(19)
(11)EP 3 020 083 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
29.04.2020 Bulletin 2020/18

(21)Application number: 14742639.9

(22)Date of filing:  26.06.2014
(51)International Patent Classification (IPC): 
H01M 4/1391(2010.01)
H01M 4/36(2006.01)
H01M 4/505(2010.01)
H01M 4/58(2010.01)
H01M 4/136(2010.01)
H01M 4/1397(2010.01)
H01M 4/485(2010.01)
H01M 4/525(2010.01)
H01M 4/131(2010.01)
H01M 10/0525(2010.01)
(86)International application number:
PCT/US2014/044240
(87)International publication number:
WO 2015/006058 (15.01.2015 Gazette  2015/02)

(54)

MIXED POSITIVE ACTIVE MATERIAL COMPRISING LITHIUM METAL OXIDE AND LITHIUM METAL PHOSPHATE

GEMISCHTES POSITIV-AKTIV-MATERIAL MIT LITHIUMMETALLOXID UND LITHIUMMETALLPHOSPHAT

MATÉRIAU ACTIF POSITIF MÉLANGÉ COMPRENANT UN OXYDE MÉTALLIQUE DE LITHIUM ET UN PHOSPHATE MÉTALLIQUE DE LITHIUM


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 09.07.2013 US 201361844122 P

(43)Date of publication of application:
18.05.2016 Bulletin 2016/20

(73)Proprietor: Dow Global Technologies LLC
Midland, MI 48674 (US)

(72)Inventors:
  • THEIVANAYAGAM, Murali, G.
    Midland, MI 48640 (US)
  • HU, Ing-Feng
    Midland, MI 48640-2176 (US)
  • MAEDA, Hideaki
    Midland, MI 48640 (US)
  • LIN, Jui-Ching
    Midland, MI 48642 (US)

(74)Representative: Beck Greener LLP 
Fulwood House 12 Fulwood Place
London WC1V 6HR
London WC1V 6HR (GB)


(56)References cited: : 
EP-A1- 2 357 693
EP-A2- 2 492 996
JP-A- H11 213 989
US-A1- 2010 154 206
EP-A1- 2 575 201
EP-A2- 2 498 323
JP-A- 2004 063 422
  
  • Dennis R Dinger: "Mixing Using an Extruder", Ceramic Processing E-zine Volume 2 Number 10, 1 August 2004 (2004-08-01), XP055404215, Retrieved from the Internet: URL:http://www.dingerceramics.com/CeramicP rocessingE-zine/CPEBackIssues/Vol2Num10.ht m [retrieved on 2017-09-06]
  
Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


Description

Field of the Invention



[0001] The invention relates to a method making improved lithium ion batteries (LIBs) and cathodes to a make LIBs. In particular, the invention relates to lithium ion batteries comprised of lithium metal oxide cathode materials where improved battery characteristics may be achieved such as greater cycle life, safety and rate capability.

Background of the Invention



[0002] Lithium ion batteries have over the past couple of decades been used in portable electronic equipment and more recently in hybrid or electric vehicles. Initially, lithium ion batteries first employed lithium cobalt oxide cathodes. Due to expense, toxicological issues and limited energy capacity other cathode materials have or are being developed.

[0003] One class of materials that has been developed and has been commercially employed is lithium metal oxides comprised of two or more of nickel, manganese and cobalt. These materials generally display a layered structure with a singular rhombohedral phase in which initial high specific charge capacities (∼170 mAh/g) have been achieved when charged to voltages of about 4.2 volts vs Li/Li+. Unfortunately, these materials have suffered from a short cycle life and safety issues related to oxygen evolution under certain conditions resulting in fires.

[0004] Li/Li+ represents the redox potential of the lithium reference electrode, which is defined as 0 volts by convention. Consequently, when using an anode other than Li metal, these voltages would be decreased to account for the difference in potential between this other anode and Li metal. Illustratively, a fully charged graphite anode has a potential of about 0.1 V vs Li/Li+. Therefore, when charging the cathode in a battery with a graphite anode to 4.25 V vs Li/Li+, the cell voltage will be approximately 4.15 V.

[0005] The cycle life is generally taken as the number of cycles (charge-discharge) before reaching a specific capacity that is 80% of the initial specific capacity. Each cycle for these materials is typically between the aforementioned 4.2 volts to 2 volts. These batteries have also suffered from inconsistencies in performance from one battery or cell to another, even though made from the same materials.

[0006] To solve some of the problems, the art has described numerous coatings, dopants as well as blending of other more stable cathode materials such as lithium iron phosphate. Examples include those described in U.S. Pat. Publ. Nos. 2004/0005265; 2004/0096743; 2006/0194112; and 2009/0305132; WO patent appl. Nos. 2008/088180; 2008/091074; 2009/057834; and 2013/016426 and Japanese Pat. No. 9035715A1. Unfortunately, even though these may have improved the safety of LIBs containing the cathode materials comprised of lithium metal oxides containing nickel, manganese, cobalt or combination thereof, the cycle life, battery capacity, or capacity at high rates of discharge were not improved. EP2357693 A1 discloses a method of forming a cathode using a mixture of lithium manganese iron phosphate and a lithium nickel manganese cobalt composite oxide.

[0007] Accordingly, it would be desirable to provide a method for forming LIBs having cathodes comprised of lithium metal oxides of nickel, manganese, cobalt or combinations thereof that results in more consistent performance, improved cycle life and greater energy capacity retention at faster charge/discharge rates while also improving the safety of such LIBs.

Summary of the Invention



[0008] We have discovered an improved method to form LIBs comprised of lithium metal oxide cathodes having nickel, manganese, cobalt or combination thereof. A first aspect of the invention is a method of forming a cathode according to claim 1.

[0009] The method surprisingly has been found to allow a LIB to be formed that has improved cycle life, essentially the same volumetric energy capacity at low and high rates of discharge and increased safety compared to a LIB having a cathode without the lithium metal phosphate. This is so even though the true density of the metal phosphate is lower than the true density of the lithium metal oxide.

[0010] The maintaining of the integrity of the secondary particles of the lithium metal phosphate is believed to be essential to achieve these surprising results. It is not understood why this is so, but is believed to be due to multiple factors such as not disrupting any electronic conductive coating that may be on the lithium metal phosphate, distribution of the lithium metal oxide and lithium metal phosphate and compaction behavior of the mixture, for example, when roll pressing to form the cathode (calendaring).

[0011] A second aspect of the invention is a cathode according to claim 6.

[0012] The cathode of the second aspect when used in a LIB surprisingly gives improved press density, volumetric energy capacity at various discharge rates, improved safety, greater cycle life than cathodes made solely with the lithium metal oxide or lithium metal phosphate. That is, there appears to be a synergistic effect, when such a ratio of secondary particle sizes of the lithium metal oxide and lithium metal phosphate is realized.

[0013] Regarding the cathode composition, it has been surprisingly found that even though the metal of lithium metal phosphate is primarily Mn, a LIB with such a cathode may have all the advantages of those previously mentioned. This is so even though it has been postulated that Mn is supposedly unstable due to dissolution in electrolytes used in LIBs (see, for example, WO 2013/016426).

[0014] A third aspect of the invention is a LIB according to claim 13.

[0015] The cathode, methods to make the cathode and LIBs made from the cathodes may be useful in any application requiring an electrochemical power source. Examples include transportation (e.g., electric and hybrid vehicles), electronics, power grid load leveling applications and the like.

Brief Description of the Drawings



[0016] 

Fig. 1 is a scanning electron micrograph at two differing magnifications of a lithium metal oxide used to make the cathode of the invention.

Fig. 2 is a scanning electron micrograph at two differing magnifications of a representative lithium metal phosphate used to make the cathode of the invention.

Fig. 3 is a scanning electron micrograph at two differing magnifications of a lithium metal phosphate not applicable to making the cathode of the invention.

Fig. 4 is a scanning electron micrograph at two differing magnifications of a lithium metal phosphate not applicable to making the cathode of the invention.

Fig. 5 is a scanning electron micrograph at differing magnifications of a cross-section of a cathode of this invention, in which the cathode has not been pressed.

Fig. 6 is a scanning electron micrograph at differing magnifications looking down at the top of a cathode of this invention, in which the cathode has been pressed.

Fig. 7 is a graph of the cycle life of an example of a LIB battery of the present invention compared to LIBs not of this invention.


Detailed Description of the Invention



[0017] The method of the first aspect of the invention uses a lithium metal oxide that is blended with a lithium metal phosphate in a particular way. Examples of lithium metal oxides include those described U.S. Pat. Nos. 5858324; 6368749; 6964828; and EP Pat. Nos. 0782206; 1296391; 0813256; 1295851; 0849817; 0872450; and 0918041 and JP Pat. No. 11-307094. Preferred metal oxides include those that have a layered structure of the Rm3 type also referred to as 03 structures that display a singular phase.

[0018] Preferred lithium metal oxides are those that are described by U.S. Pat. No. 6964828. Desirable lithium metal oxides also include those having the following formula.

        LiaCobMnc(M)dNi1-(b+c+d)O2

where (M) denotes a metal other than Co, Mn or Ni and a is greater than 0 to 1.2; b is 0.1 to 0.5, c is 0.05 to 0.4 and d is 0 to 0.4 and b+c+d is 0.15 to 0.5. M is preferably B, Al, Si, Fe, V, Cr Cu, Zn, Ga and W. Preferably "a" is less than 1.1 and more preferably less than 1.05. It is understood that LIBs made from such cathode materials are assembled in the discharged state (i.e., lithium is present in the lithium metal oxide "a ∼ 1" and then is extracted and inserted into the anode upon charging the LIB for the first time). It is also understood that more than one lithium metal oxide may be used wherein the lithium metal oxide may differ in chemistry, primary particle size or the like. In any case, the lithium metal oxide of the cathode of the invention is a lithium metal oxide of nickel, manganese, cobalt, or combinations thereof.

[0019] The lithium metal oxide generally has a median (D50) primary particle size of 0.1 micrometer to 5 micrometers. Primary particle means the smallest distinct division of a given phase as is readily determined by microscopy and is analogous, for example, to a grain in a fully dense multigrain ceramic. The D50 primary particle size is desirably at least 0.2, 0.4 or 0.5 to 4, 3, or 2 micrometers. The particle size distribution is given by D10 and D90 particles sizes. D10 is the size where 10% of the particles are smaller and D90 is the particle size where 90% of the particles are smaller in a given distribution by number. The D10 typically is 0.1, 0.2, or 0.3 micrometer. The D90 is typically 8, 5, or 4 micrometers.

[0020] The lithium metal oxide has a median (D50) secondary particle size by number that is useful to achieve a suitable pour density and tap density to achieve suitable densities on a metal foil when making the cathode of this invention. Secondary particle size means a cluster of primary particles bonded together either by hard or soft bonding where hard bonding is by chemical bonds such as covalent or ionic bonding and soft bonding is by hydrogen, van der Waals or mechanical interlocking. The primary particles making up the lithium metal oxide typically are bonded at least in part by hard bonding. The D50 secondary particle size by number is 2 to 30 micrometers. Desirably, the secondary particle size D50 is 3, 4, or 5 to 25, 20 or 15 micrometers. The lithium metal oxide secondary particles typically have a D10 that is 3, 4, or 5 micrometer and a D90 that is 12, 16, or 20 micrometers.

[0021] As stated above, the lithium metal oxide is mixed with a lithium metal phosphate in a solvent. Known lithium metal phosphates include, for example, those described in U.S. Pat. Nos. 5910382; 6514640; 5871866; 6632566; 7217474; 6528033; 6716372; 6749967, 6746799; 6811924; 6814764; 7029795; 7087346; 6855273; 7601318; 7338734; and 2010/0327223. The lithium metal phosphate is one in which a majority of the metal is Mn, which has a higher redox potential, for example, than iron in lithium iron phosphate. The higher redox potential of the Mn has been found to be useful in realizing a LIB with smooth or uniform discharge curves when mixed with the lithium metal oxides.

[0022] It has been discovered that the lithium metal phosphate secondary particulates need to have a median (D50) primary particle size by number of 25 nanometers to 1000 nanometers and D50 secondary particle size by number of 2 to 30 micrometers. It is desirable for the lithium metal phosphate primary particles to be to at most 750, 500, 250, 100, or even 75 nanometers. It also has been discovered that it is critical that the lithium metal phosphate should be present as a secondary particle when being mixed with the lithium metal oxide and its median size (D50) should be within an order of magnitude of the lithium metal oxide median secondary particle size by number. The D50 secondary particle size by number is 2 to 30 micrometers. Desirably, the D50 secondary particle size is 3, 4, or 5 to 25, 20 or 15 micrometers. The lithium metal phosphate secondary particles typically have a D10 by number that is 3, 5, or 8 micrometers and a D90 that is 15, 25, or 35 micrometers.

[0023] Typically, the secondary particles of the lithium metal phosphate tend to only be softly bonded. Thus, it is essential that the mixing not be so vigorous such that these secondary particles break apart to an extent such that the performance of the LIB is deleteriously affected. The amount of breakage may be determined by microscopic techniques prior to and after mixing the lithium metal phosphate whereby the size and size distribution may be determined and compared. According to the invention, after mixing the average secondary particle size should be within 10% of the median secondary particle size prior to mixing, and most preferably within 5% or statistically, insignificantly different.

[0024] The secondary particles of the lithium metal phosphate may be formed in situ, for example, when the lithium metal phosphate is made by a precipitation process, but more desirably, they are made from an agglomeration process such as by spray drying. It is desirable for the secondary particles to have an average projection sphericity or roundness (called sphericity in further discussion for simplicity) of 0.6 to 1.0. The average projection sphericity is at least 0.4, 0.6 or 0.7 to at most 1. The sphericity is measured by Pentland method (4A)/(πL2), where A and L are the area and long diameter (maximum caliper) of the projection of particle, respectively, as described by The Image Processing Handbook, Sixth Ed., J.C. Russ, CRC Press, 2011 (Chapt. 11). Likewise, it has been discovered that the sphericity of the lithium metal oxide is also desirably as those just mentioned. In a preferred embodiment, the ratio of the sphericity (average) of the secondary particles of the lithium metal oxide/lithium metal phosphate is desirably 0.3 to 3.33 and more desirably 0.5 to 2, even more desirably 0.6 to 1.7 and most desirably 0.8 to 1.

[0025] The lithium metal phosphate depending on the particular metals may advantageously have an electronic coating thereon. The coating generally is present in an amount of 0.5% by weight to 20% by weight of the lithium metal phosphate and said coating. It is desirable to have as little coating as possible and as such the amount is desirably at most 10%, 8%, 5% or even 3%. Typically, the coating is carbonaceous and may include graphitic carbon, amorphous carbon or combinations thereof. A desirable carbon coating may be one resulting from the carburization of an organic compound such as those known in the art, with examples being phenol, formaldehydes, sugars (e.g., lactose, glucose and fructose), starches, and celluloses.

[0026] It has been discovered that it is further advantageous for the lithium metal oxide and lithium metal phosphate to have average secondary particle sizes that are substantially near each other so that one does not form a coating and allows, for example, the deformation of the lithium metal phosphate upon pressing to form a cathode (layer of the mixture pressed on to a metal foil). It is not understood why this is important, but may be as stated previously or that it is important to have a reservoir of lithium metal phosphate that is not substantially interacting with the lithium metal oxide (combination of interacting and non-interacting). Thus, it is desirable for the lithium metal oxide and lithium metal phosphate to have a ratio of median (D50) secondary particle size that is from 0.9 to 1.1.

[0027] When mixing the lithium metal oxide and lithium metal phosphate, the amount of each generally may be any useful amount. Typically, however, the mixture typically has at least 5% to 65% by weight of the lithium metal phosphate. Note, if an electronic coating is present on either the oxide or phosphate, it is included in the aforementioned weight percentages. Desirably, the amount of the lithium metal phosphate is at most 50%, 49%, 40%, 30%, or even 20% to at least 10%.

[0028] According to the invention, the lithium metal phosphate is one that has an empirical formula: LiaMnbFecDdPO4, wherein a is a number from 0.85 to 1.15;
b is from 0.65 to 0.95;
c is from 0.049 to 0.349;
d is from 0.001 to 0.1;
2.75 ≤ (a + 2b + 2c + dV) ≤ 3.10, wherein V is the valence of D, and D is a metal ion selected from one or more of magnesium, calcium, strontium, cobalt, titanium, zirconium, molybdenum, vanadium, niobium, nickel, scandium, chromium, copper, zinc, beryllium, lanthanum and aluminum, and further wherein at least a portion of the lithium metal phosphate has an olivine structure. It is further preferred that D is magnesium, cobalt or combination thereof. This particular phosphate material has been found to not only improve cycle life even though it has high Mn concentration, but also not deleteriously affect the voltage discharge profiles of the battery as do high iron containing lithium metal phosphates.

[0029] The lithium metal oxide and lithium metal phosphate are mixed in a solvent so as to allow for a uniform mixture to be formed and to decrease the possibility of breaking the secondary particles of the lithium metal phosphate. The solvent may be any suitable solvent such as those known in the art and typically are polar and apolar organic solvents with low water contents (e.g., 500 ppm or less and preferably less than 100, 50, 10 or even 1 ppm). Examples of useful solvents include organic solvents such as n-methyl pyrrolidone (NMP) and acetone and polar solvents such as water and those described by Jin Chong, et al., Journal of Power Sources 196 (2011) pp. 7707 - 7714.

[0030] The amount of solids (lithium metal oxide and phosphate) may be any useful amount. Typically the amount is from 10% to 90% by volume of the solvent and may be at least 20% or 30% to at most 80% or 70%.

[0031] As indicated previously, it is essential that the mixing be under conditions that do not break the secondary particles of the lithium metal phosphate. Typically, this requires low shear mixing techniques such as simple paddle mixers with or without baffles. A high shear mixer (e.g. colloid mill) may be used so long as the shear forces or the gaps employed do not impinge and break the secondary particles as described above. The shear rate is at most about 5000 sec-1 and generally is about 1 sec-1 to about 1000 sec-1. Other known additives useful for casting slurries on to foils may be utilized, such as suitable dispersants, lubricants, binders and water scavengers.

[0032] The mixing is performed for a time to disperse the lithium metal oxide and lithium metal phosphate sufficiently so that the desired results are achieved. Typically the time may be from several minutes to any time that is practicable such as days or hours.

[0033] The mixture is then coated on to a metal foil that is useful for making electrodes in batteries such as aluminum, carbon coated aluminum, etched aluminum, nickel, copper, gold, silver, platinum, and alloys of the aforementioned or combinations thereof and include those described in Hsien-Chang Wu et. al., Journal of Power Sources 197 (2012) pp. 301 - 304.

[0034] The coating of the slurry may be done by any useful technique such as those known in the art. Typically, the method employed is a doctor blade casting at a desired gap.

[0035] The solvent is then removed to form the cathode. The removing may be any suitable method such as evaporating with or without heating under as static or flowing air or other suitable atmosphere such as dry air, inert atmosphere (nitrogen or inert gas such as a noble gas) or vacuum. If heating is employed, the temperature is any useful for the particular solvent employed and may be 30°C to 500°C, but is preferably 50 to 150°C. The time may be any suitable time such as several minutes to days or hours. The heating may be any useful heating such as resistance, convection, microwave, induction or any known heating method.

[0036] In an embodiment, after the solvent has been removed, the cathode is further subjected to pressing. This pressing in many instances is referred to calendaring in the art to further increase the density of the lithium metal oxide/lithium metal phosphate coating on the metal foil. Typically, calendaring is performed by passing the cathode through a roll press with a set gap to realize a cathode with uniform thickness. The cathode may be passed through the roll press multiple times with changing gaps or the same gap depending on the behavior of the coating. When doing the pressing, it is desirable to only distort the secondary particles of the lithium metal phosphate and not have any appreciable change such as fracturing of the lithium metal phosphate secondary particles. Generally, this corresponds to a pressure that is at most about 500 MPa and is desirably at most about 250, 180, 170 or 160 MPa to some low pressure which may be at least about 10 MPa. Likewise, the pressure should not be so great to cause any electronic conducting coating to be fractured off the lithium metal phosphate and also not so high that the density of the coating is too high, for example, the electrolyte employed in the battery has difficulty wetting the cathode sufficiently to achieve the desired results.

[0037] Typically, the coating has a % theoretical density that is 40% to 85% of theoretical density (60% to 15% porous). It is desirable for the theoretical density to be at least 45%, 50% or even 55% to 80%, 75% or even 70%.

[0038] The cathode is useful in making improved LIBs and when making such LIBs, suitable anode materials include, for example, carbonaceous materials such as natural or artificial graphite, carbonized pitch, carbon fibers, graphitized mesophase microspheres, furnace black, acetylene black, and various other graphitized materials. Suitable carbonaceous anodes and methods for making them are described, for example, in U.S. Patent No. 7,169,511. Other suitable anode materials include lithium metal, lithium alloys, other lithium compounds such as lithium titanate and metal oxides such as TiO2, SnO2 and SiO2, as well as materials such as Si, Sn, or Sb. The anode may be made using one or more suitable anode materials.

[0039] The separator of the LIB is generally a nonconductive material. It should not be reactive with or soluble in the electrolyte solution or any of the components of the electrolyte solution under operating conditions but must allow lithium ionic transport between the anode and cathode. Polymeric separators are generally suitable. Examples of suitable polymers for forming the separator include polyethylene, polypropylene, polybutene-1, poly-3-methylpentene, ethylene-propylene copolymers, polytetrafluoroethylene, polystyrene, polymethylmethacrylate, polydimethylsiloxane, polyethersulfones and the like.

[0040] Generally, the battery electrolyte solution has a lithium salt concentration of at least 0.1 moles/liter (0.1 M), preferably at least 0.5 moles/liter (0.5 M), more preferably at least 0.75 moles/liter (0.75 M), preferably up to 3 moles/liter (3.0 M), and more preferably up to 1.5 moles/liter (1.5 M). The lithium salt may be any that is suitable for battery use, including lithium salts such as LiAsF6, LiPF6, LiPF4(C2O4), LiPF2(C2O4)2, LiBF4, LiB(C2O4)2, LiBF2(C2O4), LiClO4, LiBrO4, LiIO4, LiB(C6H5)4, LiCH3SO3, LiN(SO2C2F5)2, and LiCF3SO3. The solvent in the battery electrolyte solution may be or include, for example, a cyclic alkylene carbonate like ethylene carbonate; a dialkyl carbonate such as diethyl carbonate, dimethyl carbonate or methylethyl carbonate, various alkyl ethers; various cyclic esters; various mononitriles; dinitriles such as glutaronitrile; symmetric or asymmetric sulfones, as well as derivatives thereof; various sulfolanes, various organic esters and ether esters having up to 12 carbon atoms, and the like.

EXAMPLES



[0041] Sphericity of particles was measured by Pentland method as described earlier.

[0042] The particle size was measured using a Coulter particle size analyzer (Coulter LS230, Bechman Coulter Inc., Brea, CA). Surface area of the particles was measured by multi-point Brunauer-Emmett-Teller (BET) surface area measurement based on N2 gas adsorption on sample surfaces (Micromeritics Tristar II, Micromeritics Instrument Corp., Norcross, GA). True density was determined from the X-ray crystal data. Tap density was measured using 1000 taps by TAP-2s tap density tester available from Logan Instruments Corporation, Somerset, NJ.

[0043] The Examples and Comparative Examples, when a lithium metal oxide was present, used lithium metal oxide (LMO) available from 3M, St. Paul, MN, having the chemical formula Li1.10Ni0.42Mn0.42Co0.17O2 and the properties are shown in Table 1 and a micrograph of this powder is shown in Fig. 1.

[0044] Three lithium manganese iron phosphates (LMFPs) were used. The first was made as follows and is referred to as "LMFP A". Iron oxalate dihydrate and manganese carbonate were mixed with water in an amount sufficient to render the mixture fluid enough to pour and pump. If a dopant metal was used, the dopant metal precursor(s) used were magnesium acetate and/or cobalt acetate. 85% Phosphoric acid in water by weight is slowly added to the mixture. After the acid addition is finished, the mixture is mixed for about 30 minutes more.

[0045] The mixture was milled using zirconia media until the particles were reduced to approximately 50 nm in diameter. During the milling, cellulose acetate was added to realize the carbon content as shown in Table 1.

[0046] The milled mixture was spray dried at 170°C to agglomerate the small particles into essentially spherical secondary particles having diameters of up to about 20 microns. The spray dried particles were heated under an atmosphere containing <100 ppm oxygen. The particles were heated from room temperature to 400°C over three hours and held at 400°C for one hour. The temperature was then increased to 650°C over two hours and held at 650°C for three hours. The heated particles were cooled to below 60°C and sieved through a 44 micron sieve. A micrograph of LMFP A appears in Fig. 2 and the characteristics of this LMFP A are shown in Table 1.

[0047] The second LMFP (referred to as "LMFP B") was made by milling Ketjen black (EC600JD) available from AkzoNobel Chemicals S.A., Parc Industriel de Ghlin, Belgium, lithium dihydrogen phosphate, iron oxalate dihydrate, and manganese carbonate in a CM20 Simoloyer mill available from Zoz GmbH, Wenden, Germany using stainless steel grinding media at 450 RPM for 2 to 3 hours followed by calcination at 650 to 700°C for 1 hour in Argon. The characteristics of LMFP B are shown in Table 1 and a micrograph of this LMFP appears in Fig. 3. In Fig. 3, the majority of the particles are dispersed as primary particles with the remaining particles being loosely agglomerated in secondary particles. Since there is in essence a lack of secondary particles, this LMFP's secondary particulate sphericity was not measured (i.e., not applicable).

[0048] The third LMFP referred to as "LMFP C" is the same as LMFP A except that after being formed, the LMFP A was milled in a PM 400 planetary mill (Retsch GmbH, Haan, Germany) run at 200 rpm for 20 minutes in using 5 mm diameter yttrium stabilized zirconia media. The powder to media ratio was (1/10). The characteristics of LMFP C are shown in Table 1 and a micrograph of this LMFP appears in Fig. 4. From Figs. 2 to 4, it is evident that LMFP B and C are essentially comprised of separated primary particles.

Examples 1 to 6:



[0049] In these Examples, LMFP A was blended with the LMO described above in the weight ratios given in Table 2.

[0050] LMFP A was blended with the LMO as follows. 3.5 (pbw)of binder (Solef 5130 from Solvay, which was added as a 5% by weight solution of N-Methylpyrrolidone (NMP)) and 2.5 (pbw) conductive carbon (SuperP conductive carbon from TIMCAL graphite and carbon) was mixed for 5 minutes at 2000 RPM in a mixer (FlackTek, Inc. Speedmixer (DAC150, FV2-k)). LMFP A was mixed with binder/carbon mixture with an amount of NMP to realize a 55% to 60% total solids loading for an additional 5 minutes of the final mixture. LMO was then added to realize the ratio of LMFP to LMO ratio as shown in Table 2 and mixed for 10 minutes at 2500 RPM, which is the same rpm used throughout.

[0051] The slurry was coated using a doctor blade onto an aluminum foil (15 microns thick) available from MTI Corporation. After coating, the NMP was removed by drying at 130°C in air for 15 minutes to form the cathode. The thickness of the coating was about 70 to 80 micrometers. Fig. 5 is a scanning electron micrograph of a cross-section of the coating after drying of Example 1. Generally, for each of the Examples, the sphericity of the secondary particles of the LMO and LMFP A were essentially the same as that of the starting LMO and LMFP.

[0052] The cathode was then further pressed using a roll press to a density of about 3 g/cc active material. Density of active material means the density of the LMFP and NMC as calculated from the measured volume and weight. The pressed cathode was punched to form circular cathodes of 1.6 cm2 area and further dried under vacuum at 125°C for at least 8 hours. Fig. 6 is a scanning electron micrograph looking down at the top of the Example 1 mixture after it was pressed. The sphericity of the LMFP was not determined due to extensive distortion, but the LMO again had essentially the same sphericity as the powder, which is also the case for each of the Comparative Examples after pressing.

[0053] From Figs. 1, 2, and 5, it is evident that the shear rate of the mixing used to make the mixture of LMFP A and LMO was insufficient to break apart secondary particles of either of these. Likewise, from Fig. 6, it is evident that the roll pressing (calendaring) was insufficient to break apart either the LMO or LMFP A, but was sufficient to distort the LMFP secondary particles, which is believed to enhance the density of the coating on the aluminum foil making up the cathode.

[0054] The pressed and punched cathodes were incorporated into CR2025 coin cells. The cells were charged using a constant current (1/10 C-rate) to 4.25V, and then held at constant voltage of 4.25 until the current decayed to C/100. The discharge was done at constant current (varying with different C-rates) with a voltage cutoff of 3.0 V. The anode in each case is lithium (in the case of a half cell) and a commercially available graphite, (AGP-2 powder obtained from BTR New Energy Materials Inc., Shenzhen, China), (in the case of a full cell), the anode/cathode capacity ratio is 1.1 to 1.2 for the full cells. A commercially available separator is used with an electrolyte of a 1.15 molar LiPF6 solution in a 1:3 by weight mixture of ethylene carbonate and ethylmethylcarbonate that also contains 2% by weight vinylidene carbonate. Cycle life was evaluated at 50°C in coin cells against graphite anode. The electrolyte used in the coin cells was 1 M LiPF6 in EC/EMC (1:3) with 2% VC.

[0055] The thermal behavior (DSC) of charged cathodes were measured by charging the cathode to 4.25 V in coin half cell against lithium metal, then disassembling the cells in dry room, and sealing them in hermetically tight DSC pans with the residual electrolyte left in the cathode. The DSC pans are then heated at a heating rate of 10°C/min and the observed heat is plotted vs. temperature, with the results for selected Examples and Comparative Examples shown in Table 3.

[0056] Oxygen evolution of charged cathodes were measured by charging the cathode to 4.25 V in coin half cell against lithium metal, then disassembling the cells in an Argon filled glove box. The electrodes were washed with dimethyl carbonate solvent to remove the electrolyte and dried under vacuum at 25°C for 12 hours. The dried electrodes were heated under Argon at 10°C/minute in a mass spectroscopy with evolved gas analysis (oxygen) for selected examples and comparative examples shown in Table 3.

Comparative Example 1:



[0057] Cathodes and cells were made in the same manner as for Examples 1 to 6 described above except that the cathodes were made using the LMO only. The density of the coating on the cathode after pressing and the characteristics of the cells are shown in Table 2.

Comparative Example 2:



[0058] Cathodes and cells were made in the same manner as for Examples 1 to 6 described above except that the cathodes were made using LMFP A only. The density of the coating on the cathode after pressing and the characteristics of the cells are shown in Table 2.

Comparative Examples 3 to 5:



[0059] Cathodes and cells were made in the same manner as for Examples 1 to 6 described above except that the cathodes were made using LMFP B blended with the LMO in the ratios shown in Table 2. The density of the coating on the cathode after pressing and the characteristics of the cells are also shown in Table 2.

Comparative Examples 6 to 8:



[0060] Cathodes and cells were made in the same manner as for Examples 1 to 6 described above except that the cathodes were made using LMFP C blended with the LMO in the ratios shown in Table 2. The density of the coating on the cathode after pressing and the characteristics of the cells are also shown in Table 2.

[0061] From Table 2, Examples 1 and 2 have essentially the same battery performance of Comparative Example 1. This is so even though the true density of the LMFP A is substantially lower than the true density of the LMO. It is believed this effect is due to an unexpected improved packing of particles without compromising conductivity when it comes to performance at high discharge rates. This surprising battery performance, however, is not observed when the LMFP fails to retain the secondary particle cohesiveness as displayed by the battery performance of Comparative Examples 3 to 8. Likewise, Comparative Example 2 shows that LMFP A does not display similar performance and as such the improvement in battery performance of the Examples 1 to 3 is not as a result of a mere rule of mixture. Examples 4-6 show that the performance improvement continues even at high concentrations of LMFP. For example, the discharge capacity at 10C of Examples 4-6 is greater than each of Comparative Examples 3-8.

[0062] The cycle life of Example 2, and Comparative Examples 1, 4 and 7 is shown in Fig. 7 measured in a coin cell. From this Figure, it is evident the cycle life of a battery is substantially improved when using the process to make a coated cathode that has a blended LMO/LMFP mixture wherein the LMFP retains cohesiveness of the LMFP secondary particles and the LMO secondary particles retain their shapes.

[0063] Table 3 compares the DSC analysis of Examples 1, 2, and comparative example 1. The bare NMC cathode (comparative example 1) shows two characteristic heat evolution peaks, one at 244°C and the second peak at 314°C. The addition of LMFP to NMC shifts both the exothermic peaks to higher temperatures, which is beneficial. Also, the shift in temperature is proportional to the amount of LMFP added in the blend.

[0064] Inhibiting or lowering the oxygen evolution from a charged cathode is important to improve the safety of NMC cathodes. Table 3 compares the oxygen evolution from bare NMC (Comparative Example 1) and NMC blended with LMFP (Examples 1 and 2). Charged NMC cathode releases oxygen with the peak onset temperature around 265°C. Addition of LMFP cathode to NMC delays, shifts the oxygen evolution to higher temperature, and also decreases the amount of oxygen evolved.
Table 1
CharacteristicLMOLMFP ALMFP BLMFP C
Chemistry Li1.10Ni-0.42Mn0.42Co0.17O2 Li1.05Mn0.75Fe0.15Mg0.05Co0.005PO4 Li1.025Mn0.30Fe0.20PO 4 Li2.05Mn0.75Fe0.15Mg0.05Co0.003PO4
Surface Area (m2/g) 0.31 m2/g 24 35 28
D10 (µm) 4 3.8 2.9 1
D50 (µm) 8 8.2 11.3 6
D90 (µm) 13 13 46.5 27
Tap density (g/cc) 2.2 1.1 - 0.9 0.7 1.1
Sphericity of Secondary Particles 0.68 0.78 Not applicable Not applicable
True density (g/cc) 4.6 3.45 3.45 3.45
Carbon (wt%) Not applicable 3 8 3


Table 3
SampleLMO/LMFP Wt. ratioDSC Peak 1 Temperature (°C)DSC Peak 2 Temperature (°C)DSC Total Heat (J/g of cathode)Oxygen Evolution Onset Temperature (°C)Evolved Oxygen (%)
Comparative example 1 100/0 244 316 587 262 100%
Example 1 90/10 261 320 717 282 66%
Example 2 80/20 262 323 687 310 35%
Example 3 60/40 260 327 569 315 18%



Claims

1. A method of forming a cathode comprising:

(a) mixing a lithium metal oxide and lithium metal phosphate in a solvent, wherein (i) the lithium metal phosphate has a D50 secondary particle size by number of 2 micrometers to 30 micrometers and a D50 primary particle size by number that is 25 to 1000 nanometers, and the average sphericity of the lithium metal phosphate is from 0.4 to 1.0, wherein said sphericity is measured by Pentland method (ii) the lithium metal oxide has a secondary particle size having a D50 by number of 2 to 30 micrometers and, (iii) the mixing is performed at a shear rate of at most 5000 sec-1 such that the lithium metal phosphate secondary particles after mixing have a D50 that is within 10% of the D50 secondary particle size prior to mixing;

(b) coating the mixture of step (A) on to a metal foil; and

(c) removing the solvent to form the cathode; wherein the lithium metal phosphate has the formula

        LiaMnbFecDdPO4,

wherein

a is a number from 0.85 to 1.15;

b is from 0.65 to 0.95;

c is from 0.049 to 0.349;

d is from 0.001 to 0.1;
2.75 ≤ (a + 2b + 2c + dV) ≤ 3.10, wherein V is the valence of D, and D is a metal ion selected from one or more of magnesium, calcium, strontium, cobalt, titanium, zirconium, molybdenum, vanadium, niobium, nickel, scandium, chromium, copper, zinc, beryllium, lanthanum and aluminum, and further wherein at least a portion of the lithium metal phosphate has an olivine structure;

wherein the lithium metal oxide is a lithium metal oxide of nickel, manganese, cobalt, or combinations thereof.


 
2. The method of Claim 1, further comprising pressing the cathode after removing the solvent.
 
3. The method of Claim 2, wherein the pressing is performed at a pressure from 10 MPa to 250 MPa.
 
4. The method of Claim 3, wherein the average sphericity of the lithium metal oxide is from 0.4 to 1.0, and optionally wherein the average sphericity of the lithium metal oxide to the average sphericity of the lithium metal phosphate has a ratio that is 0.4 to 2.5.
 
5. The method of Claim 1, wherein the lithium metal oxide has a D50 primary particle size of 3 micrometers to 0.1 micrometers and/or the D50 secondary particle size of the lithium metal oxide to the D50 secondary particle size of the lithium metal phosphate has a ratio that is 0.5 to 1.5.
 
6. A cathode, obtainable by the method of claim 1, comprised of a metal foil having a first and second face and cathode material coated on at least one face of the foil, the cathode material being comprised of a mixture of a lithium metal oxide and a lithium metal phosphate wherein the amount of lithium metal phosphate is 5% to 65% by weight of the mixture, wherein the lithium metal oxide is comprised of primary and secondary particles and the lithium metal phosphate is comprised of primary and secondary particles and the lithium metal oxide secondary particles have a D50 by number and lithium metal phosphate secondary particles have a D50 by number such that the D50 secondary particle size of the lithium metal oxide and lithium metal phosphate has a ratio of between 0.9 to 1.1; and
wherein the lithium metal phosphate has the formula

        LiaMnbFecDdPO4,

wherein

a is a number from 0.85 to 1.15;

b is from 0.65 to 0.95;

c is from 0.049 to 0.349;

d is from 0.001 to 0.1;

2.75 ≤ (a + 2b + 2c + dV) ≤ 3.10, wherein V is the valence of D, and D is a metal ion selected from one or more of magnesium, calcium, strontium, cobalt, titanium, zirconium, molybdenum, vanadium, niobium, nickel, scandium, chromium, copper, zinc, beryllium, lanthanum and aluminum, and further wherein at least a portion of the lithium metal phosphate has an olivine structure; and
wherein the lithium metal oxide is a lithium metal oxide of nickel, manganese, cobalt, or combinations thereof.
 
7. The cathode of Claim 6, wherein the lithium metal phosphate has an electronic conductive coating.
 
8. The cathode of Claim 7, wherein lithium metal oxide has an electronic conductive coating that is graphite, amorphous carbon or combination thereof.
 
9. The cathode of Claim 6, wherein the average sphericity of the lithium metal oxide is from 0.4 to 1.0 and the average sphericity of the lithium metal phosphate is from 0.4 to 1.0 and optionally wherein the average sphericity of the lithium metal oxide to the average sphericity of the lithium metal phosphate has a ratio 0.4 to 2.5.
 
10. The cathode of Claim 6 wherein the amount of lithium metal phosphate is 5% to 49% by weight of the mixture
 
11. The cathode of any of Claims 6 to 10, wherein D is magnesium, cobalt or a mixture of magnesium and cobalt.
 
12. The cathode of any of Claims 6 to 11, wherein (a + 2b + 2c + dV) ≠ 3.00.
 
13. A lithium ion battery comprising the cathode of any one of the preceding Claims.
 


Ansprüche

1. Ein Verfahren zum Bilden einer Kathode, beinhaltend:

(a) Mischen eines Lithium-Metall-Oxids und Lithium-Metall-Phosphats in einem Lösemittel, wobei (i) das Lithium-Metall-Phosphat eine sekundäre D50-Teilchengröße nach Anzahl von 2 Mikrometer bis 30 Mikrometer und eine primäre D50-Teilchengröße nach Anzahl, die 25 bis 1000 Nanometer beträgt, aufweist und die durchschnittliche Kugelförmigkeit des Lithium-Metall-Phosphats von 0,4 bis 1,0 beträgt, wobei die Kugelförmigkeit durch das Pentland-Verfahren gemessen wird, (ii) das Lithium-Metall-Oxid eine sekundäre Teilchengröße mit einer D50 nach Anzahl von 2 bis 30 Mikrometer aufweist und (iii) das Mischen bei einer Scherrate von höchstens 5000 Sek-1 durchgeführt wird, sodass die sekundären Teilchen des Lithium-Metall-Phosphats nach dem Mischen eine D50 aufweisen, die innerhalb von 10 % der sekundären D50-Teilchengröße vor dem Mischen liegt;

(b) Beschichten einer Metallfolie mit der Mischung aus Schritt (A); und

(c) Entfernen des Lösemittels, um die Kathode zu bilden;
wobei das Lithium-Metall-Phosphat die Formel LiaMnbFecDdPO4 aufweist, wobei a eine Zahl von 0,85 bis 1,15 ist;
b von 0,65 bis 0,95 beträgt;
c von 0,049 bis 0,349 beträgt;
d von 0,001 bis 0,1 beträgt;
2,75 ≤ (a + 2b + 2c + dV) ≤ 3,10, wobei V die Valenz von D ist und D ein Metallion ist, ausgewählt aus einem oder mehreren von Magnesium, Calcium, Strontium, Cobalt, Titan, Zirkonium, Molybdän, Vanadium, Niob, Nickel, Scandium, Chrom, Kupfer, Zink, Beryllium, Lanthan und Aluminium, und wobei ferner mindestens ein Teil des Lithium-Metall-Phosphats eine Olivinstruktur aufweist;
wobei das Lithium-Metall-Oxid ein Lithium-Metall-Oxid von Nickel, Mangan, Cobalt oder Kombinationen davon ist.


 
2. Verfahren gemäß Anspruch 1, ferner beinhaltend das Pressen der Kathode nach dem Entfernen des Lösemittels.
 
3. Verfahren gemäß Anspruch 2, wobei das Pressen bei einem Druck von 10 MPa bis 250 MPa durchgeführt wird.
 
4. Verfahren gemäß Anspruch 3, wobei die durchschnittliche Kugelförmigkeit des Lithium-Metall-Oxids von 0,4 bis 1,0 beträgt und wobei gegebenenfalls die durchschnittliche Kugelförmigkeit des Lithium-Metall-Oxids ein Verhältnis zur durchschnittlichen Kugelförmigkeit des Lithium-Metall-Phosphats aufweist, das 0,4 bis 2,5 beträgt.
 
5. Verfahren gemäß Anspruch 1, wobei das Lithium-Metall-Oxid eine primäre D50-Teilchengröße von 3 Mikrometer bis 0,1 Mikrometer aufweist und/oder die sekundäre D50-Teilchengröße des Lithium-Metall-Oxids ein Verhältnis zur sekundären D50-Teilchengröße des Lithium-Metall-Phosphats aufweist, das 0,5 bis 1,5 beträgt.
 
6. Eine Kathode, erhältlich durch das Verfahren gemäß Anspruch 1, die aus einer Metallfolie besteht, die eine erste und eine zweite Fläche und Kathodenmaterial, mit dem mindestens eine Fläche der Folie beschichtet ist, aufweist, wobei das Kathodenmaterial aus einer Mischung aus einem Lithium-Metall-Oxid und einem Lithium-Metall-Phosphat besteht, wobei die Menge des Lithium-Metall-Phosphats von 5 Gewichts-% bis 65 Gewichts-% der Mischung beträgt, wobei das Lithium-Metall-Oxid aus primären und sekundären Teilchen besteht und das Lithium-Metall-Phosphat aus primären und sekundären Teilchen besteht und die sekundären Teilchen des Lithium-Metall-Oxids eine D50 nach Anzahl aufweisen und die sekundären Teilchen des Lithium-Metall-Phosphats eine D50 nach Anzahl aufweisen, sodass die sekundäre D50-Teilchengröße des Lithium-Metall-Oxids und Lithium-Metall-Phosphats ein Verhältnis von zwischen 0,9 bis 1,1 aufweist; und
wobei das Lithium-Metall-Phosphat die Formel LiaMnbFecDdPO4 aufweist, wobei a eine Zahl von 0,85 bis 1,15 ist;
b von 0,65 bis 0,95 beträgt;
c von 0,049 bis 0,349 beträgt;
d von 0,001 bis 0,1 beträgt;
2,75 ≤ (a + 2b + 2c + dV) ≤ 3,10, wobei V die Valenz von D ist und D ein Metallion ist, ausgewählt aus einem oder mehreren von Magnesium, Calcium, Strontium, Cobalt, Titan, Zirkonium, Molybdän, Vanadium, Niob, Nickel, Scandium, Chrom, Kupfer, Zink, Beryllium, Lanthan und Aluminium, und wobei ferner mindestens ein Teil des Lithium-Metall-Phosphats eine Olivinstruktur aufweist; und
wobei das Lithium-Metall-Oxid ein Lithium-Metall-Oxid von Nickel, Mangan, Cobalt oder Kombinationen davon ist.
 
7. Kathode gemäß Anspruch 6, wobei das Lithium-Metall-Phosphat eine elektronisch leitfähige Beschichtung aufweist.
 
8. Kathode gemäß Anspruch 7, wobei das Lithium-Metall-Oxid eine elektronisch leitfähige Beschichtung aufweist, die Graphit, amorpher Kohlenstoff oder eine Kombination davon ist.
 
9. Kathode gemäß Anspruch 6, wobei die durchschnittliche Kugelförmigkeit des Lithium-Metall-Oxids von 0,4 bis 1,0 beträgt und die durchschnittliche Kugelförmigkeit des Lithium-Metall-Phosphats von 0,4 bis 1,0 beträgt und wobei gegebenenfalls die durchschnittliche Kugelförmigkeit des Lithium-Metall-Oxids ein Verhältnis von 0,4 bis 2,5 zur durchschnittlichen Kugelförmigkeit des Lithium-Metall-Phosphats aufweist.
 
10. Kathode gemäß Anspruch 6, wobei die Menge des Lithium-Metall-Phosphats 5 Gewichts-% bis 49 Gewichts-% der Mischung beträgt.
 
11. Kathode gemäß einem der Ansprüche 6 bis 10, wobei D Magnesium, Cobalt oder eine Mischung aus Magnesium und Cobalt ist.
 
12. Kathode gemäß einem der Ansprüche 6 bis 11, wobei (a + 2b + 2c + dV) ≠ 3,00.
 
13. Eine Lithiumionenbatterie, beinhaltend die Kathode gemäß einem der vorhergehenden Ansprüche.
 


Revendications

1. Une méthode de formation d'une cathode comprenant :

(a) le mélange d'un oxyde métallique de lithium et d'un phosphate métallique de lithium dans un solvant, dans laquelle (i) le phosphate métallique de lithium a une taille de particule secondaire D50 en nombre de 2 micromètres à 30 micromètres et une taille de particule primaire D50 en nombre qui va de 25 à 1 000 nanomètres, et la sphéricité moyenne du phosphate métallique de lithium va de 0,4 à 1,0, dans laquelle ladite sphéricité est mesurée par la méthode de Pentland (ii) l'oxyde métallique de lithium a une taille de particule secondaire ayant une D50 en nombre de 2 à 30 micromètres et, (iii) le mélange est réalisé à une vitesse de cisaillement de tout au plus 5 000 sec-1 telle que les particules secondaires de phosphate métallique de lithium après le mélange ont une D50 qui est à 10 % près de la taille de particule secondaire D50 préalablement au mélange ;

(b) le revêtement du mélange de l'étape (A) sur une feuille métallique ; et

(c) le retrait du solvant afin de former la cathode ;
dans laquelle le phosphate métallique de lithium a la formule LiaMnbFecDdPO4, dans laquelle
a est un nombre allant de 0,85 à 1,15 ;
b va de 0,65 à 0,95 ;
c va de 0,049 à 0,349 ;
d va de 0,001 à 0,1 ;
2,75 ≤ (a + 2b + 2c + dV) ≤ 3,10, dans laquelle V est la valence de D, et D est un ion métallique sélectionné parmi un ou plusieurs des éléments suivants : le magnésium, le calcium, le strontium, le cobalt, le titane, le zirconium, le molybdène, le vanadium, le niobium, le nickel, le scandium, le chrome, le cuivre, le zinc, le béryllium, le lanthane et l'aluminium, et en outre dans laquelle au moins une portion du phosphate métallique de lithium a une structure olivine ;
dans laquelle l'oxyde métallique de lithium est un oxyde métallique de lithium de nickel, de manganèse, de cobalt, ou de combinaisons de ceux-ci.


 
2. La méthode de la revendication 1, comprenant en outre le pressage de la cathode après le retrait du solvant.
 
3. La méthode de la revendication 2, dans laquelle le pressage est réalisé à une pression allant de 10 MPa à 250 MPa.
 
4. La méthode de la revendication 3, dans laquelle la sphéricité moyenne de l'oxyde métallique de lithium va de 0,4 à 1,0, et facultativement dans laquelle la sphéricité moyenne de l'oxyde métallique de lithium et la sphéricité moyenne du phosphate métallique de lithium ont un rapport qui va de 0,4 à 2,5.
 
5. La méthode de la revendication 1, dans laquelle l'oxyde métallique de lithium a une taille de particule primaire D50 de 3 micromètres à 0,1 micromètre et/ou la taille de particule secondaire D50 de l'oxyde métallique de lithium et la taille de particule secondaire D50 du phosphate métallique de lithium ont un rapport qui va de 0,5 à 1,5.
 
6. Une cathode, pouvant être obtenue par la méthode de la revendication 1, constituée d'une feuille métallique ayant une première face et une deuxième face et un matériau de cathode revêtu sur au moins une face de la feuille, le matériau de cathode étant constitué d'un mélange d'un oxyde métallique de lithium et d'un phosphate métallique de lithium dans laquelle la quantité de phosphate métallique de lithium va de 5 % à 65 % en poids du mélange, dans laquelle l'oxyde métallique de lithium est constitué de particules primaires et secondaires et le phosphate métallique de lithium est constitué de particules primaires et secondaires et les particules secondaires d'oxyde métallique de lithium ont une D50 en nombre et les particules secondaires de phosphate métallique de lithium ont une D50 en nombre telle que la taille de particule secondaire D50 de l'oxyde métallique de lithium et celle du phosphate métallique de lithium aient un rapport compris entre 0,9 et 1,1 ; et
dans laquelle le phosphate métallique de lithium a la formule LiaMnbFecDdPO4, dans laquelle
a est un nombre allant de 0,85 à 1,15 ;
b va de 0,65 à 0,95 ;
c va de 0,049 à 0,349 ;
d va de 0,001 à 0,1 ;
2,75 ≤ (a + 2b + 2c + dV) ≤ 3,10, dans laquelle V est la valence de D, et D est un ion métallique sélectionné parmi un ou plusieurs des éléments suivants : le magnésium, le calcium, le strontium, le cobalt, le titane, le zirconium, le molybdène, le vanadium, le niobium, le nickel, le scandium, le chrome, le cuivre, le zinc, le béryllium, le lanthane et l'aluminium, et en outre dans laquelle au moins une portion du phosphate métallique de lithium a une structure olivine ; et
dans laquelle l'oxyde métallique de lithium est un oxyde métallique de lithium de nickel, de manganèse, de cobalt, ou de combinaisons de ceux-ci.
 
7. La cathode de la revendication 6, dans laquelle le phosphate métallique de lithium a un revêtement conducteur électronique.
 
8. La cathode de la revendication 7, dans laquelle l'oxyde métallique de lithium a un revêtement conducteur électronique qui est le graphite, le carbone amorphe ou une combinaison de ceux-ci.
 
9. La cathode de la revendication 6, dans laquelle la sphéricité moyenne de l'oxyde métallique de lithium va de 0,4 à 1,0 et la sphéricité moyenne du phosphate métallique de lithium va de 0,4 à 1,0 et facultativement dans laquelle la sphéricité moyenne de l'oxyde métallique de lithium et la sphéricité moyenne du phosphate métallique de lithium ont un rapport qui va de 0,4 à 2,5.
 
10. La cathode de la revendication 6, dans laquelle la quantité de phosphate métallique de lithium va de 5 % à 49 % en poids du mélange.
 
11. La cathode de n'importe lesquelles des revendications 6 à 10, dans laquelle D est le magnésium, le cobalt ou un mélange de magnésium et de cobalt.
 
12. La cathode de n'importe lesquelles des revendications 6 à 11, dans laquelle (a + 2b + 2c + dV) ≠ 3,00.
 
13. Une batterie lithium-ion comprenant la cathode de n'importe laquelle des revendications précédentes.
 




Drawing


























Cited references

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