EP4367727A1 - Electrochemical cells and electrode active materials suitable for such electrochemical cells - Google Patents

Electrochemical cells and electrode active materials suitable for such electrochemical cells

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Publication number
EP4367727A1
EP4367727A1 EP22740327.6A EP22740327A EP4367727A1 EP 4367727 A1 EP4367727 A1 EP 4367727A1 EP 22740327 A EP22740327 A EP 22740327A EP 4367727 A1 EP4367727 A1 EP 4367727A1
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EP
European Patent Office
Prior art keywords
range
alkali
cathode active
active material
earth metal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP22740327.6A
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German (de)
French (fr)
Inventor
Xiaohan WU
Doron Aurbach
Sandipan MAITI
Hannah SCHREYER
Eduard L Kunkes
Imke Britta Mueller
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BASF SE
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BASF SE
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Publication of EP4367727A1 publication Critical patent/EP4367727A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • Electrochemical cells and electrode active materials suitable for such electrochemical cells are Electrochemical cells and electrode active materials suitable for such electrochemical cells
  • the present invention is directed to the use of alkali or alkali earth metal ion-containing molecu lar sieves for coating of cathode active materials with a molar manganese content in the range of from 50 to 85 mol-% referring to the metals other than lithium in said cathode active materi als.
  • Lithiated transition metal oxides are currently used as electrode active materials for lithium-ion batteries. Extensive research and developmental work have been performed in the past years to improve properties like charge density, specific energy, but also other properties like the reumbled cycle life and capacity loss that may adversely affect the lifetime or applicability of a lithi um-ion battery. Additional effort has been made to improve manufacturing methods.
  • NCM materials lithiated nickel-cobalt- manganese oxide
  • NCA materials lithiated nickel-cobalt-aluminum oxide
  • a so-called pre cursor is being formed by co-precipitating the transition metals as carbonates, oxides or prefer ably as (oxy)hydroxides.
  • the precursor is then mixed with a lithium compound such as, but not limited to LiOH, LhO or U 2 CO 3 and calcined (fired) at high temperatures.
  • Lithium compound(s) can be employed as hydrate(s) or in dehydrated form.
  • the calcination - or firing - generally also referred to as thermal treatment or heat treatment of the precursor - is usually carried out at temperatures in the range of from 600 to 1 ,000 °C.
  • hydroxides or carbonates are used as precursors a removal of water or carbon dioxide occurs first and is followed by the lithi- ation reaction.
  • the thermal treatment is performed in the heating zone of an oven or kiln.
  • cathode active materials such as energy density, charge-discharge performance such as capacity fading, and the like.
  • energy density energy density
  • charge-discharge performance such as capacity fading
  • cathode active materials suffer from limited cycle life and voltage fade. This applies particularly to many Mn-rich cathode active materials.
  • alkali or alkali earth metal ion-containing molecular sieves may be used for coating electrode active materials for lithium ion batteries, especially anode active material se lected from silicon, lithium and graphite, and cathode active materials with a molar manganese content in the range of from 50 to 85 mol-% referring to the metals other than lithium in said cathode active materials.
  • Such coated cathodes will then less readily release manganese, and such coated anodes will have a reduced tendency of accepting manganese as an undesired coating.
  • Silicon anodes are anodes based on pure silicon or on certain alloys based on silicon, for ex ample Li x Si (0 ⁇ x ⁇ 4.4), Si-Sn alloys, and Fe-Si alloys.
  • Lithium anodes are based on metallic lithium.
  • Graphite electrodes are based on graphite.
  • cathode active materials with a molar manganese content in the range of from 50 to 85 mol-% referring to the metals other than lithium in said cathode active materials include spinel LiM ⁇ CL, high-voltage spinels of an idealized formula LiNio . 5Mn1 .
  • doped high-voltage spinels for example doped with at least one of Na + , Mg 2+ , Al 3+ , Ti 4+ , Cr 3 , Fe 3+ , Zn 2+ , or Co 3+ , and in particular so-called lithium rich materials with a layered structure, general formula Lii +f TMi- f 0 2 wherein f is in the range of from 0.1 to 0.35 and TM in cludes two or more transition metals, and 50 to 85 mol-%of TM is Mn, preferably 60 to 70 mol- %.
  • said cathode active material has the com position Lii +f TMi- f C>2 wherein f is in the range of from 0.1 to 0.35, preferably 0.12 to 0.2, and TM is a combination of elements of the general formula (I a)
  • b is zero and M 1 is enriched in the outer part of the particles of said particulate material, such enrichment being measured, e.g., by cross-sectional microscopic imaging.
  • said cathode active material has the composi tion Lii +g TM * 2-g- h C>4- h wherein g is in the range of from -0.1 to +0.3, h is in the range of from zero to 0.2, and TM* corresponds to formula (I b)
  • M 4 being one or more of Ni, Co, Al, Ti, Zr, W, Mo, Mg, and t being in the range of from to 0.3 to 1.
  • Coated electrode active materials refer to at least 50% of the particles of a batch of particulate cathode active material or anode active material being coated, and to 0.5 to 2.5% of the surface of each particle being coated, for ex ample 0.75 to 1.25 %.
  • said coating has an average thickness in the range of from 2 to 10 nm. Locally, the coating may have a thickness of up to 1 pm. The thickness may be determined by transmission electron microscopy (“TEM”) and ener gy-dispersive X-ray spectroscopy (“EDS”) line scanning.
  • TEM transmission electron microscopy
  • EDS ener gy-dispersive X-ray spectroscopy
  • Molecular sieves in the context of the present invention are inorganic materials with pores of uniform size.
  • Preferred molecular sieves are selected from naturally occurring and synthetic zeolites.
  • alkali or alkali earth metal ion-containing molec ular sieves are used.
  • Suitable alkali metals are sodium and potassium and combinations of the two, and suitable alkali earth metals are magnesium and calcium and combinations of the two. Combinations of alkali and alkali earth metals are possible as well.
  • molecular sieves refers to framework materials. They are based on extensive three- dimensional networks of oxide ions containing generally tetrahedral type sites and having a substantially uniform pore distribution. The pore size is defined by the framework structure. Pre ferred examples of molecular sieves are zeolites, thus aluminosilicates. Their frameworks com prise M 3 04/Si0 4 /AIC> 4 tetrahedra, with M 3 being selected from tetravalent metals such as Ti or Zr, and the majority of the tetrahedra being SiCU/AICU tetrahedra.
  • molecular sieves are agglomerates of crystals of uniform crystal size.
  • the crystal size may be in the range of from 1 to 250 nm.
  • zeolites examples include analcime, chabazite, clinoptilite, heulandite, phil- bodye, natrolite and stilbite.
  • molecular sieves have a pore size of from 2 to 10 A, preferably from 2 to 7 A, and more preferably from 3.5 to 5 A.
  • the pore size refers to the pore diameter, and it is preferably measured by gas adsorption analysis.
  • said molecular sieves comprise YO 2 and X 2 O 3 and, optionally, Z 2 O 5 units in its framework wherein X is selected from trivalent elements, Y is select ed from tetravalent elements and Z is selected from pentavalent elements.
  • the structure may be determined by X-ray diffraction.
  • said alkali or alkali earth metal ion-containing mo lecular sieve comprises S1O 4 /AIO 4 tetrahedra and, optionally, M 3 C> 4 or PO 4 tetrahedra, wherein M 3 is selected from transition metals in the oxidation state of +IV, for example Ti or Zr.
  • molecular sieves have an average particle diame ter in the range of from 500 nm to 5 pm.
  • the particle diameter in this context refers to the diam eter of agglomerates of crystals, such agglomerates being spherical.
  • alkali or alkali earth metal ion-containing molecular sieve is of the general formula M 2 x [(AI0 2 ) x (Si0 2 ) y ] wherein M 2 is selected from alkali metal, alkali earth metal and H and wherein at least 90 mol-% of M 2 is Na.
  • M 2 other than Na may be selected from H, K, Mg, Ca, and from further alkali metals or alkali earth metals.
  • the other variables are defined as follows: x is in the range of from 1 to 150, y is in the range of from 1 to 150, and y/x > 1.
  • the water content of such molecular sieves is preferably very low, for example less than 1000 ppm by weight, more preferably less than 100 ppm.
  • a specific aspect of the present invention is related to electrochemical cells, hereinafter also referred to inventive cells.
  • inventive cells contain
  • anode an anode selected from silicon anodes, graphite anodes and lithium anodes, hereinafter also referred to as anode (A),
  • cathode (B) a cathode, hereinafter also referred to as cathode (B), wherein cathode (B) contains a cath ode active material with a molar manganese content in the range of from 50 to 85 mol-% re ferring to the metals other than lithium contained in said cathode active material, wherein said cathode active material is coated with an alkali or alkali earth metal ion-containing molecular sieve.
  • Anode (A) contains an anode active material that may be - or may be not - coated with an alkali or alkali earth metal ion-containing molecular sieve.
  • Cathode (B) contains a cathode active material with a molar manganese content in the range of from 50 to 85 mol-% referring to the metals other than lithium contained in said cathode active material.
  • Such cathode active materials are hereinafter also referred to as high-manganese ma terials.
  • High-manganese materials may be selected from spinel LiMnaCU, high-voltage spinels of formula Lii +g TM * 2-g-h 0 4-h , preferably an idealized formula LiNio . 5Mn1 .
  • doped high-voltage spinels for example doped with at least one of Na + , Mg 2+ , Al 3+ , Ti 4+ , Cr 3 , Fe 3+ , Zn 2+ , or Co 3+ , and in particular so-called lithium rich high-manganese materials with a layered structure, gen eral formula Lii +f TMi- f 0 2 wherein f is in the range of from 0.1 to 0.35 and TM includes two or more transition metals, and 50 to 85 mol-%of TM is Mn, preferably 60 to 70 mol-%. In a preferred embodiment of the present invention, f is in the range of from 0.12 to 0.2.
  • TM is a combination of elements of the general formula (I a)
  • Coated electrode active materials refer to at least 50% of the particles of a batch of particulate cathode active material being coated, and to 0.5 to 2.5% of the surface of each particle being coated, for example 0.75 to 1.25 %.
  • said coating has an average thickness in the range of from 2 to 10 nm. The thickness may be determined by transmission electron microscopy (“TEM”) and energy-dispersive X-ray spectroscopy (“EDS”) line scanning
  • a coated high-manganese material is usually mixed with a conductive carbon and a binder, for example in the presence of water or preferably of an organ ic solvent, and the resultant slurry is then applied to a current collector, for example an alumi num foil, followed by removal of the solvent (drying) and calendaring.
  • Inventive cells contain components other than anodes and cathodes, for example an electrolyte and a separator, and a housing. Inventive cells are advantageous with respect to high cycling stability, low capacity fade and low internal resistance growth upon repeated cycling.
  • inventive cathode active materials have a core of the composition Lii +f TMi- f C>2 wherein f is in the range of from 0.1 to 0.35 and TM is a combination of metals according to general formula (I a)
  • inventive cathode active materials have a core of the composition Lii +g TM * 2-g-h 0 4-h wherein g is in the range of from -0.1 to +0.3, h is in the range of from zero to 0.2, and TM* corresponds to formula (I b)
  • M 4 being one or more of Ni, Co, Al, Ti, Zr, W, Mo, Mg, and t being in the range of from to 0.3 to 1.
  • inventive cathode active materials have an aver age particle diameter D50 in the range of from 2 to 20 pm, preferably from 5 to 16 pm.
  • the av erage particle diameter may be determined, e. g., by light scattering or LASER diffraction or electroacoustic spectroscopy.
  • the particles are usually composed of agglomerates from primary particles, and the above particle diameter refers to the secondary particle diameter.
  • inventive cathode active materials have a specific surface (BET) in the range of from 0.7 to 4.0 m 2 /g or even up to 6 m 2 /g, determined according to DIN-ISO 9277:2003-05, preferred are 1.0 to 3.8 m 2 /g or even from 3.0 up to 5.5 m 2 /g.
  • BET specific surface
  • Some metals are ubiquitous such as sodium, calcium or zinc and traces of them virtually pre sent everywhere, but such traces will not be taken into account in the description of the present invention. Traces in this context will mean amounts of 0.05 mol-% or less, referring to the total metal content TM.
  • M 1 may be dispersed homogeneously or unevenly in particles of inventive cathode active mate rial.
  • M 1 is distributed unevenly in particles of inventive cathode active material, even more preferably as a gradient, with the concentration of M 1 in the outer shell being higher than in the center of the particles.
  • inventive cathode active material is comprised of spherical particles, that are particles have a spherical shape.
  • Spherical particles shall include not just those which are exactly spherical but also those particles in which the maximum and minimum diameter of at least 90% (number average) of a representative sample differ by not more than 10%.
  • inventive cathode active material is comprised of secondary particles that are agglomerates of primary particles.
  • inventive cathode active material is comprised of spherical secondary particles that are agglomerates of primary particles.
  • inventive cathode active material is comprised of spherical secondary particles that are agglomerates of platelet primary particles.
  • said primary particles of inventive cathode active material have an average diameter in the range from 1 to 2000 nm, preferably from 10 to 1000 nm, particularly preferably from 50 to 500 nm.
  • the average primary particle diameter can, for example, be determined by SEM or TEM. SEM is an abbreviation of scanning electron mi croscopy, TEM is an abbreviation of transmission electron microscopy.
  • inventive cathode active material has a monomod- al particle diameter distribution.
  • inventive cathode active material has a bimodal particle diameter distribution, for example with a maximum in the range of from 3 to 6 pm and another maximum in the range of from 9 to 12 pm.
  • the pressed density of inventive cathode active material is in the range of from 2.75 to 3.1 g/cm 3 , determined at a pressure of 250 MPa, pre ferred are 2.85 to 3.10 g/cm 3 .
  • the coating has been described above. In many embodiments it can be established from TEM and EDS line scanning that the coating is inhomogeneous. It resembles to an island structure rather than a homogeneous coating.
  • a further aspect of the present invention is related to the manufacture of inventive cathode ac tive materials, hereinafter also referred to as inventive process.
  • inventive process compris es the following steps, hereinafter also referred to as step (a), step (b), step (c) and step (d):
  • step (c) removing the water or organic solvent, as the case may be, from step (b),
  • step (d) treating the mixture obtained from step (c) thermally.
  • steps (b) and (c) are performed by mixing said core cathode active material with an alkali or alkali earth metal ion-containing molecular sieve slurried in an Ci-C3-alkanol and removing the Ci-C3-alkanol by evaporation.
  • Core cathode active materials of the general formula may be manufactured by mixing a hydrox ide or carbonate of TM with a source of lithium, for example U2CO3, LiOH, U2O2, UNO3, or a combination of at least two of the foregoing, each in water-free form or as hydrate, and a ther mal treatment such as a calcination at, e.g., 800 to 950°C.
  • a source of lithium for example U2CO3, LiOH, U2O2, UNO3, or a combination of at least two of the foregoing, each in water-free form or as hydrate
  • a ther mal treatment such as a calcination at, e.g., 800 to 950°C.
  • One or more post-treatment steps may follow, e.g., as described in WO 2021/037678.
  • step (b) said core cathode active material is treated with an alkali or alkali earth metal ion- containing molecular sieve slurried in water or in an organic solvent.
  • the weight ratio of core cathode active material provided in step (a) to molecular sieve is in the range of from 400 : 1 to 30 : 1 ; preferably 200 : 1 to 50 : 1.
  • suitable solvents in step (b) are aromatic hydrocarbons such as toluene and xylene including the mixture of at least two of the isomers, and CrC4-alkanols that are liquid at the temperature at which step is performed, for example methanol, ethanol, n-propanol, isopropa nol, n-butanol, iso-butanol and sec.-butanol. At temperatures below 26°C, tert.-butanol is solid, and it is therefore not preferred for many temperatures.
  • aromatic hydrocarbons such as toluene and xylene including the mixture of at least two of the isomers
  • CrC4-alkanols that are liquid at the temperature at which step is performed, for example methanol, ethanol, n-propanol, isopropa nol, n-butanol, iso-butanol and sec.-butanol. At temperatures below 26°C, tert.-butanol
  • the volume ratio of core cathode active material provided in step (a) and of water or organic solvent used in step (b) is in the range of from 1 : 1 to 1:10, preferably 1:2 to 1:5. If more water or organic solvent, respectively, is used, too much liq uid has to be removed in step (c). If too low amounts of water or organic solvent, respectively, are used, the likelihood of an uneven distribution in the sense of non-coated particles is too high.
  • the treatment in step (b) may be achieved by combining a slurry of an alkali or alkali earth met al ion-containing molecular sieve slurried in water or in an organic solvent with core cathode active material as provided in step (a), and mixing.
  • Mixing may be supported by ball-milling, stirring, for example with a high-speed stirrer, or - on laboratory scale - by simple shaking or with a roller-mixer.
  • step (b) is performed at a temperature in the range of from 5 to 80°C, preferably 10 to 50°C. Especially when vigorous stirring is applied, for exam ple by ball-milling or with a high-speed stirrer, a temperature increase may be observed in the course of step (b).
  • step (b) is performed at a pressure in the range of from ambient pressure to 10 bar, ambient pressure to 1 bar being preferred and ambient pres sure even being more preferred.
  • step (b) has a duration in the range of from 5 minutes to 5 hours.
  • step (b) The slurrying efficiency in step (b) may be enhanced by ultra-sound.
  • step (c) the water or, if applicable, organic solvent from step (b) is removed, for example by filtration or preferably by evaporation.
  • the temperature and pressure conditions are adapted to the boiling point of the solvent or water used in step (b).
  • step (c) is performed at a temperature in the range of from 65 to 150°C, preferably 75 to 100°C.
  • step (b) is performed at a pressure in the range of from 10 mbar to ambient pressure, 100 mbar to ambient pressure being preferred and ambient pressure even being more preferred.
  • step (c) has a duration in the range of from 15 minutes to 5 hours.
  • a solid residue is obtained from step (c).
  • step (c) further mixing may be performed.
  • step (d) the residue from step (c) is treated thermally, for example at a temperature in the range of from 120 to 300°C.
  • Step (d) may be performed under air, oxygen, oxygen-enriched air, nitrogen, nitrogen-enriched air or a noble gas, for example argon. Oxygen and air are preferred.
  • step (d) has a duration in the range of from 15 minutes to 10 hours, preferably 1 to 5 hours.
  • An inventive cathode active material is obtained from step (d).
  • steps (b) to (d) are carried out under an atmos phere with reduced CO2 content, e.g., a carbon dioxide content in the range of from 0.01 to 500 ppm by weight, preferred are 0.1 to 50 ppm by weight.
  • the CO2 content may be determined by, e.g., optical methods using infrared light. It is even more preferred to perform steps (b) to (d) under an atmosphere with a carbon dioxide content below detection limit for example with infra- red-light based optical methods.
  • inventive particulate materials may be obtained.
  • an anode active material selected from silicon, lithium and graphite the analogous steps may be performed as with the cathode active material, mutatis mutandis.
  • LiNio .5 Mn 1.5 O 4 , (d50) 12.5 pm, was used, B-CAM.1.
  • Step (c.1) In an air oven at 80°C and under air, the ethanol was then evaporated to dryness and the dried powder material was further mixes in the same roller mixer for another 15 min at 500 rpm at ambient temperature. A residue was obtained.
  • Step (d.1) the residue from step (c.1) was heated at 150 °C for 2 hours under N2 flow in a rotary evaporator equipped with a thermocouple and a heater at 150 °C. CAM.1 was obtained.
  • I.2 Manufacture of inventive coated cathode active material CAM.2
  • Step (b.2) A plastic bottle container was charged with 200 g zeolite-2. An amount of 10 ml of ethanol were added and dispersed under ultrasound for 30 minutes. 9.8 g of B-CAM.1 were added and a slurry was obtained. Cylindrical zirconia balls (1:8 by weight: B-CAM.1: zirconia ball) were added and the plastic bottle with the slurry and the zirconia balls was put on a roller mixer for 2 hours at 500 rpm at ambient temperature.
  • Step (c.2) In an air oven at 80°C and under air, the ethanol was then evaporated to dryness and the dried powder material was further mixes in the same roller mixer for another 15 min at 500 rpm at ambient temperature. A residue was obtained.
  • Step (d.2) the residue from step (c.2) was heated at 150 °C for 2 hours under N2 flow in a rotary evaporator equipped with a thermocouple and a heater. CAM.2 was obtained.
  • Positive electrode PVDF binder (Solef® 5130) was dissolved in NMP (Merck) to produce a 10 wt.% solution.
  • binder solution 3.5 wt.%), carbon black (Super C65, 4 wt.-%) were slurried in NMP.
  • ARE-250 planetary centrifugal mixer
  • B-CAM.1 a comparative cathode active material
  • the solid content of the slurry was adjusted to 62.3%.
  • the slurry was coated onto 15 pm thick Al foil using a Erichsen auto coater. The loading was 6 to 7 mg/cm 2 . Prior to further use, all electrodes were calendared. The thickness of cathode material was 38 pm, corresponding to 9 mg/cm 2 . All electrodes were dried at 105°C for 12 hours before battery assembly.
  • Negative electrode PVDF binder (Solef® 5130) was dissolved in NMP (Merck) to produce a 10 wt.% solution.
  • the negative electrode was composed of 92.5% active material (Graphite; FormulaBT, Super Graphite), 4% carbon black (Super C65), and 3.5% PVDF binder (Solef 5130).
  • the mixture was stirred with a planetary orbital mixer (Thinky, Japan) until the homogeneous slurry was obtained. It was coated then on a Copper foil using a standard doctor’s blade. The coated thick film was then heated at 120 °C for 15 min on a hot plate and 4.0 h in a vacuum oven (set at 120 °C) for complete evaporation of the solvent.
  • the anode loading was ⁇ 3 mg/cm 2 .
  • the anode active was 10% excess than that of the cathode to ensure the full intercalation process during battery cycling and avoid lithium metal deposition on the anode surface.
  • a base electrolyte composition was prepared containing 1M LiPF 6 , 3:7 (w/w) ethylene carbonate : diethyl carbonate, EL base 1.
  • Coin-type half cells (20 m in diameter and 3.2 mm in thickness) comprising a cathode prepared as described under 11.1 and lithium metal as working and counter electrode, respectively, were assembled and sealed in an Ar-filled glove box.
  • the cathode and anode and a separator were superposed in order of cathode // separator // Li foil to produce a half coin cell.
  • 80 pi of the EL base 1 which is described above (11.3) were introduced into the coin cell.
  • a polypropylene separator commercially available from Cellgard was used. The results are found in Table 2.
  • Pouch-type full cells 35 mm x 30 mm
  • a cathode prepared as described under 11.1 and Graphite or coated-graphite as counter electrode, respectively, were assembled and sealed in an Ar-filled glove box.
  • the cathode and anode and a separator were superposed in order of cathode // separator // anode to produce a full pouch cell.
  • 0.4 mL of the EL base 1 which is described above (11.2) were introduced into the pouch cells.

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Abstract

Use of alkali or alkali earth metal ion-containing molecular sieves for coating of cathode active materials with a molar manganese content in the range of from 50 to 85 mol-% referring to the metals other than lithium.

Description

Electrochemical cells and electrode active materials suitable for such electrochemical cells
The present invention is directed to the use of alkali or alkali earth metal ion-containing molecu lar sieves for coating of cathode active materials with a molar manganese content in the range of from 50 to 85 mol-% referring to the metals other than lithium in said cathode active materi als.
Lithiated transition metal oxides are currently used as electrode active materials for lithium-ion batteries. Extensive research and developmental work have been performed in the past years to improve properties like charge density, specific energy, but also other properties like the re duced cycle life and capacity loss that may adversely affect the lifetime or applicability of a lithi um-ion battery. Additional effort has been made to improve manufacturing methods.
Many electrode active materials discussed today are of the type of lithiated nickel-cobalt- manganese oxide (“NCM materials”) or lithiated nickel-cobalt-aluminum oxide (“NCA materials”).
In a typical process for making cathode materials for lithium-ion batteries, first a so-called pre cursor is being formed by co-precipitating the transition metals as carbonates, oxides or prefer ably as (oxy)hydroxides. The precursor is then mixed with a lithium compound such as, but not limited to LiOH, LhO or U2CO3 and calcined (fired) at high temperatures. Lithium compound(s) can be employed as hydrate(s) or in dehydrated form. The calcination - or firing - generally also referred to as thermal treatment or heat treatment of the precursor - is usually carried out at temperatures in the range of from 600 to 1 ,000 °C. In cases hydroxides or carbonates are used as precursors a removal of water or carbon dioxide occurs first and is followed by the lithi- ation reaction. The thermal treatment is performed in the heating zone of an oven or kiln.
Extensive research has been performed on improvement of various properties of cathode active materials, such as energy density, charge-discharge performance such as capacity fading, and the like. However, many cathode active materials suffer from limited cycle life and voltage fade. This applies particularly to many Mn-rich cathode active materials.
In EP 3486 980, specific high-manganese materials with a high energy density retention rate are disclosed. However, the cathode active materials disclosed suffer from a limited energy density as such.
It has been observed, though, that high-manganese materials suffer from Mn leaching in the course of repeated cycling. An increased manganese content may then be detected in the elec- trolyte and on the anode. A continued leaching of manganese may lead to deterioration of the anode protective layer, also known as the solid electrolyte interface causing parasitic consump tion of active lithium and ultimately loss in reversible (cyclable) capacity and cell failure.
It was therefore an objective of the present invention to provide electrochemical cells with a high energy density retention rate but a reduced tendency of capacity fade due to manganese leach ing.
It was found that alkali or alkali earth metal ion-containing molecular sieves may be used for coating electrode active materials for lithium ion batteries, especially anode active material se lected from silicon, lithium and graphite, and cathode active materials with a molar manganese content in the range of from 50 to 85 mol-% referring to the metals other than lithium in said cathode active materials. Such coated cathodes will then less readily release manganese, and such coated anodes will have a reduced tendency of accepting manganese as an undesired coating.
Silicon anodes are anodes based on pure silicon or on certain alloys based on silicon, for ex ample LixSi (0<x<4.4), Si-Sn alloys, and Fe-Si alloys.
Lithium anodes are based on metallic lithium. Graphite electrodes are based on graphite.
In the context of the present invention, such cathode active materials with a molar manganese content in the range of from 50 to 85 mol-% referring to the metals other than lithium in said cathode active materials include spinel LiM^CL, high-voltage spinels of an idealized formula LiNio.5Mn1.5O4, doped high-voltage spinels, for example doped with at least one of Na+, Mg2+, Al3+, Ti4+, Cr3 , Fe3+, Zn2+, or Co3+, and in particular so-called lithium rich materials with a layered structure, general formula Lii+fTMi-f02 wherein f is in the range of from 0.1 to 0.35 and TM in cludes two or more transition metals, and 50 to 85 mol-%of TM is Mn, preferably 60 to 70 mol- %.
In a preferred embodiment of the present invention, said cathode active material has the com position Lii+fTMi-fC>2 wherein f is in the range of from 0.1 to 0.35, preferably 0.12 to 0.2, and TM is a combination of elements of the general formula (I a)
(NiaCObMnc)i-dM1d (I a) wherein a is in the range of from 0.25 to 0.40, b being in the range of from zero to 0.15, more preferably, b is zero, c is in the range of from 0.60 to 0.70, and d is in the range of from zero to 0.02,
M1 is selected from Al, Ti, Zr, W, Mo, Mg, and Nb, and combinations of at least two of the fore going, and a + b + c = 1.
In one embodiment of the present invention, b is zero and M1 is enriched in the outer part of the particles of said particulate material, such enrichment being measured, e.g., by cross-sectional microscopic imaging.
In another embodiment of the present invention, said cathode active material has the composi tion Lii+gTM*2-g-hC>4-h wherein g is in the range of from -0.1 to +0.3, h is in the range of from zero to 0.2, and TM* corresponds to formula (I b)
M4 tMn2-t with
M4 being one or more of Ni, Co, Al, Ti, Zr, W, Mo, Mg, and t being in the range of from to 0.3 to 1.
In a preferred version, M4 is nickel and t = 0.5.
Coated electrode active materials as discussed in the context with the present invention refer to at least 50% of the particles of a batch of particulate cathode active material or anode active material being coated, and to 0.5 to 2.5% of the surface of each particle being coated, for ex ample 0.75 to 1.25 %. In one embodiment of the present invention, said coating has an average thickness in the range of from 2 to 10 nm. Locally, the coating may have a thickness of up to 1 pm. The thickness may be determined by transmission electron microscopy (“TEM”) and ener gy-dispersive X-ray spectroscopy (“EDS”) line scanning.
Molecular sieves in the context of the present invention are inorganic materials with pores of uniform size. Preferred molecular sieves are selected from naturally occurring and synthetic zeolites. In the context of the present invention, alkali or alkali earth metal ion-containing molec ular sieves are used. Suitable alkali metals are sodium and potassium and combinations of the two, and suitable alkali earth metals are magnesium and calcium and combinations of the two. Combinations of alkali and alkali earth metals are possible as well.
The term “molecular sieves” refers to framework materials. They are based on extensive three- dimensional networks of oxide ions containing generally tetrahedral type sites and having a substantially uniform pore distribution. The pore size is defined by the framework structure. Pre ferred examples of molecular sieves are zeolites, thus aluminosilicates. Their frameworks com prise M304/Si04/AIC>4 tetrahedra, with M3 being selected from tetravalent metals such as Ti or Zr, and the majority of the tetrahedra being SiCU/AICU tetrahedra.
Preferably, molecular sieves are agglomerates of crystals of uniform crystal size. The crystal size may be in the range of from 1 to 250 nm.
Examples of naturally occurring zeolites are analcime, chabazite, clinoptilite, heulandite, phil- lipsite, natrolite and stilbite.
In a preferred embodiment, molecular sieves have a pore size of from 2 to 10 A, preferably from 2 to 7 A, and more preferably from 3.5 to 5 A. The pore size refers to the pore diameter, and it is preferably measured by gas adsorption analysis.
In one embodiment of the present invention, said molecular sieves comprise YO2 and X2O3 and, optionally, Z2O5 units in its framework wherein X is selected from trivalent elements, Y is select ed from tetravalent elements and Z is selected from pentavalent elements. The structure may be determined by X-ray diffraction.
In one embodiment of the present invention, said alkali or alkali earth metal ion-containing mo lecular sieve comprises S1O4/AIO4 tetrahedra and, optionally, M3C>4 or PO4 tetrahedra, wherein M3 is selected from transition metals in the oxidation state of +IV, for example Ti or Zr.
In one embodiment of the present invention, molecular sieves have an average particle diame ter in the range of from 500 nm to 5 pm. The particle diameter in this context refers to the diam eter of agglomerates of crystals, such agglomerates being spherical.
In a preferred embodiment, alkali or alkali earth metal ion-containing molecular sieve is of the general formula M2 x[(AI02)x(Si02)y] wherein M2 is selected from alkali metal, alkali earth metal and H and wherein at least 90 mol-% of M2 is Na. M2 other than Na may be selected from H, K, Mg, Ca, and from further alkali metals or alkali earth metals. The other variables are defined as follows: x is in the range of from 1 to 150, y is in the range of from 1 to 150, and y/x > 1.
For example, 1<y/x<500 and preferably 1<y/x<35.
The water content of such molecular sieves is preferably very low, for example less than 1000 ppm by weight, more preferably less than 100 ppm.
A specific aspect of the present invention is related to electrochemical cells, hereinafter also referred to inventive cells. Inventive cells contain
(A) an anode selected from silicon anodes, graphite anodes and lithium anodes, hereinafter also referred to as anode (A),
(B) a cathode, hereinafter also referred to as cathode (B), wherein cathode (B) contains a cath ode active material with a molar manganese content in the range of from 50 to 85 mol-% re ferring to the metals other than lithium contained in said cathode active material, wherein said cathode active material is coated with an alkali or alkali earth metal ion-containing molecular sieve.
Inventive cells will be described in more detail below.
Inventive cells comprise an anode (A). Anode (A) contains an anode active material that may be - or may be not - coated with an alkali or alkali earth metal ion-containing molecular sieve.
Cathode (B) contains a cathode active material with a molar manganese content in the range of from 50 to 85 mol-% referring to the metals other than lithium contained in said cathode active material. Such cathode active materials are hereinafter also referred to as high-manganese ma terials. High-manganese materials may be selected from spinel LiMnaCU, high-voltage spinels of formula Lii+gTM* 2-g-h04-h, preferably an idealized formula LiNio.5Mn1.5O4, doped high-voltage spinels, for example doped with at least one of Na+, Mg2+, Al3+, Ti4+, Cr3 , Fe3+, Zn2+, or Co3+, and in particular so-called lithium rich high-manganese materials with a layered structure, gen eral formula Lii+fTMi-f02 wherein f is in the range of from 0.1 to 0.35 and TM includes two or more transition metals, and 50 to 85 mol-%of TM is Mn, preferably 60 to 70 mol-%. In a preferred embodiment of the present invention, f is in the range of from 0.12 to 0.2.
In a preferred embodiment of the present invention, TM is a combination of elements of the general formula (I a)
(NiaCObMnc)i-dM1d (I a) wherein a is in the range of from 0.25 to 0.40, b being in the range of from zero to 0.15, more preferably, b is zero, c is in the range of from 0.60 to 0.70, and d is in the range of from zero to 0.02,
M1 is selected from Al, Ti, Zr, W, Mo, Mg, and Nb, and combinations of at least two of the fore going, and a + b + c = 1.
Coated electrode active materials as discussed in the context with the present invention refer to at least 50% of the particles of a batch of particulate cathode active material being coated, and to 0.5 to 2.5% of the surface of each particle being coated, for example 0.75 to 1.25 %. In one embodiment of the present invention, said coating has an average thickness in the range of from 2 to 10 nm. The thickness may be determined by transmission electron microscopy (“TEM”) and energy-dispersive X-ray spectroscopy (“EDS”) line scanning
Molecular sieves including their pore size are described in more detail above.
For the manufacture of cathodes (B), a coated high-manganese material is usually mixed with a conductive carbon and a binder, for example in the presence of water or preferably of an organ ic solvent, and the resultant slurry is then applied to a current collector, for example an alumi num foil, followed by removal of the solvent (drying) and calendaring.
Inventive cells contain components other than anodes and cathodes, for example an electrolyte and a separator, and a housing. Inventive cells are advantageous with respect to high cycling stability, low capacity fade and low internal resistance growth upon repeated cycling.
A further aspect of the present invention relates to specific coated cathode active materials, hereinafter also referred to as inventive cathode active materials. In one embodiment of the present invention, inventive cathode active materials have a core of the composition Lii+fTMi-fC>2 wherein f is in the range of from 0.1 to 0.35 and TM is a combination of metals according to general formula (I a)
(NiaCObMnc)i-dM1d (I a) wherein a is in the range of from 0.25 to 0.40, b being in the range of from zero to 0.15, more preferably, b is zero, c being in the range of from 0.60 to 0.70, and d being in the range of from zero to 0.02,
M1 is selected from Al, Ti, Zr, W, Mo, Mg, and Nb, and a + b + c = 1 , and they are coated with an alkali or alkali earth metal ion-containing molecular sieve, hereinaf ter also referred to as the coating.
In one embodiment of the present invention, inventive cathode active materials have a core of the composition Lii+gTM* 2-g-h04-h wherein g is in the range of from -0.1 to +0.3, h is in the range of from zero to 0.2, and TM* corresponds to formula (I b)
M4 tMn2-t with
M4 being one or more of Ni, Co, Al, Ti, Zr, W, Mo, Mg, and t being in the range of from to 0.3 to 1.
In a preferred version, M4 is nickel and t = 0.5. In one embodiment of the present invention, inventive cathode active materials have an aver age particle diameter D50 in the range of from 2 to 20 pm, preferably from 5 to 16 pm. The av erage particle diameter may be determined, e. g., by light scattering or LASER diffraction or electroacoustic spectroscopy. The particles are usually composed of agglomerates from primary particles, and the above particle diameter refers to the secondary particle diameter.
In one embodiment of the present invention inventive cathode active materials have a specific surface (BET) in the range of from 0.7 to 4.0 m2/g or even up to 6 m2/g, determined according to DIN-ISO 9277:2003-05, preferred are 1.0 to 3.8 m2/g or even from 3.0 up to 5.5 m2/g.
Some metals are ubiquitous such as sodium, calcium or zinc and traces of them virtually pre sent everywhere, but such traces will not be taken into account in the description of the present invention. Traces in this context will mean amounts of 0.05 mol-% or less, referring to the total metal content TM.
M1 may be dispersed homogeneously or unevenly in particles of inventive cathode active mate rial. Preferably, M1 is distributed unevenly in particles of inventive cathode active material, even more preferably as a gradient, with the concentration of M1 in the outer shell being higher than in the center of the particles.
In one embodiment of the present invention, inventive cathode active material is comprised of spherical particles, that are particles have a spherical shape. Spherical particles shall include not just those which are exactly spherical but also those particles in which the maximum and minimum diameter of at least 90% (number average) of a representative sample differ by not more than 10%.
In one embodiment of the present invention, inventive cathode active material is comprised of secondary particles that are agglomerates of primary particles. Preferably, inventive cathode active material is comprised of spherical secondary particles that are agglomerates of primary particles. Even more preferably, inventive cathode active material is comprised of spherical secondary particles that are agglomerates of platelet primary particles.
In one embodiment of the present invention, said primary particles of inventive cathode active material have an average diameter in the range from 1 to 2000 nm, preferably from 10 to 1000 nm, particularly preferably from 50 to 500 nm. The average primary particle diameter can, for example, be determined by SEM or TEM. SEM is an abbreviation of scanning electron mi croscopy, TEM is an abbreviation of transmission electron microscopy.
In one embodiment of the present invention, inventive cathode active material has a monomod- al particle diameter distribution. In an alternative embodiment, inventive cathode active material has a bimodal particle diameter distribution, for example with a maximum in the range of from 3 to 6 pm and another maximum in the range of from 9 to 12 pm.
In one embodiment of the present invention, the pressed density of inventive cathode active material is in the range of from 2.75 to 3.1 g/cm3, determined at a pressure of 250 MPa, pre ferred are 2.85 to 3.10 g/cm3.
The coating has been described above. In many embodiments it can be established from TEM and EDS line scanning that the coating is inhomogeneous. It resembles to an island structure rather than a homogeneous coating.
A further aspect of the present invention is related to the manufacture of inventive cathode ac tive materials, hereinafter also referred to as inventive process. The inventive process compris es the following steps, hereinafter also referred to as step (a), step (b), step (c) and step (d):
(a) providing a core cathode active material of the general formula Lii+fTMi-fC>2,
(b) treating said core cathode active material with an alkali or alkali earth metal ion-containing molecular sieve slurried in water or in an organic solvent,
(c) removing the water or organic solvent, as the case may be, from step (b),
(d) treating the mixture obtained from step (c) thermally.
Ina preferred embodiment of the present invention, steps (b) and (c) are performed by mixing said core cathode active material with an alkali or alkali earth metal ion-containing molecular sieve slurried in an Ci-C3-alkanol and removing the Ci-C3-alkanol by evaporation.
Core cathode active materials of the general formula may be manufactured by mixing a hydrox ide or carbonate of TM with a source of lithium, for example U2CO3, LiOH, U2O2, UNO3, or a combination of at least two of the foregoing, each in water-free form or as hydrate, and a ther mal treatment such as a calcination at, e.g., 800 to 950°C. One or more post-treatment steps may follow, e.g., as described in WO 2021/037678.
In step (b), said core cathode active material is treated with an alkali or alkali earth metal ion- containing molecular sieve slurried in water or in an organic solvent. In one embodiment of the present invention, the weight ratio of core cathode active material provided in step (a) to molecular sieve is in the range of from 400 : 1 to 30 : 1 ; preferably 200 : 1 to 50 : 1.
Examples of suitable solvents in step (b) are aromatic hydrocarbons such as toluene and xylene including the mixture of at least two of the isomers, and CrC4-alkanols that are liquid at the temperature at which step is performed, for example methanol, ethanol, n-propanol, isopropa nol, n-butanol, iso-butanol and sec.-butanol. At temperatures below 26°C, tert.-butanol is solid, and it is therefore not preferred for many temperatures.
In one embodiment of the present invention, the volume ratio of core cathode active material provided in step (a) and of water or organic solvent used in step (b) is in the range of from 1 : 1 to 1:10, preferably 1:2 to 1:5. If more water or organic solvent, respectively, is used, too much liq uid has to be removed in step (c). If too low amounts of water or organic solvent, respectively, are used, the likelihood of an uneven distribution in the sense of non-coated particles is too high.
The treatment in step (b) may be achieved by combining a slurry of an alkali or alkali earth met al ion-containing molecular sieve slurried in water or in an organic solvent with core cathode active material as provided in step (a), and mixing. Mixing may be supported by ball-milling, stirring, for example with a high-speed stirrer, or - on laboratory scale - by simple shaking or with a roller-mixer.
In one embodiment of the present invention, step (b) is performed at a temperature in the range of from 5 to 80°C, preferably 10 to 50°C. Especially when vigorous stirring is applied, for exam ple by ball-milling or with a high-speed stirrer, a temperature increase may be observed in the course of step (b).
In one embodiment of the present invention, step (b) is performed at a pressure in the range of from ambient pressure to 10 bar, ambient pressure to 1 bar being preferred and ambient pres sure even being more preferred.
In one embodiment of the present invention, step (b) has a duration in the range of from 5 minutes to 5 hours.
The slurrying efficiency in step (b) may be enhanced by ultra-sound. In step (c), the water or, if applicable, organic solvent from step (b) is removed, for example by filtration or preferably by evaporation. The temperature and pressure conditions are adapted to the boiling point of the solvent or water used in step (b).
In one embodiment of the present invention, step (c) is performed at a temperature in the range of from 65 to 150°C, preferably 75 to 100°C.
In one embodiment of the present invention, step (b) is performed at a pressure in the range of from 10 mbar to ambient pressure, 100 mbar to ambient pressure being preferred and ambient pressure even being more preferred.
In one embodiment of the present invention, step (c) has a duration in the range of from 15 minutes to 5 hours. A solid residue is obtained from step (c).
In one embodiment of the present invention, after step (c), further mixing may be performed.
In step (d), the residue from step (c) is treated thermally, for example at a temperature in the range of from 120 to 300°C.
Step (d) may be performed under air, oxygen, oxygen-enriched air, nitrogen, nitrogen-enriched air or a noble gas, for example argon. Oxygen and air are preferred.
In one embodiment of the present invention, step (d) has a duration in the range of from 15 minutes to 10 hours, preferably 1 to 5 hours. An inventive cathode active material is obtained from step (d).
In one embodiment of the present invention, steps (b) to (d) are carried out under an atmos phere with reduced CO2 content, e.g., a carbon dioxide content in the range of from 0.01 to 500 ppm by weight, preferred are 0.1 to 50 ppm by weight. The CO2 content may be determined by, e.g., optical methods using infrared light. It is even more preferred to perform steps (b) to (d) under an atmosphere with a carbon dioxide content below detection limit for example with infra- red-light based optical methods.
By the inventive process excellent inventive particulate materials may be obtained. When it is intended to coat an anode active material selected from silicon, lithium and graphite, the analogous steps may be performed as with the cathode active material, mutatis mutandis.
The invention is further illustrated by working examples.
As core cathode active material, LiNio.5Mn1.5O4 , (d50) = 12.5 pm, was used, B-CAM.1.
The following molecular sieves were used:
Table 1 Description of Zeolites employed as cathode active material coating. rpm: revolutions per minute rotavap: apparatus for rotary evaporation
I. Manufacture of inventive coated cathode active materials
1.1 Manufacture of inventive coated cathode active material CAM.1
Step (a.1 ): 9.9 g of B-CAM.1 were provided.
Step (b.1 ): A plastic bottle container was charged with 100 mg zeolite-1. An amount of 10 ml of ethanol were added and dispersed under ultrasound for 30 minutes. 9.9 g of B-CAM.1 were added and a slurry was obtained. Cylindrical zirconia balls (1:8 by weight: B-CAM.1: zirconia ball) were added and the plastic bottle with the slurry and the zirconia balls was put on a roller mixer for 2 hours at 500 rpm at ambient temperature.
Step (c.1): In an air oven at 80°C and under air, the ethanol was then evaporated to dryness and the dried powder material was further mixes in the same roller mixer for another 15 min at 500 rpm at ambient temperature. A residue was obtained.
Step (d.1): the residue from step (c.1) was heated at 150 °C for 2 hours under N2 flow in a rotary evaporator equipped with a thermocouple and a heater at 150 °C. CAM.1 was obtained. I.2 Manufacture of inventive coated cathode active material CAM.2
Step (a.2): 9.8 g of B-CAM.1 were provided.
Step (b.2): A plastic bottle container was charged with 200 g zeolite-2. An amount of 10 ml of ethanol were added and dispersed under ultrasound for 30 minutes. 9.8 g of B-CAM.1 were added and a slurry was obtained. Cylindrical zirconia balls (1:8 by weight: B-CAM.1: zirconia ball) were added and the plastic bottle with the slurry and the zirconia balls was put on a roller mixer for 2 hours at 500 rpm at ambient temperature.
Step (c.2): In an air oven at 80°C and under air, the ethanol was then evaporated to dryness and the dried powder material was further mixes in the same roller mixer for another 15 min at 500 rpm at ambient temperature. A residue was obtained.
Step (d.2): the residue from step (c.2) was heated at 150 °C for 2 hours under N2 flow in a rotary evaporator equipped with a thermocouple and a heater. CAM.2 was obtained.
II. Testing of inventive coated cathode active materials
11.1 Cathode Manufacture
Positive electrode: PVDF binder (Solef® 5130) was dissolved in NMP (Merck) to produce a 10 wt.% solution. For electrode preparation, binder solution (3.5 wt.%), carbon black (Super C65, 4 wt.-%) were slurried in NMP. After mixing using a planetary centrifugal mixer (ARE-250, Thinky Corp.; Japan), either any of inventive CAM.1 to CAM.7 or a comparative cathode active material, for example B-CAM.1 (92.5 wt.%) was added and the suspension was mixed again to obtain a lump-free slurry. The solid content of the slurry was adjusted to 62.3%. The slurry was coated onto 15 pm thick Al foil using a Erichsen auto coater. The loading was 6 to 7 mg/cm2. Prior to further use, all electrodes were calendared. The thickness of cathode material was 38 pm, corresponding to 9 mg/cm2. All electrodes were dried at 105°C for 12 hours before battery assembly.
11.2 Anode Manufacture
Lithium foil (diameter = 15 mm, thickness = 300 pm; Honjo, Japan) was used as a counter as well as reference electrode for the half-coin cell fabrication.
Negative electrode: PVDF binder (Solef® 5130) was dissolved in NMP (Merck) to produce a 10 wt.% solution. The negative electrode was composed of 92.5% active material (Graphite; FormulaBT, Super Graphite), 4% carbon black (Super C65), and 3.5% PVDF binder (Solef 5130). The mixture was stirred with a planetary orbital mixer (Thinky, Japan) until the homogeneous slurry was obtained. It was coated then on a Copper foil using a standard doctor’s blade. The coated thick film was then heated at 120 °C for 15 min on a hot plate and 4.0 h in a vacuum oven (set at 120 °C) for complete evaporation of the solvent. The anode loading was ~3 mg/cm2. The anode active was 10% excess than that of the cathode to ensure the full intercalation process during battery cycling and avoid lithium metal deposition on the anode surface.
Prior to further use, all electrodes were calendared. The anodes were dried separately overnight under vacuum at 120 °C before cell preparation and were transferred into an Ar filled glovebox without exposure to ambient air.
11.3: Electrolyte Manufacture
A base electrolyte composition was prepared containing 1M LiPF6, 3:7 (w/w) ethylene carbonate : diethyl carbonate, EL base 1.
11.4 Coin-type half cell manufacture
Coin-type half cells (20 m in diameter and 3.2 mm in thickness) comprising a cathode prepared as described under 11.1 and lithium metal as working and counter electrode, respectively, were assembled and sealed in an Ar-filled glove box. In addition, the cathode and anode and a separator were superposed in order of cathode // separator // Li foil to produce a half coin cell. Thereafter, 80 pi of the EL base 1 which is described above (11.3) were introduced into the coin cell. A polypropylene separator commercially available from Cellgard was used. The results are found in Table 2.
11.5 Pouch-type full cell manufacture
Pouch-type full cells (35 mm x 30 mm) comprising a cathode prepared as described under 11.1 and Graphite or coated-graphite as counter electrode, respectively, were assembled and sealed in an Ar-filled glove box. In addition, the cathode and anode and a separator were superposed in order of cathode // separator // anode to produce a full pouch cell. Thereafter, 0.4 mL of the EL base 1 which is described above (11.2) were introduced into the pouch cells.
The results are summarized in Tables 2 and 3. Table 2 Cycling performance of inventive coated cathode active materials in coin half cells vs. Li at 30 °C Table 3 Cycling performance of inventive coated cathode active materials in full pouch cells vs. Graphite at 30 °C

Claims

Patent Claims
1. Electrochemical cell containing
(A) an anode selected from silicon anodes, graphite anodes and lithium anodes,
(B) a cathode containing a lithium-based cathode active material with a molar manganese content in the range of from 50 to 85 mol-% referring to the metals other than lithium contained in said cathode active material, wherein said cathode active material is coated with an alkali or alkali earth metal ion- containing molecular sieve.
2. Electrochemical cell according to claim 1 wherein said molecular sieves have a pore size of from 2 to 10 A measured by gas adsorption analysis.
3. Electrochemical cell according to claim 1 or 2 wherein said cathode active material has the composition Lii+fTMi-fC>2 wherein f is in the range of from 0.1 to 0.35 and TM is a com bination of elements of the general formula (I a)
(NiaCObMnc)i-dM1d (I a) wherein a is in the range of from 0.25 to 0.40, b being in the range of from zero to 0.15, c being in the range of from 0.60 to 0.70, and d being in the range of from zero to 0.02,
M1 is selected from Al, Ti, Zr, W, Mo, Mg, and Nb, and a + b + c = 1.
4. Electrochemical cell according to claim 1 or 2 wherein said cathode active material has the composition Lii+gTM* 2-g-h04-h wherein g is in the range of from -0.1 to +0.3, h is in the range of from zero to 0.2, and TM* corresponds to formula (I b)
M4 tMn2-t with M4 being one or more of Ni, Co, Al, Ti, Zr, W, Mo, Mg, and t being in the range of from to 0.3 to 1.
5. Electrochemical cell according to any of claims 1 to 4 wherein both anode active material and cathode active material are coated with an alkali or alkali earth metal ion-containing molecular sieve.
6. Particulate material having a core of the composition Lii+fTMi-fC>2 wherein f is in the range of from 0.1 to 0.35 and TM is a combination of metals according to general formula (I a)
(NiaCObMric)l-dM1d (I a) wherein a is in the range of from 0.25 to 0.40, b being in the range of from zero to 0.15, c being in the range of from 0.60 to 0.70, and d being in the range of from zero to 0.02,
M1 is selected from Al, Ti, Zr, W, Mo, Mg, and Nb, and a + b + c = 1, or Li1+gTM* 2-g.h04-h wherein g is in the range of from -0.1 to +0.3, h is in the range of from zero to 0.2, and TM* corresponds to formula (I b)
M4 tMn2-t with
M4 being one or more of Ni, Co, Al, Ti, Zr, W, Mo, Mg, and t being in the range of from to 0.3 to 1 , and wherein said cathode active material is coated with an alkali or alkali earth metal ion- containing molecular sieve.
7. Particulate material according to claim 6 wherein b is zero and wherein M1 is enriched in the outer part of the particles of said particulate material, such enrichment being meas ured by cross-sectional microscopic imaging.
8. Particulate material according to claim 6 or 7 wherein said alkali or alkali earth metal ion- containing molecular sieve has a pore size of from 2 to 10 A measured by gas adsorption analysis.
9. Particulate material according to any of the claims 6 to 8 wherein said alkali or alkali earth metal ion-containing molecular sieve comprises YO2 and X2O3 and, optionally, Z2O5 units in its framework wherein X is selected from trivalent elements, Y is selected from tetrava- lent elements and Z is selected from pentavalent elements.
10. Particulate material according to any of the claims 6 to 9 wherein said alkali or alkali earth metal ion-containing molecular sieve comprises S1O4/AIO4 tetrahedra and, optionally,
M304 or PO4 tetrahedra, wherein M3 is selected from transition metals in the oxidation state of +IV.
11. Particulate material according to any of the claims 6 to 10 wherein said alkali or alkali earth metal ion-containing molecular sieve is of the general formula M2 x[(AI02)x(Si02)y] wherein
M2 is selected from alkali metal, alkali earth metal and H wherein at least 90 mol-% of M2 is Na, x is in the range of from 1 to 150, y is in the range of from 1 to 150, and x/y £ 1.
12. Particulate material according to any of the claims 6 to 11 wherein said material has an average particle diameter (D50) in the range of from 2 to 20 pm, determined by light scat tering or LASER diffraction or electroacoustic spectroscopy.
13. Process for manufacturing a particulate material according to any of claims 6 to 12 where in said process comprises the following steps:
(a) providing a core cathode active material of the general formula Lii+fTMi-fC>2 or Lil+gTM*2-g-h04-h, (b) treating said core cathode active material with an alkali or alkali earth metal ion- containing molecular sieve slurried in water or in an organic solvent,
(c) removing the water or organic solvent from step (b),
(d) treating the mixture obtained from step (c) thermally.
14. Process according to claim 13 wherein steps (b) and (c) are performed by mixing said core cathode active material with an alkali or alkali earth metal ion-containing molecular sieve slurried in an CrC3-alkanol and removing the CrC3-alkanol by evaporation.
EP22740327.6A 2021-07-08 2022-06-24 Electrochemical cells and electrode active materials suitable for such electrochemical cells Withdrawn EP4367727A1 (en)

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