Cathode Active Material, and Lithium Ion Battery Comprising Said Cathode Active Material

Abstract

A device for monitoring the use of a pressure container system of a piece of equipment, such as a motor vehicle, is designed to ascertain equipment-side usage data relating to previous use of the pressure container system. The device is additionally designed to compare the equipment-side usage data with equipment-external usage data relating to the previous use of the pressure container system and to initiate one or more measures relating to further use of the pressure container system on the basis of the comparison.

Claims

1-12. (canceled)

13. An active cathode material for a lithium ion battery, the active cathode material comprising: particles having a core-shell structure, each of the particles having a core comprising a core material and a shell comprising a shell material, wherein the core material is selected from the group consisting of: a layered oxide, including an overlithiated layered oxide, a compound having olivine structure, a compound having spinel structure, and combinations thereof, the shell material comprises an olivine compound, and the shell material and/or the core material is at least partly delithiated.

14. The active cathode material according to claim 13, wherein the shell material comprises an iron- and/or manganese-containing olivine.

15. The active cathode material according to claim 14, wherein the shell material comprises Li.sub.xFePO.sub.4 or Li.sub.xFe.sub.yMn.sub.1-yPO.sub.4 with 0≤x≤1 and 0≤y≤1.

16. The active cathode material according to claim 13, wherein the shell material has a lithiation level x≤0.9.

17. The active cathode material according to claim 13, wherein the particles have a diameter of from 0.1 μm to 40 μm inclusive.

18. The active cathode material according to claim 17, wherein the particles have a diameter of from 1 μm to 20 μm inclusive.

19. The active cathode material according to claim 13, wherein the shell has a thickness of from 0.01 μm to 5 μm inclusive.

20. The active cathode material according to claim 19, wherein the shell has a thickness of from 0.05 μm to 1 μm inclusive.

21. The active cathode material according to claim 13, wherein the core is fully lithiated.

22. A process for producing a cathode having an active cathode material according to claim 13, wherein the cathode is produced with at least one electrode binder and water as a carrier solvent.

23. A lithium ion battery comprising: a cathode having an active cathode material according to claim 13.

24. The lithium ion battery according to claim 23, wherein the cathode contains at least one aqueously processible electrode binder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The individual figures show, in schematic form:

[0032] FIG. 1 the construction of a lithium ion battery in one working example, and

[0033] FIG. 2 a particle of the active cathode material in the working example.

[0034] The constituents shown and the size ratios of the constituents relative to one another should not be considered to be true to scale.

DETAILED DESCRIPTION OF THE DRAWINGS

[0035] The lithium ion battery 10 shown in purely schematic form in FIG. 1 has a cathode 2 and an anode 5. The cathode 2 and the anode 5 each have a current collector 1, 6, where the current collectors may be executed as metal foils. The current collector 1 of the cathode 2 may include aluminum, for example, and the current collector 6 of the anode 5 may include copper.

[0036] The cathode 2 and the anode 5 are separated from one another by a separator 4 which is permeable to lithium ions but impermeable to electrons. Separators used may be polymers, especially a polymer selected from the group consisting of polyesters, especially polyethylene terephthalate, polyolefins, especially polyethylene and/or polypropylene, polyacrylonitriles, polyvinylidene fluoride, polyvinylidene-hexafluoropropylene, polyetherimide, polyimide, aramid, polyether, polyetherketone, synthetic spider silk or mixtures thereof. The separator may optionally additionally be coated with ceramic material and a binder, for example, based on Al.sub.2O.sub.3.

[0037] In addition, the lithium ion battery includes an electrolyte 3 which is conductive to lithium ions and which may be a solid state electrolyte or a liquid comprising a solvent and at least one conductive lithium salt dissolved therein, for example, lithium hexafluorophosphate (LiPF.sub.6). The solvent is preferably inert. Suitable solvents are, for example, organic solvents such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluorethylene carbonate (FEC), sulfolane, 2-methyltetrahydrofuran, acetonitrile and 1,3-dioxolane. Solvents used may also be ionic liquids. Such ionic liquids contain exclusively ions. Preferred cations, which may especially be alkylated, are imidazolium, pyridinium, pyrrolidinium, guanidinium, uronium, thiuronium, piperidinium, morpholinium, sulfonium, ammonium and phosphonium cations. Examples of usable anions are halide, tetrafluoroborate, trifluoroacetate, triflate, hexafluorophosphate, phosphonate and tosylate anions. Illustrative ionic liquids include: N-methyl-N-propyl-piperidinium bis(trifluoromethyl sulfonyl)imide, N-methyl-N-butylpyrrolidinium bis(trifluoromethyl-sulfonyl)imide, N-butyl-N-trimethylammonium bis-(trifluoromethylsulfonyl)imide, triethylsulfonium bis(trifluoromethylsulfonyl)imide and N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethyl-sulfonyl)imide. In one variant, it is possible to use two or more of the abovementioned liquids. Preferred conductive salts are lithium salts that have inert anions and are preferably nontoxic. Suitable lithium salts are especially lithium hexafluorophosphate (LiPF.sub.6), lithium tetrafluoroborate (LiBF.sub.4), and mixtures of these salts. The separator 4 may be impregnated or wetted with the lithium salt electrolyte if it is liquid.

[0038] The anode 5 includes an active anode material. The active anode material may be selected from the group consisting of carbonaceous materials, silicon, silicon suboxide, silicon alloys, aluminum alloys, indium, indium alloys, tin, tin alloys, cobalt alloys and mixtures thereof. The active anode material is preferably selected from the group consisting of synthetic graphite, natural graphite, graphene, mesocarbon, doped carbon, hard carbon, soft carbon, fullerene, silicon-carbon composite, silicon, surface-coated silicon, silicon suboxide, silicon alloys, lithium, aluminum alloys, indium, tin alloys, cobalt alloys and mixtures thereof. In principle, further active anode materials known from the prior art are also suitable, for example including niobium pentoxide, titanium dioxide, titanates such as lithium titanate (Li.sub.4Ti.sub.5O.sub.12), tin dioxide, lithium, lithium alloys and/or mixtures thereof.

[0039] The cathode 2 in the lithium ion battery 10 has an active cathode material having a core-shell structure. The active cathode material has a multitude of particles 11. One particle 11 is shown schematically in FIG. 2. The particles 11 each have a core 12 and a shell 13. The diameter D of the particles 11 of the active cathode material, on average, is from 0.1 μm to 40 μm inclusive, preferably from 1 μm to 20 μm inclusive. The shell 13 of the particles 11, on average, has a thickness d in the range from 0.01 μm to 5 μm inclusive, preferably from 0.05 μm to 1 μm inclusive.

[0040] The material of the core 12 may be a layered oxide, for example NMC, NCA or LCO. The layered oxide may especially be an overlithiated layered oxide (OLO). Alternatively, the material of the core 12 may include a compound having spinel structure, for example LMO or LNMO, or a compound having olivine structure, for example LFP or LMFP. The material of the shell 13 is an olivine compound, preferably comprising an exclusively iron- and/or manganese-containing olivine (e.g., Li.sub.xFePO.sub.4 or Li.sub.xFe.sub.yMn.sub.1-yPO.sub.4 with 0≤x≤1 and 0≤y≤1). The material of the core 12 and/or the material of the shell 13 is at least partly delithiated.

[0041] The production of a lithium ion battery 10 with the active core-shell cathode material and an active anode material is elucidated hereinafter with reference to a reference example that does not have all the features of the invention, and with reference to a working example of the invention.

[0042] Table 1 lists the substances and materials used in the examples.

TABLE-US-00001 TABLE 1 Substances and materials used. Description NMC811 LiNi.sub.0.8Mn.sub.0.1Co.sub.0.1O.sub.2 Core material of the active cathode material FePO.sub.4 Iron phosphate having olivine structure, shell material of the active cathode material PVdF Polyvinylidene fluoride, binder NMP (electronic grade) N-Methyl-2-pyrrolidone, carrier solvent Aluminum carrier foil Carrier foil for cathode Natural graphite Active anode material SBR Styrene-butadiene rubber, binder CMC Carboxymethylcellulose, binder Super C65 (conductive Conductivity additive carbon black) Copper carrier foil Carrier foil for anode Celgard 2500 separator Separator (25 μm) of polypropylene (PP) Liquid electrolyte, Liquid electrolyte comprising comprising a solution of conductive lithium salt LiPF.sub.6 in organic carbonates (e.g. ethylene carbonate (EC), diethylene carbonate (DDC)) Aluminum composite foil Packaging foil for the cell

Example 1 (Reference Example)

[0043] A blend of 94% by weight of NMC811, 3% by weight of PVdF, and 3% by weight of conductive carbon black is suspended in NMP at 20° C. with a dissolver-mixer at high shear. This affords a homogeneous coating composition, which is knife-coated onto an aluminum carrier foil that has been rolled to 15 μm. Drawing off the NMP affords a composite cathode film having a weight per unit area of 21.3 mg/cm.sup.2.

[0044] Analogously, an anode coating composition having a composition of 94% by weight of natural graphite, 2% by weight SBR, 2% by weight of CMC and 2% by weight of Super C65 is produced and applied to a 10 μm rolled copper carrier foil. The anode film thus produced has a weight per unit area of 12.7 mg/cm.sup.2.

[0045] The cathode 2 with the cathode film, using an anode 5 with the anode film, a separator 4 (25 μm) of polypropylene (PP) and a liquid electrolyte 3 in the form of a 1 M solution of LiPF.sub.6 in EC/DMC (3:7 w/w), is used to build a lithium ion battery 10 with active electrode area 25 cm.sup.2, which is packed in highly processed aluminum composite foil (thickness 0.12 mm) and sealed. The result is a pouch cell having external dimensions of about 0.5 mm×6.4 mm×4.3 mm.

[0046] The lithium ion battery 10 is charged for the first time to 4.2 V (C/10) and then discharged at C/10 to 2.8 V. The capacity in the first charge is 111 mAh, and the capacity in the first discharge is 100 mAh. This results in a formation loss of about 10% for the complete lithium ion battery 10. This corresponds to an expected formation loss of about 10% when graphite is used as active anode material.

Example 2 (Lithium Ion Battery in a Working Example of the Invention)

[0047] A blend of 94% by weight of the disclosed active cathode material (consisting of an FePO.sub.4 shell comprising ˜5% by weight and an NMC811 core comprising 95% by weight), 3% by weight of PVdF, and 3% by weight of conductive carbon black is suspended in NMP at 20° C. with a mixing apparatus at high shear. The diameter of the core 12 of the particles 11 is about 5 μm, and the thickness of the shell 13 is about 0.06 μm. This affords a homogeneous coating composition, which is knife-coated onto an aluminum collector-carrier foil that has been rolled to 15 μm. Drawing off the NMP affords a composite cathode film having a weight per unit area of 22.4 mg/cm.sup.2.

[0048] Alternatively, the active cathode material of the disclosure can be used to perform the electrode production in an aqueous medium with aqueous binders: a blend of 94% by weight of the inventive active cathode material (consisting of an FePO.sub.4 shell comprising ˜5% by weight and an NMC811 core comprising 95% by weight), 2% by weight of SPR, 1% by weight of CMC and 3% by weight of conductive carbon black is suspended in demineralized water at 20° C. with a mixing apparatus at high shear. The diameter of the core 12 of the particles 11 is about 5 μm, and the thickness of the shell is about 0.06 μm. This affords a homogeneous coating composition, which is knife-coated onto an aluminum collector-carrier foil that has been rolled to 15 μm. Drawing off the demineralized water affords a composite cathode film having a weight per unit area of 22.4 mg/cm.sup.2.

[0049] Analogously, an anode coating composition having a composition of 94% by weight of natural graphite, 2% by weight of SPR, 2% by weight of CMC and 2% by weight of Super C65 is produced and applied to a 10 μm rolled copper carrier foil. The anode film thus produced has a weight per unit area of 12.7 mg/cm.sup.2.

[0050] The cathode 2 with the cathode film, using an anode 5 with the anode film, a separator 4 (25 μm) and a liquid electrolyte 3 in the form of a 1 M solution of LiPF.sub.6 in EC/DMC (3:7 w/w), is used to build a lithium ion battery 10 with active electrode area 25 cm.sup.2, which is packed in aluminum composite foil (thickness 0.12 mm) and sealed. The result is a pouch cell having external dimensions of about 0.5 mm×6.4 mm×4.3 mm.

[0051] The lithium ion battery 10 is charged for the first time to 4.2 V (C/10) and then discharged at C/10 to 2.8 V. The capacity in the first charge is 111 mAh, and the capacity in the first C/10 discharge is 104.5 mAh.

Comparison of the Examples

[0052] The use of the active core-shell cathode material (example 2) in the cathode 2 leads to a higher nominal capacity of lithium ion battery 10 with respect to the reference example. The increase in weight per unit area of the cathode film in example 2 by comparison with the reference example (22.4 mg/cm.sup.2 rather than 21.3 mg/cm.sup.2) results from the FePO.sub.4 particle shell 13; the proportion of cobalt and nickel, which are costly and available in finite volumes, is the same in the two examples. Alternatively, it may also be possible to keep the nominal capacity constant for the disclosed lithium ion battery 10, and instead to reduce the proportion of cobalt and nickel.

[0053] The lithium ion battery 10 is not limited to graphite as active anode material; it is advantageously also possible to use silicon-based active anode materials or other active anode materials.

[0054] Although the invention has been illustrated and described in detail with reference to working examples, the invention is not limited by the working examples. Instead, the person skilled in the art is able to derive other variations of the invention without leaving the scope of protection of the invention as defined by the claims.

LIST OF REFERENCE NUMERALS

[0055] 1 current collector [0056] 2 cathode [0057] 3 electrolyte [0058] 4 separator [0059] 5 anode [0060] 6 current collector [0061] 10 lithium ion battery [0062] 11 particle [0063] 12 core [0064] 13 shell