PROCESS FOR MAKING AN ELECTRODE ACTIVE MATERIAL, AND ELECTRODE ACTIVE MATERIAL

Abstract

Process for making an electrode active material wherein said process comprises the following steps: (a) Providing a hydroxide TM(OH).sub.2 or at least one oxide TMO or oxyhydroxide of TM or combination of at least two of the foregoing wherein TM contains at least 99 mol-% Ni and, optionally, in total up to 1 mol-% of at least one metal selected from Ti, Zr, V, Co, Zn, Ba, or Mg, (b) mixing said hydroxide TM(OH).sub.2 or oxide TMO or oxyhydroxide of TM or combination with a source of lithium and an aqueous solution of a compound of Me wherein Me is selected from Al or Ga or a combination of the foregoing and wherein the molar amount of TM corresponds to the sum of Li and Me, (c) removing the water by evaporation, (d) treating the solid residue obtained from step (c) thermally at a temperature in the range of from 500 to 800° C. in the presence of oxygen.

Claims

1-13. (canceled)

14. A process for making an electrode active material comprising: (a) providing a hydroxide TM(OH).sub.2 or at least one oxide TMO or at least one oxyhydroxide of TM or a combination of at least two of the foregoing, wherein TM contains at least 99 mol-% Ni and, optionally, in total up to 1 mol-% of at least one metal selected from Ti, Zr, V, Co, Zn, Ba, or Mg, (b) mixing the hydroxide TM(OH).sub.2 or oxide TMO or oxyhydroxide of TM or combination with a source of lithium, and an aqueous solution of a compound of Me, wherein Me is selected from Al or Ga or a combination of the foregoing and wherein the molar amount of TM corresponds to the sum of Li and Me, (c) removing water by evaporation, and (d) treating the solid residue obtained from step (c) thermally at a temperature ranging from 500 C to 800° C. in the presence of oxygen.

15. The process according to claim 14, wherein step (c) is performed at a temperature ranging from 150° C. to 500° C.

16. The process according to claim 14, wherein in step (b), the compound(s) of Me are nitrate(s).

17. The process according claim 14, wherein step (b) comprises sub-steps (b1) of mixing TM(OH).sub.2 or oxide TMO or oxyhydroxide of TM or combination of at least two of the foregoing with a source of lithium followed by sub-step (b2) adding a solution of compound of Me.

18. The process according to claim 14, wherein a molar amount x of Me corresponds to 0.00<x≤0.05 and an amount of Li corresponds to 1−x.

19. The process according to claim 14, wherein Me is gallium.

20. A particulate electrode active material according to general formula Li.sub.1−xTMMe.sub.xO.sub.2, wherein TM contains at least 99 mol-% Ni and, optionally, up to 1 mol-% of at least one metal selected from Ti, Zr, V, Co, Zn, Ba, or Mg, Me is selected from Ga and Al and combinations of the foregoing, 0.00<x≤0.05.

21. The particulate electrode active material according to claim 20, wherein TM is nickel.

22. The particulate electrode active material according to claim 20, wherein Me is Ga.

23. The particulate electrode active material according claim 20, wherein an average particle diameter ranges from 3 μm to 20 μm.

24. A cathode comprising (A) at least one electrode active material according to claim 20, (B) carbon in electrically conductive form, and (C) a binder material.

25. The cathode according to claim 24, wherein (A) 80% to 98% by weight cathode active material, (B) 1% to 17% by weight of carbon, (C) 3% to 10% by weight of binder material, and wherein percentages refer to a sum of (A), (B) and (C).

26. An electrochemical cell comprising at least one cathode according to claim 24.

Description

[0101] Examples of suitable acyclic ethers are, for example, diisopropyl ether, di-n-butyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, with preference being given to 1,2-dimethoxyethane.

[0102] Examples of suitable cyclic ethers are tetrahydrofuran and 1,4-dioxane.

[0103] Examples of suitable acyclic acetals are, for example, dimethoxymethane, diethoxymethane, 1,1-dimethoxyethane and 1,1-diethoxyethane.

[0104] Examples of suitable cyclic acetals are 1,3-dioxane and in particular 1,3-dioxolane.

[0105] Examples of suitable acyclic organic carbonates are dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate.

[0106] Examples of suitable cyclic organic carbonates are compounds according to the general formulae (II) and (III)

##STR00001##

[0107] where R.sup.1, R.sup.2 and R.sup.3 can be identical or different and are selected from among hydrogen and C.sub.1-C.sub.4-alkyl, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl, with R.sup.2 and R.sup.3 preferably not both being tert-butyl.

[0108] In particularly preferred embodiments, R.sup.1 is methyl and R.sup.2 and R.sup.3 are each hydrogen, or R.sup.1, R.sup.2 and R.sup.3 are each hydrogen.

[0109] Another preferred cyclic organic carbonate is vinylene carbonate, formula (IV).

##STR00002##

[0110] The solvent or solvents is/are preferably used in the water-free state, i.e. with a water content in the range from 1 ppm to 0.1% by weight, which can be determined, for example, by Karl-Fischer titration.

[0111] Electrolyte (C) further comprises at least one electrolyte salt. Suitable electrolyte salts are, in particular, lithium salts. Examples of suitable lithium salts are LiPF.sub.6, LiBF.sub.4, LiClO.sub.4, LiAsF.sub.6, LiCF3SO3, LiC(C.sub.nF.sub.2n+1SO.sub.2).sub.3, lithium imides such as LiN(C.sub.nF.sub.2n+1SO.sub.2).sub.2, where n is an integer in the range of from 1 to 20, LiN(SO.sub.2F).sub.2, Li.sub.2SiF.sub.6, LiSbF.sub.6, LiAlCl.sub.4 and salts of the general formula (C.sub.nF.sub.2n+1SO.sub.2).sub.tYLi, where m is defined as follows:

[0112] t=1, when Y is selected from among oxygen and sulfur,

[0113] t=2, when Y is selected from among nitrogen and phosphorus, and

[0114] t=3, when Y is selected from among carbon and silicon.

[0115] Preferred electrolyte salts are selected from among LiC(CF.sub.3SO.sub.2).sub.3, LiN(CF.sub.3SO.sub.2).sub.2, LiPF.sub.6, LiBF.sub.4, LiClO.sub.4, with particular preference being given to LiPF.sub.6 and LiN(CF.sub.3SO.sub.2).sub.2.

[0116] In an embodiment of the present invention, batteries according to the invention comprise one or more separators by means of which the electrodes are mechanically separated. Suitable separators are polymer films, in particular porous polymer films, which are unreactive toward metallic lithium. Particularly suitable materials for separators are polyolefins, in particular film-forming porous polyethylene and film-forming porous polypropylene.

[0117] Separators composed of polyolefin, in particular polyethylene or polypropylene, can have a porosity in the range from 35 to 45%. Suitable pore diameters are, for example, in the range from 30 to 500 nm.

[0118] In another embodiment of the present invention, separators can be selected from among PET nonwovens filled with inorganic particles. Such separators can have porosities in the range from 40 to 55%. Suitable pore diameters are, for example, in the range from 80 to 750 nm.

[0119] Batteries according to the invention further comprise a housing which can have any shape, for example, cuboidal or the shape of a cylindrical disk or a cylindrical can. In one variant, a metal foil configured as a pouch is used as housing.

[0120] Batteries according to the invention display a good discharge behavior, for example at low temperatures (zero ° C. or below, for example down to −10° C. or even less), a very good discharge and cycling behavior.

[0121] Batteries according to the invention can comprise two or more electrochemical cells that combined with one another, for example can be connected in series or connected in parallel. Connection in series is preferred. In batteries according to the present invention, at least one of the electrochemical cells contains at least one cathode according to the invention. Preferably, in electrochemical cells according to the present invention, the majority of the electrochemical cells contains a cathode according to the present invention. Even more preferably, in batteries according to the present invention all the electrochemical cells contain cathodes according to the present invention.

[0122] The present invention further provides for the use of batteries according to the invention in appliances, in particular in mobile appliances. Examples of mobile appliances are vehicles, for example automobiles, bicycles, aircraft or water vehicles such as boats or ships. Other examples of mobile appliances are those which move manually, for example computers, especially laptops, telephones or electric hand tools, for example in the building sector, especially drills, battery-powered screwdrivers or battery-powered staplers.

[0123] The present invention is further illustrated by the following working examples.

[0124] General remarks: N-methyl-2-pyrrolidone: NMP.

[0125] I. Synthesis of a cathode active material

[0126] I.1 Step (a.1): Synthesis of a precursor Ni(OH).sub.2

[0127] Precipitation of nickel hydroxide (precursor):

[0128] Precipitation of nickel hydroxide was performed at 55° C. under a nitrogen atmosphere using a continuously stirred tank reactor with a volume of 2.3 I Aqueous solutions of nickel sulfate, ammonia and sodium hydroxide were fed into the reactor. The individual flow rates were adjusted to ensure a pH value of 12.6 (plus/minus 0.2), a molar ratio of nickel to ammonia of 0.8 and a residence time of around 8 hours. The solid so obtained was removed by filtration, washed with deionized water for 12 hours and dried at 120° C. for 16 hours. Nickel hydroxide powder, Ni(OH).sub.2 was obtained, with an average secondary particle diameter (D50) of 15 μm.

[0129] I.2 Conversion of Ni(OH).sub.2 into cathode active materials

[0130] I.2.1 Step (b.1), general procedure

[0131] Ni(OH).sub.2 from step (a.1) and LiOH.Math.H.sub.2O were mixed in a mixer for 3 minutes in a molar ratio of 1.0:0.96. An aqueous solution of the Ga precursor (Ga(NO.sub.3).sub.3.Math.nH.sub.2O) was made and added to the mixture of Ni and Li hydroxides (typically 2.5 ml deionized water per 10 g total precursor mass). The amount of Ga was chosen to be in a molar ratio of x to 1.0, referring to Ni. In the case of step (b.1), x was set to 0.01. The resulting suspension was stirred for one minute using a spatula.

[0132] I.2.2 Steps (c.1) to (d.1)

[0133] In steps (b.1) and (c.1), both the heating and the cooling rate were set to 3° C./min.

[0134] Step (c.1): The suspension from step (b.1) was heated to 300° C. and then maintained at 300° C. for 15 hours. Step (c.1) was conducted in argon flow (4 exchanges of the reactor atmosphere per hour). The residue was cooled to ambient temperature and homogenized in a mortar.

[0135] Step (d.1): The homogenized residue from step (c.1) was subjected to calcination in O.sub.2 flow (4 exchanges of the reactor atmosphere per hour) at 700° C. for 10 hours. Inventive CAM.1 was obtained.

[0136] In the case of comparative material C-CAM.0, no gallium nitrate was added.

[0137] II. Testing of Cathode Active Material

[0138] II.1 Electrode manufacture, general procedure

[0139] Positive electrode: PVDF binder (Solef® 5130) was dissolved in NMP (Merck) to produce a 7.5 wt. % solution. For electrode preparation, binder solution (3 wt. %) and carbon black (Super C65, 3 wt.-%) were suspended in NMP. After mixing using a planetary centrifugal mixer (ARE-250, Thinky Corp.; Japan), inventive CAM (or comparative CAM) (94 wt. %) was added and the suspension was mixed again to obtain a lump-free slurry. The solid content of the slurry was adjusted to 61%. The slurry was coated onto Al foil using a KTF-S roll-to-roll coater (Mathis AG). Prior to use, all electrodes were calendared. The thickness of cathode material was 100 μm, corresponding to 6.5 mg/cm.sup.2. All electrodes were dried at 105° C. for 7 hours before battery assembly.

[0140] II.2 Electrolyte Manufacture

[0141] A base electrolyte composition was prepared containing 1 M LiPF.sub.6 in 3:7 by weight ethylene carbonate and ethyl methyl carbonate (EL base 1).

[0142] II.3 Test cell Manufacture

[0143] Coin-type half cells (20 mm in diameter and 3.2 mm in thickness) comprising a cathode prepared as described under II.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, 0.15 ml of EL base 1, which is described above (II.2), were introduced into the coin cell.

[0144] III. Evaluation of cell performance

[0145] Evaluation of coin half-cell performance

[0146] Cell performance were evaluated using the produced coin type battery. For the battery performances, initial capacity and reaction resistance of cell were measured.

[0147] Cycling data were recorded at 25° C. using a MACCOR Inc. battery cycler. For ten initial cycles, cells were galvanostatically charged to 4.3 V vs Li.sup.+/Li, followed by 15 min of potentiostatic charging (or a shorter period if the charging current dropped below C/20), and discharged to 3.0 V vs Li.sup.+/Li at a rate of C/10 (1C=225 mA/g.sub.CAM). For 100 additional cycles the charging and discharging rates were set to C/4 and C/2, respectively, and the length of the potentiostatic step at 4.3 V vs Li.sup.+/Li was set to 10 min. The results are summarized in Table 1.

TABLE-US-00001 TABLE 1 Discharge Capacities (DC) for different cycle numbers Cap. Ret. 1.sup.st Max. 10.sup.th 11.sup.th 110.sup.th 11.sup.th-110.sup.th CAM x cyc. DC DC cyc. DC cyc. DC cyc. DC cyc. [%] C- 0.00 233.0 233.0 215.2 188.1 84.1 44.7 CAM. 0 CAM. 1 0.01 225.5 225.5 204.0 175.2 80.4 45.9 CAM. 2 0.02 224.2 224.8 211.8 190.3 131.3 69.0 CAM. 3 0.03 224.2 221.7 210.9 189.4 134.0 70.7 CAM. 4 0.04 203.7 216.0 209.6 188.7 147.9 78.4 CAM. 5 0.05 190.0 208.9 204.8 183.4 139.1 75.8

[0148] 10 cycles at C/10; afterwards charging at C/4 and discharging at C/2. Max. DC refers to the highest recorded discharge capacity. The percentages denoting the samples refer to the nominal degree of Li substitution by Ga (Me), i.e. x from 0.00 to 0.05 in Li.sub.1−xNiGa.sub.xO.sub.2 refers to 0 to 5% nominal doping. All values in mA.Math.h/g unless specifically noted otherwise.