ELECTRODE ACTIVE MATERIAL AND PREPARATION METHOD THEREOF, ELECTRODE, BATTERY, AND APPARATUS

Abstract

The present invention relates to an electrode active material, a preparation method thereof, an electrode, a battery, and an apparatus. The electrode active material includes: a core and a coating layer, where the core includes a ternary material, the coating layer coats the core, the coating layer includes a reaction product of a sulfur-containing compound and a lithium-containing compound, and the reaction product includes element Li, element S, and element O.

Claims

1. An electrode active material with a coating layer, comprising: a core, comprising a ternary material; and a coating layer, wherein the coating layer coats at least part of a surface of the core, the coating layer comprises a reaction product of a sulfur-containing compound and a lithium-containing compound, and the reaction product comprises element Li, an element S, and element O.

2. The electrode active material according to claim 1, wherein a weight content of element S in the electrode active material is 500-5000 ppm.

3. The electrode active material according to claim 1, wherein the coating layer further comprises one or more of element B, element P, and element F; under a condition that element B is comprised in the coating layer, a weight content of element B in the electrode active material is 500-3000 ppm; under a condition that element P is comprised in the coating layer, a weight content of element P in the electrode active material is 200-1500 ppm; and under a condition that element F is comprised in the coating layer, a weight content of element F in the electrode active material is 500-3000 ppm;

4. The electrode active material according to claim 1, wherein the lithium-containing compound comprises a lithium salt; and the lithium-containing compound comprises one or more of the following: Li.sub.2O, LiOH and Li.sub.2CO.sub.3, LiNO.sub.3, LiPF.sub.6, lithium oxalate, lithium acetate, LiClO.sub.4, LiBF.sub.4, LiCF.sub.3SO.sub.3, LiAsF.sub.6, LiAlCl.sub.4, LiN(CF.sub.3SO.sub.2).sub.2 and LiC(SO.sub.2CF.sub.3).sub.3.

5. The electrode active material according to claim 1, wherein the sulfur-containing compound comprises one or more of the following: mercaptan, thiophenol, thioether, thioaldehyde, thioketone, thiocarboxylic acid, sulfoxide, sulfone, sulfur oxoacid, and derivatives thereof; the sulfur oxoacid is sulfonic acid, sulfinic acid, or sulfenic acid; and derivatives of the sulfur oxoacid comprise one or more of the following: an ester of the sulfur oxoacid, a salt of the sulfur oxoacid (optionally, a lithium salt of the sulfur oxoacid), an acyl halide of the sulfur oxoacid, an amide of the sulfur oxoacid, and a lithium amide salt of the sulfur oxoacid.

6. The electrode active material according to claim 1, wherein the sulfur-containing compound comprises one or more of the following: R1-S(═O).sub.2—R2, R1-C(═S)—R2, R1-C—S—C—R2, or R1-S(═O).sub.2—LiN—S(═O).sub.2—R2, wherein R1 and R2 each are selected from hydroxyl, amino, C.sub.1-6 alkyl, aryl, a halogen atom selected from the group consisting of F, Cl, Br, and I, and a hydrogen atom; the sulfur-containing compound comprises R1-S(═O).sub.2—R2, wherein R1 is hydroxyl, and R2 is selected from amino, C.sub.1-6 alkyl, and the halogen atom; the sulfur-containing compound comprises R1-C(═S)—R2, wherein R1 is amino, and R2 is C.sub.1-6 alkyl; the sulfur-containing compound comprises ##STR00005## wherein R1 and R2 each are a hydrogen atom or C.sub.1-6 alkyl; the sulfur-containing compound comprises R1-C—S—C—R2, wherein R1 and R2 each are a hydrogen atom or C.sub.1-6 alkyl; and the sulfur-containing compound comprises R1-S(═O).sub.2—LiN—S(═O).sub.2—R2, wherein R1 and R2 each are a halogen atom.

7. The electrode active material according to claim 1, wherein the sulfur-containing compound comprises one or more of the following: sulfamide, aminomethanesulfonic acid, lithium bisfluorosulfonimide, thio-propionamide, thio-isobutyramide, propylene sulfide, and methyl ethyl sulfide.

8. The electrode active material according to claim 1, wherein the ternary material comprises one or more of the following: lithium nickel cobalt manganese oxides and lithium nickel cobalt aluminum oxides; a chemical formula of the lithium nickel cobalt manganese oxides is Li.sub.xNi.sub.aCo.sub.bMn.sub.cM.sup.1.sub.(1-a-b-c)O.sub.2, wherein 0.5≤x≤1.2, 0.3≤a≤1, 0≤b≤0.5, 0≤c≤0.6, and M.sup.1 is selected from a combination of one or more of Zr, Zn, Ti, Sr, Sb, Y, W, Al, B, P, and F; and a chemical formula of the lithium nickel cobalt aluminum oxides is Li.sub.xNi.sub.dCo.sub.eAl.sub.fM.sup.2.sub.(1-d-e-f)O.sub.2, wherein 0.5≤x≤1.2, 0.5≤d≤1, 0≤e≤0.5, 0≤f≤0.5, and M.sup.2 is selected from a combination of one or more of Zr, Mg, Ba, Ti, Sr, Sb, Y, W, and B.

9. The electrode active material according to claim 1, wherein a particle size (D.sub.v50 particle size) of the electrode active material is 1-25 μm.

10. A preparation method of an electrode active material with a coating layer, comprising: (a) providing a core material and a coating layer forming material, wherein the core material comprises a ternary material, and the coating layer forming material comprises a sulfur-containing compound; wherein, step (a) comprises one or more characteristics of the following (a1) and (a2): (a1) a surface of the core material comprises a lithium-containing compound; and (a2) the coating layer forming material further comprises a lithium-containing compound; and (b) processing the core material by using the coating layer forming material, so that a reaction product of the sulfur-containing compound and the lithium-containing compound is formed on the surface of the core material, and the reaction product comprises element Li, element S, and element O.

11. The preparation method according to claim 10, wherein, in (a1), the lithium-containing compound is an alkaline lithium-containing compound.

12. The preparation method according to claim 10, wherein, in (a2), the lithium-containing compound is a neutral lithium-containing compound or an acidic lithium-containing compound.

13. The preparation method according to claim 10, wherein the coating layer forming material further comprises one or more of element B, element P, and element F; under a condition that element B is comprised in the coating layer, a molar ratio of element B to element S in the coating layer forming material is 2-5:4-7; under a condition that element P is comprised in the coating layer, a molar ratio of element P to element S in the coating layer forming material is 1-3:4-6; and under a condition that element F is comprised in the coating layer, a molar ratio of element F to element S in the coating layer forming material is 10-15:4-6;

14. The preparation method according to claim 10, wherein the processing the core material by using the coating layer forming material comprises: applying a solution containing the coating layer forming material to the surface of the core material, and performing heat treatment; wherein a heat treatment temperature is 80-300° C.; and a heat treatment time is 3-20 hours.

15. The preparation method according to claim 10, comprising one or more of the following characteristics: in the solution containing the coating layer forming material, a concentration of the sulfur-containing compound is 0.1-5 mol/L (optionally, 0.2-2 mol/L); in the solution containing the coating layer forming material, a concentration of the lithium-containing compound is 0.1-3 mol/L (optionally, 0.3-0.5 mol/L); and in the solution containing the coating layer forming material, a solvent comprises one or more of the following substances: water, ethanol, and NMP, and the solvent is alcohol with a concentration of 90-95 vol %.

16. The preparation method according to claim 10, comprising one or more of the following characteristics: a definition of the lithium-containing compound is as defined according to claim 4; the lithium-containing compound is as defined according to claim 5; and the ternary material is as defined according to claim 8.

17. An electrode active material with a coating layer, obtained by the preparation method according to claim 10.

18. An electrode, comprising the electrode active material according to claim 1.

19. A battery, comprising the electrode active material according to claim 1.

20. An apparatus, comprising the battery according to claim 19, wherein the battery is used as a power supply unit or an energy storage unit of the apparatus; and the apparatus is an electric apparatus, and the battery is configured to power the electric apparatus.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0129] FIG. 1 shows scanning electron microscope images of a lithium nickel cobalt manganese oxide numbered 10, with (a)-(d) showing images at different magnifications or positions.

[0130] FIG. 2 shows scanning electron microscope images of a lithium nickel cobalt manganese oxide numbered 24, with (a)-(d) showing images at different magnifications or positions.

[0131] FIG. 3 is a schematic diagram of a battery according to an embodiment of this application.

[0132] FIG. 4A is a schematic diagram of a housing of a battery, and FIG. 4B is a schematic diagram of the housing and a cover plate of the battery.

[0133] FIG. 5A and FIG. 5B respectively show a side view and a bottom view of a vehicle according to an embodiment of this application.

DESCRIPTION OF EMBODIMENTS

[0134] The following embodiments specifically describe an electrode active material with a coating layer and a preparation method thereof. A battery is assembled by using the electrode active material, and tested for one or more of the following performance: capacity retention rate, direct current resistance, gas production, and slurry processing performance.

[0135] The following embodiments describe in more detail content disclosed in this application. These embodiments are intended only for illustrative purposes because various modifications and changes made without departing from the scope of the content disclosed in this application are apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weights, all reagents used in the embodiments are commercially available or synthesized in a conventional manner, and can be used directly without further processing, and all instruments used in the embodiments are commercially available.

[0136] 1. Electrode Active Material Powder (Core Material)

[0137] The electrode active material powder as a core material is a commercially available ternary material, specifically, NCMs 1-4 are lithium nickel cobalt manganese oxides and NCA is a lithium nickel cobalt aluminum oxide. Due to a preparation process, residual lithium is present on a surface of the core material. Relevant parameters of the core material are shown in the following table:

TABLE-US-00001 Residual Chemical Morphological lithium No. formula feature D.sub.V10 D.sub.v50 D.sub.V90 content* NCM1 LiNi.sub.0.82Co.sub.0.118Mn.sub.0.058Zr.sub.0.004O.sub.2 Single crystal 1.8 3.6 7.2 0.21% NCM2 LiNi.sub.0.644Co.sub.0.098Mn.sub.0.252Ti.sub.0.006O.sub.2 Single crystal 1.54 3.23 6.6 0.08% NCM3 LiNi.sub.0.548Co.sub.0.05Mn.sub.0.40Sr.sub.0.002O.sub.2 Single crystal 1.81 3.76 7.44 0.06% NCM4 LiNi.sub.0.818Co.sub.0.119Mn.sub.0.059Zr.sub.0.002Sr.sub.0.002O.sub.2 Polycrystal 5.39 10 17.4 0.26% NCA LiNi.sub.0.83Co.sub.0.10Al.sub.0.065Ba.sub.0.005O.sub.2 Polycrystal 5.21 9.53 16.2 0.31% *A method for determining residual lithium content is as follows: Reference standard: GB/T 9725-2007 Chemical reagent—general rule for potentiometric titration

[0138] Device parameters: 905 Ttrando potentiometric titrator; electrode: composite pH electrode; reagent: 0.5 mol/L of HCl solution; environmental parameters: 15-28° C., ambient humidity less than or equal to 80%

[0139] Test method: 30 g of a sample is weighted, mixed and stirred with 100 g of deionized water, and left standing; upon suction filtration, a filtrate was subjected to potentiometric titration with 0.5 mol/L of HCL solution by using the 905 Ttrando potentiometric titrator, and contents of CO.sub.3.sup.2− and OH.sup.− in the filtrate were determined; and conversions were performed according to a stoichiometric ratio of Li.sub.2CO.sub.3 and LiOH, with 1 mol of CO.sub.3.sup.2− corresponding to 2 mol of element Li, and 1 mol of OH.sup.− corresponding to 1 mol of element Li, and a residual lithium weight content based on element Li was obtained after summation.

[0140] 2. Coating Method

[0141] Step 1: providing the ternary material as a core material.

[0142] Step 2: providing a solution containing a coating layer formation material, where a formula of the solution containing the coating layer formation material is shown in Table 1.

[0143] Step 3: mixing the products in step 1 and step 2 at a weight ratio of 1:1, stirring for 30 minutes after the mixing, and upon solid-liquid separation, collecting solids.

[0144] Step 4: performing heat treatment to the solids obtained in the previous step in an inert atmosphere in a closed environment to obtain an electrode active material with a coating layer, with heat treatment conditions shown in Table 1.

[0145] In the foregoing example, an alkaline lithium-containing compound (such as Li.sub.2O, LiOH, and Li.sub.2CO.sub.3) was present on the surface of the core material, and the alkaline lithium-containing compound reacted with a sulfur-containing compound during a coating process, producing a reaction product of the sulfur-containing compound and the lithium-containing compound, where the reaction product included element Li, element S, and element O.

[0146] After the coating treatment was performed on the core material based on the foregoing method, an electrode active material with a coating layer was obtained. Specific process parameters are shown in Table 1.

TABLE-US-00002 TABLE 1 Raw material Heat Core Solution containing a coating layer formation material treatment material Lithium- Parameter Chemical Sulfur-containing Concentration containing Concentration Another Concentration Temperature Time formula Solvent compound (mol/L) compound (mol/L) compound (mol/L) (° C.) (h) 1 NCM1 95% Sulfamide 0.5 N/A / N/A / 175 8 ethanol 2 NCM2 95% Aminomethanesulfonic 0.4 N/A / N/A / 245 8 ethanol acid 3 NCM3 Deionized lithium 5 N/A / N/A / 265 8 water bisfluorosulfonimide 4 NCM1 95% Sulfamide 0.2 LiNO.sub.3 0.5 N/A / 245 8 ethanol 5 NCM1 95% Sulfamide 0.8 Li.sub.2C.sub.2O.sub.4 0.3 N/A / 245 8 ethanol 6 NCM1 95% Sulfamide 2.0 LiC.sub.2H.sub.3O.sub.2 0.3 N/A / 175 8 ethanol 7 NCM1 Deionized Sulfamide 0.7 N/A / H.sub.3BO.sub.3 0.5 150 20 water 8 NCM1 95% Sulfamide 0.5 N/A / Li.sub.3PO.sub.4 0.2 225 8 ethanol 9 NCM1 95% Sulfamide 0.5 N/A / LiPF.sub.6 0.2 270 8 ethanol 10 NCM1 95% Sulfamide 0.5 N/A / LiPF.sub.6 + 0.2 + 300 8 ethanol H.sub.3BO.sub.3 0.2 11 NCM1 / / / / / / / / / 12 NCM2 / / / / / / / / / 13 NCM3 / / / / / / / / / 14 NCA 95% Sulfamide 0.5 N/A N/A / 245 8 ethanol 15 NCA 95% Sulfamide 0.5 LiNO.sub.3 0.5 N/A / 245 12 ethanol 16 NCA 95% Aminomethanesulfonic 0.4 Li.sub.2C.sub.2O.sub.4 0.3 N/A / 245 6 ethanol acid 17 NCA 95% lithium 0.3 LiC.sub.2H.sub.3O.sub.2 0.3 N/A / 245 4 ethanol bisfluorosulfonimide 18 NCA / / / / / / / / / 19 NCM4 95% Sulfamide 0.5 N/A N/A / 200 8 ethanol 20 NCM4 95% Sulfamide 0.5 LiNO.sub.3 0.5 N/A / 80 16 ethanol 21 NCM4 NMP lithium 0.4 Li.sub.2C.sub.2O.sub.4 0.3 N/A / 300 3 bisfluorosulfonimide 22 NCM4 95% Aminomethanesulfonic 0.4 LiC.sub.2H.sub.3O.sub.2 0.3 N/A / 200 8 ethanol acid 23 NCM4 95% Aminomethanesulfonic 0.4 LiC.sub.2H.sub.3O.sub.2 0.5 N/A / 200 8 ethanol acid 24 NCM4 / / / / / / / / / Li.sub.2C.sub.2O.sub.4 is lithium oxalate with a CAS number of 533-91-3. LiC.sub.2H.sub.3O.sub.2 is lithium acetate with a CAS number of 6108-17-4. 95% alcohol is an aqueous solution of ethanol with a concentration of 95 vol %. Deionized water refers to deionized water with conductivity less than or equal to 0.5 μs/cm. NMP refers to an aqueous solution of N-methylpyrrolidone with a concentration of 99% or more.

[0147] Material Physical Performance and Electrical Performance Test

[0148] 24 samples are shown in Table 1, including coated and uncoated electrode active materials. These 24 samples are tested by using the following test methods.

[0149] I. Preparation of a Battery

[0150] Preparation of a positive-electrode plate: At 2% environmental humidity, the electrode active material prepared in the foregoing examples/comparative examples was mixed with conductive carbon black and a binder PVDF at a mass ratio of 96:2.5:1.5. A solvent N-methylpyrrolidone (NMP) was added, with a mass of the solvent accounting for 30% of a total weight of a slurry, to produce a uniform positive-electrode slurry after stirring. The positive-electrode slurry was evenly applied on both sides of a positive-electrode collector aluminum foil, the aluminum foil was cold pressed by using a roller press to obtain a positive-electrode plate, and a press density of the obtained positive-electrode plate was 3.5-4.0 g/cc.

[0151] Preparation of a negative-electrode plate: Artificial graphite was used as a negative-electrode active substance. In a negative-electrode slurry, solid components were formed by the artificial graphite, styrene polybutadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), and conductive carbon black at a ratio of 96:2:1:1. A solvent of the slurry was water, and the solvent accounted for 50% of weight of the slurry. The negative-electrode slurry was evenly applied on both sides of a negative-electrode current collector copper foil, the copper foil was cold pressed by using a roller press to obtain a negative-electrode plate, and a press density of the negative-electrode plate was 1.65 g/cc.

[0152] Separator: A PP/PE composite separator was used.

[0153] Electrolyte: 1 mol/L of LiPF.sub.6 solution was selected. Its solvent mainly includes ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC).

[0154] Assembly of a battery: The negative-electrode plate, the separator, and the positive-electrode plate were stacked and then wound. After a roll core was obtained, a tab was welded on the copper and aluminum foil current collectors of the positive-electrode plate and the negative-electrode plate exposed from the core, and all are encapsulated in a packaging bag made of aluminum-plastic composite material. A thickness of the packaging bag was 153 μm. An electrolyte was injected and then the bag was sealed. Chemical conversion was performed at 45° C. After the chemical conversion, gas generated by the chemical conversion was extracted and excess packaging bags were removed to obtain a battery with a height of 130 mm, a thickness of 4 mm, and a width of 60 mm.

[0155] II. First-Cycle Discharge Specific Capacity and Testing Method

[0156] The battery was charged and discharged at a constant test room temperature (25° C.) by using a Neware charge and discharge machine (5V/6A). A charging and discharging method was as follows:

[0157] 1. The battery was left standing for 10 minutes at a constant temperature of 25° C.

[0158] 2. The battery was charged at a constant current rate of 0.33 C to a charge cut-off voltage (charge cut-off voltages of battery cells corresponding to different active materials are shown in the following table) and then charged at a constant voltage of the charge cut-off voltage until a charge current was less than or equal to 0.05 C;

TABLE-US-00003 TABLE 2 Electrode active material Charge cut-off voltage of battery cell NCM1, NCM4, NCA  4.2 V NCM2, NCM3 4.35 V

[0159] 3. The battery was left standing for 5 minutes;

[0160] 4. The battery was discharged at a constant current rate of 0.33 C to a discharge cut-off voltage (in the following examples, the discharge cut-off voltage is set to 2.8 V and may be adjusted based on different to-be-detected batteries);

[0161] A first-cycle discharge specific capacity was determined as a test result.

[0162] The charge/discharge current was a preset rate multiplied by a rated capacity of the battery cell. The rated capacity is based on a cell capacity identified in a GBT certification document for the cell, or the battery module to which the cell belongs, or the battery pack to which the cell belongs.

[0163] III. Method for Testing a Capacity Retention Rate

[0164] A high/low temperature chamber of 220L from Tengda was used for testing. A charging and discharging method is as follows:

[0165] 1. The chamber was adjusted to a preset temperature and left standing for 2 hours;

[0166] 2. The battery was charged at a constant current rate of 1 C to a charge cut-off voltage (cut-off voltages for different active materials are shown above), and then charged at a constant voltage of the charge cut-off voltage until a charge current was less than or equal to 0.05 C;

[0167] 3. The battery was left standing for 5 minutes;

[0168] 4. The battery was discharged at a constant current rate of 1 C to a discharge cut-off voltage (a discharge cut-off voltage used in the following examples is specifically 2.8 V);

[0169] 5. The battery was left standing for 5 minutes;

[0170] 6. Steps 2-5 are repeated.

[0171] IV. Method for Testing Gas Production:

[0172] After fully charged, the battery cell was stored in a high-temperature furnace at 70° C. At regular intervals, the battery cell was taken out of the furnace and a volume of the battery was measured by using a drainage method. A volume change before and after the storage was found after comparison, and a volume change rate of the gas production was obtained.

[0173] V. Method for Extracting a DCR Growth Rate During Cycling

[0174] During cycling, an average voltage/average current 30 seconds before charging to 100% SOC is extracted for each cycle to obtain a DCR at a corresponding number of cycles. After DCRs are extracted by the number of cycles, a DCR growth rate during the cycling is obtained.

[0175] VI. Method for Testing a Particle Size Distribution:

[0176] A laser particle size test was performed by using a Mastersizer 3000E laser particle size analyzer from Malvern instruments Ltd in UK. A test method can be referred to a GB/T 19077-2016 particle size distribution laser diffraction method. In the test, the electrode active material was dispersed in water to obtain a particle refractive index of 1.69.

[0177] A method for testing a particle size of electrode active material in the finished electrode is as follows: powder was scraped from the positive-electrode plate, the scraped powder was collected, put in a sintering furnace, and sintered at 600° C. for 4 hours to remove conductive carbon and binder from the powder and obtain an electrode active material. A laser particle size test was performed on the electrode active material by using a Mastersizer 3000E laser particle size analyzer.

[0178] VII. Method for Testing Contents of Element Sulfur, Element Boron, and Element Phosphorus:

[0179] Testing method: inductively coupled plasma atomic emission spectrometry

[0180] Instrument model: ICP-OES, Thermo ICAP7400

[0181] Sample weight: 0.4 g

[0182] Digestion method: plate digestion

[0183] Type and volume of acids used for digestion: 10 mL of aqua regia (concentrated nitric acid: concentrated hydrochloric acid (volume ratio)=1:1)

[0184] Constant volume: 100 mL

[0185] Quantitative method: standard curve method

[0186] VIII. Method for testing content of element fluorine:

[0187] Instrument model: ICS-900 ion chromatography instrument

[0188] Reference standard: General Rules for Ion Chromatography JY/T202-1996

[0189] Measurement method: 0.4 g of the electrode active material was completely digested in 10 mL of aqua regia (concentrated nitric acid: concentrated hydrochloric acid (volume ratio)=1:1), and an obtained solution was diluted to 250 mL for measurement.

[0190] Detailed description of test results of the electrode active material

[0191] Test results obtained by testing samples 1-24 based on the foregoing methods are described in detail below.

[0192] 1. Micro-morphology and particle size

[0193] (1) Micro-morphology

[0194] FIG. 1 shows scanning electron microscope images of an electrode active material numbered 10, with (a)-(d) sequentially showing images at scales of 10 μm, 2 μm, 1 μm, and 1 μm. Particles of the electrode active material have irregular particle shapes, with a single crystal micro-structure.

[0195] FIG. 2 shows scanning electron microscope images of an electrode active material numbered 24, with (a)-(d) sequentially showing images at different magnifications or positions. (a)-(d) sequentially show images at scales of 10 μm, 2 μm, 1 μm, and 1 μm. Particles of the electrode active material have a spherical particle shape, with a polycrystal micro-structure.

[0196] (2) Particle Size Distribution

[0197] Particle size distributions of the electrode active materials numbered 1, 2, 3, 14, and 21 are as follows:

TABLE-US-00004 TABLE 3 Sample Item 1 2 3 14 21 Dv10 1.7 1.58 1.63 5.39 5.20 D.sub.v50 3.5 3.32 3.36 9.73 9.51 Dv90 7.2 6.65 7.29 16.50 16.4

[0198] (3) Element Content Test

[0199] Contents of element S, element B, element P, and element F in the electrode active materials numbered 1-24 are as follows:

TABLE-US-00005 TABLE 4 Element S Element B Element P Element F Number (ppm) (ppm) (ppm) (ppm) 1 1600 \ \ \ 2 1060 \ \ \ 3 840 \ \ 1070 4 540 \ \ \ 5 1620 \ \ \ 6 4360 \ \ \ 7 1550 860 \ \ 8 1630 \ 690 \ 9 1490 \ 820 2100 10 1570 910 870 2060 11 260 \ \ \ 12 190 \ \ \ 13 230 \ \ \ 14 1540 \ \ \ 15 1610 \ \ \ 16 1520 \ \ \ 17 1630 \ \ 1720 18 310 \ \ \ 19 1370 \ \ \ 20 1270 \ \ \ 21 1410 \ \ 1260 22 1460 \ \ \ 23 1560 \ \ \ 24 360 \ \ \

[0200] Coating treatment is not performed on the electrode active materials numbered 11 to 13, 18, and 24. Because a raw material precursor contains elemental sulfur, the electrode active materials inevitably contain trace amounts of residual element sulfur (<400 ppm).

[0201] (4) Lithium-ion secondary batteries are assembled by using the electrode active materials numbered 1 to 24 based on the foregoing methods, and tested for performance. Results are as follows:

TABLE-US-00006 TABLE 5 Direct Capacity current Gas production First cycle retention rate* resistance* at 70° C. discharge (%) (mΩ) Volume change capacity 100 500 100 500 rate (%) Number (mAh/g) cycles cycles cycles cycles 10 days 50 days 1 197 96.2 90.1 17.7 28.7  7.38% 31.08% 2 188 96.5 90.7 17.6 18.7  0.09%  7.25% 3 179 97.5 93.9 16.6 16.8  0.21%  5.68% 4 196 96.7 91.5 17.1 27.5  7.71% 28.14% 5 197 96.8 91.3 19.5 25  8.50% 33.81% 6 195 96.6 90.9 19 25  8.83% 33.15% 7 198 97 90.9 19 25  8.69% 42.86% 8 197 97 91.6 17.7 25 10.10% 36.80% 9 197 97.2 92.1 17.7 24.6  8.24% 24.99% 10 198 97.2 92.4 17.5 24.6  7.00% 19.60% 11 194 96.4 86.4 19.8 30  7.40% 52.40% 12 187 95.7 86.5 19.8 24.3  1.75% 15.36% 13 179 97.1 90.5 19.1 21  2.47% 12.13% 14 191 95.9 85.7 19 35.4  5.22% 65.30% 15 190 96.1 88.7 17.4 23.6  4.57% 60.04% 16 191 95.9 88.2 16.7 22.9 11.21% 32.49% 17 190 96.2 90.2 17.4 18.7 15.71% 35.23% 18 189 95.7 83.9 14.1 74.3  8.39% 85.40% 19 199 95.8 85.4 17.9 20.3 10.60% 48.40% 20 198 96.7 91.4 17.5 20 11.90% 53.60% 21 197 96.7 91 18.2 20.7 12.20% 54.60% 22 199 96.8 91.9 17.1 18.2 15.70% 49.60% 23 198 96.9 91.7 17.4 18.4 15.10% 50.40% 24 196 94.3 79.8 18.5 55.2 22.00% 72.50% *Capacity retention rate and direct current impedance are tested at a preset environmental temperature of 45° C.

[0202] (5) Slurry Processing Performance:

[0203] The electrode active material numbered 23 was used to prepare a slurry in environment with a relative humidity of 2% and 45%, respectively, with the following formulation: the electrode active material, conductive carbon black, and a binder PVDF were mixed at a mass ratio of 96:2.5:1.5 A solvent N-methyl-pyrrolidone (NMP) was added, with a mass of the solvent accounting for 30% of a total weight of the slurry, and a resulting mixture was stirred to form a uniform positive-electrode slurry. The slurries prepared in environment with two different humidity were left standing, and viscosities of the electrode slurries were analyzed at regular intervals by using a rheological analyzer (Gemini 150 Rheometer, Malvern Instruments ltd).

[0204] In addition, based on the foregoing testing method, the sample numbered 24 was also treated in the same way and taken as a reference group, and results are shown in the following table:

TABLE-US-00007 TABLE 6 Number No. 23 No. 23 No. 24 No. 24 2% RH 45% RH 2% RH 45% RH Standing Viscosity Viscosity Viscosity Viscosity time (h) (mPa*s) (mPa*s) (mPa*s) (mPa*s) 0 8300 9490 12700 11350 1 10100 10650 13450 16400 2 12800 10050 15700 24500 4 13200 12650 17600 47300 12 14650 13800 20050 >50000 24 15300 16000 22750 ∞ 48 17300 17500 22550 ∞ ∞ indicates that the viscosity is too high to be measured accurately.

[0205] The electrode active material numbered 17 was used to prepare a slurry in environment with a relative humidity of 2% and 45%, respectively, with the following formulation: the electrode active material, conductive carbon black, and a binder PVDF are mixed at a mass ratio of 96:2.5:1.5. A solvent N-methyl-pyrrolidone (NMP) was added, with a mass of the solvent accounting for 30% of a total weight of the slurry, and a resulting mixture was stirred to form a uniform positive-electrode slurry. The slurries prepared in environment with two different humidity were left standing, and viscosities of the electrode slurries were analyzed at regular intervals by using a rheological analyzer (Gemini 150 Rheometer, Malvern Instruments ltd).

[0206] In addition, based on the foregoing testing method, the sample numbered 18 was treated in the same way and taken as a reference group, and results are shown in the following table:

TABLE-US-00008 TABLE 7 Number No. 17 No. 17 No. 18 No. 18 2% RH 45% RH 2% RH 45% RH Standing Viscosity Viscosity Viscosity Viscosity time (h) (mPa*s) (mPa*s) (mPa*s) (mPa*s) 0 10780 9760 8680 12100 1 12650 13780 10260 22380 2 14760 14760 12650 36590 4 15290 15870 14870 48820 12 16870 17230 17530 >50000 24 18540 19430 20120 ∞ 48 19520 20360 21000 ∞ ∞ indicates that the viscosity is too high to be measured accurately.

[0207] From the foregoing experimental data, it can be learned that compared to the electrode active materials (No. 18 and 24) without a coating layer, the electrode active materials (No. 17 and 23) with a coating layer have improved processing performance. Specifically, the electrode active materials (No. 17 and 23) with a coating layer have relatively low viscosity and no obvious gelation in appearance by visual observation, no matter whether the slurry is prepared at 2% or 45% relative humidity. Such a slurry is beneficial to subsequent processes of coating and cold pressing, and beneficial to improving electrical performance of the battery.

[0208] From the foregoing experimental data, it can be learned that a coating layer containing a reaction product of a lithium-containing compound and a sulfur-containing compound can improve performance of the electrode active material. Compared to the electrode active materials (No. 11-13, 18, and 24) without a coating layer, the electrode active materials (No. 1-10, 14-17, and 19-23) with a coating layer have the following beneficial effects:

[0209] 1) Increased specific capacity;

[0210] 2) Improved cycling performance;

[0211] 3) Reduced direct current resistance;

[0212] 4) Lower gas production;

[0213] 5) Relatively good performance at a higher voltage; and

[0214] 6) Stable production and processing at high relative humidity.

[0215] According to some embodiments of this application, this application provides a battery. FIG. 3 shows a battery 10 according to an embodiment of this application. FIG. 4A is a schematic diagram of a housing of a battery, and FIG. 4B is a schematic diagram of the housing and a cover plate of the battery. As shown in FIG. 3 and FIG. 4, in this embodiment, the battery may also be referred to as a battery cell 20. The battery cell 20 includes a housing 21, an electrode assembly 22, and an electrolyte, where the electrode assembly 22 is accommodated in the housing 21 of the battery cell 20, and the electrode assembly 22 includes a positive-electrode plate, a negative-electrode plate, and a separator. The separator may be the separator prepared in the embodiments of this application. The electrode assembly 22 may be a wound structure or a stacked structure, and may, for example, be the structure actually used in the embodiments of this application. The housing 21 includes a shell 211 and a cover plate 212. The shell 211 includes an accommodating cavity 211a formed by a plurality of walls, and an opening 211b. The cover plate 212 is disposed on the opening 211b to seal the accommodating cavity 211a. In addition to the electrode assembly 22, the accommodating cavity 211a further accommodates the electrolyte. The positive-electrode plate and the negative-electrode plate of the electrode plate assembly 22 are generally provided with tabs. The tabs generally include a positive-electrode tab and a negative-electrode tab. According to some embodiments of this application, a plurality of positive-electrode tabs are provided and stacked together, and a plurality of negative-electrode tabs are provided and stacked together. The tabs are connected to a positive-electrode terminal 214a and a negative-electrode terminal 214b outside the battery cell 20 through connection members 23. In the description of this application, the positive-electrode terminal 214a and the negative-electrode terminal 214b are collectively referred to as an electrode terminal 214. For a prismatic cell, the electrode terminal 214 may generally be disposed on the cover plate 212.

[0216] According to some embodiments of this application, this application provides an apparatus. The apparatus may include a mobile phone, a portable device, a laptop, an electric scooter, an electric vehicle, a steamship, a spacecraft, an electric toy, an electric tool, or the like. The spacecraft may include an airplane, a rocket, a space shuttle, a spaceship, or the like. The electric toy includes a fixed or mobile electric toy, such as a game console, an electric vehicle toy, an electric ship toy, and an electric airplane toy. The electric tool includes an electric metal cutting tool, an electric grinding tool, an electric assembly tool, and an electric railway-specific tool, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an electric impact drill, a concrete vibrator, and an electric planer.

[0217] In this embodiment, the apparatus includes a vehicle. For example, FIG. 5A and FIG. 5B respectively show a side view and a bottom view of a vehicle according to an embodiment of this application. The vehicle may be an oil-fueled vehicle, a gas-powered vehicle, or a new energy vehicle. The new energy vehicle may be a battery electric vehicle, a hybrid electric vehicle, an extended-range electric vehicle, or the like. As shown in FIG. 5A, a battery 10 may be disposed in the vehicle 1. As shown in FIG. 5A, the battery 10 is disposed at the bottom of the vehicle. However, the battery 10 may alternatively be disposed at the head or the tail of the vehicle 1 as required. When the vehicle is driven, the battery 10 may intermittently or continuously supply power to the vehicle 1. For example, the battery 10 may supply electrical energy to apparatuses of the vehicle 1 such as a lamp, a liquid crystal display, and an igniter. For a hybrid electric vehicle or an electric vehicle, the battery 10 may also supply driving power to the vehicle 1. As shown in FIG. 5B, the vehicle 1 may further include a controller 30 and a motor 40, and the controller 30 is configured to control the battery 10 to supply power to the motor 40, for example, to satisfy a working electricity need during start, navigation, and driving of the vehicle 1. In another embodiment of this application, the battery 10 not only can be used as an operational power supply for the vehicle 1, but also can be used as a driving power supply for the vehicle 1, to totally or partially replace fossil fuel or natural gas to provide driving power for the vehicle 1. According to an embodiment of this application, the battery 10 used in the vehicle may alternatively be a battery pack that includes a plurality of battery cells 20 shown in FIG. 3 to FIG. 4.

[0218] The foregoing descriptions are merely specific embodiments, but are not intended to limit the protection scope. Any equivalent modifications or replacements readily figured out by a person skilled in the art within the technical scope disclosed in this application shall fall within the protection scope. Therefore, the protection scope shall be subject to the protection scope of the claims.