A battery

Abstract

The present invention provides a battery. The ternary material of the battery of the present invention has a low residual alkali content, and at the same time, a first additive shown in Formula 1 is added to the electrolyte. The first additive has two oxygen elements in its structure, which can be adsorbed on the surface of the residual alkali Li2CO3 and LiOH, and inhibit the battery gas production and cycle failure caused by the electrolyte reacting with Li2CO3 and LiOH to generate water. In particular, when the content of the first additive in the electrolyte is higher than the residual alkali content of the ternary material, the protective effect of the first additive is the best. This is because when the quality of the first additive is high, it can be fully adsorbed on the surface of all Li2CO3 and LiOH, and the reaction between the electrolyte and the ternary material is fully inhibited, and the performance is optimal.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries, and in particular relates to a lithium ion secondary battery. Background Art

[0002] Due to the advantages of lithium-ion batteries such as high energy density, long cycle life and environmental friendliness, they are widely used in portable electronic products such as mobile phones and laptops, and new energy vehicles.

[0003] Lithium-ion batteries mainly include positive electrode materials, negative electrode materials, separators and electrolytes. At present, the positive electrode materials for batteries used in new energy vehicles are mainly selected from lithium nickel cobalt manganese oxide materials LiNi x Mn y Co z O2 (x+y+z=1), this material has the advantages of high energy density, good safety performance, low cost, etc., and has become a new generation of lithium battery positive electrode material. 3+ The ion is not very stable in the air and is easily reduced to Ni 2+ At the same time, along with the precipitation of lithium, alkaline substances such as LiOH and Li2CO3 are easily generated on the surface of the positive electrode material.

[0004] Too much residual lithium and residual alkali on the surface of the positive electrode material will bring many hazards. For example, too much residual lithium on the surface of the positive electrode material will cause an increase in the pH value. Too much residual alkali will cause gelation of the slurry during the preparation of the positive electrode sheet, resulting in uneven slurry coating to form jelly, affecting the coating; leading to poor high-temperature storage performance of the battery, cycle diving, severe swelling and other problems. Summary of the invention

[0005] In order to improve the deficiencies of the prior art, the purpose of the present invention is to provide a battery. The present invention adjusts the amount of residual alkali on the surface of the positive electrode material and selects a suitable electrolyte additive. Through the combination of the two, the prepared battery has excellent high-temperature storage performance and room-temperature cycle performance.

[0006] The object of the present invention is achieved through the following technical solutions:

[0007] A battery, comprising a positive electrode sheet, a negative electrode sheet and an electrolyte; the positive electrode material in the positive electrode sheet is a ternary material, the residual alkali amount on the surface of the ternary material is ≤1000ppm, and the electrolyte comprises a first additive, wherein the first additive is selected from at least one of the compounds represented by Formula 1;

[0008]

[0009] In Formula 1, R is hydrogen, halogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted benzene ring, substituted or unsubstituted C2-C5 alkenyl; if substituted, the substituent is C1-C5 alkyl, C2-C5 alkenyl or halogen.

[0010] According to an embodiment of the present invention, R is hydrogen, halogen, substituted or unsubstituted C1-C3 alkyl, substituted or unsubstituted benzene ring, substituted or unsubstituted C2-C3 alkenyl; if substituted, the substituent is C1-C3 alkyl, C2-C3 alkenyl or halogen.

[0011] According to an embodiment of the present invention, R is hydrogen, F, substituted or unsubstituted methyl, substituted or unsubstituted ethyl, substituted or unsubstituted benzene ring, substituted or unsubstituted vinyl; if substituted, the substituent is methyl, vinyl or F.

[0012] According to an embodiment of the present invention, the compound represented by Formula 1 is specifically selected from at least one of the following compounds represented by T1 to T6:

[0013]

[0014]

[0015] According to an embodiment of the present invention, the compound represented by Formula 1 can be prepared by a method known in the art, or can be purchased through commercial channels.

[0016] According to an embodiment of the present invention, the content of the first additive is higher than the residual alkali on the surface of the ternary material. The content of the first additive is the mass percentage of the mass of the first additive to the total mass of the electrolyte.

[0017] According to an embodiment of the present invention, the mass of the first additive is 0.1 to 10.0 wt% of the total mass of the electrolyte, for example, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.2 wt%, 1.3 wt%, 1.5 wt%, 1.6 wt%, 1.8 wt%, 2 wt%, 2.2 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.8 wt%, 3 wt%, 3.3 wt%, 3.5 wt%, 3.8 wt%, 4 wt%, 4.2 wt%, 4.5 wt%, 4.8 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt% or 10 wt%.

[0018] According to an embodiment of the present invention, the electrolyte further includes an electrolyte salt and an organic solvent.

[0019] According to an embodiment of the present invention, the organic solvent is selected from at least two of propylene carbonate, ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, fluoroethylene carbonate, γ-butyrolactone, cyclopentane, methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, and butyl butyrate.

[0020] According to an embodiment of the present invention, the electrolyte salt is selected from at least one of an electrolyte lithium salt, an electrolyte sodium salt, an electrolyte aluminum salt, and an electrolyte magnesium salt.

[0021] According to an embodiment of the present invention, the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalatoborate) and lithium difluorooxalatoborate.

[0022] According to an embodiment of the present invention, the mass percentage of the electrolyte salt to the total mass of the electrolyte is 12 wt % to 18 wt %.

[0023] According to an embodiment of the present invention, the electrolyte further includes a second additive, and the second additive is selected from at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl ethylene carbonate (VEC), ethylene sulfate (DTD), 1,3-propane sultone (PS), vinyl sulfite (ES), tris(trimethylsilyl) borate (TMSB), and tris(trimethylsilyl) phosphate (TMSP).

[0024] According to an embodiment of the present invention, the mass percentage of the second additive to the total mass of the electrolyte is 0.5wt% to 4wt%, for example, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, 1.2wt%, 1.3wt%, 1.5wt%, 1.6wt%, 1.8wt%, 2wt%, 2.2wt%, 2.4wt%, 2.5wt%, 2.6wt%, 2.8wt%, 3wt%, 3.3wt%, 3.5wt%, 3.8wt% or 4wt%.

[0025] According to an embodiment of the present invention, the chemical formula of the ternary material is:

[0026] Li 1+x Ni a Co b Mn c M (1-a-b-c) O 2+y, where -0.1≤x≤0.1, a≥0.8, 0≤b≤0.15, 0≤c≤0.15, 1-abc≥0, -0.1≤y≤0.1, and M is one or more of Al, Ti, Mg, Zr, B, and Ca.

[0027] According to an embodiment of the present invention, the surface of the ternary material includes residual alkali, and the residual alkali is Li2CO3 and / or LiOH.

[0028] According to an embodiment of the present invention, the residual alkali content on the surface of the ternary material is ≤1000 ppm.

[0029] According to an embodiment of the present invention, the ternary material is prepared by the following method:

[0030] 1) Add 1000ppm to 3000ppm of LiOH·H2O to water to prepare a washing liquid;

[0031] 2) The ternary material with a surface residual alkali content of >1000ppm is mixed with a washing liquid, subjected to ultrasonic washing treatment, then subjected to filter pressing and drying, and the dried product is sintered to obtain a ternary material with a surface residual alkali content of ≤1000ppm.

[0032] The ultrasonic power of the ultrasonic cleaning treatment is 300-500W, and the time of the ultrasonic cleaning treatment is 5-15 minutes;

[0033] The drying temperature is 150-350°C and the drying time is 1-5h;

[0034] The dried product is sintered in an oxygen atmosphere furnace at a sintering temperature of 250 to 650° C. and a sintering time of 2 to 10 hours.

[0035] Beneficial effects of the present invention:

[0036] The present invention provides a battery. The ternary material of the battery of the present invention has a low residual alkali content, and at the same time, a first additive shown in Formula 1 is added to the electrolyte. The first additive has two oxygen elements in its structure, which can be adsorbed on the surface of the residual alkali Li2CO3 and LiOH, and inhibit the battery gas production and cycle failure caused by the electrolyte reacting with Li2CO3 and LiOH to generate water. In particular, when the content of the first additive in the electrolyte is higher than the residual alkali content on the surface of the ternary material, the protective effect of the first additive is the best. This is because when the content of the first additive is high, it can be fully adsorbed on the surfaces of all Li2CO3 and LiOH, and the reaction between the electrolyte and the ternary material is fully inhibited, and the performance is optimal. DETAILED DESCRIPTION

[0037] The present invention will be described in further detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0038] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the reagents, materials, etc. used in the following examples, unless otherwise specified, can be obtained from commercial channels.

[0039] In the description of the present invention, it should be noted that the terms "first", "second", etc. are only used for descriptive purposes, and do not indicate or imply relative importance.

[0040] The LiNi used in the following examples 0.5 Co 0.3 Mn 0.2 O2 was purchased from commercial sources.

[0041] LiNi 0.5 Co 0.3 Mn 0.2 The test process of residual alkali of O2:

[0042] Take an appropriate amount of LiNi 0.5 Co 0.3 Mn 0.2 O2, using potentiometric titration, hydrochloric acid reacts with the residual alkali in the filtrate to neutralize, the pH electrode indicates the end point, and the residual alkali is calculated based on the volume of the consumed HCl standard solution. According to the test results, it is 2361ppm.

[0043] Preparation Example 1

[0044] Add 2000ppm of LiOH·H2O to pure water to prepare a cleaning solution;

[0045] The above-mentioned ternary material with a residual alkali content of 2361ppm is subjected to ultrasonic washing treatment using a washing liquid, wherein the ultrasonic power during the ultrasonic washing treatment is 300-500W, and the ultrasonic washing treatment time is preferably 5-10 minutes; then it is subjected to filter pressing and drying, and the dried product is sintered to obtain a high-nickel ternary positive electrode material with low residual alkali; wherein the drying temperature is 150-350°C and the time is 1-2h; the dried product is sintered in an oxygen atmosphere furnace, and the sintering temperature is 250-650°C and the time is 2-5h. The residual alkali content on the surface of the ternary material prepared by the above method is 1271ppm, and the test process of the residual alkali content is the same as above.

[0046] Preparation Example 2

[0047] Add 2500ppm of LiOH·H2O to pure water to prepare a cleaning solution;

[0048] The above-mentioned ternary material with a residual alkali content of 2361ppm is subjected to ultrasonic washing treatment using a washing liquid, wherein the ultrasonic power during the ultrasonic washing treatment is 300-500W, and the ultrasonic washing treatment time is preferably 10-15 minutes; then it is subjected to filter pressing and drying, and the dried product is sintered to obtain a high-nickel ternary positive electrode material with low residual alkali; wherein the drying temperature is 150-350°C and the time is 3-5h; the dried product is sintered in an oxygen atmosphere furnace, and the sintering temperature is 250-650°C and the time is 8-10h.

[0049] The residual alkali content on the surface of the ternary material prepared by the above method is 952 ppm, and the testing process of the residual alkali content is the same as above.

[0050] Preparation Example 3

[0051] Add 3000ppm of LiOH·H2O to pure water to prepare a cleaning solution;

[0052] The ternary material with a residual alkali content of 2361ppm is subjected to ultrasonic washing treatment using a washing liquid, wherein the ultrasonic power during the ultrasonic washing treatment is 300-500W, and the ultrasonic washing treatment time is preferably 10-15 minutes; then it is subjected to filter pressing and drying, and the dried product is sintered to obtain a high-nickel ternary positive electrode material with low residual alkali; wherein the drying temperature is 150-350°C and the time is 4-5h; the dried product is sintered in an oxygen atmosphere furnace, and the sintering temperature is 250-650°C and the time is 8-10h.

[0053] The residual alkali content on the surface of the ternary material prepared by the above method is 552 ppm, and the testing process of the residual alkali content is the same as above.

[0054] Example 1

[0055] A lithium-ion battery comprises a positive electrode plate, a separator, an electrolyte, an aluminum-plastic film and a negative electrode plate.

[0056] The negative electrode sheet includes a negative electrode active material, a negative electrode binder, a negative electrode conductive agent and a negative electrode dispersant, wherein the negative electrode active material is graphite, the dispersant is sodium hydroxymethyl cellulose (CMC-Na), the negative electrode binder is styrene-butadiene rubber (SBR), water is a solvent, the conductive agent is super P (SP) and single-walled carbon nanotubes (SWCNTs), and the mass ratio of the negative electrode active material: CMC-Na: SBR: SP: SWCNTs is 96:1.5:1.5:0.9:0.1. The negative electrode sheet is prepared by stirring, coating, rolling, slitting and sheeting. The preparation method of the negative electrode sheet is a conventional technical means in this field.

[0057] The positive electrode sheet includes a positive electrode active material, a positive electrode binder and a positive electrode conductive agent, wherein the positive electrode active material is LiNi with a residual alkali content of ≤1000ppm. 0.5 Co 0.3 Mn 0.2 O2, polyvinylidene fluoride (PVDF) is a binder, N-methylpyrrolidone (NMP) is a solvent, SP (super P) and carbon nanotubes (CNT) are composite conductive agents, the mass ratio of the positive electrode active material: PVDF: SP: CNTs is 96:2:1.5:0.5, and the positive electrode sheet is prepared through stirring, coating, rolling, slitting and sheeting. The preparation method of the positive electrode sheet is a conventional technical means in this field.

[0058] The diaphragm is a polyethylene diaphragm.

[0059] In an argon atmosphere glove box with a water content of <10 ppm, ethylene carbonate (EC), diethyl carbonate (DEC), and propylene carbonate (PC) were uniformly mixed in a mass ratio of 25:70:5 to obtain an organic solvent, and then 12.5 wt % of lithium hexafluorophosphate lithium salt and additives (specific selections are shown in Table 1) were added to the organic solvent.

[0060] The positive and negative electrodes are stacked and assembled, the pole ears are welded, the aluminum-plastic film is packaged, the top and side are sealed, and the moisture is vacuum-baked. After the moisture reaches the standard, the liquid is injected, the electrode is allowed to stand, and the electrode is formed. After the electrode is formed, the electrode is vacuum-sealed again. The charge and discharge range is 3.0V to 4.2V.

[0061] Examples 2-11 and Comparative Examples 1-3

[0062] The specific operation is the same as that in Example 1, the only difference being the amount of residual alkali on the surface of the ternary material and the additives and addition amounts in the electrolyte, as shown in Table 1 for details.

[0063] Table 1 Residual alkali content and additive composition on the surface of ternary materials of the embodiments and comparative examples

[0064] Residual alkali on the surface of ternary materials First Additive Second additive Comparative Example 1 2361ppm / / Comparative Example 2 1271ppm 0.5wt%T1 / Comparative Example 3 952ppm / / Example 1 952ppm 0.05wt%T1 / Example 2 952ppm 0.1wt%T1 / Example 3 952ppm 0.5wt%T1 / Example 4 552ppm 0.5wt%T1 / Example 5 952ppm 1wt%T2 / Example 6 952ppm 1wt%T3 / Example 7 952ppm 1wt%T4 / Example 8 952ppm 1wt%T5 / Example 9 952ppm 1wt%T6 / Example 10 952ppm 5wt%T2 / Embodiment 11 952ppm 0.5wt%T1 1wt%VC

[0065] (1) Cyclic performance test

[0066] The batteries of the comparative example and the embodiment were charged and discharged for 100 cycles at 25°C at a rate of 0.5C; at the same time, the capacity of the 100th week was divided by the capacity of the 1st week to obtain the cycle capacity retention rate, and the results are recorded as shown in Table 2.

[0067] (2) High temperature storage performance test

[0068] The batteries of the embodiment and comparative example were subjected to 5 charge and discharge cycle tests at room temperature at a charge and discharge rate of 1C, and then charged to a fully charged state at a rate of 1C. The 1C capacity Q and the battery thickness T were recorded respectively. The fully charged battery was stored at 60°C for 7 days, and the battery thickness T0 and 1C discharge capacity Q1 were recorded. The battery was then charged and discharged at a rate of 1C for 5 weeks at room temperature, and the 1C discharge capacity Q2 was recorded. The experimental data such as the battery high temperature storage capacity retention rate, capacity recovery rate and thickness change rate were calculated, and the recorded results are shown in Table 2.

[0069] The calculation formula used is as follows:

[0070]

[0071]

[0072]

[0073] Table 2 Performance test results of batteries of embodiments and comparative examples

[0074]

[0075] From the comparison between Comparative Examples 1 to 3 and Examples 1 to 11, it can be seen that by regulating the amount of residual alkali on the surface of the ternary material and the additives in the electrolyte, and using the two in combination, the prepared battery has excellent high-temperature storage performance and room-temperature cycle performance.

[0076] It can be seen from Examples 1 to 3 that when the content of the first additive in the electrolyte is higher than the amount of residual alkali on the surface of the ternary material, it can provide more adequate protection for the positive electrode.

[0077] It can be seen from Example 11 that adding other additives to the electrolyte can further improve the battery performance.

[0078] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A battery, characterized in that: The battery comprises a positive electrode sheet, a negative electrode sheet and an electrolyte; the positive electrode material in the positive electrode sheet is a ternary material, the residual alkali amount on the surface of the ternary material is ≤1000ppm, and the electrolyte comprises a first additive, and the first additive is selected from at least one of the compounds represented by Formula 1; In Formula 1, R is hydrogen, halogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted benzene ring, substituted or unsubstituted C2-C5 alkenyl; if substituted, the substituent is C1-C5 alkyl, C2-C5 alkenyl or halogen.

2. The battery according to claim 1, characterized in that R is hydrogen, halogen, substituted or unsubstituted C1-C3 alkyl, substituted or unsubstituted benzene ring, substituted or unsubstituted C2-C3 alkenyl; if substituted, the substituent is C1-C3 alkyl, C2-C3 alkenyl or halogen.

3. The battery according to claim 2, characterized in that R is hydrogen, F, substituted or unsubstituted methyl, substituted or unsubstituted ethyl, substituted or unsubstituted benzene ring, substituted or unsubstituted vinyl; if substituted, the substituent is methyl, vinyl or F.

4. The battery according to claim 3, characterized in that The compound represented by Formula 1 is specifically selected from at least one of the following compounds represented by T1 to T6:

5. The battery according to claim 1, characterized in that The content of the first additive is higher than the residual alkali content on the surface of the ternary material.

6. The battery according to claim 1, characterized in that The mass of the first additive is 0.1-10.0 wt % of the total mass of the electrolyte.

7. The battery according to any one of claims 1 to 6, characterized in that: The electrolyte also includes a second additive, which is selected from at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl ethylene carbonate (VEC), ethylene sulfate (DTD), 1,3-propane sultone (PS), vinyl sulfite (ES), tris(trimethylsilyl)borate (TMSB), and tris(trimethylsilyl)phosphate (TMSP).

8. The battery according to claim 7, characterized in that The mass percentage of the second additive to the total mass of the electrolyte is 0.5wt% to 4wt%.

9. The battery according to any one of claims 1 to 6, characterized in that: The chemical formula of the ternary material is: Li 1+x Ni a Co b Mn c M (1-a-b-c) O 2+y , where -0.1≤x≤0.1, a≥0.8, 0≤b≤0.15, 0≤c≤0.15, 1-abc≥0, -0.1≤y≤0.1, and M is one or more of Al, Ti, Mg, Zr, B, and Ca.

10. The battery according to any one of claims 1 to 6, characterized in that: The surface of the ternary material includes residual alkali, and the residual alkali is Li2CO3 and / or LiOH.

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