A battery

Abstract

The application provides a battery, in particular a lithium ion battery with high-temperature storage performance, fast charging performance and high safety, wherein the negative electrode binder in the negative electrode sheet is optimized, DTD, a compound shown in formula 1 and a carboxylic acid ester organic solvent are introduced into an electrolyte to construct a stable SEI film, the dissolution of transition metal ions is inhibited, the occurrence of a positive electrode end side side reaction is reduced, and the lithium ion battery has high-temperature performance and fast charging performance.

Description

Technical Field

[0001] This invention relates to a battery, belonging to the field of lithium-ion battery technology. Background Technology

[0002] Due to their superior performance, including high operating voltage, high energy density, long cycle life, low self-discharge rate, and no memory effect, lithium-ion batteries have experienced rapid development in recent years. Simultaneously, the application scope of lithium-ion batteries continues to expand, from the information industry (mobile phones, PDAs, laptops, etc.) to energy and transportation (electric vehicles, grid peak shaving, solar energy, wind power station energy storage, etc.). High reliability and high safety have become fundamental requirements for lithium-ion batteries. With technological advancements, people have increasingly higher performance demands for lithium-ion batteries, expecting them to have longer battery life and excellent safety performance.

[0003] Currently, the main means to improve the energy density of lithium-ion batteries include increasing the battery's operating voltage. However, increasing the battery's operating voltage will cause the electrolyte components to undergo oxidative decomposition reactions under high voltage, which will deteriorate the electrode / electrolyte interface and lead to an unstable state at the interface. This can easily cause the dissolution of transition metal ions, resulting in a phase change in the cathode material structure and the decomposition of electrolyte components, which in turn leads to a sharp decline in battery performance. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a battery, particularly a lithium-ion battery that exhibits superior high-temperature storage performance and fast-charging performance under high voltage while also possessing high safety. This invention constructs a stable SEI film by optimizing the electrolyte composition and the negative electrode binder, reducing side reactions at the electrode interface, and improving the battery's high-temperature storage and fast-charging performance. Simultaneously, the compound shown in Formula 1 introduced into the electrolyte can further reduce heat accumulation inside the battery, improving the battery's thermal conductivity and overcharge pass rate.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A battery, the battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte; wherein the negative electrode comprises a negative current collector and a negative active material layer coated on one or both surfaces of the negative current collector, the negative active material layer comprising a negative active material, a negative conductive agent, and a negative binder;

[0007] The negative electrode binder is a negative electrode binder containing weakly basic adsorption groups;

[0008] The electrolyte includes ethylene sulfate (DTD), carbonyl imidazole compounds, and carboxylic acid ester organic solvents.

[0009] According to an embodiment of the present invention, the carbonyl imidazole compound is a compound containing a carbonyl imidazole group.

[0010] According to an embodiment of the present invention, the carbonyl imidazole compound has the structural formula shown in Formula 1:

[0011]

[0012] In Equation 1, R 11 It is selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, and alkylsulfonyl; if substituted, the substituent is alkyl or halogen;

[0013] R 12 R 13 R 14 They may be the same or different, and are independently selected from cyano, substituted or unsubstituted alkyl groups; if substituted, the substituents are alkyl or cyano.

[0014] According to an embodiment of the present invention, in formula 1, R 11 Selected from hydrogen, substituted or unsubstituted C 1-20 Alkyl, substituted or unsubstituted C 3-20 cycloalkyl, substituted or unsubstituted C 6-20 Aryl, C 1-20 Alkyl sulfonyl group; if substituted, the substituent is C. 1-20 Alkyl groups, halogens;

[0015] R 12 R 13 R 14 They are either the same or different, and are independently selected from cyano, substituted or unsubstituted C groups. 1-20 Alkyl; if substituted, the substituent is C. 1-20 Alkyl, cyano.

[0016] According to an embodiment of the present invention, in formula 1, R 11 Selected from hydrogen, substituted or unsubstituted C 1-12 Alkyl, substituted or unsubstituted C 3-12 cycloalkyl, substituted or unsubstituted C 6-12 Aryl, C 1-12 Alkyl sulfonyl group; if substituted, the substituent is C. 1-12 Alkyl groups, halogens;

[0017] R 12 R 13 R 14 They are either the same or different, and are independently selected from cyano, substituted or unsubstituted C groups. 1-12 Alkyl; if substituted, the substituent is C. 1-12 Alkyl, cyano.

[0018] According to an embodiment of the present invention, in formula 1, R 11 Selected from hydrogen, substituted or unsubstituted C 1-6 Alkyl, substituted or unsubstituted C 3-6 cycloalkyl, substituted or unsubstituted C 6-10 Aryl, C 1-6 Alkyl sulfonyl group; if substituted, the substituent is C. 1-6 Alkyl, F;

[0019] R 12 R 13 R 14 They are either the same or different, and are independently selected from cyano, substituted or unsubstituted C groups. 1-6 Alkyl; if substituted, the substituent is C. 1-6 Alkyl, cyano.

[0020] According to an embodiment of the present invention, in formula 1, R 11 Selected from hydrogen, substituted or unsubstituted C 1-3 Alkyl, substituted or unsubstituted C 3-4 cycloalkyl, substituted or unsubstituted C 6-8 Aryl, C 1-3 Alkyl sulfonyl group; if substituted, the substituent is C. 1-3 Alkyl, F;

[0021] R 12 R 13 R 14 They are either the same or different, and are independently selected from cyano, substituted or unsubstituted C groups. 1-3 Alkyl; if substituted, the substituent is C. 1-3 Alkyl, cyano.

[0022] According to an embodiment of the present invention, the compound represented by Formula 1 is selected from at least one of the compounds represented by Formulas 1-1 to 1-8:

[0023]

[0024]

[0025] According to an embodiment of the present invention, the amount of the compound shown in Formula 1 added is 0.5 wt% to 3 wt% of the total mass of the electrolyte, for example, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt%, or 3 wt%.

[0026] According to embodiments of the present invention, the compound represented by Formula 1 can be prepared by methods known in the art or obtained through commercial purchase.

[0027] According to embodiments of the present invention, the carboxylic acid ester organic solvent is selected from at least one of ethyl acetate (EA), ethyl propionate (EP), or propyl propionate (PP). The carboxylic acid ester organic solvent can reduce the viscosity of the electrolyte and increase its conductivity.

[0028] According to an embodiment of the present invention, the amount of the added carboxylic acid ester organic solvent as a percentage of the total mass of the electrolyte, X, is 5wt% to 40wt%, for example, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, or 40wt%.

[0029] According to an embodiment of the present invention, the amount of ethylene sulfate added, as a percentage (Y) of the total mass of the electrolyte, is 0.1 wt% to 3 wt%, 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%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt%, or 3 wt%.

[0030] According to embodiments of the present invention, the electrolyte further includes one or more of the following compounds: vinylene carbonate, butene sulfite, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

[0031] According to an embodiment of the present invention, the electrolyte further includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0032] According to an embodiment of the present invention, the electrolyte further includes an electrolyte lithium salt, which is selected from at least one of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium trifluorosulfonyl, lithium difluoro(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium tri(trifluoromethylsulfonyl)methyl.

[0033] According to an embodiment of the present invention, the concentration of the electrolyte lithium salt in the electrolyte is 0.5 mol / L to 2.0 mol / L, for example, 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L or 2 mol / L.

[0034] According to an embodiment of the present invention, the positive electrode sheet includes a positive current collector and a positive active material layer coated on one or both surfaces of the positive current collector, wherein the positive active material layer includes a positive active material, a positive conductive agent, and a positive binder.

[0035] According to an embodiment of the present invention, the mass percentage of each component in the positive electrode active material layer is: 94-99 wt% positive electrode active material, 0.5-3 wt% positive electrode conductive agent, and 0.5-3 wt% positive electrode binder.

[0036] According to an embodiment of the present invention, the positive electrode active material is selected from at least one of lithium cobalt oxide, nickel-cobalt-manganese-lithium ternary materials, lithium iron phosphate, and lithium manganese oxide.

[0037] According to an embodiment of the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder.

[0038] According to an embodiment of the present invention, the negative electrode active material is selected from at least one of artificial graphite, natural graphite, hard carbon, soft carbon, and mesophase carbon microspheres.

[0039] According to an embodiment of the present invention, the mass percentage of each component in the negative electrode active material layer is: 94-99 wt% negative electrode active material, 0.5-3 wt% negative electrode conductive agent, and 0.5-3 wt% negative electrode binder.

[0040] According to embodiments of the present invention, the mass percentage N of the negative electrode binder containing weakly basic adsorption groups in the negative electrode sheet is 0.5wt% to 3wt%, for example, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, 2wt%, 2.1wt%, 2.2wt%, 2.3wt%, 2.4wt%, 2.5wt%, 2.6wt%, 2.7wt%, 2.8wt%, 2.9wt%, or 3wt%.

[0041] According to an embodiment of the present invention, the negative electrode binder containing weakly basic adsorption groups comprises at least one polymer, the polymer comprising at least one repeating unit shown in Formula 2 and at least one repeating unit shown in Formula 3:

[0042]

[0043] Wherein, R1 is selected from weakly basic adsorption groups; R2 is selected from dispersing groups; R may be the same or different, and their independence is selected from C. 1-6 Alkyl or hydrogen; * indicates a connecting end.

[0044] According to an embodiment of the present invention, R1 is selected from thiazolyl groups. imidazole or pyridyl

[0045] According to an embodiment of the present invention, R2 is selected from -CONH2 and -CONH(CH2). z OH (z is an integer between 1 and 6), -CN, -COOH, -COOLi, -COONa, -COO(CH2) m OH (m is an integer between 1 and 6) or -COO(CH2) n CH3 (n is an integer between 1 and 10).

[0046] According to embodiments of the present invention, R may be the same or different, and their independence is selected from C. 1-3 Alkyl or hydrogen.

[0047] According to embodiments of the present invention, R may be the same or different, and their independence is selected from CH3 or hydrogen.

[0048] According to an embodiment of the present invention, R1 is derived from a polymeric monomer containing a carbon-carbon double bond that can form a repeating unit as shown in Formula 2, specifically selected from at least one of 1-vinylimidazolium, vinylpyridine, and 5-vinylthiazole.

[0049] According to an embodiment of the present invention, R2 is derived from a polymeric monomer containing a carbon-carbon double bond that can form a repeating unit as shown in Formula 3, specifically selected from at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylamide, hydroxymethyl acrylamide, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, methacrylamide, methacrylonitrile, methacrylic acid, lithium methacrylate, sodium methacrylate, acrylamide, acrylonitrile, acrylic acid, lithium acrylate, and sodium acrylate.

[0050] According to embodiments of the present invention, the negative electrode binder can capture metal ions dissolved from the positive electrode at the negative electrode. Specifically, the lone pair electrons on the N atom in the R1 group can form coordination with transition metal ions (such as nickel, cobalt, manganese, iron, etc.) to form complexes, thereby reducing the concentration of free transition metal ions at the negative electrode interface and thus reducing side reactions of the solvent at the negative electrode. Simultaneously, due to the presence of the R2 group, the negative electrode binder also exhibits good dispersibility.

[0051] According to an embodiment of the present invention, the polymer is a copolymer formed from at least one repeating unit shown in Formula 2 and at least one repeating unit shown in Formula 3. Specifically, it is a random copolymer or a block copolymer, preferably a random copolymer.

[0052] According to an embodiment of the present invention, the repeating unit shown in Formula 2 accounts for 1 mol% to 60 mol% of the total molar amount of the copolymer (e.g., 1 mol%, 2 mol%, 3 mol%, 4 mol%, 5 mol%, 6 mol%, 7 mol%, 8 mol%, 9 mol%, 10 mol%, 15 mol%, 18 mol%, 20 mol%, 22 mol%, 25 mol%, 28 mol%, 30 mol%, 32 mol%, 35 mol%, 38 mol%, 40 mol%, 45 mol%, 50 mol%, 55 mol%, or 60 mol%); the repeating unit shown in Formula 3 accounts for 40 mol% to 99 mol% of the total molar amount of the copolymer (e.g., 40 mol%, 45 mol%, 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, 75 mol%, 80 mol%, 85 mol%, 90 mol%, 95 mol%, 98 mol%, or 99 mol%). The performance of the negative electrode binder can be adjusted by regulating the molar ratio of the repeating units shown in Equation 2 and Equation 3.

[0053] According to an embodiment of the present invention, the weight-average molecular weight of the polymer is 30 million to 2 million. Polymers with molecular weights in this range can satisfy the controllable adjustment of adhesive strength. If the molecular weight of the polymer is too low, for example, below 3000, the cohesive force between molecules will decrease and the adhesive strength will also be too low. If the molecular weight of the polymer is too high, for example, above 2 million, the molecules will be severely entangled during use, which is not conducive to the adhesion of active substances.

[0054] According to an embodiment of the present invention, the polymer has a decomposition temperature >300°C. That is, the polymer does not decompose below 300°C, indicating high thermal stability. The polymer has a glass transition temperature <60°C (DSC test), meaning the polymer has high bonding strength, which imparts good toughness to the binder and allows the electrode to maintain a certain degree of toughness.

[0055] According to an embodiment of the present invention, the negative electrode binder has the structural formula shown in Formula I:

[0056]

[0057] Where x:y is (1~60):(40~99); R1 and R2 are defined as described above.

[0058] According to an embodiment of the present invention, the adhesive has the structural formula shown in Formula II:

[0059]

[0060] The definitions of x and y are the same as above.

[0061] The present invention also provides a method for preparing the above-mentioned negative electrode binder, the method comprising the following steps:

[0062] The binder is prepared by dissolving a monomer containing an R1 group and a monomer containing an R2 group in water (or DMF, NMP, DMSO), selecting a suitable initiator and catalyst according to the polymerization system, and carrying out a copolymerization reaction.

[0063] According to embodiments of the present invention, the copolymerization method may be free radical polymerization or redox system polymerization, reversible addition-fragmentation chain transfer polymerization (RAFT), atom transfer radical polymerization (ATRP), or redox polymerization, etc.

[0064] According to an embodiment of the present invention, the reaction is carried out under the protection of an inert gas, wherein the inert gas is high-purity nitrogen or argon.

[0065] According to an embodiment of the present invention, the temperature of the copolymerization reaction is 30–100°C, preferably 40–80°C.

[0066] According to an embodiment of the present invention, the charging cutoff voltage of the battery is 4.5V or higher.

[0067] Terminology and Explanation:

[0068] In this invention, the term "binder" refers to a binder used in lithium-ion batteries. It is a polymer compound and a non-active component in lithium-ion battery electrode sheets, and is one of the essential materials required for manufacturing lithium-ion battery electrode sheets. The main function of the binder is to connect the electrode active material, conductive agent, and electrode current collector, ensuring overall connectivity between them. This reduces electrode impedance and simultaneously gives the electrode sheet good mechanical properties and processability, meeting the needs of actual production.

[0069] The beneficial effects of this invention are:

[0070] This invention provides a battery, particularly a lithium-ion battery with superior high-temperature storage performance, fast charging performance, and high safety. Specifically, it optimizes the negative electrode binder in the negative electrode sheet and introduces DTD, the compound shown in Formula 1, and a carboxylic acid ester organic solvent into the electrolyte to construct a stable SEI film, suppressing the dissolution of transition metal ions and reducing the occurrence of side reactions at the positive electrode, thereby enabling the lithium-ion battery to achieve superior high-temperature performance and fast charging performance. Specifically, DTD and the compound shown in Formula 1 can undergo polymerization reactions at the positive and negative electrodes to form SEI and CEI films. The formed SEI film contains alkyl sulfonate lithium (RSO3Li), which increases the ionic conductivity of the SEI film and improves its stability, effectively suppressing gas generation caused by film decomposition. Therefore, the electrolyte of this invention can form a thinner and more stable SEI film at the negative electrode, improving ionic conductivity and reducing impedance; and at the positive electrode, it forms a film that protects the positive electrode, suppresses the dissolution of metal ions, and reduces solvent reactions at the positive electrode. Furthermore, the negative electrode binder contains weakly alkaline adsorption groups, which can further adsorb metal ions dissolved in the electrolyte. Simultaneously, the use of this binder can improve the flexibility and adhesion of the electrode sheet, enhance battery stability, and prevent battery safety accidents caused by instantaneous heat generation during safety performance testing. Moreover, due to the special structure of the compound shown in Formula 1, it can absorb heat during ring-opening polymerization at high temperatures, thereby reducing the heat of reaction. The heat accumulation inside the battery can further improve the pass rate of the battery's hot box test and overcharge test. Attached Figure Description

[0071] Figure 1 The NMR spectrum of the negative electrode binder shown in Formula II is shown below. Detailed Implementation

[0072] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. Any modifications or equivalent substitutions to the technical solutions of the present invention that do not depart from the spirit and scope of the technical solutions of the present invention should be covered within the scope of protection of the present invention.

[0073] Preparation Example 1: Preparation of Negative Electrode Binder

[0074] The structural formula of the negative electrode binder is shown below:

[0075]

[0076] The synthesis method is as follows: N-vinylimidazole monomer (0.94 g, 10.0 mmol), ethyl acrylate (1.0 g, 10.0 mmol), initiator AIBN (25.0 mg, 0.152 mmol), and solvent DMSO (10 mL) were added separately to 100 mL Schrank flasks. Under an argon atmosphere, oxygen was removed three times using a freeze-thaw cycle, and the reaction proceeded at 65 °C for 24 h. After the reaction was complete, the product was precipitated with diethyl ether and dried under vacuum at 100 °C for 12 h to obtain the final product, with a yield of 80%. Figure 1 The NMR spectrum of the negative electrode binder shows that each characteristic peak corresponds to the previous one, proving the successful synthesis of the negative electrode binder (where x:y = 50:50), and the solvent is DMSO-d6.

[0077] Preparation Example 2: Preparation of Lithium-ion Batteries

[0078] (1) Preparation of positive electrode

[0079] Lithium cobalt oxide (LCO), polyvinylidene fluoride (PVDF), and acetylene black (NMP) were mixed in a weight ratio of 97:1.5:1.5. N-methylpyrrolidone (NMP) was added and the mixture was stirred under vacuum until it formed a uniform and fluid positive electrode slurry. The positive electrode slurry was then uniformly coated onto a current collector aluminum foil. The coated aluminum foil was baked in an oven with five different temperature gradients and then dried in an oven at 120°C for 8 hours. Finally, it was rolled and slit to obtain the desired positive electrode sheet.

[0080] (2) Preparation of negative electrode

[0081] Artificial graphite (anode active material), sodium carboxymethyl cellulose (CMC-Na) (thickener), binder, and acetylene black (conductive agent) were mixed in a weight ratio of 98:N:1:N:1, where N was 0.5–3 (as shown in Table 1). Deionized water was added, and the mixture was stirred in a vacuum mixer to obtain a cathode slurry. The cathode slurry was uniformly coated onto a high-strength carbon-coated copper foil to obtain an electrode sheet. The obtained electrode sheet was dried at room temperature and then transferred to an 80°C oven for 10 hours. After drying, the electrode sheet was rolled and slit to obtain the cathode sheet.

[0082] (3) Electrolyte preparation

[0083] In a glove box filled with inert gas (argon) (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate, propylene carbonate, and diethyl carbonate were mixed evenly in a 1:1:1 ratio. Then, 1.25 mol / L of fully dried lithium hexafluorophosphate (LiPF6) was quickly added and dissolved in a non-aqueous organic solvent. The mixture was stirred evenly, and after passing tests for moisture and free acid, the basic electrolyte was obtained. Different amounts of DTD, the compound shown in Formula 1, and carboxylic acid ester organic solvents were added to the basic electrolyte to obtain the experimental electrolytes, as shown in Table 1.

[0084] (4) Preparation of lithium-ion batteries

[0085] The prepared positive electrode, separator, and negative electrode are stacked in sequence, ensuring that the separator is positioned between the positive and negative electrodes to provide isolation. Then, the cells are wound to obtain bare cells without electrolyte injection. The bare cells are placed in outer packaging foil, and the prepared electrolyte is injected into the dried bare cells. After vacuum sealing, settling, formation, shaping, and sorting, the corresponding lithium-ion batteries are obtained. The charging voltage range of the lithium-ion batteries is 3.0 to 4.5V.

[0086] Lithium-ion battery 60℃ 35D storage test:

[0087] (1) 60℃ 35D storage test: The corresponding battery was adjusted to 50% SOC in a constant temperature environment of 25℃. The initial thickness T1 of the battery was tested when it arrived. It was charged to the upper limit voltage at a constant current and constant voltage of 0.7C, and the cut-off current was 0.05C. Then it was discharged to 3.0V at 0.5C. The capacity obtained by discharging was the initial capacity C1. The battery was charged to the upper limit voltage at a constant current and constant voltage of 0.7C, with a cutoff current of 0.05C. The fully charged battery was stored in a constant temperature environment of 60℃ for 35 days, and the thermal thickness expansion change of the battery was monitored. The final thermal thickness T2 of the battery after 35 days of storage at 60℃ was measured. The thickness expansion rate of the lithium battery at 60℃ is calculated as (T2-T1) / T1×100%. The battery was then placed in a 25℃ environment for 2 hours. After the battery temperature returned to room temperature, it was discharged to 3.0V at 0.5C, and the discharge capacity was recorded as the residual capacity C2. Then, it was charged to the upper limit voltage at a constant current and constant voltage of 0.7C, with a cutoff current of 0.05C, and then discharged to 3.0V at 0.5C again. The capacity obtained after discharge is the recovered capacity C3. The residual capacity retention rate after storage at 60℃ is calculated as C2 / C1×100%, and the recovered capacity retention rate is calculated as C3 / C1×100%. The results are shown in Table 2.

[0088] Lithium-ion battery charging temperature rise test:

[0089] (2) Charging temperature rise test: The obtained batteries are placed in a constant temperature environment of 25℃ and charged at rates of 0.5C, 1C, 3C and 5C respectively. The temperature rise of the battery surface at 1C, 3C and 5C is measured relative to the 0.5C charging. That is, the battery temperature rise is equal to the battery surface temperature at 1C, 3C and 5C charging minus the battery surface temperature at 0.5C charging.

[0090] Lithium-ion battery hot box test:

[0091] (3) 130℃ Hot Chamber Test: After the battery cell is fully charged at a constant current and constant voltage of 0.5C, it is placed in a constant temperature chamber and heated using convection or a circulating hot air chamber with an initial temperature of 20±5℃. The temperature of the hot chamber is increased to 130±2℃ at a rate of 5±2℃ per minute and maintained at this temperature for 30 minutes before the test ends. Judgment criteria: The battery cell does not ignite or explode within 30 minutes. The specific test results are shown in Table 2.

[0092] Lithium-ion battery overcharge test:

[0093] (4) 3C-5V Overcharge Test: Under ambient temperature (25±5)℃, the discharged battery cell is charged with a constant current of 3C to 5.0V, then switched to constant voltage charging. The charging time is limited to 7 hours or charging is stopped when the battery surface temperature stabilizes (temperature difference ≤2℃ within 45 minutes). Judgment criteria: The battery cell does not catch fire or explode. The specific test results are shown in Table 2.

[0094] Table 1. Composition of lithium-ion batteries in comparative and example cases.

[0095]

[0096] Table 2. Electrical performance and safety test results of lithium-ion batteries in comparative and example cases.

[0097]

[0098]

[0099] As shown in Table 2, Comparative Examples 1-6, with the contents of carboxylic acid ester organic solvents, DTD, and the compound shown in Formula 1 fixed, revealed that with the increase of negative electrode binder content, the thickness expansion at 60℃ storage and the temperature rise during 5C charging first decreased and then increased, while the residual capacity / recovery capacity at 60℃ initially increased and then decreased. This is mainly because the negative electrode binder, within its appropriate operating range, plays a crucial role in constructing a stable SEI interface, resulting in superior battery performance. When the negative electrode binder content is too low, it cannot effectively complex metal ions and stabilize the SEI interface; when the binder content is too high, the increased battery impedance leads to a corresponding increase in side reactions on the electrode surface, resulting in deterioration of battery performance.

[0100] In Examples 4 and 7 to 11, the contents of the negative electrode binder, DTD, and the compound shown in Formula 1 were fixed. It was found that with increasing content of carboxylic acid ester organic solvents, the thickness expansion at 60°C storage and the temperature rise during 5C charging initially decreased and then increased. The residual capacity / recovery capacity at 60°C initially increased and then decreased. Performance was optimal when the content of carboxylic acid ester organic solvents was within a suitable range. When the content of carboxylic acid ester organic solvents was less than a certain range, the electrolyte conductivity was low, the impedance was relatively high, and the battery performance was poor. When the content of carboxylic acid ester organic solvents was greater than a certain range, it interacted with the negative electrode binder, increasing the swelling rate of the negative electrode binder and thus degrading the battery performance.

[0101] Examples 4 and Comparative Examples 1 to 17 fixed the contents of the negative electrode binder, carboxylic acid ester organic solvent, and the compound shown in Formula 1; or Examples 4 and Comparative Examples 18 to 22 fixed the contents of the negative electrode binder, carboxylic acid ester organic solvent, and DTD. It was found that as the content of DTD or the compound shown in Formula 1 increased, the thickness expansion at 60°C storage and the temperature rise during 5C charging first decreased and then increased; the residual capacity / recovery capacity at 60°C initially increased and then decreased. The performance was optimal when the contents of DTD and the compound shown in Formula 1 were within a suitable range. When the content of DTD or the compound shown in Formula 1 was less than the specified range, the battery film was incomplete, resulting in poor battery performance and ineffective operation. When the content of DTD and the compound shown in Formula 1 was greater than the specified range, the SEI / CEI film formed at the positive and negative electrode interfaces was thicker, increasing the battery impedance and increasing interfacial side reactions, leading to poor battery performance.

[0102] The performance test results from 60℃ 35D storage also reflect the reduction of transition metal ions in the electrolyte after storage, proving that the negative electrode binder can adsorb transition metal ions.

[0103] In summary, it can be seen that the lithium-ion battery using the solution of this invention possesses superior high-temperature storage performance, high-rate charging performance, and high safety performance, demonstrating extremely high application value. The above is a detailed description of feasible embodiments of this invention, but it does not limit the scope of protection of this invention.

Claims

1. A battery, characterized by, The battery comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer coated on one side or both sides of the negative electrode current collector, and the negative electrode active material layer comprises a negative electrode active material, a negative electrode conductive agent and a negative electrode binder; The negative electrode binder is a negative electrode binder containing a weakly basic adsorption group; The electrolyte comprises ethylene sulfate (DTD), a carbonyl imidazole compound and a carboxylic acid ester organic solvent; The negative electrode binder containing a weakly basic adsorption group comprises at least one polymer, and the polymer comprises at least one repeating unit shown in formula 2 and at least one repeating unit shown in formula 3: Formula 2 Formula 3 wherein R1is selected from weakly basic adsorbing groups; R2is selected from dispersing groups; R, the same or different, are independently selected from C 1-6 alkyl or hydrogen; is a linking end; R1 is selected from thiazole, imidazole or pyridine; R2is selected from -CONH2, -CONH(CH2) z OH, -CN, -COOH, -COOLi, -COONa, -COO(CH2) m OH or -COO(CH2) n CH3; z is an integer between 1 and 6, m is an integer between 1 and 6, n is an integer between 1 and 10; The carbonyl imidazole compound has a structure shown in formula 1: Formula 1 In formula 1, R 11 is selected from the group consisting of hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, alkylsulfonyl; if substituted, the substituents are alkyl, halogen; R 12 , R 13 , R 14 are identical or different and independently from each other selected from the group consisting of cyano, substituted or unsubstituted alkyl; if substituted, the substituent is alkyl, cyano; The addition amount of the compound shown in formula 1 accounts for 0.5wt%-3wt% of the total mass of the electrolyte; The addition amount of the carboxylic acid ester organic solvent accounts for 5wt%-40wt% of the total mass of the electrolyte; The addition amount of the ethylene sulfate accounts for 0.1wt%-3wt% of the total mass of the electrolyte; The mass percentage content N of the negative electrode binder containing a weakly basic adsorption group in the negative electrode sheet is 0.5wt%-3wt%.

2. The battery of claim 1, wherein, The carboxylic acid ester organic solvent is selected from at least one of ethyl acetate (EA), ethyl propionate (EP) or propyl propionate (PP).

3. The battery of claim 1, wherein, The polymer is a copolymer formed by at least one repeating unit shown in formula 2 and at least one repeating unit shown in formula 3; The repeating unit shown in formula 2 accounts for 1mol%-60mol% of the total molar amount of the copolymer; and the repeating unit shown in formula 3 accounts for 40mol-99mol% of the total molar amount of the copolymer.

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