Battery

Abstract

The invention relates to the technical field of batteries, in particular to a battery. The battery comprises a positive plate and an electrolyte, the electrolyte comprises a cyano phosphate compound, the cyano phosphate compound comprises one or more of structures shown as a formula (I), a formula (II) and a formula (III), and R1, R2, R3, R4, R5, R6, R7, R8 and R9 are independently selected from alkyl, alkenyl, alkynyl and ether; on the basis of the total weight of the electrolyte, the weight content of the cyano phosphate compound is Dwt%; the positive plate comprises a lithium cobalt oxide material, and the crystal structure A of the lithium cobalt oxide material is equal to I003 / I101 + I003 / delta I104, so that the battery meets the condition that A / D is greater than or equal to 1.2 and less than or equal to 4.2. The battery disclosed by the invention is high in cycling stability, good in storage performance and high in safety performance under high voltage.

Description

A battery Technical Field

[0001] The present disclosure relates to the technical field of batteries, and in particular to a battery.

[0002] Background of the Invention

[0003] Currently, lithium-ion batteries using lithium cobalt oxide cathodes are widely used in smart electronic devices and portable electronics due to their high energy density and long cycle life, greatly facilitating people's lives. To further meet consumers' energy storage needs, higher energy density is primarily achieved by increasing the operating voltage of lithium-ion batteries. However, lithium-ion batteries operating at high voltages (>4.45V) face severe side reactions such as cobalt ion dissolution, solvent oxidative decomposition, and oxygen atom precipitation. These reactions result in severe capacity degradation and battery bulging, reducing battery cycle stability and safety.

[0004] Therefore, it is very important to improve the stability of the cathode-electrolyte interface and improve the cycle performance, gas production and storage performance.

[0005] Summary of the Invention

[0006] To address the technical issues faced by batteries at high voltages (>4.45V), such as oxidative decomposition of the electrolyte solvent and structural damage to the positive electrode material, resulting in short cycle life, poor storage performance, and safety during high-voltage cycling, the present disclosure provides a battery. The battery disclosed herein exhibits high cycle stability, good storage performance, and high safety performance at high voltages (>4.45V).

[0007] To achieve the above-mentioned object, the present disclosure provides a battery, comprising a positive electrode and an electrolyte, wherein the electrolyte comprises a cyanophosphate compound, wherein the cyanophosphate compound comprises one or more of the structures represented by formula (I), formula (II) and formula (III),

[0008] Wherein, R1, R2, R3, R4, R5, R6, R7, R8, and R9 are each independently selected from an O atom, a substituted or unsubstituted C1-C9 alkyl group, a substituted or unsubstituted C2-C9 alkenyl group, a substituted or unsubstituted C2-C9 alkynyl group, a substituted or unsubstituted C2-C9 alkoxy group, a substituted or unsubstituted C2-C9 alkenyloxy group, a substituted or unsubstituted C2-C9 alkynyloxy group, and a blank bond, and the substituted substituent is selected from one or more halogens; based on the total weight of the electrolyte, the weight content of the cyanophosphate compound is Dwt%; the positive electrode sheet comprises a lithium cobalt oxide material, and the crystal structure of the lithium cobalt oxide material is A=ΔI 003 / △I 101 +△I003 / △I 104 , then the battery satisfies: 1.2≤A / D≤4.2.

[0009] In one example, R1, R2, R3, R4, R5, R6, R7, R8, and R9 are each independently selected from substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C2-C5 alkenyl, substituted or unsubstituted C2-C5 alkynyl, substituted or unsubstituted C2-C5 alkoxy, substituted or unsubstituted C2-C5 alkenyloxy, and substituted or unsubstituted C2-C5 alkynyloxy.

[0010] In one embodiment, the substituted substituent is F.

[0011] In one embodiment, the cyanophosphate compound includes one or more of the structures represented by formula (II) and formula (III).

[0012] In one embodiment, the cyanophosphate compound includes a compound having a structure shown in formula (II).

[0013] In one example, the battery satisfies: 2.1≤A / D≤3.8.

[0014] In one example, the electrolyte further includes an ether nitrile compound Z, and the ether nitrile compound includes one or more of the following structures:

[0015] In one embodiment, the weight content of the ether nitrile compound Z is 0.2 wt%-3 wt% based on the total weight of the electrolyte. When the weight content of the ether nitrile compound in the electrolyte is within the above-specified range, due to the ether nitrile compound's inherently stronger solvating ability, it is more easily coordinated with lithium ions, thereby preventing the cyanophosphate compound from reacting with the lithium salt to produce fluorophosphorus compounds. Fluorophosphorus compounds can violently decompose during battery overcharge / overdischarge, disrupting the stability of the electrode-electrolyte interface film and leading to safety issues such as fire and explosion. Therefore, on the one hand, the introduction of cyanophosphate into the electrolyte can react with lithium cobalt oxide of a specific XRD crystal form, improving the stability of the lithium cobalt oxide-electrolyte interface and optimizing the battery's gas production, cycle performance, and K value. On the other hand, the introduction of the ether nitrile compound into the electrolyte can inhibit the generation of fluorophosphorus compounds from the phosphate ester, thereby improving the ability to prevent overcharge / overdischarge. When the weight content of ether nitrile compounds in the electrolyte is lower than 0.2wt%, the ether nitrile compounds are insufficient to inhibit the side reaction between cyanophosphate compounds and lithium salts; when the weight content of ether nitrile compounds in the electrolyte is higher than 3wt%, the excess ether nitrile compounds will increase the internal resistance of the battery, which is not conducive to lithium ion transmission.

[0016] Through the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0017] The present invention adds a cyanophosphate compound with a specific structure to the electrolyte. The phosphoric acid-containing functional group in the cyanophosphate compound can capture active free radicals when the electrolyte burns, thereby playing a flame retardant role in the electrolyte and improving the safety performance of the battery. At the same time, by limiting 1.2≤A / D≤4.2, the positive electrode-electrolyte interface stability can be improved, and the interface side reactions between the positive electrode sheet and the electrolyte can be reduced. The problems of short cycle life, poor storage performance and safety performance of the battery during high-voltage cycling caused by oxidative decomposition of the electrolyte solvent and structural destruction of the positive electrode material faced by the battery under high voltage are solved, thereby improving the cycle stability, storage performance and safety performance of the battery. At the same time, the gas production of the lithium cobalt oxide material under high voltage (>4.45V) can be reduced, the conductivity of the lithium cobalt oxide material can be improved, the K value can be optimized, and the rate performance of the battery can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the XRD spectrum of lithium cobalt oxide material. DETAILED DESCRIPTION

[0019] The following is a detailed description of the specific embodiments of the present disclosure. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure. In this article, unless otherwise specified, data ranges include endpoints.

[0020] The present disclosure provides a battery, comprising a positive electrode and an electrolyte, wherein the electrolyte comprises a cyanophosphate compound, wherein the cyanophosphate compound comprises one or more of the structures represented by formula (I), formula (II) and formula (III).

[0021] Wherein, R1, R2, R3, R4, R5, R6, R7, R8, and R9 are each independently selected from an O atom, a substituted or unsubstituted C1-C9 alkyl group, a substituted or unsubstituted C2-C9 alkenyl group, a substituted or unsubstituted C2-C9 alkynyl group, a substituted or unsubstituted C2-C9 alkoxy group, a substituted or unsubstituted C2-C9 alkenyloxy group, a substituted or unsubstituted C2-C9 alkynyloxy group, and a blank bond, and the substituted substituent is selected from one or more halogens; based on the total weight of the electrolyte, the weight content of the cyanophosphate compound is Dwt%; the positive electrode sheet comprises a lithium cobalt oxide material, and the crystal structure of the lithium cobalt oxide material is A=ΔI 003 / △I 101 +△I 003 / △I 104 , then the battery satisfies: 1.2≤A / D≤4.2.

[0022] The inventors of the present invention have found that A=△I 003 / △I 101 +△I 003 / △I 104 The specific crystal structure of lithium cobalt oxide can produce a good synergistic effect with cyanophosphate compounds. The reason is that the specific crystal structure of lithium cobalt oxide facilitates the directional adsorption of the cyano functional groups of the specific content of cyanophosphate compounds (the two are in a specific relationship) on the surface of the positive electrode, thereby enhancing the complexation effect of the cyano functional groups on metal ions (cobalt ions) without compromising battery performance due to too little or too much cyano additives. In addition, the phosphate ester adsorbed in the cyanophosphate compound contains P=O, which can coordinate with lithium ions, accelerate the migration of the electrolyte from the bulk phase to the positive electrode interface, improve the battery's rate performance, and reduce polarization.

[0023] A cyanophosphate compound with a specific structure is added to the electrolyte. The cyano group in the cyanophosphate compound can be adsorbed on the metal ion site on the surface of the positive electrode. The lithium cobalt oxide material with a specific crystal structure has good crystallinity and a neat layered structure. The specific crystal structure is conducive to the cyano functional group in the cyanophosphate compound being uniformly adsorbed on the surface of the positive electrode, forming a cyanophosphate compound adsorption layer with a directional arrangement, thereby complexing the cobalt ions on the surface of the lithium cobalt oxide material and inhibiting the dissolution of cobalt ions, thereby improving the structural stability of the lithium cobalt oxide material. Moreover, the cyanophosphate compound forms a directional and orderly distribution on the surface of the lithium cobalt oxide material with a specific crystal structure, which can facilitate the cyanophosphate compound to play a role, avoid the problem of abuse of the cyanophosphate compound or uneven local action, thereby achieving the effect of improving the stability of the positive electrode-electrolyte interface. In addition, the phosphoric acid-containing functional group in the cyanophosphate compound can capture active free radicals when the electrolyte burns, thereby playing a flame retardant role in the electrolyte and improving the safety performance of the battery.

[0024] The battery may satisfy: 1.2≤A / D≤4.2 (e.g., 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2). When A / D is limited to the above-mentioned specific range, the lithium cobalt oxide material has high crystallinity and a neat layered structure, and the surface ions are arranged in an orderly manner. Based on this, through the synergistic combination of cyanophosphate compounds and lithium cobalt oxide materials, the cyano functional groups in the cyanophosphate compounds can be uniformly adsorbed on the surface of the positive electrode sheet to form a directionally arranged molecular interface. This molecular interface can effectively complex the cobalt ions or other dopant ions on the surface of the lithium cobalt oxide material, thereby inhibiting the dissolution of active ions on the surface of the positive electrode material (lithium cobalt oxide material) under high voltage, improving the structural stability of the positive electrode material (lithium cobalt oxide material), and thus improving the storage performance and high-temperature cycle performance of the battery. Moreover, since the lithium cobalt oxide material is prone to gassing at high voltage (>4.45V) and its own conductivity is poor, by limiting the crystal structure of the lithium cobalt oxide material and combining it with the cyanophosphate compound, the gas production of the lithium cobalt oxide material under high voltage can be reduced, the conductivity of the lithium cobalt oxide material can be improved, and the rate performance of the battery can be improved. When A / D is higher than 4.2 or lower than 1.2, the crystallinity of the lithium cobalt oxide material is poor, the layered structure is relatively chaotic, and the surface ions are disordered, making it impossible for the cyanophosphate compounds to effectively complex the active ions on the surface of the lithium cobalt oxide material. As a result, the cyanophosphate compounds cannot form a uniform directional distribution on the surface of the positive electrode, and cannot effectively inhibit the dissolution of cobalt ions or other dopant ions, resulting in rapid degradation of battery performance.

[0025] By adding the aforementioned cyanophosphate compound with a specific structure to the electrolyte, and by combining the cyanophosphate compound with a lithium cobalt oxide material with a specific crystal structure, the battery has achieved higher cycle stability, higher storage performance, and higher safety performance than existing technologies. To further enhance the effect, one or more of these technical features may be further optimized.

[0026] In one embodiment, the battery satisfies: 2.1≤A / D≤3.8. Limiting the battery to the above specific range can further improve the cycle stability, rate performance and safety performance of the battery and further reduce the expansion rate of the battery.

[0027] Since the three sites connected to P (R1, R2 and R3, or R4, R5 and R6, or R7, R8 and R9) form a rotationally symmetrical structure, and these three sites can be independently selected from the same group, the formula (I) and formula (II) of the present application actually cover other connection methods. For example, formula (I) actually covers the connection between cyano (-CN) and R2 and connected with R3 ), formula (II) actually covers These situations are all structures of the cyanophosphate compounds protected by the present invention and are no longer listed separately in this article.

[0028] R1, R2, R3, R4, R5, R6, R7, R8, and R9 may be the same or different and are each independently selected from an O atom, a substituted or unsubstituted C1-C9 alkyl group, a substituted or unsubstituted C2-C9 alkenyl group, a substituted or unsubstituted C2-C9 alkynyl group, a substituted or unsubstituted C2-C9 alkoxy group, a substituted or unsubstituted C2-C9 alkenyloxy group, a substituted or unsubstituted C2-C9 alkynyloxy group, and a blank bond.

[0029] In the present disclosure, the expression "substituted or unsubstituted" means, for example, "substituted or unsubstituted C1-C9 alkyl", which means that the alkyl group may be substituted or may not be substituted by any substituent. When the alkyl group is substituted by a substituent, one H in the alkyl group may be substituted, multiple H groups may be substituted, or all H groups may be substituted.

[0030] The structural formulas of the cyanophosphate compounds are shown in formula (I), formula (II) and formula (III). It can be seen that both sides of R1, R4, R6, R7, R8, and R9 are connected to the P atom and the cyano group. Therefore, the alkyl, alkenyl, alkynyl, alkoxy, alkenyloxy, and alkynyloxy groups selected from R1, R4, R6, R7, R8, and R9 can all satisfy the structures of (I), formula (II) and formula (III). For example, if R1 is a methyl group, the structure of the methyl group is -CH2-.

[0031] In this disclosure, an empty bond means that there is no group or atomic group at that position. For example, if R1 is an empty bond, the P on one side is directly connected to the cyano group on the other side. If R2 is an empty bond, there is no R2 group on P.

[0032] The C1-C9 alkyl group is, for example, selected from methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, isopentyl, tert-pentyl, neopentyl, cyclopentyl, 2,2-dimethylpropyl, 1-ethylpropyl, 1-methylbutyl, 2-methylbutyl, n-hexyl, isohexyl, 2-hexyl, 3-hexyl, cyclohexyl, 2-methylpentyl, 3-methylpentyl, 1,1,2-trimethylpropyl, 3,3-dimethylbutyl, n-heptyl, 2-heptyl, 3-heptyl, 2-methylhexyl, 3-methylhexyl, 4-methylhexyl, isoheptyl, cycloheptyl, n-octyl, cyclooctyl, and nonyl.

[0033] The C2-C9 alkenyl group is, for example, selected from vinyl, n-propenyl, isopropenyl, cyclopropenyl, n-butenyl, isobutenyl, sec-butenyl, tert-butenyl, cyclobutenyl, n-pentenyl, isopentenyl, tert-pentenyl, neopentenyl, cyclopentenyl, 2,2-dimethylpropenyl, 1-ethylpropenyl, 1-methylbutenyl, 2-methylbutenyl, n-hexenyl, isohexenyl, 2-hexenyl, 3-hexenyl, cyclohexenyl, 2-methylpentenyl, 3-methylpentenyl, 1,1,2-trimethylpropenyl, 3,3-dimethylbutenyl, n-heptenyl, 2-heptenyl, 3-heptenyl, 2-methylhexenyl, 3-methylhexenyl, 4-methylhexenyl, isoheptenyl, cycloheptenyl, n-octenyl, cyclooctenyl, and nonyl.

[0034] The C2-C9 alkynyl group is, for example, selected from ethynyl, n-propynyl, isopropynyl, n-butynyl, isobutynyl, sec-butynyl, tert-butynyl, n-pentynyl, isopentenyl, tert-pentynyl, neopentynyl, 2,2-dimethylpropynyl, 1-ethylpropynyl, 1-methylbutynyl, 2-methylbutynyl, n-hexynyl, isohexynyl, 2-hexynyl, 3-hexynyl, cyclohexynyl, 2-methylpentynyl, 3-methylpentynyl, 1,1,2-trimethylpropynyl, 3,3-dimethylbutynyl, n-heptynyl, 2-heptynyl, 3-heptynyl, 2-methylhexynyl, 3-methylhexynyl, 4-methylhexynyl, isoheptynyl, cycloheptynyl, n-octynyl, cyclooctynyl, and nonynyl.

[0035] The C2-C9 alkoxy group is, for example, selected from ethaneoxy, n-propaneoxy, isopropaneoxy, cyclopropaneoxy, n-butaneoxy, isobutaneoxy, sec-butaneoxy, tert-butaneoxy, cyclobutaneoxy, n-pentaneoxy, isopentanoxy, tert-pentaneoxy, neopentaneoxy, cyclopentaneoxy, n-hexaneoxy, isohexaneoxy, 2-hexaneoxy, 3-hexaneoxy, cyclohexaneoxy, n-heptaneoxy, 2-heptaneoxy, 3-heptaneoxy, isoheptaneoxy, cycloheptaneoxy, n-octaneoxy, cyclooctaneoxy, and nonaneoxy.

[0036] The C2-C9 alkenyloxy group is, for example, selected from vinyloxy, n-propyleneoxy, isopropyleneoxy, n-butenyloxy, isobutenyloxy, sec-butenyloxy, tert-butenyloxy, n-pentenyloxy, isopentenyloxy, tert-pentenyloxy, neopentenyloxy, n-hexenyloxy, isohexenyloxy, 2-hexenyloxy, 3-hexenyloxy, n-heptenyloxy, 2-heptenyloxy, 3-heptenyloxy, isoheptenyloxy, cycloheptenyloxy, n-octenyloxy, cyclooctenyloxy, and nonenyloxy.

[0037] The C2-C9 alkynyloxy group is, for example, selected from ethynyloxy, n-propynyloxy, isopropynyloxy, n-butynyloxy, isobutynyloxy, sec-butynyloxy, tert-butynyloxy, n-pentynyloxy, isopentenyloxy, tert-pentynyloxy, neopentynyloxy, n-hexynyloxy, isohexynyloxy, 2-hexynyloxy, 3-hexynyloxy, n-heptynyloxy, 2-heptynyloxy, 3-heptynyloxy, isoheptynyloxy, cycloheptynyloxy, n-octynyloxy, cycloynyleneoxy, and nonynyloxy.

[0038] R1, R2, R3, R4, R5, R6, R7, R8, and R9 may be the same or different and are each independently selected from a substituted or unsubstituted C1-C5 alkyl, a substituted or unsubstituted C2-C5 alkenyl, a substituted or unsubstituted C2-C5 alkynyl, a substituted or unsubstituted C2-C5 alkoxy, a substituted or unsubstituted C2-C5 alkenyloxy, and a substituted or unsubstituted C2-C5 alkynyloxy.

[0039] In one embodiment, the substituted substituent is selected from one or more halogens, which may be F, Cl, Br, or I.

[0040] In one embodiment, the substituted substituent is F. When the substituted substituent is F, the flame retardancy of the cyanophosphate compound can be improved, and the drop performance of the battery can be optimized.

[0041] In one example, R1, R2, R3, R4, R5, R6, R7, R8, and R9 are selected from an O atom, a substituted or unsubstituted C2-C5 alkoxy group, and a substituted or unsubstituted C2-C5 alkenyloxy group.

[0042] In one embodiment, the cyanophosphate compound includes one or more structures represented by formula (II) and formula (III). In this case, the cyanophosphate compound has a large number of cyano groups, which can improve the efficiency of inhibiting the dissolution of cobalt ions, thereby reducing the K value of the battery and reducing the degree of self-discharge. At the same time, the P=O of the phosphate in the cyanophosphate compound coordinates with lithium ions. After the phosphate is adsorbed to the positive electrode interface, it is conducive to the insertion of lithium ions into the positive electrode, thereby optimizing the charge rate performance of the battery.

[0043] In one embodiment, the cyanophosphate compound includes a structure represented by formula (III). In this case, the cyanophosphate compound has more cyano groups, which can further improve the efficiency of inhibiting the dissolution of cobalt ions, thereby further reducing the K value of the battery and reducing the degree of self-discharge.

[0044] In one embodiment, the cyanophosphate compound includes one or more of the following structures:

[0045] The cyanophosphate compound can be purchased commercially or prepared through conventional preparation processes.

[0046] In one embodiment, based on the total weight of the electrolyte, the weight content Dwt% of the cyanophosphate compound is 0.2wt%-5wt% (for example, 0.2wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%). When the weight content of the cyanophosphate compound in the electrolyte is lower than 0.2wt%, the content of the cyanophosphate compound is too low, and its protective effect on the positive electrode structure is not obvious, resulting in low cycle stability of the battery; when the weight content of the cyanophosphate compound in the electrolyte is higher than 5wt%, the positive electrode-electrolyte interface is overprotected, the impedance of the interface increases, and the impedance of the battery is large. Limiting the weight content of the cyanophosphate compound in the electrolyte to the above-mentioned specific range can not only enhance the interface stability of the positive electrode-electrolyte and enhance the protection of the positive electrode structure, but also maintain a low impedance.

[0047] In one embodiment, based on the total weight of the electrolyte, the weight content D wt % of the cyanophosphate compound is 0.5 wt %-3 wt %.

[0048] In one example, the electrolyte further includes an ether nitrile compound Z, and the ether nitrile compound includes one or more of the following structures:

[0049] In one example, based on the total weight of the electrolyte, the weight content of the ether nitrile compound Z is 0.2wt%-3wt% (for example, 0.2wt%, 0.5wt%, 0.7wt%, 1wt%, 1.2wt%, 1.5wt%, 1.7wt%, 2wt%, 2.2wt%, 2.5wt%, 2.7wt%, 3wt%).

[0050] In one embodiment, based on the total weight of the electrolyte, the weight content of the ether nitrile compound Z is 0.5 wt % to 2 wt %.

[0051] In one embodiment, the weight ratio of the cyanophosphate compound to the ethernitrile compound is (0.1-1.5):1 (e.g., 0.1:1, 0.3:1, 0.5:1, 0.7:1, 1:1, 1.2:1, 1.5:1). When the weight ratio of the cyanophosphate compound to the ethernitrile compound meets the above-mentioned specific range, the ethernitrile compound can inhibit the side reaction between the cyanophosphate compound and the lithium salt, reduce the damage of the side reaction product, the fluorophosphorus compound, to the stability of the electrode-electrolyte interface film, thereby improving the safety performance of the battery.

[0052] In one example, the weight ratio of the cyanophosphate compound to the ether nitrile compound is (0.2-1):1.

[0053] In one example, the electrolyte includes a lithium salt, an organic solvent, and a functional additive.

[0054] In one example, the lithium salt includes one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethylsulfonyl imide, lithium difluorobisoxalatophosphate, and lithium tetrafluoroborate.

[0055] In one embodiment, the weight content of the lithium salt is 10 wt% to 18 wt% (e.g., 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%) based on the total weight of the electrolyte. When the weight content of the lithium salt in the electrolyte is higher than 18 wt%, stress and damage inside the battery may be increased, resulting in a shortened cycle life of the battery. When the weight content of the lithium salt in the electrolyte is lower than 10 wt%, the discharge capacity of the battery may be affected.

[0056] In one example, based on the total weight of the electrolyte, the weight content of the lithium salt is 12 wt%-16 wt%.

[0057] In one example, the organic solvent includes an acid ester and / or a carboxylic acid ester; the carboxylic acid ester includes one or more of the following fluorinated or unsubstituted solvents: propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, propyl propionate, ethyl propionate, methyl butyrate, ethyl n-butyrate; the carbonate includes one or more of the following fluorinated or unsubstituted solvents: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate.

[0058] In one example, based on the total weight of the electrolyte, the weight content of the organic solvent is 60 wt%-82 wt% (eg, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 82 wt%).

[0059] In one embodiment, based on the total weight of the electrolyte, the weight content of the organic solvent is 65 wt % to 73 wt %.

[0060] In one embodiment, the electrolyte includes a functional additive. When the electrolyte includes the cyanophosphate compound, the ether nitrile compound, and the functional additive, the battery exhibits improved cycle stability, storage performance, and safety. Furthermore, the functional additive improves the battery's cycle stability and storage performance while reducing resistance.

[0061] In one example, the functional additive includes one or more of a cyclic carbonate additive, a cyclic sultone additive, and a lithium salt additive.

[0062] In one embodiment, the cyclic carbonate additive includes one or more of fluoroethylene carbonate, vinylene carbonate, and vinyl ethylene carbonate. The cyclic carbonate additive can promote the formation of an electrolyte film on the negative electrode, thereby protecting the negative electrode interface.

[0063] In one embodiment, the cyclic sultone additive includes one or more of 1,3-propane sultone, 1,3-propylene sultone, 2,4-butane sultone, and 1,4-butane sultone. The cyclic sultone additive can promote the formation of an electrolyte film on the positive electrode, further enhancing the protection of the positive electrode sheet.

[0064] In one embodiment, the lithium salt additive includes one or more of lithium difluorooxalatoborate, lithium difluorophosphate, lithium difluorobisoxalatophosphate, and lithium bisoxalatoborate. The lithium salt additive can reduce the impedance of the battery.

[0065] In one example, based on the total weight of the electrolyte, the weight content of the functional additive is 8wt%-29wt% (for example, 8wt%, 10wt%, 15wt%, 20wt%, 25wt%, 29wt%). When the weight content of the functional additive in the electrolyte is lower than 8wt%, the amount of the functional additive is too low, the protective effect on the positive and negative electrodes is not obvious, and the cycle stability of the battery is low; when the weight content of the functional additive in the electrolyte is higher than 29wt%, the amount of the functional additive is too high, over-protecting the positive and negative electrodes, increasing the interface impedance, and the impedance of the battery is higher. When the weight content of the functional additive in the electrolyte is limited to the above-mentioned specific range, the functional additive can not only effectively protect the positive and negative electrodes, but also make the battery have a lower impedance.

[0066] In one example, based on the total weight of the electrolyte, the weight content of the functional additive is 10 wt%-22 wt%.

[0067] In one example, the battery includes a positive electrode sheet, a negative electrode sheet, and a separator.

[0068] In one example, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on one or both sides of the positive electrode current collector, wherein the positive electrode active material layer includes a lithium cobalt oxide material, a conductive agent, and a binder.

[0069] The positive electrode sheet comprises a lithium cobalt oxide material, and the crystal structure of the lithium cobalt oxide material is A=ΔI 003 / △I 101 +△I 003 / △I 104 As shown in Figure 1, △I 003 is the difference between the characteristic diffraction peak height of the (003) crystal plane obtained from the XRD spectrum of the lithium cobalt oxide material and the baseline height; ΔI 101 is the difference between the characteristic diffraction peak height of the (101) crystal plane obtained from the XRD spectrum of the lithium cobalt oxide material and the baseline height; ΔI 104 It is the difference between the characteristic diffraction peak height of the (104) crystal plane obtained by the XRD spectrum of the lithium cobalt oxide material and the baseline height.

[0070] Among them, in the XRD spectrum of the lithium cobalt oxide material, the (003) crystal plane is an XRD peak located at 19.2±0.5°, the (101) crystal plane is a peak located at 37.3±0.5°, and the (104) crystal plane is a peak located at 45.3±0.5°.

[0071] In one embodiment, the crystal structure of the lithium cobalt oxide material is 6.2≤A≤8.3 (e.g., 6.2, 6.5, 6.8, 7, 7.2, 7.5, 7.8, 8, 8.3). When the crystal structure of the lithium cobalt oxide material meets the above-mentioned specific range, the lithium cobalt oxide material has high crystallinity, a neat layered structure, and orderly surface ion arrangement, which is conducive to the formation of a directional molecular interface of the cyanophosphate compound.

[0072] In one example, the crystal structure of the lithium cobalt oxide material is 6.5≤A≤7.6.

[0073] In one example, the lithium cobalt oxide material includes a doped and / or coated modified lithium cobalt oxide material.

[0074] In one example, the lithium cobalt oxide material is a doped and / or coated modified lithium cobalt oxide material.

[0075] The doping and / or coating modification method may be a conventional method in the art, such as mixing a lithium cobalt oxide precursor with a compound containing a doping element or a coating and then performing solid phase sintering.

[0076] In one embodiment, the chemical formula of the lithium cobalt oxide material is Li x Co 1-y M y O2. Chemical formula Li x Co 1-y M y O2 satisfies the principle that the algebraic sum of the positive and negative valences of each element is zero.

[0077] Wherein, 0.9≤x≤1.1 (e.g., 0.9, 0.92, 0.95, 0.98, 1, 1.02, 1.05, 1.08, 1.1), 0≤y≤0.1 (e.g., 0, 0.01, 0.03, 0.05, 0.07, 0.1). When y is 0, the lithium cobalt oxide material does not include a doping element; when y>0, the lithium cobalt oxide material includes a doping element.

[0078] M may be a doping element.

[0079] M may include one or more of Al, Mg, Ti, Zr, Co, Ni, Mn, Y, La, Sr, W, Sc, Ta, and Nb.

[0080] In one embodiment, M includes one or more of Al, Mg, and Ti. When M includes these specific elements as doping elements, it is possible to control defects within the lithium cobalt oxide particles, thereby suppressing the structural phase transition of the lithium cobalt oxide material that causes electrochemical performance degradation during high-voltage charge and discharge.

[0081] In one embodiment, based on the total weight of the doped and modified lithium cobalt oxide material, the weight content of M is 0.02wt%-0.1wt% (e.g., 0.02wt%, 0.03wt%, 0.04wt%, 0.05wt%, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt%, 0.1wt%). When the weight content of M is limited to the above-mentioned specific range, the crystal structure of the lithium cobalt oxide material can be regulated, the stability of the lithium cobalt oxide material can be improved, and the matching effect of the lithium cobalt oxide material and the specific electrolyte of the present invention can be further optimized, thereby improving the cycle stability, rate performance, and safety performance of the battery.

[0082] In one embodiment, based on the total weight of the doped and modified lithium cobalt oxide material, the weight content of M is 0.04 wt % to 0.08 wt %.

[0083] In one embodiment, M includes one or more of Al, Mg, and Ti, and the weight content of M is 0.04 wt% to 0.08 wt% based on the total weight of the doped and modified lithium cobalt oxide material. When M is selected as the above-mentioned specific elements as the doping element, and the weight content of M in the doped and modified lithium cobalt oxide material is limited to the above-mentioned specific range, the cycling stability of the lithium cobalt oxide material during high-voltage charge and discharge is greatly improved.

[0084] In one example, the surface of the lithium cobalt oxide material has a coating layer formed by a coating.

[0085] In one embodiment, the coating layer has a thickness H of less than 50 nm (eg, 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 45 nm, 49 nm). When the coating layer has a thickness greater than or equal to 50 nm, it will hinder the conduction of lithium ions and increase the impedance of the battery.

[0086] In one example, the thickness H of the coating layer is 20 nm ≤ H < 50 nm.

[0087] In one embodiment, based on the total weight of the coated modified lithium cobalt oxide material, the weight content of the coating is 0 wt%-5 wt% (e.g., 0 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%). When the weight content of the coating is 0 wt%, it means that the lithium cobalt oxide material has no coating layer.

[0088] In one example, based on the total weight of the coated modified lithium cobalt oxide material, the weight content of the coating is 0.05 wt % to 0.12 wt %.

[0089] In one embodiment, the coating includes one or more of carbon material, Al2O3, TiO2, ZrO2, MgO, CoO2, CoO, NiO, MnO2, Mn3O4, NbO3, Ta2O5, AlF3, MgF2, CuF2, AlPO3, Li3PO3, lithium lanthanum zirconium oxide (LLZO), lithium aluminum titanium phosphate (LATP), LiCoPO4, Zr3(PO4)4 and Li2PO3F.

[0090] In one example, the lithium cobalt oxide material is a doped and coated modified lithium cobalt oxide material.

[0091] In one embodiment, a doped and coated modified lithium cobalt oxide material has a core-shell structure, wherein the core is a doped and coated modified lithium cobalt oxide material, M comprises one or more of Al, Mg, and Ti, and the weight content of M is 0.04wt%-0.08wt% based on the total weight of the doped and coated modified lithium cobalt oxide material; the shell is a coating layer formed by a coating material, the coating material comprises a carbon material, and the thickness of the coating layer is H 20nm≤H<50nm, and the weight content of the coating is 0.05wt%-0.12wt% based on the total weight of the doped and coated modified lithium cobalt oxide material. The doped and coated lithium cobalt oxide material having the above-mentioned specific structure can improve material stability and improve needle penetration rate.

[0092] In one embodiment, the median particle size Dv50 of the lithium cobalt oxide material is 10 μm-30 μm (for example, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm). When the median particle size of the lithium cobalt oxide material is less than 10 μm, the lithium cobalt oxide particle size is too small, resulting in a decrease in electronic conductivity and an increase in the internal resistance of the lithium ion battery. When the median particle size of the lithium cobalt oxide material is greater than 30 μm, the lithium cobalt oxide particle size is too large, the diffusion path of lithium ions in the positive electrode material becomes longer, resulting in a decrease in the ion diffusion rate, thereby reducing the charge and discharge performance of the battery. When the median particle size of the lithium cobalt oxide material is limited to the above-mentioned specific range, it can simultaneously have good electronic conductivity and ion diffusion rate, reduce the internal resistance of the battery, and improve the charge and discharge performance of the battery.

[0093] In one example, the median particle size Dv50 of the lithium cobalt oxide material is 12 μm-20 μm.

[0094] In one example, based on the total weight of the positive electrode active material layer, the weight content of the lithium cobalt oxide material is 80wt%-99.5wt%, the weight content of the conductive agent is 0.25wt%-10wt%, and the weight content of the binder is 0.25wt%-10wt%.

[0095] In one example, based on the total weight of the positive electrode active material layer, the weight content of the lithium cobalt oxide material is 90wt%-99wt%, the weight content of the conductive agent is 0.5wt%-5wt%, and the weight content of the binder is 0.5wt%-5wt%.

[0096] In one example, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both sides of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder.

[0097] In one example, the negative electrode active material includes graphite and a graphite mixed material optionally containing hard carbon, soft carbon, SiO, and Si.

[0098] In one example, based on the total weight of the negative electrode active material layer, the weight content of the negative electrode active material is 80wt%-99.5wt%, the weight content of the conductive agent is 0.25wt%-10wt%, and the weight content of the binder is 0.25wt%-10wt%.

[0099] In one example, based on the total weight of the negative electrode active material layer, the weight content of the negative electrode active material is 90wt%-99wt%, the weight content of the conductive agent is 0.5wt%-5wt%, and the weight content of the binder is 0.5wt%-5wt%.

[0100] In one example, the conductive agent includes one or more of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, and carbon nanotubes.

[0101] In one example, the binder includes one or more of sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene, polyethylene oxide, and polyvinylidene fluoride.

[0102] The battery may be a lithium-ion battery.

[0103] In one example, the upper voltage limit of the battery is greater than 4.45V.

[0104] The present disclosure will be described in detail below through examples. The examples described in this disclosure are only a portion of the examples of the present disclosure, not all of the examples. Based on the examples in this disclosure, all other examples obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this disclosure.

[0105] The following examples are used to illustrate the electrolyte and positive electrode sheet of the present disclosure.

[0106] Example 1 Group

[0107] Example 1-1

[0108] (1) Preparation of ingredients

[0109] Electrolyte: 3 parts by weight of a cyanophosphate compound (having the structure shown in formula (III-1)), 14.5 parts by weight of a lithium salt (lithium hexafluorophosphate (LiPF6)), 69 parts by weight of an organic solvent (12 parts by weight of EC, 5 parts by weight of PC, 20 parts by weight of PE, and 32 parts by weight of PP), and 13.5 parts by weight of functional additives (5 parts by weight of 1,3-propane sultone, 0.5 parts by weight of lithium difluorooxalatoborate, and 8 parts by weight of fluoroethylene carbonate).

[0110] Positive electrode sheet: positive electrode current collector (aluminum foil);

[0111] 97 parts by weight of lithium cobalt oxide material (LiCoO2), 2 parts by weight of binder (polyvinylidene fluoride (PVDF 500)), and 1 part by weight of conductive agent (conductive carbon black (Super P)).

[0112] (2) Preparation of electrolyte

[0113] In a glove box filled with argon (H2O < 0.1ppm, O2 < 0.1ppm), the organic solvent is mixed evenly, and then fully dried lithium salt is added thereto. After dissolution, functional additives are added and stirred evenly. After passing the moisture and free acid tests, the electrolyte is obtained.

[0114] (3) Preparation of positive electrode

[0115] The lithium cobalt oxide material, binder, and conductive agent were mixed, and N-methylpyrrolidone (NMP) was added. The mixture was stirred in a blender until a uniform and fluid positive electrode slurry was formed. The positive electrode slurry was evenly coated on one side of a 10 μm thick positive electrode current collector. The coated positive electrode current collector was dried in a 120°C oven for 8 hours, then roll-pressed and slit to obtain positive electrode sheets. At this point, if A is 7.1 and D wt% is 3 wt%, then A / D = 7.1 / 3 = 2.37.

[0116] Example I-2 group

[0117] This group of examples is used to illustrate the effects of changing the content D wt % of the cyanophosphate compound in the electrolyte.

[0118] This group of examples was carried out with reference to Example I-1, except that the content Dwt% of the cyanophosphate compound in the electrolyte was changed. For details, see Table I-1.

[0119] Example 1-3 group

[0120] This group of examples is used to illustrate the impact produced when the lithium cobalt oxide material is changed.

[0121] This group of examples was carried out with reference to Example I-1, except that the lithium cobalt oxide material was changed. For details, see Table I-1.

[0122] Example 1-4 group

[0123] This set of examples is used to illustrate the effects of changing the specific selection of cyanophosphate compounds.

[0124] This group of examples was carried out with reference to Example 1, except that the specific selection of the cyanophosphate compound was changed. For details, see Table I-1.

[0125] Example 1-5 group

[0126] This group of examples is used to illustrate the effects of changes in the median particle size of the lithium cobalt oxide material.

[0127] This group of examples was carried out with reference to Example I-1, except that the median particle size of the lithium cobalt oxide material was changed. For details, see Table I-1.

[0128] Example I-6 group

[0129] This set of examples is used to illustrate the effects of changing the content of functional additives in the electrolyte (keeping the internal proportion unchanged).

[0130] This group of examples was carried out with reference to Example I-1, except that the content of the functional additive in the electrolyte was changed. For details, see Table I-1.

[0131] Example I-7 group

[0132] This set of examples is used to illustrate the effects of changing the specific selection of functional additives in the electrolyte (keeping the internal proportions unchanged).

[0133] This group of examples was carried out with reference to Example I-1, except that the specific selection of the functional additives in the electrolyte was changed. For details, see Table I-1.

[0134] Comparative Example 1

[0135] The process was carried out in accordance with Example I-1, except that no cyanophosphate compound was added to the electrolyte. For details, see Table I-1.

[0136] Comparative Example 2

[0137] The same procedure was followed as in Example I-1, except that the crystal structure of the lithium cobalt oxide material was changed so that A / D was adjusted to 0.7. For details, see Table I-1.

[0138] Comparative Example 3

[0139] The same procedure was followed as in Example I-1, except that the crystal structure of the lithium cobalt oxide material was changed so that A / D was adjusted to 5. For details, see Table I-1.

[0140] Table I-1

[0141] * indicates the same as Example 1;

[0142] - means it does not exist.

[0143] Example II Group

[0144] Example II-1

[0145] The process was carried out in accordance with Example I-1, except that D% was changed and 1.5% of ether nitrile compound was added to the electrolyte. For details, see Table II-1.

[0146] Example II-2 Group

[0147] This group of examples is used to illustrate the effects produced when the structure of the ether nitrile compound is changed.

[0148] This group of examples was carried out with reference to Example II-1, except that the structure of the ether nitrile compound was changed. For details, see Table II-1.

[0149] Example II-3 Group

[0150] This group of examples is used to illustrate the effects of changing the content of the ether nitrile compound in the electrolyte.

[0151] This group of examples was carried out with reference to Example II-1, except that the content of the ether nitrile compound in the electrolyte was changed. For details, see Table II-1.

[0152] Table II-1

[0153] Preparation Example

[0154] Batteries were prepared using the electrolytes and positive electrodes obtained in the examples and comparative examples in the following manners.

[0155] (1) Positive electrode

[0156] The positive electrode sheets obtained in the above embodiments and comparative examples were used respectively.

[0157] (2) Negative electrode

[0158] 97% natural graphite anode material, 0.5% single-walled carbon nanotube (SWCNT) conductive agent, 0.5% conductive carbon black (Super P) conductive agent, 0.5% sodium carboxymethyl cellulose (CMC) binder, and 1.5% styrene-butadiene rubber (SBR) binder are mixed in an aqueous phase and stirred in a blender to form a uniform and fluid anode slurry. Subsequently, the slurry is coated on the surface of the anode current collector copper foil, dried in a vacuum oven at 120°C for 8 hours, and then rolled and slit to obtain the desired anode sheets.

[0159] (3) Electrolyte

[0160] The electrolytes obtained in the above-mentioned embodiments and comparative examples were used respectively.

[0161] (4) Diaphragm

[0162] A composite layer of titanium oxide and polyvinylidene fluoride-hexafluoropropylene copolymer with a thickness of 2 μm is coated on a polyethylene separator with a thickness of 5 μm.

[0163] (5) Preparation of lithium-ion batteries

[0164] The positive electrode sheet of step (1), the separator of step (4), and the negative electrode sheet of step (2) are wound to obtain a bare cell without liquid injection; the bare cell is placed in an aluminum-plastic film package, and the electrolyte of step (3) is injected into the dried bare cell. After vacuum packaging, standing, forming, shaping, sorting and other processes, a lithium-ion battery is obtained.

[0165] Test Case

[0166] The batteries obtained in the examples and comparative examples were tested as follows:

[0167] (1) 25℃ normal temperature cycle test

[0168] The battery was placed in an ambient temperature of (25±3)°C and charged at a constant current of 1C to 4.5V with a cut-off current of 0.05C. After the battery was fully charged, it was placed for 5 minutes and then discharged at a constant current of 0.5C to a cut-off voltage of 3.0V. The highest discharge capacity of the first three cycles was recorded as the initial capacity Q. When the cycle reached the required number of times, the last discharge capacity Q1 of the battery was recorded. The recorded results are shown in Table 2.

[0169] The calculation formula is as follows: Capacity retention rate (%) = Q1 / Q×100%.

[0170] (2) 45℃ cycle test

[0171] The battery was placed in a high temperature environment (45±3)℃ and charged at a constant current of 1C to 4.5V with a cutoff current of 0.05C. After the battery was fully charged, it was placed for 5 minutes and then discharged at a constant current of 0.5C to a cutoff voltage of 3.0V. The highest discharge capacity of the first three cycles was recorded as the initial capacity Q2. When the cycle reached the required number of times, the last discharge capacity of the battery was recorded Q3. The recorded results are shown in Table 2.

[0172] The calculation formula is as follows: Capacity retention rate (%) = Q3 / Q2×100%.

[0173] (3) High temperature storage test

[0174] The obtained battery was charged at an ambient temperature of (25±3)°C and the thickness H1 of the battery was measured while maintaining 100% SOC. It was then stored in a high temperature environment of (85±3)°C for 8 hours. After storage, it was allowed to stand at room temperature for 1.5 hours and the thickness H2 of the battery after storage was measured again. The results are recorded in Table 2.

[0175] The calculation formula is as follows: battery expansion rate (%) = (H2-H1) / H1×100%.

[0176] (4) Furnace temperature test

[0177] The resulting battery was placed horizontally on a tray in an oven. The equipment was set to heat up to 130°C at a rate of (5±2)°C / min. The battery was then fully charged at this temperature and left in this environment for 1 hour. After completion, the battery was left to rest for 2 hours and its condition was observed. If the battery did not leak, catch fire, or explode, it was considered "passed." Otherwise, it was considered "failed."

[0178] (4) Rate charge capacity retention

[0179] At a temperature of 20±5℃, charge at a constant current of 0.7C to 4.5V with a cut-off current of 0.05C. After the battery is fully charged, let it rest for 5 minutes, record the capacity Q4, and then discharge at a constant current of 0.2C to a cut-off voltage of 3.0V; let it rest for 1 hour, charge at a rate of 2.5C to 4.5V, cut off at 0.05C, and record the capacity Q5.

[0180] The calculation formula is as follows: rate charge capacity retention (%) = Q5 / Q4×100%.

[0181] (5) K value test

[0182] At a temperature of 20±5°C, test the initial open circuit voltage of the battery and record the voltage OCV1. After standing for 24 hours, test the open circuit voltage of the battery again and record the voltage OCV2.

[0183] The calculation formula is as follows: K value = (OCV1-OCV2) / 24h

[0184] (6) Overcharge test

[0185] At 20±5°C, set the maximum current in (4.0°C) to charge to 4.6V, maintain constant voltage for 7 hours, and then stop the test. After completion, let the battery rest for 2 hours and observe its condition. If the battery does not leak, catch fire, or explode, it is considered "passed." Otherwise, it is considered "failed."

[0186] (7) Over-discharge test

[0187] At 20±5°C, reverse the battery connection and charge at 1C for 120 minutes. Then stop the test. After completion, let the battery rest for 2 hours and observe its condition. If the battery does not leak, catch fire, or explode, it is considered "passed." Otherwise, it is considered "failed."

[0188] The results obtained in Example I-1 are shown in Table I-2.

[0189] Table I-2

[0190] As can be seen from Table I-2, from the comparative examples and the embodiments, it can be seen that the 25°C cycle capacity retention rate of the battery of the embodiment is significantly improved, the 45°C cycle capacity retention rate is significantly improved, the battery expansion rate is significantly reduced, the furnace temperature test results are good, the overcharge test results are good, the over-discharge test results are good, the rate charge capacity retention rate is significantly improved, and the K value is reduced, indicating that when the battery of the present invention meets 1.2≤A / D≤4.2, the cycle stability, storage performance, and safety performance are improved.

[0191] The results obtained in Example II-1 are shown in Table II-2.

[0192] Table II-2

[0193] It can be seen from Table II-2 that the battery of the embodiment has a high 25°C cycle capacity retention rate, a high 45°C cycle capacity retention rate, a low battery expansion rate, good furnace temperature test results, good overcharge test results, good over-discharge test results, a high rate charge capacity retention rate, and a low K value, indicating that the addition of ether nitrile compounds to the electrolyte improves the safety performance, storage performance, and cycle performance of the battery.

[0194] The preferred embodiments of the present disclosure are described in detail above, but the present disclosure is not limited thereto. Within the technical concept of the present disclosure, various simple variations of the technical solution of the present disclosure may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed by the present disclosure and fall within the scope of protection of the present disclosure.

Claims

1. A battery, characterized in that, The battery includes a positive electrode sheet and an electrolyte, the electrolyte includes a cyano phosphate compound, and the cyano phosphate compound includes one or more of the structures represented by formula (I), formula (II), and formula (III). Wherein, R1, R2, R3, R4, R5, R6, R7, R8, and R9 are each independently selected from an O atom, a substituted or unsubstituted C1-C9 alkyl group, a substituted or unsubstituted C2-C9 alkenyl group, a substituted or unsubstituted C2-C9 alkynyl group, a substituted or unsubstituted C2-C9 alkoxy group, a substituted or unsubstituted C2-C9 alkenoxy group, a substituted or unsubstituted C2-C9 alkynyloxy group, and a null bond, and the substituents of the substitution are selected from one or more of halogens; based on the total weight of the electrolyte, the weight content of the cyanophosphate compound is Dwt%; the positive electrode sheet includes a lithium cobaltate material, and the crystal structure A of the lithium cobaltate material = △I 003 / △I 101 +△I 003 / △I 104 , then the battery satisfies: 1.2 ≤ A / D ≤ 4.

2.

2. The battery according to claim 1, wherein R1, R2, R3, R4, R5, R6, R7, R8, R9 are each independently selected from substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C2-C5 alkenyl, substituted or unsubstituted C2-C5 alkynyl, substituted or unsubstituted C2-C5 alkoxy, substituted or unsubstituted C2-C5 alkenyloxy, substituted or unsubstituted C2-C5 alkynyloxy; and / or, the substituent of the substitution is F.

3. The battery according to claim 1 or 2, characterized in that, R1, R2, R3, R4, R5, R6, R7, R8, R9 are selected from O atom, substituted or unsubstituted C2-C5 alkoxy, substituted or unsubstituted C2-C5 alkenyloxy.

4. The battery according to any one of claims 1-3, characterized in that, The cyanophosphate compounds include one or more of the structures shown in formula (Ⅱ) and formula (ⅡⅠ); Preferably, the cyanophosphate compounds include the structure shown in formula (ⅡⅠ).

5. The battery according to any one of claims 1-4, characterized in that, The cyanophosphate compounds include one or more of the following structures:

6. The battery according to any one of claims 1-5, characterized in that, Dwt% is 0.2wt%-5wt%, preferably 0.5wt%-3wt%.

7. The battery according to any one of claims 1-6, characterized in that, The electrolyte further includes an ether nitrile compound Z, and the ether nitrile compound includes one or more of the following structures:

8. The battery according to claim 7, characterized in that, Based on the total weight of the electrolyte, the weight content of the ether nitrile compound Z is 0.2wt%-3wt%; and / or, the weight ratio of the cyanophosphate compound to the weight of the ether nitrile compound is (0.1-1.5):

1.

9. The battery according to any one of claims 1-8, characterized in that, The electrolyte includes functional additives, and the functional additives include one or more of cyclic carbonate additives, cyclic sulfonic acid lactone additives and lithium salt type additives.

10. The battery according to claim 9, characterized in that, The cyclic carbonate additives include one or more of fluoroethylene carbonate, vinylene carbonate and ethylene vinylene carbonate; and / or, the cyclic sulfonic acid lactone additives include one or more of 1,3-propane sultone, 1,3-propene sultone, 2,4-butane sultone and 1,4-butane sultone; and / or, the lithium salt type additives include one or more of lithium difluorooxalate borate, lithium difluorophosphate, lithium difluoro bis(oxalato)phosphate and lithium bis(oxalato)borate.

11. The battery according to any one of claims 1-10, characterized in that, The crystal structure of the lithium cobaltate material is 6.2≤A≤8.3, preferably 6.5≤A≤7.6; and / or, the median particle size Dv50 of the lithium cobaltate material is 10μm-30μm, preferably 12μm-20μm; and / or, the lithium cobaltate material includes a doped and / or coated modified lithium cobaltate material; And / or, the chemical formula of the lithium cobaltate material is Li x Co 1-y M y O2, where 0.9 ≤ x ≤ 1.1, 0 ≤ y ≤ 0.1, and M is a doping element; and / or, M includes one or more of Al, Mg, Ti, Zr, Co, Ni, Mn, Y, La, Sr, W, Sc, Ta and Nb.

12. The battery according to claim 11, characterized in that, Based on the total weight of the doped modified lithium cobaltate material, the weight content of M is 0.02wt%-0.1wt%.

13. The battery according to any one of claims 1-12, characterized in that, The surface of the lithium cobaltate material has a coating layer formed by a coating material.

14. The battery according to claim 13, characterized in that, The thickness of the coating layer is H<50nm; and / or, based on the total weight of the coated modified lithium cobaltate, the weight content of the coating material is 0wt%-5wt%; And / or, the coating includes one or more of carbon materials, Al2O3, TiO2, ZrO2, MgO, CoO2, CoO, NiO, MnO2, Mn3O4, NbO3, Ta2O5, AlF3, MgF2, CuF2, AlPO3, Li3PO3, and Li2PO3F.

15. The battery according to any one of claims 1-14, characterized in that, The battery satisfies: 2.1 ≤ A / D ≤ 3.8; And / or, the battery is a lithium-ion battery; And / or, the upper limit voltage of the battery > 4.45V.

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