Battery and power consuming device

Abstract

The application relates to a battery and a power utilization device, and belongs to the technical field of batteries. The application adds a cyclic sulfate into an electrolyte of a battery, and meanwhile, the mass percentage of the cyclic sulfate in the electrolyte, the viscosity of the electrolyte at 25 DEG C and the interlayer spacing of graphite satisfy a specific relationship, so that the three parameters play a synergistic role, and thus the battery can have good fast charging performance and cycle performance.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more particularly to batteries and electrical devices. Background Technology

[0002] Lithium-ion batteries, with their outstanding advantages such as high energy density, long cycle life, and low self-discharge rate, have been widely used in consumer electronics, new energy vehicles, and grid energy storage. Currently, the market demand for fast-charging capabilities is increasingly urgent, and electrolyte solvents are a key factor limiting lithium-ion transport. To improve fast-charging performance, low-viscosity solvents with faster lithium-ion transport are often chosen; however, these solvents are prone to violent side reactions with the negative electrode, leading to a significant decrease in battery cycle stability. Therefore, there is an urgent need to develop a technology to simultaneously optimize the fast-charging performance and cycle stability of lithium-ion batteries, further expanding their application scenarios. Summary of the Invention

[0003] The purpose of this application is to overcome the shortcomings of the prior art and provide a battery and power device that enable the battery to have both good fast charging performance and cycle performance.

[0004] To achieve the above objectives, in a first aspect, this application provides a battery, including a cell, the cell comprising a negative electrode and an electrolyte;

[0005] The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one side of the negative electrode current collector. The negative electrode material layer includes a negative electrode material, the negative electrode material includes a negative electrode active material, and the negative electrode active material includes graphite.

[0006] The electrolyte comprises cyclic sulfates;

[0007] The battery satisfies the following condition: 0.0015cp / nm ≤ a×b / c ≤ 38cp / nm;

[0008] Where a% represents the mass percentage of cyclic sulfate esters in the electrolyte.

[0009] b represents the viscosity of the electrolyte at 25°C, expressed in cp.

[0010] c represents the interlayer spacing of graphite, measured in nm.

[0011] Secondly, this application provides an electrical device including the battery.

[0012] Compared with the prior art, the beneficial effects of this application are as follows: This application adds cyclic sulfate esters to the electrolyte of the battery, and controls the mass percentage of cyclic sulfate esters in the electrolyte, the viscosity of the electrolyte at 25°C and the interlayer spacing of graphite to meet a specific relationship, so that these three parameters work together, thereby enabling the battery to have both good fast charging performance and cycle performance. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0014] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0015] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0016] In this application, there are no particular restrictions on the specific dispersion and mixing methods.

[0017] Unless otherwise specified, all reagents or instruments used in this application are commercially available products.

[0018] In this application, terms such as "first time" and "second time" are not used to limit the number of times.

[0019] In this application, "negative electrode material" includes negative electrode active material, conductive agent, binder, etc.; similarly, "positive electrode material" includes positive electrode active material, conductive agent, binder, etc.

[0020] According to a first aspect of this application, a battery is provided, which includes a cell, the cell including a negative electrode and an electrolyte;

[0021] The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one side of the negative electrode current collector. The negative electrode material layer includes a negative electrode material, the negative electrode material includes a negative electrode active material, and the negative electrode active material includes graphite.

[0022] The electrolyte comprises cyclic sulfates;

[0023] The battery satisfies the following condition: 0.0015cp / nm ≤ a×b / c ≤ 38cp / nm;

[0024] Where a% represents the mass percentage of cyclic sulfate esters in the electrolyte.

[0025] b represents the viscosity of the electrolyte at 25°C, expressed in cp.

[0026] c represents the interlayer spacing of graphite, measured in nm.

[0027] The inventors discovered that reducing electrolyte viscosity can improve the transport efficiency of lithium ions in the electrolyte and accelerate the battery charging rate. However, if the viscosity is too low, the electrolyte has a strong electron-acquiring ability and high reactivity, which increases the side reactions with the negative electrode and reduces the battery's cycle performance. Adding cyclic sulfates to the electrolyte can preferentially and earlier participate in the formation of the SEI film during cycling due to their high reduction potential. Furthermore, the film composition contains non-gaseous olefins, which polymerize to form polyolefins, resulting in a better SEI film and reducing side reactions between the electrolyte and the negative electrode. However, the introduction of cyclic sulfates can easily introduce impurities (such as sulfites), which can increase the battery's impedance.

[0028] Electrolyte viscosity is related to the transport rate of lithium ions in the electrolyte. Reducing electrolyte viscosity can increase the transport rate of lithium ions in the electrolyte and improve the fast charging performance of the battery. However, if the viscosity is too low, the electrolyte will have a stronger ability to gain electrons and increase its reactivity, resulting in an increase in side reactions with the negative electrode and deteriorating the cycle performance of the battery.

[0029] Increasing the mass percentage of cyclic sulfates in the electrolyte allows them to preferentially undergo reduction reactions during cycling due to their higher reduction potential, thus participating in the formation of the interfacial protective film earlier and preferentially forming an interfacial protective film at the negative electrode. This reduces the side reactions between low-viscosity solvents and the negative electrode. However, if the mass percentage of cyclic sulfates is too high, the impurities they carry will accumulate synchronously with the amount added. The increased content of these impurities (such as sulfites) will cause an increase in battery impedance.

[0030] The interlayer spacing of graphite refers to the distance between two adjacent 002 crystal planes, reflecting the width of the lithium-ion transport channels between layers. Increasing the interlayer spacing of graphite can widen the lithium-ion transport channels between layers, reduce ion migration resistance, and promote the rapid insertion of lithium ions into the negative electrode lattice, thereby improving the fast-charging performance of the battery. At the same time, the widened interlayer channels will increase electrolyte wetting, resulting in increased side reactions between the electrolyte and the negative electrode, and decreased cycle performance.

[0031] Reducing electrolyte viscosity can increase the transport rate of lithium ions in the electrolyte and accelerate the battery charging rate. However, excessively low viscosity increases the electrolyte's electron-acquiring ability and reactivity, leading to increased side reactions with the negative electrode. Adding cyclic sulfates, with their higher reduction potential, allows them to participate in the formation of the interfacial protective film earlier, preferentially forming the film at the negative electrode and reducing side reactions between low-viscosity solvents and the negative electrode. However, the content of cyclic sulfates cannot be too high, as their introduction can introduce impurities (such as sulfites), which increase battery impedance. Simultaneously, by matching and controlling the interlayer spacing of the negative electrode material, the resistance to lithium ion migration is reduced, promoting rapid lithium ion insertion into the negative electrode lattice, thereby improving the battery's fast-charging performance. By controlling the values ​​of a, b, and c to satisfy the above relationship, these three parameters work synergistically, enabling the battery to achieve both good fast-charging and cycle performance.

[0032] For example, a×b / c is an interval range formed by any two of the following values: 0.0015cp / nm, 0.002cp / nm, 0.004cp / nm, 0.006cp / nm, 0.008cp / nm, 0.01cp / nm, 0.03cp / nm, 0.05cp / nm, 0.07cp / nm, 0.1cp / nm, 0.13cp / nm, 0.3cp / nm, 0.5cp / nm, 0.8cp / nm, 1cp / nm, 3cp / nm, 5cp / nm, 7cp / nm, 10cp / nm, 12cp / nm, 14cp / nm, 16cp / nm, 18cp / nm, 20cp / nm, 22cp / nm, 24cp / nm, 26cp / nm, 28cp / nm, 30cp / nm, 32cp / nm, 34cp / nm, 36cp / nm, 38cp / nm.

[0033] In some implementations, 0.04cp / nm≤a×b / c≤12cp / nm, the synergistic effect of the three parameters a, b and c is stronger, and the balance between the battery's fast charging performance and cycle performance is better.

[0034] Especially when 2cp / nm≤a×b / c≤6cp / nm, the synergistic effect of the three parameters a, b and c is further enhanced, which is more conducive to the balance of the battery's fast charging performance and cycle performance.

[0035] In some embodiments, 0.001% ≤ a% ≤ 3.5%, such that a% is a range formed by any two values ​​of 0.001%, 0.005%, 0.01%, 0.05%, 0.08%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.2%, 3.5%, or higher. In some embodiments, 0.01% ≤ a% ≤ 2%.

[0036] By controlling a% within the range of 0.001% to 3.5%, especially within the range of 0.01% to 2%, cyclic sulfates can better participate in the formation of the SEI film, and the resulting film has a higher olefin content, which is conducive to the formation of more polyolefins, thus making the interfacial film more protective, better reducing the side reactions between the electrolyte and the negative electrode, improving cycle performance, and avoiding the introduction of too many impurities that would lead to increased impedance, thereby being more conducive to a balance between fast charging performance and cycle performance.

[0037] This application does not limit the detection method for the value of 'a', and it can be detected using conventional methods in the art. For example, the detection is performed as follows:

[0038] 1) Electrolyte Collection: Use a battery charge / discharge device to discharge the battery under test. Discharge conditions: current 0.3C, discharge to the lower limit voltage 2.5V; disassemble the battery and collect the electrolyte in a glove box (H2O≤0.1ppm, O2≤0.1ppm). There are three methods for collecting the electrolyte. After removing the battery cover,

[0039] ① If there is free electrolyte, collect the electrolyte into a 5mL sample tube with a pipette and seal it with sealing tape to prevent electrolyte leakage;

[0040] ② If there is no free electrolyte, a hydraulic press (Beijing Heng'ao Technology Co., Ltd. FY-30 hydraulic press) can be used to continuously pressurize until free electrolyte appears. Collect the electrolyte into the sample tube and seal it.

[0041] ③ Add an appropriate amount of dichloromethane extractant to the battery and record the dichloromethane content. After adding dichloromethane, put the battery into an aluminum-plastic bag and seal it with a heat sealer. Transfer it to an ultrasonic oscillator and oscillate for 12 hours to allow the electrolyte in the electrode to mix thoroughly with the dichloromethane. Then, use a pipette to draw the mixture of dichloromethane and electrolyte into a 5mL sample tube and seal the sample tube with sealing glue.

[0042] 2) The collected electrolyte sample was injected into an Agilent Intuvo 9000 gas chromatograph-mass spectrometer using a microsyringe for testing. GC-MS spectra were obtained, and the specific types of cyclic sulfates in the electrolyte were analyzed using a spectral library search. The cyclic sulfates were dissolved in EMC solvent to prepare solutions of different concentrations, and these solutions were injected into the Agilent Intuvo 9000 gas chromatograph-mass spectrometer to obtain standard GC-MS spectra. The GC-MS spectra of the electrolyte to be tested were compared with the standard GC-MS spectra, and the content of cyclic sulfates was determined based on the peak area of ​​the cyclic sulfates in the electrolyte to be tested. If the electrolyte to be tested was a finished product, the component content was directly determined by comparing it with the standard GC-MS spectra, and the mass percentage of cyclic sulfates in the electrolyte was measured, which is the value of 'a'.

[0043] In some implementations, 0.4cp ≤ b ≤ 4cp, where b is a range formed by any two of the following values: 0.4cp, 0.6cp, 0.8cp, 1cp, 1.2cp, 1.5cp, 1.8cp, 2cp, 2.2cp, 2.5cp, 2.8cp, 3cp, 3.2cp, 3.5cp, 3.8cp, 4cp, or more. In some implementations, 1.2cp ≤ b ≤ 2.8cp.

[0044] Controlling b within the range of 0.4 to 4 cp, especially within the range of 1.2 to 2.8 cp, results in a more suitable electrolyte viscosity. This not only improves the transport efficiency of lithium ions in the electrolyte and accelerates the charging rate of the battery, but also reduces the electrolyte's electron-acquiring ability and reactivity, thereby reducing side reactions with the negative electrode and improving the battery's cycle performance. This leads to a better balance between fast charging performance and cycle performance.

[0045] This application does not limit the detection method for the value of b; it can be detected using conventional methods in the art. For example, the following detection method can be used:

[0046] 1) Electrolyte Collection: Use a battery charge / discharge device to discharge the battery under test. Discharge conditions: current 0.3C, discharge to the lower limit voltage 2.5V; disassemble the battery and collect the electrolyte in a glove box (H2O≤0.1ppm, O2≤0.1ppm). There are three methods for collecting the electrolyte. After removing the battery cover,

[0047] ① If there is free electrolyte, collect the electrolyte into a 5mL sample tube with a pipette and seal it with sealing tape to prevent electrolyte leakage;

[0048] ② If there is no free electrolyte, a hydraulic press (Beijing Heng'ao Technology Co., Ltd. FY-30 hydraulic press) can be used to continuously pressurize until free electrolyte appears. Collect the electrolyte into the sample tube and seal it.

[0049] ③ Add an appropriate amount of dichloromethane extractant to the battery and record the dichloromethane content. After adding dichloromethane, put the battery into an aluminum-plastic bag and seal it with a heat sealer. Transfer it to an ultrasonic oscillator and oscillate for 12 hours to allow the electrolyte in the electrode to mix thoroughly with the dichloromethane. Then, use a pipette to draw the mixture of dichloromethane and electrolyte into a 5mL sample tube and seal the sample tube with sealing glue.

[0050] 2) The electrolyte was removed and tested using a Cambridge viscometer. The Cambridge viscometer is designed based on electromagnetic oscillation viscosity detection technology and uses a magnetically levitated probe for viscosity measurement. Specifically, the electrolyte was placed in a beaker, and the sample temperature was controlled at 25°C for testing. After the displayed value stabilized, the reading was taken, which is the value of b.

[0051] The value of b can be controlled by at least one of the following process parameters: the type of solvent components, the ratio between solvent components, and the lithium salt concentration.

[0052] In some implementations, 0.336nm ≤ c ≤ 0.38nm, where c is a range of 0.336nm, 0.338nm, 0.34nm, 0.342nm, 0.345nm, 0.348nm, 0.35nm, 0.352nm, 0.355nm, 0.358nm, 0.36nm, 0.362nm, 0.365nm, 0.368nm, 0.37nm, 0.372nm, 0.375nm, 0.378nm, 0.38nm, or any two of these values. In some implementations, 0.34nm ≤ c ≤ 0.36nm.

[0053] Controlling c within the range of 0.336~0.38nm, especially within the range of 0.34~0.36nm, makes the width of the lithium-ion transport channel between layers more suitable. This is beneficial for reducing ion migration resistance, promoting the rapid insertion of lithium ions into the negative electrode lattice, improving the fast charging performance of the battery, and also reducing the wettability of the electrolyte on the negative electrode sheet, weakening the side reactions between the electrolyte and the negative electrode, and improving cycle performance.

[0054] This application does not limit the detection method for the value of c; it can be detected using conventional methods in the art. For example, the following detection method can be used:

[0055] 1) Use a battery charging and discharging device to discharge the battery under test. Discharge conditions: current 0.3C, discharge to the lower limit voltage 2.5V; disassemble the battery, take out the negative electrode sheet, soak the negative electrode sheet in DMC (dimethyl carbonate) at room temperature for 4 hours, take it out and vacuum dry it at 60℃ for 12 hours, scrape off the powder to obtain negative electrode material powder.

[0056] 2) X-ray diffraction (XRD) tests were performed on the negative electrode material powder using a Rigaku Ultima IV X-ray diffractometer to determine the interlayer spacing c (i.e., d). 002 According to Bragg's equation 2c×𝑠𝑖𝑛(2θ) 𝑐𝑜𝑟 The result is obtained by calculating c = λ, where c is the interplanar spacing in nm.

[0057] θ 𝑐𝑜𝑟 The Bragg angle, after systematic error correction, is more accurate and is expressed in degrees.

[0058] λ is the incident X-ray wavelength, using a Cu target K α1 Rays, λ=1.5406nm;

[0059] n is the reflection order (generally n is taken as 1).

[0060] The value of c can be controlled by at least one of the following process parameters: the types of graphite precursor components and the ratio between the components, the core-shell structure design of the graphite precursor (if any), the doping elements in graphite and their content, carbonization temperature, graphitization temperature, and graphite surface coating (such as coating with amorphous carbon).

[0061] In some embodiments, the cyclic sulfate ester comprises a compound represented by Formula I;

[0062] In Formula I, R1, R2, R3 and R4 each independently include the groups shown in Formula II, hydrogen atoms, alkyl groups of 1 to 6 carbon atoms, halogen atoms, haloalkyl groups of 1 to 3 carbon atoms, alkoxy groups of 1 to 3 carbon atoms, haloalkoxy groups of 1 to 3 carbon atoms, alkenyl groups of 2 to 6 carbon atoms, alkynyl groups of 2 to 6 carbon atoms, aromatic groups, ester groups, cyano groups or sulfonic acid groups;

[0063] In Formula II, R5 and R6 each independently include the group shown in Formula III, a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, a halogen atom, a haloalkyl group of 1 to 3 carbon atoms, an alkoxy group of 1 to 3 carbon atoms, a haloalkoxy group of 1 to 3 carbon atoms, an alkenyl group of 2 to 6 carbon atoms, an alkynyl group of 2 to 6 carbon atoms, an aromatic group, an ester group, a cyano group, or a sulfonic acid group.

[0064] In Formula III, R7 and R8 each independently include a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, a halogen atom, a haloalkyl group of 1 to 3 carbon atoms, an alkoxy group of 1 to 3 carbon atoms, a haloalkoxy group of 1 to 3 carbon atoms, an alkenyl group of 2 to 6 carbon atoms, an alkynyl group of 2 to 6 carbon atoms, an aromatic group, an ester group, a cyano group, or a sulfonic acid group.

[0065]

[0066]

[0067] .

[0068] In some embodiments, the number of sulfate ester groups in Formula I is an integer from 2 to 4, such as 4, 3 or 2, to reduce the molecular weight of the compound shown in Formula I, reduce its film-forming resistance, and facilitate its participation in the formation of the interfacial protective film, thereby reducing the side reactions between the low viscosity solvent and the negative electrode, and thus improving the cycle performance.

[0069] In some embodiments, at least one of R1 to R4 is a hydrogen atom to reduce the steric hindrance of the cyclic sulfate ester, which helps it participate in film formation, generate non-gaseous olefins, and further polymerize to form polyolefins, resulting in better film formation. This further weakens the side reactions between the low-viscosity solvent and the negative electrode, and improves cycle performance.

[0070] In some embodiments, R1 and R3 are the same to make cyclic sulfates easier to synthesize and easier to process.

[0071] In some embodiments, R1 and R3 are selected from the groups shown in Structural Formula II, hydrogen atoms, alkyl groups of 1 to 6 carbon atoms, halogen atoms, haloalkyl groups of 1 to 3 carbon atoms, alkoxy groups of 1 to 3 carbon atoms, haloalkoxy groups of 1 to 3 carbon atoms, alkenyl groups of 2 to 6 carbon atoms, alkynyl groups of 2 to 6 carbon atoms, aromatic groups, ester groups, cyano groups, or sulfonic acid groups, so as to make the cyclic sulfate ester have a smaller molecular weight, lower film-forming resistance, easier formation of an interfacial protective film, weakening the side reaction between the low viscosity solvent and the negative electrode, and improving cycle performance.

[0072] In some embodiments, R1 and R3 are selected from hydrogen atoms, CH3, -C2H5, -C3H7, -CH=CH2, -CH2-CH=CH2, -CH=CH-CH3, -O-CH3, -O-C2H5, -O-C3H7, -F, -Cl, -Br, -I, -CF3, CCl3, -CBr3, -C2F5, -C2Cl5, -C2Br5, -C3F7, -C3Cl7, -C3Br7, -C≡CH, -CH2-C≡CH, -C≡C-CH3, aromatic groups, or... When R1 and R3 are selected from the above functional groups, the molecular weight of the cyclic sulfate ester is smaller and the film-forming resistance is lower. It can better form an interfacial protective film, weaken the side reactions between the low viscosity solvent and the negative electrode, and ultimately improve the cycle performance.

[0073] In some embodiments, the cyclic sulfate ester comprises at least one of the following compounds:

[0074] , , , , ,

[0075] , , , ,

[0076] , , , ,

[0077] , , , ,

[0078] , , , ,

[0079] , , , ,

[0080] , , ,

[0081] , ,

[0082] , , ,

[0083] , ,

[0084] , , .

[0085] In some embodiments, the cyclic sulfate ester comprises at least one of the following compounds:

[0086] When cyclic sulfates include at least one of the above compounds, especially for lithium iron phosphate systems, they can not only better enhance the preferential reaction level of cyclic sulfates on the electrode surface and promote the formation of a dense, highly ionicly conductive SEI film, but also have short functional group chains, which have little impact on the viscosity of the electrolyte, making it easier for the electrolyte to transport ions and thus improving the fast-charging performance of the battery.

[0087] In some embodiments, the graphite contains a dopant element selected from at least one of N, B, S, P, and Si. Doping graphite with N allows N atoms to introduce lone pairs of electrons, disrupting the regularity of the carbon layers and increasing the interlayer spacing. Doping graphite with B atoms, due to their different atomic size and electronic properties compared to carbon, introduces lattice distortion and charge redistribution locally, thereby weakening the van der Waals forces between graphite layers and ultimately increasing the interlayer spacing. Doping graphite with S atoms, due to their larger atomic radius, expands the graphite layers through interlayer insertion, increasing the interlayer spacing. Doping graphite with P atoms allows P atoms to replace C atoms, introducing additional free electrons, increasing the local electron cloud density of the crystal structure, generating repulsive forces, and driving layer separation, thus increasing the interlayer spacing. Simultaneously, the larger P atomic radius also contributes to the expansion of the graphite layers, increasing the interlayer spacing. When Si is doped into graphite, it will be embedded in the graphite layers in the form of nanoparticles, expanding the layers through the physical occupancy effect; at the same time, the Si-C bond formed by Si and C will induce strong lattice distortion, further expanding the interlayer spacing.

[0088] In some embodiments, the mass percentage of the doped elements in the graphite is 0.1% to 5%.

[0089] This application does not limit the preparation method of graphite, which can be obtained by conventional methods. For example, the preparation method of graphite includes the following steps:

[0090] The soft carbon precursor and the hard carbon precursor are mixed in a certain proportion, and then mixed with the dopant source (if any) in a certain proportion and dispersed.

[0091] The heat treatment process consists of two steps: first step: carbonization; second step: high-temperature graphitization.

[0092] Soft carbon precursors include, but are not limited to, at least one of coal tar, pitch, petroleum pitch, needle coke, and pitch coke.

[0093] Hard carbon precursors include, but are not limited to, at least one of resin-based or biomass-based carbon sources such as phenolic resin, epoxy resin, polyfurfuryl alcohol, and cellulose.

[0094] In some embodiments, the dopant source includes at least one of N-containing compounds, S-containing compounds, B-containing compounds, P-containing compounds, and Si-containing compounds. For example, the N-containing compound may be at least one of melamine, urea, polyacrylonitrile, pyridine, polyaniline, etc.; the S-containing compound may be at least one of sulfuric acid, sulfite, polythiophene, benzothiophene, benzenesulfonate, sulfurized polyacrylonitrile, aminosulfonic acid, etc.; the B-containing compound may be at least one of boric acid, boron oxide, triphenylboron, trimethyl borate, boron powder, etc.; the P-containing compound may be at least one of phosphoric acid, phosphate, triphenylphosphine, etc.; and the Si-containing compound may be at least one of elemental silicon, silicon dioxide, silane, etc.

[0095] In some embodiments, dispersion is achieved by mechanical grinding, liquid-phase stirring, or spray drying. In some of these embodiments, dispersion is achieved by grinding, with the following grinding conditions: grinding media: zirconia balls, cemented carbide balls, or agate balls; ball-to-material ratio: 3:1 to 10:1 (mass ratio); rotation speed: 200 to 500 rpm (planetary); grinding time: 30 minutes to 4 hours; atmosphere: inert atmosphere (N2 / Ar) protection.

[0096] In some embodiments, soft carbon precursors and hard carbon precursors are mixed at a mass ratio of 8:2 to 6:4, and then 0.1% to 5% of the total mass of the precursors is added as a dopant source.

[0097] In some embodiments, carbonization is performed at 800°C to 1500°C for 1-3 hours under an inert atmosphere (such as nitrogen or argon).

[0098] In some implementations, high-temperature graphitization satisfies the following: under an inert atmosphere (usually argon), the carbon atoms in the carbonized material are rearranged at a temperature of 2000℃~3500℃ for 0.5-2 hours to form a highly ordered graphite crystal structure, while simultaneously achieving stable solid solution of the doped atoms.

[0099] In some embodiments, the method for preparing the graphite further includes the following steps: subjecting the graphite to pitch coating treatment to construct an amorphous carbon layer on the particle surface, thereby further optimizing ion transport and interface stability.

[0100] In some embodiments, the OI value of the negative electrode material ranges from 0.5 to 40. The OI value of the negative electrode material is the ratio of the peak area of ​​the 004 characteristic peak to the peak area of ​​the 110 characteristic peak in its X-ray diffraction pattern. Controlling the OI value of the negative electrode material within the aforementioned range reduces the orientation disorder of the negative electrode material particles, decreases the tortuosity of ion channels and the openness of the pore structure in the negative electrode sheet, weakens the wetting effect of the electrolyte on the negative electrode sheet, reduces the active sites of the negative electrode sheet, reduces side reactions between the electrolyte and the negative electrode, and improves the cycle performance of the battery. For example, the OI value of the negative electrode material is within the range formed by any two of the following values: 0.5, 1, 2, 4, 6, 8, 10, 15, 20, 25, 30, 35, 40, or more.

[0101] This application does not limit the method for detecting the OI value of the negative electrode material; it can be detected using conventional methods in the art. For example, the following method can be used for detection:

[0102] 1) Pretreatment: Discharge the battery at 0.33C to the lower limit voltage of 2.5V; disassemble the battery, remove the negative electrode, soak it in dimethyl carbonate (DMC) solution at room temperature for 4 hours, dry it after soaking, and scrape off the material powder on the surface of the electrode with a ceramic knife.

[0103] 2) The electrode was tested using an XRD diffractometer. The test conditions were set as follows: copper target, scanning voltage of 40KV, current of 40mA, scanning range of 5-90°, scanning speed of 4° / min, and XRD was calibrated using the silicon internal standard method. The X-ray source was started and the diffraction data was recorded (the scanning rate and scanning range were determined according to the case).

[0104] 3) Calculate the OI value of the negative electrode material. OI value = peak area of ​​the 004 characteristic peak / peak area of ​​the 110 characteristic peak.

[0105] In some embodiments, n is the minimum particle size in the particle size frequency distribution curve of the negative electrode material, in μm; n and a satisfy: 0.00075μm≤a×n≤15μm.

[0106] The particle size frequency distribution curve of the anode material is plotted with particle size on the x-axis and the percentage of particles on the y-axis. The minimum particle size in the particle size frequency distribution curve is the particle size value corresponding to the intersection of the curve and the x-axis. The minimum particle size in the particle size frequency distribution curve of the anode material represents the characteristic size of the finest particle group in the anode material, reflecting the length of the lithium-ion diffusion path and the interfacial reaction activity, which can affect the kinetic performance and cycle performance. The smaller the n value, the shorter the path for lithium ions to enter the interior of the anode material particles from the electrolyte and complete the intercalation and deintercalation, which can reduce diffusion resistance and increase the contact area between the anode and the electrolyte, providing more lithium-ion intercalation active sites and improving the interfacial charge transfer rate. However, it will also increase the side reactions with the electrolyte and deteriorate the cycle performance of the battery. By matching and controlling the α value, a denser SEI film is formed on the anode, reducing the side reactions between the anode and the electrolyte. Controlling n and a to satisfy the above relationship can improve the transport efficiency of lithium ions in the negative electrode, reduce the side reactions between the electrolyte and the negative electrode, and thus improve the fast charging performance and cycle stability of the battery.

[0107] The value of n can be controlled by at least one of the following process parameters: graphitization temperature, grinding conditions, such as the grinding ball ratio; grinding speed, time, etc.

[0108] For example, a×n is an interval range formed by any two of the following values: 0.00075μm, 0.001μm, 0.005μm, 0.01μm, 0.05μm, 0.1μm, 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or above.

[0109] In some implementations, 0.5μm≤nμm≤5μm is used to shorten the path for lithium ions to enter the anode material particles from the electrolyte and complete the insertion / extraction process, thereby reducing diffusion resistance. At the same time, it reduces the contact area between the anode and the electrolyte, reducing side reactions between them, which is more conducive to balancing the battery's fast charging performance and cycle stability.

[0110] This application does not limit the detection method for the value of n; conventional methods in the art can be used for detection. For example, the following detection method can be used:

[0111] 1) Use a battery charging and discharging device to discharge the battery under test. Discharge conditions: current 0.3C, discharge to the lower limit voltage 2.5V; disassemble the battery, take out the negative electrode sheet, soak the negative electrode sheet in DMC (dimethyl carbonate) at room temperature for 4 hours, take it out and vacuum dry it at 60℃ for 12 hours, scrape off the powder to obtain negative electrode material powder.

[0112] 2) Use a laser particle size distribution measuring instrument (Mastersizer 3000) to test the negative electrode material powder (refer to GB / T19077-2016 for specific steps), obtain the frequency distribution curve, and read the particle size value corresponding to the intersection of the curve and the horizontal axis. The smallest of these particle size values ​​is the n value.

[0113] In some embodiments, the electrolyte further includes a solvent, which includes at least one of carboxylic acid esters and carbonates.

[0114] In some embodiments, the carboxylic acid ester includes at least one of ethyl acetate, ethyl propionate, propyl acetate, methyl propionate, and propyl propionate.

[0115] In some embodiments, the solvent includes a carboxylic acid esters, and the a% range is 0.0015% to 3.5%. Carboxylic acid esters have low viscosity, and controlling the a% value within this range allows the cyclic sulfate esters to better participate in the formation of the SEI film, providing better interface protection for the negative electrode, reducing side reactions between the electrolyte and the negative electrode, and improving cycle performance. Simultaneously, it avoids introducing excessive impurities that could increase impedance, thus facilitating a balance between battery cycle performance and fast-charging performance.

[0116] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the carboxylic acid ester is 5% to 70%, such as within the range formed by any two values ​​of 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, or above, so that the viscosity of the electrolyte is more suitable, improving the transport efficiency of lithium ions in the electrolyte, accelerating the charging rate of the battery, and at the same time, reducing the wetting of the electrode by the electrolyte, reducing the side reactions between the electrode and the electrolyte, and improving cycle performance.

[0117] In some embodiments, the carbonate contains 6 or fewer carbon atoms and 3 or more carbon atoms to make the electrolyte viscosity more suitable. This improves the lithium-ion transport efficiency in the electrolyte, accelerating the battery charging rate; and it reduces the wetting effect of the electrolyte on the electrodes, decreasing side reactions between the electrodes and the electrolyte, thus improving the battery's cycle performance. For example, the number of carbon atoms in the carbonate is within the range formed by any two of the following values: 6, 5, 4, 3, or more.

[0118] In some embodiments, the carbonate includes at least one of dimethyl carbonate, ethylene carbonate, vinylene carbonate, propylene carbonate, methyl ethyl carbonate, trimethylene carbonate, diethyl carbonate, and butene carbonate.

[0119] In some embodiments, the solvent includes carbonate, and the a% range is 0.001% to 3%. Carbonate has a high viscosity, and controlling the a% value within this range allows the cyclic sulfate to better participate in the formation of the SEI film, reducing side reactions between the electrolyte and the negative electrode, improving cycle performance, reducing impurity introduction, lowering impedance, and improving fast-charging performance.

[0120] In some embodiments, the mass percentage of the carbonate is 30% to 90%, based on the total mass of the electrolyte, such as 30%, 40%, 50%, 60%, 70%, 80%, 90%, or any two values ​​above, to make the viscosity of the electrolyte more suitable, improve the transport efficiency of lithium ions in the electrolyte, accelerate the charging rate of the battery, and at the same time, reduce the wetting of the electrode by the electrolyte, reduce the side reactions between the electrode and the electrolyte, and improve cycle performance.

[0121] In some embodiments, the solvent includes carboxylic acid esters and carbonates, with the mass ratio of carboxylic acid ester to carbonate ranging from 0.4 to 9. For example, a ratio of 0.4, 0.8, 1, 2, 3, 4, 5, 6, 7, 8, 9, or any two of these values ​​within a range makes the electrolyte viscosity more suitable, improves the lithium-ion transport efficiency in the electrolyte to accelerate the charging rate, and simultaneously suppresses excessive wetting of the electrode by the electrolyte, reduces side reactions at the electrode-electrolyte interface, and improves the battery cycle performance.

[0122] In some embodiments, the ratio of carboxylic acid ester mass to carbonate mass ranges from 1 to 9.

[0123] In one embodiment, the ratio of carboxylic acid ester mass to carbonate mass ranges from 3 to 9.

[0124] When the ratio of carboxylic acid ester mass to carbonate mass is in the range of 1 to 9, especially in the range of 3 to 9, the viscosity of the electrolyte is further improved. This not only results in faster lithium ion transport efficiency and higher charging rate in the electrolyte, but also suppresses excessive wetting of the electrode by the electrolyte, reduces side reactions at the electrode-electrolyte interface, and improves battery cycle performance. This is more conducive to balancing the battery's fast charging performance and cycle performance.

[0125] This application does not limit the detection methods for the mass percentage content of carboxylic acid esters, the mass percentage content of carbonates, and the ratio of carboxylic acid ester mass to carbonate mass. These can be obtained using conventional methods in the art. For example, the following detection methods are used:

[0126] 1) Electrolyte Collection: Use a battery charge / discharge device to discharge the battery under test. Discharge conditions: current 0.3C, discharge to the lower limit voltage 2.5V; disassemble the battery and collect the electrolyte in a glove box (H2O≤0.1ppm, O2≤0.1ppm). There are three methods for collecting the electrolyte: after opening the battery cover...

[0127] ① If there is free electrolyte, collect the electrolyte into a 5mL sample tube with a pipette and seal it with sealing tape to prevent electrolyte leakage;

[0128] ② If there is no free electrolyte, a hydraulic press (Beijing Heng'ao Technology Co., Ltd. FY-30 hydraulic press) can be used to continuously pressurize until free electrolyte appears. Collect the electrolyte into the sample tube and seal it.

[0129] ③ Add an appropriate amount of dichloromethane extractant to the battery and record the dichloromethane content. After adding dichloromethane, put the battery into an aluminum-plastic bag and seal it with a heat sealer. Transfer it to an ultrasonic oscillator and oscillate for 12 hours to allow the electrolyte in the electrode to mix thoroughly with the dichloromethane. Then, use a pipette to draw the mixture of dichloromethane and electrolyte into a 5mL sample tube and seal the sample tube with sealing glue.

[0130] 2) The collected electrolyte sample was injected into an Agilent Intuvo 9000 gas chromatograph-mass spectrometer using a microsyringe for testing. GC-MS spectra were obtained, and the specific types of carbonates and carboxylic esters contained in the electrolyte were analyzed by spectral library searching. Solutions of carbonates and carboxylic esters at different concentrations were prepared (the reagents used to prepare the solutions can be determined according to the specific types of carbonates and carboxylic esters. For example, when preparing solutions of carboxylic esters, methyl ethyl carbonate can be selected; when preparing solutions of dimethyl carbonate, ethylene carbonate, vinylene carbonate, propylene carbonate, trimethylene carbonate, diethyl carbonate, and butene carbonate, methyl ethyl carbonate can be selected; when preparing solutions of methyl ethyl carbonate, ethylene carbonate can be selected), and injected into the Agilent Intuvo 9000 gas chromatograph-mass spectrometer to obtain standard GC-MS spectra. The GC-MS spectrum of the electrolyte to be tested is compared with the standard GC-MS spectrum. Then, the content of each component is determined based on the peak area of ​​each component in the electrolyte to be tested. If the electrolyte to be tested is a finished product, the component content is determined directly by comparing the standard GC-MS spectrum. The mass percentage of carboxylic acid esters and carbonates in the solvent and their ratio (i.e., the ratio of carboxylic acid ester mass to carbonate mass) are measured.

[0131] In some embodiments, the mass percentage of electron-donating groups in the cyclic sulfate ester is 0.000008%-1.22% based on the total mass of the electrolyte.

[0132] Electron-donating groups, also known as electron-donating radicals, refer to atoms or groups of atoms capable of donating electrons to attached molecular segments (such as carbocations, unsaturated bonds, etc.). Their mechanisms of action mainly include inductive effects (+I) and conjugation effects (+C). Controlling the mass percentage of electron-donating groups in the cyclic sulfate ester within the aforementioned range can enhance the preferential reaction level of the cyclic sulfate ester on the electrode surface, promote the formation of a dense, highly ionicly conductive SEI film, and simultaneously reduce the strength of hydrogen bonding between cyclic sulfate ester molecules, thereby reducing the steric hindrance of lithium-ion transport and improving fast-charging performance. For example, electron-donating groups include at least one of alkyl, alkenyl, alkoxy, phenyl, and alkynyl groups.

[0133] For example, based on the total mass of the electrolyte, the mass percentage of electron-donating groups in the cyclic sulfate ester is within any two of the following ranges: 0.000008%, 0.00001%, 0.00005%, 0.0001%, 0.0005%, 0.001%, 0.005%, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.22%, or more.

[0134] In some embodiments, the electrolyte further includes a first additive selected from at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), and methylene disulfonate (MMDS) to preferentially react on the electrode surface, constructing a denser and more stable SEI film. This additive also optimizes the ion transport characteristics of the electrolyte, thereby improving the battery's fast-charging performance, cycle stability, and other properties.

[0135] In some embodiments, the mass percentage of the first additive is 1% to 3% based on the total mass of the electrolyte, such as a range formed by any two values ​​of 1%, 1.5%, 2%, 2.5%, 3% or more.

[0136] In some embodiments, the electrolyte further includes lithium salt; based on the total mass of the electrolyte, the mass percentage of the lithium salt is 5% to 20%, such as a range formed by any two values ​​of 5%, 8%, 10%, 12%, 15%, 18%, 20% or more.

[0137] In some embodiments, the lithium salt is selected from at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

[0138] In some embodiments, the battery cell includes a positive electrode sheet, the positive electrode sheet includes a positive current collector and a positive electrode material layer disposed on at least one side of the positive current collector, the positive electrode material layer includes a positive electrode material, the positive electrode material includes a positive electrode active material, and the positive electrode active material includes at least one of lithium iron phosphate and ternary materials.

[0139] In some embodiments, the positive electrode active material includes lithium iron phosphate; at least one of R1 to R4 is selected from hydrogen atom, -CH3, -C2H5, -C3H7, -CH=CH2, -CH2-CH=CH2, -CH=CH-CH3, -C≡CH, -CH2-C≡CH, -C≡C-CH3, phenyl, -O-CH3, -O-C2H5, or -O-C3H7. All of the above functional groups are electron-donating groups, also known as electron-donating groups, which refer to atoms or groups of atoms that have the ability to donate electrons to molecular segments (such as carbocations, unsaturated bonds, etc.) attached to them. Their mechanisms of action mainly include inductive effects (+I) and conjugation effects (+C). Lithium iron phosphate has a low potential. When at least one of R1 to R4 is selected from the above functional groups, it can not only reduce the oxidation potential of the electrolyte and form an interfacial protective film on the surface of lithium iron phosphate, reducing the risk of Fe element dissolution in lithium iron phosphate and improving the cycle performance of the battery, but also these functional groups have short chains and have little impact on the viscosity of the electrolyte, making it easier for the electrolyte to transport ions, which is beneficial to improving the fast charging performance of the battery.

[0140] The chemical formula of the lithium iron phosphate is Li a FePO4, wherein 0.9 ≤ a ≤ 1.1 (e.g., a is 0.9, 1, 1.1, or any range formed by two of the above values). Lithium iron phosphate may or may not contain doping elements; this application does not limit the types of doping elements in lithium iron phosphate. In some embodiments, the doping elements in lithium iron phosphate include, but are not limited to, at least one of V, Zr, Al, Sr, Mg, Ti, Nb, Mn, Ni, Co, Cr, Cu, Bi, Sb, F, N, and Cl. This application does not limit the content of doping elements in lithium iron phosphate. In some embodiments, the mass content of the doping element in the lithium iron phosphate is selected to be 300-30000 ppm, such as 300 ppm, 500 ppm, 1000 ppm, 5000 ppm, 10000 ppm, 12000 ppm, 15000 ppm, 17000 ppm, 20000 ppm, 22000 ppm, 25000 ppm, 27000 ppm, 30000 ppm or any two of the above values ​​forming a range.

[0141] In some embodiments, the lithium iron phosphate is coated with a carbon layer, which can not only improve the electronic conductivity and ion transport efficiency of the lithium iron phosphate, reduce electrode polarization, but also inhibit the aggregation and grain growth of the lithium iron phosphate particles during charge and discharge, thereby improving the rate performance and cycle stability of the battery. In some of these embodiments, based on the total mass of the lithium iron phosphate (including the mass of the carbon layer), the mass content of the carbon layer is selected to be 1% - 3%, such as 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3% or any range formed by any two of the above values.

[0142] In some embodiments, the chemical formula of the lithium nickel cobalt manganese oxide is Li q Ni x Co y Mn 1-x-y O2, where 0.9 ≤ q ≤ 1.1; 0 < x < 1; 0 < y < 1; x + y < 1. For example, q is 0.9, 1, 1.1 or any range formed by any two of the above values; x is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or any range formed by any two of the above values; y is 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, 0.24, 0.26, 0.28, 0.3, 0.32, 0.35 or any range formed by any two of the above values; x + y is 0.15, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95 or any range formed by any two of the above values.

[0143] The lithium nickel cobalt manganese oxide may either contain no doping elements or contain doping elements. The present application places no limitation on the types of doping elements in the lithium nickel cobalt manganese oxide. In some embodiments, the doping elements in the lithium nickel cobalt manganese oxide include but are not limited to at least one of Zr, Mo, B, Al, W, Sr, Mg, Ca, Ta, Ti, Nb, Y, Ta, Sb, S, Na. The present application places no limitation on the content of the doping elements in the lithium nickel cobalt manganese oxide. In some embodiments, the mass content of the doping elements in the lithium nickel cobalt manganese oxide is selected to be 300 - 30000 ppm, such as 300 ppm, 500 ppm, 1000 ppm, 5000 ppm, 10000 ppm, 12000 ppm, 15000 ppm, 17000 ppm, 20000 ppm, 22000 ppm, 25000 ppm, 27000 ppm, 30000 ppm or any range formed by any two of the above values.

[0144] In some embodiments, the ternary material includes lithium nickel cobalt manganese oxide (NCM), the surface of which is coated with at least one of alumina, zirconium oxide, titanium dioxide, zinc oxide, magnesium oxide, aluminum fluoride, lithium fluoride, polypyrrole, tungsten oxide, and boron oxide. This can reduce side reactions between the NCM and the electrolyte and improve battery cycle life by constructing a dense and stable physical barrier layer. In some embodiments, the thickness of the coating layer is 10~100 nm, such as within the range of any two values ​​of 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or higher.

[0145] This application does not limit the preparation method of the lithium iron phosphate. Those skilled in the art can prepare the lithium iron phosphate using conventional techniques, or it can be obtained commercially. For example, the preparation method of the lithium iron phosphate includes the following steps:

[0146] The lithium source, iron source, and phosphorus source precursors, along with element M precursor (element M is a dopant element if it is present), and carbon source (if a carbon coating layer is required), are mixed uniformly to obtain a mixture. This mixture is then dispersed in a solvent and wet-milled, followed by spray drying. The resulting powder is typically calcined once in an inert atmosphere (such as nitrogen (N2) or argon (Ar) atmosphere), then pulverized. It is then sintered a second time in an inert atmosphere or a reducing atmosphere (such as nitrogen (N2) or argon (Ar) atmosphere, or a mixture of hydrogen and nitrogen and / or argon) atmosphere, followed by pulverization, to obtain the lithium iron phosphate.

[0147] In some embodiments, the solvent includes at least one of water, methanol, and ethanol.

[0148] In some embodiments, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate, lithium oxalate, lithium dihydrogen phosphate, lithium citrate, and lithium acetate.

[0149] The phosphorus source includes at least one of ammonium dihydrogen phosphate, ammonium phosphate, and lithium dihydrogen phosphate.

[0150] The iron source includes at least one of ferrous oxalate, ferric hydroxide, ferrous hydroxide, ferric phosphate, ferrous phosphate, ferric acetate, ferrous acetate, ferric carbonate, ferrous carbonate, ferric oxide, ferric oxide, and ferric oxalate.

[0151] It should be noted that the phosphorus source and the iron source can be the same, such as iron phosphate.

[0152] The carbon source includes at least one of glucose, sucrose, and polyethylene glycol.

[0153] The precursor of element M can be at least one of the oxides, compounds, or salts of element M, and there is no specific limitation thereto. For example, when M is Ti, the precursor of element M can be at least one of titanium dioxide or tetrabutyl titanate.

[0154] In some embodiments, the wet grinding is wet ball milling, the ball milling time is 2-4 hours, and the rotation speed is 1000-1500 r / min.

[0155] In some embodiments, the spray drying pressure is 0.4~0.7 MPa, the atomizer speed is 8000~15000 r / min, the inlet temperature is 180~250℃, and the outlet temperature is 70~100℃.

[0156] In some embodiments, the primary calcination temperature is 780~810℃, the heating rate is 4~6℃ / min, and the holding time is 8~12h; the secondary calcination temperature is 760~790℃, the heating rate is 4~6℃ / min, and the holding time is 6~8h.

[0157] In some embodiments, the pulverization is carried out by air jet pulverization, and the pressure of the air jet pulverization is 0.5~1.2MPa.

[0158] This application does not limit the preparation method of the lithium nickel cobalt manganese oxide. Those skilled in the art can prepare the lithium nickel cobalt manganese oxide using conventional techniques, or it can be obtained commercially. For example, the preparation method of the lithium nickel cobalt manganese oxide includes the following steps:

[0159] Nickel, cobalt, and manganese sources are mixed in the molar ratios of the chemical formula of the ternary material, dissolved in deionized water, and dispersed to prepare a mixed solution. The obtained mixed solution, precipitant, and complexing agent are mixed and subjected to a co-precipitation reaction. After drying, a precursor is obtained. The lithium source and the obtained precursor are mixed and sintered in an oxygen-containing atmosphere, then pulverized to obtain the ternary material.

[0160] The nickel source includes, but is not limited to, at least one of nickel chloride, nickel sulfate, nickel nitrate, nickel acetate, nickel carbonate, and nickel hydroxide; the cobalt source includes, but is not limited to, at least one of cobalt chloride, cobalt sulfate, cobalt nitrate, cobalt acetate, cobalt carbonate, and cobalt hydroxide; the manganese source includes, but is not limited to, at least one of manganese chloride, manganese sulfate, manganese nitrate, manganese acetate, manganese carbonate, and manganese hydroxide; the lithium source includes, but is not limited to, at least one of lithium carbonate, lithium hydroxide, lithium oxide, and lithium acetate; the precipitant includes, but is not limited to, at least one of sodium hydroxide and potassium hydroxide; and the complexing agent includes, but is not limited to, ammonia.

[0161] In the coprecipitation method, the conditions for the coprecipitation reaction are: reaction temperature 110~120℃, reaction time 20~36h, pH value 6~8; the conditions for the sintering treatment are: sintering temperature 800~950℃, sintering time 6~12h.

[0162] In some embodiments, the molar amount of the complexing agent is 0.5 to 1.5 times the total molar amount of the Ni source, Co source and Mn source.

[0163] In some embodiments, the complexing agent is added in solution form at a concentration of 0.2 to 1.0 mol / L.

[0164] In some embodiments, during the preparation of the precursor, it is necessary to control the pH value of the system within the range of 6 to 8, which can be achieved by adding the alkaline solution.

[0165] In some embodiments, the alkaline solution contains 1.0% to 4.0% by mass of alkali.

[0166] In some implementations, the complexing agent is introduced by dropwise addition.

[0167] In some implementations, the alkaline solution is introduced dropwise.

[0168] In some implementations, the amounts of the precursor and the Li salt satisfy the following ratio: amount of Li element: sum of amounts of Ni, Co and Mn elements = (1.01~1.10):1.

[0169] In some implementations, the pulverizing method includes ball milling.

[0170] Lithium nickel cobalt manganese oxide can also be doped as needed, specifically as follows: When the precursor and Li salt are mixed and dispersed, a salt or oxide containing the corresponding dopant element is added simultaneously. For example, when doping Zr, at least one of zirconium dioxide, zirconium nitrate, etc., can be added; when doping B, at least one of boron trioxide, boric acid, etc., can be added; when doping W, at least one of tungsten trioxide, tungsten nitrate, etc., can be added. The dopant element source includes, but is not limited to, at least one of the following: chloride, sulfate, nitrate, acetate, carbonate, and hydroxide species of the dopant element.

[0171] Lithium nickel cobalt manganese oxide can also be coated as needed. Specifically, a dry coating method (high-temperature solid-state method) is used to coat the surface of the lithium nickel cobalt manganese oxide particles with a coating material, so that the surface of the lithium nickel cobalt manganese oxide particles is partially or completely covered with a coating layer formed by the coating material. For example, dry coating includes the following steps:

[0172] The obtained ternary material was aluminized using an ALD atomic deposition instrument with oxide powder as the coating material to obtain a ternary material with oxide coating on the surface. The oxide powder included at least one of alumina powder and zirconium oxide powder.

[0173] In some embodiments, the negative electrode active material further includes a silicon-based material, and the a% range is 0.0015% to 3.5%. During the charging and discharging process, the silicon particles will pulverize and break due to drastic volume expansion and contraction. New SEI films will continuously form on the surface of the broken silicon particles, continuously consuming active lithium. By controlling the a% value within the above range, the cyclic sulfate ester can better participate in the formation of the SEI film, reduce the side reactions between the electrolyte and the negative electrode, improve cycle performance, and at the same time avoid introducing too many impurities that would lead to increased impedance.

[0174] In some embodiments, the battery cell includes a positive tab, and the ratio of the width of the positive tab to the width of the battery cell is in the range of 0.05 to 0.5, such as the ratio being 0.05, 0.1, 0.2, 0.3, 0.4, 0.5 or any two of the above values ​​forming a range.

[0175] In some embodiments, the battery cell includes a negative electrode tab, and the ratio of the width of the negative electrode tab to the width of the battery cell is in the range of 0.05 to 0.5, such as the ratio being 0.05, 0.1, 0.2, 0.3, 0.4, 0.5 or any two of the above values ​​forming a range.

[0176] In some embodiments, the battery cell includes a positive tab and a negative tab;

[0177] The ratio of the width of the positive tab to the width of the battery cell, and / or the ratio of the width of the negative tab to the width of the battery cell, is 0.9 to 1. When the positive / negative tabs meet the above conditions, their size is relatively large, and they can provide a larger current-carrying cross-sectional area, which can improve the current-carrying capacity and thus improve fast charging performance.

[0178] A tab refers to a structural component that is located on one side of the positive / negative current collector and is separately or integrally formed with the current collector. It is electrically connected to the current collector to conduct current through the corresponding current collector. The material of the positive tab can be, but is not limited to, aluminum or aluminum alloy. The material of the negative tab can be, but is not limited to, copper or copper alloy.

[0179] This application does not limit the detection method for the width of the positive and negative tabs and the width of the battery cell. They can be detected by conventional methods in the field. For example, they can be measured by a micrometer.

[0180] The negative electrode current collector may include negative electrode current collectors conventionally used in the art. For example, the negative electrode current collector includes at least one of copper foil, chromium foil, nickel foil, and titanium foil.

[0181] In some implementations, the graphite content in the negative electrode material is 95% to 98% by mass.

[0182] In some embodiments, the negative electrode material further includes a conductive agent. The conductive agent in the negative electrode material is used to provide conductivity, and any conductive agent can be used without particular limitation, as long as it has suitable electronic conductivity and does not significantly cause adverse chemical changes in the battery. Exemplarily, the conductive agent in the negative electrode material includes, but is not limited to, at least one of carbon nanotubes, carbon black, graphite, carbon fibers, activated carbon, mesoporous carbon, and fullerenes, wherein carbon fibers are, for example, carbon nanofibers; carbon black is, for example, SP (Super P), acetylene black, Ketjen black, etc. In some embodiments, the mass percentage of the conductive agent in the negative electrode material is 0.2% to 1.5%.

[0183] In some embodiments, the negative electrode material further includes a binder. The binder in the negative electrode material is used to improve the adhesion between the negative electrode active material particles and the adhesion between the negative electrode active material and the negative electrode current collector. Any binder can be used without particular limitation, as long as it has suitable adhesive properties and does not significantly cause adverse chemical changes in the battery. Exemplary binders in the negative electrode material include, but are not limited to, at least one of carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl butyral, and aqueous acrylic resin. In some embodiments, the binder in the negative electrode material has a mass percentage of 1% to 3%.

[0184] In some embodiments, the negative electrode material further includes a dispersant. The dispersant in the negative electrode material is used to improve the dispersibility of the negative electrode active material. Any dispersant can be used without particular limitation, as long as it has suitable dispersibility and does not significantly cause adverse chemical changes in the battery. Exemplary examples include, but are not limited to, at least one of carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and hydrogenated styrene-butadiene rubber (H-SBR).

[0185] In some embodiments, the mass percentage of dispersant in the negative electrode material is 0.3% to 1.5%, such as 0.3%, 0.5%, 0.7%, 1%, 1.2%, 1.5%, or any range formed by any two of the above values.

[0186] The negative electrode sheet can be prepared according to conventional methods in the art. For example, the preparation method of the negative electrode sheet includes the following steps: mixing a negative electrode active material, a conductive agent, a binder, a dispersant and a solvent to obtain a negative electrode slurry; coating the negative electrode slurry onto at least one side of a negative electrode current collector, drying it and then rolling and cutting it to obtain a negative electrode sheet.

[0187] In some embodiments, the areal density of the negative electrode is 150-260 g / m³. 2 The compacted density is 1.4-1.8 g / cm³. 3 .

[0188] The positive current collector may include positive current collectors conventionally used in the art. For example, the positive current collector includes at least one of aluminum foil and composite foil. The composite foil includes a middle high-density layer and metal layers disposed on both sides of the polymer layer. The polymer layer includes polymer materials, including at least one of polyamide (PA), polyterephthalate, polyimide (PI), polyethylene (PE), polypropylene (PP), polystyrene (PPE), polyvinyl chloride (PVC), aramid, acrylonitrile-butadiene-styrene copolymer (ABS), polybutylene terephthalate (PET), poly(p-phenylene terephthalamide) (PPTA), polypropylene (PPE), polyoxymethylene (POM), epoxy resin, phenolic resin, polytetrafluoroethylene (PTEE), polyvinylidene fluoride (PVDF), silicone rubber, polycarbonate (PC), polyvinyl alcohol (PVA), polyethylene glycol (PEG), cellulose, starch, protein, their derivatives, their crosslinks, and their copolymers. The metal layers may include at least one of aluminum, copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys.

[0189] In some embodiments, the positive electrode material contains 95% to 98% by mass of the positive electrode active material.

[0190] In some embodiments, the cathode material further includes a conductive agent. The conductive agent in the cathode material is used to provide conductivity, and any conductive agent can be used without particular limitation, as long as it has suitable electronic conductivity and does not significantly cause adverse chemical changes in the battery. Exemplarily, the conductive agent includes, but is not limited to, at least one of carbon nanotubes, carbon black, graphite, activated carbon, carbon fibers, mesoporous carbon, and fullerenes, wherein carbon fibers are, for example, carbon nanofibers; and carbon black is, for example, acetylene black, SP, Ketjen black, etc. In some embodiments, the conductive agent in the cathode material has a mass percentage content of 0.1% to 2%.

[0191] In some embodiments, the positive electrode material further includes a binder. The binder in the positive electrode material is used to improve the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode current collector. Any binder can be used without particular limitation, as long as it has suitable adhesive properties and does not significantly cause adverse chemical changes in the battery. Exemplarily, the binder includes, but is not limited to, fluorinated polyolefin binders, including, but not limited to, polyvinylidene fluoride (PVDF), PVDF copolymers, or their modified derivatives (e.g., modified with carboxylic acids, acrylic acid, acrylonitrile, etc.).

[0192] In some embodiments, the binder in the positive electrode material has a mass percentage content of 0.2% to 3%.

[0193] The positive electrode sheet can be prepared according to conventional methods in the art. For example, the preparation method of the positive electrode sheet includes the following steps: mixing positive electrode active material, conductive agent, binder and solvent to obtain positive electrode slurry; coating the positive electrode slurry onto at least one side of the positive electrode current collector, drying and then rolling and cutting to obtain the positive electrode sheet.

[0194] In some implementations, for lithium iron phosphate batteries, the areal density of the positive electrode is 350-500 g / m³. 2 The compacted density is 2.45-2.78 g / cm³. 3 For ternary lithium batteries, the areal density of the positive electrode is 200-700 g / m³. 2 The compacted density is 3.2-3.8 g / cm³. 3 .

[0195] According to a second aspect of this application, an electrical device is also provided, comprising the battery. The battery serves as a power source for the electrical device.

[0196] The term "electrical device" refers to any device that can utilize electrical energy and convert it into mechanical energy, thermal energy, light energy, or one or more other energy forms, such as electric motors, electric heaters, and electric light sources. Specifically, it can include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, and energy storage systems. Mobile devices can include mobile phones, laptops, drones, robot vacuum cleaners, and e-cigarettes; electric vehicles can include pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, and electric trucks.

[0197] The present application is further illustrated below with specific embodiments:

[0198] Examples 1-35 and Comparative Examples 1-4

[0199] A battery is provided, comprising the following steps:

[0200] (1) Preparation of positive electrode

[0201] (1.1) Preparation of positive electrode active material (i.e., positive electrode main material)

[0202] The types of positive electrode active materials are shown in Table 1.

[0203] If the positive electrode active material is lithium iron phosphate, its preparation method is as follows: Lithium carbonate precursor, iron phosphate, titanium dioxide, vanadium oxide, and carbon source (glucose and PEG1500, mass ratio 2:1, where 1500 refers to the molecular weight of PEG) are mixed evenly. The resulting mixture is dispersed in water and wet-milled for 3 hours at a speed of 1200 r / min. Spray drying is then performed at a pressure of 0.5 MPa, an atomizer speed of 10000 r / min, an inlet temperature of 200℃, and an outlet temperature of 90℃. The resulting powder is then calcined once under a nitrogen atmosphere at a sintering temperature of 800℃ and a heating rate of 5℃ / min. The temperature was maintained for 10 hours; after pulverization, a second calcination was performed under a nitrogen atmosphere at a temperature of 770℃, a heating rate of 5℃ / min, and a holding time of 6 hours; then pulverization was performed again to obtain lithium iron phosphate, which is the positive electrode active material. All pulverization was carried out using air jet milling at a pressure of 1 MPa. The ratio of Li to Fe in the lithium carbonate and iron phosphate was 1.05:1 (molar ratio); the molar ratio of Ti to V in the titanium oxide and vanadium oxide was 1:1. Based on the total mass of the obtained lithium iron phosphate material, the sum of the mass percentages of Ti and V was 5000 ppm; based on the total mass of the obtained lithium iron phosphate material, the mass percentage of carbon in the carbon source was 1%.

[0204] If the positive electrode active material is a ternary material, its preparation method is as follows: Nickel sulfate, cobalt sulfate, and manganese sulfate are mixed according to the molar ratio in the chemical formula of the ternary material (see Table 1), dissolved in deionized water, dispersed, and a mixed solution is prepared; the obtained mixed solution, precipitant sodium hydroxide, and complexing agent ammonia water (concentration 0.5 mol / L) are mixed and subjected to a co-precipitation reaction at a reaction temperature of 110℃ for 24 h, pH value of 8, and the molar amount of NH3 in the ammonia water is 1 times the total molar amount of nickel sulfate, cobalt sulfate, and manganese sulfate. After drying, a precursor is obtained; the lithium source and the obtained precursor are mixed and sintered in an oxygen-containing atmosphere, pulverized, sintered at a temperature of 850℃ for 10 h.

[0205] (1.2) Preparation of positive electrode sheet

[0206] The positive electrode active material, conductive carbon black SP, and binder PVDF are mixed in a mass ratio of 97:1:2. N-methylpyrrolidone (NMP) is added and the mixture is dispersed evenly to obtain a positive electrode slurry. The positive electrode slurry is coated on both sides of the positive electrode current collector aluminum foil, dried, cold-pressed, and slit to obtain a positive electrode sheet.

[0207] (2) Preparation of negative electrode

[0208] (2.1) Preparation of negative electrode active material

[0209] The soft carbon precursor and hard carbon precursor were mixed according to the mass ratio in Table 1, and then mixed and dispersed with the dopant element source by mechanical grinding.

[0210] The heat treatment process consists of two steps: first, carbonization; and second, high-temperature graphitization.

[0211] Among them, the soft carbon precursor is needle coke;

[0212] The hard carbon precursor is phenolic resin;

[0213] The types of doping elements are shown in Table 1. If the doping element is N, then the doping element source is melamine; if the doping element is S, then the doping element source is benzothiophene; if the doping element is B, then the doping element source is boron oxide; if the doping element is P and N, then the doping element source is melamine and phosphoric acid; if the doping element is Si, then the doping element source is silicon dioxide.

[0214] Based on the total mass of the obtained graphite, the mass percentage of doped elements is shown in Table 1;

[0215] Dispersion requirements: The grinding media is zirconia balls, the ball-to-material ratio (mass ratio) is shown in Table 1, the rotation speed is shown in Table 1 (planetary type), the grinding time is 1 hour, and the inert atmosphere (N2) is used for protection;

[0216] Carbonization requirements: Carbonization treatment at 1000℃ for 2 hours under an inert atmosphere (nitrogen) protection;

[0217] High-temperature graphitization satisfies the following conditions: under an inert atmosphere (argon), the carbon atoms in the carbonized material are held at the graphitization temperature for 1 hour to rearrange and form a highly ordered graphite crystal structure, while simultaneously achieving stable solid solution of the doped atoms. The graphitization temperatures are shown in Table 1.

[0218] (2.2) Preparation of negative electrode

[0219] The negative electrode active material, conductive agent SP, binder SBR, and dispersant CMC are mixed in a mass ratio of 95.5:2:1.5:1. Deionized water is added and the mixture is dispersed evenly to obtain a negative electrode slurry. The negative electrode slurry is coated on both sides of the negative electrode current collector copper foil, dried, rolled, and cut to obtain a negative electrode sheet.

[0220] (3) Preparation of electrolyte

[0221] An organic solvent was obtained by mixing carboxylic acid esters and carbonates. Cyclic sulfates, vitamin C, FEC, and MMDS were added to the organic solvent. Then, fully dried lithium salt LiPF6 was added to dissolve the solvent to obtain an electrolyte. The carboxylic acid ester was ethyl acetate; the carbonate was a mixture of ethylene carbonate and methyl ethyl carbonate in a mass ratio of 1.5:1. The types of cyclic sulfates are shown in Table 1, and the a values ​​are shown in Table 2. Based on the total mass of the electrolyte, the mass percentages of carboxylic acid esters and lithium salts are shown in Table 1. The mass percentage of vitamin C was 1.5%, the mass percentage of FEC was 1%, and the mass percentage of MMDS was 0.8%.

[0222] (4) Preparation of the diaphragm:

[0223] The selected membrane is a commercially available PE base membrane with alumina ceramic layers on both sides. The membrane thickness is 9.5 μm, and the ceramic layer thickness is 1.5 μm.

[0224] (5) Assembly and formation

[0225] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. They are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, the battery is obtained. The formation process is as follows:

[0226] If the positive electrode active material is lithium iron phosphate, then the formation process is as follows: after being placed at 45°C for 24 hours, it is placed in a glass fixture with a fixture pressure of 0.5MPa, left to stand for 10 minutes, charged at a rate of 0.05 for 120 minutes, left to stand for 10 minutes, and charged at a rate of 0.33 for 120 minutes to complete the formation.

[0227] If the positive electrode active material is ternary, then the formation process is as follows:

[0228] After standing at 25℃ for 24 hours, place the glass in the glass clamp with a clamping pressure of 0.4-0.6MPa.

[0229] 1) Let stand at 45℃ for 10 minutes;

[0230] 2) Charge at a rate of 0.05C, with a cutoff voltage of 3.4V;

[0231] 3) Let it stand for 10 minutes;

[0232] 4) Charge at a rate of 0.05C, with a cutoff voltage of 3.75V;

[0233] 5) End.

[0234] Table 1

[0235]

[0236] Continued from Table 1

[0237]

[0238] The performance of the batteries in each embodiment and comparative example was tested as follows:

[0239] (1) Fast charging test

[0240] Obtain a three-electrode soft-pack battery. Preparation of the three-electrode copper wire: Wrap the copper wire around the fixed copper foil surface, evenly adhering both ends of the wire to the foil. With the end of the foil (the neatly cut end of the double-sided tape) facing down, roll it into a semi-circle and place it in a 500mL beaker. Add sulfuric acid (a 1:1 volume ratio of pure water and 98% concentrated sulfuric acid) to immerse the wire, ensuring the immersion depth exceeds the top of the double-sided tape by 12mm. Immerse in the sulfuric acid for 4 hours, then remove. Clean the bottom immersed area with anhydrous ethanol, let it stand for 5 minutes, and then proceed with subsequent processing. Prepare 1.2mol / L dilute hydrochloric acid (37wt% concentrated hydrochloric acid diluted 10 times with deionized water). Immerse the copper foil with the attached copper wire in the dilute hydrochloric acid and acid wash for 15 minutes. Remove the acid-washed copper wire and place it in anhydrous ethanol, then clean it in an ultrasonic cleaner for 10-15 minutes. Transfer the copper wire to a room with humidity less than 1.2% for later use. Assembly and Formation: Prepare the required positive and negative electrode sheets and copper wires. Stack the electrode sheets in the following order: negative electrode sheet, separator, copper wire, separator, positive electrode sheet, separator, negative electrode sheet. The positive electrode sheet should be placed in the center of the negative electrode sheet, and the negative electrode sheets should be completely aligned. After stacking, peel off the outermost negative electrode sheet. Position the end of the copper wire (processed end) 32±5mm from the top edge of the cell and 40.5±5mm to the left and right. Add another 81×81mm² separator, then place the negative electrode sheet on top. After arranging the copper wire, the copper wire should be 11.5mm from each side of the electrode tab. After the separator automatically winds up one and a half times, roll it up and apply adhesive to fix the separator in place. The outermost separator should be tightly wrapped without any obvious looseness, and at least 110mm of copper wire should be exposed. The copper wire is transferred using a soldering iron (soldering temperature 300℃, time 5~10s). During ultrasonic welding, the battery cell is handled gently to prevent the copper wire from breaking during transport, resulting in a bare battery cell. The bare battery cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, and formation, the formation process follows the steps given above. Then, the following steps are performed: the battery is charged at a constant current of 0.33C to the upper limit voltage (3.65V for lithium iron phosphate batteries and 4.25V for ternary batteries), charged at a constant voltage until the current is less than or equal to 0.05C, and discharged at 0.33C to the lower limit voltage. Repeat the above steps 3 times, and take the capacity discharged in the third cycle as the battery discharge capacity C; let it stand for 10 minutes, discharge at 1C to 2.5V, let it stand for 10 minutes, and charge at 0.33C to 10% SOC; then charge at a high rate of 8C with constant current, and then gradually reduce the charging rate in 0.2C increments until it drops to 0.4C. The cutoff condition for each charge is to charge to the upper limit voltage (3.65V for lithium iron phosphate batteries and 4.25V for ternary batteries) or the auxiliary voltage of 0mV; record the charging time between 10% SOC (10%×C) and 80% SOC (80%×C).

[0241] (2) Loop testing

[0242] Place the test subject in a 25℃ incubator and perform the following operations:

[0243] Charge at 0.33C to the upper limit voltage (3.65V for lithium iron phosphate batteries and 4.25V for ternary batteries), charge at constant voltage to the cutoff current of 0.05C, let stand for 30 minutes, and discharge at 0.33C to the lower limit voltage of 2.5V.

[0244] Repeat the above operation for 3 cycles. Use the discharge capacity of the third cycle as the battery's rated capacity, and then proceed with the following steps:

[0245] 1) Charge at a constant current rate of 1C to the upper limit voltage (3.65V for lithium iron phosphate batteries and 4.25V for ternary batteries), and charge at a constant voltage until the current drops to 0.05C;

[0246] 2) Let it stand for 20 minutes;

[0247] 3) Discharge to 2.5V at a 1C rate;

[0248] 4) Let it stand for 20 minutes.

[0249] Perform cycle tests according to steps 1)-4) until the capacity of the lithium-ion battery is less than 80% of the initial capacity, and record the number of cycles.

[0250] The test results are shown in Table 2.

[0251] Table 2

[0252]

[0253] The batteries prepared in the various embodiments of this application have a charging time of less than 18.7 minutes and a cycle count of more than 2000 cycles, which shows that the batteries containing this application have both excellent fast charging performance and cycle performance.

[0254] As can be seen from the comparison of Examples 1-8 with Examples 12-13 and 29, Examples 14-15 with Examples 9-11 and 30, and Examples 17-19 with Example 20, when the values ​​of a, b, and c meet the preferred range described in this application, it is more conducive to the balance between fast charging performance and cycle performance.

[0255] Comparing Examples 1-8 with Examples 14-15, Examples 12-13 and 29 with Examples 9-11 and 30, and Examples 17-21 with Example 22, it can be seen that when the battery satisfies 0.04 cp / nm≤a×b / c≤12 cp / nm, it is more conducive to balancing fast charging performance and cycle performance.

[0256] As shown in Comparative Examples 1 to 4, even if the values ​​of a, b, and c are within appropriate ranges, the fast charging performance and / or cycle performance of the battery deteriorates when the value of a×b / c exceeds the range of 0.0015cp / nm to 38cp / nm.

[0257] As can be seen from the comparison of Examples 28 to 31, when the battery satisfies 0.00075μm≤a×n≤15μm, the battery has better fast charging performance and cycle performance.

[0258] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this article and are not intended to limit the scope of protection of this article. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this article without departing from the essence and scope of the technical solutions of this article.

Claims

1. A battery, characterized in that, This includes the battery cell, which consists of a negative electrode and an electrolyte. The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one side of the negative electrode current collector. The negative electrode material layer includes a negative electrode material, the negative electrode material includes a negative electrode active material, and the negative electrode active material includes graphite. The electrolyte comprises cyclic sulfates; The battery satisfies the following condition: 0.0015cp / nm ≤ a×b / c ≤ 38cp / nm; Where a% represents the mass percentage of cyclic sulfate esters in the electrolyte. b represents the viscosity of the electrolyte at 25°C, measured using a Cambridge viscometer, and the unit is cp. c represents the interlayer spacing of graphite, in nm; 0.001%≤a%≤3.5%； 0.4cp≤b≤4cp; 0.336nm≤c≤0.38nm.

2. The battery as described in claim 1, characterized in that, 0.04cp / nm≤a×b / c≤12cp / nm.

3. The battery as described in claim 1, characterized in that, The cyclic sulfates include compounds represented by Formula I; In Formula I, R1, R2, R3 and R4 each independently include the groups shown in Formula II, hydrogen atoms, alkyl groups of 1 to 6 carbon atoms, halogen atoms, haloalkyl groups of 1 to 3 carbon atoms, alkoxy groups of 1 to 3 carbon atoms, haloalkoxy groups of 1 to 3 carbon atoms, alkenyl groups of 2 to 6 carbon atoms, alkynyl groups of 2 to 6 carbon atoms, aromatic groups, ester groups, cyano groups or sulfonic acid groups; In Formula II, R5 and R6 each independently include the group shown in Formula III, a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, a halogen atom, a haloalkyl group of 1 to 3 carbon atoms, an alkoxy group of 1 to 3 carbon atoms, a haloalkoxy group of 1 to 3 carbon atoms, an alkenyl group of 2 to 6 carbon atoms, an alkynyl group of 2 to 6 carbon atoms, an aromatic group, an ester group, a cyano group, or a sulfonic acid group. In Formula III, R7 and R8 each independently include a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, a halogen atom, a haloalkyl group of 1 to 3 carbon atoms, an alkoxy group of 1 to 3 carbon atoms, a haloalkoxy group of 1 to 3 carbon atoms, an alkenyl group of 2 to 6 carbon atoms, an alkynyl group of 2 to 6 carbon atoms, an aromatic group, an ester group, a cyano group, or a sulfonic acid group. 。 4. The battery as described in claim 3, characterized in that, In Formula I, the number of sulfate groups is an integer from 2 to 4.

5. The battery as described in claim 3, characterized in that, At least one of R1 to R4 is a hydrogen atom.

6. The battery as described in claim 3, characterized in that, R1 and R3 are the same.

7. The battery as described in claim 6, characterized in that, R1 and R3 are selected from the group shown in structural formula II, hydrogen atom, alkyl group of 1 to 6 carbon atoms, halogen atom, haloalkyl group of 1 to 3 carbon atoms, alkoxy group of 1 to 3 carbon atoms, haloalkoxy group of 1 to 3 carbon atoms, alkenyl group of 2 to 6 carbon atoms, alkynyl group of 2 to 6 carbon atoms, aromatic group, ester group, cyano group or sulfonic acid group. In Formula II, R5 and R6 each independently include the group shown in Formula III, a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, a halogen atom, a haloalkyl group of 1 to 3 carbon atoms, an alkoxy group of 1 to 3 carbon atoms, a haloalkoxy group of 1 to 3 carbon atoms, an alkenyl group of 2 to 6 carbon atoms, an alkynyl group of 2 to 6 carbon atoms, an aromatic group, an ester group, a cyano group, or a sulfonic acid group. In Formula III, R7 and R8 each independently include a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, a halogen atom, a haloalkyl group of 1 to 3 carbon atoms, an alkoxy group of 1 to 3 carbon atoms, a haloalkoxy group of 1 to 3 carbon atoms, an alkenyl group of 2 to 6 carbon atoms, an alkynyl group of 2 to 6 carbon atoms, an aromatic group, an ester group, a cyano group, or a sulfonic acid group. 。 8. The battery as claimed in claim 7, characterized in that, R1 and R3 are selected from hydrogen atoms, CH3, -C2H5, -C3H7, -CH=CH2, -CH2-CH=CH2, -CH=CH-CH3, -O-CH3, -O-C2H5, -O-C3H7, -F, -Cl, -Br, -I, -CF3, CCl3, -CBr3, -C2F5, -C2Cl5, -C2Br5, -C3F7, -C3Cl7, -C3Br7, -C≡CH, -CH2-C≡CH, -C≡C-CH3, aromatic groups, or... .

9. The battery as described in claim 3, characterized in that, The cyclic sulfate ester includes at least one of the following compounds: 。 10. The battery as claimed in claim 1, characterized in that, The graphite contains a doping element selected from at least one of N, B, S, P, and Si.

11. The battery as claimed in claim 1, characterized in that, The OI value of the negative electrode material ranges from 0.5 to 40.

12. The battery as claimed in claim 1, characterized in that, n is the minimum particle size in the particle size frequency distribution curve of the negative electrode material, in μm; n and a satisfy: 0.00075μm≤a×n≤15μm.

13. The battery as claimed in claim 12, characterized in that, 0.5μm≤n≤5μm.

14. The battery as claimed in claim 1, characterized in that, The electrolyte also includes a solvent, which includes at least one of carboxylic acid esters and carbonates.

15. The battery as claimed in claim 14, characterized in that, The carboxylic acid ester includes at least one of ethyl acetate, ethyl propionate, propyl acetate, methyl propionate, and propyl propionate.

16. The battery as claimed in claim 14, characterized in that, The solvent includes carboxylic acid esters, and the a% range is 0.0015% to 3.5%.

17. The battery as claimed in claim 16, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the carboxylic acid ester is 5% to 70%.

18. The battery as claimed in claim 14, characterized in that, The carbonate contains 6 or less carbon atoms and 3 or more carbon atoms.

19. The battery as claimed in claim 14, characterized in that, The solvent includes carbonates, and the a% range is 0.001% to 3%.

20. The battery as claimed in claim 19, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the carbonate is 30% to 90%.

21. The battery as claimed in claim 14, characterized in that, The solvent includes carboxylic acid esters and carbonates, with the ratio of carboxylic acid ester mass to carbonate mass ranging from 0.4 to 9.

22. The battery as claimed in claim 1, characterized in that, Based on the total mass of the electrolyte, the mass percentage of electron-donating groups in the cyclic sulfate ester is 0.000008%-1.22%.

23. The battery as claimed in claim 1, characterized in that, The electrolyte further includes a first additive, which is selected from at least one of vinylene carbonate, fluoroethylene carbonate, vinyl sulfate, and methylene disulfonate.

24. The battery as claimed in claim 1, characterized in that, The electrolyte also includes lithium salt; based on the total mass of the electrolyte, the mass percentage of the lithium salt is 5% to 20%.

25. The battery as claimed in claim 24, characterized in that, The lithium salt is selected from at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

26. The battery as claimed in claim 3, characterized in that, The battery cell includes a positive electrode sheet, the positive electrode sheet includes a positive current collector and a positive electrode material layer disposed on at least one side of the positive current collector, the positive electrode material layer includes a positive electrode material, the positive electrode material includes a positive electrode active material, and the positive electrode active material includes at least one of lithium iron phosphate and ternary materials.

27. The battery as claimed in claim 26, characterized in that, The positive electrode active material includes lithium iron phosphate; at least one of R1 to R4 is selected from hydrogen atom, -CH3, -C2H5, -C3H7, -CH=CH2, -CH2-CH=CH2, -CH=CH-CH3, -C≡CH, -CH2-C≡CH, -C≡C-CH3, phenyl, -O-CH3, -O-C2H5 or -O-C3H7.

28. The battery as claimed in claim 26, characterized in that, The lithium iron phosphate is coated with a carbon layer. And / or, the ternary material includes lithium nickel cobalt manganese oxide, the surface of which is coated with at least one of alumina, zirconium oxide, titanium dioxide, zinc oxide, magnesium oxide, aluminum fluoride, lithium fluoride, polypyrrole, tungsten oxide, and boron oxide.

29. The battery as claimed in claim 1, characterized in that, The negative electrode active material also includes silicon-based materials, and the a% range is 0.0015% to 3.5%.

30. The battery as claimed in claim 1, characterized in that, The battery cell includes a positive electrode tab, and the ratio of the width of the positive electrode tab to the width of the battery cell is in the range of 0.05 to 0.

5. And / or, the battery cell includes a negative electrode tab, and the ratio of the width of the negative electrode tab to the width of the battery cell is in the range of 0.05 to 0.

5.

31. The battery as claimed in claim 1, characterized in that, The battery cell includes a positive electrode and a negative electrode; The ratio of the width of the positive electrode tab to the width of the cell, and / or the ratio of the width of the negative electrode tab to the width of the cell, is 0.9 to 1.

32. An electrical appliance, characterized in that, Includes the battery as described in any one of claims 1 to 31.

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