Battery and preparation method therefor

Abstract

A battery and a preparation method therefor. The battery comprises a positive electrode lithium supplementing material and an electrolyte; the positive electrode lithium supplementing material comprises at least one of lithium nickelate, lithium ferrite and lithium oxide; the electrolyte comprises a silicon-based fluorophosphate compound represented by formula I: formula I, where R1, R2, and R 3 are each independently H, F, C1-C4 alkyl, C1-C4 fluoroalkyl, C2-C4 alkenyl, C2-C4 fluoroalkenyl, C2-C4 alkynyl, C2-C4 fluoroalkynyl, C5-C7 cycloalkyl, R4-substituted phenyl or R5-substituted benzyl, and R4 and R5 are each independently C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, C1-C4 fluoroalkyl, C2-C4 fluoroalkenyl, or C2-C4 fluoroalkynyl.

Description

Battery and its preparation method

[0001] Technical Field

[0002] This disclosure relates to the field of battery technology, and more specifically, to a battery and a method for preparing the same. Background Technology

[0003] Energy storage is a capital-intensive investment sector, and the cycle life of battery systems is a key factor affecting the profitability of energy storage companies. The current cycle life of lithium-ion battery energy storage systems makes it difficult to promote the large-scale commercial application of energy storage power stations. Therefore, how to further improve the cycle life of lithium-ion batteries is an urgent problem to be solved in energy storage batteries. At the same time, improving the cycle life of lithium-ion batteries can reduce end-product production costs and alleviate the pressure on companies to recycle batteries.

[0004] Lithium loss is the direct cause of battery cycle degradation. For example, during the first charge and discharge cycle, a solid electrolyte interphase (SEI) film forms on the negative electrode surface. The formation of the SEI film consumes a large amount of active lithium ions, resulting in a low coulombic efficiency in the first cycle. During subsequent charge and discharge cycles, the cracking and fragmentation of the positive electrode active material particles, the thickening and repair of the SEI film, all consume active lithium ions, leading to a significant decrease in battery cycle performance. Adding lithium replenishers can improve the cycle life of lithium-ion batteries to some extent; however, further research on how to improve battery cycle life is crucial for promoting the application of energy storage batteries.

[0005] Application content

[0006] This application aims to at least partially address one of the technical problems in the related art. To this end, one objective of this application is to provide a battery and a method for its preparation. In this battery electrolyte, by adding silicon-based fluorophosphate compounds as electrolyte additives, the problems of gas expansion and lithium plating caused by positive electrode lithium replenishment materials can be solved, thereby improving the high-temperature performance of the battery.

[0007] In one aspect of this application, a battery is provided, comprising a positive electrode and an electrolyte; the positive electrode comprises a positive electrode lithium replenishment material; the positive electrode lithium replenishment material comprises at least one of lithium nickelate, lithium ferrite, and lithium oxide;

[0008] The electrolyte includes silicon-based fluorophosphate compounds as shown in Formula I:

[0009]

[0010] Formula I;

[0011] In Formula I, R1, R2, and R3 are independently H, F, C1-C4 alkyl, C1-C4 fluoroalkyl, C2-C4 alkenyl, C2-C4 fluoroalkenyl, C2-C4 alkynyl, C2-C4 fluoroalkynyl, C5-C7 cycloalkyl, R4-substituted phenyl, or R5-substituted benzyl; R4 and R5 are independently C1-C4 alkaneyl, C2-C4 alkenylyl, C2-C4 alkynyl, C1-C4 fluoroalkaneyl, C2-C4 fluoroalkenylyl, or C2-C4 fluoroalkynyl.

[0012] The battery system provided in this application includes a lithium replenishment material that can activate and release active Li to achieve the lithium replenishment effect. The unreacted lithium replenishment material continuously releases oxygen free radicals during high-temperature storage, forming oxygen. By adding silicon-based fluorophosphate compounds to the electrolyte, on the one hand, the silicon-based fluorophosphate compounds contain phosphorus central atoms, which can absorb oxygen free radicals and reduce the formation of gas caused by oxygen free radicals; on the other hand, the silicon-based fluorophosphate compounds contain silicon groups, which can react with residual alkali and residual moisture in the lithium replenishment material to form a dense fluorinated phosphate silicon-oxygen polymer, which is used to form an SEI film, improve the stability of the interface film, and improve the high-temperature performance of the battery.

[0013] This application discloses a method for preparing a battery, specifically a method for preparing the battery provided in the first aspect, comprising: preparing a positive electrode sheet and preparing an electrolyte; the step of preparing the positive electrode sheet includes forming a positive electrode active material layer on a positive electrode current collector using a positive electrode slurry, the positive electrode slurry including a positive electrode lithium supplementing material, the positive electrode lithium supplementing material including at least one of lithium nickelate, lithium ferrite and lithium oxide; the electrolyte includes a silicon-based fluorophosphate compound represented by Formula I.

[0014] In some embodiments of this application, the mass percentage of the positive electrode lithium replenishment material in the positive electrode slurry is 0.5% to 4%.

[0015] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Embodiments of the present invention

[0016] The embodiments of the present invention are described in detail below, and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0017] The addition of lithium replenishing agents can improve the cycle life of lithium-ion batteries. Positive electrode lithium replenishment is simple: currently, typical positive electrode lithium replenishment involves adding a small amount of high-capacity lithium replenishing material during the positive electrode slurry preparation process. During charging, Li... +Lithium replenishment is a process that extracts lithium from high-capacity materials to compensate for the irreversible capacity loss during the initial charge-discharge cycle. Lithium replenishment of the cathode is the most promising method for industrial application due to its high safety and the fact that it does not require changes to existing battery manufacturing processes. The most suitable lithium replenishment material is lithium iron phosphate (LFP). i5 Taking FeO4 (LFO) as an example, LFO has gradually become the mainstream lithium replenishment agent in the market, with advantages such as high irreversible capacity (≥670 mAh), good cycle improvement effect (energy density improvement of 6%~8%), and low production cost. However, LFO itself has high chemical reactivity, activating and releasing active Li to achieve the lithium replenishment effect. At the same time, oxygen is generated, which affects the insertion of active Li released from lithium ferrite into the negative electrode, resulting in problems such as black spots and lithium plating. Furthermore, LFO that has not fully reacted during the formation stage will continue to react and release oxygen in subsequent processes (especially high-temperature storage), further causing gas expansion in the battery during the later stages of storage, and causing further lithium plating on the negative electrode, leading to high-temperature performance degradation. Therefore, there is an urgent need to develop a solution to the gas expansion and lithium plating problems caused by LFO, thereby extending the cycle life of the battery.

[0018] In one aspect of the present invention, a battery is provided, comprising: a positive electrode and an electrolyte; the positive electrode comprises a positive electrode lithium replenishing material; the positive electrode lithium replenishing material comprises at least one selected from lithium nickel oxide, lithium ferrite, and lithium oxide;

[0019] The electrolyte includes silicon-based fluorophosphate compounds as shown in Formula I:

[0020]

[0021] Formula I;

[0022] R1, R2, and R3 each independently include any one of H, F, C1-C4 alkyl, C1-C4 fluoroalkyl, C2-C4 alkenyl, C2-C4 fluoroalkenyl, C2-C4 fluoroalkynyl, C2-C4 fluoroalkynyl, C5-C7 cycloalkyl, C5-C7 cycloalkyl, R4-substituted phenyl, and R5-substituted benzyl. R1, R2, and R3 may be the same as or different from each other.

[0023] R4 and R5 are each independently selected from any one of C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, C1-C4 fluoroalkyl, C2-C4 fluoroalkenyl, and C2-C4 fluoroalkynyl.

[0024] The battery system provided in this application includes a lithium replenishment material that can activate and release active Li to achieve the effect of lithium replenishment. The unreacted lithium replenishment material continuously releases oxygen free radicals during high-temperature storage, forming oxygen. By adding silicon-based fluorophosphate compounds to the electrolyte, on the one hand, the silicon-based fluorophosphate compounds contain phosphorus central atoms, which can absorb oxygen free radicals and reduce the formation of gas caused by oxygen free radicals; on the other hand, the silicon-based fluorophosphate compounds contain silicon groups, which can react with the residual moisture in the lithium replenishment material to form a dense fluorinated phosphate silicon-oxygen polymer, which is used to form an SEI film, improve the stability of the interface film, and improve the high-temperature performance of the battery.

[0025] In some embodiments of this application, in Formula I, R1, R2, and R3 are each independently H, F, C1-C4 alkyl, C1-C4 fluoroalkyl, C2-C4 alkenyl, C2-C4 fluoroalkenyl, C2-C4 alkynyl, C2-C4 fluoroalkynyl, C5-C7 cycloalkyl, R4-substituted phenyl, or R5-substituted benzyl.

[0026] R4 and R5 are each independently selected from either -CH3 or F.

[0027] In some embodiments of this application, the silicon-based fluorophosphate compound represented by Formula I includes at least one of the following compounds:

[0028] The compound shown in Formula 1-1, The compound shown in Formula 1-1, The compounds shown in Formula 1-3,

[0029] The compounds shown in Formula 1-4, The compounds shown in Formulas 1-5, The compounds shown in Formulas 1-6 The compounds shown in Formulas 1-7 The compounds shown in Formula 1-8, Compounds shown in Formulas 1-9 The compounds shown in Formula 1-10, The compounds shown in Formula 1-11, The compounds shown in Formula 1-12, The compounds shown in Formula 1-13, The compounds shown in Formula 1-14, The compounds shown in Formula 1-15, The compounds shown in Formula 1-16, The compounds shown in Formula 1-17, The compounds shown in Formula 1-18, The compounds shown in Formula 1-19, The compounds shown in Formula 1-20, The compounds shown in Formula 1-21, The compounds shown in Formula 1-22.

[0030] In the embodiments of this application, at least one of the above-mentioned compounds is used as an electrolyte additive as a silicon-based fluorophosphate compound represented by Formula I, which helps to solve the problems of gas expansion and lithium plating caused by oxygen production in lithium-filled batteries, and further improves the high-temperature performance of the battery.

[0031] Furthermore, the silicon-based fluorophosphate compounds represented by Formula I include at least one of the following compounds:

[0032] The compound shown in Formula I-1 .

[0033] In some embodiments of this application, the mass percentage of the silicon-based fluorophosphate compound represented by Formula I in the electrolyte is 0.1% to 3%.

[0034] In this embodiment, the mass percentage of the silicon-based fluorophosphate compound shown in Formula I in the electrolyte meets the above conditions, which is beneficial for improving the deoxygenation effect, solving the gas expansion and lithium plating problems caused by oxygen production in lithium-filled batteries, and further improving the high-temperature performance of the battery; at the same time, it is beneficial for forming an interface film of appropriate thickness, reducing internal resistance, and improving battery performance. In specific examples, the mass percentage of the silicon-based fluorophosphate compound shown in Formula I in the electrolyte is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, etc.

[0035] In some embodiments of this application, the mass percentage of the silicon-based fluorophosphate compound represented by Formula I in the electrolyte is 0.5% to 2%.

[0036] In the embodiments of this application, the silicon-based fluorophosphate compound represented by Formula I has a mass percentage content of 0.5% to 2% in the electrolyte, which is beneficial to improve the deoxygenation effect, solve the gas expansion and lithium plating problems caused by oxygen production in lithium-replenishing batteries, and further improve the high-temperature performance of the battery; at the same time, it is beneficial to form an interface film of appropriate thickness, reduce internal resistance, and improve battery performance.

[0037] In some embodiments of this application, the electrolyte further includes a solvent and a lithium salt; the electrolyte satisfies at least one of the following:

[0038] (i) The solvent includes at least one of carbonate solvents, carboxylic acid ester solvents and ether solvents;

[0039] (ii) Lithium salts include at least one of LiPF6, LiFSI, LiTFSI and LiBF4.

[0040] (iii) The mass percentage of lithium salt in the electrolyte is 8% to 18%.

[0041] In the embodiments of this application, the solvent may be at least one of carbonate solvents, carboxylic acid ester solvents, and ether solvents.

[0042] Furthermore, carbonate solvents include at least one of ethylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, and methyl propyl carbonate.

[0043] Furthermore, the carboxylic acid ester solvents include at least one of methyl formate, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, propyl propionate, and ethyl butyrate.

[0044] Furthermore, the ether solvent includes at least one of tetrahydrofuran, 1,3-dioxapentane, diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0045] In the embodiments of this application, the lithium salt includes at least one of LiPF6 (lithium hexafluorophosphate), LiFSI (lithium bisfluorosulfonylimide), LiTFSI (lithium bistrifluoromethanesulfonylimide), and LiBF4 (lithium tetrafluoroborate).

[0046] In the embodiments of this application, the mass percentage of lithium salt in the electrolyte is 8% to 18%, with specific examples being 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, etc.

[0047] In some embodiments of this application, the electrolyte further includes a film-forming agent, which satisfies at least one of the following (I) and (II):

[0048] (I) The film-forming agent includes at least one of cyclic carbonates, cyclic sulfates, or cyclic sulfonyl lactones;

[0049] (II) The mass percentage of the film-forming agent in the electrolyte is 0.1%~3%.

[0050] The addition of a film-forming agent to the electrolyte in the battery embodiments of this application can improve the electrochemical performance of the battery, especially during charge-discharge cycles. During the first charge of the battery, the film-forming agent undergoes a chemical reaction on the electrode surface to form a stable solid electrolyte interphase (SEI) film.

[0051] Furthermore, adding film-forming agents (such as VC) to the battery electrolyte to form an SEI film composed of polyorganic materials has certain shortcomings, such as poor hardness and weak durability of the formed SEI film. In the embodiments of this application, a silicon-based fluorophosphate compound is added to the electrolyte. This silicon-based fluorophosphate compound reacts with residual alkali and moisture in the lithium replenishing agent to form a dense fluorinated phosphate-containing silicon-oxygen polymer. This fluorinated phosphate-containing silicon-oxygen polymer can provide a large amount of lithium difluorophosphate and inorganic components with silicon-oxygen structures, making the SEI film both robust and tough, and thinner. It also facilitates the desolvation and embedding of active Li into the graphite anode, reducing polarization and thus suppressing lithium plating problems, reducing interfacial impedance, and minimizing battery expansion, thereby improving the battery's high-temperature cycling and storage performance.

[0052] Furthermore, cyclic carbonates include at least one of vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0053] Furthermore, cyclic sulfates include vinyl sulfate (DTD).

[0054] Furthermore, cyclic sulfonyl lactones include 1,3-propanesulfonyl lactone (1,3-PS).

[0055] In this embodiment, the mass percentage of the film-forming agent in the electrolyte meets the above conditions, which is beneficial to improving the stability of the interfacial film and improving battery performance. Specifically, the mass percentage of the film-forming agent in the electrolyte is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, etc.

[0056] Furthermore, the mass percentage of the film-forming agent in the electrolyte is 0.5% to 2.5%.

[0057] In some embodiments of this application, the battery includes a positive electrode;

[0058] The positive electrode sheet includes a positive current collector and a positive active material layer attached to at least one side surface of the positive current collector. The positive active material layer includes a positive active material and a positive lithium supplement material.

[0059] Alternatively, it may also include a lithium replenishment sheet combined with the positive electrode sheet; the lithium replenishment sheet includes a positive electrode lithium replenishment material, and the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer attached to at least one side of the surface of the positive electrode current collector, the positive electrode active material layer including at least a positive electrode active material.

[0060] Furthermore, the cathode material is lithium iron phosphate.

[0061] In some embodiments of this application, the positive electrode current collector may include a metal foil or a composite positive electrode current collector. For example, the metal foil may be aluminum foil. The composite positive electrode current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. For example, the composite negative electrode current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0062] In some embodiments of this application, the positive electrode active material layer may optionally include a conductive agent and a binder. The conductive agent can be selected based on actual needs. The binder can be selected based on actual needs.

[0063] In some embodiments of this application, the positive electrode active material includes at least one of nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, nickel-cobalt-manganese-aluminum quaternary materials, nickel-manganese-aluminum ternary materials, lithium cobalt oxide, lithium manganese oxide, lithium manganese iron phosphate, and lithium iron phosphate.

[0064] In some embodiments of this application, the positive electrode active material includes lithium iron phosphate; the electrolyte includes film-forming additives, including vinylene carbonate.

[0065] In some embodiments of this application, a negative electrode sheet is also included, which includes a negative electrode active material, and the negative electrode active material includes at least one of carbon material and silicon material.

[0066] Furthermore, carbon materials include at least one of natural graphite, artificial graphite, hard carbon, and soft carbon.

[0067] Furthermore, silicon materials include at least one of pure silicon materials, silicon-carbon materials, and silicon-oxygen materials.

[0068] In some embodiments of this application, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer attached to at least one side surface of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material.

[0069] In some embodiments of this application, the negative electrode active material layer may optionally include a conductive agent and a binder. The conductive agent can be selected based on actual needs. The binder can be selected based on actual needs.

[0070] A method for preparing a battery is proposed in two aspects of the application embodiments, specifically the method for preparing the battery provided in the first aspect of the application embodiments, including: preparing a positive electrode sheet and preparing an electrolyte;

[0071] The steps for preparing the positive electrode sheet include forming a positive active material layer on the positive current collector using a positive electrode slurry. The positive electrode slurry includes a positive lithium supplement material, which includes at least one of lithium nickelate, lithium iron phosphate, and lithium oxide. The electrolyte includes a silicon-based fluorophosphate compound represented by Formula I.

[0072] The battery system prepared in this application includes a lithium replenishing material, which can activate and release active Li to achieve the effect of lithium replenishment. The unreacted lithium replenishing material continuously releases oxygen free radicals during high-temperature storage, forming oxygen. By adding silicon-based fluorophosphate compounds to the electrolyte, on the one hand, silicon-based fluorophosphate compounds contain phosphorus central atoms, which can absorb oxygen free radicals and reduce the formation of gas caused by oxygen free radicals; on the other hand, silicon-based fluorophosphate compounds contain silicon groups, which can react with the residual moisture in the lithium replenishing material to form a dense fluorinated phosphate silicon-oxygen polymer, which is used to form an SEI film, improve the stability of the interface film, and improve the high-temperature performance of the battery.

[0073] In some embodiments of this application, the mass percentage of the positive electrode lithium replenishment material in the positive electrode slurry is 0.5% to 4%.

[0074] The amount of positive electrode lithium replenishing material added in the embodiments of this application meets the above conditions, which is beneficial for its use in combination with silicon-based fluorophosphate compounds to improve the performance of the positive electrode lithium replenishing material on the battery.

[0075] As an example, the mass percentage of the positive electrode lithium replenishment material in the positive electrode slurry is 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, etc.

[0076] In some embodiments of this application, the positive electrode slurry also includes a positive electrode active material, a conductive agent, a binder, and a solvent.

[0077] Specifically, a positive electrode active material, a positive electrode lithium supplementing material, a conductive agent, a binder, and a solvent can be formulated into a positive electrode slurry. The positive electrode slurry is then coated onto a positive electrode current collector, and subsequently molded to obtain a positive electrode sheet. The conductive agent, binder, solvent, and positive electrode current collector material can be selected from conventional materials in this field.

[0078] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the invention in any way. The reagents used in the embodiments are all from Aladdin Biochemical Technology Co., Ltd.

[0079] Preparation of Compounds

[0080] 1. The compound shown in Formula I-1 The CAS number is 4419-25-9.

[0081]

[0082] 2. The compound shown in Formula I-2 The CAS number is 2708941-25-5.

[0083]

[0084] 3. The compound shown in Formula I-3 The CAS number is 13683-39-1.

[0085]

[0086] 4. The compound shown in Formula I-4 The CAS number is 4414-27-1.

[0087]

[0088] 5. The compound shown in Formula I-5 The CAS number is 4414-26-0.

[0089]

[0090] 6. The compound shown in Formula I-6 The CAS number is 4480-02-8.

[0091]

[0092] 7. The compound shown in Formula I-7 The CAS number is 2577172-95-1.

[0093]

[0094] 8. The compound shown in Formula I-8 The CAS number is 13683-40-4.

[0095]

[0096] 9. Compounds shown in Formula I-9 The CAS number is 2577172-93-9.

[0097]

[0098] 10. Compounds shown in Formula I-10 The CAS number is 2708941-27-7.

[0099]

[0100] 11. The compound shown in Formula I-11 The CAS number is 2287283-36-5.

[0101]

[0102] 12. The compound shown in Formula I-12 The CAS number is 6231-57-8.

[0103]

[0104] 13. The compound shown in Formula I-13 The CAS number is 1386-54-9.

[0105] 14. The compound shown in Formula I-14 The CAS number is 2708941-26-6.

[0106]

[0107] 15. The compound shown in Formula I-15 The CAS number is 6231-58-9.

[0108]

[0109] 16. Compounds shown in Formula I-16 The CAS number is 6231-59-0.

[0110]

[0111] 17. The compound shown in Formula I-17 The CAS number is 2577172-94-0.

[0112] 18. The compounds shown in Formula I-18 to Formula I-22 were prepared according to the preparation method of Example 14 in Patent CN114728992A, specifically, the dichlorophenylsilane in the reference patent was replaced with the following raw materials.

[0113] The compound shown in Formula I-18 The raw material used is trivinylchlorosilane (CAS No.: 1871-21-2).

[0114] The compound shown in Formula I-19 The raw material used is dimethylethynyl butylchlorosilane (2069196-19-4).

[0115] The compound shown in Formula I-20 The raw material used is dimethyl (trifluoropropylene) chlorosilane (89705-02-2).

[0116] The compound shown in Formula I-21 The raw material used is tris(pentafluoroethyl)chlorosilane (1620665-21-5).

[0117] The compound shown in Formula I-22 The raw material used is dimethyl(p-methylbenzyl)chlorosilane (1833-28-9).

[0118] [Battery Manufacturing]

[0119] Example 1

[0120] Positive electrode sheet: The positive electrode active material lithium iron phosphate, lithium supplementer (lithium-rich lithium iron phosphate LFO), conductive agent conductive carbon black super-p, and binder (polyvinylidene fluoride) PVDF are dispersed in the solvent NMP (N-methylpyrrolidone) at a mass ratio of 93:3:2:2 (LFO addition is 3%) to obtain a positive electrode active material layer slurry; the positive electrode active material layer slurry is uniformly coated on the surface of the positive electrode current collector aluminum foil, and after drying, rolling, baking, slitting and spot welding of the tabs, the positive electrode sheet is obtained.

[0121] Negative electrode sheet: The negative electrode active material graphite, conductive agent conductive carbon black super-p, binder SBR, and dispersant sodium carboxymethyl cellulose (CMC) are dispersed in deionized water at a mass ratio of 95:1.5:2:1.5 and stirred evenly to obtain a negative electrode active material layer slurry; the negative electrode active material layer slurry is evenly coated on the surface of the negative electrode current collector copper foil, and after drying, rolling, baking, slitting and spot welding of electrode tabs, the negative electrode sheet is obtained.

[0122] Electrolyte: The solvent is a combination of ethylene carbonate (EC) and ethyl methyl carbonate (EMC), EC:EMC=3:7 (mass ratio); the additive is VC, added at 2% (mass percentage); the silicon-based fluorophosphate compound is added at 0.5% (mass percentage); the lithium salt is lithium hexafluorophosphate, with a concentration of 1 mol / L.

[0123] Membrane: Polypropylene / Polyethylene / Polypropylene three-layer composite membrane (PP / PE / PP).

[0124] Battery: The prepared positive electrode, negative electrode and separator are stacked in sequence, the separator is placed between the positive electrode and negative electrode, and the cells are wound up to obtain the battery cell. The battery cell is placed in the outer packaging, and the electrolyte is injected into the battery cell in the glove box. Then it is left to stand for 24 hours, pre-charged for the first formation, then sealed, and after the second formation, the preparation of the lithium-ion battery is completed.

[0125] Examples 2-45

[0126] The battery preparation methods provided in Examples 2-45 are as shown in Example 1, with differences shown in Tables 1-1 and 1-2.

[0127] Comparative Examples 1-4

[0128] The battery preparation methods provided in Examples 2-45 are as shown in Example 1, with differences shown in Tables 1-1 and 1-2.

[0129] The preparation parameters of the batteries provided in Examples 2-45 and Comparative Examples 1-4 are shown in Tables 1-1 and 1-2.

[0130] Table 1-1

[0131]

[0132] Table 1-2

[0133]

[0134] In Tables 1-1 and 1-2, the proportions of the film-forming additives in Examples 29-31, 40, and 41 are expressed as mass ratios. "NCM811" indicates LiNi 0.8 Co 0.1 Mn 0.1 O2. “LMFP” indicates lithium manganese iron phosphate.

[0135] I. Testing Method:

[0136] 1. Lithium-ion battery storage test at 60℃:

[0137] First, after the cells were sealed twice (gas removed), the lithium-ion batteries were left to stand at 25°C for 30 minutes. They were then charged at a constant current of 1C to 3.65V, and further charged at a constant voltage of 3.65V until the current reached 0.05C. Next, the lithium-ion batteries were discharged at a constant current of 1C to 2.0V; this discharge capacity is recorded as C0. They were then charged again at a constant current of 1C to 3.65V, and further charged at a constant voltage of 3.65V until the current reached 0.05C. Finally, the battery volume was measured using the water displacement method; this is the volume V0 before storage. Afterward, the lithium-ion batteries were stored at 60°C for 30 days. After storage, the rechargeable lithium-ion batteries were placed at 25°C, and the volume was measured using the water displacement method; this is the volume V after storage. 30 Then, the lithium-ion battery is discharged at a constant current of 1 C to 2.0 V. The discharge capacity at this point is denoted as C'. 30 The lithium-ion secondary battery is then charged to 3.65 V using a constant current of 1 C, and further charged to 0.05 C using a constant voltage of 3.65 V. Finally, the lithium-ion secondary battery is discharged to 2.0 V using a constant current of 1 C. The discharge capacity at this point is denoted as C. 30 .

[0138] Lithium-ion storage capacity retention rate (%) after 30 days of storage = C'30 / C0;

[0139] Lithium-ion storage capacity recovery rate (%) after 30 days of storage = C 30 / C0;

[0140] Volume expansion rate (%) of lithium-ion battery after 30 days of storage = (V 30 V0) / V0.

[0141] 2. High-Temperature Storage DCR Performance Test:

[0142] After the battery was left to stand at 25 °C for 30 minutes, its discharge DC internal resistance (DCIR) was tested and recorded as R0. Then, the battery was stored at 60 °C for 30 days. After storage, the battery was placed at 25 °C and its discharge DC internal resistance (DCIR) was tested again and recorded as R. 30

[0143] 3. 45℃ Cyclic Performance Test:

[0144] The test method is as follows: The lithium-ion battery is charged to 3.65 V at a constant current and voltage of 1 C in a constant temperature chamber at 45 ℃±1 ℃, with a cutoff current of 0.05 C, and then discharged to 2.0 V at 1 C. Multiple charge-discharge cycles are performed under these conditions. The capacity retention rate of the battery after 500 cycles is calculated.

[0145] 4. Percentage of lithium plating region at the negative electrode interface of the battery:

[0146] Before and after cycling, the battery was disassembled, the area of ​​the lithium plating region at the interface was recorded, and its proportion in the entire negative electrode interface was calculated.

[0147] II. Test Results:

[0148] The performance test results of the batteries provided in Examples 1-45 and Comparative Examples 1-4 are shown in Tables 2-1 and 2-2.

[0149] Table 2-1

[0150]

[0151] Table 2-2

[0152]

[0153] Performance testing results show that silicon-based fluorophosphate compounds, when used as oxygen scavengers in positive electrode lithium replenishment materials, are beneficial for improving the high-temperature performance of batteries and solving the problems of gas expansion and lithium plating caused by oxygen production in lithium replenishment batteries. By optimizing the dosage of silicon-based fluorophosphate compounds, active oxygen can be fully absorbed, and phosphate-silicon oxide polymers can be generated to form a high-quality, thin SEI film, which can further improve cycle performance.

[0154] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0155] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A battery, wherein, include: Positive electrode and electrolyte; The positive electrode sheet includes a positive electrode lithium replenishment material, which includes at least one of lithium nickel oxide, lithium iron ferrite and lithium oxide. The electrolyte comprises a silicon-based fluorophosphate compound represented by Formula I: Formula I; In Formula I, R1, R2, and R3 are independently H, F, C1-C4 alkyl, C1-C4 fluoroalkyl, C2-C4 alkenyl, C2-C4 fluoroalkenyl, C2-C4 alkynyl, C2-C4 fluoroalkynyl, C5-C7 cycloalkyl, R4-substituted phenyl, or R5-substituted benzyl; R4 and R5 are independently C1-C4 alkaneyl, C2-C4 alkenylyl, C2-C4 alkynyl, C1-C4 fluoroalkaneyl, C2-C4 fluoroalkenylyl, or C2-C4 fluoroalkynyl.

2. The battery according to claim 1, wherein, In Formula I, R1, R2, and R3 are each independently H, F, C1-C4 alkyl, C1-C4 fluoroalkyl, C2-C4 alkenyl, C2-C4 fluoroalkenyl, C2-C4 alkynyl, C2-C4 fluoroalkynyl, C5-C7 cycloalkyl, R4-substituted phenyl, or R5-substituted benzyl. R4 and R5 are each independently selected from either -CH3 or F.

3. The battery according to claim 1 or 2, wherein, The silicon-based fluorophosphate compounds represented by Formula I include at least one of the following compounds: The compound shown in Formula 1-1, The compound shown in Formula 1-1, The compounds shown in Formula 1-3, The compounds shown in Formula 1-4, The compounds shown in Formulas 1-5, The compounds shown in Formulas 1-6 The compounds shown in Formulas 1-7 The compounds shown in Formula 1-8, Compounds shown in Formulas 1-9 The compounds shown in Formula 1-10, The compounds shown in Formula 1-11, The compounds shown in Formula 1-12, The compounds shown in Formula 1-13, The compounds shown in Formula 1-14, The compounds shown in Formula 1-15, The compounds shown in Formula 1-16, The compounds shown in Formula 1-17, The compounds shown in Formula 1-18, The compounds shown in Formula 1-19, The compounds shown in Formula 1-20, The compounds shown in Formula 1-21, The compounds shown in Formula 1-22.

4. The battery according to any one of claims 1 to 3, wherein, The mass percentage of the silicon-based fluorophosphate compound represented by Formula I in the electrolyte is 0.1% to 3%.

5. The battery according to any one of claims 1 to 3, wherein, The mass percentage of the silicon-based fluorophosphate compound represented by Formula I in the electrolyte is 0.5% to 2%.

6. The battery according to any one of claims 1 to 5, wherein, The electrolyte further includes a solvent and a lithium salt; the electrolyte satisfies at least one of the following: (i) The solvent includes at least one of carbonate solvents, carboxylic acid ester solvents, and ether solvents; (ii) The lithium salt includes at least one of LiPF6, LiFSI, LiTFSI and LiBF4; (iii) The lithium salt in the electrolyte has a mass percentage content of 8% to 18%.

7. The battery according to any one of claims 1 to 6, wherein, The electrolyte further includes a film-forming agent, which satisfies at least one of the following (I) and (II): (I) The film-forming agent includes at least one of cyclic carbonates, cyclic sulfates, or cyclic sulfonyl lactones; (II) The film-forming agent has a mass percentage content of 0.1% to 3% in the electrolyte.

8. The battery according to any one of claims 1 to 7, wherein, Including the positive electrode plate; The positive electrode sheet includes a positive current collector and a positive active material layer attached to at least one side surface of the positive current collector, wherein the positive active material layer includes a positive active material and a positive lithium supplement material; Alternatively, it may also include a lithium replenishment sheet combined with the positive electrode sheet; the lithium replenishment sheet includes a positive electrode lithium replenishment material, and the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer attached to at least one side surface of the positive electrode current collector, the positive electrode active material layer including at least a positive electrode active material.

9. The battery according to claim 8, wherein, The positive electrode active material includes at least one of nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, nickel-cobalt-manganese-aluminum quaternary materials, nickel-manganese-aluminum ternary materials, lithium cobalt oxide, lithium manganese oxide, lithium manganese iron phosphate, and lithium iron phosphate.

10. The battery according to claim 8, wherein, The positive electrode active material includes lithium iron phosphate; the electrolyte includes a film-forming additive, which includes vinylene carbonate.

11. The battery according to any one of claims 1 to 10, wherein, It also includes a negative electrode sheet, which includes a negative electrode active material, and the negative electrode active material includes at least one of carbon material and silicon material.

12. A method for preparing the battery according to any one of claims 1-11, wherein, include: Preparation of positive electrode sheet and preparation of electrolyte; The step of preparing the positive electrode sheet includes forming a positive active material layer on the positive current collector using a positive electrode slurry. The positive electrode slurry includes a positive lithium supplementing material, which includes at least one of lithium nickelate, lithium ferrite, and lithium oxide. The electrolyte includes a silicon-based fluorophosphate compound represented by Formula I.

13. The method according to claim 12, wherein, The positive electrode lithium replenishment material has a mass percentage content of 0.5% to 4% in the positive electrode slurry.

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