Battery and preparation method thereof

Abstract

The invention discloses a battery and a preparation method thereof. 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 as shown in a formula I: # imgabs0 #, wherein R1, R2 and R3 are independently H, F, alkyl of C1-C4, fluoroalkyl of C1-C4, alkenyl of C2-C4, fluoroalkenyl of C2-C4, alkynyl of C2-C4, fluoroalkynyl of C2-C4, cycloalkane of C5-C7, phenyl substituted by R4 or benzyl substituted by R5; r1, R2, R3, R4 and R5 are independently alkyl groups of C1-C4, alkylene groups of C2-C4, alkyne groups of C2-C4, fluoro alkyl groups of C1-C4, fluoro alkylene groups of C2-C4 or fluoro alkyne groups of C2-C4. The compound shown in the formula I is added into the electrolyte, so that the problems of gas expansion and lithium precipitation caused by a positive electrode lithium supplementing material can be solved, and the battery performance is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a battery and a preparation method thereof. Background Art

[0002] The energy storage sector is a heavy asset investment. The cycle life of the battery system is a key factor affecting the profitability of energy storage companies. The current cycle life of lithium-ion energy storage systems is difficult to promote large-scale commercial applications of energy storage power stations. Therefore, how to further improve the cycle life of ion batteries is an urgent problem to be solved for energy storage batteries. At the same time, improving the cycle life of lithium-ion batteries can reduce terminal production costs and alleviate the pressure on corporate battery recycling.

[0003] Lithium loss is the direct cause of battery cycle attenuation. For example, during the first charge and discharge process of the battery, the electrolyte will form a solid electrolyte interface film (SEI film) on the surface of the negative electrode. The formation of the SEI film will consume a large amount of active lithium ions, which will lead to a low coulombic efficiency of the first cycle of the battery. During the battery's charge and discharge cycle, the cracking and crushing of the positive electrode active material particles, the thickening and repair of the SEI film, etc. will consume active lithium ions, which will cause a significant decrease in the battery's cycle performance. The addition of lithium supplements can have a certain effect on improving the cycle life of lithium-ion batteries. However, on this basis, studying how to further improve the cycle life of batteries is of great significance for promoting the application of energy storage batteries. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the related art to at least a certain extent. To this end, one object of the present invention is to provide a battery and a method for preparing the same. In the battery electrolyte, by adding a silicon-based fluorophosphate compound as an electrolyte additive, the gas expansion and lithium precipitation problems caused by the positive electrode lithium supplement material can be solved, thereby improving the high temperature performance of the battery.

[0005] In one aspect of the present invention, the present invention provides a battery, comprising a positive electrode sheet and an electrolyte; the positive electrode sheet comprises a positive electrode lithium supplement material; the positive electrode lithium supplement material comprises at least one of lithium nickelate, lithium ferrite and lithium oxide;

[0006] The electrolyte includes a silicon-based fluorophosphate compound shown in Formula I:

[0007]

[0008]

[0009] 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 cycloalkane, R4 substituted phenyl or R5 substituted benzyl; R4 and R5 are independently C1-C4 alkyl, C2-C4 alkene, C2-C4 alkynyl, C1-C4 fluoroalkyl, C2-C4 fluoroalkenyl or C2-C4 fluoroalkynyl.

[0010] The battery system provided in the present application includes a lithium replenishing material, which can be activated to release active Li to achieve the effect of lithium replenishment. The unreacted lithium replenishing material continues to release oxygen free radicals to form oxygen during high-temperature storage. 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 gases caused by oxygen free radicals; on the other hand, the silicon-based fluorophosphate compounds contain silicon groups that can react with residual alkali and residual moisture in the lithium replenishing material to form a dense silicon-oxygen polymer containing fluorinated phosphates, which is used to form an SEI film, improve the stability of the interface film, and improve the high-temperature performance of the battery.

[0011] In some embodiments of the present 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 cycloalkane, R4 substituted phenyl, or R5 substituted benzyl;

[0012] R4 and R5 are each independently selected from any one of -CH3 and F.

[0013] In some embodiments of the present application, the silicon-based fluorophosphate compound represented by Formula I includes at least one of the following compounds:

[0014] 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 alkynyl, C2-C4 fluoroalkynyl, C5-C7 cycloalkane, C5-C7 cycloalkane, R4 substituted phenyl and R5 substituted benzyl, and R1, R2 and R3 are the same or different from each other.

[0015] R4 and R5 are each independently selected from any one of a C1-C4 alkyl group, a C2-C4 alkenyl group, a C2-C4 alkynyl group, a C1-C4 fluoroalkyl group, a C2-C4 fluoroalkenyl group and a C2-C4 fluoroalkynyl group.

[0016] In some embodiments of the present application, the silicon-based fluorophosphate compound represented by Formula I includes at least one of the following compounds:

[0017] The compounds shown, The compounds shown, The compounds shown,

[0018] The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown.

[0019] In some embodiments of the present application, the mass percentage of the silicon-based fluorophosphate compound represented by Formula I in the electrolyte is 0.1% to 3%.

[0020] In some embodiments of the present application, the mass percentage of the silicon-based fluorophosphate compound represented by Formula I in the electrolyte is 0.5% to 2%.

[0021] In some embodiments of the present application, the electrolyte further includes a solvent and a lithium salt; the electrolyte satisfies at least one of the following:

[0022] (i) the solvent comprises at least one of a carbonate solvent, a carboxylate solvent and an ether solvent;

[0023] (ii) the lithium salt comprises at least one of LiPF6, LiFSI, LiTFSI and LiBF4;

[0024] (iii) The mass percentage of lithium salt in the electrolyte is 8% to 18%.

[0025] In some embodiments of the present application, the electrolyte further includes a film-forming agent, and the film-forming agent satisfies: the film-forming agent includes at least one of cyclic carbonate, cyclic sulfate or cyclic sultone; and / or the mass percentage of the film-forming agent in the electrolyte is 0.1% to 3%.

[0026] In some embodiments of the present application, the battery includes a positive electrode sheet;

[0027] 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, and the positive electrode active material layer includes a positive electrode active material and a positive electrode lithium supplement material;

[0028] Alternatively, it also includes a lithium replenishing sheet compounded with the positive electrode sheet; the lithium replenishing sheet includes a positive electrode lithium replenishing material, the positive electrode sheet includes a positive electrode collector and a positive electrode active material layer attached to at least one side of the positive electrode collector, and the positive electrode active material layer includes at least a positive electrode active material.

[0029] In some embodiments of the present application, the positive electrode active material includes at least one of nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material, nickel-cobalt-manganese-aluminum quaternary material, nickel-manganese-aluminum ternary material, lithium cobaltate, lithium manganeseate, lithium iron manganese phosphate and lithium iron phosphate.

[0030] In some embodiments of the present application, the positive electrode active material includes lithium iron phosphate; the electrolyte includes a film-forming additive, and the film-forming additive includes vinylene carbonate.

[0031] In some embodiments of the present application, the battery further includes a negative electrode sheet, the negative electrode sheet includes a negative electrode active material, and the negative electrode active material includes at least one of a carbon material and a silicon material.

[0032] In the second aspect of the present invention, a method for preparing a battery is proposed, 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 comprises using a positive electrode slurry to form a positive electrode active material layer on a positive electrode current collector, the positive electrode slurry comprises a positive electrode lithium replenishing material, and the positive electrode lithium replenishing material comprises at least one of lithium nickelate, lithium ferrite and lithium oxide; the electrolyte comprises a silicon-based fluorophosphate compound shown in formula I.

[0033] In some embodiments of the present application, the mass percentage of the positive electrode lithium supplement material in the positive electrode slurry is 0.5% to 4%.

[0034] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. DETAILED DESCRIPTION

[0035] The embodiments of the present invention are described in detail below, which are intended to explain the present invention but should not be construed as limiting the present invention.

[0036] The cycle life of lithium-ion batteries can be improved by adding lithium supplements. The operation of positive electrode lithium supplementation is simple: the typical positive electrode lithium supplementation is to add a small amount of high-capacity lithium supplement material during the positive electrode slurry process. + It is extracted from high-capacity materials to supplement the irreversible capacity loss of the first charge and discharge. Positive electrode lithium supplementation has the most industrial application prospects due to its high safety and no need to change the existing battery production process. Lithium supplementation materials are mainly lithium-rich lithium iron oxide L i5 Taking FeO4 (LFO) as an example, LFO has gradually become the mainstream lithium supplement in the market, which has the advantages of high irreversible capacity (≥670mAh), good cycle improvement effect (energy density increased by 6% to 8%), and low production cost. However, LFO itself has high chemical reaction activity, which activates and releases active Li to achieve the effect of lithium supplementation. At the same time, it is accompanied by the generation of oxygen, which will affect the active Li released by lithium ferrite to embed in the negative electrode, resulting in black spots, lithium precipitation and other problems; and LFO that has not reacted completely in the formation stage will continue to react and release oxygen in the subsequent process (especially high-temperature storage), further causing the battery to produce gas and expand in the later stage of storage, and at the same time causing further lithium precipitation at the negative electrode of the battery, resulting in high-temperature performance degradation; therefore, it is urgent to develop a method that can solve the gas expansion and lithium precipitation problems caused by LFO, thereby extending the cycle life of the battery.

[0037] In one aspect of the present invention, the present invention provides a battery, comprising: a positive electrode sheet and an electrolyte; the positive electrode sheet comprises a positive electrode lithium supplement material; the positive electrode lithium supplement material comprises at least one of lithium nickelate, lithium ferrite and lithium oxide;

[0038] The electrolyte includes a silicon-based fluorophosphate compound shown in Formula I:

[0039]

[0040] 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 alkynyl, C2-C4 fluoroalkynyl, C5-C7 cycloalkane, C5-C7 cycloalkane, R4 substituted phenyl and R5 substituted benzyl, and R1, R2 and R3 are the same or different from each other.

[0041] R4 and R5 are each independently selected from any one of a C1-C4 alkyl group, a C2-C4 alkenyl group, a C2-C4 alkynyl group, a C1-C4 fluoroalkyl group, a C2-C4 fluoroalkenyl group and a C2-C4 fluoroalkynyl group.

[0042] The battery system provided in the embodiment of the present application includes a lithium replenishing material, which can be activated to release active Li to achieve the effect of lithium replenishment. The unreacted lithium replenishing material continues to release oxygen free radicals to form oxygen during high-temperature storage. 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 gases caused by oxygen free radicals; on the other hand, the silicon-based fluorophosphate compounds contain silicon groups that can react with residual moisture in the lithium replenishing material to form a dense silicon-oxygen polymer containing fluorinated phosphates, which is used to form an SEI film, improve the stability of the interface film, and improve the high-temperature performance of the battery.

[0043] In some embodiments of the present 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 cycloalkane, R4 substituted phenyl, or R5 substituted benzyl;

[0044] R4 and R5 are each independently selected from any one of -CH3 and F.

[0045] In some embodiments of the present application, the silicon-based fluorophosphate compound represented by Formula I includes at least one of the following compounds:

[0046] The compounds shown, The compounds shown, The compounds shown,

[0047] The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compound represented by formula 1-9, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown.

[0048] In the embodiments of the present application, the at least one compound mentioned above is used as a silicon-based fluorophosphate compound shown in Formula I as an electrolyte additive, which is beneficial to solve the gas expansion and lithium precipitation problems caused by oxygen production in lithium-supplemented material batteries, and further improve the high temperature performance of the battery.

[0049] Furthermore, the silicon-based fluorophosphate compound represented by formula I includes at least one of the following compounds:

[0050] Compound represented by formula I-1

[0051] In some embodiments of the present application, the mass percentage of the silicon-based fluorophosphate compound represented by Formula I in the electrolyte is 0.1% to 3%.

[0052] In the embodiment of the present application, the mass percentage of the silicon-based fluorophosphate compound shown in Formula I in the electrolyte meets the above conditions, which is beneficial to improve the deoxygenation effect, solve the gas expansion and lithium precipitation problems caused by the oxygen production of the lithium-supplemented material battery, 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. In a specific example, 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.

[0053] In some embodiments of the present application, the mass percentage of the silicon-based fluorophosphate compound represented by Formula I in the electrolyte is 0.5% to 2%.

[0054] In the embodiment of the present application, the mass percentage of the silicon-based fluorophosphate compound shown in Formula I in the electrolyte is 0.5% to 2%, which is beneficial to improving the deoxygenation effect, solving the gas expansion and lithium precipitation problems caused by oxygen production in the lithium-supplemented material battery, and further improving 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.

[0055] In some embodiments of the present application, the electrolyte further includes a solvent and a lithium salt; the electrolyte satisfies at least one of the following:

[0056] (i) the solvent comprises at least one of a carbonate solvent, a carboxylate solvent and an ether solvent;

[0057] (ii) The lithium salt includes at least one of LiPF6, LiFSI, LiTFSI and LiBF4.

[0058] (iii) The mass percentage of lithium salt in the electrolyte is 8% to 18%.

[0059] In the embodiment of the present application, the solvent may be at least one of a carbonate solvent, a carboxylate solvent and an ether solvent.

[0060] Further, the carbonate solvent includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate and methyl propyl carbonate.

[0061] Further, the carboxylate solvent includes at least one of methyl formate, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, propyl propionate and ethyl butyrate.

[0062] Further, the ether solvent includes at least one of tetrahydrofuran, 1,3-dioxolane, ethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.

[0063] In an embodiment of the present application, the lithium salt includes at least one of LiPF6 (lithium hexafluorophosphate), LiFSI (lithium bis(trifluoromethanesulfonyl)imide), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) and LiBF4 (lithium tetrafluoroborate).

[0064] In the embodiment of the present application, the mass percentage of lithium salt in the electrolyte is 8% to 18%, and specific examples are 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, etc.

[0065] In some embodiments of the present application, the electrolyte further includes a film-forming agent, and the film-forming agent satisfies: the film-forming agent includes at least one of cyclic carbonate, cyclic sulfate or cyclic sultone; and / or the mass percentage of the film-forming agent in the electrolyte is 0.1% to 3%.

[0066] The addition of a film-forming agent to the electrolyte in the battery of the present application embodiment can be used to improve the electrochemical performance of the battery, especially during the charge and discharge cycle of the battery. The film-forming agent will undergo a chemical reaction on the electrode surface during the first charge of the battery to form a stable solid electrolyte interface (SEI) film.

[0067] In addition, the addition of a film-forming agent (such as VC) to the electrolyte of the battery to form a SEI film formed by polyorganic matter has certain shortcomings, such as the poor hardness and weak firmness of the SEI film formed. The electrolyte of the battery in the embodiment of the present application adds a silicon-based fluorophosphate compound additive, and the silicon-based fluorophosphate compound reacts with the residual alkali and residual water in the lithium supplement to form a dense silicon-oxygen polymer containing fluorinated phosphates. The silicon-oxygen polymer containing fluorinated phosphates can provide a large amount of lithium difluorophosphate and inorganic components of silicon-oxygen structure, so that the SEI film is both strong and tough, and thinner; it is more conducive to guiding the desolvation of active Li and embedding it into the graphite negative electrode, reducing polarization to suppress the problem of lithium precipitation, reducing interface impedance, and reducing battery expansion, which is beneficial to the high-temperature cycle and storage performance of the battery.

[0068] Further, the cyclic carbonate includes at least one of vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0069] Further, the cyclic sulfate ester includes dithiothreitol disulfide (DTD).

[0070] Further, the cyclic sultone includes 1,3-propane sultone (1,3-PS).

[0071] In the embodiment of the present application, the mass percentage of the film-forming agent in the electrolyte meets the above conditions, which is beneficial to improve the stability of the interface film and improve the battery performance. In a specific example, 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.

[0072] Furthermore, the mass percentage of the film-forming agent in the electrolyte is 0.5% to 2.5%.

[0073] In some embodiments of the present application, the battery includes a positive electrode sheet;

[0074] 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, and the positive electrode active material layer includes a positive electrode active material and a positive electrode lithium supplement material;

[0075] Alternatively, it also includes a lithium replenishing sheet compounded with the positive electrode sheet; the lithium replenishing sheet includes a positive electrode lithium replenishing material, the positive electrode sheet includes a positive electrode collector and a positive electrode active material layer attached to at least one side of the positive electrode collector, and the positive electrode active material layer includes at least a positive electrode active material.

[0076] Furthermore, the positive electrode material is lithium iron phosphate.

[0077] In some embodiments of the present 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 base and a metal layer formed on at least one side of the polymer material base. 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) and other substrates).

[0078] In some embodiments of the present application, the positive electrode active material layer may also optionally include a conductive agent and a binder. A conventional conductive agent in the art may be selected based on actual needs. A conventional binder in the art may be selected based on actual needs.

[0079] In some embodiments of the present application, the positive electrode active material includes at least one of nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material, nickel-cobalt-manganese-aluminum quaternary material, nickel-manganese-aluminum ternary material, lithium cobaltate, lithium manganeseate, lithium iron manganese phosphate and lithium iron phosphate.

[0080] In some embodiments of the present application, the positive electrode active material includes lithium iron phosphate; the electrolyte includes a film-forming additive, and the film-forming additive includes vinylene carbonate.

[0081] In some embodiments of the present application, a negative electrode sheet is also included, the negative electrode sheet includes a negative electrode active material, and the negative electrode active material includes at least one of a carbon material and a silicon material.

[0082] Further, the carbon material includes at least one of natural graphite, artificial graphite, hard carbon and soft carbon.

[0083] Furthermore, the silicon material includes at least one of pure silicon material, silicon-carbon material and silicon-oxygen material.

[0084] In some embodiments of the present 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, and the negative electrode active material layer includes a negative electrode active material.

[0085] In some embodiments of the present application, the negative electrode active material layer may also optionally include a conductive agent and a binder. A conventional conductive agent in the art may be selected based on actual needs. A conventional binder in the art may be selected based on actual needs.

[0086] In the second aspect of the application embodiment, a method for preparing a battery is proposed, specifically a method for preparing the battery provided in the first aspect of the application embodiment, comprising: preparing a positive electrode sheet and preparing an electrolyte;

[0087] The steps of preparing the positive electrode sheet include forming a positive electrode active material layer on the positive electrode current collector using a positive electrode slurry, wherein the positive electrode slurry includes a positive electrode lithium replenishing material, and the positive electrode lithium replenishing material includes at least one of lithium nickelate, lithium ferrite and lithium oxide; the electrolyte includes a silicon-based fluorophosphate compound shown in formula I.

[0088] The battery system prepared in the embodiment of the present application contains a lithium supplement material, which can be activated to release active Li to achieve the effect of lithium supplement. The unreacted lithium supplement material continues to release oxygen free radicals to form oxygen during high-temperature storage. 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 gases caused by oxygen free radicals; on the other hand, the silicon-based fluorophosphate compounds contain silicon groups that can react with residual moisture in the lithium supplement material to form a dense silicon-oxygen polymer containing fluorinated phosphates, which is used to form an SEI film, improve the stability of the interface film, and improve the high-temperature performance of the battery.

[0089] In some embodiments of the present application, the mass percentage of the positive electrode lithium supplement material in the positive electrode slurry is 0.5% to 4%.

[0090] The amount of the positive electrode lithium supplement material added in the embodiment of the present application meets the above conditions, which is conducive to the use with silicon-based fluorophosphate compounds to improve the improvement performance of the positive electrode lithium supplement material on the battery.

[0091] As an example, the mass percentage of the positive electrode lithium supplement 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.

[0092] In some embodiments of the present application, the positive electrode slurry further includes a positive electrode active material, a conductive agent, a binder, and a solvent.

[0093] Specifically, the positive electrode active material, positive electrode lithium supplement material, conductive agent, binder and solvent can be configured into positive electrode slurry, the positive electrode slurry is coated on the positive electrode collector, and then subjected to molding treatment to obtain a positive electrode sheet. Among them, the conductive agent, binder and solvent, positive electrode collector material, etc. can be selected from conventional materials in the field.

[0094] The present invention is described below with reference to specific examples. It should be noted that these examples are merely illustrative and do not limit the present invention in any way. The reagents used in the examples are all from Aladdin Biochemical Technology Co., Ltd.

[0095]

Compound preparation

[0096] 1. Compound represented by formula I-1 The CAS number is: 4419-25-9.

[0097] 2. Compound represented by formula I-2 The CAS number is: 2708941-25-5.

[0098] 3. Compound represented by formula I-3 The CAS number is: 13683-39-1.

[0099] 4. Compound represented by formula I-4 The CAS number is: 4414-27-1.

[0100] 5. Compound represented by formula I-5 The CAS number is: 4414-26-0.

[0101] 6. Compound represented by formula I-6 The CAS number is: 4480-02-8.

[0102] 7. Compound represented by formula I-7 The CAS number is: 2577172-95-1.

[0103] 8. Compound represented by formula I-8 The CAS number is: 13683-40-4.

[0104] 9. Compound represented by formula I-9 The CAS number is: 2577172-93-9.

[0105] 10. Compound represented by formula I-10 The CAS number is: 2708941-27-7.

[0106] 11. Compound represented by formula I-11 The CAS number is: 2287283-36-5.

[0107] 12. Compound represented by formula I-12 The CAS number is: 6231-57-8.

[0108] 13. Compound represented by formula I-13 The CAS number is: 1386-54-9.

[0109] 14. Compound represented by formula I-14 The CAS number is: 2708941-26-6.

[0110] 15. Compound represented by formula I-15 The CAS number is: 6231-58-9.

[0111] 16. Compound represented by formula I-16 The CAS number is: 6231-59-0.

[0112] 17. Compound represented by formula I-17 The CAS number is: 2577172-94-0.

[0113] 18. The compounds represented by formula I-18 to I-22 are prepared by referring to the preparation method of Example 14 in patent CN114728992A. Specifically, the raw materials shown below are used to replace the chlorodimethylphenylsilane in the reference patent.

[0114] Compound represented by formula I-18 The raw material used is trivinyl chlorosilane (CAS No.: 1871-21-2).

[0115] Compound represented by formula I-19 The raw material used is dimethyl butyl chlorosilane (2069196-19-4).

[0116] Compound represented by formula I-20 The raw material used is dimethyl(trifluoropropylene)chlorosilane (89705-02-2).

[0117] Compound represented by formula I-21 The raw material used is tris(pentafluoroethyl)chlorosilane (1620665-21-5).

[0118] Compound represented by formula I-22 The raw material used is dimethyl (p-methylbenzyl) chlorosilane (1833-28-9).

[0119]

Battery preparation

[0120] Example 1

[0121] Positive electrode sheet: The positive electrode active material lithium iron phosphate, lithium supplement agent (lithium-rich iron oxide LFO), conductive agent conductive carbon black super-p and binder (polyvinylidene fluoride) PVDF are dispersed in the solvent NMP (N-methylpyrrolidone) in a mass ratio of 93:3:2:2 (LFO addition amount is 3%) to obtain a positive electrode active material layer slurry; the positive electrode active material layer slurry is evenly coated on the surface of the positive electrode current collector aluminum foil, and the positive electrode sheet is obtained after drying, rolling, baking, slitting and spot welding of the pole ears.

[0122] Negative electrode sheet: The negative electrode active material graphite, the conductive agent conductive carbon black super-p, the binder SBR, and the dispersant sodium hydroxymethyl cellulose (CMC) are dispersed in deionized water at a mass ratio of 95:1.5:2:1.5, and stirred evenly to obtain the 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 the negative electrode sheet is obtained after drying, rolling, baking, slitting and spot welding of the pole ears.

[0123] 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, the addition amount is 2% (mass percentage content); the addition amount of silicon-based fluorophosphate compound is 0.5% (mass percentage content); the lithium salt is lithium hexafluorophosphate, and the concentration is 1 mol / L.

[0124] Diaphragm: Polypropylene / Polyethylene / Polypropylene three-layer composite film (PP / PE / PP).

[0125] Battery: stack the prepared positive electrode sheet, negative electrode sheet and separator in order, place the separator between the positive electrode sheet and the negative electrode sheet, wind them to obtain a battery cell, place the battery cell in an outer package, and inject the above-mentioned electrolyte into the battery cell in a glove box, then let it stand for 24 hours, pre-charge for primary formation, and then seal it. After secondary formation, the preparation of the lithium-ion battery is completed.

[0126] Example 2-Example 44

[0127] The preparation methods of the batteries provided in Examples 2 to 44 are as shown in Example 1, with the differences shown in Tables 1-1 and 1-2.

[0128] Comparative Example 1-Comparative Example 4

[0129] The preparation methods of the batteries provided in Examples 2 to 44 are as shown in Example 1, with the differences shown in Tables 1-1 and 1-2.

[0130] The preparation parameters of the batteries provided by Example 2 to Example 44 and Comparative Example 1 to Comparative Example 4 are shown in Table 1-1 and Table 1-2.

[0131] Table 1-1

[0132]

[0133] Table 1-2

[0134]

[0135] In Table 1-1 and Table 1-2, the ratio of the components of the film-forming additives in Examples 29 to 31, Example 40, and Example 41 is the mass ratio.0.8 Co 0.1 Mn 0.1 O2. "LMFP" stands for lithium manganese iron phosphate.

[0136] 1. Test method:

[0137] 1. Lithium-ion battery 60°C storage test:

[0138] First, after the second seal (gas is removed), the lithium-ion battery is left to stand at 25°C for 30 minutes; it is charged to 3.65V at a constant current of 1C, and further charged to a current of 0.05C at a constant voltage of 3.65V; then the lithium-ion battery is discharged to 2.0V at a constant current of 1C, and the discharge capacity at this time is recorded as C0; it is then charged to 3.65V at a constant current of 1C, and further charged to a current of 0.05C at a constant voltage of 3.65V; finally, the volume of the battery is tested by the drainage method, which is the volume before storage V0. The lithium-ion battery is then stored at 60°C for 30 days. After the storage is completed, the lithium-ion secondary battery is placed in an environment of 25°C, and the volume of the battery is tested by the drainage method, which is the volume after storage V 30 Then the lithium-ion battery is discharged at a constant current of 1C to 2.0V. The discharge capacity at this time is recorded as C' 30 ; Then charge the lithium-ion secondary battery to 3.65V at a constant current of 1C, and further charge it at a constant voltage of 3.65V to a current of 0.05C; then discharge the lithium-ion secondary battery to 2.0V at a constant current of 1C, and the discharge capacity at this time is recorded as C 30 .

[0139] Storage capacity retention rate after 30 days of lithium ion storage (%) = C' 30 / C0;

[0140] Storage capacity recovery rate after 30 days of lithium ion storage (%) = C 30 / C0;

[0141] Volume expansion rate of lithium-ion battery after 30 days of storage (%) = (V 30 V0) / V0.

[0142] 2. High temperature storage DCR performance test:

[0143] After the battery was left at 25°C for 30 minutes, a discharge DC internal resistance (DCIR) test was performed on the battery, which was recorded as R0. The battery was then stored at 60°C for 30 days. After the storage period, the battery was placed in a 25°C environment and a discharge DC internal resistance (DCIR) test was performed on the battery, which was recorded as R 30

[0144] 3. 45℃ cycle performance test:

[0145] The test method is: in a 45℃±1℃ constant temperature box, charge the lithium-ion battery to 3.65V at 1C constant current and constant voltage, cut off the current at 0.05C, and then discharge it to 2.0V at 1C. Perform multiple charge and discharge cycles under the above conditions. Calculate the capacity retention rate of the battery after 500 cycles.

[0146] 4. The proportion of lithium deposition area at the negative electrode interface of the battery:

[0147] Before and after the cycle, the battery was disassembled, the area of ​​the lithium deposition region on the interface was recorded, and its area share in the entire negative electrode interface was calculated.

[0148] 2. Test results:

[0149] The performance test results of the batteries provided in Examples 1 to 44 and Comparative Examples 1 to 4 are shown in Tables 2-1 and 2-2.

[0150] Table 2-1

[0151]

[0152] Table 2-2

[0153]

[0154] From the performance test results, it can be seen that the use of silicon-based fluorophosphate compounds as deoxidizers for positive lithium supplement materials is beneficial to improving the high temperature performance of the battery and solving the gas expansion and lithium precipitation problems caused by oxygen production in lithium supplement material batteries. By optimizing the dosage of silicon-based fluorophosphate compounds, active oxygen can be fully absorbed and silicon-oxygen phosphate polymers can be generated to form a high-quality and thin SEI film, which can further improve the cycle performance.

[0155] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0156] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A battery, characterized in that: Including: positive electrode and electrolyte; The positive electrode sheet includes a positive electrode lithium supplement material, and the positive electrode lithium supplement material includes at least one of lithium nickelate, lithium ferrite and lithium oxide; The electrolyte comprises a silicon-based fluorophosphate compound as shown in 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 cycloalkane, R4 substituted phenyl or R5 substituted benzyl; R4 and R5 are independently C1-C4 alkyl, C2-C4 alkene, C2-C4 alkynyl, C1-C4 fluoroalkyl, C2-C4 fluoroalkenyl or C2-C4 fluoroalkynyl.

2. The battery according to claim 1, characterized in that In the 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 cycloalkane, R4 substituted phenyl, or R5 substituted benzyl; R4 and R5 are each independently selected from any one of -CH3 and F.

3. The battery according to claim 1, characterized in that The silicon-based fluorophosphate compound represented by formula I comprises at least one of the following compounds: The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown, The compounds shown.

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

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

6. The battery according to claim 1, characterized in that The electrolyte further comprises a solvent and a lithium salt; the electrolyte satisfies at least one of the following: (i) the solvent comprises at least one of a carbonate solvent, a carboxylate solvent and an ether solvent; (ii) the lithium salt comprises at least one of LiPF6, LiFSI, LiTFSI and LiBF4; (iii) The mass percentage of the lithium salt in the electrolyte is 8% to 18%.

7. The battery according to claim 1, characterized in that The electrolyte further includes a film former, and the film former satisfies: the film former includes at least one of cyclic carbonate, cyclic sulfate or cyclic sultone; and / or the mass percentage of the film former in the electrolyte is 0.1% to 3%.

8. The battery according to claim 1, characterized in that Including positive electrode; The positive electrode sheet comprises 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, wherein the positive electrode active material layer comprises a positive electrode active material and a positive electrode lithium supplement material; Alternatively, it also includes a lithium replenishing sheet compounded with the positive electrode sheet; the lithium replenishing sheet includes a positive electrode lithium replenishing material, 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, and the positive electrode active material layer includes at least a positive electrode active material.

9. The battery according to claim 8, characterized in that The positive electrode active material includes at least one of a nickel-cobalt-manganese ternary material, a nickel-cobalt-aluminum ternary material, a nickel-cobalt-manganese-aluminum quaternary material, a nickel-manganese-aluminum ternary material, lithium cobaltate, lithium manganeseate, lithium iron manganese phosphate and lithium iron phosphate.

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

11. The battery according to claim 1, characterized in that The invention also includes a negative electrode sheet, wherein the negative electrode sheet includes a negative electrode active material, and the negative electrode active material includes at least one of a carbon material and a silicon material.

12. A method for preparing a battery according to any one of claims 1 to 11, characterized in that: include: 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, wherein the positive electrode slurry includes a positive electrode lithium replenishing material, and the positive electrode lithium replenishing material includes at least one of lithium nickelate, lithium ferrite and lithium oxide; the electrolyte includes a silicon-based fluorophosphate compound shown in formula I.

13. The method according to claim 12, characterized in that The mass percentage of the positive electrode lithium supplement material in the positive electrode slurry is 0.5% to 4%.

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