A lithium-ion battery and its application

Abstract

This invention relates to the field of battery technology and discloses a lithium-ion battery and its application. The lithium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive current collector and a positive electrode material disposed on at least one side of the current collector. The electrolyte includes a lithium salt, an organic solvent, a fluorinated cyclic ether, and an α,ω-dianitronic organic compound. The fluorinated cyclic ether is tetrahydrofuran containing 4-6 fluorine atoms substituted and / or tetrahydropyran containing 4-6 fluorine atoms substituted. The fluorinated cyclic ether of this invention can improve the cycle life of lithium-ion batteries and forms a polar complementary solvation network with the α,ω-dianitronic organic compound. The cyano group of the dianitronic compound preferentially chelates metal ions, while the fluorinated cyclic ether coats the surface of the lithium replenishing agent. The two work synergistically to avoid mutual interference and maintain the overall ionic conductivity and interfacial wettability of the electrolyte, achieving synergistic optimization of high-temperature gas generation and long cycle life.

Description

Technical Field

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

[0002] Lithium iron phosphate (LiFePO4) batteries have become the mainstream choice for power batteries and energy storage batteries due to their high safety, long cycle life and low cost. However, the formation of the solid electrolyte interphase (SEI) film on the negative electrode during the first charge and discharge will consume a large amount of active lithium, which limits the battery's energy density and cycle life.

[0003] In pre-lithiation technology, cathode lithium replenishment agents have become the preferred approach due to their compatibility with existing production lines. Among them, lithium-rich lithium iron phosphate (Li5FeO4, LFO) has become a research hotspot due to its high lithium replenishment capacity of ~700mAh / g. However, existing technologies only focus on "lithiation capacity gain" and do not address the side effects of LFO: LFO releases highly reactive oxygen species during delithiation, which attack the electrolyte, causing severe oxidation and decomposition gas production, metal ion dissolution, and interface instability, leading to battery swelling, increased interface impedance, and ultimately capacity decay and shortened lifespan. Furthermore, existing technologies are mostly a positive superposition of "lithiation replenishment agent + single component," resulting in poor high-temperature storage performance.

[0004] Therefore, how to prepare lithium-ion batteries that combine large capacity, long cycle life, and good high-temperature storage performance is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This invention provides a lithium-ion battery to solve the problems of poor cycle performance and high-temperature storage performance of existing lithium-ion batteries.

[0006] In a first aspect, the present invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive current collector and a positive electrode material disposed on at least one side surface of the positive current collector. The positive electrode material includes a positive active material and a lithium replenishing agent. The electrolyte includes a lithium salt, an organic solvent, a fluorinated cyclic ether, and an α,ω-diacetonitrile organic compound. The mass ratio of the fluorinated cyclic ether to the α,ω-diacetonitrile organic compound is (2.0-3.5):1. The fluorocyclic ether is a tetrahydrofuran containing 4-6 fluorine atoms substituted and / or a tetrahydropyran containing 4-6 fluorine atoms substituted.

[0007] In one optional embodiment, the mass ratio of the fluorocyclic ether to the α,ω-dianitronic organic compound is (2.8-3.5):1.

[0008] In one optional embodiment, the tetrahydrofuran containing 4-6 fluorine atoms includes at least one of 2,2,3,3-tetrafluorotetrahydrofuran, 2,2,3,3,4-pentafluorotetrahydrofuran, and 2,2,3,3,4,4-hexafluorotetrahydrofuran; preferably 2,2,3,3-tetrafluorotetrahydrofuran or 2,2,3,3,4-pentafluorotetrahydrofuran.

[0009] In one alternative embodiment, the tetrahydropyran containing 4-6 fluorine atoms includes at least one of 2,2,3,3,4,4-hexafluorotetrahydropyran, 2,2,3,3-tetrafluorotetrahydropyran, and 2,2,3,3,4-pentafluorotetrahydropyran.

[0010] In one optional embodiment, the α,ω-dianitronic organic compound includes at least one of adiponitrile and octanoic acid; preferably adiponitrile.

[0011] In one optional embodiment, the lithium replenishing agent includes a first lithium replenishing agent and a second lithium replenishing agent, wherein the first lithium replenishing agent is Li5FeO4 and the second lithium replenishing agent is Li 2+x Ni 1-x O2; where 0≤x≤0.1, preferably 0≤x≤0.05.

[0012] In one optional embodiment, the mass ratio of the first lithium replenisher to the second lithium replenisher is R, where R is 1-5.

[0013] In one optional embodiment, the total mass content of the first lithium supplement and the second lithium supplement in the positive electrode material is w. PR %, w PR 0.5wt%-5wt%; w PR The preferred concentration is 2.5wt%-5wt%.

[0014] In one optional embodiment, the mass content of the fluorocyclic ether is C. FE %, 12%-2%×(R / (1+R))×w PR ≤C FE %≤12%+2%×(R / (1+R))×w PR .

[0015] In one optional embodiment, the mass content of the α,ω-dianitronic organic compound is C. DN %, 3.5% + 0.25% × (w PR ×(1+0.6R) / (1+R))-0.5%≤C DN %≤3.5%+0.25%×(w PR ×(1+0.6R) / (1+R))+0.5%.

[0016] In one optional embodiment, the content of the fluorocyclic ether in the electrolyte is 10wt%-20wt%; preferably 11wt%-16wt%.

[0017] In one optional embodiment, the content of the α,ω-dianitronic organic compound is 3wt%-5wt%; preferably 4wt%-5wt%.

[0018] In one optional embodiment, the lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorosulfonylimide, lithium perchlorate, lithium tetrafluoroborate, lithium dioxalate borate, and lithium difluorooxalate borate.

[0019] In one optional embodiment, the lithium salt content is 12wt%-16wt%, preferably 13wt%-15wt%.

[0020] In one alternative embodiment, the organic solvent includes at least two of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene sulfite, and ethyl acetate.

[0021] In one alternative embodiment, the electrolyte further includes the addition of additives.

[0022] In one alternative embodiment, the additive includes fluorinated lithium salt film-forming additives and acid neutralizers.

[0023] In one optional embodiment, the fluorinated lithium salt film-forming additive includes at least one of lithium difluorophosphate, lithium difluorooxalate borate, and lithium difluorobis(oxalate) phosphate; preferably lithium difluorophosphate.

[0024] In one optional embodiment, the acid neutralizing agent includes at least one of trimethylsilane phosphate, triethylsilane phosphate, and trimethylsilane phosphite; preferably trimethylsilane phosphate.

[0025] In one optional embodiment, the mass ratio of the fluorinated lithium salt film-forming additive to the acid neutralizer is (0.4-1.2):1; preferably (1-1.2):1.

[0026] In one optional embodiment, the content of the fluorinated lithium salt film-forming additive is 0.1wt%-2wt%; preferably 1wt%-1.2wt%.

[0027] In one optional embodiment, the content of the acid neutralizing agent is 0.3wt%-2wt%; preferably 0.5wt%-1.5wt%.

[0028] In one alternative embodiment, the positive electrode material further includes a first conductive agent, a first binder, and a dispersant.

[0029] In one alternative embodiment, the first conductive agent includes at least one of conductive carbon black, acetylene black, Ketjen black, and carbon nanotubes.

[0030] In one alternative embodiment, the adhesive includes at least one of polyvinylidene fluoride and polyacrylic acid.

[0031] In one alternative embodiment, the dispersant includes at least one of polyacrylic acid, polyethylene glycol, carboxymethyl cellulose, and polyvinylpyrrolidone.

[0032] In one alternative embodiment, the content of the first conductive agent in the positive electrode material is 0.2wt%-4wt%.

[0033] In one alternative embodiment, the content of the first binder in the positive electrode material is 1wt%-2.5wt%.

[0034] In one alternative embodiment, the content of the dispersant in the positive electrode material is 0.1wt%-0.3wt%.

[0035] In one optional embodiment, the negative electrode sheet includes a negative current collector and a negative electrode material disposed on at least one side surface of the negative current collector, wherein the negative electrode material includes graphite, a second conductive agent, and a second binder.

[0036] In one optional embodiment, the second conductive agent includes at least one of conductive carbon black and carbon nanotubes.

[0037] In one alternative embodiment, the second adhesive comprises at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber, sodium alginate, and polyacrylic acid.

[0038] In one alternative embodiment, the content of the second conductive agent in the negative electrode material is 0.5wt%-2wt%.

[0039] In one alternative embodiment, the content of the second binder in the negative electrode material is 1.5wt%-4.5wt%.

[0040] Secondly, the present invention provides an application of the lithium-ion battery described in the first aspect in an electrical device.

[0041] The technical solution of this invention has the following advantages: 1. The fluorinated cyclic ether in the lithium-ion battery electrolyte provided by this invention contains 4-6 fluorine atoms, which reduces the electron cloud density of the ether oxygen atom and weakens its effect on Li.+ The fluorine atom enhances the coordination ability of the lithium replenisher, thereby preferentially adsorbing active sites (such as oxygen vacancies and unsaturated metal sites) on the surface of the lithium replenisher. Simultaneously, the steric hindrance effect of the fluorine atom forms a local physical barrier on the surface of the lithium replenisher particles, physically preventing solvent molecules in the electrolyte from contacting the lithium replenisher surface. This significantly inhibits the release of reactive oxygen species (including singlet oxygen), effectively mitigating subsequent chain oxidation reactions in the electrolyte and achieving precise suppression of oxygen release behavior and transition metal dissolution from the lithium replenisher. Compared to common fluorinated solvents (such as monofluorocarbonates), the fluorinated cyclic ether of this invention provides a denser surface coverage and stronger chemical inertness, forming a stable protective layer on the surface of the lithium replenisher particles and improving the cycle life of lithium-ion batteries. Furthermore, the fluorinated cyclic ether forms a polar complementary solvation network with α,ω-dianitronic organic compounds. The cyano groups of the dianitronic compounds preferentially chelate metal ions, while the fluorinated cyclic ether encapsulates the surface of the lithium replenisher. The two work synergistically to avoid mutual interference and maintain the overall ionic conductivity and interfacial wettability of the electrolyte, achieving synergistic optimization of high-temperature gas generation and long cycle life.

[0042] 2. In the lithium-ion battery provided by the present invention, the mass content of the fluorinated cyclic ether in the electrolyte is C. FE %, (12%-2%×(R / (1+R))×w PR )≤C FE %≤(12%+2%×(R / (1+R))×w PR The mass content of α,ω-dianitronic organic compounds is C. DN %, 3.5% + 0.25% × (w PR ×(1+0.6R) / (1+R))-0.5%)≤C DN %≤(3.5%+0.25%×(w PR ×(1+0.6R) / (1+R))+0.5%); The dosage of fluorinated cyclic ethers and α,ω-dianitronics is not fixed, but depends on two core parameters of the lithium supplement: the mass ratio R and the total content w. PR Dynamic calculations are performed to achieve precise adaptation to different lithium supplementation systems. The dosage range of fluorinated cyclic ethers is determined by the higher the proportion of Li5FeO4 in the lithium supplementation (larger R) or the higher the total amount of lithium supplementation added (w...). PR When the concentration of oxygen increases (to a higher level), the risk of oxygen release increases, thus increasing the C content. FE To ensure adequate coverage of the active surface, use more fluorocyclic ethers, considering the upper and lower limits of the lithium supplement. Conversely, if the lithium supplement is insufficient or R is small, C can be appropriately reduced. FE To control electrolyte viscosity. The dosage range of α,ω-dianitronic organic compounds; the larger R is, the better the transition metal ion (Ni). 2+ Fe 3+ The larger the total amount, and w PRAt higher temperatures, more dinitrile compounds are needed to chelate metal ions and prevent them from catalyzing electrolyte decomposition. Fluorinated cyclic ethers and α,ω-dianitriles achieve synergistic optimization for high-temperature gas production and long cycle life. Detailed Implementation

[0043] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.

[0044] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0045] To address the aforementioned problems, in a first aspect, the present invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive current collector and a positive electrode material disposed on at least one surface of the positive current collector. The positive electrode material includes a positive active material and a lithium replenishing agent. The electrolyte includes a lithium salt, an organic solvent, a fluorinated cyclic ether, and an α,ω-diacetonitrile organic compound. The mass ratio of the fluorinated cyclic ether to the α,ω-diacetonitrile organic compound is (2.0-3.5):1. The fluorocyclic ether is a tetrahydrofuran containing 4-6 fluorine atoms substituted and / or a tetrahydropyran containing 4-6 fluorine atoms substituted.

[0046] Further, as an example, the mass ratio of the fluorocyclic ether to the α,ω-diacetonide organic compound can be 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3.0:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1, or 3.5:1.

[0047] It should be noted that when the mass ratio of fluorinated cyclic ethers and α,ω-dianitronic organic compounds is controlled within the range of (2.0-3.5):1, a polarity-complementary solvation network can be formed, optimizing the electrolyte viscosity, ionic conductivity and electrode wettability, and synergistically constructing a stable electrode interface film.

[0048] In one optional embodiment, the mass ratio of the fluorocyclic ether to the α,ω-dianitronic organic compound is (2.8-3.5):1.

[0049] In one optional embodiment, the tetrahydrofuran containing 4-6 fluorine atoms includes at least one of 2,2,3,3-tetrafluorotetrahydrofuran, 2,2,3,3,4-pentafluorotetrahydrofuran, and 2,2,3,3,4,4-hexafluorotetrahydrofuran; preferably 2,2,3,3-tetrafluorotetrahydrofuran (CAS No. 13472-16-7) or 2,2,3,3,4-pentafluorotetrahydrofuran (CAS No. 204391-86-6).

[0050] In one alternative embodiment, the tetrahydropyran containing 4-6 fluorine atoms includes at least one of 2,2,3,3,4,4-hexafluorotetrahydropyran, 2,2,3,3-tetrafluorotetrahydropyran, and 2,2,3,3,4-pentafluorotetrahydropyran.

[0051] In one optional embodiment, the α,ω-dianitronic organic compound includes at least one of adiponitrile and octanoic acid; preferably adiponitrile.

[0052] In one optional embodiment, the lithium replenishing agent includes a first lithium replenishing agent and a second lithium replenishing agent, wherein the first lithium replenishing agent is Li5FeO4 and the second lithium replenishing agent is Li 2+x Ni 1-x O2, preferably 0 ≤ x ≤ 0.05; where 0 ≤ x ≤ 0.1. As an example, x can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1.

[0053] In one optional embodiment, the mass ratio of the first lithium replenisher to the second lithium replenisher is R, where R is 1-5. As an example, R can be 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5.

[0054] In one optional embodiment, the total mass content of the first lithium supplement and the second lithium supplement in the positive electrode material is w. PR %, w PR The percentage is 0.5wt%-5wt%. As an example, w PR The percentage can be 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, or 5wt%.

[0055] In one optional embodiment, the mass content of the fluorocyclic ether in the electrolyte is C. FE %, (12%-2%×(R / (1+R))×w PR )≤C FE ≤(12%+2%×(R / (1+R))×w PR).

[0056] It should be noted that by controlling the content of fluorinated cyclic ethers within the above range, the dosage can be adaptively matched according to the ratio of composite lithium supplement and the doping content, so that the fluorinated cyclic ether molecules can be fully adsorbed and spread on the surface of the lithium supplement and completely coat the active sites, effectively inhibiting oxygen release and gas production and metal ion dissolution; at the same time, it avoids the defects of excessive addition causing excessively high electrolyte viscosity, obstructed ion conduction, and poor electrode wetting.

[0057] In one optional embodiment, the mass content of the α,ω-dianitronic organic compound is C. DN %, 3.5% + 0.25% × (w PR ×(1+0.6R) / (1+R))-0.5%≤C DN ≤3.5%+0.25%×(w PR ×(1+0.6R) / (1+R))+0.5%.

[0058] It should be noted that limiting the content of α,ω-dianitronic organic compounds to the above range allows for the chelation of Fe dissolved from the lithium supplement by utilizing the strong coordination effect of the cyano group. 3+ Ni 2+ Transition metal ions inhibit catalytic decomposition and acidic side reactions in the electrolyte; simultaneously, they synergistically form a stable solvation network with fluorinated cyclic ethers, stabilizing the electrode interface. Appropriate content fully leverages the passivation and side-resistance effects of metal ions while avoiding excessive addition that could lead to excessively high electrolyte viscosity, increased interfacial side reactions, and decreased battery cycle and rate performance.

[0059] It should be noted that in calculating C FE and C DN At that time, w PR Substitute the percentage value, for example, w PR =2.5% then input 2.5.

[0060] In one optional embodiment, the content of the fluorocyclic ether in the electrolyte is 10wt%-20wt%; preferably 11wt%-16wt%. As an example, the content of the fluorocyclic ether can be 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, or 20wt%.

[0061] In one optional embodiment, the content of the α,ω-dianitronic organic compound in the electrolyte is 3wt%-5wt%; preferably 4wt%-5wt%. As an example, the content of the α,ω-dianitronic organic compound is 3wt%, 3.5wt%, 4wt%, 4.5wt%, or 5wt%.

[0062] In one optional embodiment, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium di(oxalate-borate) (LiBOB), and lithium di(fluorooxalate-borate) (LiODFB); preferably, the lithium salt is lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, and the mass ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide is 1:0.1-1.

[0063] In one optional embodiment, the lithium salt content in the electrolyte is 12wt%-16wt%, preferably 13wt%-15wt%. As an example, the lithium salt content can be 12wt%, 12.5wt%, 13wt%, 13.5wt%, 14wt%, 14.5wt%, 15wt%, 15.5wt%, or 16wt%.

[0064] In one optional embodiment, the organic solvent includes at least two selected from ethylene carbonate (EC), propylene carbonate, dimethyl carbonate, diethyl carbonate (DEC), methyl ethyl carbonate (EMC), propylene sulfite, and ethyl acetate; preferably, the organic solvent is ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate, and the total content of the organic solvent is the balance in the electrolyte excluding the lithium salt, the fluorinated cyclic ether, the α,ω-diacetonitrile organic compound, and the additive; based on the total mass of the electrolyte, the content of ethylene carbonate is... The content of ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate is 10wt%-25wt%, 30wt%-50wt%, and 10wt%-25wt%. Preferably, the mass ratio of ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate is (2-4):(3.5-6):(1-2.5). As an example, the mass ratio of ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate can be 2.5:5.5:2, 2.5:6:1, 2.5:3.5:1, 4:6:2, 4:6:1, 3:6:1.5, or 3:3.5:1.

[0065] In one alternative embodiment, the electrolyte also includes additives.

[0066] In one alternative embodiment, the additive includes fluorinated lithium salt film-forming additives and acid neutralizers.

[0067] In one optional embodiment, the fluorinated lithium salt film-forming additive includes at least one of lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate, and lithium difluorobis(oxalate) phosphate; preferably lithium difluorophosphate.

[0068] In one optional embodiment, the acid neutralizing agent includes at least one of trimethylsilane phosphate (TMSP), triethylsilane phosphate, and trimethylsilane phosphite; preferably trimethylsilane phosphate.

[0069] In one optional embodiment, the mass ratio of the fluorinated lithium salt film-forming additive to the acid neutralizer is (0.4-1.2):1; preferably (1-1.2):1. As an example, the mass ratio of the fluorinated lithium salt film-forming additive to the acid neutralizer can be 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, or 1.2:1.

[0070] It should be noted that by controlling the mass ratio of fluorinated lithium salt film-forming additives and the acid neutralizer within the range of (0.4-1.2):1, a dense and stable solid electrolyte interphase (CEI / SEI) film can be synergistically constructed at the electrode interface, and acidic substances in the system can be neutralized, thereby achieving dynamic repair and protection of the interface.

[0071] In one optional embodiment, the positive electrode active material includes at least one of lithium iron phosphate, lithium manganese iron phosphate, and lithium-rich manganese-based positive electrode materials.

[0072] In one optional embodiment, the content of the fluorinated lithium salt film-forming additive is 0.1wt%-2wt%; preferably 1wt%-1.2wt%. As an example, the content of the fluorinated lithium salt film-forming additive may be 0.1wt%, 0.3wt%, 0.5wt%, 0.7wt%, 0.9wt%, 1.1wt%, 1.3wt%, 1.5wt%, 1.7wt%, 1.9wt%, or 2wt%.

[0073] In one optional embodiment, the content of the acid neutralizing agent is 0.3wt%-2wt%; preferably 0.5wt%-1.5wt%. As an example, the content of the acid neutralizing agent is 0.3wt%, 0.5wt%, 0.7wt%, 0.9wt%, 1.1wt%, 1.3wt%, 1.5wt%, 1.7wt%, 1.9wt%, or 2wt%.

[0074] In one alternative embodiment, the positive electrode material further includes a first conductive agent, a first binder, and a dispersant.

[0075] In one alternative embodiment, the first conductive agent includes at least one of conductive carbon black, acetylene black, Ketjen black, and carbon nanotubes.

[0076] In one alternative embodiment, the first adhesive comprises at least one of polyvinylidene fluoride and polyacrylic acid.

[0077] In one alternative embodiment, the dispersant includes at least one of polyacrylic acid, polyethylene glycol, carboxymethyl cellulose, and polyvinylpyrrolidone.

[0078] In one alternative embodiment, the content of the first conductive agent in the positive electrode material is 0.2wt%-4wt%.

[0079] In one alternative embodiment, the content of the first binder in the positive electrode material is 1wt%-2.5wt%.

[0080] In one alternative embodiment, the content of the dispersant in the positive electrode material is 0.1wt%-0.3wt%.

[0081] In one optional embodiment, the negative electrode sheet includes a negative current collector and a negative electrode material disposed on at least one side surface of the negative current collector, wherein the negative electrode material includes graphite, a second conductive agent, and a second binder.

[0082] In one optional embodiment, the second conductive agent includes at least one of conductive carbon black and carbon nanotubes.

[0083] In one optional embodiment, the second adhesive comprises at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber, sodium alginate, and polyacrylic acid; preferably, sodium carboxymethyl cellulose and styrene-butadiene rubber are in a mass ratio of (0.5-1.5):(1-3).

[0084] In one alternative embodiment, the content of the second conductive agent in the negative electrode material is 0.5wt%-2wt%.

[0085] In one alternative embodiment, the content of the second binder in the negative electrode material is 1.5wt%-4.5wt%.

[0086] It should be noted that, in this invention, the method for preparing a lithium-ion battery includes the following steps: (1) A positive electrode slurry is prepared by dispersing the positive electrode active material, lithium supplementing agent, first conductive agent, first binder and dispersant in a solvent; the positive electrode slurry is transferred to a coating device and uniformly coated on an aluminum foil current collector, and after drying, rolling and cutting, a pre-lithiated positive electrode sheet is obtained; wherein, the solid content of the positive electrode slurry is 55wt%-75wt%; (2) Artificial graphite, a second conductive agent, and a second binder are dispersed in deionized water and mixed to obtain a negative electrode slurry; the negative electrode slurry is coated onto copper foil, and after drying, rolling, and slitting, the negative electrode sheet is obtained; wherein the solid content of the negative electrode slurry is 45wt%-55wt%; (3) Assemble the pre-lithiated positive electrode, negative electrode and separator, inject electrolyte, and obtain lithium-ion battery by forming and compatibility testing.

[0087] Secondly, the present invention provides an application of the lithium-ion battery described in the first aspect in an electrical device.

[0088] In this invention, the conductive carbon black was purchased from Temico, Switzerland, and its model name is Super P Li; the polyvinylidene fluoride was purchased from Arkema, France, and its model name is HSV900; the styrene-butadiene rubber was purchased from Zeon, Japan, and its model name is BM-451; and the polyvinylpyrrolidone was purchased from Ashland, and its model name is PVP K30.

[0089] Example 1 This embodiment provides a method for preparing a lithium-ion battery, including the following steps: (1) Preparation of positive electrode: Lithium iron phosphate, Li5FeO4, Li2NiO2, conductive carbon black, polyvinylidene fluoride, and polyvinylpyrrolidone were dispersed in N-methylpyrrolidone to obtain a positive electrode slurry with a solid content of 60 wt%. The positive electrode slurry was transferred to a coating device and uniformly coated onto an aluminum foil current collector. After drying, rolling, and slitting, a pre-lithiated positive electrode sheet was obtained. The total content of Li5FeO4 and Li2NiO2 in the positive electrode material was wt%. PR The content of the active carbon black is 2.5wt%, the mass ratio of Li5FeO4 to Li2NiO2 is R = 3, the contents of conductive carbon black, polyvinylidene fluoride and polyvinylpyrrolidone are 1.5wt%, 1.7wt% and 0.2wt% respectively, and the balance is lithium iron phosphate. (2) Anode preparation: Artificial graphite, conductive carbon black, sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are dispersed in deionized water and mixed evenly to obtain a negative electrode slurry with a solid content of 50 wt%. The negative electrode slurry is coated onto copper foil, and after drying, rolling, and slitting, the negative electrode sheet is obtained. In the negative electrode slurry, the contents of conductive carbon black, sodium carboxymethyl cellulose, and styrene-butadiene rubber are 0.5 wt%, 1.2 wt%, and 1.8 wt%, respectively, with artificial graphite as the balance. (3) Electrolyte: The electrolyte was prepared by mixing lithium salts (LiPF6 and LiFSI), organic solvents (EC, EMC, and DEC in a mass ratio of 25:55:20), 2,2,3,3-tetrafluorotetrahydrofuran, adiponitrile, LiPO2F2, and TMSP; wherein the contents of LiPF6, LiFSI, organic solvents, 2,2,3,3-tetrafluorotetrahydrofuran, adiponitrile, LiPO2F2, and TMSP were 10 wt%, 4 wt%, 66.5 wt%, 11.5 wt%, 4.0 wt%, 1.0 wt%, and 1.0 wt%, respectively. (4) Battery assembly: The pre-lithiated positive electrode, negative electrode, and separator are assembled, injected with electrolyte, and then subjected to formation and capacity testing to obtain a lithium-ion battery.

[0090] Example 2 This embodiment provides a method for preparing a lithium-ion battery, which is basically the same as the steps in Embodiment 1, except that the lithium supplement includes Li5FeO4 and Li2NiO2 in a mass ratio of 1:1, and the total content of the lithium supplement is w PR The content of 2,2,3,3-tetrafluorotetrahydrofuran is 14.5 wt%, adiponitrile is 4.8 wt%, LiPO2F2 is 1.2 wt%, and TMSP is 1 wt%.

[0091] Example 3 This embodiment provides a method for preparing a lithium-ion battery, which is basically the same as the steps in Embodiment 1, except that the lithium supplement includes Li5FeO4 and Li2NiO2 in a mass ratio of 5:1, and the total content of the lithium supplement is w PR The content of 2,2,3,3-tetrafluorotetrahydrofuran is 12wt%, the content of adiponitrile is 3.6wt%, the content of LiPO2F2 is 0.5wt%, and the content of TMSP is 1.2wt%.

[0092] Example 4 This embodiment provides a method for preparing a lithium-ion battery, which is basically the same as the steps in Embodiment 1, except that 2,2,3,3-tetrafluorotetrahydrofuran is replaced with the same mass of 2,2,3,3,4-pentafluorotetrahydrofuran.

[0093] Example 5 This embodiment provides a method for preparing a lithium-ion battery, which is basically the same as the steps in Embodiment 1, except that adiponitrile is replaced with the same mass of octadionitrile.

[0094] Example 6 This embodiment provides a method for preparing a lithium-ion battery, which is basically the same as the steps in Embodiment 1, except that LiPO2F2 and TMSP are not added to the electrolyte, and the content of 2,2,3,3-tetrafluorotetrahydrofuran is 15.5 wt% and the content of adiponitrile is 4.5 wt%; the lithium supplement includes Li5FeO4 and Li2NiO2 in a mass ratio of 5:1, and the total content of the lithium supplement is w PR It is 5 wt%.

[0095] Comparative Example 1 This comparative example provides a method for preparing a lithium-ion battery, which is basically the same as the steps in Example 1, except that in step (1), the lithium replenishing agents Li5FeO4 and Li2NiO2 are replaced with the same mass of lithium iron phosphate.

[0096] Comparative Example 2 This comparative example provides a method for preparing a lithium-ion battery, which is basically the same as the steps in Example 1, except that in step (3), the addition of 2,2,3,3-tetrafluorotetrahydrofuran and adiponitrile is omitted.

[0097] Comparative Example 3 This comparative example provides a method for preparing a lithium-ion battery, which is basically the same as the steps in Example 1, except that in step (3), 2,2,3,3-tetrafluorotetrahydrofuran is replaced with the same mass of adiponitrile.

[0098] Comparative Example 4 This comparative example provides a method for preparing a lithium-ion battery, which is basically the same as the steps in Example 1, except that in step (3), adiponitrile is replaced with the same mass of 2,2,3,3-tetrafluorotetrahydrofuran.

[0099] Comparative Example 5 This comparative example provides a method for preparing a lithium-ion battery, which is basically the same as the steps in Example 1, except that in step (3), the content of 2,2,3,3-tetrafluorotetrahydrofuran is 15.75wt% and the content of adiponitrile is 3.5wt%.

[0100] Comparative Example 6 This comparative example provides a method for preparing a lithium-ion battery, which is basically the same as the steps in Example 1, except that in step (3), the content of 2,2,3,3-tetrafluorotetrahydrofuran is 8.25wt% and the content of adiponitrile is 4.3wt%.

[0101] Comparative Example 7 This comparative example provides a method for preparing a lithium-ion battery, which is basically the same as the steps in Example 1, except that 2,2,3,3-tetrafluorotetrahydrofuran is replaced with the same mass of 3-fluorotetrahydrofuran (1362119-98-9).

[0102] Experimental Example The 2Ah pouch cells prepared in Examples 1-6 and Comparative Examples 1-7 were charged at a constant current and constant voltage rate of 0.33C to 3.65V (cutoff current 0.05C) to bring them to 100% SOC. Their initial volume (V0) was measured using a cell volume expansion rate tester (DahoMete DH-2000G-T). Subsequently, the cells were stored in a 60°C high-temperature test chamber for 7 days. On the 7th day of storage, the cells were removed and cooled to a 25°C environment for 2 hours, and their volume after storage (V0) was measured again. n ), calculate the volume growth rate, volume growth rate = (V n -V0) / V0×100%, the results are shown in Table 1.

[0103] The soft-pack battery cells with a rated capacity of 2Ah prepared in Examples 1-6 and Comparative Examples 1-7 were discharged at 25°C and then constant-current charged at a charging current of 1C to a voltage of 3.65V. After that, the cells were allowed to stand for 15 minutes at a constant charging current of 0.05C under a constant voltage of 3.65V, and then constant-current discharged at a discharging current of 1C to a voltage of 2.5V. The discharge capacity of the first cycle was recorded as C1. Then, 1000 charge and discharge cycles were performed, and the discharge capacity C of the 1000th cycle was recorded. 1000 Calculate the discharge capacity retention rate after 1000 cycles. Capacity retention rate = C 1000 / C1×100%, the results are shown in Table 1.

[0104] Table 1 Electrical performance test results

[0105] As can be seen from Table 1, the lithium-ion batteries prepared in Examples 1-6 all showed a volume growth rate of ≤6.2% after 7 days of storage at 60℃, and a capacity retention rate of ≥87.0% after 1000 cycles at 1C / 1C.

[0106] Among them, the volume growth rate of Examples 1-5 was only 2.1%-3.2%, and the capacity retention rate was as high as 91.5%-96.0%, indicating that the present invention, through the synergistic design of composite lithium replenishing agent and electrolyte, can effectively replenish lithium while significantly suppressing oxygen release and gas production and maintaining interface stability, thus achieving a balance between high capacity retention and low-temperature gas production.

[0107] Although the volume growth rate of Example 6 (without additives) increased to 6.2% and the capacity retention decreased to 87.1%, it was still better than the comparative example, proving that the synergistic solvent network composed of fluorinated cyclic ethers and α,ω-dianitronic organic compounds can still play a certain role in inhibiting gas production and stabilizing the interface even in the absence of film-forming additives and acid neutralizers.

[0108] Comparative Example 1, without the addition of a lithium replenisher, exhibited the lowest volume growth rate at only 1.8% due to the absence of a lithium replenisher and oxygen release source. This was attributed to the minimal degree of electrolyte oxidation side reactions in the absence of a lithium replenisher and oxygen release source. Simultaneously, its capacity retention rate after 1000 cycles at 1C / 1C was 90.0%, reflecting the excellent structural stability and cycling performance of the lithium iron phosphate cathode material itself, and serving as a normal baseline performance for LFP. However, compared to Examples 1-5, Comparative Example 1 showed a capacity retention rate 1-6 percentage points lower, indicating that the inherent stability of LFP alone is insufficient to meet the demands of long-life applications.

[0109] Comparative Example 2, without the addition of fluorinated cyclic ethers and α,ω-dianitronic organic compounds, showed the worst performance, with a volume growth rate as high as 15.8% and a capacity retention rate of only 78.5%. This demonstrates that fluorinated cyclic ethers and α,ω-dianitronic organic compounds are the core components for inhibiting electrolyte oxidative decomposition and ensuring long cycle life.

[0110] Comparative Example 3, which replaced the fluorocyclic ether with adiponitrile, showed a volume growth rate of 12.0% and a capacity retention rate of 81.9%, indicating that the absence of the fluorocyclic ether resulted in the inability to effectively suppress oxygen release, and that adiponitrile could not replace the function of the fluorocyclic ether.

[0111] Comparative Example 4, which replaced adiponitrile with fluorocyclic ether, showed a volume growth rate of 10.0% and a capacity retention rate of 84.3%, demonstrating that the metal ion chelating effect of adiponitrile is indispensable and that fluorocyclic ether cannot completely replace the function of adiponitrile.

[0112] The comparative example 5 showed a large mass ratio of fluorocyclic ethers and α,ω-dianitronic organic compounds, resulting in a volume growth rate of 7.8% and a capacity retention rate of 86.5%. This indicates that excessive fluorocyclic ethers can lead to excessively high electrolyte viscosity, which is detrimental to cycle performance.

[0113] Comparative Example 6 shows that the relatively small mass of fluorocyclic ethers and α,ω-dianitronic organic compounds resulted in a volume growth rate of 13.2% and a capacity retention rate of 82.3%, demonstrating that insufficient fluorocyclic ether content cannot adequately cover the lithium supplement surface and thus has insufficient oxygen release inhibition effect.

[0114] Comparative Example 7, which replaced the tetrafluorocyclic ether with a monofluorocyclic ether, showed a volume increase of 15.6% and a capacity retention of 79.2%, demonstrating that monofluorocyclic ethers cannot form effective steric hindrance and surface coverage, and are essentially ineffective in inhibiting oxygen release from lithium supplementation agents. Only the polyfluorocyclic ethers with 4-6 fluorine atoms substituted in this invention can effectively inhibit the oxygen release behavior of lithium supplementation agents through the synergistic effect of steric hindrance and strong electronegativity generated by polyfluoro substitution.

[0115] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode comprises a positive current collector and a positive electrode material disposed on at least one surface of the positive current collector, the positive electrode material comprising a positive active material and a lithium replenishing agent, characterized in that, The electrolyte comprises lithium salt, organic solvent, fluorinated cyclic ether, and α,ω-dianitronic organic compound; the mass ratio of the fluorinated cyclic ether to the α,ω-dianitronic organic compound is (2.0-3.5):1; The fluorocyclic ether is a tetrahydrofuran containing 4-6 fluorine atoms substituted and / or a tetrahydropyran containing 4-6 fluorine atoms substituted.

2. The lithium-ion battery according to claim 1, characterized in that, The mass ratio of the fluorinated cyclic ether to the α,ω-dianitronic organic compound is (2.8-3.5):1; And / or, the tetrahydrofuran containing 4-6 fluorine atoms substituted includes at least one of 2,2,3,3-tetrafluorotetrahydrofuran, 2,2,3,3,4-pentafluorotetrahydrofuran, and 2,2,3,3,4,4-hexafluorotetrahydrofuran; preferably 2,2,3,3-tetrafluorotetrahydrofuran or 2,2,3,3,4-pentafluorotetrahydrofuran; And / or, the tetrahydropyran containing 4-6 fluorine atoms substituted includes at least one of 2,2,3,3,4,4-hexafluorotetrahydropyran, 2,2,3,3-tetrafluorotetrahydropyran, and 2,2,3,3,4-pentafluorotetrahydropyran; And / or, the α,ω-dianitrile organic compound includes at least one of adiponitrile and octanonitrile; preferably adiponitrile.

3. The lithium-ion battery according to claim 1, characterized in that, The lithium replenishing agent includes a first lithium replenishing agent and a second lithium replenishing agent, wherein the first lithium replenishing agent is Li5FeO4 and the second lithium replenishing agent is Li 2+x Ni 1-x O2; where 0≤x≤0.1, preferably 0≤x≤0.

05.

4. The lithium-ion battery according to claim 3, characterized in that, The mass ratio of the first lithium replenishing agent to the second lithium replenishing agent is R, where R is 1-5; And / or, in the cathode material, the total mass content of the first lithium supplement and the second lithium supplement is w. PR %, w PR 0.5wt%-5wt%; w PR The preferred concentration is 2.5wt%-5wt%.

5. The lithium-ion battery according to any one of claims 1-4, characterized in that, The mass content of the fluorocyclic ether is C. FE %, 12%-2%×(R / (1+R))×w PR ≤C FE %≤12%+2%×(R / (1+R))×w PR ; And / or, the mass content of the α,ω-dianitronic organic compound is C DN %, 3.5% + 0.25% × (w PR ×(1+0.6R) / (1+R))-0.5%≤C DN %≤3.5%+0.25%×(w PR ×(1+0.6R) / (1+R))+0.5%.

6. The lithium-ion battery according to claim 5, characterized in that, In the electrolyte, the content of the fluorocyclic ether is 10wt%-20wt%; preferably 11wt%-16wt%. And / or, the content of the α,ω-diacetonide organic compound is 3wt%-5wt%; preferably 4wt%-5wt%.

7. The lithium-ion battery according to claim 1, characterized in that, The lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorosulfonylimide, lithium perchlorate, lithium tetrafluoroborate, lithium dioxaborate, and lithium difluorooxaborate. And / or, the lithium salt content is 12wt%-16wt%, preferably 13wt%-15wt%; And / or, the organic solvent includes at least two of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene sulfite, and ethyl acetate; And / or, the electrolyte also includes additives; Optionally, the additives include fluorinated lithium salt film-forming additives and acid neutralizers; Optionally, the fluorinated lithium salt film-forming additive includes at least one of lithium difluorophosphate, lithium difluorooxalate borate, and lithium difluorobis(oxalate) phosphate; preferably lithium difluorophosphate. And / or, the acid neutralizing agent includes at least one of trimethylsilane phosphate, triethylsilane phosphate, and trimethylsilane phosphite; preferably trimethylsilane phosphate; And / or, the mass ratio of the fluorinated lithium salt film-forming additive to the acidic neutralizer is (0.4-1.2):1; preferably (1-1.2):1; And / or, the content of the fluorinated lithium salt film-forming additive is 0.1wt%-2wt%; preferably 1wt%-1.2wt%. And / or, the content of the acid neutralizing agent is 0.3wt%-2wt%; preferably 0.5wt%-1.5wt%.

8. The lithium-ion battery according to claim 1 or 3, characterized in that, The positive electrode material further includes a first conductive agent, a first binder, and a dispersant; Optionally, the first conductive agent includes at least one of conductive carbon black, acetylene black, Ketjen black, and carbon nanotubes; Optionally, the adhesive includes at least one of polyvinylidene fluoride and polyacrylic acid; Optionally, the dispersant includes at least one of polyacrylic acid, polyethylene glycol, carboxymethyl cellulose, and polyvinylpyrrolidone; Optionally, in the positive electrode material, the content of the first conductive agent is 0.2wt%-4wt%; Optionally, in the positive electrode material, the content of the first binder is 1wt%-2.5wt%; Optionally, the content of the dispersant in the positive electrode material is 0.1wt%-0.3wt%.

9. The lithium-ion battery according to claim 1, characterized in that, The negative electrode sheet includes a negative electrode current collector and a negative electrode material disposed on at least one side surface of the negative electrode current collector. The negative electrode material includes graphite, a second conductive agent, and a second binder. Optionally, the second conductive agent includes at least one of conductive carbon black and carbon nanotubes; Optionally, the second adhesive includes at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber, sodium alginate, and polyacrylic acid; Optionally, in the negative electrode material, the content of the second conductive agent is 0.5wt%-2wt%; Optionally, in the negative electrode material, the content of the second binder is 1.5wt%-4.5wt%.

10. The use of the lithium-ion battery according to any one of claims 1-9 in an electrical device.

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