Gel electrolyte, preparation method thereof and battery

Abstract

The invention discloses a gel electrolyte, a preparation method thereof and a battery. The gel electrolyte provided by the invention is obtained by polymerizing and curing a prepolymer electrolyte; the prepolymer electrolyte comprises a prepolymer solution and a liquid electrolyte; the prepolymer solution comprises an acrylate monomer, a cross-linking agent and an initiator; the liquid electrolyte comprises an additive, and the additive comprises at least one of the following three components: # imgabs0. In the gel electrolyte, through the combined action of the acrylate polymer gel electrolyte and the sulfonate additive, the expansion of the battery and the rapid and continuous increase of the DCR value in high-temperature storage are inhibited, so that the high-temperature electrochemical performance of the battery is improved; and meanwhile, relatively high normal-temperature cycle performance is realized.

Description

Technical Field

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

[0002] High energy density, long life, and high safety are the prerequisite conditions for the commercial application of lithium-ion batteries in the field of electric vehicles. The development and application of ternary lithium-ion power batteries are restricted by technical problems such as capacity attenuation under high-temperature conditions and gas production and bulging of the battery.

[0003] The gel electrolyte combines the cohesion of a solid and the diffusion and transmission properties of a liquid, has good electrochemical stability, and solves the problem of electrolyte leakage in traditional liquid batteries by encapsulating the liquid electrolyte in a polymer network, increasing safety. As the matrix of the gel electrolyte, polyacrylate exhibits good room-temperature cycle stability, but its electrochemical performance under high-temperature conditions needs to be further improved. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems in the related art to some extent. To this end, an object of the present invention is to provide a gel electrolyte, a preparation method thereof, and a battery. In this gel electrolyte, through the combined action of an acrylate polymer gel electrolyte and a sulfonate additive, the battery swelling and the rapid and continuous increase of the DCR value during high-temperature storage are inhibited, thereby improving the high-temperature electrochemical performance of the battery and having relatively high room-temperature cycle performance at the same time.

[0005] In one aspect of the present application, a gel electrolyte is provided. According to an embodiment of the present application, the gel electrolyte is obtained by polymerizing and curing a prepolymer electrolyte; the prepolymer electrolyte includes a prepolymer solution and a liquid electrolyte; the prepolymer solution includes acrylate monomers, a cross-linking agent, and an initiator; the liquid electrolyte includes an additive, and the additive includes at least one of the following three:

[0006]

[0007] In this application, the sulfonate additive contains an aromatic ring, which is more likely to be reduced and form a stable electrode-electrolyte interface film component. In addition, this interface film also has greater flexibility, enabling stable lithium-ion insertion and extraction and inhibiting the dissolution of metal ions from the cathode material. This mechanism can be explained as follows: during the charging process of the prepolymer electrolyte added with sulfonate additives in the battery formation stage, the sulfonate additives are attacked by electrons, the sulfonate bonds of the sulfonate additives are broken to generate free radicals, which cooperate with the initiator to initiate the polymerization of monomers in the prepolymer electrolyte. Finally, the sulfonate group and aryl group of the sulfonate additives are introduced into the polymer backbone, increasing the flexibility and ionic conductivity of the gel electrolyte polymer backbone. At the electrode interface, it is preferentially reduced to form an interface film composed of an inorganic layer and an organic polymer layer connecting aromatic rings with polyoxyalkyl chains (PEO-like structure). The high content of oxygen atoms ensures high lithium-ion conductivity and low impedance, while the structure introducing aromatic rings ensures the flexibility of the interface film, supporting the long-term stable lithium-ion insertion and extraction of the electrodes in this battery system and the ability to inhibit the increase of DCR at high temperatures. Through the optimization of the structure and properties of the polymer backbone and the interface film, excellent cycle stability and interface stability under high-temperature conditions are finally presented, achieving a high capacity retention rate during high-temperature storage.

[0008] In this application, an acrylate polymer gel electrolyte with high conductivity and certain mechanical strength is used in combination with sulfonate additives. On the one hand, by utilizing the high conductivity of the gel itself and its mechanical properties that can relieve the volume strain of the silicon-carbon negative electrode, the sulfonate group and aryl group of the sulfonate additives are introduced into the polymer backbone, enhancing the flexibility of the gel electrolyte polymer backbone and its lithium-ion transport ability, and achieving the stability of long-term cycling. On the other hand, the sulfonate additives are used to regulate the electrode-electrolyte interface to construct a low-impedance and flexible SEI film, preventing the electrode from being crushed and collapsed due to severe volume expansion during long-term cycling and high-temperature conditions, continuously exposing new active interfaces and undergoing continuous decomposition, thereby achieving the inhibition of DCR growth and improving the capacity retention rate during high-temperature storage.

[0009] According to the embodiments of this application, the above gel electrolyte may further include at least one of the following additional technical features:

[0010] In some embodiments, by mass percentage, the prepolymer electrolyte includes: 5% - 35% of the prepolymer solution, 65% - 95% of the liquid electrolyte; the amount of the additive accounts for 0.1% - 3% of the mass of the liquid electrolyte.

[0011] In some embodiments, at least one of the following (1) - (3) is satisfied:

[0012] (1) The acrylate monomers include: conforming to the structural general formula CH 2 =C(R'1)C(O)OCn H 2n+1 At least one of the acrylate compounds shown, wherein R'1 is H or CH 3 , n = 1 to 8;

[0013] (2) The crosslinking agent includes: carboxylate esters having a double bond structure;

[0014] (3) The initiator includes: azo initiators.

[0015] In some embodiments, the acrylate monomer is selected from at least one of ethyl acrylate, propyl acrylate, ethyl methacrylate, and propyl methacrylate.

[0016] In some embodiments, the liquid electrolyte further includes a lithium salt and an organic solvent.

[0017] In a second aspect of the present application, a method for preparing a gel electrolyte is proposed, including:

[0018] Preparing a gel electrolyte by polymerizing and curing a prepolymer electrolyte solution; the prepolymer solution includes an acrylate monomer, a crosslinking agent, and an initiator; the liquid electrolyte includes an additive; the additive includes at least one of the following three:

[0019]

[0020] The preparation method provided by the present application can in-situ prepare a gel electrolyte. By using an acrylate polymer gel electrolyte with high conductivity and certain mechanical strength in combination with a sulfonate additive, on the one hand, by utilizing the high conductivity of the gel itself and the mechanical properties that can relieve the volume strain of the silicon-carbon negative electrode, the sulfonate group and aryl group of the sulfonate additive are introduced into the polymer backbone, enhancing the flexibility of the gel electrolyte polymer backbone and the lithium ion transport ability, and realizing the stability of long-term cycling; on the other hand, by using the sulfonate additive to regulate the electrode-electrolyte interface to construct a low-impedance and flexible SEI film, preventing the electrode from being crushed and collapsed due to severe volume expansion during long-term cycling and high-temperature conditions, continuously exposing new active interfaces and undergoing continuous decomposition, thereby realizing the inhibition of DCR growth and improving the capacity retention rate during high-temperature storage.

[0021] In some embodiments, the raw materials satisfy at least one of the following (1) to (3):

[0022] (1) The acrylate monomer includes: conforming to the structural general formula CH 2 =C(R'1)C(O)OC n H 2n+1 At least one of the acrylate compounds shown, wherein R'1 is H or CH 3 , n = 1 to 8;

[0023] (2) The crosslinking agent includes: carboxylic acid esters having a double bond structure;

[0024] (3) The initiator includes: azo initiators.

[0025] In some embodiments, the acrylate monomers are selected from at least one of ethyl acrylate, propyl acrylate, ethyl methacrylate, and propyl methacrylate.

[0026] In some embodiments, the raw materials satisfy at least one of the following (1) to (4):

[0027] (1) The mass ratio of the acrylate monomers to the crosslinking agent is (97.5 - 60):(2.5 - 40), and the sum of the former term and the latter term is 100;

[0028] (2) The dosage of the initiator is 0.01% - 0.05% of the total mass of the acrylate monomers and the crosslinking agent;

[0029] (3) The mass ratio of the prepolymer solution to the liquid electrolyte is (5 - 35):(95 - 65), and the sum of the former term and the latter term is 100;

[0030] (4) The amount of the additive accounts for 0.1% - 3% of the mass of the liquid electrolyte.

[0031] In three aspects of the present application, the present application provides a battery, which includes the above-mentioned gel electrolyte, or includes the gel electrolyte obtained by the above-mentioned preparation method.

[0032] The battery provided by the present application contains the above-mentioned electrolyte. Through the combined action of the acrylate polymer gel electrolyte and the sulfonate additive, it can inhibit the swelling of the battery and the rapid and continuous increase of the DCR value during high-temperature storage, and can improve its normal-temperature cycling performance and high-temperature storage performance.

[0033] The additional aspects and advantages of the present invention will be partially given in the following description, partially will become obvious from the following description, or will be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, wherein:

[0035] Figure 1 is the preparation flow chart of the gel electrolyte in some embodiments of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The embodiments of the present invention will be described in detail below, which are intended to explain the present invention and should not be construed as limiting the present invention.

[0037] Traditional liquid carbonate electrolytes are prone to oxidative decomposition under high-temperature conditions, resulting in intense side reactions between the electrolyte components and the electrodes, which significantly deteriorates the electrochemical performance of the battery and even causes safety problems. Gel electrolytes combine the cohesion of solids and the diffusion and transport properties of liquids, and have good electrochemical stability. By encapsulating liquid electrolytes (including lithium salts and solvents) in a polymer network, the problem of electrolyte leakage in traditional liquid batteries is solved, greatly increasing safety. Acrylate compounds have a high lithium salt solubility, enabling the gel electrolyte to have a high conductivity. Moreover, the gel electrolyte has a certain mechanical strength and can relieve the volume strain caused by the lithium insertion and extraction processes at the negative electrode during long-term cycling, improving its room-temperature cycling stability. However, during high-temperature storage, the impedance at the electrode interface increases significantly, affecting the electrochemical performance of the gel system under high-temperature conditions.

[0038] In one aspect of the embodiments of the present application, a gel electrolyte is proposed. The gel electrolyte is obtained by polymerizing and curing a prepolymer electrolyte; the prepolymer electrolyte includes a prepolymer solution and a liquid electrolyte; the prepolymer solution includes acrylate monomers, a cross-linking agent, and an initiator; the liquid electrolyte includes additives, and the additives include at least one of the following three:

[0039]

[0040] To solve the problem of the growth of the gel electrolyte DCR (Direct Current Resistance) under high-temperature conditions, in the embodiments of the present application, at least one of the above three sulfonate additives is used in combination with an acrylate polymer gel electrolyte in a battery system. The sulfonate additives have an obvious inhibitory effect on the growth of its high-temperature DCR, enabling good room-temperature cycling stability while improving the high-temperature electrochemical performance of the system, specifically manifested as inhibiting the swelling of the battery and the rapid and continuous increase in the DCR value during high-temperature storage.

[0041] In the embodiments of the present application, during the charging process in the battery formation stage, the prepolymer electrolyte added with sulfonate additives is attacked by electrons. The sulfonate additives break their bonds to generate free radicals, which cooperate with the initiator to initiate the polymerization of monomers in the prepolymer electrolyte. Eventually, the sulfonate groups and aryl groups of the sulfonate additives are introduced into the polymer backbone, increasing the flexibility and ionic conductivity of the gel electrolyte polymer backbone. At the electrode interface, an interfacial film composed of an inorganic layer preferentially formed by reduction and an organic polymer layer connecting aromatic rings by polyoxyalkyl chains (PEO-like structure) is formed. The high content of oxygen atoms ensures high lithium-ion conductivity and low impedance, while the introduction of the aromatic ring structure ensures the flexibility of the interfacial film, supporting the long-term stable insertion and extraction of lithium ions by the electrodes in this battery system and the ability to inhibit the increase in DCR at high temperatures. By optimizing the structures and properties of the polymer backbone and the interfacial film, excellent cycle stability and interfacial stability under high-temperature conditions are finally presented, achieving a high capacity retention rate during high-temperature storage.

[0042] In the embodiments of the present application, an acrylate polymer gel electrolyte with high conductivity and certain mechanical strength is used in combination with sulfonate additives. On the one hand, by utilizing the high conductivity of the gel itself and its mechanical properties that can relieve the volume strain of the silicon-carbon negative electrode, the sulfonate groups and aryl groups of the sulfonate additives are introduced into the polymer backbone, enhancing the flexibility of the gel electrolyte polymer backbone and its ability to transport lithium ions, and achieving the stability of long-term cycling. On the other hand, the sulfonate additives are used to regulate the electrode-electrolyte interface to construct a SEI film with low impedance and rich flexibility, preventing the electrode from being crushed and collapsed due to severe volume expansion during long-term cycling and high-temperature conditions, continuously exposing new active interfaces and undergoing continuous decomposition, thereby achieving the inhibition of DCR growth and improving the capacity retention rate during high-temperature storage.

[0043] In some specific embodiments of the present application, the additives include:

[0044]

[0045] Compared with the additives shown in Formula I-1 and Formula I-2, the oxygen sites are relatively more after the partial bond cleavage of the sulfonate group in the additive shown in Formula I-3, and the effect of improving the ionic conductivity of the polymer backbone and the interfacial film is more significant. Therefore, its improvement of the electrochemical performance is more obvious.

[0046] In some specific embodiments of the present application, by mass percentage, the prepolymer electrolyte includes: 5% - 35% of the prepolymer solution, 65% - 95% of the liquid electrolyte; the amount of the additive accounts for 0.1% - 3% of the mass of the liquid electrolyte.

[0047] In the embodiments of the present application, the gel electrolyte and the liquid electrolyte meet the above conditions, which is beneficial to improving the cycle performance and high-temperature storage performance of the battery. In a specific example, the composition of the prepolymer electrolyte is 5% prepolymer solution + 95% liquid electrolyte, or 10% prepolymer solution + 90% liquid electrolyte, 15% prepolymer solution + 85% liquid electrolyte, 20% prepolymer solution + 80% liquid electrolyte, 25% prepolymer solution + 75% liquid electrolyte, 30% prepolymer solution + 70% liquid electrolyte, 35% prepolymer solution + 65% liquid electrolyte, etc.

[0048] In the embodiments of the present application, the dosage of the additive meets the above conditions, which is beneficial to the full play of the additive's effect, inhibits the expansion of the battery and the rapid and continuous increase of the DCR value during high-temperature storage. Adding an appropriate amount of the additive can further regulate the growth of the flexible and uniform electrode and electrolyte interface film, reduce interface side reactions and active material realization, etc., and improve the long-term cycle stability of the battery under high-temperature working conditions and maintain a relatively high cycle reversible capacity. In a specific example, the amount of the additive is 0.1%, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc. of the mass of the liquid electrolyte.

[0049] In some specific embodiments of the present application, at least one of the following (1) to (3) is satisfied:

[0050] (1) The acrylate monomers include: at least one of the acrylate compounds conforming to the structural general formula CH 2 =C(R'1)C(O)OC n H 2n+1 shown, where R'1 is H or CH 3 , and n = 1 to 8;

[0051] (2) The crosslinking agent includes: carboxylic acid esters having a double bond structure;

[0052] (3) The initiator includes: azo initiators.

[0053] In the embodiments of the present application, the structural general formula is CH 2 =C(R'1)C(O)OC n H 2n+1The acrylate compound shown, as an acrylate monomer, has a high lithium salt dissolution ability, enabling the gel electrolyte to have a high conductivity. Moreover, the gel electrolyte has a certain mechanical strength and can play a role in alleviating the volume strain caused by the lithium insertion and extraction processes at the negative electrode during long-term cycling, thereby enhancing its room-temperature cycling stability. The drawback is that during high-temperature storage, the impedance at the electrode interface increases significantly, which will affect the electrochemical performance of the gel system under high-temperature conditions. In the embodiments of the present application, by adding a specific sulfonate additive, the prepolymer electrolyte added with the sulfonate additive is attacked by electrons during the charging process in the battery formation stage. The sulfonate additive breaks the bond to generate free radicals, which cooperate with the initiator to initiate the polymerization of the monomers in the prepolymer electrolyte. Finally, the sulfonate group and aryl group of the sulfonate additive are introduced into the polymer backbone, increasing the flexibility and ionic conductivity of the gel electrolyte polymer backbone. In addition, the sulfonate additive is beneficial for inhibiting the rapid and continuous increase in battery swelling and DCR value during high-temperature storage. The two work together to simultaneously obtain good low-temperature cycling performance and high-temperature electrochemical performance.

[0054] In the embodiments of the present application, the cross-linking agent includes a carboxylic acid ester having a double-bond structure, which is beneficial for cross-linking polymer segments to form a network structure, thereby enabling the liquid electrolyte to be filled in the grid to form a gel electrolyte. Further, the carboxylic acid ester having a double-bond structure includes at least one of polyethylene glycol dimethacrylate (PEGDMA), polyethylene glycol diacrylate, and polyethylene glycol methacrylate.

[0055] Furthermore, the carboxylic acid ester having a double-bond structure is polyethylene glycol dimethacrylate (PEGDMA). Its symmetric methyl structure can make the electron clouds on adjacent carbon-carbon double bonds unevenly distributed, making it more likely to react to form a multi-point cross-linked network polymer structure.

[0056] In the embodiments of the present application, the initiator includes: an azo initiator, that is, a free radical initiator containing a nitrogen-nitrogen double bond in its molecular structure. Further, the azo initiator includes at least one of azobisisobutyronitrile (AIBN) and azobisisoheptonitrile (ABVN).

[0057] In some specific embodiments of the present application, the acrylate monomer includes: an acrylate compound conforming to the structural general formula CH 2 =C(R'1)C(O)OC n H 2n+1 shown, where R'1 is H or CH 3 , and n = 2 or 3.

[0058] In the embodiments of the present application, acrylate monomers are polymerized under the action of a free radical initiator, and the chain segments grow. Further, through the cross-linking action of a cross-linking agent, the chain segments are interconnected to form a network structure, and at the same time, a liquid electrolyte is filled in the grid to form a gel electrolyte. For the general structural formula of acrylate compounds CH 2 =C(R'1)C(O)OC n H 2n+1 , when n = 2 or 3, the length of the free chain segments between the polymer grids is appropriate, which is conducive to improving the lithium ion transport efficiency, and the steric hindrance is small. The formed network structure is conducive to accommodating more liquid electrolyte, which is conducive to reducing the internal resistance and providing an effective buffering effect on volume changes, thereby improving the cycle performance and high-temperature storage performance of the battery.

[0059] In some specific embodiments of the present application, the acrylate monomer is selected from at least one of ethyl acrylate, propyl acrylate, ethyl methacrylate, and propyl methacrylate.

[0060] In the embodiments of the present application, the polymer formed by the polymerization of the above acrylate monomers is shown as a cross-linked network structure with short side chains. The cross-linking interval has relatively small steric hindrance, can accommodate more liquid electrolyte, and can ensure the lithium ion transport effect. While ensuring a high ion transport ability, it also provides an effective buffering effect on the volume change at the electrode material end, thereby improving the cycle performance and high-temperature storage performance of the battery.

[0061] In some specific embodiments of the present application, the liquid electrolyte further includes a lithium salt and an organic solvent.

[0062] In the embodiments of the present application, the lithium salt can adopt lithium salt materials known in the art for batteries. Further, the lithium salt includes LiPF 6 , LiFSI, etc.

[0063] In the embodiments of the present application, the organic solvent can adopt organic solvents known in the art for batteries. Further, the organic solvent includes carbonate solvents, and the carbonate solvents include ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), etc.

[0064] In another aspect of the embodiments of the present application, the present application proposes a preparation method of a gel electrolyte, including:

[0065] Preparing a gel electrolyte by polymerizing and curing a prepolymer electrolyte solution; the prepolymer solution includes acrylate monomers, a cross-linking agent, and an initiator; the liquid electrolyte includes additives; the additives include at least one of the following three:

[0066]

[0067] The preparation method provided by the embodiments of the present application can in-situ prepare a gel electrolyte. By using an acrylate polymer gel electrolyte with high conductivity and certain mechanical strength in combination with a sulfonate additive, on the one hand, taking advantage of the high conductivity of the gel itself and the mechanical properties that can relieve the volume strain of the silicon-carbon negative electrode, the sulfonate group and aryl group of the sulfonate additive are introduced into the polymer backbone, enhancing the flexibility of the gel electrolyte polymer backbone and the ability to transport lithium ions, and realizing the stability of long-term cycling; on the other hand, using the sulfonate additive to regulate the electrode-electrolyte interface to construct a low-impedance and flexible SEI film, preventing the electrode from being crushed and collapsed due to severe volume expansion during long-term cycling and high-temperature conditions, continuously exposing new active interfaces and undergoing continuous decomposition, thereby realizing the inhibition of DCR growth and improving the capacity retention rate during high-temperature storage.

[0068] In some specific embodiments of the present application, at least one of the following (1) to (3) is satisfied:

[0069] (1) The acrylate monomers include: acrylate compounds conforming to the structural general formula CH 2 =C(R'1)C(O)OC n H 2n+1 shown, where R'1 is H or CH 3 , and n = 1 to 8;

[0070] (2) The cross-linking agent includes: carboxylate esters with double bond structures;

[0071] (3) The initiator includes: azo initiators.

[0072] In the embodiments of the present application, the structural general formula is CH 2 =C(R'1)C(O)OC n H 2n+1The acrylate compound shown is used as an acrylate monomer. The acrylate compound has a high lithium salt solubility, which can endow the gel electrolyte with a high conductivity. Moreover, the gel electrolyte has a certain mechanical strength and can play a role in alleviating the volume strain caused by the lithium insertion and extraction processes at the negative electrode during long-term cycling, thereby enhancing its room-temperature cycling stability. The drawback is that during high-temperature storage, the impedance at the electrode interface increases significantly, which will affect the electrochemical performance of the gel system under high-temperature conditions. In the embodiments of the present application, by adding a specific sulfonate additive, the sulfonate group and aryl group of the sulfonate additive are introduced into the polymer backbone, enhancing the flexibility of the gel electrolyte polymer backbone and the ability to transport lithium ions. In addition, the sulfonate additive is beneficial for inhibiting battery swelling and the rapid and continuous increase of the DCR value during high-temperature storage. The two work together to simultaneously obtain good low-temperature cycling performance and high-temperature electrochemical performance.

[0073] In the embodiments of the present application, the cross-linking agent includes a carboxylic acid ester having a double-bond structure, which is conducive to cross-linking polymer segments to form a network structure, thereby enabling the liquid electrolyte to be filled in the grid to form a gel electrolyte. Further, the carboxylic acid ester having a double-bond structure includes at least one of polyethylene glycol dimethacrylate (PEGDMA), polyethylene glycol diacrylate, and polyethylene glycol methacrylate.

[0074] Furthermore, the carboxylic acid ester having a double-bond structure is polyethylene glycol dimethacrylate (PEGDMA). Its symmetric methyl structure can cause the electron clouds on adjacent carbon-carbon double bonds to be unevenly distributed, making it more likely to react and form a multi-point cross-linked network polymer structure.

[0075] In the embodiments of the present application, the initiator includes an azo initiator, that is, a radical initiator containing a nitrogen-nitrogen double bond in its molecular structure. Further, the azo initiator includes at least one of azobisisobutyronitrile (AIBN) and azobisisoheptonitrile (ABVN).

[0076] In some specific embodiments of the present application, the acrylate monomer includes: conforming to the structural general formula CH 2 =C(R'1)C(O)OC n H 2n+1 The acrylate compound shown, wherein, R'1 is H or CH 3 , n = 2 or 3.

[0077] In the embodiments of the present application, the acrylate monomer polymerizes under the action of a radical initiator, the chain segments grow, and further through the cross-linking action of the cross-linking agent, the chain segments are interconnected to form a network structure. At the same time, the liquid electrolyte is filled in the grid to form a gel electrolyte. For the structural general formula CH of the acrylate compound 2=C(R'1)C(O)OC n H 2n+1 When n = 2 or 3, the length of the free chain segments between the polymer networks is appropriate, which is conducive to improving the lithium ion transport efficiency. Moreover, the steric hindrance is small, and the formed network structure is conducive to accommodating more liquid electrolyte, which is conducive to reducing the internal resistance and providing an effective buffering effect on the volume change, thereby improving the cycle performance and high temperature storage performance of the battery.

[0078] In some specific embodiments of the present application, the acrylate monomer is selected from at least one of ethyl acrylate, propyl acrylate, ethyl methacrylate and propyl methacrylate.

[0079] In the embodiments of the present application, the polymer formed by polymerizing the above acrylate monomers is shown as a cross-linked network structure with short side chains. The cross-linking interval has relatively small steric hindrance, can accommodate more liquid electrolyte, and can ensure the lithium ion transport effect. While ensuring a high ion transport capacity, it also provides an effective buffering effect on the volume change at the electrode material end, thereby improving the cycle performance and high temperature storage performance of the battery.

[0080] In some specific embodiments of the present application, the raw materials satisfy at least one of the following (1) to (4):

[0081] (1) The mass ratio of the acrylate monomer to the cross-linking agent is (97.5 - 60):(2.5 - 40), and the sum of the former term and the latter term is 100; further, the mass ratio of the acrylate monomer to the cross-linking agent is (97.5 - 90):(2.5 - 10);

[0082] (2) The dosage of the initiator is 0.01% - 0.05% of the total mass of the acrylate monomer and the cross-linking agent; further, the dosage of the initiator is 0.02% - 0.03% of the total mass of the acrylate monomer and the cross-linking agent;

[0083] (3) The mass ratio of the prepolymer solution to the liquid electrolyte is (5 - 35):(95 - 65), and the sum of the former term and the latter term is 100; further, the mass ratio of the prepolymer solution to the liquid electrolyte is (5 - 20):(95 - 80);

[0084] (4) The amount of the additive accounts for 0.1% - 3% of the mass of the liquid electrolyte.

[0085] In the embodiments of the present application, when the mass ratio of the acrylate monomer to the crosslinking agent meets the above conditions, it is beneficial to improve the cohesion of the acrylate polymer and the diffusion and transmission of the liquid, and has good electrochemical stability. By wrapping the liquid electrolyte in the polymer network and utilizing the high conductivity of the gel itself and the mechanical properties that can relieve the volume strain of the silicon-carbon negative electrode, the stability of long-term cycling is achieved. In specific examples, the mass ratio of the acrylate monomer to the crosslinking agent is 97.5:2.5, 97:3, 96.5:3.5, 96:4, 95.5:4.5, 95:5, 94.5:5.5, 94:6, 93.5:6.5, 93:7, 92.5:7.5, 92:8, 91.5:8.5, 91:9, 90.5:9.5, 90:10, 85:15, 80:20, 75:25, 70:30, 65:35, 60:40, etc.

[0086] In the embodiments of the present application, when the dosage of the initiator meets the above requirements, it is beneficial to reasonably control the polymerization reaction rate and obtain an acrylate polymer with high conductivity and good mechanical properties. In specific examples, the dosage of the initiator is 0.01%, 0.02%, 0.025%, 0.03%, 0.04%, 0.05%, etc. of the total mass of the acrylate monomer and the crosslinking agent.

[0087] In the embodiments of the present application, when the mass ratio of the prepolymer solution to the liquid electrolyte meets the above requirements, while ensuring the overall mechanical strength and conductivity, a high ionic conductivity can be obtained, which is further beneficial to suppressing the swelling of the battery and the rapid and continuous increase of the DCR value during high-temperature storage. In specific examples, the mass ratio of the prepolymer solution to the liquid electrolyte is 5:95, 8:92, 10:90, 12:88, 15:85, 20:80, 25:75, 30:70, 35:65, etc. Among them, in the prepolymer solution, since the addition amount of the initiator is small, the addition amount of the initiator can be ignored during the preparation process. Therefore, the mass ratio of the prepolymer solution to the liquid electrolyte can actually refer to the ratio of the total mass of the "acrylate monomer and the crosslinking agent" to the mass of the liquid electrolyte.

[0088] In the embodiments of the present application, when the dosage of the additive meets the above conditions, it is beneficial for the additive to fully exert its effect and suppress the rapid and continuous increase of the battery swelling and the DCR value during high-temperature storage. Adding an appropriate amount of the additive can further regulate the growth of the electrode and electrolyte interface film with flexibility and uniformity, reduce interface side reactions and active substance loss, etc., and improve the long-term cycling stability of the battery under high-temperature working conditions and maintain a high cycle reversible capacity. In specific examples, the amount of the additive is 0.1%, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc. of the mass of the liquid electrolyte.

[0089] In some specific embodiments of the present application, the step of mixing raw materials including acrylate monomers, crosslinking agents, initiators, additives, lithium salts, and organic solvents includes:

[0090] Mix acrylate monomers, crosslinking agents, and initiators to prepare a prepolymer solution;

[0091] Mix additives, lithium salts, and organic solvents to prepare a liquid electrolyte;

[0092] Mix the prepolymer solution and the liquid electrolyte.

[0093] In the embodiments of the present application, by separately preparing the prepolymer solution and the liquid electrolyte and then mixing the prepolymer solution and the liquid electrolyte, it is beneficial to improve the mixing effect. The preparation order of the solutions is not limited. The prepolymer solution can be prepared first, or the liquid electrolyte can be prepared first.

[0094] In some embodiments, the mixed solution of the prepolymer solution and the liquid electrolyte is thermally initiated, and a gel electrolyte is obtained through a polymerization reaction and curing.

[0095] In some embodiments, the mixed solution of the prepolymer solution and the liquid electrolyte is injected into the battery. After the battery formation, a gel electrolyte is formed by in-situ polymerization through thermal initiation.

[0096] In some specific embodiments of the present application, in the gel electrolyte obtained through reaction preparation, the controlled parameters include:

[0097] The reaction temperature is: 35°C to 80°C, and further, the reaction temperature is 50°C to 70°C; and / or, the reaction time is 1 h to 36 h, and further, the reaction time is 10 h to 15 h.

[0098] In specific examples, the reaction temperature is 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C, etc.

[0099] In specific examples, the reaction time is 1 h, 5 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 20 h, 25 h, 30 h, or 36 h, etc.

[0100] In some specific embodiments of the present application, as Figure 1 shown, the preparation method of the gel electrolyte includes the steps:

[0101] S1000: Prepare a prepolymer solution. Mix acrylate monomers, crosslinking agents, and initiators to obtain a prepolymer solution.

[0102] S2000: Prepare a liquid electrolyte. Mix additives, lithium salts, and organic solvents to obtain a liquid electrolyte.

[0103] S3000: Prepare a gel electrolyte precursor solution. Mix the prepolymer solution and the liquid electrolyte to obtain the gel electrolyte precursor solution.

[0104] S4000: Polymerization reaction. Subject the coagulated gel electrolyte precursor solution to a thermal initiation for a polymerization reaction to prepare the gel electrolyte.

[0105] In three aspects of the embodiments of the present application, the present application provides a battery, which includes the above-mentioned gel electrolyte, or includes the gel electrolyte obtained by the above-mentioned preparation method.

[0106] The battery provided by the embodiments of the present application contains the above-mentioned electrolyte. Through the combined action of the acrylate polymer gel electrolyte and the sulfonate additive, it can inhibit the expansion of the battery and the rapid and continuous increase of the DCR value during high-temperature storage, and can improve its normal-temperature cycling performance and high-temperature storage performance.

[0107] In some specific embodiments of the present application, the battery further includes a negative electrode plate, which includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

[0108] In some specific embodiments of the present application, the battery further includes a positive electrode plate, which includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material.

[0109] In some specific embodiments of the present application, the positive electrode active material can be a positive electrode active material known in the art for batteries. As an example, the positive electrode active material includes ternary medium-high nickel or high nickel active materials, lithium iron phosphate, lithium manganese iron phosphate materials, etc.; further, the ternary medium-high nickel or high nickel active materials include LiNi 0.6 Co 0.2 Mn 0.2 O 2 、LiNi 0.6 Co 0.1 Mn 0.3 O 2 、LiNi 0.5 Co 0.2 Mn 0.3 O 2、 LiNi 0.8 Co 0.1 Mn 0.1 O 2 、LiNi 0.85 Co 0.1 Al 0.05 O 2 etc.

[0110] In some specific embodiments of the present application, the negative electrode active material may adopt conventional negative electrode active materials in the art. As an example, the negative electrode active material includes a silicon-carbon composite.

[0111] Further, the silicon-carbon composite includes carbon nanotube-doped silicon, graphene sheet-coated silicon, porous carbon shell-coated silicon-based materials, etc.

[0112] The gel electrolyte provided by the embodiments of the present application can effectively alleviate the performance problems caused by the sudden increase in the impedance at the positive electrode interface and the large volume strain of the negative electrode during high-temperature conditions in the battery system.

[0113] The present invention will be described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way. The reagents used in the embodiments are all from Aladdin Biochemical Technology Co., Ltd.

[0114] Example 1

[0115] (1) Preparation of the prepolymer electrolyte

[0116] First, the acrylate monomer (ethyl acrylate) and the cross-linking agent (polyethylene glycol dimethacrylate) are pretreated by heating and baking at high temperature and then passing through a molecular sieve after cooling for water treatment. The water treatment time should be greater than 5 days. Weigh 90 g of ethyl acrylate and 10 g of polyethylene glycol dimethacrylate into a clean aluminum bottle and mix them. Finally, add 0.25 g of the initiator (azobisisobutyronitrile) and mix to obtain the prepolymer solution;

[0117] Weigh 125 g of LiPF 6 into a clean aluminum bottle, sequentially add 262.5 g of EC (ethylene carbonate) and 612.5 g of EMC (ethyl methyl carbonate), shake until completely dissolved, and finally add 1 g of Additive I (Additive I-1), and mix evenly to obtain the liquid electrolyte;

[0118] Weigh 100 g of the prepolymer solution and 900 g of the liquid electrolyte and mix them to obtain the prepolymer electrolyte.

[0119] (2) Preparation of the positive electrode sheet: Disperse the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 , the conductive agent super P, and the binder PVDF (polyvinylidene fluoride) in a mass ratio of 92.5:5:2.5 in the NMP (N-methylpyrrolidone) solvent, stir and mix well to form a uniform positive electrode paste (the solid content in the positive electrode paste is 60 wt%), uniformly coat the positive electrode paste on the positive electrode current collector aluminum foil, and obtain the positive electrode sheet after drying, rolling, and slitting.

[0120] (3) Preparation of the negative electrode sheet: The negative active material SiC550, conductive agents super P and SWCNT (single-walled carbon nanotube), binder CMC (carboxymethyl cellulose), and SBR (styrene-butadiene rubber) were dispersed in deionized water according to a mass ratio of 87.94:6:0.06:2:4, and were sufficiently stirred and mixed to form a uniform negative electrode slurry (the solid content in the negative electrode slurry was 49 wt%). The negative electrode slurry was uniformly coated on the negative electrode current collector copper foil, and after drying, rolling, and slitting, the negative electrode sheet was obtained.

[0121] (4) Preparation of the battery: The above-mentioned positive electrode sheet, separator, and the above-mentioned negative electrode sheet were stacked in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, and then wound to obtain a bare battery cell. The bare battery cell was placed in an outer packaging case, and after drying, the prepolymer electrolyte prepared in step (1) was injected. After the procedures of primary encapsulation, formation, and hot pressing and curing, the preparation of the battery was completed.

[0122] Example 2 - 23

[0123] The method provided in Example 2 - 23 is the same as that in Example 1, with the differences recorded in Table 1 and Table 2. In Table 1:

[0124] The additive of Formula I - 1 is:

[0125]

[0126] The additive of Formula I - 2 is:

[0127]

[0128] The additive of Formula I - 3 is:

[0129]

[0130] “NMC811” represents LiNi 0.8 Mn 0.1 Co 0.1 O 2 ; “NMC622” represents LiNi 0.6 Mn 0.2 Co 0.2 O 2 .

[0131] Comparative Example 1

[0132] The preparation method of the battery provided in Comparative Example 1 is the same as that in Example 1, except that no additive was added.

[0133] Comparative Example 2

[0134] The specific preparation method of the battery is as follows:

[0135] (1) Prepare a liquid electrolyte solution containing the additive of Formula I

[0136] Weigh 125 g of LiPF 6 Into a clean aluminum bottle, sequentially add 262.5 g of EC (ethylene carbonate) and 612.5 g of EMC (ethyl methyl carbonate), and shake until completely dissolved. Finally, add 1 g of the additive of Formula I-1. After mixing evenly, the liquid electrolyte is prepared;

[0137] Take 900 g of the liquid electrolyte into a sample bottle, and the target electrolyte solution is prepared.

[0138] (2) Preparation of the positive electrode sheet: Disperse the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 , conductive agent super P, and binder PVDF in a mass ratio of 92:5:5:2.5 in NMP solvent, stir and mix well to form a uniform positive electrode paste (the solid content in the positive electrode paste is 60 wt%). Coat the positive electrode paste evenly on the positive electrode current collector aluminum foil, and after drying, rolling, and slitting, the positive electrode sheet is obtained.

[0139] (3) Preparation of the negative electrode sheet: Disperse the negative electrode active material SiC550, conductive agent super P, and SWCNT, binder CMC, and SBR in a mass ratio of 87.94:6:0.06:2:4 in deionized water, stir and mix well to form a uniform negative electrode paste (the solid content in the negative electrode paste is 49 wt%). Coat the negative electrode paste evenly on the negative electrode current collector copper foil, and after drying, rolling, and slitting, the negative electrode sheet is obtained.

[0140] (4) Preparation of the battery: Stack the above positive electrode sheet, separator, and the above negative electrode sheet in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, then wind to obtain a bare battery core, place the bare battery core in an outer packaging shell, after drying, inject 900 g of the target electrolyte solution prepared in step (1). After a primary encapsulation process, the preparation of the battery is completed.

[0141] Comparative Example 3

[0142] The specific preparation method of the battery is as follows:

[0143] (1) Prepare a liquid electrolyte solution containing the PS additive

[0144] Weigh 125 g of LiPF 6Into a clean aluminum bottle, 262.5 g of EC (ethylene carbonate) and 612.5 g of EMC (ethyl methyl carbonate) were added in sequence, and shaken until completely dissolved. Finally, 1 g of PS (1,3 - propane sultone) additive was added. After mixing evenly, a liquid electrolyte was prepared.

[0145] 900 g of the liquid electrolyte was taken into a sample bottle to prepare the target electrolyte solution.

[0146] (2) Preparation of the positive electrode sheet: The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 , conductive agent super P, and binder PVDF were dispersed in NMP solvent according to the mass ratio of 92:5:5:2.5, and stirred thoroughly to form a uniform positive electrode paste (the solid content in the positive electrode paste was 60 wt%). The positive electrode paste was evenly coated on the positive electrode current collector aluminum foil, and after drying, rolling, and slitting, the positive electrode sheet was obtained.

[0147] (3) Preparation of the negative electrode sheet: The negative electrode active material SiC550, conductive agent super P, and SWCNT, binder CMC, and SBR were dispersed in deionized water according to the mass ratio of 87.94:6:0.06:2:4, and stirred thoroughly to form a uniform negative electrode paste (the solid content in the negative electrode paste was 49 wt%). The negative electrode paste was evenly coated on the negative electrode current collector copper foil, and after drying, rolling, and slitting, the negative electrode sheet was obtained.

[0148] (4) Preparation of the battery: The above - mentioned positive electrode sheet, separator, and negative electrode sheet were stacked in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role. Then, it was wound to obtain a bare battery core, and the bare battery core was placed in an outer packaging shell. After drying, 900 g of the target electrolyte solution prepared in step (1) was injected. After a primary packaging process, the preparation of the battery was completed.

[0149] The parameter settings in the preparation methods provided in Examples 2 - 23 and Comparative Examples 1 - 3 are shown in Table 1.

[0150] Table 1

[0151]

[0152] Performance testing

[0153] I. Testing method.

[0154] The batteries in the examples and comparative examples were respectively subjected to the following performance tests:

[0155] (1) DCR (Direct Current Resistance) Test: After the formation process is completed, charge the battery at 1C to 4.2V with a cut-off current of 0.05C, let it stand for 120 min, discharge it at 2C to 10s with a sampling interval of 0.1s, record the data, and mark it as the initial DCR. After high-temperature storage, conduct a capacity recovery test on the battery. After 5 cycles of 1C / 1C, charge the battery at 1C to 4.2V with a cut-off current of 0.05C, let it stand for 120 min, discharge it at 2C to 10s with a sampling interval of 0.1s, record the data, and mark it as the DCR' after storage. Record the change in the DCR value of the battery before and after high-temperature storage.

[0156] (2) 25°C 0.5C / 0.5C Cycle Test:

[0157] Charge the battery at a constant current of 0.5C to 4.2V at 25°C, charge it at a constant voltage of 4.2V until the cut-off current is 0.05C, and then discharge the battery at a constant current of 0.5C. Record the discharge capacity as C 0 , repeat the charge and discharge process until the capacity decays to 80% of C 0 , and record the number of cycles.

[0158] (3) 45°C 0.5C / 0.5C Cycle Test:

[0159] Charge the battery at a constant current of 0.5C to 4.2V at 45°C, charge it at a constant voltage until the cut-off current is 0.05C, and then discharge the battery at a constant current of 0.5C. Record the discharge capacity as C 1 , repeat the charge and discharge process until the capacity decays to 80% of C 1 , and record the number of cycles.

[0160] (4) 60°C Storage for 30 Days Test:

[0161] Charge the battery at a constant current of 0.1C to 4.2V at 25°C, charge it at a constant voltage of 4.2V until the cut-off current is 0.05C, and then discharge the battery at a constant current of 0.5C. Record the discharge capacity as C 2 . Remove the battery and measure its initial thickness as T using a thickness tester 1 . At 25°C, charge the battery at a constant current of 0.1C to 4.2V, charge it at a constant voltage of 4.2V until the cut-off current is 0.05C, and then transfer the battery to 60°C and let it stand for 30 days. Measure its thickness after 30 days of standing as T 2 . Then discharge the battery at a constant current of 0.1C. Record the discharge capacity as C 3 , the capacity retention rate after 60°C storage for 30 days = C 3 / C 2 *100%, the battery expansion rate = 100%*(T 2 - T 1 ) / T1 。

[0162] II. Performance Test Results

[0163] The performance test results are shown in Table 2

[0164] Table 2

[0165]

[0166] By combining the data of the implementation examples and the comparative examples, the conclusion can be drawn that the combination of acrylate polymer gel electrolyte and sulfonate additive can combine the advantages of both, construct a SEI film with low impedance and rich flexibility, prevent the silicon-based negative electrode from being crushed and collapsed due to severe volume expansion under long-term cycling and high-temperature conditions, continuously expose new active interfaces for continuous decomposition, and then achieve the effect of inhibiting the growth of DCR, improve the capacity retention rate during high-temperature storage, and achieve the stability of long-term cycling.

[0167] In the description of this specification, the descriptions with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection 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 are not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0168] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A gel electrolyte, characterized in that: The prepolymer electrolyte is obtained by polymerization and curing; the prepolymer electrolyte comprises a prepolymer solution and a liquid electrolyte; The prepolymer solution includes an acrylate monomer, a crosslinking agent and an initiator; The liquid electrolyte includes an additive, and the additive includes at least one of the following three:

2. The gel electrolyte according to claim 1, characterized in that Calculated by mass percentage, the prepolymer electrolyte comprises: 5% to 35% of the prepolymer solution and 65% to 95% of the liquid electrolyte; the amount of the additive accounts for 0.1% to 3% of the mass of the liquid electrolyte.

3. The gel electrolyte according to claim 1 or 2, characterized in that: Satisfy at least one of the following (1) to (3): (1) The acrylic ester monomers include: n H 2n+1 At least one of the acrylic acid ester compounds shown, wherein R'1 is H or CH3, and n=1 to 8; (2) The cross-linking agent includes: a carboxylate having a double bond structure; (3) The initiator includes: an azo initiator.

4. The gel electrolyte according to any one of claims 1 to 3, characterized in that: The acrylic acid ester monomer is selected from at least one of ethyl acrylate, propyl acrylate, ethyl methacrylate and propyl methacrylate.

5. The gel electrolyte according to any one of claims 1 to 4, characterized in that: The liquid electrolyte further includes a lithium salt and an organic solvent.

6. A method for preparing a gel electrolyte, characterized in that: include: The prepolymer electrolyte is polymerized and solidified to prepare a gel electrolyte; the prepolymer solution includes an acrylate monomer, a crosslinking agent and an initiator; the liquid electrolyte includes an additive, and the additive includes at least one of the following three:

7. The method for preparing the gel electrolyte according to claim 6, characterized in that: Satisfy at least one of the following (1) to (3): (1) The acrylic ester monomers include: n H 2n+1 At least one of the acrylic acid ester compounds shown, wherein R'1 is H or CH3, and n=1 to 8; (2) The cross-linking agent includes: a carboxylate having a double bond structure; (3) The initiator includes: an azo initiator.

8. The method for preparing a gel electrolyte according to claim 6 or 7, characterized in that: The acrylic acid ester monomer is selected from at least one of ethyl acrylate, propyl acrylate, ethyl methacrylate and propyl methacrylate.

9. The method for preparing a gel electrolyte according to any one of claims 6 to 8, characterized in that: Satisfy at least one of the following (1) to (4): (1) The mass ratio of the acrylic acid ester monomer to the crosslinking agent is (97.5-60):(2.5-40), and the sum of the former and the latter is 100; (2) The amount of the initiator is 0.01% to 0.05% of the total mass of the acrylic ester monomer and the crosslinking agent; (3) The mass ratio of the prepolymer solution to the liquid electrolyte is (5-35):(95-65), and the sum of the former and the latter is 100; (4) The amount of the additive accounts for 0.1% to 3% of the mass of the liquid electrolyte.

10. A battery, characterized in that: The invention comprises the gel electrolyte according to any one of claims 1 to 5, or the gel electrolyte obtained by the preparation method according to any one of claims 6 to 9.

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