Controllable polymerization gel electrolyte and preparation method thereof

Abstract

The application discloses a controllable polymerization gel electrolyte and a preparation method and application thereof. The controllable polymerization gel electrolyte is formed by in-situ polymerization of a controllable polymerization gel electrolyte precursor, and the controllable polymerization gel electrolyte precursor comprises the following components in parts by weight: a retarder 0.8-2.7 parts, a cationic polymerization monomer 5-27 parts, a lithium salt 15-35 parts and a lithium salt additive 4-8 parts; the retarder is a cyclic ether or a cyclic siloxane compound containing fluorine atoms in a substituent group. By adjusting the ratio of the retarder and the monomer, the controllability of the gel process can be realized, the electrolyte can keep liquid at room temperature to facilitate storage and infiltration, and a gel structure can be formed in-situ at a high-temperature aging stage after battery assembly. The controllable polymerization gel electrolyte is suitable for lithium ion batteries, and can significantly improve the safety, cycle stability and interface compatibility of the batteries.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to a controllable polymerizable gel electrolyte and its preparation method. Background Technology

[0002] Semi-solid-state batteries have become a recent research focus. Among the various polymerization methods for semi-solid gel electrolytes, photo / thermal initiation polymerization inevitably requires the addition of an initiator to promote the polymerization reaction, or additional light exposure and high-temperature curing processes, which are not fully compatible with existing battery manufacturing processes. Cationic polymerization, however, can utilize Lewis acids generated from the hydrolysis of lithium salts as initiators, allowing polymerization to occur at relatively lower temperatures, demonstrating unique application advantages. However, this also brings problems such as the electrolyte's tendency to self-polymerize, difficulty in room temperature storage, and premature gelation after electrolyte injection, resulting in insufficient wetting.

[0003] Cationic ring-opening polymerization of gel monomers can directly use Lewis acids from lithium salt dissociation as initiators, eliminating the need for additional initiators. Furthermore, polymerization can occur at relatively low temperatures, avoiding the need for additional high-temperature curing processes. This simplifies the application of controllable polymerization gel electrolytes, and the cell fabrication process can be largely consistent with traditional liquid electrolyte cells. However, this also presents a potential drawback: the easily polymerizable gel electrolyte undergoes self-polymerization at room temperature within a short time, making storage and transportation inconvenient and hindering the proper wetting of the cell after electrolyte injection. Summary of the Invention

[0004] In a first aspect, this application provides a controllable polymerizable gel electrolyte, which is formed by in-situ polymerization of a controllable polymerizable gel electrolyte precursor. The controllable polymerizable gel electrolyte precursor comprises the following components in parts by weight: 0.8 to 2.7 parts of a retarder, 5 to 27 parts of a cationic polymerizable monomer, 15 to 35 parts of a lithium salt, and 4 to 8 parts of a lithium salt additive.

[0005] The retarder is a cyclic ether compound or a cyclic siloxane compound containing fluorine atoms in its substituents;

[0006] The mass ratio of the retarder to the cationic monomer is 1:10 to 1:15.

[0007] In some embodiments, the weight parts of the retarder are specifically 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.8, 1.9, 2.0, 2.1, 2.4, 2.5 or 2.7 parts.

[0008] In some embodiments, the cationic polymeric monomer is specifically expressed in parts by weight as 5, 8, 10, 12, 15, 16.8, 18, 20, 22, 25, or 27.

[0009] In some embodiments, the lithium salt is specifically expressed in parts by weight as 15, 15.19, 18, 19, 20, 25, 28, 30, 32 or 35 parts.

[0010] In some embodiments, the lithium salt additive is specifically in parts by weight of 4, 4.16, 4.5, 5, 5.5, 6, 7 or 8 parts.

[0011] The controllable polymerization gel electrolyte formulation designed in this invention can slow down the self-polymerization process of the gel electrolyte at room temperature by precisely configuring the ratio of monomers to retarders, while still allowing normal gelation at higher temperatures, thus achieving controllable gelation process management and being fully compatible with existing liquid battery production processes.

[0012] In some embodiments, the retarder is selected from one or more of 3-(2,2,3,3-tetrafluoropropoxy)-1,2-propene oxide, 2-(trifluoromethyl)dioxane, 2,2-bis(trifluoromethyl)ethylene oxide, 1,3-bis(trifluoromethyl)cyclohexane, 3-(perfluorobutane)-1,2-propene oxide, and 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane.

[0013] The retarder used in this application is rich in fluorine and has a strong electron-withdrawing effect. This effect can increase the polymerization energy of the monomers and slow down the room-temperature polymerization rate. It also helps form a favorable fluoride-rich CEI / SEI film on the electrode surface, improving the high-voltage resistance of the controlled-polymerization gel electrolyte. Furthermore, the retarder itself participates in the cationic polymerization reaction and can form a cross-linked structure with the cationic monomers, enhancing the stability of the controlled-polymerization gel electrolyte. Therefore, the influence of initiator or retarder residues does not need to be considered.

[0014] In some embodiments, the cationic polymerizable monomer is selected from one or more of ethylene oxide, propylene oxide, epichlorohydrin, tetrahydrofuran, 2,3-dihydrofuran, 1,3-dioxane, 1,3-dioxane, 1,3-dioxane, 1,3-dioxane, 1,3,5-trioxane, maleic anhydride, succinic anhydride, glutaric anhydride, pentaerythritol glycidyl ether, trimethylolpropane triglycidyl ether, triglycidyl isocyanate, and trimethylolpropane-tris(3-acrylidinylpropionate).

[0015] The cationic ring-opening polymerization type of gel monomer selected in this application can directly use the Lewis acid of lithium salt dissociation as an initiator without the need to add an additional initiator. At the same time, polymerization can occur under relatively low temperature conditions, avoiding additional high-temperature curing processes. This makes the application of controllable polymerized gel electrolytes simpler, and the process flow for cell preparation can be basically consistent with that of traditional liquid cells.

[0016] In some embodiments, the lithium salt and the lithium salt additive are each independently selected from one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalate)borate, and lithium di(fluorooxalate)borate.

[0017] The formulation design of this application does not introduce any additional substances that could cause side reactions. The selected cationic polymerization pathway can use lithium salts as initiators, simplifying the process flow. Simultaneously, the lithium salts provide a lithium-ion source, ensuring the ionic conductivity of the electrolyte, and are compatible with retarders and cationic polymer monomers.

[0018] In some embodiments, the controllable polymerizable gel electrolyte precursor comprises the following components in parts by weight: 1.0 to 2.0 parts of retarder, 10 to 18 parts of cationic polymerizable monomer, 15.19 to 25 parts of lithium salt, and 4.16 to 6 parts of lithium salt additive;

[0019] The polymerization retarder is 3-(2,2,3,3-tetrafluoropropoxy)-1,2-propene oxide or 2-(trifluoromethyl)dioxolane;

[0020] The cationic polymer monomer is 1,3-dioxane;

[0021] The lithium salt is lithium hexafluorophosphate;

[0022] The lithium salt additive is lithium difluorooxalate borate; and

[0023] The mass ratio of the retarder to the cationic monomer is 1:10 to 1:15.

[0024] In some embodiments, the controllable polymerizable gel electrolyte precursor further includes an organic solvent;

[0025] The organic solvent is selected from one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, methyl formate, ethyl acetate, propyl propionate, and γ-butyrolactone.

[0026] Organic solvents, used as electrolyte bases, provide good solubility and flowability, ensuring uniform dispersion of lithium salts, retarders, and monomers, promoting full wetting of the electrolyte inside the battery cell, and laying the foundation for subsequent controlled polymerization.

[0027] A second aspect of this application provides the application of the controllable polymerizable gel electrolyte in the preparation of lithium-ion batteries.

[0028] When controllable polymerizable gel electrolytes are used in lithium-ion batteries, they improve battery safety through controllable polymerization, preventing electrolyte leakage or combustion at high temperatures; at the same time, they enhance cycle life and capacity retention, and are compatible with existing battery manufacturing processes.

[0029] A third aspect of this application provides a lithium-ion battery comprising the aforementioned controllable polymerizable gel electrolyte.

[0030] The lithium-ion battery uses the controllable polymerized gel electrolyte, which has low internal resistance, high coulombic efficiency and excellent cycle stability. At the same time, the gel structure enhances the mechanical strength of the battery, reduces the risk of short circuit, and improves the overall safety performance.

[0031] In some embodiments, the lithium-ion battery satisfies at least one of the following conditions (1) to (11);

[0032] (1) The lithium-ion battery further includes a positive electrode, a negative electrode, and a separator;

[0033] (2) The positive electrode sheet includes a current collector and a positive electrode material layer coated on the surface of the positive current collector;

[0034] (3) The positive electrode material layer includes a positive electrode active material, a conductive agent, and a binder;

[0035] (4) The negative electrode sheet includes a current collector and a negative electrode material layer coated on the surface of the negative electrode current collector;

[0036] (5) The negative electrode material layer includes a negative electrode active material, a conductive agent, and a binder;

[0037] (6) The positive electrode active material is selected from one or more of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide, lithium manganese iron phosphate, and lithium nickel cobalt aluminum oxide;

[0038] (7) The negative electrode active material is selected from one or more of graphite, lithium metal, lithium metal alloy, silicon-carbon materials, tin-based materials and silicon-oxygen materials;

[0039] (8) The conductive agent is selected from one or more of conductive carbon black, conductive graphite, carbon fiber and carbon nanotubes;

[0040] (9) The adhesive is selected from one or more of styrene-butadiene rubber, nitrile rubber, polyvinylidene fluoride and polytetrafluoroethylene;

[0041] (10) The mass ratio of the positive electrode active material, conductive agent and binder is (80-95):(2-10):(3-10);

[0042] (11) The mass ratio of the negative electrode active material: conductive agent: binder is (85-95): (1-6): (4-9).

[0043] The battery's specific structure is compatible with the controllable polymerized gel electrolyte, ensuring uniform gel distribution and good interfacial contact, further optimizing ion conduction pathways and electrode stability, and improving the battery's overall performance.

[0044] A fourth aspect of this application provides a method for preparing the lithium-ion battery, comprising the following steps:

[0045] S1. Dissolve lithium salt and lithium salt additives in an organic solvent to prepare an electrolyte base;

[0046] S2. Add the retarder and cationic monomer to the electrolyte substrate obtained in step S1, and mix evenly to obtain a gel precursor;

[0047] S3. The gel precursor obtained in step S2 is injected into the cell, left to stand, and then subjected to formation charging, aging treatment, sealing, and capacity testing to obtain a lithium-ion battery.

[0048] The method achieves controllable polymerization through step optimization: during the room temperature standing and formation stages, the electrolyte remains in a liquid state, ensuring sufficient wetting of the battery cell electrode and the formation of a uniform SEI film; in the subsequent aging stage, high-temperature triggered polymerization is used to achieve in-situ gelation, which solves the problem of poor contact between the controllable polymerized gel electrolyte and the electrode, and does not require additional high-temperature or light curing equipment, making the process simple and efficient.

[0049] In some implementations, the method satisfies at least one of the following conditions (12) to (16):

[0050] (12) The concentration of lithium salt in step S1 is 1.0 mol / L ~ 2.0 mol / L, specifically 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0 mol / L; the concentration of lithium salt additive is 0.2 mol / L ~ 0.55 mol / L, specifically 0.2, 0.3, 0.4, 0.5 or 0.55 mol / L;

[0051] (13) The temperature for standing in step S3 is 20~30℃, specifically 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30℃; the standing time is 12~120h, specifically 12, 24, 36, 48, 60, 72, 96 or 120h;

[0052] (14) The formation charging process in step S3 is to charge at a constant current of 0.02 C to 3.4V, at a constant current of 0.1 C to 3.6V, and at a constant current of 0.2 C to 3.8V in sequence;

[0053] (15) The aging treatment temperature in step S3 is 45℃-60℃ and the aging treatment time is 48h-72h;

[0054] (16) The process of capacity division in step S3 is to charge at a constant current and constant voltage of 0.33 C to 4.25 V, cut off current of 0.05 C, discharge at a constant current of 0.33 C to 2.5 V, and repeat 5 times.

[0055] By precisely controlling the concentration, temperature, and time parameters, optimal control of the polymerization kinetics was achieved. A specific lithium salt concentration balances conductivity and initiation efficiency; specific resting / aging temperatures and time windows precisely match the activation threshold of the slow polymerization system, ensuring that gelation does not occur before wetting is complete, and that the system can rapidly and completely transform into a gel during aging, thereby obtaining a battery product with the lowest internal resistance and the best overall performance. Detailed Implementation

[0056] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] For the sake of brevity, this document only discloses a few specific numerical ranges for a given parameter. However, any lower limit can be combined with any upper limit to form an unspecified range, and any lower limit can be combined with other lower limits to form an unspecified range; similarly, any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit, combined with any other point or single value, or with other lower or upper limits, to form an unspecified range. It should be understood that this disclosure is not limited to the specific methods, schemes, and reagents described herein, and is itself subject to variation. The terminology used herein is for the purpose of describing specific embodiments or aspects only and is not intended to limit the scope of this disclosure.

[0058] Unless otherwise stated, the terms used in this application have their common meanings as commonly understood by those skilled in the art. Unless otherwise stated, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application). Unless otherwise expressly stated, all reagents used in this application are commonly used reagents for chemical analysis or experiments and are derived from conventional commercial suppliers in the art.

[0059] The list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0060] In this article, "retarder" refers to an additive that slows down the polymerization reaction rate and is used in controlled polymerization gel electrolytes to delay the gelation process at room temperature so that polymerization occurs only when needed (e.g., at high temperatures).

[0061] In this article, "flowing gel" refers to the initial state of gelation, which has a certain fluidity and viscosity, has not yet fully solidified, and can still flow slowly.

[0062] In this paper, "complete gel" refers to a high degree of gelation, which has lost its fluidity and formed a stable solid or semi-solid structure, but still retains a certain degree of elasticity.

[0063] In this article, "hard gel" refers to a gel structure that has been further solidified, resulting in a harder texture and higher strength, usually formed by high cross-linking or long-term aging.

[0064] In this paper, "diffuse gel" refers to gelation that is uneven, may be dispersed or locally gelled, has a loose structure, and fails to form a continuous, dense gel network.

[0065] In this article, "first-cycle coulombic efficiency" refers to the percentage of discharge capacity to charge capacity of a battery during its first charge-discharge cycle.

[0066] In this article, "200-cycle capacity retention" refers to the percentage of the battery's remaining discharge capacity relative to its initial discharge capacity after 200 charge-discharge cycles.

[0067] Experimental reagents

[0068] Lithium hexafluorophosphate was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., item number L697849; lithium difluorooxalate borate was purchased from Aladdin Reagent (Shanghai) Co., Ltd., item number L303675; ethylene carbonate was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., item number E707993; dimethyl carbonate was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., item number D822978; 3-(2,2,3,3-tetrafluoropropoxy)-1,2-propene oxide was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., item number G857607; 1,3-dioxopentane was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., item number D806906; nickel-cobalt-manganese ternary materials were purchased from Shenzhen Kejing Zhida Technology Co., Ltd., item number MS-LNCM811-183; polyvinylidene fluoride was purchased from Solvay (Shanghai) Co., Ltd., item number PVDF5130; carbon black was purchased from Shenzhen Kejing Zhida Technology Co., Ltd., item number Super P; Silicon-carbon material (Si:C=1:9) was purchased from Shenzhen Kejing Zhida Technology Co., Ltd., item number SL450B-SC; Styrene-butadiene rubber was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., item number P886285; Carbon nanotubes were purchased from Shanghai Maclean Biochemical Technology Co., Ltd., item number C915132; The diaphragm was purchased from Shenzhen Kejing Zhida Technology Co., Ltd., item number 2325; 1,1,1-trifluoro-2,3-epoxypropane was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., item number E809385.

[0069] The following exemplarily illustrates the various steps in preparing the controllable polymerizable gel electrolyte of the present invention:

[0070] Example 1: This example describes the preparation of a controllable polymerizable gel electrolyte, and the process is as follows:

[0071] Step 1: Dissolve 15.19 g of lithium hexafluorophosphate (LiPF6) and 4.16 g of lithium difluorooxalate borate (LiDFOB) in 100 mL of a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) (volume ratio 1:1), and stir until the lithium salt and lithium salt additive are completely dissolved to obtain an electrolyte base with a lithium salt (LiPF6) concentration of 1 mol / L and a lithium salt additive (LiDFOB) concentration of 0.2 mol / L.

[0072] Step 2: Add 1.4 g of 3-(2,2,3,3-tetrafluoropropoxy)-1,2-propene oxide retarder and 16.8 g of 1,3-dioxane cationic monomer to the electrolyte base and continue stirring to mix evenly to obtain a controllable polymerization gel electrolyte precursor solution containing the retarder.

[0073] Step 3: The controllable polymerized gel electrolyte precursor solution was injected into the dry cell using the conventional liquid electrolyte preparation process. The cell was then subjected to vacuum sealing, room temperature standing (48h), formation charging, 45℃ high-temperature aging (48h), and capacity testing to prepare a pouch battery. The positive electrode of the pouch battery was prepared by mixing nickel-cobalt-manganese ternary materials, polyvinylidene fluoride binder, and carbon black conductive agent in a mass ratio of 95:2:3. The negative electrode was prepared by mixing silicon-carbon materials, styrene-butadiene rubber binder, and carbon nanotube conductive agent in a mass ratio of 95:4:1. The positive and negative electrodes and the separator were then assembled into a pouch battery using a stacking process. To fully observe the conversion process of the controllable polymerized gel electrolyte inside the cell, the pouch battery used for disassembly and analysis was subjected to different standing times at room temperature (25℃) and 45℃, as detailed in Table 1. The pouch cells used for performance testing were uniformly subjected to a process of being left to stand at room temperature for 48 hours and then aged at 45°C for 48 hours. The formation and charging process involved constant current charging at 0.02 C to 3.4 V, constant current charging at 0.1 C to 3.6 V, and constant current charging at 0.2 C to 3.8 V. The capacity grading process involved constant current and constant voltage charging at 0.33 C to 4.25 V, with a cutoff current of 0.05 C, followed by constant current discharge at 0.33 C to 2.5 V, repeated 5 times.

[0074] Example 2: This example is the preparation of a controllable polymerizable gel electrolyte. Compared with Example 1, the difference is that 0.7 g of 3-(2,2,3,3-tetrafluoropropoxy)-1,2-propene oxide retarder was added in step 2. Other substances, amounts and parameters are the same as in Example 1.

[0075] Example 3: This example is the preparation of a controllable polymerizable gel electrolyte. Compared with Example 1, the difference is that 2.8 g of 3-(2,2,3,3-tetrafluoropropoxy)-1,2-propene oxide retarder was added in step 2. All other substances, amounts and parameters are the same as in Example 1.

[0076] Example 4: This example is for the preparation of a controllable polymerizable gel electrolyte. The difference from Example 1 is that 5.6 g of 3-(2,2,3,3-tetrafluoropropoxy)-1,2-propene oxide retarder was added in step 2. All other substances, amounts and parameters are the same as in Example 1.

[0077] Example 5: This example is for the preparation of a controllable polymerizable gel electrolyte. Compared with Example 1, the difference is that 1.4 g of 1,1,1-trifluoro-2,3-epoxypropane retarder was added in step 2. All other substances, amounts and parameters are the same as in Example 1.

[0078] Example 6: This example is the preparation of a controllable polymerizable gel electrolyte. Compared with Example 1, the difference is that 28 g of 1,3-dioxopentane cationic polymer monomer was added in step 2. Other substances, amounts and parameters are the same as in Example 1.

[0079] Example 7: This example is the preparation of a controllable polymerizable gel electrolyte. Compared with Example 1, the difference is that 8.32 g of lithium difluorooxalate borate was added in step 1. Other substances, amounts and parameters are the same as in Example 1.

[0080] Example 8: This example is the preparation of a controllable polymerizable gel electrolyte. Compared with Example 1, the difference is that 1.8 g of 3-(2,2,3,3-tetrafluoropropoxy)-1,2-propene oxide retarder and 18 g of 1,3-dioxopentane cationic monomer were added in step 2. Other substances, amounts and parameters are the same as in Example 1.

[0081] Example 9: This example is the preparation of a controllable polymerizable gel electrolyte. Compared with Example 1, the difference is that 1.0 g of 3-(2,2,3,3-tetrafluoropropoxy)-1,2-propylene oxide retarder and 10 g of 1,3-dioxopentane cationic monomer were added in step 2. All other substances, amounts and parameters are the same as in Example 1.

[0082] Example 10: This example is for the preparation of a controllable polymerizable gel electrolyte. Compared with Example 1, the difference is that 1.0 g of 2-(trifluoromethyl)dioxolane retarder and 12 g of 1,3-dioxolane cationic monomer were added in step 2. Other substances, amounts and parameters are the same as in Example 1.

[0083] Comparative Example 1: This comparative example is the preparation of a controllable polymerizable gel electrolyte without a retarder. The difference from Example 1 is that no retarder was added in step 2. All other substances, amounts and parameters are the same as in Example 1.

[0084] Comparative Example 2: This comparative example is the preparation of a controllable polymerizable gel electrolyte without a retarder. Compared with Example 1, the difference is that no retarder was added in step 2, and the amount of 1,3-dioxopentane cationic monomer added was 11.2 g. Other substances, amounts and parameters were the same as in Example 1.

[0085] Comparative Example 3: This comparative example is the preparation of a controllable polymerizable gel electrolyte without a retarder. Compared with Example 1, the difference is that no retarder was added in step 2, and the amount of 1,3-dioxopentane cationic monomer added was 28 g. Other substances, amounts and parameters were the same as in Example 1.

[0086] Test Example 1

[0087] First, the pouch cells at different stages of the manufacturing process were disassembled and analyzed. The electrolyte state of each implementation / comparative cell was recorded at different times through visual observation, and the results are shown in Table 1.

[0088] Table 1 shows the electrolyte state of the batteries in each embodiment and comparative example at different times.

[0089]

[0090] The purpose of allowing the electrolyte to fully penetrate the pores of the electrode, ensuring complete wetting of the battery cell, and forming a more uniform SEI (solid electrolyte interface) layer during the subsequent formation stage. Completely gelled electrolytes have reduced fluidity and cannot fully wet the battery cell. Therefore, ideally, the controllable polymerized gel electrolyte should remain liquid during room temperature standing and formation stages to ensure normal electrical performance, while forming a gel during the high-temperature aging stage to protect the battery cell and improve safety. Observations of the polymerization within the cells of Comparative Examples 1, 2, and 3 (without retarders) show that high-proportion cationic monomers have a rapid polymerization rate at room temperature, completing gelation within 48 hours of room temperature standing. Comparative Example 2, by reducing the monomer dosage to avoid excessively rapid polymerization at room temperature, allowed the electrolyte to remain in a viscous state for a longer period at room temperature, but it failed to form a gel during the subsequent aging stage at 45°C. While reducing the monomer ratio lowered the reaction rate, it also reduced the molecular weight of the polymerized product. Therefore, after reaching a certain threshold, it tended to form low-molecular-weight oligomers rather than high-molecular-weight polymers. In other words, simply reducing the monomer dosage could not achieve the desired controlled gel polymerization effect. After introducing a retarder, the gel polymerization rate in all examples at room temperature was slowed down. Example 1 ensured that the electrolyte remained in a liquid state after standing at room temperature for 5 days. Example 2, with a lower retarder dosage, showed a significant increase in electrolyte viscosity after 72 hours of standing at room temperature, and still began to gel after 5 days of standing at room temperature. Examples 3 and 4, compared to Example 1, used a higher retarder dosage. Although the retardation effect was more significant at room temperature, effective complete gelation could not be achieved under 45°C heating conditions. Example 5 changed the type of retarder. Under the same addition ratio, the retardation effect of 1,1,1-trifluoro-2,3-epoxypropane was not as good as that of 3-(2,2,3,3-tetrafluoropropoxy)-1,2-propene oxide. This may be related to the fact that the latter has more fluorine atoms and a higher ring-opening polymerization energy. Examples 6 and 7 increased the monomer concentration and the lithium salt additive concentration, respectively, and their gelation process was accelerated, but the retarder's room-temperature retardation effect was still visible.

[0091] Test Example 2

[0092] 1. Testing method:

[0093] (1) Ionic conductivity: The test adopts the AC impedance method. The electrolyte solution in all the above examples or comparative examples is placed in a lithium-lithium symmetrical coin cell. After assembly, it undergoes a polymerization reaction to form a controllable polymerized gel electrolyte. The ionic conductivity value is calculated by testing the total impedance contributed by the electrolyte in the battery and combining it with the size of the controllable polymerized gel electrolyte being tested.

[0094] (2) Battery internal resistance test: After 200 cycles, the battery impedance is tested using an internal resistance meter. The internal resistance growth rate is the ratio of the difference before and after the cycle to the battery internal resistance before the cycle.

[0095] (3) First-cycle coulomb efficiency test: The first-cycle coulomb efficiency is obtained by calculating the ratio of the discharge capacity to the charging capacity after the initial capacity is determined.

[0096] (4) Cyclic performance test: 200 cycles of constant current and constant voltage charge and discharge test at room temperature with a voltage range of 2.5-4.25 V. The capacity retention rate is obtained by calculating the ratio of discharge capacity before and after the cycle.

[0097] Electrical performance tests were conducted on the above embodiments and comparative examples, and the test results are shown in Table 2.

[0098] Table 2. Electrical performance test results of batteries in each embodiment and comparative example.

[0099]

[0100] The test results show a correlation between battery internal resistance and battery gelation. Groups with faster gelation tend to exhibit higher internal resistance, which is related to premature monomer polymerization, insufficient electrolyte wetting of the electrodes, and the inherently lower ion conductivity of the gel state compared to the liquid state. Compared to the comparative examples with the same monomer concentration, all examples showed significantly higher cycle capacity retention. The retarder not only regulates the degree of gelation but also works with the cationic monomers to form a cross-linked structure, which is beneficial for improving the structural stability and high-voltage resistance of the electrolyte, resulting in a significant improvement in cycle life. However, more retarders are not always better. Excessive retarder dosage (Example 4) may lead to a decrease in gelation degree and excessive cross-linking density, resulting in increased brittleness and decreased ionic conductivity, thus reducing capacity retention. When the cationic monomer dosage is too high (Example 6 and Comparative Example 3), residual unreacted monomers become a potential problem, and the overall lithium salt concentration is effectively diluted, further reducing ionic conductivity and causing a rapid decline in electrical performance. Therefore, it is necessary to achieve precise formulation design and controlled polymerization of controllable polymerizable gel electrolytes.

[0101] The embodiments described in this application are merely illustrative examples. The embodiments of this application are not limited to the above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of this application shall be considered equivalent substitutions and shall be included within the protection scope of this application.

Claims

1. A controllable polymerizable gel electrolyte, characterized in that, The controllable polymerizable gel electrolyte is formed by in-situ polymerization of a controllable polymerizable gel electrolyte precursor. The controllable polymerizable gel electrolyte precursor comprises the following components in parts by weight: 0.8-2.7 parts of retarder, 5-27 parts of cationic polymerizable monomer, 15-35 parts of lithium salt, and 4-8 parts of lithium salt additive. The polymerization retarder is selected from one or more of 2-(trifluoromethyl)dioxolane, 2,2-bis(trifluoromethyl)ethylene oxide, 1,3-bis(trifluoromethyl)cyclohexane, 3-(perfluorobutane)-1,2-propane oxide, and 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane; The cationic polymer monomer is 1,3-dioxane; The mass ratio of the retarder to the cationic monomer is 1:10 to 1:

15.

2. The controllable polymerizable gel electrolyte as described in claim 1, characterized in that, The lithium salt and lithium salt additive are each independently selected from one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalate)borate, and lithium di(fluorooxalate)borate.

3. The controllable polymerizable gel electrolyte as described in claim 1, characterized in that, The controllable polymerizable gel electrolyte precursor comprises the following components in parts by weight: 1.0-2.0 parts of retarder, 10-18 parts of cationic polymerizable monomer, 15.19-25 parts of lithium salt, and 4.16-6 parts of lithium salt additive; The lithium salt is lithium hexafluorophosphate; The lithium salt additive is lithium difluorooxalate borate.

4. The controllable polymerizable gel electrolyte as described in claim 1, characterized in that, The controllable polymerizable gel electrolyte precursor also includes an organic solvent; The organic solvent is selected from one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, methyl formate, ethyl acetate, propyl propionate, and γ-butyrolactone.

5. A lithium-ion battery, characterized in that, Includes the controllable polymerizable gel electrolyte as described in any one of claims 1-4.

6. The lithium-ion battery as described in claim 5, characterized in that, The lithium-ion battery satisfies at least one of the following conditions (1) to (11); (1) The lithium-ion battery further includes a positive electrode, a negative electrode, and a separator; (2) The positive electrode sheet includes a current collector and a positive electrode material layer coated on the surface of the positive current collector; (3) The positive electrode material layer includes a positive electrode active material, a conductive agent, and a binder; (4) The negative electrode sheet includes a current collector and a negative electrode material layer coated on the surface of the negative electrode current collector; (5) The negative electrode material layer includes a negative electrode active material, a conductive agent, and a binder; (6) The positive electrode active material is selected from one or more of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide, lithium manganese iron phosphate, and lithium nickel cobalt aluminum oxide; (7) The negative electrode active material is selected from one or more of graphite, lithium metal, lithium metal alloy, silicon-carbon materials, tin-based materials and silicon-oxygen materials; (8) The conductive agent is selected from one or more of conductive carbon black, conductive graphite, carbon fiber and carbon nanotubes; (9) The adhesive is selected from one or more of styrene-butadiene rubber, nitrile rubber, polyvinylidene fluoride and polytetrafluoroethylene; (10) The mass ratio of the positive electrode active material, conductive agent, and binder is (80-95):(2-10):(3-10); or (11) The mass ratio of the negative electrode active material: conductive agent: binder is (85-95): (1-6): (4-9).

7. A method for preparing a lithium-ion battery as described in claim 5 or 6, characterized in that, Includes the following steps: S1. Dissolve lithium salt and lithium salt additives in an organic solvent to prepare an electrolyte base; S2. Add the retarder and cationic polymerizing monomer to the electrolyte substrate obtained in step S1, and mix evenly to obtain a gel precursor; S3. The gel precursor obtained in step S2 is injected into the battery cell, left to stand, and then subjected to formation charging, aging treatment, sealing, and capacity testing to obtain a lithium-ion battery.

8. The method as described in claim 7, characterized in that, The method satisfies at least one of the following conditions (12) to (16): (12) In step S1, the concentration of lithium salt is 1.0 mol / L to 2.0 mol / L, and the concentration of lithium salt additive is 0.2 mol / L to 0.55 mol / L; (13) The temperature for standing in step S3 is 20~30℃ and the standing time is 12~120h; (14) The formation charging process in step S3 is to charge at a constant current of 0.02 C to 3.4V, at a constant current of 0.1C to 3.6V, and at a constant current of 0.2C to 3.8V in sequence; (15) The aging treatment temperature in step S3 is 45℃-60℃ and the aging treatment time is 48h-72h; (16) The process of capacity division in step S3 is to charge to 4.25V with constant current and constant voltage at 0.33C, cut off current at 0.05C, discharge to 2.5V with constant current at 0.33C, and repeat 5 times.

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