In-situ cured electrolyte, preparation method therefor and lithium ion battery

Abstract

An in-situ cured electrolyte, a preparation method therefor and a lithium ion battery. The raw material components comprise an initiator and an electrolyte, and the raw material components further comprise a polymer monomer and a phosphate ester flame retardant. The polymer monomer is subjected to a chemical reaction by means of the initiator, so as to form a high-molecular polymer with a cross-linked network structure. The phosphate ester flame retardant is dissolved in the electrolyte and then becomes uniformly transparent. Under the synergistic effect of the polymer monomer and the phosphate ester flame retardant, the technical problem of high safety hazards of existing lithium ion batteries is solved.

Description

In-situ solidified electrolyte and preparation method thereof, and lithium ion battery

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202311196975.1 filed on September 18, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the technical field of lithium-ion batteries, and in particular to an in-situ solidified electrolyte and a preparation method thereof, and a lithium-ion battery. Background Art

[0004] Since its commercialization in the 1990s, lithium-ion batteries have become a leader in the fields of energy storage, 3C consumer electronics, and power batteries due to their high output voltage, high energy density, low pollution, and no memory effect.

[0005] However, as consumers' requirements for battery energy density and safety continue to increase, the safety issues of lithium-ion batteries are difficult to meet user needs.

[0006] Summary of the Invention

[0007] The present application provides an in-situ solidified electrolyte and a preparation method thereof, and a lithium-ion battery, to solve the technical problem of high safety hazards of existing lithium-ion batteries.

[0008] In a first aspect, the present application provides an in-situ solidified electrolyte, the raw material components of which include an initiator and an electrolyte, and the raw material components further include: a polymer monomer and a phosphate flame retardant; wherein,

[0009] The polymer monomers undergo a chemical reaction with the initiator to form a high molecular polymer having a cross-linked network structure;

[0010] The phosphate flame retardant is dissolved in the electrolyte and then becomes uniform and transparent.

[0011] An optional optimization technical solution is that the phosphate flame retardant includes at least one of the following: triethyl phosphate, triphenyl phosphate, and tributyl phosphate.

[0012] An optional optimization technical solution is that the polymer monomer includes at least one of the following: a monomer containing an unsaturated bond, and a cyclic monomer.

[0013] An optional optimization technical solution is that the monomer containing an unsaturated bond includes at least one of the following: vinylene carbonate and succinonitrile.

[0014] In an optional optimization technical solution, the cyclic monomer includes at least one of the following: dioxolane and 1,4-butyrolactone.

[0015] An optional optimization technical solution is that the volume ratio of the polymer monomer to the phosphate flame retardant is (1-5):(1-3).

[0016] An optional optimization technical solution, wherein the volume ratio is 1:1.

[0017] In a second aspect, the present application provides a method for preparing an in-situ solidified electrolyte, for preparing the in-situ solidified electrolyte according to any embodiment of the first aspect, the method comprising:

[0018] Mixing polymer monomers, initiators, electrolytes, and phosphate flame retardants to obtain a precursor solution;

[0019] The precursor solution is heated and solidified in stages to obtain an in-situ solidified electrolyte.

[0020] An optional optimization technical solution, wherein the precursor solution is heated and solidified in stages to obtain an in-situ solidified electrolyte, comprises:

[0021] The precursor solution is heated and solidified at a first temperature and a second temperature respectively to obtain an in-situ solidified electrolyte; wherein the first temperature is 45° C. to 65° C., and the second temperature is 65° C. to 85° C.

[0022] In a third aspect, the present application provides a lithium-ion battery, comprising the in-situ solidified electrolyte described in any one embodiment of the first aspect.

[0023] The above technical solution provided by this application has the following advantages compared with the existing technology:

[0024] The in-situ solidified electrolyte provided by the present application, the polymer monomer undergoes an addition reaction through an initiator under a heating environment to form a high molecular polymer with a cross-linked network structure, thereby improving the solidification ability of the reaction system to fix the liquid and reducing the ability to leak, thereby improving the safety of the battery; the phosphate flame retardant has the characteristics of high boiling point, high flash point and non-flammability, thereby improving the thermal stability of the battery and reducing the risk of thermal runaway; and it is dissolved in the electrolyte, and the solution is uniform and transparent, which is conducive to the formation of an ideal in-situ solidified electrolyte, thereby improving the safety of the battery. The polymer monomer and the flame retardant each have a corresponding promoting effect on the safety of the battery, and no side reaction will occur between the two. Therefore, under the synergistic effect of the polymer monomer and the phosphate flame retardant, the technical problem of the high safety hazards of existing lithium-ion batteries is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0027] FIG1 is a diagram of electrolyte flow before and after curing provided in Example 1 of the present application; wherein a-before curing, b-after curing;

[0028] FIG2 is a graph showing a lithium-ion battery cycle performance test according to Example 1 of the present application;

[0029] FIG3 is a graph showing the results of a lithium-ion battery puncture test provided in Example 1 of the present application; wherein a represents current / voltage-time, and b represents temperature-time;

[0030] FIG4 is a graph showing the results of an extrusion test of a lithium-ion battery provided in Example 1 of the present application; wherein a represents current / voltage-time and b represents temperature-time;

[0031] FIG5 is a schematic flow chart of a method for preparing an in-situ solidified electrolyte provided in an embodiment of the present application. DETAILED DESCRIPTION

[0032] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0033] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0034] In this application, unless otherwise specified, the directional words used, such as "upper" and "lower", refer specifically to the directions of the drawings in the accompanying drawings. In addition, in the description of the present application specification, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" refers to one or more, and "plurality" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple.

[0035] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0036] In a first aspect, the present application provides an in-situ solidified electrolyte, the raw material components of which include an initiator and an electrolyte, and the raw material components further include: a polymer monomer and a phosphate flame retardant; wherein,

[0037] The polymer monomers undergo a chemical reaction with the initiator to form a high molecular polymer having a cross-linked network structure;

[0038] The phosphate flame retardant is dissolved in the electrolyte and then becomes uniform and transparent.

[0039] In the embodiments of the present application, the polymer monomer undergoes an addition reaction with the initiator under a heated environment to form a high molecular weight polymer with a cross-linked network structure, thereby improving the reaction system's ability to solidify the liquid and reduce leakage, thereby improving the safety of the battery; the phosphate flame retardant has high boiling point, high flash point and non-flammability, thereby improving the thermal stability of the battery and reducing the risk of thermal runaway; and it dissolves in the electrolyte, and the solution is uniform and transparent, which is conducive to the formation of an ideal in-situ solidified electrolyte, thereby improving the safety of the battery. The polymer monomer and the flame retardant each have a corresponding promoting effect on battery safety, and no side reactions will occur between the two. Therefore, under the synergistic effect of the polymer monomer and the phosphate flame retardant, the technical problem of the high safety risks of existing lithium-ion batteries is solved.

[0040] The electrolyte provides a medium for conducting lithium ions during the battery's electrochemical reaction. The electrolyte's ability to conduct lithium ions ensures smooth charging and discharging. The electrolyte includes additives and lithium salts. The additives can be one or more combinations of vinylene carbonate (VC), 1,3-propane sultone (PS), fluoroethylene carbonate (FEC), ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). The lithium salts can be one or more combinations of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonimide) (LiTFSI), lithium bis(fluorosulfonimide) (LiFSI), and lithium difluorooxalatoborate (LiDFOB). Preferably, the additive components are vinylene carbonate, 1,3-propane sultone, fluoroethylene carbonate, ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate; wherein, by weight, vinylene carbonate is 1 part, 1,3-propane sultone is 1 part, fluoroethylene carbonate is 2 to 5 parts, ethylene carbonate is 5 to 13 parts, ethyl methyl carbonate is 8 to 12 parts, and dimethyl carbonate is 74 to 75 parts; the lithium salt is lithium hexafluorophosphate, and its molar concentration is 1 mol / L. The electrolyte has good electrochemical properties, thereby ensuring a long life of the battery, and can maintain a stable interface between the electrolyte and the electrode during the battery cycle, and is not prone to forming side reactions that cause battery performance degradation; and the content of the above components is controlled to ensure that the electrolyte has good electrochemical properties and good fluidity, and can ensure good wetting effect between the electrolyte and the electrode material before solidification, ensuring efficient transmission of lithium ions. Using lithium hexafluorophosphate (LiPF6) as the lithium salt results in a high conductivity (0.7 mS / cm) organic electrolyte. Furthermore, the raw material is stable, has good solubility, does not react with flame retardants or additives, and has low toxicity. The initiator can be one or a combination of azobisisobutyronitrile (AIBN), azobisisoheptanenitrile (ABVN), and dimethyl azobisisobutyrate (AIBME); preferably, azobisisobutyronitrile is used.

[0041] In some embodiments, the phosphate flame retardant includes at least one of the following: triethyl phosphate (TEP), triphenyl phosphate (TPP), and tributyl phosphate (TBP).

[0042] In the embodiments of the present application, since the organic electrolyte is flammable and explosive, there are certain safety hazards. In order to further improve the safety of the battery, phosphates are added as flame retardants. Phosphate flame retardants have the characteristics of high boiling point, high flash point, and non-flammability. At the same time, they can be well dissolved in the electrolyte, and the solution is uniform and transparent. Adding an appropriate amount of phosphate flame retardants will not affect the electrochemical properties of the battery, and at the same time, it can improve the safety of the battery. It is a flame retardant auxiliary with excellent performance. At least one of triethyl phosphate, triphenyl phosphate, and tributyl phosphate is selected as the phosphate flame retardant, which is easy to obtain, low in price, and has good non-flammable properties. Preferably, tributyl phosphate can be selected.

[0043] In some embodiments, the polymer monomer includes at least one of the following: a monomer containing an unsaturated bond, and a cyclic monomer.

[0044] The in-situ solidified electrolyte provided in the embodiment of the present application adopts the above-mentioned monomer or cyclic monomer containing an unsaturated bond. The monomer undergoes an addition reaction under the action of a heating environment and an initiator to form a high molecular polymer. After the reaction, a cross-linked network structure can be formed, which is of great help in improving the system's ability to fix liquids and reducing leakage, thereby improving the safety of the electrolyte.

[0045] In some embodiments, the monomer containing an unsaturated bond includes at least one of the following: vinylene carbonate and succinonitrile.

[0046] In some embodiments, the cyclic monomer includes at least one of the following: dioxolane and 1,4-butyrolactone.

[0047] In the embodiments of the present application, vinylene carbonate and succinonitrile have unsaturated bonds. Under the action of a heating environment and an initiator, an addition reaction occurs to form a high molecular weight polymer, which can form a cross-linked network structure after the reaction. Dioxolane and 1,4-butyrolactone have a cyclic structure and are easily ring-opened. Under the action of a heating environment and an initiator, an addition reaction occurs to form a high molecular weight polymer, which can form a cross-linked network structure after the reaction. Vinylene carbonate is preferred. The gel electrolyte is prepared by in-situ polymerization of thermally initiated monomers using vinylene carbonate (VC) as the main component. This method is simple and easy to implement, suitable for large-scale production, and improves battery safety performance. Vinylene carbonate has two functional groups: a carbon-carbon double bond and a carbon-oxygen double bond. Under the action of a heating environment and an initiator, the carbon-carbon double bond undergoes ring opening and undergoes multiple addition reactions to form a high molecular polymer. At the same time, an organic electrolyte is introduced because vinylene carbonate (―O―(C=O)―O―) can form a coordination bond with lithium ions. Since lithium ions are Lewis acids and have no electrons in their outermost orbits, the oxygen atoms in vinylene carbonate can provide electrons for lithium ions, thereby forming a coordination bond. Under the action of an electric field, they undergo directional migration and complete the migration of lithium ions. In addition, after polymerization, vinylene carbonate can form a cross-linked network structure, which is very helpful in improving the system's ability to fix liquids and reducing leakage.

[0048] In some embodiments, the volume ratio of the polymer monomer to the phosphate flame retardant is (1-5):(1-3).

[0049] In some embodiments, the volume ratio is 1:1.

[0050] In the embodiment of the present application, controlling the volume ratio of the polymer monomer to the phosphate flame retardant can first ensure the safety of the electrolyte, secondly ensure that the electrolyte and the electrode form a stable and dense interface in the early stage of the charge and discharge cycle, and finally ensure the long life and high safety of the battery. If the above ratio is not met, the safety of the battery will be reduced to a certain extent, and fire and explosion may occur under the conditions of collision and extrusion. If the amount of the flame retardant added is too much, the electrolyte will become viscous and have poor fluidity to a certain extent, and the electrochemical properties of the electrolyte will be reduced, thereby affecting the performance of the battery. If the amount of the flame retardant added is too little, the safety performance of the battery cannot be improved to a certain extent. If the amount of the polymer monomer used is too much, it will lead to poor curing effect and insufficient reaction to a certain extent, and may also reduce the electrochemical performance. If the amount of the polymer monomer used is too little, it will lead to poor curing effect to a certain extent, increase the risk of leakage, and thus reduce the safety performance. Specifically, the volume ratio of the polymer monomer to the phosphate flame retardant can be 1:1, 5:3, 3:2, 2:1, 5:1, 5:2, 2:3, 4:3, etc. Preferably, the volume ratio of the polymer monomer to the phosphate flame retardant may be 1:1.

[0051] In a second aspect, the present application provides a method for preparing an in-situ solidified electrolyte, as shown in FIG5 , for preparing the in-situ solidified electrolyte according to any one embodiment of the first aspect, the method comprising:

[0052] S1, mixing a polymer monomer, an initiator, an electrolyte, and a phosphate flame retardant to obtain a precursor solution;

[0053] S2. Heating and curing the precursor solution in stages to obtain an in-situ cured electrolyte.

[0054] In the embodiments of this application, curing is performed in stages to allow the electrolyte to fully penetrate the electrode material, ensuring good contact between the electrolyte and the electrode material, thereby ensuring efficient lithium ion transmission. If the curing temperature is too high, the curing speed will be too fast, and the electrode and electrolyte will not form good contact, resulting in poor battery performance. Therefore, a staged curing process is adopted.

[0055] In some embodiments, the step of heating and curing the precursor solution in stages to obtain an in-situ cured electrolyte comprises:

[0056] The precursor solution is heated and solidified at a first temperature and a second temperature to obtain an in-situ solidified electrolyte; wherein,

[0057] The first temperature is 45°C to 65°C, and the second temperature is 65°C to 85°C.

[0058] In the embodiments of this application, the "first temperature" corresponds to the first-stage curing temperature, with a curing time of 8 hours; the "second temperature" corresponds to the second-stage curing temperature, with a curing time of 2 hours. Controlling the first-stage curing temperature ensures sufficient contact and wetting between the electrolyte and the electrode materials, ensuring efficient lithium ion transfer and good battery cycling performance, and ensuring a good curing effect, thereby improving battery safety. If the temperature is too high, the curing speed will be too fast, and the electrolyte and electrode materials will not be able to achieve sufficient contact, resulting in impeded lithium ion transfer and affecting the electrochemical performance of the battery. If the temperature is too low, the curing effect will not be achieved, and a solidified electrolyte will not be obtained, thereby affecting battery safety. Specifically, the first-stage curing temperature can be 45°C, 50°C, 55°C, 60°C, 65°C, etc. Controlling the second-stage curing temperature accelerates the curing effect and shortens the curing time. If the temperature is too high, it may cause excessive side reactions, leading to a decrease in electrolyte performance. If the temperature is too low, the curing time will be too long, which is not conducive to process scalability. Specifically, the temperature of the second stage curing may be 65°C, 70°C, 75°C, 80°C, 85°C, etc.

[0059] The preparation method of the in-situ solidifying electrolyte is implemented based on the above-mentioned in-situ solidifying electrolyte. The raw material components of the in-situ solidifying electrolyte can be specifically referred to the above-mentioned embodiments. Since the preparation method of the in-situ solidifying electrolyte adopts part or all of the technical solutions of the above-mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here one by one.

[0060] In a third aspect, the present application provides a lithium-ion battery, comprising the in-situ solidified electrolyte described in any one embodiment of the first aspect.

[0061] In the embodiments of the present application, the above-mentioned in-situ solidified electrolyte is applied to lithium-ion batteries, which not only has good battery performance but also has good safety performance.

[0062] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are usually measured in accordance with national standards. If there are no corresponding national standards, then the methods are carried out in accordance with general international standards, conventional conditions, or according to the conditions recommended by the manufacturer.

[0063] Example 1

[0064] The raw material components of the in-situ solidified electrolyte include the following:

[0065] Electrolyte, triethyl phosphate, vinylene carbonate, azobisisobutyronitrile; among them, 50ml (about 62g) electrolyte (VC:PS:FEC:EC:EMC:DMC=1:1:2:13:8:75, 1mol / L LiPF6), triethyl phosphate (TEP) 50ml (about 53.47g), vinylene carbonate (VC) 50ml (about 68g) (electrolyte: TEP: VC volume ratio 1:1:1).

[0066] The preparation method of the in-situ solidified electrolyte comprises the following steps:

[0067] 50ml (about 62g) of electrolyte (VC:PS:FEC:EC:EMC:DMC=1:1:2:13:8:75, 1mol / L LiPF6), 50ml (about 53.47g) of triethyl phosphate (TEP), and 50ml (about 68g) of vinylene carbonate (VC) were added to a 500ml beaker (the ratio of electrolyte: TEP: VC was controlled at 1:1:1), and then 2wt% of azobisisobutyronitrile (AIBN) initiator was added. After stirring to completely dissolve the initiator and fully mix, about 30ml of the mixed solution was taken into a sample bottle, and then placed in an oven for heating and curing. The first stage of curing was at 60°C for 8h; the second stage of curing was at 80°C for 2h.

[0068] Example 2

[0069] The heating curing was set as follows: first stage curing: 55°C, 8h; second stage curing: 70°C, 2h, and the rest was the same as in Example 1.

[0070] Example 3

[0071] The heating curing was set as follows: first stage curing: 45°C, 8h; second stage curing: 65°C, 2h, and the rest was the same as in Example 1.

[0072] Example 4

[0073] The volume ratio of electrolyte:TEP:VC in the embodiment was set to 5:3:5, and the rest was the same as in Example 1.

[0074] Example 5

[0075] The volume ratio of electrolyte:TEP:VC in the embodiment was set to 4:2:3, and the rest was the same as in Example 1.

[0076] The preparation of lithium-ion batteries includes the following:

[0077] The precursor solution of the in-situ solidified electrolyte of Examples 1 to 5 is used to prepare a lithium-ion battery, which has the same composition as a conventional battery, including components such as a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, an aluminum-plastic film, and a tab; wherein,

[0078] The positive electrode material can be a mixture of one or more of lithium iron phosphate (LFP) ternary positive electrode material (NCM), lithium cobalt oxide (LCO), lithium iron manganese phosphate (LMFP), and lithium manganese oxide (LMP); the negative electrode material can be a mixture of one or more of graphite material, silicon oxide material, silicon material, and lithium metal negative electrode; the conductive agent can be a mixture of one or more of conductive graphite, conductive carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, nanofibers (VGCF), and graphene; the binder can be a mixture of one or more of sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, and polyvinylidene fluoride; the solvent can be N-methylpyrrolidone; the above-mentioned diaphragm base film is a porous film, and one or a mixture of polyethylene diaphragm (PE) and polypropylene diaphragm (PP) is used as the diaphragm, and the diaphragm is not modified in any way.

[0079] Adopt transfer or extrusion coating method, the negative electrode surface density is 2-5 mg / cm 2 , the positive electrode surface density is 5-10 mg / cm 2 After drying, roller press to control the negative electrode compaction density to 0.5~1.5mg / cm 3 The positive electrode compaction density is 2.5-3.5 mg / cm 3 The battery electrodes are obtained by die-cutting. The electrodes are stacked in a Z-shaped pattern and then go through processes such as tab welding, drying, liquid injection, curing, formation, fine sealing, and capacity separation to produce a highly safe lithium-ion battery.

[0080] Comparative Example 1

[0081] A conventional organic liquid electrolyte was used as the electrolyte, and its composition (VC:PS:FEC:EC:EMC:DMC=1:1:2:13:8:75, 1 mol / L LiPF6) was used to prepare a lithium-ion battery. The preparation process did not include a curing process, and the rest was the same as Examples 1 to 5.

[0082] The lithium-ion batteries prepared in Examples 1 to 5 and Comparative Example 1 were subjected to cycle tests. The positive electrode of the battery used lithium iron phosphate (LFP) and the negative electrode used lithium metal. The test results are shown in Table 1.

[0083] Table 1 Lithium-ion battery cycle test results

[0084] The in-situ solidified electrolyte provided in the examples of the present application has a good solidification effect. Specifically, the in-situ solidified electrolyte prepared in Example 1 exhibits obvious liquid fluidity before heat curing, as shown in Figure 1a. After heating, the mixed solution has an obvious solidification effect, as shown in Figure 1b. For Example 1, the cycle performance is shown in Figure 2. The initial discharge specific capacity is 138.2mAh / g (theoretical specific capacity 170mAh / g), and the capacity retention rate after 300 cycles is 97.5% (the capacity retention rate of commercial liquid batteries after 300 cycles is ≥95%, and GB38031 requires a capacity retention rate of ≥94% after 300 cycles). The battery using the solidified electrolyte has good cycle performance. The batteries prepared in Examples 1 to 5 all have good cycle performance.

[0085] Safety tests were performed on the lithium-ion batteries of Examples 1 to 5 and Comparative Example 1, mainly including needle penetration and extrusion tests. The test results are shown in Table 2.

[0086] Table 2 Lithium-ion battery puncture and extrusion test results

[0087] Combined with Table 2, specifically, the lithium-ion battery prepared in Example 1, the needle penetration test results are shown in Figures 3a and 3b. The temperature-time test results show that the battery temperature did not increase significantly. The current / voltage-time test graph shows that the voltage drops very slowly, the current basically does not change, and the battery does not catch fire or explode, showing good safety performance. The extrusion test results also show that the battery has good safety performance. The temperature-time test results show that the battery temperature did not increase significantly. The current / voltage-time test graph shows that the voltage and current basically do not change, as shown in Figures 4a and 4b. In summary, this lithium-ion battery has good safety performance.

[0088] In Examples 1 to 5, a solid electrolyte was prepared by a thermal initiation method using vinylene carbonate (VC), electrolyte, initiator (azobisisobutyronitrile), and trimethyl phosphate (TEP) as main raw materials. The solidified electrolyte was applied to lithium-ion batteries and had good electrochemical performance and safety. The capacity retention rate after 300 cycles reached 97%, and 100% of the tests were passed through the puncture and extrusion safety tests. The liquid lithium-ion battery in Comparative Example 1 could not pass the puncture and extrusion safety tests. In the above embodiments, not only the content of the electrolyte in the battery was reduced, which prevented battery leakage and environmental pollution, but also the unsafe conditions of flammability and explosion of the organic electrolyte were alleviated (Comparative Example 1). Moreover, the process is simple, suitable for large-scale production, and greatly improves the safety performance of the battery. The solid-state battery using this curing scheme not only has good battery performance, but also has good safety performance.

[0089] Compared with the prior art, the embodiments of the present application have the following advantages:

[0090] The in-situ solidified electrolyte provided by the embodiment of the present application, the polymer monomer undergoes an addition reaction through the initiator under a heating environment to form a high molecular polymer with a cross-linked network structure, thereby improving the solidification ability of the reaction system to fix the liquid and reducing the ability to leak, thereby improving the safety of the battery; the phosphate flame retardant has the characteristics of high boiling point, high flash point and non-flammability, thereby improving the thermal stability of the battery and reducing the risk of thermal runaway; and it is dissolved in the electrolyte, and the solution is uniform and transparent, which is conducive to the formation of an ideal in-situ solidified electrolyte, thereby improving the safety of the battery. The polymer monomer and the flame retardant each have a corresponding promoting effect on the safety of the battery, and no side reaction will occur between the two. Therefore, under the synergistic effect of the polymer monomer and the phosphate flame retardant, the technical problem of the high safety hazards of existing lithium-ion batteries is solved.

[0091] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. An in-situ solidified electrolyte, the raw material components include an initiator and an electrolyte, and the raw material components also include: Polymer monomers and phosphate flame retardants; wherein, The polymer monomer undergoes a chemical reaction through the initiator to form a high molecular polymer having a cross-linked network structure; The phosphate flame retardant is dissolved in the electrolyte and then becomes uniform and transparent.

2. The in-situ solidified electrolyte according to claim 1, wherein: The phosphate flame retardant includes at least one of the following: triethyl phosphate, triphenyl phosphate, and tributyl phosphate.

3. The in-situ solidified electrolyte according to claim 1, wherein: The polymer monomer includes at least one of the following: a monomer containing an unsaturated bond and a cyclic monomer.

4. The in-situ solidified electrolyte according to claim 3, wherein: The monomer containing an unsaturated bond includes at least one of the following: vinylene carbonate and succinonitrile.

5. The in-situ solidified electrolyte according to claim 3, wherein: The cyclic monomer includes at least one of the following: dioxolane and 1,4-butyrolactone.

6. The in-situ solidified electrolyte according to any one of claims 1 to 5, wherein: The volume ratio of the polymer monomer to the phosphate flame retardant is (1-5):(1-3).

7. The in-situ solidified electrolyte according to claim 6, wherein: The volume ratio is 1:

1.

8. A method for preparing the in-situ solidified electrolyte according to any one of claims 1 to 7, the method comprising: Mixing polymer monomers, initiators, electrolytes and phosphate flame retardants to obtain a precursor solution; The precursor solution is heated and cured in stages to obtain an in-situ cured electrolyte.

9. The method according to claim 8, wherein: The step of heating and curing the precursor solution in stages to obtain an in-situ cured electrolyte comprises: The precursor solution is heated and cured at a first temperature and a second temperature respectively to obtain an in-situ cured electrolyte; wherein, The first temperature is 45°C to 65°C, and the second temperature is 65°C to 85°C.

10. A lithium ion battery, comprising the in-situ solidified electrolyte according to any one of claims 1 to 7.

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