A flame-retardant gel electrolyte for lithium-ion batteries, its preparation method and application

Abstract

This invention belongs to the field of secondary battery technology, specifically relating to a flame-retardant gel electrolyte for lithium-ion batteries, and further disclosing a preparation process based on in-situ thermal polymerization, as well as the application of the flame-retardant gel electrolyte. The flame-retardant gel electrolyte of this invention uses acrylonitrile, a phosphorus-containing vinyl compound of a selected structure, and terminal vinyl silicone oil as reactive monomers. Under the action of an initiator and crosslinking agent, it is prepared by directly adding it to a commercial liquid electrolyte and injecting it into the assembled battery using an in-situ thermal polymerization method. The flame-retardant gel electrolyte of this invention has high ion mobility number, good flame-retardant properties, and excellent electrochemical stability. It can reduce the exothermic reaction of oxidation / combustion in organic electrolytes, prevent battery thermal runaway caused by electrolyte / electrode thermal decomposition, and improve the safety of lithium-ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a flame-retardant gel electrolyte for lithium-ion batteries, and further disclosing a preparation process based on in-situ thermal polymerization, as well as the application of the flame-retardant gel electrolyte. Background Technology

[0002] With the growing acceptance of the carbon neutrality concept, related industries such as new energy vehicles have developed rapidly. Lithium-ion batteries, with their advantages of high energy density, long cycle life, and high operating voltage, not only dominate the field of automotive power batteries but are also widely used in many high-tech fields such as mobile communications, satellites, and high-end electronic devices. In recent years, with the rapid development and popularization of electric vehicles, people have raised higher standards for the safety of power lithium-ion batteries. However, as the energy density of lithium-ion batteries continues to increase, the inherent safety hazards also greatly limit their production and use.

[0003] Studies show that thermal runaway is the main cause of safety accidents in lithium-ion batteries. Currently, lithium-ion batteries mainly consist of three parts: electrodes, separators, and electrolytes. Most commercial lithium-ion batteries use liquid organic electrolytes. Due to their low flash point, low vapor pressure, and high fluidity, these electrolytes are prone to leakage. Moreover, because of their low decomposition voltage, they are easily decomposed under high pressure, which can even lead to combustion or explosion, posing significant safety hazards and thus limiting their application in energy storage devices.

[0004] Currently, the main methods for addressing lithium battery safety issues include: all-solid-state lithium-ion battery solutions, adding flame retardants to the electrolyte, and gel electrolyte solutions. All-solid-state lithium-ion batteries can effectively solve safety problems, but they have high interfacial impedance and poor low-temperature performance, resulting in poor rate capability and cycle performance, making them unsuitable for current power battery requirements. Adding flame retardants to the electrolyte can effectively improve lithium battery safety, but the presence of free flame retardants increases internal resistance, reduces electrochemical stability, and still carries the risk of leakage. Gel electrolytes, due to the ionic conductivity and chemical properties of gel polymers being closer to liquid electrolytes and their safety performance closer to solid electrolytes, can improve lithium battery safety to some extent while maintaining excellent ionic conductivity, offering broader development potential. However, the flammability of the gel electrolyte polymer matrix itself means that the flame retardant performance of gel electrolyte lithium-ion batteries remains unsatisfactory.

[0005] Chinese patent CN112582670A discloses a method for preparing a flame-retardant gel electrolyte membrane. The gel electrolyte membrane consists of a phosphorus-containing polymer backbone and a commercial electrolyte. This flame-retardant gel electrolyte membrane can reduce the exothermic reaction of oxidation / combustion in organic electrolytes, thus improving battery safety. Chinese patent CN114976236A discloses a flame-retardant gel electrolyte for lithium metal. The polyethyl acrylate acrylic gel electrolyte prepared by this method exhibits high ionic conductivity and lithium-ion migration ability, good electrochemical stability, and excellent flame retardancy at room temperature. However, most gel electrolyte membranes suffer from complex preparation steps when applied to lithium-ion batteries, limiting their further development. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to provide a flame-retardant gel electrolyte for lithium-ion batteries, wherein the flame-retardant gel electrolyte has good flame-retardant properties and electrochemical properties.

[0007] The second technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned flame-retardant gel electrolyte, wherein the flame-retardant gel electrolyte is prepared on-site based on the on-site thermal polymerization method, which has the advantages of simple processing and convenient operation;

[0008] The third technical problem to be solved by the present invention is to provide the application of the above-mentioned flame-retardant gel electrolyte;

[0009] The fourth technical problem to be solved by the present invention is to provide a flame-retardant gel polymer and further disclose its use in preparing flame-retardant gel electrolytes.

[0010] To solve the above-mentioned technical problems, the present invention provides a flame-retardant gel electrolyte for lithium-ion batteries, the raw materials of which include the following components in parts by weight:

[0011] 3-5 parts by weight of phosphorus-containing vinyl compounds;

[0012] 3-5 parts by weight of acrylonitrile;

[0013] 3-5 parts by weight of vinyl-terminated silicone oil;

[0014] Initiator 0.5-1 parts by weight;

[0015] 2-3 parts by weight of crosslinking agent;

[0016] 100-110 parts by weight of electrolyte.

[0017] The lithium-ion battery flame-retardant gel electrolyte of the present invention is formed by polymerizing various monomer components in a selected ratio to form a mixture of polymers with multiple polymer structures, thereby forming the desired gel electrolyte.

[0018] Specifically, in the lithium-ion battery flame-retardant gel electrolyte, the phosphorus-containing vinyl compound is the reaction product of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and 1,5-hexadiene.

[0019] Preferably, in the lithium-ion battery flame-retardant gel electrolyte, the mass ratio of the phosphorus-containing vinyl compound, acrylonitrile, and terminal vinyl silicone oil is 1:1:1.

[0020] Specifically, the lithium-ion battery flame-retardant gel electrolyte:

[0021] The viscosity of the vinyl-terminated silicone oil is 3000-5000 mPa·s; and / or,

[0022] The initiator includes azobisisobutyronitrile (AIBN); and / or,

[0023] The crosslinking agent includes triethylene glycol dimethacrylate; and / or,

[0024] The lithium salts contained in the electrolyte include lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and / or lithium bis(fluorosulfonyl)imide (LiFSI).

[0025] This invention also discloses a method for preparing the flame-retardant gel electrolyte for lithium-ion batteries, comprising the following steps:

[0026] (1) Take a selected amount of the phosphorus-containing vinyl compound, acrylonitrile, terminal vinyl silicone oil, initiator, and crosslinking agent, and add them to a selected amount of the electrolyte and mix.

[0027] (2) The obtained mixed electrolyte is injected into the assembled lithium-ion soft-pack battery and sealed. After standing, it is heated to form the required flame-retardant gel electrolyte in the lithium-ion battery.

[0028] Preferably, step (1) further includes a step of preparing the desired phosphorus-containing vinyl compound by reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and 1,5-hexadiene as raw materials.

[0029] Specifically, in the preparation method of the flame-retardant gel electrolyte for lithium-ion batteries, step (2) includes:

[0030] The settling step includes setting the temperature at 40-50℃ for 45-50 hours.

[0031] The heating reaction step includes heating the reaction at 55-65°C for 8-12 hours.

[0032] The present invention also discloses a flame-retardant gel electrolyte for lithium-ion batteries prepared by the above method. Based on the polymerization reaction of each monomer component in a selected ratio, a mixture of polymers with multiple polymer structures can be formed to form the desired gel electrolyte.

[0033] The present invention also discloses a flame-retardant gel polymer having the structure shown in formula (Ⅰ):

[0034]

[0035] Wherein, a1, a2, b1, and b2 are independent integers selected from 0 or 1, and a1 and a2 are not both 0 at the same time, and b1 and b2 are not both 0 at the same time.

[0036] The present invention also discloses a flame-retardant gel electrolyte for lithium-ion batteries, comprising a flame-retardant gel polymer having the structure shown in formula (I), or a mixture of flame-retardant gel polymers having different structures as shown in formula (I).

[0037] In the flame-retardant gel electrolyte for lithium-ion batteries of this invention, in the flame-retardant gel polymer with the structure shown in formula (Ⅰ), a1, a2, b1, and b2 are independently selected from integers of 0 or 1, thus forming compositions of polymers with different structures. Simultaneously, a1 and a2 are not both 0, and b1 and b2 are not both 0, to ensure that the gel electrolyte contains phosphorus-containing vinyl compounds. This improves the flame-retardant performance and electrochemical stability of the gel electrolyte, reduces the exothermic reaction of the organic electrolyte oxidation / combustion, prevents battery thermal runaway due to electrolyte / electrode thermal decomposition, and improves the safety of the lithium-ion battery. The introduction of terminal vinyl silicone oil, due to its flexible molecular chain structure and strong chain mobility, effectively increases the ion transference number of the gel electrolyte, thereby improving the electrical performance of the lithium-ion battery. In the polymer, the value of n depends on the structure of the selected silicone oil and has no effect on the performance and effect of its gel electrolyte.

[0038] In the lithium-ion battery flame-retardant gel electrolyte of the present invention, the mixing ratio of polymers with different polymerization structures has no effect on the properties of the gel electrolyte. Under the selected monomer ratio, the mixture of polymers with multiple structures formed by polymerization all have good application performance.

[0039] The present invention also discloses a lithium-ion battery, including a casing, a positive electrode, a negative electrode, a separator, and a gel electrolyte;

[0040] The gel electrolyte includes the flame-retardant gel electrolyte, or the flame-retardant gel electrolyte prepared by the method, or a flame-retardant gel electrolyte comprising a mixture of flame-retardant gel polymers having a structure as shown in Formula (I);

[0041] Preferably, the lithium-ion battery is a ternary soft-pack battery.

[0042] The present invention also discloses the use of the flame-retardant gel electrolyte, or the flame-retardant gel electrolyte prepared by the method, or the flame-retardant gel electrolyte comprising a mixture of flame-retardant gel polymers having a structure as shown in formula (I), for the preparation of lithium-ion batteries;

[0043] or,

[0044] The flame-retardant gel polymer is used to prepare flame-retardant gel electrolytes or lithium-ion batteries containing flame-retardant gel electrolytes.

[0045] The flame-retardant gel electrolyte of this invention uses acrylonitrile, a phosphorus-containing vinyl compound with a selected structure, and terminal vinyl silicone oil as reactive monomers, which are polymerized under the action of an initiator and a crosslinking agent to form a flame-retardant polymer. The introduction of the phosphorus-containing vinyl compound can improve the flame-retardant properties and electrochemical stability of the gel electrolyte, reduce the exothermic oxidation / combustion reaction of the organic electrolyte, prevent battery thermal runaway due to electrolyte / electrode thermal decomposition, and improve the safety of lithium-ion batteries. The introduction of terminal vinyl silicone oil, due to its flexible molecular chain structure and strong chain mobility, effectively increases the ion transport number of the gel electrolyte, thereby improving the electrical performance of lithium-ion batteries. The flame-retardant gel electrolyte of this invention has a high ion transport number, good flame-retardant properties, and excellent electrochemical stability, which can reduce the exothermic oxidation / combustion reaction of the organic electrolyte, prevent battery thermal runaway due to electrolyte / electrode thermal decomposition, and improve the safety of lithium-ion batteries.

[0046] The flame-retardant gel electrolyte of this invention is prepared by on-site thermal polymerization. By adding raw materials such as acrylonitrile, phosphorus-containing vinyl compounds, terminal vinyl silicone oil, initiators and crosslinking agents to a commercial liquid electrolyte and directly injecting it into the assembled battery, the polymerization is initiated by heat. This method can prepare the flame-retardant gel electrolyte without significantly changing the existing lithium-ion battery process, and has the advantage of simple operation. Attached Figure Description

[0047] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0048] Figure 1 The results show the cycle capacity retention of lithium-ion batteries obtained in Examples 1-3 and Comparative Example 1. Detailed Implementation

[0049] The present invention will be specifically described below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments based on the above-described invention, which still fall within the scope of protection of the present invention.

[0050] In the following embodiments of the present invention, the electrolyte involved can be any commercially available electrolyte in the art. The molecular weight (i.e., parameter n value) of the vinyl-terminated silicone oil used has no effect on the performance and effect of the gel electrolyte. The viscosity of the vinyl-terminated silicone oil is preferably 3000-5000 mPa·s. The molecular weight and parameters of the selected acrylonitrile have no effect on the effect of the gel electrolyte.

[0051] Preparation Example 1

[0052]

[0053] Following the above reaction procedure, 21.6 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and 8.2 g of 1,5-hexadiene were placed in a 250 ml three-necked flask and reacted at 80 °C for 3 h. The reaction product was collected, washed, filtered, and dried to obtain the desired phosphorus-containing vinyl compound.

[0054] Example 1

[0055] This embodiment utilizes an in-situ thermopolymerization method to prepare the flame-retardant gel electrolyte. The specific reaction process is shown below, where the structural formula of the polymer represents a mixture of various polymers with different polymerization structures:

[0056]

[0057] Three parts by weight of a phosphorus-containing vinyl compound (Preparation Example 1), three parts by weight of acrylonitrile, three parts by weight of vinyl-terminated silicone oil (viscosity 3000-5000 mPa·s), 0.5 parts by weight of an initiator (AIBN), and two parts by weight of a crosslinking agent (triethylene glycol dimethacrylate) were mixed into 100 parts by weight of a commercial electrolyte to obtain a mixed electrolyte. Then, according to the required amount of gel electrolyte in the lithium-ion battery, an appropriate amount of the mixed electrolyte was injected into the assembled lithium-ion pouch battery and sealed. After sealing, the battery was allowed to stand at 45°C for 48 hours, and then the temperature was raised to 60°C to continue the reaction for 10 hours, thereby forming the desired flame-retardant gel electrolyte mixture in the lithium-ion battery.

[0058] In the gel electrolyte formed in this embodiment, due to the presence of triethylene glycol dimethacrylate crosslinking agent and terminal vinyl silicone oil, a polymerization reaction can be formed between the phosphorus-containing vinyl compound and acrylonitrile, thereby forming a mixture of polymers with various structures to form the desired gel electrolyte.

[0059] In this embodiment, the introduction of phosphorus-containing vinyl compounds into the gel electrolyte mixture can improve the flame retardant properties and electrochemical stability of the gel electrolyte, reduce the exothermic reaction of the organic electrolyte oxidation / combustion, prevent battery thermal runaway caused by electrolyte / electrode thermal decomposition, and improve the safety of lithium-ion batteries. The introduction of terminal vinyl silicone oil, due to its flexible molecular chain structure and strong chain mobility, effectively increases the ion transference number of the gel electrolyte and improves the electrical performance of lithium-ion batteries.

[0060] Example 2

[0061] In this embodiment, the flame-retardant gel electrolyte is prepared by on-site thermopolymerization. The specific reaction process is the same as in Example 1. Each monomer component undergoes polymerization to form a mixture of polymers with multiple structures, thus forming the desired gel electrolyte.

[0062] Four parts by weight of a phosphorus-containing vinyl compound (Preparation Example 1), four parts by weight of acrylonitrile, four parts by weight of vinyl-terminated silicone oil, 0.75 parts by weight of an initiator (AIBN), and 2.5 parts by weight of a crosslinking agent (triethylene glycol dimethacrylate) were mixed into 105 parts by weight of a commercial electrolyte to obtain a mixed electrolyte. Then, according to the required amount of gel electrolyte in the lithium-ion battery, an appropriate amount of the mixed electrolyte was injected into the assembled lithium-ion pouch battery and sealed. After sealing, the battery was allowed to stand at 45°C for 48 hours, and then the temperature was raised to 60°C and the reaction continued for 10 hours to form the desired flame-retardant gel electrolyte in the lithium-ion battery.

[0063] Example 3

[0064] In this embodiment, the flame-retardant gel electrolyte is prepared by on-site thermopolymerization. The specific reaction process is the same as in Example 1. Each monomer component undergoes polymerization to form a mixture of polymers with multiple structures, thus forming the desired gel electrolyte.

[0065] Five parts by weight of a phosphorus-containing vinyl compound (Preparation Example 1), five parts by weight of acrylonitrile, five parts by weight of terminal vinyl silicone oil, one part by weight of an initiator (AIBN), and three parts by weight of a crosslinking agent (triethylene glycol dimethacrylate) were mixed into 110 parts by weight of a commercial electrolyte to obtain a mixed electrolyte. Then, according to the required amount of gel electrolyte in the lithium-ion battery, an appropriate amount of the mixed electrolyte was injected into the assembled lithium-ion pouch battery and sealed. After sealing, the battery was allowed to stand at 45°C for 48 hours, and then the temperature was raised to 60°C and the reaction continued for 10 hours to form the desired flame-retardant gel electrolyte in the lithium-ion battery.

[0066] Example 4

[0067] Five parts by weight of a phosphorus-containing vinyl compound (Preparation Example 1), five parts by weight of acrylonitrile, five parts by weight of terminal vinyl silicone oil, 0.5 parts by weight of an initiator, and two parts by weight of a crosslinking agent were mixed into 100 parts by weight of a commercial electrolyte to obtain a mixed electrolyte. This mixed electrolyte was then injected into an assembled lithium-ion pouch cell and sealed. After sealing, the mixture was allowed to stand at 40°C for 50 hours, and then the temperature was increased to 55°C and the reaction continued for 12 hours to form the desired flame-retardant gel electrolyte in the lithium-ion battery.

[0068] Example 5

[0069] Five parts by weight of a phosphorus-containing vinyl compound (Preparation Example 1), five parts by weight of acrylonitrile, five parts by weight of vinyl-terminated silicone oil, 0.75 parts by weight of an initiator, and one part by weight of a crosslinking agent were mixed into 105 parts by weight of a commercial electrolyte to obtain a mixed electrolyte. This mixed electrolyte was then injected into an assembled lithium-ion pouch cell and sealed. After sealing, the cell was allowed to stand at 50°C for 45 hours, and then the temperature was increased to 65°C and the reaction continued for 8 hours to form the desired flame-retardant gel electrolyte in the lithium-ion battery.

[0070] Comparative Example 1

[0071] 100 parts by weight of commercial electrolyte were injected into the assembled lithium-ion pouch cell, which was then sealed. After sealing, the cells were left to stand at 45°C for 48 hours, and then the temperature was raised to 60°C and left to stand for another 10 hours.

[0072] Comparative Example 2

[0073] Five parts acrylonitrile, 0.75 parts initiator, and 1 part crosslinking agent were mixed into 105 parts commercial electrolyte to obtain a mixed electrolyte. This mixed electrolyte was then injected into an assembled lithium-ion pouch cell and sealed. After sealing, the mixture was allowed to stand at 50°C for 45 hours, and then the temperature was increased to 65°C and the reaction continued for 8 hours to form the desired flame-retardant gel electrolyte in the lithium-ion battery.

[0074] Experimental Example

[0075] 1. Flame retardant performance test of flame retardant gel electrolyte

[0076] Following the schemes of Examples 1-3 and Comparative Examples 1-2, respectively, phosphorus-containing vinyl compounds, acrylonitrile, terminal vinyl silicone oil, initiator and crosslinking agent were mixed into commercial electrolytes and directly prepared into flame-retardant gel electrolytes through reaction. The heat release during combustion was tested using a cone calorimeter, and the results are shown in Table 1 below.

[0077] Table 1. Heat release during combustion of different gel electrolytes

[0078] Serial Number <![CDATA[Maximum heat release rate / KW / m 2 > Example 1 432.5 Example 2 419.6 Example 3 398.7 Comparative Example 1 645.3 Comparative Example 2 592.4

[0079] As can be seen, the gel electrolyte of the present invention, which is formed by the reaction of phosphorus-containing vinyl compounds, acrylonitrile, and terminal vinyl silicone oil, can effectively reduce the heat release of the electrolyte during combustion, and its flame retardant performance and thermal stability are greatly improved, resulting in better battery performance.

[0080] 2. Battery performance test

[0081] The lithium-ion batteries prepared in Examples 1-3 and Comparative Example 1 were subjected to electrochemical constant current charge-discharge tests in a voltage range of 2.8-4.3V. The cycle capacity retention results are shown in the appendix. Figure 1 As shown.

[0082] As can be seen, compared with conventional commercially available electrolytes (Comparative Example 1), the lithium-ion batteries of the present invention exhibit better cycle performance, especially the lithium-ion batteries prepared in Examples 2 and 3, whose capacity retention rate is above 97% after 100 cycles. Therefore, the flame-retardant gel electrolyte prepared by the present invention possesses excellent electrical properties and superior application performance.

[0083] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A flame-retardant gel electrolyte for lithium-ion batteries, characterized in that, Its preparation raw materials include the following components in parts by weight: 3-5 parts by weight of phosphorus-containing vinyl compounds; 3-5 parts by weight of acrylonitrile; 3-5 parts by weight of vinyl-terminated silicone oil; Initiator 0.5-1 parts by weight; 2-3 parts by weight of crosslinking agent; 100-110 parts by weight of electrolyte; The lithium-ion battery flame-retardant gel electrolyte comprises a flame-retardant gel polymer having the structure shown in formula (I): ； （Ⅰ） Wherein, a1, a2, b1, and b2 are independent integers selected from 0 or 1, and a1 and a2 are not both 0 at the same time, and b1 and b2 are not both 0 at the same time.

2. The lithium-ion battery flame-retardant gel electrolyte according to claim 1, characterized in that, The phosphorus-containing vinyl compound is the reaction product of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 1,5-hexadiene.

3. The lithium-ion battery flame-retardant gel electrolyte according to claim 1 or 2, characterized in that, The mass ratio of the phosphorus-containing vinyl compound, acrylonitrile, and terminal vinyl silicone oil is 1:1:

1.

4. The flame-retardant gel electrolyte for lithium-ion batteries according to claim 1 or 2, characterized in that: The viscosity of the vinyl-terminated silicone oil is 3000-5000 mPa·s; and / or, The initiator includes azobisisobutyronitrile; and / or, The crosslinking agent includes triethylene glycol dimethacrylate; and / or, The lithium salts contained in the electrolyte include lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and / or lithium bis(fluorosulfonyl)imide (LiFSI).

5. A method for preparing the flame-retardant gel electrolyte for lithium-ion batteries according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Take a selected amount of the phosphorus-containing vinyl compound, acrylonitrile, terminal vinyl silicone oil, initiator, and crosslinking agent, and add them to a selected amount of the electrolyte and mix. (2) The obtained mixed electrolyte is injected into the assembled lithium-ion soft-pack battery and sealed. After standing, it is heated to form the required flame-retardant gel electrolyte in the lithium-ion battery.

6. The method for preparing the flame-retardant gel electrolyte for lithium-ion batteries according to claim 5, characterized in that, Step (1) further includes a step of preparing the desired phosphorus-containing vinyl compound by reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 1,5-hexadiene as raw materials; and / or, In step (2): The settling step includes setting the temperature at 40-50°C for 45-50 hours; and / or, The heating reaction step includes heating the reaction at 55-65°C for 8-12 hours.

7. A lithium-ion battery, characterized in that, It includes the outer shell, positive electrode, negative electrode, separator, and gel electrolyte; The gel electrolyte includes the flame-retardant gel electrolyte according to any one of claims 1-4, or the flame-retardant gel electrolyte prepared by the method according to claim 5 or 6.

8. The lithium-ion battery according to claim 7, characterized in that, The lithium-ion battery is a ternary soft-pack battery.

9. Use of the flame-retardant gel electrolyte according to any one of claims 1-4, or the flame-retardant gel electrolyte prepared by the method according to claim 5 or 6, in the preparation of lithium-ion batteries.

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