Gel electrolyte and use thereof

Abstract

Provided are a gel electrolyte and a use thereof. The gel electrolyte comprises a polymer backbone and an electrolyte applied to fill the polymer backbone. The polymer backbone is obtained by polymerizing a gel polymerization starting material system. The gel polymerization starting material system comprises trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, N,N'-methylenebisacrylamide, and an initiator, wherein the ratio of the total mass of trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate and N,N'-methylenebisacrylamide to the mass of the electrolyte ranges from 3:97 to 12:88. The gel electrolyte has a long cycle life, and also has high safety performance.

Description

A gel electrolyte and its application

[0001] This application claims priority to Chinese Patent Application No. 202411521925.0, filed on October 29, 2024, entitled "A Gel Electrolyte and Its Application", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of lithium-ion battery technology, and more particularly to a gel electrolyte and its applications. Background Technology

[0003] With the depletion of fossil fuels and the worsening of environmental pollution, countries worldwide are actively seeking to develop green and emerging economic industries. Against this backdrop, electric vehicles are gradually replacing traditional gasoline-powered vehicles, becoming a major trend in response to environmental protection requirements. The widespread adoption of electric vehicles places higher demands on the performance of power batteries. Next-generation power batteries need to possess higher energy density, wider electrochemical windows, longer cycle life, and greater ion migration efficiency. However, high-energy-density batteries may experience thermal runaway under conditions such as severe impacts, abuse, short circuits, overcharging, and over-discharging, causing serious harm. Therefore, the safety of power batteries is of paramount importance.

[0004] To improve safety, gel electrolytes have emerged. Compared with traditional liquid electrolytes, gel electrolytes can alleviate the problems of electrolyte evaporation and leakage to some extent. However, liquid electrolytes are still present in gel electrolytes, and their safety performance needs to be further improved. Summary of the Invention

[0005] To address the aforementioned deficiencies, this application provides a gel electrolyte that not only has a long cycle life but also high safety performance.

[0006] This application also provides a gel battery comprising the aforementioned gel electrolyte, thus the gel battery has high cycle performance and safety performance.

[0007] This application provides a gel electrolyte comprising a polymer backbone and an electrolyte filled within the polymer backbone; the polymer backbone is obtained by polymerization of a gel polymerization raw material system, the gel polymerization raw material system comprising trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, N,N-methylenebisacrylamide, and an initiator; wherein the total mass ratio of the trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, and N,N-methylenebisacrylamide to the electrolyte is 3:97 to 12:88.

[0008] Furthermore, the molar ratio of the methoxy polyethylene glycol acrylate to the trifluoroethyl methacrylate is 1:(1-5).

[0009] Furthermore, based on the total mass of the trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, N,N-methylenebisacrylamide, and electrolyte, the mass percentage of N,N-methylenebisacrylamide is 0.75% to 1.25%.

[0010] Furthermore, the initiator includes azobisisobutyronitrile and / or azobisisoheptanenitrile.

[0011] Furthermore, the mass ratio of the initiator to the electrolyte is 1:(1000~10000).

[0012] Furthermore, the number-average molecular weight of the methoxy polyethylene glycol acrylate is 480–1000.

[0013] Furthermore, the exothermic enthalpy of the gel electrolyte in the DSC test is not higher than 200 J / g.

[0014] This application also provides a gel battery, the gel battery comprising the gel electrolyte described in any of the above claims.

[0015] Furthermore, the gel battery is prepared by a method comprising the following steps:

[0016] A precursor solution is prepared by mixing raw materials including trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, and N,N-methylenebisacrylamide with an electrolyte. An initiator is then added to the precursor solution and injected into the battery. A gel electrolyte is generated through a polymerization reaction at a temperature of 45–75°C for 4–24 hours. After subsequent formation and capacity testing, the gel battery is obtained.

[0017] Furthermore, the N,N-methylenebisacrylamide in the precursor solution has a mass percentage content of 0.75% to 1.25%.

[0018] Furthermore, the gel battery also includes a positive electrode active material, which includes a ternary positive electrode material;

[0019] The nickel content of the ternary cathode material is not less than 60%.

[0020] This application describes a gel electrolyte comprising a polymer backbone and an electrolyte filled within the polymer backbone. The polymer backbone is obtained by polymerizing a gel polymerization raw material system comprising trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, N,N-methylenebisacrylamide, and an initiator. By controlling the ratio of the total mass of trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, and N,N-methylenebisacrylamide to the mass of the electrolyte, not only can the structural stability of the cathode material be effectively improved, but it also exhibits good flame retardant and wettability properties. Therefore, applying this gel electrolyte to gel batteries can effectively improve the cycle stability and safety performance of the batteries. Attached Figure Description

[0021] The accompanying drawings, which are provided to further illustrate this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application.

[0022] Figure 1 shows the viscoelastic curves of the gel electrolytes in Examples 1-3 of this application;

[0023] Figure 2 shows the relationship between the ionic conductivity and temperature of the gel electrolytes in Examples 1-3 of this application;

[0024] Figure 3 shows the LSV curves of the gel cells in Examples 1-3 and Comparative Example 1 of this application;

[0025] Figure 4 shows the DSC curves of the gel electrolytes in Examples 1-3 and Comparative Example 1 of this application;

[0026] Figure 5 shows the relationship between battery capacity and number of cycles in Examples 1-3 and Comparative Example 1 of this application;

[0027] Figure 6 shows photographs of the gel electrolyte in Example 1 of this application before and after ignition;

[0028] Figure 7 shows photographs of the liquid electrolyte in Comparative Example 1 of this application before and after ignition. Detailed Implementation

[0029] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0030] The first aspect of this application provides a gel electrolyte comprising a polymer backbone and an electrolyte filled in the polymer backbone; the polymer backbone is obtained by polymerization of a gel polymerization raw material system, the gel polymerization raw material system comprising trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, N,N-methylenebisacrylamide and an initiator; wherein the total mass ratio of trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate and N,N-methylenebisacrylamide to the mass ratio of the electrolyte is 3:97 to 12:88.

[0031] For example, the mass ratio is 3:97, 4:96, 5:95, 6:94, 7:93, 8:92, 9:91, 10:90, 11:89 or 12:88.

[0032] In this application, "the total mass ratio of trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, and N,N-methylenebisacrylamide to the electrolyte is 3:97 to 12:88" means that, based on the total mass of trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, N,N-methylenebisacrylamide, and the electrolyte, the electrolyte has a mass percentage content of 88% to 97%, with the remainder being trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, and N,N-methylenebisacrylamide.

[0033] This application does not specify the specific composition of the electrolyte; for example, conventional electrolytes in the art can be used.

[0034] This application does not specify the molar ratio of trifluoroethyl methacrylate and methoxy polyethylene glycol acrylate, or the mass ratio of initiator to electrolyte.

[0035] This application does not specify the number-average molecular weight of methoxy polyethylene glycol acrylate.

[0036] This application does not specify the specific type of initiator.

[0037] This application does not specify the exact source of trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, N,N-methylenebisacrylamide, and the initiator; any commercially available product or product prepared by conventional methods known to those skilled in the art is acceptable.

[0038] This application describes a gel electrolyte comprising a polymer backbone and an electrolyte filled within the polymer backbone. The polymer backbone is obtained by polymerizing a gel polymerization raw material system including trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, N,N-methylenebisacrylamide, and an initiator. By controlling the ratio of the total mass of the reactive monomers (trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, and N,N-methylenebisacrylamide) to the mass of the electrolyte, the gel electrolyte can exhibit high cycle performance and safety. This is primarily because when the total mass of the specific reactive monomers in the polymer backbone and the mass of the electrolyte are within the aforementioned range, the fluorinated and nitrided groups in the gel electrolyte can promote the formation of a stable CEI film. This not only enhances the electrolyte's antioxidant capacity but also effectively inhibits interfacial side reactions between the electrolyte and the cathode material, thereby improving the problem of transition metal ion dissolution in the cathode material and avoiding... The positive electrode material undergoes structural degradation, ensuring its structural stability and improving the battery's cycle stability. Simultaneously, at high temperatures, the gel electrolyte decomposes to produce hydrogen fluoride, which effectively captures oxygen and hydrogen free radicals in the electrolyte, thereby reducing the flame's combustion rate and disrupting the flame chain reaction. Furthermore, the gel electrolyte generates inert nitrogen gas during combustion, which dilutes flammable gases and effectively enhances the gel electrolyte's flame retardancy, resulting in higher safety for the gel battery. In addition, the gel electrolyte exhibits good wettability, and its -CF3 groups promote lithium-ion dissociation, while the COC groups coordinate with lithium ions, facilitating lithium-ion transport through chain segment movement. This enables effective lithium-ion conduction, maintaining high lithium-ion transport efficiency even at low temperatures of -20°C, effectively reducing interfacial impedance and further improving the battery's cycle performance.

[0039] Furthermore, since the gel electrolyte has high antioxidant properties, the gel electrolyte in this application can be adapted to high-voltage lithium-ion batteries, thereby improving the energy density of the battery.

[0040] In one specific embodiment, the molar ratio of methoxy polyethylene glycol acrylate to trifluoroethyl methacrylate is 1:(1-5). Within this range, methoxy polyethylene glycol acrylate and trifluoroethyl methacrylate can synergistically complement each other, better balancing ionic conductivity and electrochemical window. This not only further reduces lithium-ion migration resistance but also improves the oxidation resistance of the gel electrolyte, resulting in better battery cycle performance.

[0041] For example, the molar ratio of methoxy polyethylene glycol acrylate to trifluoroethyl methacrylate is 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5.

[0042] In one specific embodiment, the initiator includes azobisisobutyronitrile and / or azobisisoheptanenitrile. When the initiator includes both azobisisobutyronitrile and azobisisoheptanenitrile, this application does not specify the ratio between the two.

[0043] In one specific embodiment, the mass ratio of initiator to electrolyte is 1:(1000-10000). Within this range, the polymerization rate is suitable. On the one hand, it avoids an excessively fast polymerization rate, which would lead to the generation of bubbles; on the other hand, it avoids an excessively long reaction time due to a slow polymerization rate, which would not only reduce efficiency but also exacerbate side reactions and affect battery performance.

[0044] For example, the mass ratio of initiator to electrolyte is 1:1000, 1:2000, 1:3000, 1:4000, 1:5000, 1:6000, 1:7000, 1:8000, 1:9000 or 1:10000.

[0045] In one specific embodiment, the number-average molecular weight of methoxy polyethylene glycol acrylate is 480–1000. Within this range, it facilitates the diffusion of the electrolyte and the gel polymerization raw material system including methoxy polyethylene glycol acrylate within the battery cell, improving the gelation effect and thus further enhancing the battery's cycle performance.

[0046] For example, the number average molecular weight of methoxy polyethylene glycol acrylate is 480, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950 or 1000.

[0047] In one specific embodiment, the exothermic enthalpy of the gel electrolyte in the DSC test is no higher than 200 J / g. Specifically, the flame retardancy of the gel electrolyte can be further improved by controlling the total mass ratio of trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, and N,N-methylenebisacrylamide to the electrolyte, or the molar ratio of methoxy polyethylene glycol acrylate to trifluoroethyl methacrylate, or the mass ratio of the initiator to the electrolyte, or the number-average molecular weight of methoxy polyethylene glycol acrylate, or the reaction temperature, or the reaction time, so that the exothermic enthalpy of the gel electrolyte in the DSC test is no higher than 200 J / g.

[0048] Specifically, the exothermic enthalpy of the gel electrolyte in this application can be measured by a method including the following steps:

[0049] The prepared gel electrolyte was placed in a crucible and tested using a differential scanning calorimeter. The test temperature range was 30℃ to 300℃, and the heating rate was 10℃ / min. The DSC curve of the gel electrolyte was obtained, and the exothermic enthalpy was the peak area of ​​160 to 275℃ in the DSC curve.

[0050] A second aspect of this application provides a gel battery, which includes a gel electrolyte as described in the first aspect. Since the gel electrolyte includes a polymer backbone and an electrolyte filled within the polymer backbone; wherein the polymer backbone is obtained by polymerization of a gel polymerization raw material system including trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, N,N-methylenebisacrylamide, and an initiator, the gel electrolyte not only effectively improves the structural stability of the positive electrode material but also has good flame retardant and wettability properties, thereby enabling the battery including the gel electrolyte to have high cycle stability and safety performance.

[0051] In one specific embodiment, the gel battery is prepared by a method comprising the following processes:

[0052] A precursor solution is prepared by mixing raw materials including trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, and N,N-methylenebisacrylamide with an electrolyte. An initiator is then added to the precursor solution and injected into the battery. A gel electrolyte is generated through a polymerization reaction at a temperature of 45–75°C for 4–24 hours. After subsequent formation and capacity testing, a gel battery is obtained.

[0053] Specifically, raw materials including trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, and N,N-methylenebisacrylamide are dissolved in an electrolyte to obtain a homogeneous precursor solution. An initiator is then added to the precursor solution, and after dissolution, a mixed solution is obtained. This mixed solution is injected into a baked lithium-ion battery. After injection, the battery is allowed to stand at room temperature for a period of time before undergoing a polymerization reaction to generate a gel electrolyte. The reaction temperature is 45–75°C, and the reaction time is 4–24 hours. The lithium-ion battery containing the gel electrolyte is then subjected to formation treatment and capacity testing to obtain a gel battery.

[0054] For example, the reaction temperature is 45℃, 47℃, 49℃, 51℃, 53℃, 55℃, 57℃, 59℃, 61℃, 63℃, 65℃, 67℃, 69℃, 71℃, 73℃ or 75℃; the reaction time is 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h or 24h.

[0055] This application does not specify a particular settling time; for example, the settling time may be 12 to 24 hours. For example, the settling time may be 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, or 24 hours.

[0056] This application does not specifically limit the formation treatment and capacity separation treatment, which can be carried out by conventional formation treatment and capacity separation treatment methods in the art.

[0057] The gel battery prepared by the method including the above steps has a gel electrolyte with good flame retardant effect and better safety than electrolyte or conventional gel electrolyte, which can significantly improve the safety performance of the battery. At the same time, it can also improve the structural stability of the positive electrode material and ensure high ionic conductivity, so that the battery has high cycle stability.

[0058] In one specific embodiment, the mass percentage of N,N-methylenebisacrylamide in the precursor solution is 0.75% to 1.25%.

[0059] For example, the mass percentage content is 0.75%, 0.85%, 0.95%, 1.05%, 1.15%, or 1.25%.

[0060] In one specific embodiment, the gel battery further includes a positive electrode active material, which includes a ternary positive electrode material; the nickel content of the ternary positive electrode material is not less than 60%. In this case, while ensuring high safety performance, the energy density of the battery can be further improved. Simultaneously, the gel electrolyte in this gel battery can effectively suppress the dissolution of transition metal ions in the positive electrode material, ensuring the structural stability of the positive electrode material. Therefore, when the nickel content of the ternary positive electrode material is not less than 60%, the gel battery can simultaneously possess high safety performance, cycle performance, and energy density.

[0061] In this application, “nickel content” refers to the molar content of nickel as a percentage of the transition metal elements.

[0062] Example

[0063] The gel electrolyte of this application is described in detail below through specific embodiments. Various tests and evaluations were performed according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are mass standards.

[0064] Example 1

[0065] 1) The reactant monomers methoxy polyethylene glycol acrylate (number average molecular weight 480), trifluoroethyl methacrylate, and crosslinking agent N,N-methylenebisacrylamide were added to the electrolyte and mixed thoroughly to obtain a precursor solution. The electrolyte, by mass percentage, comprised: lithium hexafluorophosphate (LiPF6) 12.5 wt%, ethylene carbonate (EC) 7.75 wt%, ethyl methyl carbonate (EMC) 38.75 wt%, propylene carbonate (PC) 7.75 wt%, and fluoroethylene carbonate (FE). C) 10wt%, diethyl carbonate (DEC) 23.25wt%; the precursor solution contains, by mass percentage: 6.67wt% methoxy polyethylene glycol acrylate, 2.33wt% trifluoroethyl methacrylate, 1wt% N,N-methylenebisacrylamide, and 90wt% electrolyte, with a molar ratio of methoxy polyethylene glycol acrylate to trifluoroethyl methacrylate of 1:1; then, azobisisobutyronitrile (AIB) and initiator are added to the precursor solution, with a mass ratio of initiator to electrolyte of 1:4000;

[0066] 2) The precursor solution including the initiator was injected into a pre-baked lithium-ion battery (capacity 1.4Ah), wherein the negative electrode active material was a silicon-oxygen material (Zichen), and the positive electrode active material was a ternary nickel-cobalt-manganese material LiNi. 0.6 Co 0.1 Mn 0.3 O2 (NCM613, Zhenhua), the separator is a PE ceramic separator (Xingyuan material); after injection, it is left to stand at room temperature (25℃) for 6 hours, and then pressure curing is performed. The pressure curing pressure is 0.3MPa, the reaction temperature is 60℃, and the reaction time is 16 hours. After the reaction, it is left to stand at room temperature for 24 hours, and then pressure heating formation treatment is performed. The pressure is 3MPa, the temperature is 45℃, the formation current is 0.1C, and the formation time is 390 minutes. The formed battery is then aged at 45℃, 0.3MPa, and for 16 hours. Then, venting and secondary sealing are performed for 5 seconds, and the venting vacuum degree is 90-95Pa to complete the battery encapsulation. The battery is then capacity tested with currents of 0.1C, 0.3C, 0.5C, and 1C to obtain the gel battery of this embodiment.

[0067] Example 2

[0068] The preparation method of the gel battery in this embodiment is basically the same as that in Example 1. The difference is that in step 1), the mass percentage of methoxy polyethylene glycol acrylate in the precursor solution is adjusted to 3.75 wt%, and the mass percentage of trifluoroethyl methacrylate is adjusted to 5.25 wt%, so the molar ratio of methoxy polyethylene glycol acrylate to trifluoroethyl methacrylate is 1:4.

[0069] Example 3

[0070] The preparation method of the gel battery in this embodiment is basically the same as that in Example 1. The difference is that in step 1), the mass percentage of methoxy polyethylene glycol acrylate in the precursor solution is adjusted to 3.85 wt%, the mass percentage of trifluoroethyl methacrylate is adjusted to 5.4 wt%, the mass percentage of N,N-methylenebisacrylamide is adjusted to 0.75 wt%, and the molar ratio of methoxy polyethylene glycol acrylate to trifluoroethyl methacrylate is 1:4.

[0071] Example 4

[0072] The preparation method of the gel battery in this embodiment is basically the same as that in Example 1. The difference is that in step 1), the mass percentage of methoxy polyethylene glycol acrylate in the precursor solution is adjusted to 3.64 wt%, the mass percentage of trifluoroethyl methacrylate is adjusted to 5.11 wt%, the mass percentage of N,N-methylenebisacrylamide is adjusted to 1.25 wt%, and the molar ratio of methoxy polyethylene glycol acrylate to trifluoroethyl methacrylate is 1:4.

[0073] Example 5

[0074] The preparation method of the gel battery in this embodiment is basically the same as that in Example 1. The difference is that in step 1), the mass percentage of methoxy polyethylene glycol acrylate in the precursor solution is adjusted to 3.27 wt%, the mass percentage of trifluoroethyl methacrylate is adjusted to 5.73 wt%, and the molar ratio of methoxy polyethylene glycol acrylate to trifluoroethyl methacrylate is 1:5.

[0075] Example 6

[0076] The preparation method of the gel battery in this embodiment is basically the same as that in Example 1. The difference is that in step 1), the mass percentage of methoxy polyethylene glycol acrylate in the precursor solution is adjusted to 6.26 wt%, the mass percentage of trifluoroethyl methacrylate is adjusted to 2.74 wt%, and the molar ratio of methoxy polyethylene glycol acrylate to trifluoroethyl methacrylate is 1:1.25.

[0077] Example 7

[0078] The preparation method of the gel battery in this embodiment is basically the same as that in Example 2, except that in step 1), the mass ratio of initiator to electrolyte is adjusted to 1:1000.

[0079] Example 8

[0080] The preparation method of the gel battery in this embodiment is basically the same as that in Example 2, except that in step 1), the mass ratio of initiator to electrolyte is adjusted to 1:10000.

[0081] Example 9

[0082] The preparation method of the gel battery in this embodiment is basically the same as that in Example 2, except that in step 1), the mass ratio of initiator to electrolyte is adjusted to 1:5000.

[0083] Example 10

[0084] The preparation method of the gel battery in this embodiment is basically the same as that in Example 2. The difference is that in step 1), the number average molecular weight of methoxy polyethylene glycol acrylate is adjusted to 1000, the mass percentage of methoxy polyethylene glycol acrylate in the precursor solution is adjusted to 5.38 wt%, and the mass percentage of trifluoroethyl methacrylate is adjusted to 3.62 wt%.

[0085] Example 11

[0086] The preparation method of the gel battery in this embodiment is basically the same as that in Example 2, except that in step 2), the reaction time of pressure curing is adjusted to 24h.

[0087] Example 12

[0088] The preparation method of the gel battery in this embodiment is basically the same as that in Example 2. The difference is that in step 2), the reaction temperature of pressure curing is adjusted to 45°C and the reaction time is adjusted to 14h.

[0089] Example 13

[0090] The preparation method of the gel battery in this embodiment is basically the same as that in Example 2. The difference is that in step 2), the reaction temperature of the pressure curing is adjusted to 75°C and the reaction time is adjusted to 4h.

[0091] Example 14

[0092] The preparation method of the gel battery in this embodiment is basically the same as that in Example 2, except that in step 1), the initiator azobisisobutyronitrile is replaced with azobisisoheptanenitrile.

[0093] Example 15

[0094] The preparation method of the gel battery in this embodiment is basically the same as that in Example 2. The difference is that in step 1), the mass percentage of methoxy polyethylene glycol acrylate in the precursor solution is adjusted to 2.37 wt%, and the mass percentage of trifluoroethyl methacrylate is adjusted to 6.63 wt%, so the molar ratio of methoxy polyethylene glycol acrylate to trifluoroethyl methacrylate is 1:8.

[0095] Example 16

[0096] The preparation method of the gel battery in this embodiment is basically the same as that in Example 2. The difference is that in step 1), the mass percentage of methoxy polyethylene glycol acrylate in the precursor solution is adjusted to 3.54 wt%, the mass percentage of trifluoroethyl methacrylate is adjusted to 4.96 wt%, and the mass percentage of N,N-methylenebisacrylamide is adjusted to 1.5 wt%.

[0097] Example 17

[0098] The preparation method of the gel battery in this embodiment is basically the same as that in Example 2, except that in step 1), the mass ratio of the initiator to the electrolyte is adjusted to 1:500.

[0099] Example 18

[0100] The preparation method of the gel battery in this embodiment is basically the same as that in Example 2. The difference is that in step 2), the number average molecular weight of methoxy polyethylene glycol acrylate is adjusted to 2000, the mass percentage of methoxy polyethylene glycol acrylate in the precursor solution is adjusted to 6.74 wt%, and the mass percentage of trifluoroethyl methacrylate is adjusted to 2.26 wt%.

[0101] Example 19

[0102] The preparation method of the gel battery in this embodiment is basically the same as that in Example 2. The difference is that in step 2), the mass percentage of methoxy polyethylene glycol acrylate in the precursor solution is adjusted to 2.71 wt%, and the mass percentage of trifluoroethyl methacrylate is adjusted to 3.79 wt%. Then the mass ratio of the total mass of the reactant monomers to the mass of the electrolyte is 7.5:92.5.

[0103] Example 20

[0104] The preparation method of the gel battery in this embodiment is basically the same as that in Example 2. The difference is that in step 2), the mass percentage of methoxy polyethylene glycol acrylate in the precursor solution is adjusted to 4.59 wt%, and the mass percentage of trifluoroethyl methacrylate is adjusted to 6.41 wt%. Then the mass ratio of the total mass of the reactant monomers to the mass of the electrolyte is 12:88.

[0105] Example 21

[0106] The preparation method of the gel battery in this embodiment is basically the same as that in Example 2. The difference is that in step 2), the mass percentage of methoxy polyethylene glycol acrylate in the precursor solution is adjusted to 1.17 wt%, and the mass percentage of trifluoroethyl methacrylate is adjusted to 0.83 wt%. Then the mass ratio of the total mass of the reactant monomers to the mass of the electrolyte is 3:97.

[0107] Comparative Example 1

[0108] A conventional electrolyte was injected into a pre-baked lithium-ion battery. The electrolyte, by weight percentage, consisted of 12.5 wt% lithium hexafluorophosphate (LiPF6), 7.75 wt% ethylene carbonate (EC), 38.75 wt% ethyl methyl carbonate (EMC), 7.75 wt% propylene carbonate (PC), 10 wt% fluoroethylene carbonate (FEC), and 23.25 wt% diethyl carbonate (DEC). The negative electrode active material was a silicon-oxygen material (Zichen), and the positive electrode active material was a ternary nickel-cobalt-manganese material LiNi0.6Co0.1Mn0.3O2 (NCM613, Zhenhua). The separator is a PE ceramic separator (Xingyuan material). After liquid injection, the battery is left to stand at room temperature (25℃) for 24 hours, and then subjected to pressurized heating formation at a pressure of 3MPa, a temperature of 45℃, a formation current of 0.1C, and a formation time of 390min. The formed battery is then subjected to aging treatment at a temperature of 45℃, a pressure of 0.3MPa, and a time of 16h. Subsequently, venting and secondary sealing are performed for 5s, with a venting vacuum degree of 90-95Pa, to complete battery encapsulation. The battery is then subjected to capacity testing at currents of 0.1C, 0.3C, 0.5C, and 1C to obtain the comparative example battery.

[0109] Comparative Example 2

[0110] The preparation method of the battery in this comparative example is basically the same as that in Example 2, except that the precursor solution does not include methoxy polyethylene glycol acrylate, and correspondingly, the mass percentage of trifluoroethyl methacrylate in the precursor solution becomes 9 wt%.

[0111] Comparative Example 3

[0112] The preparation method of the battery in this comparative example is basically the same as that in Example 2. The difference is that the precursor solution does not include trifluoroethyl methacrylate, so the mass percentage of methoxy polyethylene glycol acrylate in the precursor solution becomes 9 wt%. Gel electrolyte cannot be obtained in this comparative example.

[0113] Comparative Example 4

[0114] The preparation method of the battery in this comparative example is basically the same as that in Example 2, except that N,N-methylenebisacrylamide is not included in the precursor solution, and correspondingly, the mass percentage of the electrolyte in the precursor solution becomes 91 wt%; a gel electrolyte cannot be obtained in this comparative example.

[0115] Comparative Example 5

[0116] The preparation method of the battery in this comparative example is basically the same as that in Example 2. The difference is that in step 2), the mass percentage of methoxy polyethylene glycol acrylate in the precursor solution is adjusted to 5.83 wt%, and the mass percentage of trifluoroethyl methacrylate is adjusted to 8.17 wt%. Then the mass ratio of the total mass of the reactants to the mass of the electrolyte is 15:85.

[0117] The basic parameters are shown in Table 1.

[0118] Table 1

[0119] Note: In Table 1, " / " indicates that the corresponding preparation parameters or substances do not exist.

[0120] Test case

[0121] 1. The storage modulus, ionic conductivity, electrochemical window, thermal stability, and cycling performance of the gel electrolytes in the above examples and comparative examples were tested, including the following steps:

[0122] 1) Energy storage modulus

[0123] The precursor solutions from the above examples and comparative examples were added to the corresponding mass ratios of initiators, and then reacted at the corresponding temperatures and times. After the reaction was completed, a gel electrolyte was obtained. At 25°C, the gel electrolyte was placed on an aluminum plate, and strain scanning was performed at a constant frequency of 1 rad / s, with a scanning range of 1–100%. The average storage modulus within the linear viscoelastic range was taken as the storage modulus of the corresponding gel electrolyte to evaluate the mechanical strength of the gel electrolyte. The test results are shown in Table 2 and Figure 1.

[0124] Figure 1 shows the viscoelastic curves of the gel electrolytes in Examples 1-3. As can be seen from Figure 1, the storage modulus (G') of the gel electrolytes in Examples 1-3 remains at a high level (greater than 3000 Pa) within the strain range of 1-10%, indicating that the gel electrolyte of this application has good mechanical strength, which is beneficial to suppressing the volume expansion of the silicon-carbon anode during cycling.

[0125] 2) Ionic conductivity

[0126] The precursor solutions from the above examples and comparative examples were added to the corresponding mass ratios of initiators, and the reactions were carried out at the corresponding temperatures and times. After the reaction was completed, a gel electrolyte was obtained. The gel electrolyte was placed in a 25 mL colorimetric tube, and the tube was sealed after inserting a conductivity electrode. The ionic conductivity of the gel electrolyte was tested using a conductivity meter at room temperature (25 °C) and low temperature (-20 °C). The test results are shown in Table 2 and Figure 2.

[0127] Figure 2 shows the relationship between the ionic conductivity and temperature of the gel electrolytes in Examples 1-3. As can be seen from Figure 2, the ionic conductivity of the gel electrolytes in Examples 1-3 measured at 25℃ were 5.3 mS / cm, 5.4 mS / cm, and 5.4 mS / cm, respectively; even at -20℃, they still exhibited high ionic conductivity, at 1.4 mS / cm, 1.5 mS / cm, and 1.5 mS / cm, respectively. Furthermore, Figure 2 shows that the relationship between the lithium-ion conductivity of the gel electrolytes and temperature conforms to a typical Arrhenius linear equation, exhibiting a linear relationship.

[0128] 3) Electrochemical window

[0129] The precursor solutions from the above examples and comparative examples were added to initiators at corresponding mass ratios and placed in a three-electrode electrolytic cell. The reactions were carried out at the appropriate temperatures and times, resulting in a gel electrolyte. Linear sweep voltammetry (LSV) was performed using a platinum electrode as the working electrode, lithium metal as the counter electrode, and lithium metal as the reference electrode. The initial voltage was the open-circuit voltage, the scan rate was 0.1 mV / s, and the termination voltage was 7 V. The test results are shown in Table 2 and Figure 3.

[0130] Figure 3 shows the LSV curves of the gel batteries in Examples 1-3 and Comparative Example 1. As can be seen from Figure 3, the gel electrolytes in Examples 1-3 have good oxidation resistance before 4.8V, which shows that the gel electrolyte in this application can be adapted to higher voltage systems.

[0131] 4) Thermal stability

[0132] The precursor solutions from the above examples and comparative examples were added to initiators at corresponding mass ratios, and the reactions were carried out at corresponding reaction temperatures and times. After the reaction, a gel electrolyte was obtained. The gel electrolyte was placed in a crucible and tested using a scanning calorimeter (SCCAD). The test temperature range was 30℃ to 300℃, and the heating rate was 10℃ / min. The DSC curve of the gel electrolyte was obtained, and the exothermic enthalpy (J / g) was the peak area of ​​the curve from 160℃ to 275℃. The test results are shown in Table 2 and Figure 4.

[0133] Figure 4 shows the DSC curves of the gel electrolytes in Examples 1-3 and Comparative Example 1. As can be seen from Figure 4, the gel electrolytes in Examples 1-3 have a smaller exothermic enthalpy at high temperatures compared to the liquid electrolyte in Comparative Example 1, indicating that the gel electrolyte of this application has higher safety.

[0134] 5) Cyclic performance

[0135] At room temperature of 25°C, the batteries in the above examples and comparative examples were charged to 4.35V with a constant current and constant voltage of 1C and a cutoff current of 0.07A. After resting for 5 minutes, they were discharged to 2.75V with a constant current of 1C and rested for 5 minutes. The initial discharge capacity was recorded as C0. The batteries were cycled 100 times according to the aforementioned charge and discharge mechanism, and the discharge capacity after the cycle was recorded as C1. The cycle capacity retention rate of the battery (%) = (C1 / C0) × 100%. The calculation results are shown in Table 2 and Figure 5.

[0136] Figure 5 shows the relationship between battery capacity and cycle number in Examples 1-3 and Comparative Example 1. As can be seen from Figure 5, the batteries in Examples 1-3 have a higher capacity retention rate than those in Comparative Example 1.

[0137] 2. The gel electrolyte and electrolyte solution in the above embodiments and comparative examples were placed in a container and ignited with an igniter to evaluate the flame retardant effect. The test results are shown in Table 2 and Figures 6 and 7.

[0138] Figure 6 shows photographs of the gel electrolyte in Example 1 before and after ignition, and Figure 7 shows photographs of the liquid electrolyte in Comparative Example 1 before and after ignition. In Figure 6, the left image shows the state of the gel electrolyte when ignited, and the right image shows the state after the flame automatically extinguishes itself immediately upon removal of the igniter. During combustion, the gel electrolyte in Example 1 automatically extinguishes itself after ignition and can extinguish itself automatically after multiple ignitions, demonstrating good flame retardancy. In Figure 7, the left image shows the state of the liquid electrolyte when ignited, and the right image shows the state of the liquid electrolyte after 10 seconds of combustion. The liquid electrolyte in Comparative Example 1 continues to burn within 10 seconds after ignition. Therefore, it can be seen that the gel electrolyte of this application has high safety performance.

[0139] Table 2

[0140] Table 2 shows that, compared to Comparative Examples 1-5, the batteries in Examples 1-21 exhibit higher overall performance. Specifically, the gel electrolyte in Example 2 achieves an ionic conductivity of 5.4 mS / cm at room temperature (25°C), and even at low temperatures, it maintains a good ionic conductivity of 1.5 mS / cm. Furthermore, due to its high oxidation resistance, this gel electrolyte can also be used in high-voltage battery systems, with an electrochemical window of up to 5.7 V. The gel electrolyte also possesses high mechanical strength and thermal stability, with a storage modulus of 14733 Pa and an exothermic enthalpy of only 173.2 J / g. The flame extinguishes immediately upon combustion, indicating that the gel electrolyte also exhibits high flame retardant properties, effectively improving battery safety. Finally, the battery incorporating this gel electrolyte also demonstrates high cycle performance, with a cycle capacity retention rate of 97.96%. Therefore, the gel electrolyte in this application can effectively improve the cycle performance and safety performance of batteries.

[0141] Finally, it should be noted that other embodiments of the invention will readily conceive of by those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A gel electrolyte, wherein, The gel electrolyte comprises a polymer backbone and an electrolyte filled in the polymer backbone; The polymer backbone is obtained by polymerization of a gel polymerization raw material system, which includes trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, N,N-methylenebisacrylamide and an initiator; wherein the total mass ratio of trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate and N,N-methylenebisacrylamide to the mass ratio of the electrolyte is 3:97 to 12:

88.

2. The gel electrolyte according to claim 1, wherein, The molar ratio of the methoxy polyethylene glycol acrylate to the trifluoroethyl methacrylate is 1:(1-5).

3. The gel electrolyte according to claim 1 or 2, wherein, Based on the total mass of the trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, N,N-methylenebisacrylamide, and electrolyte, the mass percentage of N,N-methylenebisacrylamide is 0.75% to 1.25%.

4. The gel electrolyte according to any one of claims 1-3, wherein, The initiator includes at least one of azobisisobutyronitrile and azobisisoheptanenitrile.

5. The gel electrolyte according to any one of claims 1-4, wherein, The mass ratio of the initiator to the electrolyte is 1:(1000~10000).

6. The gel electrolyte according to any one of claims 1-5, wherein, The number-average molecular weight of the methoxy polyethylene glycol acrylate is 480–1000.

7. The gel electrolyte according to any one of claims 1-6, wherein, The exothermic enthalpy of the gel electrolyte in the DSC test is not higher than 200 J / g.

8. A gel battery, wherein, The gel battery includes the gel electrolyte according to any one of claims 1-7.

9. The gel battery according to claim 8, wherein, The gel battery is prepared by a method including the following process: A precursor solution is prepared by mixing raw materials including trifluoroethyl methacrylate, methoxy polyethylene glycol acrylate, and N,N-methylenebisacrylamide with an electrolyte. An initiator is then added to the precursor solution and injected into the battery. A gel electrolyte is generated through a polymerization reaction at a temperature of 45–75°C for 4–24 hours. After subsequent formation and capacity testing, the gel battery is obtained.

10. The gel battery according to claim 9, wherein, The N,N-methylenebisacrylamide in the precursor solution has a mass percentage of 0.75% to 1.25%.

11. The gel battery according to any one of claims 8-10, wherein, The gel battery also includes a positive electrode active material, which includes a ternary positive electrode material. The nickel content of the ternary cathode material is not less than 60%.

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