Solid-state composite electrolytes, their preparation methods, and batteries

Abstract

This invention relates to the field of new energy batteries, specifically to a solid-state composite electrolyte, its preparation method, and a battery. The solid-state composite electrolyte includes a lithium replenishing agent and a polymer electrolyte coated on the surface of the lithium replenishing agent. The polymer electrolyte comprises a lithium salt and a solid solvent polymer, with the lithium salt dissolved in the solid solvent polymer. The solid-state composite electrolyte of this invention encapsulates the lithium replenishing agent between the polymer electrolyte layers, preventing contact with air or other external sources. This prevents the lithium replenishing agent from releasing lithium upon contact with air, effectively preventing lithium release and improving lithium replenishment efficiency.

Description

Technical Field

[0001] This invention relates to the field of new energy batteries, specifically to a solid composite electrolyte, its preparation method, and a battery. Background Technology

[0002] The capacity decay problem of lithium-ion batteries remains an unresolved issue in the development of lithium-ion batteries. Lithium-ion batteries are highly susceptible to irreversible capacity loss under electrical, thermal, and mechanical abuse. Low initial anode efficiency is a major source of overall battery capacity loss. Solutions to the capacity loss problem include optimizing the battery's electrochemical system to suppress capacity decay during use, but these are only auxiliary improvements and do not fundamentally address or prevent capacity loss. Another approach is to replenish lithium on the surface of the positive and negative electrode materials to compensate for the irreversible lithium loss during the initial lithium insertion process at the negative electrode. However, both positive electrode lithium replenishment agents and negative electrode pre-lithiation lead to a significant increase in cost and manufacturing difficulty. Furthermore, using lithium replenishment agents at the positive electrode reduces the cell's volumetric energy density.

[0003] Studies have shown that incorporating lithium replenishing agents within the separator can effectively mitigate lithium loss caused by SEI film formation during the initial lithium insertion process at the negative electrode, as well as the consumption of active lithium by subsequent side reactions. Therefore, it is generally believed that improving and preventing irreversible lithium loss in lithium-ion batteries through separators is a promising approach. Lithium replenishment can be achieved through coating and multi-layering of the separator, which can improve irreversible lithium loss. However, most separators, including currently commercially available PE, PP, and PE / PP / PE separators, do not offer feasible implementation options, necessitating a re-evaluation and restructuring of the separator structure. If the separator is linked to a polymer solid electrolyte, the lithium replenishing agent can act as a Lewis acid to promote the polymerization reaction of polymer monomers. After electrolyte injection, the polymer expands and releases the lithium replenishing agent. Furthermore, the material itself, after lithium release, acts as a good inert filler, improving the local crystallization state of the polymer, promoting lithium salt dissolution, and enhancing Li... + The polymerization of segmental polar groups helps generate free volume, enhances ionic conductivity, and compensates for the initial lithium insertion process of the negative electrode, thereby increasing the initial efficiency of the anode.

[0004] To address irreversible lithium loss, lithium replenishing agents are added during the positive electrode homogenization process. However, the lithium replenishing agent releases lithium due to contact with the external environment, reducing the lithium replenishment effect. Furthermore, the lithium replenishing agent currently leaves inactive residues after lithium release at the positive electrode, affecting the cell's cycle performance and increasing internal resistance. Replenishing lithium on the negative electrode side using lithium foil or lithium powder is expensive and uncontrollable. Using pre-lithiated negative electrodes also presents the same problems. Summary of the Invention

[0005] In view of this, the present invention aims to provide a solid composite electrolyte, its preparation method and battery, to solve the problems in the prior art where the addition of lithium replenishing agent during the positive electrode homogenization process causes lithium release due to contact with the external environment, reducing the lithium replenishment effect; lithium replenishment on the negative electrode side using lithium foil or lithium powder is expensive and uncontrollable; the use of pre-lithiated negative electrodes increases the manufacturing difficulty and reduces the yield of finished products; and the traditional separator material encapsulates the lithium replenishing agent, which can prevent the lithium replenishing agent from being released and cause the lithium replenishing agent to fail.

[0006] To solve the above-mentioned technical problems, this application is implemented as follows:

[0007] A first aspect of the present invention provides a solid composite electrolyte, the solid composite electrolyte comprising a lithium replenishing agent and a polymer electrolyte coated on the surface of the lithium replenishing agent;

[0008] The polymer electrolyte comprises a solid solvent polymer and a lithium salt, wherein the lithium salt is dissolved in the solid solvent polymer.

[0009] Optionally, the lithium replenishing agent, the lithium salt, and the solid solvent polymer contained in the solid composite electrolyte satisfy the following relationship: 0.6≤m1 / (m1+m2+m3)≤0.9, where m1 represents the mass of the solid solvent polymer, m2 represents the mass of the lithium replenishing agent, and m3 represents the mass of the lithium salt; preferably, the lithium replenishing agent, the lithium salt, and the solid solvent polymer contained in the solid composite electrolyte satisfy the following relationship: 0.75≤m1 / (m1+m2+m3)≤0.85.

[0010] Optionally, the mass ratio of the lithium salt to the lithium replenishing agent is 1:0.1 to 5, preferably 1:0.5 to 1.5.

[0011] Optionally, the lithium supplement includes a lithium oxide; optionally, the lithium oxide is selected from at least one of Li5FeO4, LiNiO2, Li2NiO2, Li2O, Li2O2, Li2MnO3, Li6MnO4, Li6CoO4 and Li5ReO6; and / or, the lithium salt is selected from at least one of LiTFSI, LiPF6, LiBF4, LiBOB, LiFSI and LiODFB; and / or, the solid solvent polymer is selected from at least one of poly(1,3-dioxolane), polyethylene oxide, polyvinyl alcohol, polymethyl methacrylate and polyvinylidene fluoride.

[0012] Optionally, the solid composite electrolyte further includes glass fibers dispersed in the solid solvent polymer; optionally, based on the total mass of the solid composite electrolyte, the content of the glass fibers is 0.05 to 10 wt%, preferably 1 to 5 wt%.

[0013] A second aspect of the present invention provides a method for preparing a solid composite electrolyte, the method comprising the following steps:

[0014] S1. The solid solvent polymer monomer and lithium supplementer are subjected to a first mixing treatment to obtain a first slurry;

[0015] S2. The first slurry and lithium salt are subjected to a second mixing process to obtain a second slurry;

[0016] S3. The second slurry is subjected to heat treatment and drying treatment.

[0017] Optionally, the viscosity of the first slurry is 500-10000 Cp, preferably 1000-3000 Cp; and / or, the solid content of the first slurry is 10-50%, preferably 15-30%; and / or, the viscosity of the second slurry is 50-20000 Cp, preferably 50-200 Cp; and / or, the solid content of the second slurry is 1-20%, preferably 5-10%; and / or, the solid solvent polymer monomer is selected from at least one of 1,3-epoxypentane, ethylene oxide, vinyl acetate, methyl methacrylate, and 1,1-difluoroethylene.

[0018] Optionally, in step S1, the conditions for the first mixing treatment include: a temperature of 40–60°C, a time of 10–120 min, and a stirring speed of 800–1500 rpm; and / or, in step S2, the conditions for the second mixing treatment include: a temperature of 40–60°C, a time of 30–60 min, and a stirring speed of 600–900 rpm; and / or, in step S3, the conditions for the heating treatment include: a temperature of 40–60°C, a time of 30–90 min; and / or, the conditions for the drying treatment include: a temperature of 40–60°C, a time of 60–150 min.

[0019] Optionally, the preparation method further includes: adding glass fibers to the second mixing process to obtain a second slurry containing glass fibers.

[0020] A third aspect of the present invention provides a battery comprising an electrode assembly and an electrolyte, wherein the electrode assembly comprises a positive electrode, a negative electrode and a solid electrolyte layer, and the solid electrolyte layer is the solid composite electrolyte described above or a solid composite electrolyte prepared according to the preparation method described above.

[0021] The beneficial technical effects of the present invention through the above technical solution are as follows:

[0022] (1) The solid composite electrolyte of the present invention encapsulates the lithium replenishing agent between the polymer electrolyte layers, preventing it from contacting the air or other external environments. This prevents the lithium replenishing agent from releasing lithium upon contact with air, effectively preventing lithium release and improving lithium replenishment efficiency. The present invention places the lithium replenishing agent between the polymer solid electrolyte layers before electrolyte injection. During the first charging process, an SEI film is formed on the negative electrode surface first. The redox potential of the lithium replenishing agent is lower than that of the positive electrode material, causing lithium ions to be released first during charging, thus achieving orderly lithium release.

[0023] (2) In the solid composite electrolyte of the present invention, after the lithium replenishment agent releases lithium, the inactive substances remain in the polymer system as inert fillers, which can increase the proportion of amorphous polymer and enhance the Li-1444 lithium content. + The polymerization of segmental polar groups facilitates the generation of free volume and enhances ionic conductivity.

[0024] (3) The solid composite electrolyte of the present invention can reduce the amount of electrolyte used, the solid electrolyte layer is not prone to high-temperature deformation, and its stability is significantly improved compared with the separator. The polymer solid electrolyte layer has a high Young's modulus, and lithium dendrites cannot pierce it, which can effectively reduce the probability of thermal runaway and the peak temperature during thermal runaway. The solvent in the electrolyte wets the solid composite electrolyte, which can enhance the flexibility of the solid electrolyte layer, improve the "solid-solid contact" problem between the solid electrolyte layer and the positive and negative electrodes, and accelerate the electrochemical reaction rate.

[0025] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0026] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0027] Figure 1 The image shown is a SEM image of the solid composite electrolyte prepared in Example 1. Detailed Implementation

[0028] This invention discloses a solid-state composite electrolyte, its preparation method, and a battery. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0029] In the description of this invention, the list of items connected by the term "at least one of" or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0030] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0031] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0032] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0033] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0034] To address the problems in existing technologies, such as lithium release due to contact with the external environment when adding lithium supplementing agent during the positive electrode homogenization process, reducing the lithium supplementation effect; the high cost and uncontrollable cost of lithium foil or lithium powder for lithium supplementation on the negative electrode side; increased manufacturing difficulty and reduced product yield when using pre-lithiated negative electrodes; and the inability of traditional separator materials to encapsulate the lithium supplementing agent, leading to its failure, this invention adopts the following technical solution:

[0035] A first aspect of the present invention provides a solid composite electrolyte, the solid composite electrolyte comprising a lithium replenishing agent and a polymer electrolyte coated on the surface of the lithium replenishing agent;

[0036] The polymer electrolyte comprises a solid solvent polymer and a lithium salt, wherein the lithium salt is dissolved in the solid solvent polymer.

[0037] The solid-state composite electrolyte of this invention encapsulates the lithium replenishing agent within the polymer electrolyte layers, preventing contact with air and other external elements. This prevents the lithium replenishing agent from releasing lithium upon contact with air, effectively controlling lithium release and improving lithium replenishment efficiency. By placing the lithium replenishing agent between the polymer solid electrolyte layers before electrolyte injection, an SEI film is formed on the negative electrode surface during the initial charging process. Since the redox potential of the lithium replenishing agent is lower than that of the positive electrode material, it releases lithium ions first during charging, thus enabling orderly lithium release.

[0038] The solid-state composite electrolyte of this invention can also reduce the amount of electrolyte used. The solid electrolyte layer containing the solid-state composite electrolyte of this invention is less prone to high-temperature deformation, and its stability is significantly improved compared to the separator. The polymer solid electrolyte layer of this invention has a high Young's modulus, preventing lithium dendrites from piercing it, which can effectively reduce the probability of thermal runaway and the peak temperature during thermal runaway. In this invention, the solvent in the electrolyte, while wetting the solid-state composite electrolyte, can enhance the flexibility of the solid electrolyte layer, improve the "solid-solid contact" problem between the solid electrolyte layer and the positive and negative electrodes, and accelerate the electrochemical reaction rate.

[0039] According to the present invention, the solid composite electrolyte requires a suitable solid solvent polymer to ensure that the lithium salt is dissolved without affecting the migration and ionic conductivity of lithium ions. Exemplarily, the lithium supplementer, lithium salt, and solid solvent polymer contained in the solid composite electrolyte can satisfy the relationship: 0.6 ≤ m1 / (m1+m2+m3) ≤ 0.9, where m1 represents the mass of the solid solvent polymer, m2 represents the mass of the lithium supplementer, and m3 represents the mass of the lithium salt. In the present invention, if there is too much solid solvent polymer, it may lead to a decrease in lithium ion transport number and ionic conductivity; if there is too little solid solvent polymer, the lithium salt may not be completely dissolved. Preferably, the lithium supplementer, lithium salt, and solid solvent polymer contained in the solid composite electrolyte satisfy the relationship: 0.75 ≤ m1 / (m1+m2+m3) ≤ 0.85.

[0040] According to the present invention, a suitable ratio of lithium salt to lithium replenisher exhibits excellent ionic conductivity and ion mobility. The mass ratio of lithium salt to lithium replenisher can be from 1:0.1 to 5. Exemplarily, the mass ratio of lithium salt to lithium replenisher can be any value from 1:0.1, 1:0.5, 1:1, 1:2, 1:3, 1:4, and 1:5, or any value within the range of any pair of values ​​mentioned above. In the present invention, if the proportion of lithium salt is too high, it may lead to insolubility of the lithium salt, thereby reducing the overall ionic conductivity; if the proportion of lithium salt is too low, it may lead to low ionic conductivity, thus failing to meet the conditions for high-rate operation. Preferably, the mass ratio of lithium salt to lithium replenisher can be from 1:0.5 to 1.5.

[0041] According to the present invention, the lithium replenishing agent may include lithium-containing oxides; exemplaryly, the lithium-containing oxides may be selected from at least one of Li5FeO4, LiNiO2, Li2NiO2, Li2O, Li2O2, Li2MnO3, Li6MnO4, Li6CoO4, and Li5ReO6. In the solid-state composite electrolyte of the present invention, after the lithium replenishing agent has completed lithium release, inactive substances (e.g., iron oxide) can remain in the polymer system as inert fillers, which can increase the proportion of amorphous polymer and enhance the lithium content. + The polymerization of segmental polar groups facilitates the generation of free volume and enhances ionic conductivity.

[0042] For example, the lithium salt may be selected from at least one of LiTFSI, LiPF6, LiBF4, LiBOB, LiFSI and LiODFB.

[0043] For example, the solid solvent polymer may be selected from at least one of poly(1,3-dioxolane) (PDOL), polyethylene oxide (PEO), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), and polyvinylidene fluoride (PVDF).

[0044] In a preferred embodiment of the present invention, the lithium oxide is Li5FeO4, the lithium salt is LiTFSI, and the solid solvent polymer is poly(1,3-dioxolane). In this embodiment, the solid composite electrolyte can have excellent ionic conductivity and can improve the lithium ion transference number.

[0045] According to the present invention, the solid composite electrolyte may further include glass fibers dispersed in the solid solvent polymer. In this invention, the rigidity of the solid composite electrolyte can be maintained by adding glass fibers.

[0046] According to the present invention, a suitable amount of glass fiber can maintain the rigidity of the solid composite electrolyte while reducing the glass transition temperature of the polymer and increasing the solubility of the lithium salt. Based on the total mass of the solid composite electrolyte, the content of the glass fiber can be 0.05–10 wt%. Exemplarily, the content of the glass fiber can be any value from 0.05–10 wt%, 0.5 wt%, 1 wt%, 3 wt%, 5 wt%, 7 wt%, and 10 wt%, or any value within the range of any two of the above values. In this invention, if the amount of glass fiber added is too low, the rigidity of the solid composite electrolyte may not be guaranteed; if the amount of glass fiber added is too high, the polymer electrolyte may lose its toughness. Preferably, the content of the glass fiber can be 1–5 wt%.

[0047] A second aspect of the present invention provides a method for preparing a solid composite electrolyte, the method comprising the following steps:

[0048] S1. The solid solvent polymer monomer and lithium supplementer are subjected to a first mixing treatment to obtain a first slurry;

[0049] S2. The first slurry and lithium salt are subjected to a second mixing process to obtain a second slurry;

[0050] S3. The second slurry is subjected to heat treatment and drying treatment.

[0051] According to the present invention, a suitable viscosity of the first slurry can increase the production efficiency of the solid composite electrolyte. In this invention, the viscosity of the first slurry can be 500–10000 Cp. Exemplarily, the viscosity of the first slurry can be any value selected from 500 Cp, 1000 Cp, 3000 Cp, 5000 Cp, 7000 Cp, 9000 Cp, and 10000 Cp, or any value within the range formed by any pair of the above values. In this invention, if the viscosity of the first slurry is too high, a thin layer may not be achieved; if the viscosity of the first slurry is too low, it may affect the formation of the electrolyte layer. Preferably, the viscosity of the first slurry can be 1000–3000 Cp.

[0052] According to the present invention, a suitable solid content of the first slurry can control the film thickness while ensuring film formation. In this invention, the solid content of the first slurry can be 10-50%. Exemplarily, the solid content of the first slurry can be any value selected from 10%, 20%, 30%, 40%, and 50%, or any value within the range of any pair of values ​​mentioned above. In this invention, if the solid content of the first slurry is too high, film formation may be difficult; if the solid content of the first slurry is too low, film thickness may be difficult to control. Preferably, the solid content of the first slurry can be 15-30%.

[0053] According to the present invention, a suitable viscosity of the second slurry can improve the production efficiency of solid composite electrolytes. In this invention, the viscosity of the second slurry can be 50–20000 Cp. Exemplarily, the viscosity of the second slurry can be any value selected from 50 Cp, 100 Cp, 1000 Cp, 10000 Cp, 15000 Cp, and 20000 Cp, or any value within the range formed by any pair of the above values. In this invention, if the viscosity of the second slurry is too high, it may affect subsequent coating; if the viscosity of the second slurry is too low, it may waste solvent and thus increase costs. Preferably, the viscosity of the second slurry can be 50–200 Cp.

[0054] According to the present invention, a suitable solid content of the second slurry can control the film thickness while ensuring film formation. In this invention, the solid content of the second slurry can be 1% to 20%. Exemplarily, the solid content of the second slurry can be any value selected from 1%, 5%, 10%, 15%, and 20%, or any value within the range of any pair of values ​​mentioned above. In this invention, if the solid content of the second slurry is too high, film formation may be difficult; if the solid content of the second slurry is too low, film thickness may be difficult to control. Preferably, the solid content of the second slurry can be 5% to 10%.

[0055] According to the present invention, the solid solvent polymer monomer may be selected from at least one of 1,3-epoxypentane, ethylene oxide, vinyl acetate, methyl methacrylate and 1,1-difluoroethylene.

[0056] According to the present invention, in step S1, the conditions for the first mixing treatment may include: a temperature of 40 to 60°C, a time of 10 to 120 minutes, and a stirring speed of 800 to 1500 rpm.

[0057] According to the present invention, in step S2, the conditions for the second mixing treatment may include: a temperature of 40 to 60°C, a time of 30 to 60 minutes, and a stirring speed of 600 to 900 rpm.

[0058] According to the present invention, in step S3, the conditions for the heat treatment may include: a temperature of 40 to 60°C and a time of 30 to 90 min; and / or, the conditions for the drying treatment may include: a temperature of 40 to 60°C and a time of 60 to 150 min.

[0059] According to the present invention, the preparation method may further include: adding glass fibers to the second mixing process to obtain a second slurry containing glass fibers.

[0060] A third aspect of the present invention provides a battery comprising an electrode assembly and an electrolyte, wherein the electrode assembly comprises a positive electrode, a negative electrode and a solid electrolyte layer, and the solid electrolyte layer is the solid composite electrolyte described above or a solid composite electrolyte prepared according to the preparation method described above.

[0061] The electrolyte used in this invention is a conventional solvent in the art. For example, the electrolyte may be selected from at least one of ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), vinylene carbonate (VC), fluoroethylene carbonate (FEC), and propylene carbonate (PC).

[0062] The present invention will be further described in detail below through examples. All raw materials used in the examples are commercially available.

[0063] Example 1

[0064] (1) In a glove box under an argon atmosphere (O2 < 0.1 ppm, H2O < 0.1 ppm), 1,3-epoxypentane and LiTFSI were added for a first mixing treatment, wherein the mass ratio of 1,3-epoxypentane to LiTFSI was 1:0.125. The temperature of the first mixing treatment was 50℃, the time was 45 min, and the stirring speed was 100 rpm. After the mixture became clear, the first slurry was obtained. Li5FeO4 with a mass relative to 1,3-epoxypentane (12.5 wt%) was added to the first slurry for a second mixing treatment. The temperature of the second mixing treatment was 30℃, the time was 45 min, and the stirring speed was 120 rpm. After the solution became viscous, a glass fiber membrane with a diameter of 19 mm was placed in the bottle for full permeation. Then, the permeated membrane was removed and placed in a sealed glass jar to obtain the second slurry. The second slurry was heated at 45℃ for 12 hours for full polymerization. After the reaction was complete, the mixture was transferred to a 45°C vacuum drying oven and vacuum dried for 2 hours. The remaining small-molecule liquid was then removed by vacuum drying to obtain Li5FeO4-P-DOL, which is the solid-state composite electrolyte of this embodiment. In this embodiment, the mass relationship between the lithium supplement (Li5FeO4), lithium salt (LiTFSI), and solid solvent polymer (poly(1,3-dioxolane)) in the solid-state composite electrolyte is m1 / (m1+m2+m3) = 0.8 (where m1 represents the mass of the solid solvent polymer, m2 represents the mass of the lithium supplement, and m3 represents the mass of the lithium salt); the mass ratio of lithium salt to lithium supplement is 1:1. The SEM image of the solid-state composite electrolyte of this embodiment is shown below. Figure 1 ,pass Figure 1 It can be seen that the solid composite electrolyte is a mixed structure of DOL, LiTFSI, and Li5FeO4. Among them, Li5FeO4 has lithium release characteristics, which can compensate for the irreversible capacity loss caused by SEI formation during the initial lithium insertion of the anode material and enhance the energy density of the cell. The presence of DOL can suppress the decrease in lithium replenishment efficiency caused by lithium release from the lithium replenishing agent during use due to contact with the external environment. The solid composite electrolyte inhibits the vertical growth of lithium dendrites by utilizing the high shear modulus of the polymer.

[0065] (2) Lithium foil was used as the negative electrode active material and bonded to copper foil to obtain a negative electrode sheet with a size of 100mm × 55mm. A ternary material was used as the positive electrode active material, mixed with a conductive agent, binder, etc., coated onto aluminum foil, and then dried and pressed to form a positive electrode sheet with a size of 96mm × 51mm. The solid composite electrolyte of this embodiment was used as the separator. The electrolyte was 1M LiPF6 dissolved in a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) at a volume ratio of 1:1. The assembly process used a soft-pack stacking method, stacking the positive electrode sheet, separator, and negative electrode sheet in sequence to obtain the battery cell.

[0066] Example 2

[0067] The preparation method of the solid composite electrolyte in this embodiment is generally the same as in Example 1, except that the mass ratio of 1,3-epoxypentane to LiTFSI is 1:0.1875. In this embodiment, the mass relationship between the lithium supplement (Li5FeO4), lithium salt (LiTFSI), and solid solvent polymer (poly(1,3-dioxolane)) in the solid composite electrolyte is m1 / (m1+m2+m3) = 0.76 (where m1 represents the mass of the solid solvent polymer, m2 represents the mass of the lithium supplement, and m3 represents the mass of the lithium salt); the mass ratio of lithium salt to lithium supplement is 1:1.46.

[0068] The method for preparing the battery cell in this embodiment is the same as in Embodiment 1.

[0069] Example 3

[0070] The preparation method of the solid composite electrolyte in this embodiment is generally the same as in Example 1, except that the mass ratio of 1,3-epoxypentane to LiTFSI is 1:0.0625. In this embodiment, the mass relationship between the lithium supplement (Li5FeO4), lithium salt (LiTFSI), and solid solvent polymer (poly(1,3-dioxolane)) in the solid composite electrolyte is m1 / (m1+m2+m3) = 0.84 (where m1 represents the mass of the solid solvent polymer, m2 represents the mass of the lithium supplement, and m3 represents the mass of the lithium salt); the mass ratio of lithium salt to lithium supplement is 1:2.

[0071] The method for preparing the battery cell in this embodiment is the same as in Embodiment 1.

[0072] Example 4

[0073] The preparation method of the solid composite electrolyte in this embodiment is the same as that in Example 1, except that the mass of Li5FeO4 added is 20.8 wt% relative to the mass of 1,3-epoxypentane. In this embodiment, the mass relationship between the lithium supplement (Li5FeO4), lithium salt (LiTFSI), and solid solvent polymer (poly(1,3-dioxolane)) in the solid composite electrolyte is m1 / (m1+m2+m3) = 0.75 (where m1 represents the mass of the solid solvent polymer, m2 represents the mass of the lithium supplement, and m3 represents the mass of the lithium salt); the mass ratio of lithium salt to lithium supplement is 1:1.67.

[0074] The method for preparing the battery cell in this embodiment is the same as in Embodiment 1.

[0075] Example 5

[0076] The preparation method of the solid composite electrolyte in this embodiment is the same as that in Example 1, except that the mass of Li5FeO4 added is 4.2 wt% relative to the mass of 1,3-epoxypentane. In this embodiment, the mass relationship between the lithium supplement (Li5FeO4), lithium salt (LiTFSI), and solid solvent polymer (poly(1,3-dioxolane)) in the solid composite electrolyte is m1 / (m1+m2+m3) = 0.86 (where m1 represents the mass of the solid solvent polymer, m2 represents the mass of the lithium supplement, and m3 represents the mass of the lithium salt); the mass ratio of lithium salt to lithium supplement is 1:2.98.

[0077] The method for preparing the battery cell in this embodiment is the same as in Embodiment 1.

[0078] Example 6

[0079] The preparation method of the solid composite electrolyte in this embodiment is the same as that in Embodiment 1, except that glass fiber film is not added.

[0080] The method for preparing the battery cell in this embodiment is the same as in Embodiment 1.

[0081] Comparative Example 1

[0082] The preparation method of the solid composite electrolyte in this comparative example is the same as that in Example 1, except that Li5FeO4 is not added.

[0083] The specific preparation method includes: In a glove box under an argon atmosphere (O2 < 0.1 ppm, H2O < 0.1 ppm), 1,3-epoxypentane and LiTFSI are added for a first mixing treatment, wherein the mass ratio of 1,3-epoxypentane to LiTFSI is 1:0.125. The first mixing treatment is carried out at a temperature of 50℃ for 45 min, with a stirring speed of 100 rpm. After the mixture becomes clear, a first slurry is obtained. A 19 mm diameter glass fiber film is placed in a bottle for full permeation, then the film is removed and placed in a sealed glass jar to obtain a second slurry. The second slurry is heated at 45℃ for 12 hours to allow for complete polymerization. After the reaction is complete, it is transferred to a 25℃ vacuum drying oven and vacuum dried for 2 hours. The residual small molecule liquid is then removed to obtain P-DOL, which is the solid composite electrolyte of this comparative example.

[0084] The method for preparing the battery cell in this embodiment is the same as in Embodiment 1.

[0085] Comparative Example 2

[0086] The preparation method of the solid composite electrolyte in this comparative example is the same as that in Example 1, except that LiTFSI is not added.

[0087] The specific preparation method includes: In a glove box under an argon atmosphere (O2 < 0.1 ppm, H2O < 0.1 ppm), 1,3-epoxypentane and Li5FeO4 are added for a second mixing treatment. The amount of Li5FeO4 added relative to the mass of 1,3-epoxypentane is 12.5 wt%. The second mixing treatment is carried out at 30℃ for 12 hours with a stirring speed of 100 rpm. After the solution becomes viscous, a 19 mm diameter glass fiber film is placed into the bottle for full permeation. Then, the film is removed and placed in a sealed glass jar to obtain a second slurry. The second slurry is heated at 45℃ for 12 hours to allow for complete polymerization. After the reaction is complete, it is transferred to a 25℃ vacuum drying oven and vacuum dried for 2 hours. The residual small molecule liquid is then removed to obtain Li5FeO4-DOL, which is the solid composite electrolyte of this comparative example.

[0088] The method for preparing the battery cell in this embodiment is the same as in Embodiment 1.

[0089] Comparative Example 3

[0090] Lithium foil was used as the negative electrode active material and bonded to copper foil to obtain a negative electrode sheet with dimensions of 100mm × 55mm. A ternary material was used as the positive electrode active material, mixed with conductive agents and binders, coated onto aluminum foil, and then dried and pressed to form a positive electrode sheet with dimensions of 96mm × 51mm. A PE-based film was used as the separator. The electrolyte was 1M LiPF6 dissolved in a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) at a 1:1 volume ratio. The assembly process used a flexible stacking method, stacking the positive electrode sheet, separator, and negative electrode sheet in sequence to obtain the battery cell.

[0091] Test Example 1

[0092] The battery cells prepared in Examples 1-6 and Comparative Examples 1-3 were hot-pressed and placed in an aluminum-plastic film for top-side sealing. Electrolyte was injected into the battery, and the injected battery was sealed. The prepared batteries underwent formation treatment. When comparing the electrochemical performance of different positive electrode plates, the negative electrode loading remained essentially consistent. The charge / discharge cutoff voltage was set to 2.8-4.2V, the charge / discharge current to 1A / g, and the test was completed after 2000 cycles. The test results of the batteries prepared in Examples 1-6 and Comparative Examples 1-3 are shown in Table 1.

[0093] The electrolyte injection coefficient (g / Ah) is the amount of electrolyte added divided by the cell design capacity.

[0094] The initial efficiency test method includes: After the battery is manufactured, it is first charged at a constant current rate of 0.1C to 3.75V to obtain the formation capacity C0. Then, the battery is divided into equal parts and charged at a constant current rate of 0.33C to 4.25V, and then charged at a constant voltage of 4.25V until I≤0.05C to obtain the divided battery capacity C1. After standing for 5 minutes, the battery is discharged at a constant current rate of 1C to 2.8V to obtain the discharge capacity C2, then discharged at a constant current rate of 0.1C to 2.8V to obtain the discharge capacity C3, and finally discharged at a constant current rate of 0.01C to 2.8V to obtain the discharge capacity C4. The initial coulombic efficiency (first efficiency) is calculated as (C2+C3+C4) / (C0+C1)*100%.

[0095] The test method for capacity retention after 2000 cycles includes: 1. After capacity grading, the battery is first charged at a constant current rate of 1C to 4.25V, and then charged at a constant voltage of 4.25V until I≤0.05C; 2. After resting for 5 minutes, the battery is discharged at a constant current rate of 1C to 2.8V to obtain the discharge capacity C1; 3. After resting for 30 minutes, steps 1-3 are repeated 1999 times to obtain the discharge capacity C. 2000 ; Capacity retention rate over 2000 laps according to (C 2000 The result is calculated as (C1) / (C1)*100%.

[0096] Contact angle testing methods include those using optical contact angle meters, ranging from manual instruments to fully automated systems. In the seated drop method, a droplet (usually water) is placed on a solid sample, an image of the droplet is captured by a high-resolution camera, and then the angle is automatically measured by software.

[0097] The method for testing area shrinkage at 200℃ includes: taking a 10cm*10cm diaphragm area as S1, placing it at 200℃ for 2 hours, and then measuring the area as S2. The shrinkage rate is y=1-(S2 / S1).

[0098] Table 1

[0099]

[0100]

[0101] As shown in Table 1, compared with Examples 1-6 and Comparative Examples 1-3, the solid composite electrolyte prepared by this invention, when used in a separator, can effectively reduce the amount of liquid electrolyte used and the area shrinkage at 200°C, while improving the initial coulombic efficiency and capacity retention. A comparison of the contact angle test results of each example and comparative example shows that the introduction of Li5FeO4 can significantly reduce the separator contact angle, accelerate wetting, and form a polymer solid electrolyte layer with the polymer under plasticizing effect, enhancing contact with the positive and negative electrode surfaces and improving the solid-solid contact interface.

[0102] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A solid composite electrolyte, characterized in that, The solid composite electrolyte includes a lithium replenishing agent and a polymer electrolyte coated on the surface of the lithium replenishing agent; The polymer electrolyte comprises a solid solvent polymer and a lithium salt, wherein the lithium salt is dissolved in the solid solvent polymer; The lithium replenishing agent, the lithium salt, and the solid solvent polymer contained in the solid composite electrolyte satisfy the following relationship: 0.6≤m1 / (m1+m2+m3)≤0.9, where m1 represents the mass of the solid solvent polymer, m2 represents the mass of the lithium replenishing agent, and m3 represents the mass of the lithium salt; The mass ratio of the lithium salt to the lithium replenishing agent is 1:0.1~5.

2. The solid composite electrolyte according to claim 1, characterized in that, The lithium supplement, lithium salt and solid solvent polymer contained in the solid composite electrolyte satisfy the following relationship: 0.75≤m1 / (m1+m2+m3)≤0.

85.

3. The solid composite electrolyte according to claim 1, characterized in that, The mass ratio of the lithium salt to the lithium replenishing agent is 1:0.5~1.

5.

4. The solid composite electrolyte according to claim 1, characterized in that, The lithium supplement agent includes lithium oxides; And / or, the lithium salt is selected from at least one of LiTFSI, LiPF6, LiBF4, LiBOB, LiFSI and LiODFB; And / or, the solid solvent polymer is selected from at least one of poly(1,3-dioxolane), polyethylene oxide, polyvinyl alcohol, polymethyl methacrylate and polyvinylidene fluoride.

5. The solid composite electrolyte according to claim 4, characterized in that, The lithium oxide is selected from at least one of Li5FeO4, LiNiO2, Li2NiO2, Li2O, Li2O2, Li2MnO3, Li6MnO4, Li6CoO4 and Li5ReO6.

6. The solid composite electrolyte according to any one of claims 1 to 5, characterized in that, The solid composite electrolyte also includes glass fibers, which are dispersed in the solid solvent polymer.

7. The solid composite electrolyte according to claim 6, characterized in that, Based on the total mass of the solid composite electrolyte, the content of the glass fiber is 0.05~10wt%.

8. The solid composite electrolyte according to claim 7, characterized in that, Based on the total mass of the solid composite electrolyte, the content of the glass fiber is 1~5wt%.

9. A method for preparing a solid composite electrolyte, characterized in that, The preparation method includes the following steps: S1. The solid solvent polymer monomer and lithium supplementer are subjected to a first mixing treatment to obtain a first slurry; S2. The first slurry and lithium salt are subjected to a second mixing process to obtain a second slurry; S3. The second slurry is subjected to heat treatment and drying treatment.

10. The preparation method according to claim 9, characterized in that, The viscosity of the first slurry is 500~10000 Cp; And / or, the solid content of the first slurry is 10-50%; And / or, the viscosity of the second slurry is 50~20000 Cp; And / or, the solid content of the second slurry is 1~20%; And / or, the solid solvent polymer monomer is selected from at least one of 1,3-epoxypentane, ethylene oxide, vinyl acetate, methyl methacrylate and 1,1-difluoroethylene.

11. The preparation method according to claim 10, characterized in that, The viscosity of the first slurry is 1000~3000 Cp; And / or, the solid content of the first slurry is 15-30%; And / or, the viscosity of the second slurry is 50~200 Cp; And / or, the solid content of the second slurry is 5-10%.

12. The preparation method according to claim 9, characterized in that, In step S1, the conditions for the first mixing treatment include: a temperature of 40~60℃, a time of 10~120min, and a stirring speed of 800~1500rpm; And / or, in step S2, the conditions for the second mixing treatment include: a temperature of 40~60℃, a time of 30~60min, and a stirring speed of 600~900rpm; And / or, in step S3, the conditions for the heat treatment include: a temperature of 40~60℃ and a time of 30~90min; and / or, the conditions for the drying treatment include: a temperature of 40~60℃ and a time of 60~150min.

13. The preparation method according to any one of claims 9 to 12, characterized in that, The preparation method further includes: adding glass fibers to the second mixing process to obtain a second slurry containing glass fibers.

14. A battery, characterized in that, The battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a solid electrolyte layer. The solid electrolyte layer is a solid composite electrolyte as described in any one of claims 1 to 8 or a solid composite electrolyte prepared by the preparation method according to any one of claims 9 to 13.

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