A carbonate-based polymer electrolyte with a wide electrochemical window

Abstract

A carbonate-based polymer electrolyte with a wide electrochemical window belongs to the technical field of lithium-ion batteries. In the present invention, ethylene carbonate, a catalyst, a conductive lithium salt, a porous support material, and a solvent are used to prepare a carbonate-based polymer electrolyte with a wide electrochemical window through ring-opening polymerization of cyclic carbonates. Ring-opening polymerization eliminates the weak links in the cyclic carbonates, and at the same time, an addition reaction occurs to the C═C double bond, forming a three-dimensional network structure, which improves the electrochemical stability window, mechanical properties, and thermal stability of the polymer electrolyte. The preparation process of this polymer electrolyte is simple and easy to control, and it has excellent mechanical properties; the room temperature ionic conductivity > 10 ‑3 S cm ‑1 , the electrochemical window > 4.95 V (vs. Li + / Li), which has great innovation and practicality for the application of high-voltage cathode materials.

Description

Technical Field

[0001] The present invention relates to the field of polymer electrolytes for lithium - ion batteries, in particular to the preparation of a carbonate - based polymer electrolyte with a wide electrochemical window and its application in solid - state lithium - ion batteries, belonging to the technical field of lithium - ion batteries. Background Art

[0002] Lithium - ion batteries are increasingly widely used in electric vehicles and energy storage devices due to their advantages such as high energy density, fast charging, and convenient portability. Currently, most commercial batteries use conventional organic liquid electrolytes, such as ethylene carbonate, propylene carbonate, etc. However, the safety defects of organic electrolytes, such as high chemical activity, volatility, flammability, and explosiveness, seriously hinder the further popularization and application of lithium - ion batteries. In addition, when using metallic lithium as the negative electrode, during the operation of a liquid battery, with the continuous insertion and extraction of lithium ions, lithium dendrites will be formed on the surface of metallic lithium. The formation of lithium dendrites not only causes dead lithium areas and reduces the comprehensive performance of the battery, but also pierces the separator, causing battery short - circuit and even safety accidents such as fires, severely limiting the development and application of high - energy - density lithium - metal batteries. Therefore, the development of lithium - ion polymer electrolytes to replace traditional liquid electrolytes has epoch - making significance for the development of high - energy - density lithium - metal batteries. For the defects of inorganic solid electrolytes, such as complex preparation processes, poor mechanical properties, and interfacial compatibility, polymer electrolytes have been widely recognized due to their good compatibility with lithium metal, high thermal stability, simple preparation process, good flexibility, and adjustable shape and size. An ideal polymer electrolyte should have the following advantages: 1. Ion conductivity close to that of liquid electrolytes; 2. Good compatibility with electrodes; 3. A wide electrochemical window; 4. Simple preparation process. However, so far, it is difficult for polymer electrolytes to simultaneously meet the above advantages.

[0003] In 1973, Wright et al. reported that poly (ethylene oxide) (PEO) has ion - conducting functions, kicking off the research on polymer electrolytes. In 1979, it was confirmed and proposed by Armand to be used as the electrolyte material for solid - state batteries, which made the research on polymer electrolytes enter a new stage of development. However, due to the high crystallinity of PEO - based polymer electrolytes, they have low ion conductivity (the room - temperature conductivity of PEO is about 10 -7 Scm -1 ) and a relatively low electrochemical stability window at room temperature, and thus cannot be widely used and promoted. By physically modifying PEO (blending, adding plasticizers) and chemically modifying it (grafting modification), the ion conductivity of PEO can be improved to a certain extent (up to 10 -5 ~10 -4 S cm -1), but there are still problems of low electrochemical window and interfacial issues. Therefore, novel polymer electrolytes containing strongly polar carbonate groups [-O-(C=O)-O-] have attracted extensive attention from researchers. Patent No. CN105591154A provides a polycarbonate-based all-solid polymer electrolyte with an ionic conductivity of 2×10 -5 S cm -1 ~1×10 -3 S cm -1 at room temperature and an electrochemical window greater than 4V. Patent No. CN109802174A discloses a polycarbonate-based polymer electrolyte with an ionic conductivity > 10 -3 S cm -1 at room temperature, but its electrochemical window is only 4.7V and it cannot be applied to high-voltage cathode materials such as LiNi 0.5 Mn 1.5 O4. These two carbonate-based polymer electrolytes have high ionic conductivity and good interfacial stability, but their electrochemical windows are low (<4.7V) and they are not suitable for application in high-voltage cathode material systems such as LiNi 0.5 Mn 1.5 O4.

[0004] To address the above problems, we have developed a carbonate-based polymer electrolyte with a wide electrochemical window. By selecting ethylene carbonate, a catalyst, a conductive lithium salt, a porous support material, and a solvent, and through ring-opening polymerization of cyclic carbonates, a carbonate-based polymer electrolyte with a wide electrochemical window is prepared. Ring-opening polymerization eliminates the weak links in cyclic carbonates, and at the same time, an addition reaction occurs to the C=C double bond, forming a three-dimensional network structure, which improves the electrochemical stability window, mechanical properties, and thermal stability of the polymer electrolyte. The preparation process of this polymer electrolyte is simple and easy to control, and it has excellent mechanical properties; its ionic conductivity > 10 -3 S cm -1 at room temperature, and its electrochemical window > 4.95V (vs. Li + / Li), which has great innovation and practicality for the application of high-voltage cathode materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a carbonate-based polymer electrolyte with a wide electrochemical window and its application in solid-state lithium-ion batteries.

[0006] The technical solution of the present invention is as follows:

[0007] A carbonate-based polymer electrolyte with a wide electrochemical window selects ethylene carbonate, a conductive lithium salt, an organic solvent, and a catalyst as raw materials, mixes the raw materials to form a mixture, immerses a porous support material in the mixture or coats the mixture onto the porous support material, and prepares a carbonate-based polymer electrolyte with a wide electrochemical window through ring-opening polymerization of cyclic carbonates.

[0008] Among them, the mass fraction of ethylene carbonate in the mixture is 25 - 80%, the mass fraction of the conductive lithium salt in the mixture is 10 - 50%, the mass fraction of the organic solvent in the mixture is 0 - 50%, and the mass fraction of the catalyst is 0.1 - 10% of the mass of ethylene carbonate. The room-temperature ionic conductivity of this polymer electrolyte > 10 -3 Scm -1 , and the electrochemical window > 4.95V (vs. Li + / Li), which has great innovation and practicality for the application of high-voltage cathode materials.

[0009] Ring-opening polymerization eliminates the weak links in the cyclic carbonate, and at the same time, an addition reaction occurs to the C = C double bond to form a three-dimensional network structure. The polymer electrolyte structure formed by the ring-opening polymerization of the carbon cyclic carbonate is as follows:

[0010]

[0011] Among them, the values of x and y are 1 - 50000; the dotted lines therein are to connect other corresponding structures to make the polymer electrolyte form a three-dimensional network structure.

[0012] The conductive lithium salt is one or more of the following: lithium hexafluorophosphate (LiPF6), lithium difluorooxalate borate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(trifluoromethanesulfonyl)methyl [LiC(SO2CF3)3].

[0013] The organic solvent is one or more of the following: N-methylpyrrolidone (NMP), ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethylene glycol carbonate, ethyl methyl carbonate, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, acetonitrile, 1,2-dimethoxyethane, tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethyl sulfoxide;

[0014] The catalyst is one of the following: aluminum isopropoxide, stannum, cycloalkoxytin, tin chloride, magnesium octoate, potassium tert-butoxide, lithium tert-butoxide, trifluoromethanesulfonic acid, methyl trifluoromethanesulfonate, boric acid or its derivatives, hexaalkylguanidine salts or their derivatives.

[0015] The porous support material is one or more of cellulose non-woven fabric, polyethylene non-woven fabric, polypropylene non-woven fabric, glass fiber non-woven fabric, and polytetrafluoroethylene non-woven fabric.

[0016] The preparation of the wide electrochemical window carbonate-based polymer electrolyte includes the following steps: Prepare an electrolyte by mixing ethylene carbonate, a conductive lithium salt, and an organic solvent with corresponding mass fractions, and stir evenly; add a catalyst with a corresponding mass fraction and stir evenly; coat or immerse the above electrolyte into a polytetrafluoroethylene mold containing a porous support material, and heat and cure at 60 - 120 °C for 2 - 12 hours to form a film.

[0017] The present invention provides a polymer lithium-ion battery, including: a positive electrode, a negative electrode, and a polymer electrolyte disposed between the positive electrode and the negative electrode and having both the functions of a separator and an electrolyte.

[0018] For the polymer lithium-ion battery, the positive electrode active material is one or more of lithium manganate, lithium iron phosphate (LiFeO4), lithium nickel cobalt aluminate (NCA), lithium manganese oxide, lithium iron manganese phosphate, lithium cobaltate (LiCoO2), lithium nickel manganate, lithium-rich materials (LLOs), lithium nickel cobalt manganate, lithium ion fluorophosphate, and lithium nickelate (LiNiO2); the negative electrode active material is one or more of metallic lithium, metallic lithium alloy, carbon-silicon composite material, lithium titanate, graphite, lithium metal nitride, antimony oxide, carbon-germanium composite material, and lithium titanium oxide. The preparation of the positive electrode includes the following steps: The preparation of the positive electrode material includes the following steps: Grind and mix 50 - 90% of the positive electrode active material and 5 - 30% of the conductive agent acetylene black, add 1 - 15% of polyvinylidene fluoride (PVDF) and 1 - 15% of the electrolyte mixture (the above substances add up to 100%), and then add 1-methyl-2-pyrrolidone (NMP) to grind and mix to obtain the positive electrode material, where 1-methyl-2-pyrrolidone (NMP) is used to adjust the viscosity and is not included in the mass percentage composition of the positive electrode material; coat the positive electrode material on the surface of the aluminum foil and dry to obtain the positive electrode; metallic lithium and metallic lithium alloy can also be directly used as the corresponding negative electrode. The preparation of the negative electrode includes the following steps: Grind and mix 30 - 80% of the negative electrode active material and 5 - 30% of the conductive agent acetylene black, add 5 - 25% of polyvinylidene fluoride (PVDF), 1 - 15% of the electrolyte mixture (the above substances add up to 100%) and 1-methyl-2-pyrrolidone (NMP) to grind and mix to obtain the negative electrode material; where 1-methyl-2-pyrrolidone (NMP) is used to adjust the viscosity and is not included in the mass percentage composition of the negative electrode material; coat on the surface of the copper foil and dry to obtain the negative electrode.

[0019] The polymer lithium-ion battery: The composition of the electrolyte mixture in the positive electrode material and the negative electrode material is as follows: The mass fraction of vinylene carbonate in the electrolyte mixture is 30-80% of the mass of the electrolyte mixture, the mass fraction of the conductive lithium salt in the electrolyte mixture is 10-50% of the mass of the electrolyte mixture, the mass fraction of the organic solvent in the electrolyte mixture is 1-50% of the mass of the electrolyte mixture, and the mass fraction of the catalyst is 0.1-10% of the mass of vinylene carbonate; The specific selection range of each substance in the electrolyte mixture is the same as the selection range of each substance of the carbonate-based polymer electrolyte raw material.

[0020] The polymer lithium-ion battery is characterized in that: The preparation of the battery can be (1): Non-in-situ assembly process---positive electrode, negative electrode and the above-mentioned composite solid electrolyte; (2): In-situ assembly process---inject the above-mentioned electrolyte mixture into the battery system of the positive electrode, separator and negative electrode, and cure at 60-120°C for 2-24 hours.

[0021] The innovation and practicality of the present invention lie in:

[0022] The present invention selects vinylene carbonate, conductive lithium salt, organic solvent and catalyst, immerses the porous support material into the liquid mixture or coats the liquid mixture on the porous support material, and prepares a carbonate-based polymer electrolyte with a wide electrochemical window through ring-opening polymerization of cyclic carbonate. Ring-opening polymerization eliminates the weak links in cyclic carbonate, and at the same time, C═C double bonds undergo an addition reaction to form a three-dimensional network structure, improving the electrochemical stability window, mechanical properties, thermal stability, ion transference number of the polymer electrolyte, improving the interfacial compatibility between the polymer electrolyte and the electrode material, and improving the charge and discharge performance of the solid-state lithium-ion battery. The room-temperature ionic conductivity of this polymer electrolyte > 10 -3 S cm -1 , the electrochemical window > 4.95V (vs. Li + / Li), suitable for application in high-voltage positive electrode material systems such as LiNi 0.5 Mn 1.5 O4, etc., has great innovation and practicality for the application of high-voltage positive electrode materials. This polymer electrolyte can effectively inhibit the growth of lithium negative electrode dendrites, improve the interfacial compatibility and long cycle performance; The solid-state lithium-ion battery can work for a long time at room temperature. At the same time, this polymer electrolyte has good flexibility and is also suitable for flexible lithium-ion battery devices of wearable electronic devices

[0023] Meanwhile, when the polymer electrolyte is assembled into a solid-state lithium-ion battery, it can form a protective layer on the surface of the lithium battery electrode material and metallic lithium, which can effectively inhibit the damage of the electrode crystal caused by the insertion and extraction of lithium ions, thereby improving the long-cycle stability performance of the lithium battery. Moreover, during the preparation process of the polymer electrolyte of the present invention, organic solvents can be not added, and in-situ polymerization is used to prepare the polymer electrolyte, eliminating potential safety hazards and environmental pollution, and greatly enhancing the safety and practicality of the lithium battery. It can be applied to all-solid-state lithium batteries (including lithium-sulfur batteries), all-solid-state lithium-ion batteries, and other secondary high-energy lithium batteries. Description of the Drawings

[0024] Figure 1 It is the linear voltammetry scan curve of the electrolyte in Preparation Example 2 of the polymer electrolyte.

[0025] Figure 2 It is the charge and discharge performance of the lithium-ion battery in Preparation Example 6 of the solid-state lithium-ion battery. Detailed Embodiments

[0026] The following uses specific examples to illustrate the present invention. The examples are for better understanding of the present invention and in no way limit the scope of the present invention.

[0027] Preparation of the polymer electrolyte:

[0028] Example 1

[0029] Dissolve 10 g of ethylene carbonate and 3 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 10 ml of acetonitrile, and stir at room temperature until completely dissolved; add 0.2 g of tin chloride. On a polytetrafluoroethylene mold, using non-woven fabric as the porous support skeleton, scrape the stirred mixture onto both sides of the non-woven fabric membrane; heat in a vacuum drying oven at 80 °C for 10 hours to cure into a film.

[0030] Example 2

[0031] Dissolve 1 g of ethylene carbonate and 0.25 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 1.5 ml of N-methylpyrrolidone (NMP), and stir at room temperature until completely dissolved; add 0.02 g of stannous octoate and stir evenly. On a polytetrafluoroethylene mold, using a whatman membrane as the porous support skeleton, scrape the stirred mixture onto both sides of the whatman membrane; heat in a vacuum drying oven at 80 °C for 10 hours to cure into a film.

[0032] Example 3

[0033] Dissolve 1.38 g of ethylene carbonate and 0.4 g of lithium perchlorate (LiClO4) in 1.5 ml of N-methylpyrrolidone (NMP), and stir at room temperature until completely dissolved; add 0.02 g of methyl trifluoromethanesulfonate and stir evenly. On a polytetrafluoroethylene mold, with a whatman membrane as the porous support framework, scrape the evenly stirred mixture onto both sides of the whatman membrane; heat in a vacuum drying oven at 80 °C for 10 hours to cure into a film.

[0034] Example 4

[0035] Dissolve 15 g of ethylene carbonate and 5 lithium perchlorate (LiClO4) in 2 ml of tetrahydrofuran, and stir at room temperature until completely dissolved; add 0.5 g of stannous octoate and stir evenly. On a polytetrafluoroethylene mold, with a cellulose membrane as the porous support framework, scrape the evenly stirred mixture onto both sides of the cellulose membrane; heat in a vacuum drying oven at 80 °C for 10 hours to cure into a film.

[0036] Electrolyte thickness: Use a micrometer (accuracy 0.01 mm) to measure the thickness of the block copolymer electrolyte. Arbitrarily measure 3 points on the film and calculate the average value.

[0037] Ionic conductivity: Clamp the polymer electrolyte with two stainless steel gaskets, assemble a 2032 coin cell to measure the impedance, according to the formula where L is the thickness of the polymer electrolyte, S is the area of the stainless steel gasket, and R is the measured impedance value.

[0038] Electrochemical window: Clamp the polymer electrolyte with stainless steel and a lithium sheet, assemble a 2032 coin cell, and perform linear voltammetry scanning measurement. The starting voltage is 2.8 V, the maximum potential is 5.5 V, and the scanning speed is 1 mV S -1 .

[0039] Example <![CDATA[Ionic conductivity (S cm -1 , 25 °C)]]> Electrochemical window (V) 1 <![CDATA[1.05×10 -3 > 4.95 2 <![CDATA[1.11×10 -3 > 5.00 3 <![CDATA[1.21×10 -3 > 4.97 4 <![CDATA[1.01×10 -3 > 4.97

[0040] Preparation of polymer lithium-ion battery: The specific composition of the electrolyte mixture used in the following examples is the same as the corresponding solid polymer electrolyte component.

[0041] Example 5

[0042] Grind 800 mg of lithium nickel cobalt aluminate and 150 mg of conductive agent acetylene black evenly for 40 min; add 50 mg of binder polyvinylidene fluoride, 30 mg of electrolyte mixture and 1600 μL of 1-methyl-2-pyrrolidone and grind evenly for 40 min; coat on the surface of the aluminum foil, dry at 80 °C for 8 h under vacuum to obtain the positive electrode; cut the positive electrode into a circle with R = 0.6 mm, use the polymer electrolyte prepared in Example 1 of the above polymer electrolyte to assemble a solid-state lithium-ion half-cell, and then use metallic lithium as the negative electrode.

[0043] Example 6

[0044] 80 mg of the lithium-rich material and 10 mg of the conductive agent acetylene black were uniformly ground for 40 min; 5 mg of the binder polyvinylidene fluoride, 5 mg of the electrolyte mixture, and 150 μL of 1-methyl-2-pyrrolidone were added and uniformly ground for 40 min; it was coated on the surface of the aluminum foil and dried at 80 °C for 8 h under vacuum conditions to obtain the positive electrode; the positive electrode was cut into a disc with R = 0.6 mm, and the polymer electrolyte prepared in Example 2 of the above polymer electrolyte was used to assemble a solid-state lithium-ion half-cell, and then metallic lithium was used as the negative electrode.

[0045] Example 7

[0046] 250 mg of lithium nickel cobalt aluminate and 46.8 mg of the conductive agent acetylene black were uniformly ground for 40 min; 15 mg of the binder polyvinylidene fluoride, 15 mg of the electrolyte mixture, and 150 μL of 1-methyl-2-pyrrolidone were added and uniformly ground for 40 min; it was coated on the surface of the aluminum foil and dried at 80 °C for 8 h under vacuum conditions to obtain the positive electrode; the positive electrode was cut into a disc with R = 0.6 mm, and the polymer electrolyte prepared in Example 4 of the above polymer electrolyte was used to assemble a solid-state lithium-ion half-cell, and then metallic lithium was used as the negative electrode.

Claims

1. A carbonate-based polymer electrolyte with a wide electrochemical window, characterized in that Ethylene carbonate, a conductive lithium salt, an organic solvent and a catalyst are selected as raw materials, and the raw materials are mixed to form a mixture. The porous support material is immersed in the mixture or the mixture is coated on the porous support material. Through ring-opening polymerization of cyclic carbonate, a carbonate-based polymer electrolyte with a wide electrochemical window is prepared. Ring-opening polymerization eliminates the weak links in the cyclic carbonate, and at the same time, an addition reaction occurs on the C═C double bond to form a three-dimensional network structure. The polymer electrolyte structure formed by the ring-opening polymerization of the cyclic carbonate is as follows: Among them, the values of x and y are 1 - 50000; the dotted lines therein are used to connect other corresponding structures to make the polymer electrolyte form a three-dimensional network structure. The catalyst is one of the following: stannous octanoate, cycloalkoxytin, tin chloride, trifluoromethanesulfonic acid, methyl trifluoromethanesulfonate.

2. The polycarbonate-based polymer electrolyte with a wide electrochemical window according to claim 1, characterized in that Among them, the mass fraction of ethylene carbonate in the mixture is 25 - 80%, the mass fraction of the conductive lithium salt in the mixture is 10 - 50%, the mass fraction of the organic solvent in the mixture is 0 - 50%, and the mass fraction of the catalyst is 0.1 - 10% of the mass of ethylene carbonate.

3. A carbonate-based polymer electrolyte with a wide electrochemical window according to claim 1, characterized in that, The conductive lithium salt is one or more of the following: lithium hexafluorophosphate (LiPF6), lithium difluorooxalate borate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(trifluoromethanesulfonyl)methyl (LiC(SO2CF3)3); The organic solvent is one or more of the following: N-methylpyrrolidone (NMP), ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethylene glycol carbonate, ethyl methyl carbonate, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, acetonitrile, 1,2-dimethoxyethane, tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethyl sulfoxide; The porous support material is one or more of cellulose non-woven fabric, polyethylene non-woven fabric, polypropylene non-woven fabric, glass fiber non-woven fabric, polytetrafluoroethylene non-woven fabric.

4. A method for preparing a carbonate-based polymer electrolyte with a wide electrochemical window according to claim 1, characterized in that, It includes the following steps: Prepare an electrolyte by taking corresponding mass fractions of ethylene carbonate, a conductive lithium salt and an organic solvent, and stir evenly; add a corresponding mass fraction of the catalyst and stir evenly; coat or immerse the above electrolyte into a polytetrafluoroethylene mold containing a porous support material, and heat and cure at 60 - 120 °C for 2 - 12 hours to form a film.

5. A polymer lithium-ion battery, characterized in that, It includes: A positive electrode, a negative electrode, and a polymer electrolyte having both the functions of a separator and an electrolyte placed between the positive electrode and the negative electrode; the polymer electrolyte is a carbonate-based polymer electrolyte with a wide electrochemical window according to any one of claims 1 - 4.

6. A polymer lithium ion battery according to claim 5, characterized in that, The positive electrode active material is one or more of lithium manganate, lithium iron phosphate (LiFeO4), lithium nickel cobalt aluminate (NCA), lithium manganese oxide, lithium manganese iron phosphate, lithium cobalt oxide (LiCoO2), lithium nickel manganate, lithium-rich materials (LLOs), lithium nickel cobalt manganate, lithium ion lithium fluorophosphate, lithium nickel oxide (LiNiO2); the negative electrode active material is one or more of metallic lithium, metallic lithium alloy, carbon-silicon composite material, lithium titanate, graphite, lithium metal nitride, antimony oxide, carbon-germanium composite material, lithium titanium oxide; the preparation of the positive electrode includes the following steps: The preparation of the positive electrode material includes the following steps: grinding and mixing 50-90% of the positive electrode active material and 5-30% of the conductive agent acetylene black, adding 1-15% of polyvinylidene fluoride (PVDF) and 1-15% of the electrolyte mixture, and then adding 1-methyl-2-pyrrolidone (NMP) for grinding and mixing to obtain the positive electrode material, where 1-methyl-2-pyrrolidone (NMP) is used to adjust the viscosity and is not included in the mass percentage composition of the positive electrode material; coating the positive electrode material on the surface of the aluminum foil and drying to obtain the positive electrode; or metallic lithium and metallic lithium alloy are directly used as the corresponding negative electrodes; the preparation of the negative electrode includes the following steps: grinding and mixing 30-80% of the negative electrode active material and 5-30% of the conductive agent acetylene black, adding 5-25% of polyvinylidene fluoride (PVDF), 1-15% of the electrolyte mixture and 1-methyl-2-pyrrolidone (NMP) for grinding and mixing to obtain the negative electrode material; where 1-methyl-2-pyrrolidone (NMP) is used to adjust the viscosity and is not included in the mass percentage composition of the negative electrode material; coating on the surface of the copper foil and drying to obtain the negative electrode.

7. A polymer lithium ion battery according to claim 6, characterized in that, The composition of the electrolyte mixture in the positive electrode material and the negative electrode material is: the mass fraction of ethylene carbonate in the electrolyte mixture component is 30-80% of the mass of the electrolyte mixture, the mass fraction of the conductive lithium salt in the electrolyte mixture is 10-50%, the mass fraction of the organic solvent in the electrolyte mixture is 1-50%, and the mass fraction of the catalyst is 0.1-10% of the mass of ethylene carbonate; the specific selection range of each substance in the electrolyte mixture is the same as the selection range of each substance in the raw materials of the carbonate-based polymer electrolyte.

8. A method for preparing a polymer lithium-ion battery according to claim 5, characterized in that, It includes two processes, (1): non-in-situ assembly process---positive electrode, negative electrode and the above-mentioned carbonate-based polymer electrolyte with a wide electrochemical window; (2): in-situ assembly process---injecting the above-mentioned electrolyte mixture into the battery system of the positive electrode, separator and negative electrode, and curing at 60-120 °C for 2-24 hours.

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