Method for assembling lithium battery from polymer electrolyte

Abstract

The invention discloses a method for assembling a lithium battery from a polymer electrolyte. The method comprises in-situ copolymerization or ectopic copolymerization, the in-situ copolymerization comprises the following steps: blending cyclic anhydride, cyclic acetal, a lithium salt and a selectively added catalyst to obtain a precursor solution, placing a porous support material infiltrated with the precursor solution between a positive electrode and a negative electrode, assembling, heating and copolymerizing to obtain an in-situ copolymerized lithium battery; the ectopic copolymerization comprises the following steps: blending cyclic anhydride, cyclic acetal, a lithium salt and a selectively added catalyst, carrying out heating copolymerization to obtain a polymer electrolyte, dissolving the polymer electrolyte in an organic solvent to obtain a mixed solution, carrying out vacuum drying on a porous support material infiltrating the mixed solution, and placing the dried porous support material between a positive electrode and a negative electrode to obtain the lithium ion battery. And assembling to obtain the ectopic copolymerization lithium battery. The polymer electrolyte prepared by the method has excellent room-temperature ionic conductivity, good electrode / electrolyte interface contact, excellent thermal stability and wide electrochemical window; and various positive and negative electrode materials are adapted.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a method for assembling lithium batteries using polymer electrolytes. Background Art

[0002] As an efficient and safe energy storage technology, lithium-ion batteries are widely used in portable electronic products, electric vehicles, and large-scale energy storage equipment. However, commercial lithium batteries currently use flammable and leaky small molecule organic electrolytes, which pose safety risks such as fire and explosion. One strategy to solve this problem is to use polymer electrolytes.

[0003] Polymer electrolytes are considered to be one of the most commercially valuable lithium battery electrolytes due to their high electrochemical stability, good processing performance, diverse shapes, and good flexibility. Generally speaking, an ideal polymer electrolyte needs to meet the following conditions: -4 S / cm room temperature ionic conductivity, good electrode / electrolyte interface contact, high lithium ion transference number, high chemical stability, electrochemical stability and thermal stability. However, it is difficult for current polymer electrolyte systems to meet the above requirements at the same time.

[0004] At present, the polymer matrix of polymer electrolytes is mostly polyethers such as polyethylene oxide (PEO), polyesters, polycarbonates, polyionic liquids, etc. + / Li)PEO solid electrolytes have been commercialized, but the low ionic conductivity of PEO-based polymer electrolytes at room temperature limits their application at room temperature; at the same time, polyether polymer electrolytes are generally recognized in the field as not suitable for 4V (VS.Li + / Li) or above, which hinders its application in high energy density lithium batteries (ACS Energy Lett. 2020, 5, 10, 3244–3253).

[0005] In addition, lithium metal anode has a very high specific capacity (3860 mAh g -1, which is more than ten times that of the currently commercialized graphite negative electrode). The extremely low reduction potential (-3.04V vs standard hydrogen potential) is regarded as the "holy grail" for improving energy density. Lithium metal batteries with ultra-high theoretical energy density are also ideal candidates for the next generation of energy storage devices. The instability of carbonyl groups and metallic lithium limits the application of polycarbonate-based and polyester-based polymer electrolytes in lithium metal batteries, and the strong rigidity inhibits the movement of polymer segments, and usually requires a higher lithium salt concentration to improve its ionic conductivity. For example, Y. Tominaga et al. (Electrochemistry Communications, 66, 2016, 5, 46-48) prepared a high salt concentration polyvinyl carbonate-based electrolyte, and after adding up to 80wt% of LiFSI, the conductivity at 30°C was 1.6×10 -5 S / cm. However, the large-scale use of lithium salts significantly increases the production cost of lithium batteries.

[0006] Future energy storage devices urgently need to achieve high energy density, low-cost lithium batteries, and the structural design of polymers is expected to overcome this problem. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention discloses a method for assembling a lithium battery from a polymer electrolyte. The polymer electrolyte prepared by the method has excellent room temperature ionic conductivity, good electrode / electrolyte interface contact, excellent thermal stability and a wide electrochemical window; it is compatible with a variety of positive and negative electrode materials, and is particularly suitable for high-voltage positive electrodes and lithium metal negative electrodes with high energy density. The raw materials are widely available, the monomers have strong universality, the amount of lithium salt used is small, and the production cost is low. The prepared lithium battery has excellent room temperature and low-temperature and high-temperature cycle stability.

[0008] The specific technical solutions are as follows:

[0009] A method for assembling a lithium battery from a polymer electrolyte, comprising in-situ copolymerization or ex-situ copolymerization;

[0010] The in-situ copolymerization comprises the following steps:

[0011] The cyclic anhydride, cyclic acetal, lithium salt and a catalyst which can be optionally added are mixed to obtain a precursor solution, the separator soaked in the precursor solution is placed between the positive electrode and the negative electrode, and after assembly, the separator is heated and copolymerized to prepare an in-situ copolymerized lithium battery;

[0012] The heterotopic copolymerization comprises the following steps:

[0013] Cyclic anhydride, cyclic acetal, lithium salt and a catalyst which can be optionally added are mixed to obtain a precursor solution, and a polymer electrolyte is obtained after heating copolymerization, and the polymer electrolyte is dissolved in an organic solvent to obtain a mixed solution, and a diaphragm soaked in the mixed solution is vacuum dried and placed between a positive electrode and a negative electrode, and an ex situ copolymerized lithium battery is obtained after assembly;

[0014] In the in-situ copolymerization or the hetero-situ copolymerization, the molar ratio of the cyclic anhydride to the cyclic acetal is 1:1-2.

[0015] The present invention uses cyclic anhydride and cyclic acetal as raw material monomers, prepares a polymer electrolyte through in-situ copolymerization or ex-situ copolymerization, and assembles a lithium battery. The T g It is far below room temperature, and is in a viscous flow state at room temperature, and has better compatibility with the positive and negative electrodes, so it has excellent cycle stability at room temperature, high (80°C), and low temperature (0°C). In addition, the polymer electrolyte prepared by the present invention has excellent room temperature ionic conductivity, excellent thermal stability, and a wide electrochemical window, and is suitable for a variety of positive and negative electrode materials, especially for high-voltage positive electrodes and lithium metal negative electrodes with high energy density.

[0016] In the present invention, the molar ratio of cyclic anhydride to cyclic acetal needs to be strictly controlled, and the cyclic anhydride cannot be excessive. Experiments have found that if the cyclic anhydride is added in excess, residual cyclic anhydride will be detected in the prepared polymer electrolyte, which will lead to a significant decrease in the electrochemical window and thermal decomposition temperature of the polymer electrolyte.

[0017] Whether to adopt in-situ copolymerization or ex-situ copolymerization depends on whether the cyclic anhydride and lithium salt can be completely dissolved in the cyclic acetal to form a uniform solution under the actual monomer ratio and lithium salt concentration. If they are completely dissolved, the in-situ copolymerization method can be adopted. If they are not completely dissolved and require external auxiliary dissolution, the ex-situ copolymerization method is suitable.

[0018] Experiments have shown that, compared with in-situ copolymerization, the polymer electrolyte prepared by ex-situ copolymerization has a slightly lower room temperature ionic conductivity, but a slightly higher electrochemical window and thermal decomposition temperature.

[0019] In the present invention, the cyclic anhydride is selected from a five-membered cyclic anhydride and / or a six-membered cyclic anhydride;

[0020] The five-membered ring anhydride is selected from one or more of maleic anhydride, succinic anhydride, 2,3-dimethylmaleic anhydride, 2,3-dichloromaleic anhydride, 2,3-dibromomaleic anhydride, 2,3-difluoromaleic anhydride, methylsuccinic anhydride, phthalic anhydride, and 3,4,5,6-tetrahydrophthalic anhydride;

[0021] The six-membered cyclic acid anhydride is selected from one or more of glutaric anhydride, diglycolic anhydride, thioglycolic anhydride, 3-methylglutaric anhydride, 3,3-dimethylglutaric anhydride, 2,2-dimethylglutaric anhydride, 3-isobutylglutaric anhydride, hexafluoroglutaric anhydride, 3,3-tetramethyleneglutaric anhydride, and 1,1-cyclohexyldiacetic anhydride;

[0022] Preferably, the cyclic anhydride is selected from six-membered cyclic anhydride, specifically one or more selected from glutaric anhydride, thiohydroxyacetic anhydride, 3-methylglutaric anhydride, 3,3-dimethylglutaric anhydride, 2,2-dimethylglutaric anhydride, diglycolic anhydride, hexafluoroglutaric anhydride. It is found through experiments that the polymer electrolyte prepared by using six-membered cyclic anhydride has higher room temperature ionic conductivity.

[0023] Further preferably, the cyclic anhydride is selected from glutaric anhydride and / or hexafluoroglutaric anhydride, and the polymer electrolyte prepared by the two has higher room temperature ionic conductivity and electrochemical window; and the lithium battery assembled with the polymer electrolyte prepared by hexafluoroglutaric anhydride has higher electrochemical stability and better cycle stability at room temperature and high and low temperatures.

[0024] In view of the situation where higher requirements are placed on heat resistance, it is further preferred that the cyclic anhydride is selected from glutaric anhydride. Experiments have shown that the thermal decomposition temperature of the polymer electrolyte prepared using glutaric anhydride is higher.

[0025] In the present invention, the cyclic acetal is selected from one or more of a five-membered cyclic acetal, a six-membered cyclic acetal, a seven-membered cyclic acetal, and an eight-membered cyclic acetal;

[0026] The five-membered ring acetal is selected from one or more of 1,3-dioxolane, 2,2-dimethyl-1,3-dioxolane, 2-chloromethyl-1,3-dioxolane, 2-propyl-4-methyl-1,3-dioxolane, 2-(trifluoromethyl)dioxolane, 4-methyl-2-pentyl-1,3-dioxolane, 2-bromomethyl-1,3-dioxolane and 2-(2-bromoethyl)-1,3-dioxane;

[0027] The six-membered ring acetal is selected from one or more of 1,3-dioxane, 4-methyl-1,3-dioxane, glycerol formal, 2-(2-bromoethyl)-1,3-dioxane, and 4-phenyl-1,3-dioxane;

[0028] The seven-membered ring acetal is selected from one or more of 1,3-dioxepin, 2-methylene-1,3-dioxane, and cis-4,7-dihydro-1,3-dioxepin;

[0029] The eight-membered ring acetal is selected from 1,3-dioxocane and / or 1,3,6-trioxocane.

[0030] Preferably, the cyclic acetal is selected from one or more of 1,3-dioxolane, 2,2-dimethyl-1,3-dioxolane, 2-propyl-4-methyl-1,3-dioxolane, 4-methyl-2-pentyl-1,3-dioxolane, 1,3-dioxane, 4-methyl-1,3-dioxane, 1,3-dioxane, 1,3-dioxane, 1,3-dioxane and / or 1,3,6-trioxane. The above preferred cyclic acetals have higher reactivity and are more likely to undergo ring-opening copolymerization under mild conditions; and the raw material sources are wide and the production cost is low.

[0031] More preferably, the cyclic acetal is selected from one or more of 1,3-dioxolane, 1,3-dioxane, 4-methyl-1,3-dioxane, 1,3-dioxepin, 1,3-dioxoctane, and 1,3,6-trioxoctane; more preferably, it is one or more of 1,3-dioxolane, 1,3-dioxane, 1,3-dioxepin, and 1,3-dioxoctane; more preferably, it is 1,3-dioxane and / or 1,3-dioxepin; and most preferably, it is 1,3-dioxane. With the continuous optimization of the above cyclic acetal types, the room temperature ionic conductivity and electrochemical window of the prepared polymer electrolyte are higher.

[0032] In the present invention, the lithium salt is selected from one or more of lithium bis(oxalatoborate), lithium tetrafluoroborate, lithium hexafluorophosphate, lithium difluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl imide), lithium difluorooxalatoborate, lithium difluorophosphate, lithium trifluorosulfonyl imide, lithium bis(trifluoromethanesulfonate), and lithium bis(trifluoromethanesulfonyl imide).

[0033] The molar number of the monomer is calculated based on the total molar number of the cyclic anhydride and the cyclic acetal, and the molar ratio of the lithium salt to the monomer is 0.03 to 0.12, or 0.7 to 0.8; within the above preferred dosage range, the room temperature ionic conductivity of the prepared polymer electrolyte can reach 10 -4 S / cm.

[0034] Based on cost considerations, preferably, the molar ratio of lithium salt to monomer is 0.03 to 0.12.

[0035] In the present invention, the catalyst is selected from Lewis acid or protonic acid;

[0036] Preferably, the catalyst is selected from Lewis acids with weaker acidity to reduce damage to electrode materials, and is specifically selected from one or more of boron trifluoride, tin tetrachloride, aluminum trichloride, antimony pentachloride, ethyl trifluoromethanesulfonate, and triphenyl hexafluorophosphate.

[0037] Preferably, the molar ratio of the catalyst to the cyclic anhydride is 1 to 5:100.

[0038] In the present invention, whether it is in-situ copolymerization or hetero-situ copolymerization, preferably, the molar ratio of cyclic anhydride to cyclic acetal is 1:1; when the two are added in equimolar amounts, the prepared polymerization product is an alternating copolymer of the two, and when the cyclic acetal is excessive, a certain amount of cyclic acetal homopolymer is also produced in the polymerization product. It is found through experiments that when the cyclic acetal is excessive, the room temperature ionic conductivity, electrochemical window and thermal decomposition temperature of the prepared polymer electrolyte are significantly reduced.

[0039] In the heterotopic copolymerization, the organic solvent is selected from one or more of acetonitrile, acetone, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide.

[0040] On the basis of the above raw materials, further preferred are:

[0041] The cyclic acetal is selected from 1,3-dioxane;

[0042] The lithium salt is selected from one or more of lithium difluorooxalatoborate, lithium hexafluorophosphate, lithium difluorophosphate, and lithium tetrafluoroborate.

[0043] Experiments have shown that the 1,3-dioxane used in the reaction system has special properties. When the lithium salt used is selected from the above situation, the lithium salt is also used as a catalyst without the need to add an additional catalyst. The polymer electrolyte prepared at this time will have the best room temperature ionic conductivity, electrochemical window and thermal decomposition temperature, as well as cyclic stability at room temperature and high and low temperatures.

[0044] The experiment also found that in the present reaction system, cyclic anhydride and cyclic acetal must be added in equimolar amounts. Even a slight excess of cyclic acetal will lead to a significant decrease in the electrochemical window and thermal decomposition temperature of the prepared polymer electrolyte.

[0045] The diaphragm used in the present invention is selected from porous support materials;

[0046] The porous support material is selected from one or more of glass fiber, cellulose, polyethylene membrane, polypropylene membrane, nylon non-woven membrane, seaweed fiber non-woven membrane, bacterial cellulose, polyimide non-woven membrane, polyamide membrane, spandex membrane, and aramid membrane;

[0047] The positive electrode is selected from one or more of lithium cobalt oxide, lithium cobalt phosphate, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel manganese oxide, lithium nickel oxide, lithium manganese-rich base, nickel cobalt manganese ternary material, sulfur positive electrode, lithium fluorophosphate, lithium vanadium fluorophosphate, lithium iron fluorophosphate, lithium manganese oxide, and lithium manganese oxide;

[0048] The negative electrode is selected from one or more of metallic lithium, metallic lithium alloy, hard carbon, graphite, molybdenum disulfide, lithium titanate, graphene, antimony oxide, and silicon.

[0049] The method disclosed in the present invention is applicable to a variety of positive and negative electrode materials as mentioned above, in particular to high-voltage positive electrodes, such as one or more of lithium cobalt oxide, nickel-cobalt-manganese ternary materials, lithium-rich manganese-based materials, and lithium nickel manganese oxide; and negative electrodes of metallic lithium and / or metallic lithium alloys.

[0050] The heating copolymerization in the present invention has a temperature of 25 to 80°C.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] The present invention is the first to use a polymer prepared by copolymerizing cyclic anhydride and cyclic acetal as monomers in a specific molar ratio as an electrolyte to assemble a lithium battery. The polymer electrolyte prepared by this method has a T g It is far below room temperature, in a viscous flow state at room temperature, and has better compatibility with the positive and negative electrodes, so it has excellent cycle stability at room temperature, high (80°C) and low temperature (0°C); the amount of lithium salt used in the present invention is far lower than the amount range disclosed in the prior art, but the prepared polymer electrolyte has excellent room temperature ionic conductivity, excellent thermal stability and a wide electrochemical window; it is suitable for a variety of positive and negative electrode materials, and is particularly suitable for high-voltage positive electrodes and lithium metal negative electrodes with high energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 The polymer electrolyte prepared in Example 1 1 H NMR spectrum;

[0054] Figure 2 The polymer electrolyte prepared in Example 1 13 C NMR spectrum;

[0055] Figure 3 The polymer electrolyte prepared in Comparative Example 1 1 H NMR spectrum;

[0056] Figure 4 The polymer electrolyte prepared in Example 4 1 H NMR spectrum;

[0057] Figure 5 The polymer electrolyte prepared in Comparative Example 3 1 H NMR spectrum;

[0058] Figure 6 FT-IR spectrum of the polymer electrolyte prepared in Comparative Example 3;

[0059] Figure 7 The Li / PE / Li symmetric battery assembled in this embodiment 13 was heated at 25°C and 1 mA / cm 2 Lithium deposition / stripping curves;

[0060] Figure 8 1 is the room temperature ionic conductivity curve of the polymer electrolyte prepared at different lithium salt molar ratios in Example 1 and Examples 20 to 25. DETAILED DESCRIPTION

[0061] The specific implementation method of the present invention is further described below in conjunction with examples. It should be noted here that the specific implementation method described here is only for illustrating and explaining the present invention, and is not limited to the present invention.

[0062] The present invention performs relevant characterization on the polymer obtained by ring-opening polymerization: for button batteries obtained by assembling polymers prepared by an in-situ copolymerization method, the batteries are disassembled after sufficient polymerization under required reaction conditions, and a proper amount of polymer electrolyte is taken for relevant tests; for polymer electrolytes prepared by an ex-situ copolymerization method, a proper amount of polymer electrolyte can be directly taken for relevant tests.

[0063] The present invention utilizes 13 CNMR, 1 HNMR and FT-IR were used to characterize the structure of polymer electrolytes;

[0064] The polymer electrolyte was subjected to thermogravimetric testing using a Perkin-Elmer Pyris 1 instrument. The sample was heated from room temperature to 500 °C at a rate of 10 °C / min in a N2 atmosphere;

[0065] The glass transition temperature of the polymer electrolyte was tested using a DSCQ200 instrument. The sample was heated from room temperature to 80°C at a rate of 5°C / min in a N2 atmosphere, then cooled to -80°C at a rate of 5°C / min, and finally heated to 80°C at a rate of 5°C / min.

[0066] The present invention conducts electrochemical characterization on the polymer electrolytes prepared by polymerization in each embodiment or comparative example, and the specific test is described as follows:

[0067] The present invention uses an electrochemical workstation (Shanghai Chenhua Instrument Co., Ltd.) to test the electrochemical window using linear sweep voltammetry. Linear sweep voltammetry (LSV) is to apply a linear potential scan (i.e., the potential is linearly related to time) between the working electrode and the reference electrode of the battery, record the current change on the working electrode caused by the voltage, and obtain a voltage-current curve. The present invention uses SS as the working electrode, Li as the reference electrode and the counter electrode, and uses the electrolyte system to be tested to assemble a semi-blocked battery for LSV testing. The scanning range is OCV~6.5V (vs.Li + / Li), scanning rate 1mV s -1 .

[0068] In the present invention, an electrochemical workstation (Shanghai Chenhua Instrument Co., Ltd.) was used to test the ionic conductivity of the electrolyte using the AC impedance method. The electrolyte system to be tested was assembled into a blocking battery SS / PE / SS for electrochemical AC impedance spectroscopy testing. The test frequency range was 0.1 Hz to 10 6 Hz, amplitude 10mV; after testing the AC impedance, the ionic conductivity of the polymer electrolyte was calculated.

[0069] In the present invention, solid button batteries with different positive and negative electrode materials are assembled, and the polymer battery is tested at different temperatures within a certain voltage range and current density using a blue battery testing system to collect parameters such as voltage platform, specific capacity, and cycle stability.

[0070] Example 1

[0071] Under argon atmosphere, glutaric anhydride (GA), lithium trifluoromethanesulfonyl imide (LiTFSI), and BF3 were dissolved in 1,3-dioxolane (DOL), and stirred at 20°C for 1h to mix evenly to obtain a copolymer precursor solution, wherein the molar ratio of GA / DOL / LiTFSI / BF3 was 100 / 100 / 10 / 1. 0.20mL of the above copolymer precursor solution was injected into a glass fiber separator with a thickness of 420μm for full infiltration; then, lithium iron phosphate (LFP) was used as the positive electrode and lithium metal as the negative electrode, and the glass fiber separator soaked in the copolymer precursor solution was placed between the positive and negative electrodes for packaging; the assembled battery was heated at 35°C for 12h.

[0072] Figure 1 and Figure 2 are respectively the polymer electrolyte prepared in this embodiment 1 H NMR spectra and 13 C-NMR diagram. By observing the two diagrams, it can be confirmed that the fully alternating copolymerization product of glutaric anhydride and 1,3-dioxolane was prepared in this example.

[0073] It was observed that the polymer electrolyte was in a viscous flow state at room temperature. The T g is -46.43°C, therefore, the compatibility between the polymer electrolyte and the positive and negative electrodes is better.

[0074] The room temperature ionic conductivity, electrochemical window and thermal decomposition temperature data of the polymer electrolyte prepared in this example are listed in Table 1 below.

[0075] The LFP / PE / Li full battery assembled in this embodiment was charged to 4.0V at 0°C, 25°C and 80°C at a rate of 0.1C for charge and discharge cycle tests. The test results at 0°C and 25°C are listed in Tables 2 and 3 below, and the test results at 80°C are listed in Table 4 below.

[0076] Comparative Example 1

[0077] The preparation process is basically the same as that in Example 1, except that:

[0078] No glutaric anhydride was added when preparing the copolymer precursor solution.

[0079] Figure 3 The polymer electrolyte prepared in this comparative example 1 HNMR chart. By observing the chart, it can be confirmed that the product prepared in this comparative example is a ring-opening homopolymerization product of 1,3-dioxolane.

[0080] It was observed that the polymer electrolyte prepared in this comparative example was in a crystalline state at room temperature.

[0081] The room temperature ionic conductivity, electrochemical window and thermal decomposition temperature data of the polymer electrolyte prepared in this comparative example are listed in the following Table 1.

[0082] The LFP / PE / Li full battery assembled in this comparative example was charged to 4.0V at 0°C, 25°C and 80°C at a rate of 0.1C for charge and discharge cycle tests. The test results at 0°C and 25°C are listed in Tables 2 and 3 below, and the test results at 80°C are listed in Table 4 below.

[0083] By comparing the performance data of the polymer electrolytes prepared in Example 1 and Comparative Example 1, it can be found that the introduction of ester bonds by acid anhydride in Example 1 improves the room temperature ionic conductivity and electrochemical window of the polymer electrolyte, and also greatly improves its heat resistance; and by comparing the cycle stability of the full batteries assembled from the two, it can be found that the cycle stability of Example 1 is greatly improved, which can be attributed to the introduction of two functional groups to improve the chemical stability between the polymer electrolyte and the electrode, and effectively inhibit the redox reaction between the electrolyte and the electrode.

[0084] Example 2

[0085] The preparation process is basically the same as that in Example 1, except that:

[0086] The molar ratio of GA / DOL / LiTFSI / BF3 was replaced to 100 / 200 / 15 / 1.

[0087] According to nuclear magnetic resonance testing, the polymer electrolyte prepared in this embodiment includes a fully alternating copolymerization product of glutaric anhydride and 1,3-dioxolane and a homopolymerization product of 1,3-dioxolane.

[0088] It was observed that the polymer electrolyte prepared in this example was in an amorphous state at room temperature. The T gis -50.29°C, therefore, the compatibility between the polymer electrolyte and the positive and negative electrodes is better.

[0089] The room temperature ionic conductivity, electrochemical window and thermal decomposition temperature data of the polymer electrolyte prepared in this example are listed in Table 1 below.

[0090] The LFP / PE / Li full battery assembled in this embodiment was charged to 4.0V at 0°C and 25°C at a rate of 0.1C for charge and discharge cycle tests. The test results are listed in Tables 2 and 3 below.

[0091] By comparing the data of Example 1 with that of Example 2, it can be found that when the cyclic acetal is in excess, the room temperature ionic conductivity, electrochemical window and thermal decomposition temperature of the polymer electrolyte prepared are all reduced.

[0092] Comparative Example 2

[0093] The preparation process is basically the same as that in Example 1, except that:

[0094] The molar ratio of GA / DOL / LiTFSI / BF3 was replaced to 100 / 500 / 30 / 1.

[0095] The room temperature ionic conductivity, electrochemical window and thermal decomposition temperature data of the polymer electrolyte prepared in this comparative example are listed in the following Table 1.

[0096] The LFP / PE / Li full battery assembled in this comparative example was charged to 4.0V at 0°C and 25°C at a rate of 0.1C for charge and discharge cycle tests. The test results are listed in Tables 2 and 3 below.

[0097] Example 3

[0098] Under argon atmosphere, glutaric anhydride (GA), lithium trifluoromethanesulfonyl imide (LiTFSI), 1,3-dioxolane (DOL), and BF3 were added to a 10 mL pressure tube in sequence, and the pressure tube was placed in a 35°C oil bath for reaction for 2 hours to obtain a polymer electrolyte, wherein the molar ratio of GA / DOL / LiTFSI / BF3 was 100 / 100 / 10 / 1. 1 g of the above polymer electrolyte was fully dissolved in an acetonitrile solution to obtain a polymer electrolyte mixed solution. A glass fiber diaphragm was placed in a mold, and the polymer electrolyte mixed solution was injected. After the solvent was thoroughly dried, a glass fiber diaphragm adsorbed with a polymer electrolyte was obtained. Then, lithium iron phosphate (LFP) was used as the positive electrode and lithium metal as the negative electrode. The glass fiber diaphragm adsorbed with the polymer electrolyte was placed between the positive and negative electrodes and then packaged to obtain an assembled battery.

[0099] The room temperature ionic conductivity, electrochemical window and thermal decomposition temperature data of the polymer electrolyte prepared in this example are listed in Table 1 below.

[0100] The LFP / PE / Li full battery assembled in this embodiment was charged to 4.0V at 0°C and 25°C at a rate of 0.1C for charge and discharge cycle tests. The test results are listed in Tables 2 and 3 below.

[0101] Example 4

[0102] Under argon atmosphere, glutaric anhydride (GA) and lithium difluorooxalatoborate (LiDFOB) were dissolved in 1,3-dioxane (DOX), and stirred at 20°C for 1h to obtain a copolymer precursor solution, wherein the molar ratio of GA / DOL / LiDFOB was 100 / 100 / 10. 0.03mL of the above copolymer precursor solution was injected into a cellulose diaphragm with a thickness of 20μm for full infiltration; then lithium cobalt oxide (LCO) was used as the positive electrode and lithium metal as the negative electrode, and the diaphragm infiltrated with the copolymer precursor solution was placed between the positive and negative electrodes for packaging; the assembled battery was heated at 80°C for 24h.

[0103] Figure 4 The polymer electrolyte prepared in this example is 1 H-NMR graph, observation of the graph can confirm that the present embodiment obtains a fully alternating copolymerization product of GA and DOX with a clear structure. The room temperature ionic conductivity, electrochemical window and thermal decomposition temperature data of the polymer electrolyte prepared in this embodiment are listed in the following Table 1.

[0104] The LCO / PE / Li full battery assembled in this embodiment was charged to 4.4V at 0°C, 25°C and 80°C at a rate of 0.1C for charge and discharge cycle tests. The test results at 0°C and 25°C are listed in Tables 2 and 3 below.

[0105] Comparative Example 3

[0106] The preparation process is basically the same as that in Example 4, except that:

[0107] The molar ratio of GA / DOX / LiDFOB was changed to 120 / 100 / 10.

[0108] Figure 5 The polymer electrolyte prepared in this comparative example 1 HNMR graph. By observing the graph, it can be confirmed that the fully alternating copolymerization product of GA and DOX was prepared in this example, but a small amount of glutaric anhydride monomer remained.

[0109] Figure 6 This is the FT-IR spectrum of the polymer electrolyte prepared in this comparative example. The characterization results also show that glutaric anhydride monomers still remain in the polymer electrolyte.

[0110] Combination Figures 5-6This shows that although the alternating copolymer product can be obtained by adding an excess of cyclic anhydride monomer, the excess anhydride remains on the separator in a solid state, which greatly reduces the performance of the battery.

[0111] The room temperature ionic conductivity, electrochemical window and thermal decomposition temperature data of the polymer electrolyte prepared in this comparative example are listed in the following Table 1.

[0112] By comparing the data of Example 4 with that of Comparative Example 3, it can be seen that the electrochemical window and thermal decomposition temperature of the prepared polymer electrolyte are significantly reduced due to the residual glutaric anhydride monomer.

[0113] The LCO / PE / Li full battery assembled in this comparative example was charged to 4.4V at 0°C and 25°C at a rate of 0.1C for charge and discharge cycle tests. The test results are listed in Tables 2 and 3 below.

[0114] Comparative Example 4

[0115] The preparation process is basically the same as that in Example 4, except that:

[0116] The molar ratio of GA / DOX / LiDFOB was changed to 100 / 120 / 10.

[0117] The room temperature ionic conductivity, electrochemical window and thermal decomposition temperature data of the polymer electrolyte prepared in this comparative example are listed in the following Table 1.

[0118] By comparing the data of Example 4 with that of Comparative Example 4, it can be seen that the electrochemical window and thermal decomposition temperature of the prepared polymer electrolyte are significantly reduced due to the slight excess of DOX.

[0119] The LCO / PE / Li full battery assembled in this comparative example was charged to 4.4V at 0°C and 25°C at a rate of 0.1C for charge and discharge cycle tests. The test results are listed in Tables 2 and 3 below.

[0120] Embodiments 5 to 7

[0121] The preparation process is basically the same as that in Example 4, except that:

[0122] The lithium salt was replaced with equimolar amounts of lithium hexafluorophosphate, lithium difluorophosphate and lithium tetrafluoroborate in sequence.

[0123] The room temperature ionic conductivity, electrochemical window and thermal decomposition temperature data of the polymer electrolyte prepared in each example are listed in Table 1 below.

[0124] Example 8

[0125] The preparation process is basically the same as that in Example 4, except that:

[0126] The cyclic anhydride was replaced sequentially with an equimolar amount of thioglycolic anhydride.

[0127] The room temperature ionic conductivity, electrochemical window and thermal decomposition temperature data of the polymer electrolyte prepared in this example are listed in Table 1 below.

[0128] The full battery assembled in this embodiment was charged to 4.4V at 0°C and 25°C at a rate of 0.1C for charge and discharge cycle tests. The test results are listed in Tables 2 and 3 below.

[0129] Example 9

[0130] Under argon atmosphere, 3-methylglutaric anhydride (3-MGA), lithium difluorooxalatoborate (LiDFOB), and 1,3-dioxane (DOX) were added to a 10 mL pressure tube in sequence, and the pressure tube was placed in an 80 ° C oil bath for 24 hours to obtain a polymer electrolyte, wherein the molar ratio of 3-MGA / DOX / LiDFOB was 100 / 100 / 10. 1 g of the above polymer electrolyte was fully dissolved in an acetonitrile solution to obtain a polymer electrolyte mixed solution. A glass fiber diaphragm was placed in a mold, and the polymer electrolyte mixed solution was injected. After the solvent was thoroughly dried, a glass fiber diaphragm adsorbed with a polymer electrolyte was obtained. Then, lithium iron phosphate (LFP) was used as the positive electrode and lithium metal was used as the negative electrode. The glass fiber diaphragm adsorbed with the polymer electrolyte was placed between the positive and negative electrodes and packaged to obtain an assembled battery.

[0131] The room temperature ionic conductivity, electrochemical window and thermal decomposition temperature data of the polymer electrolyte prepared in this example are listed in Table 1 below.

[0132] The full battery assembled in this embodiment was charged to 4.0V at 0°C and 25°C at a rate of 0.1C for charge and discharge cycle tests. The test results are listed in Tables 2 and 3 below.

[0133] Embodiments 10 to 12

[0134] The preparation process is basically the same as that in Example 9, except that:

[0135] The cyclic anhydride was replaced with equimolar amounts of 3,3-dimethylglutaric anhydride, 2,2-dimethylglutaric anhydride and diglycolic anhydride in sequence.

[0136] The room temperature ionic conductivity, electrochemical window and thermal decomposition temperature data of the polymer electrolyte prepared in each example are listed in Table 1 below.

[0137] The full batteries assembled in each embodiment were charged to 4.0V at 0°C and 25°C at a rate of 0.1C for charge and discharge cycle tests. The test results are listed in Table 2 below.

[0138] Example 13

[0139] The preparation process is basically the same as that in Example 9, except that:

[0140] The cyclic anhydride was replaced sequentially with an equimolar amount of hexafluoroglutaric anhydride.

[0141] The room temperature ionic conductivity, electrochemical window and thermal decomposition temperature data of the polymer electrolyte prepared in this example are listed in Table 1 below.

[0142] The full battery assembled in this embodiment was charged to 4.0V at 0°C and 25°C at a rate of 0.1C for charge and discharge cycle tests. The test results are listed in Table 2 below.

[0143] Figure 7 The Li / PE / Li symmetric battery assembled for this example was heated at 25°C and 1 mA / cm 2 The lithium deposition / stripping curve under the above conditions is shown. By observing the curve, it can be found that the battery assembled in this embodiment can be stably cycled for more than 1000 hours and has excellent lithium metal compatibility. This result shows that the polymer electrolyte prepared by introducing fluorinated cyclic anhydride monomers into the reaction system of the present invention has excellent electrochemical stability, no safety hazard of electrolyte leakage, and excellent battery long cycle performance.

[0144] Comparing Examples 4 with 8 to 13, the preferred cyclic anhydride is selected from glutaric anhydride and / or hexafluoroglutaric anhydride, and the room temperature ionic conductivity and electrochemical window of the polymer electrolyte prepared by the two are higher.

[0145] Embodiments 14 to 15

[0146] The preparation process is basically the same as that in Example 9, except that:

[0147] The cyclic anhydride was replaced with equimolar amounts of succinic anhydride and 2,3-dimethylmaleic anhydride, respectively.

[0148] The room temperature ionic conductivity, electrochemical window and thermal decomposition temperature data of the polymer electrolyte prepared in each example are listed in Table 1 below.

[0149] Embodiments 16 to 19

[0150] The preparation process is basically the same as that in Example 1, except that:

[0151] The cyclic acetal was replaced with equimolar amounts of 4-methyl-1,3-dioxane, 1,3-dioxetane, 1,3-dioxoctane and 1,3,6-trioxoctane in sequence.

[0152] The room temperature ionic conductivity, electrochemical window and thermal decomposition temperature data of the polymer electrolyte prepared in each example are listed in Table 1 below.

[0153] The full batteries assembled in each embodiment were charged to 4.0V at 0°C and 25°C at a rate of 0.1C for charge and discharge cycle tests. The test results are listed in Table 2 below.

[0154] Embodiments 20 to 25

[0155] The preparation process is basically the same as that in Example 1, except that:

[0156] The ratio of the molar number of lithium salt to the total molar number of monomers was changed to 0.02, 0.08, 0.12, 0.30, 0.50 and 0.70, respectively.

[0157] The room temperature ionic conductivity of the polymer electrolyte prepared in each example is listed in Table 5 below.

[0158] Table 5

[0159]

[0160] Figure 8 The room temperature ionic conductivity curves of polymer electrolytes prepared at different lithium salt molar ratios show that the conductivity changes with the lithium salt concentration (the ratio of the molar number of lithium salt to the monomer) and has two extreme values, between 0.03 and 0.12. The conductivity increases first and then decreases with the increase of lithium salt content, but both reach 10 -4 S / cm, the conductivity shows a trend of decreasing first and then increasing as the lithium salt concentration continues to increase, but the conductivity is still low. -4 S / cm level, but the lithium salt content here is relatively large, which will greatly increase the production cost.

[0161] Table 1

[0162]

[0163] Table 2

[0164]

[0165]

[0166] Table 3

[0167]

[0168]

[0169] Table 4

[0170]

[0171] aThe capacity of the battery assembled in this comparative example decayed to 0 after 3 cycles and could not be charged and discharged normally.

[0172] The applicant declares that the present invention illustrates the detailed method of the present invention through the above embodiments, but the present invention is not limited to the above detailed method.

Claims

1. A method for assembling a lithium battery from a polymer electrolyte, characterized in that: Including in situ copolymerization or ex situ copolymerization; The in-situ copolymerization comprises the following steps: The cyclic anhydride, cyclic acetal, lithium salt and a catalyst which can be optionally added are mixed to obtain a precursor solution, the separator soaked in the precursor solution is placed between the positive electrode and the negative electrode, and after assembly, the separator is heated and copolymerized to prepare an in-situ copolymerized lithium battery; The heterotopic copolymerization comprises the following steps: Cyclic anhydride, cyclic acetal, lithium salt and a catalyst which can be optionally added are mixed to obtain a precursor solution, and a polymer electrolyte is obtained after heating copolymerization, and the polymer electrolyte is dissolved in an organic solvent to obtain a mixed solution, and a diaphragm soaked in the mixed solution is vacuum dried and placed between a positive electrode and a negative electrode, and an ex situ copolymerized lithium battery is obtained after assembly; In the in-situ copolymerization or the hetero-situ copolymerization, the molar ratio of the cyclic anhydride to the cyclic acetal is 1:1-2.

2. The method for assembling a lithium battery from a polymer electrolyte according to claim 1, characterized in that: In the in-situ copolymerization or the ex-situ copolymerization: The cyclic anhydride is selected from a five-membered cyclic anhydride and / or a six-membered cyclic anhydride; The five-membered ring anhydride is selected from one or more of maleic anhydride, succinic anhydride, 2,3-dimethylmaleic anhydride, 2,3-dichloromaleic anhydride, 2,3-dibromomaleic anhydride, 2,3-difluoromaleic anhydride, methylsuccinic anhydride, phthalic anhydride, and 3,4,5,6-tetrahydrophthalic anhydride; The six-membered cyclic acid anhydride is selected from one or more of glutaric anhydride, diglycolic anhydride, thioglycolic anhydride, 3-methylglutaric anhydride, 3,3-dimethylglutaric anhydride, 2,2-dimethylglutaric anhydride, 3-isobutylglutaric anhydride, hexafluoroglutaric anhydride, 3,3-tetramethyleneglutaric anhydride, and 1,1-cyclohexyldiacetic anhydride; The cyclic acetal is selected from one or more of a five-membered cyclic acetal, a six-membered cyclic acetal, a seven-membered cyclic acetal, and an eight-membered cyclic acetal; The five-membered ring acetal is selected from one or more of 1,3-dioxolane, 2,2-dimethyl-1,3-dioxolane, 2-chloromethyl-1,3-dioxolane, 2-propyl-4-methyl-1,3-dioxolane, 2-(trifluoromethyl)dioxolane, 4-methyl-2-pentyl-1,3-dioxolane, 2-bromomethyl-1,3-dioxolane and 2-(2-bromoethyl)-1,3-dioxane; The six-membered ring acetal is selected from one or more of 1,3-dioxane, 4-methyl-1,3-dioxane, glycerol formal, 2-(2-bromoethyl)-1,3-dioxane, and 4-phenyl-1,3-dioxane; The seven-membered ring acetal is selected from one or more of 1,3-dioxepin, 2-methylene-1,3-dioxane, and cis-4,7-dihydro-1,3-dioxepin; The eight-membered ring acetal is selected from 1,3-dioxoctane and / or 1,3,6-trioxoctane; The lithium salt is selected from one or more of lithium bis(oxalatoborate), lithium tetrafluoroborate, lithium hexafluorophosphate, lithium difluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl imide), lithium difluorooxalatoborate, lithium difluorophosphate, lithium trifluorosulfonyl imide, lithium bis(trifluoromethanesulfonate), and lithium bis(trifluoromethanesulfonyl imide); The catalyst is selected from Lewis acids or protic acids.

3. The method for assembling a lithium battery from a polymer electrolyte according to claim 2, characterized in that: The cyclic anhydride is selected from six-membered cyclic anhydrides; The cyclic acetal is selected from one or more of 1,3-dioxolane, 2,2-dimethyl-1,3-dioxolane, 2-propyl-4-methyl-1,3-dioxolane, 4-methyl-2-pentyl-1,3-dioxolane, 1,3-dioxane, 4-methyl-1,3-dioxane, 1,3-dioxepane, 1,3-dioxocane and / or 1,3,6-trioxocane.

4. The method for assembling a lithium battery from a polymer electrolyte according to claim 3, characterized in that: The cyclic anhydride is selected from one or more of glutaric anhydride, thioglycolic anhydride, 3-methylglutaric anhydride, 3,3-dimethylglutaric anhydride, 2,2-dimethylglutaric anhydride, diglycolic anhydride, and hexafluoroglutaric anhydride; The cyclic acetal is selected from one or more of 1,3-dioxolane, 1,3-dioxane, 4-methyl-1,3-dioxane, 1,3-dioxetane, 1,3-dioxoctane, and 1,3,6-trioxoctane; In the in-situ copolymerization or the hetero-situ copolymerization, the molar ratio of the cyclic anhydride to the cyclic acetal is 1:

1.

5. The method for assembling a lithium battery from a polymer electrolyte according to claim 1, characterized in that: The molar number of the monomer is calculated based on the total molar number of the cyclic anhydride and the cyclic acetal, and the molar ratio of the lithium salt to the monomer is 0.03 to 0.12, or 0.7 to 0.8; The molar ratio of the catalyst to the cyclic anhydride is 1 to 5:100; In the heterotopic copolymerization, the organic solvent is selected from one or more of acetonitrile, acetone, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide.

6. The method for assembling a lithium battery from a polymer electrolyte according to claim 5, characterized in that: The molar ratio of lithium salt to monomer is 0.03 to 0.12; The cyclic anhydride is selected from glutaric anhydride and / or hexafluoroglutaric anhydride; The cyclic acetal is selected from one or more of 1,3-dioxolane, 1,3-dioxane, 1,3-dioxepane, and 1,3-dioxane.

7. The method for assembling a lithium battery from a polymer electrolyte according to claim 1, characterized in that: The cyclic acetal is selected from 1,3-dioxane; The lithium salt is selected from one or more of lithium difluorooxalatoborate, lithium hexafluorophosphate, lithium difluorophosphate, and lithium tetrafluoroborate; the lithium salt is also used as a catalyst, and no additional catalyst needs to be added; The cyclic anhydride and the cyclic acetal are added in equimolar amounts.

8. The method for assembling a lithium battery from a polymer electrolyte according to claim 1, characterized in that: The separator is selected from a porous support material; The porous support material is selected from one or more of glass fiber, cellulose, polyethylene membrane, polypropylene membrane, nylon non-woven membrane, seaweed fiber non-woven membrane, bacterial cellulose, polyimide non-woven membrane, polyamide membrane, spandex membrane, and aramid membrane; The positive electrode is selected from one or more of lithium cobalt oxide, lithium cobalt phosphate, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel manganese oxide, lithium nickel oxide, lithium manganese-rich base, nickel cobalt manganese ternary material, sulfur positive electrode, lithium fluorophosphate, lithium vanadium fluorophosphate, lithium iron fluorophosphate, lithium manganese oxide, and lithium manganese oxide; The negative electrode is selected from one or more of metallic lithium, metallic lithium alloy, hard carbon, graphite, molybdenum disulfide, lithium titanate, graphene, antimony oxide, and silicon.

9. The method for assembling a lithium battery from a polymer electrolyte according to claim 8, characterized in that: The positive electrode is selected from one or more of lithium cobalt oxide, nickel-cobalt-manganese ternary material, lithium-rich manganese base, and lithium nickel manganese oxide; The negative electrode is selected from metallic lithium and / or metallic lithium alloy.

10. The method for assembling a lithium battery from a polymer electrolyte according to claim 1, characterized in that: The heating copolymerization is carried out at a temperature of 25 to 80°C.

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