Temperature-responsive high-safety lithium ion battery and preparation method thereof
By using in-situ polymerization method inside the lithium-ion battery to form a temperature-responsive composite solid electrolyte, the safety hazards caused by internal short circuit of the battery under external abuse conditions are solved, and the battery is high safety performance and large-scale production that is compatible with existing production processes is achieved.
Patent Information
- Application Number
- CN202411917480.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-24
- Publication Date
- 2025-03-21
AI Technical Summary
Lithium-ion batteries are prone to large-scale internal short circuits under external abuse conditions, resulting in concentrated heat generation, which in turn causes heat release, combustion and explosion of unstable materials, posing serious safety hazards.
By using in-situ polymerization method inside the battery, the temperature-responsive composite solid electrolyte is formed. The electrolyte is stable at room temperature and low temperature, and shrinks when the temperature rises to 80°C, cutting off the connection between the positive and negative electrode materials and the electrolyte to prevent further occurrence of short-circuit exothermic reactions.
It effectively prevents the occurrence of short-circuit exothermic reactions in the battery, improves the safety performance of the battery, and is compatible with the existing liquid lithium-ion battery production process, and does not require additional manufacturing equipment, so as to achieve rapid large-scale production.
Smart Images
Figure BDA0005207153070000101 
Figure HDA0005207153080000011
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a temperature-responsive high-safety lithium ion battery and a preparation method thereof. Background Art
[0002] Driven by the goals of ensuring energy security and addressing climate change, electric vehicles and large-scale energy storage power stations have entered a stage of vigorous development. High-energy-density lithium-ion batteries are a key factor in promoting the large-scale development of electric vehicles and large-scale energy storage power stations. However, in recent years, safety accidents caused by thermal runaway of lithium-ion batteries have brought a huge impact on the development of the industry. The main reason for thermal runaway is that the battery forms a large-scale internal short circuit under external abuse conditions (including puncture, extrusion, collision, high temperature, etc.). The concentrated heat generated by the short circuit causes the internal unstable materials (including high-energy-density positive electrode materials, flammable organic electrolytes, high-temperature and easy-to-shrink diaphragms, highly reactive negative electrode materials, etc.) to further release heat, and then burn and explode. With the further improvement of battery energy density and the emergence of large modular batteries, the demand for improving the safety of lithium-ion batteries has also greatly increased.
[0003] There are two main countermeasures for the safety hazards of lithium-ion batteries: external prevention and control and internal suppression. External prevention and control mainly focuses on developing battery management systems for real-time monitoring and control, reducing the damage to the battery caused by abuse conditions, and can reduce the risk of thermal runaway to a certain extent, but the intrinsic safety hazards of the battery still exist. The intrinsic safety of the battery can be improved to a certain extent by reducing the heat-generating reaction by improving the stability of the internal materials of the battery. At present, technical means such as improving the structural stability of positive and negative electrode materials by coating positive and negative electrode materials, using high-temperature resistant diaphragms, adding flame-retardant electrolyte additives, using solid electrolytes to partially or completely replace liquid electrolytes, and adding functional coatings on the surfaces of positive and negative electrodes can improve the safety of the battery to a certain extent. However, the above technical means to improve the stability of internal battery materials cannot reduce the huge heat generated by the internal short circuit of the battery, and the effect of improving the safety performance of the battery is very limited. At the same time, most of the technical means will have an adverse effect on the electrochemical properties of the battery, especially the rate performance; and will increase the complexity of the battery process flow, and put forward higher requirements for the battery manufacturing process and manufacturing equipment. Further research and development are needed to achieve large-scale application. Summary of the invention
[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a temperature-responsive high-safety lithium-ion battery and a preparation method thereof, which forms a temperature-responsive composite solid electrolyte inside the battery by in-situ polymerization, has temperature-responsive characteristics, can maintain a stable state at room temperature and low temperature, shrinks after the temperature rises to 80°C, cuts off the connection between the positive and negative electrode materials and the electrolyte, disconnects the lithium ion transmission channel, and prevents further occurrence of short-circuit exothermic reactions, effectively solving the problem that the concentrated heat generated by large-scale internal short circuits under existing lithium ion external abuse conditions affects the safety performance of the battery.
[0005] The technical solution of the present invention to solve the above technical problems is as follows: a method for preparing a temperature-responsive high-safety lithium-ion battery is provided, which comprises the following steps in sequence:
[0006] (1) preparing a soft-packaged laminated dry battery cell including a positive electrode, a negative electrode and a separator, and then injecting a precursor solution 1, setting aside, performing a primary formation, and performing a primary exhaust; the precursor solution 1 includes an organic solvent, a lithium salt, a negative thermal expansion inorganic material, and a thermally shrinkable organic material;
[0007] (2) injecting the second precursor solution, setting aside, causing polymerization reaction after heating, secondary formation, aging, secondary exhaust, and volume separation after packaging to obtain a temperature-responsive high-safety lithium-ion battery; the second precursor solution includes a multifunctional polymer monomer, an initiator, an organic solvent, and a lithium salt.
[0008] Furthermore, in step (1), in the soft-pack laminated dry battery cell, the positive electrode is at least one of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide and nickel cobalt manganese ternary materials; the negative electrode is at least one of graphite, silicon carbon and silicon oxygen carbon materials; and the diaphragm is at least one of polyethylene film, polypropylene film, fiber film and ceramic composite film.
[0009] Furthermore, the soft-pack laminated dry battery cell is prepared by the following method: the positive and negative electrode sheets are prepared by slurrying, coating, rolling, slitting, die-cutting and other processes; and the PP / PE composite diaphragm and the positive and negative electrodes are laminated, hot pressed, the tabs are welded, and the aluminum-plastic shell is encapsulated to obtain the dry battery cell.
[0010] Furthermore, in step (1), in the precursor solution 1, the molar concentration of lithium salt is 0.9-1.1 M, and the negative thermal expansion inorganic material and the thermal shrinkage organic material account for 0.5-1.5 wt% and 1.5-3.5 wt% respectively.
[0011] Furthermore, in step (1), the organic solvent is at least one of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, vinylene carbonate, fluoroethylene carbonate, methyl butyrate, ethyl butyrate and ethyl acetate; and the lithium salt is at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium bis(trifluoromethanesulfonyl imide) and lithium bis(fluorosulfonyl imide).
[0012] Furthermore, in step (1), the negative thermal expansion inorganic material is a tungstate, including at least one of niobium tungstate, zirconium tungstate and yttrium tungstate; and the heat shrinkable organic material is at least one of acrylamide, methacrylamide, diacetone acrylamide and N-methyl-2-acrylamide.
[0013] Furthermore, in step (1), the mixture is placed at a temperature of 20-30° C. for 24-48 hours.
[0014] Furthermore, in step (2), in the precursor solution 2, the molar concentration of lithium salt is 0.9-1.1 M, and the proportions of multifunctional polymer monomer and initiator are 8-10 wt% and 0.5-1.5 wt% respectively.
[0015] Furthermore, in step (2), the multifunctional polymer monomer is at least one of pentaerythritol tetraacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, ethoxylated trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate and trimethylolpropane triacrylate; and the initiator is an azo compound, including at least one of azobisisobutyronitrile, dimethyl azobisisobutyrate and azobisisoheptanonitrile.
[0016] Furthermore, in step (2), the organic solvent is at least one of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, vinylene carbonate, fluoroethylene carbonate, methyl butyrate, ethyl butyrate and ethyl acetate; and the lithium salt is at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium bis(trifluoromethanesulfonyl imide) and lithium bis(fluorosulfonyl imide).
[0017] Furthermore, in step (2), the mixture is placed at a temperature of 15-25° C. for 24-48 hours, and the polymerization reaction is carried out at a temperature of 45-75° C. for 4-12 hours.
[0018] Furthermore, in the two precursor solutions, the proportions of the first precursor solution and the second precursor solution are 70-80 wt % and 20-30 wt % respectively.
[0019] The present invention also provides a temperature-responsive high-safety lithium-ion battery prepared by the method for preparing the temperature-responsive high-safety lithium-ion battery.
[0020] The present invention has the following beneficial effects:
[0021] 1. The present invention introduces a temperature response mechanism into the electrolyte, which maintains a stable state at room temperature and low temperature, and shrinks after the temperature rises to 80°C, cutting off the connection between the positive and negative electrode materials and the electrolyte. Figure 1 As shown; prevent the further occurrence of short-circuit exothermic reaction in the battery and improve the safety performance of the battery.
[0022] 2. The present invention solidifies the electrolyte by an in-situ polymerization method, which can inhibit the flow of the electrolyte, avoid leakage of the electrolyte under abuse conditions, enhance the stability of the electrolyte, and improve the safety performance of the battery. In addition, the technical means of in-situ polymerization are well compatible with the existing production process of liquid lithium-ion batteries, do not need to add additional battery manufacturing equipment, do not change the existing battery preparation process, and can quickly achieve large-scale production.
[0023] 3. The present invention provides an in-situ curing technology for step-by-step injection, which effectively solves the battery interface problem, prevents electrolyte leakage, and improves the safety performance of the battery while ensuring the electrochemical performance of the battery. At the same time, the preparation process is compatible with the existing liquid lithium-ion battery production process route, does not require the addition of additional battery manufacturing equipment, and can quickly achieve large-scale production.
[0024] 4. During preparation, the components of precursor solution 1 and precursor solution 2 are cured in situ to form the electrolyte of the battery, in which the organic material will polymerize to form a polymer network. The function of lithium salt is to conduct ions, and the solvent is to dissolve lithium salt. The heat-shrinkable organic material is mainly amides. The network formed by in-situ curing with the multifunctional polymer monomer of precursor solution 2 has heat shrinkage and will shrink to a certain extent at high temperature; at the same time, it contains nitrogen, which is conducive to the formation of nitrogen-containing SEI during the initial formation of the battery, and is beneficial to the rate performance and cycle performance of the battery under normal conditions. Negative thermal expansion inorganic materials are mainly used to further enhance the heat shrinkage of the electrolyte, ensure shrinkage at high temperatures, and cut off the connection between the active material and the electrolyte; at the same time, the composite of inorganic materials and organic materials can enhance the segment movement of the polymer network, which is beneficial to improve the ionic conductivity of the electrolyte and the rate performance of the battery under normal conditions. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 Schematic diagram of the state of a temperature-responsive, high-safety lithium-ion battery at different temperatures. DETAILED DESCRIPTION
[0026] The principles and features of the present invention are described below, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. If no specific conditions are specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.
[0027] Example 1
[0028] A temperature-responsive high-safety lithium-ion battery, the preparation method of which comprises the following steps in sequence:
[0029] (1) A soft-packaged laminated dry battery cell (nickel-cobalt-manganese NCM622 ternary positive electrode and graphite negative electrode) including a positive electrode, a negative electrode and a separator was prepared, and then a precursor solution 1 was injected. The injection environment was a glove box with a water and oxygen content of less than 0.1 ppm. After the injection was completed and the sealing was completed, the mixture was placed at 20° C. for 30 h for initial formation and initial exhaust. The precursor solution 1 was prepared by the following method: 16.0 g of ethylene carbonate, 12.0 g of diethyl carbonate, 12.0 g of ethyl methyl carbonate, 1.0 g of fluoroethylene carbonate, 5.0 g of lithium hexafluorophosphate, 0.3 g of niobium tungstate and 0.7 g of diacetone acrylamide were mixed and injected into an electrolyte bottle, and the mixture was stirred for 4 h to obtain a precursor solution 1.
[0030] (2) Injecting precursor solution 2, the injection environment is a glove box with a water and oxygen content of less than 0.1ppm, and after the injection is completed and sealed, it is allowed to stand and soak for 30 hours at a constant temperature of 20°C, and then heated to 70°C at a heating rate of 1°C / min, and maintained for 2 hours for in-situ polymerization to solidify the electrolyte, perform secondary formation, aging, secondary exhaust, and volume separation after packaging to obtain a temperature-responsive high-safety lithium-ion battery; Precursor solution 1 is prepared by the following method: 4.0g of ethylene carbonate, 3.0g of diethyl carbonate, 3.0g of ethyl methyl carbonate, 0.2g of vinylene carbonate, 1.5g of lithium hexafluorophosphate, 1.4g of pentaerythritol tetraacrylate, and 0.15g of initiator azobisisobutyronitrile are mixed and injected into the electrolyte bottle, and fully stirred for 4h to obtain precursor solution 2.
[0031] Example 2
[0032] A temperature-responsive high-safety lithium-ion battery, the preparation method of which comprises the following steps in sequence:
[0033] (1) A soft-pack laminated dry battery cell (nickel-cobalt-manganese NCM811 ternary positive electrode and graphite negative electrode) including a positive electrode, a negative electrode and a separator was prepared, and then a precursor solution 1 was injected. The injection environment was a glove box with a water and oxygen content of less than 0.1 ppm. After the injection was completed and the sealing was completed, the precursor solution was placed at 20° C. for 30 hours for initial formation and initial exhaust. The precursor solution 1 was prepared by the following method: 16.0 g of ethylene carbonate, 12.0 g of diethyl carbonate, 12.0 g of ethyl methyl carbonate, 1.0 g of fluoroethylene carbonate, 5.0 g of lithium hexafluorophosphate, 0.3 g of niobium tungstate and 0.7 g of diacetone acrylamide were mixed and injected into an electrolyte bottle, and the mixture was stirred for 4 hours to obtain a precursor solution 1.
[0034] (2) Injecting precursor solution 2, the injection environment is a glove box with a water and oxygen content of less than 0.1ppm, and after the injection is completed and sealed, it is allowed to stand and soak for 30 hours at a constant temperature of 20°C, and then heated to 70°C at a heating rate of 1°C / min, and maintained for 2 hours for in-situ polymerization to solidify the electrolyte, perform secondary formation, aging, secondary exhaust, and volume separation after packaging to obtain a temperature-responsive high-safety lithium-ion battery; Precursor solution 1 is prepared by the following method: 4.0g of ethylene carbonate, 3.0g of diethyl carbonate, 3.0g of ethyl methyl carbonate, 0.2g of vinylene carbonate, 1.5g of lithium hexafluorophosphate, 1.4g of pentaerythritol tetraacrylate, and 0.15g of initiator azobisisobutyronitrile are mixed and injected into the electrolyte bottle, and fully stirred for 4h to obtain precursor solution 2.
[0035] Example 3
[0036] A temperature-responsive high-safety lithium-ion battery, the preparation method of which comprises the following steps in sequence:
[0037] (1) A soft-packaged laminated dry battery cell (nickel-cobalt-manganese NCM622 ternary positive electrode and silicon-carbon negative electrode) including a positive electrode, a negative electrode and a separator was prepared, and then a precursor solution 1 was injected. The injection environment was a glove box with a water and oxygen content of less than 0.1 ppm. After the injection was completed and the sealing was completed, the mixture was placed at 20° C. for 30 h for initial formation and initial exhaust. The precursor solution 1 was prepared by the following method: 16.0 g of ethylene carbonate, 12.0 g of diethyl carbonate, 12.0 g of ethyl methyl carbonate, 1.0 g of fluoroethylene carbonate, 5.0 g of lithium hexafluorophosphate, 0.3 g of niobium tungstate and 0.7 g of diacetone acrylamide were mixed and injected into an electrolyte bottle, and the mixture was stirred for 4 h to obtain a precursor solution 1.
[0038] (2) Injecting precursor solution 2, the injection environment is a glove box with a water and oxygen content of less than 0.1ppm, and after the injection is completed and sealed, it is allowed to stand and soak for 30 hours at a constant temperature of 20°C, and then heated to 70°C at a heating rate of 1°C / min, and maintained for 2 hours for in-situ polymerization to solidify the electrolyte, perform secondary formation, aging, secondary exhaust, and volume separation after packaging to obtain a temperature-responsive high-safety lithium-ion battery; Precursor solution 1 is prepared by the following method: 4.0g of ethylene carbonate, 3.0g of diethyl carbonate, 3.0g of ethyl methyl carbonate, 0.2g of vinylene carbonate, 1.5g of lithium hexafluorophosphate, 1.4g of pentaerythritol tetraacrylate, and 0.15g of initiator azobisisobutyronitrile are mixed and injected into the electrolyte bottle, and fully stirred for 4h to obtain precursor solution 2.
[0039] Example 4
[0040] A temperature-responsive high-safety lithium-ion battery, the preparation method of which comprises the following steps in sequence:
[0041] (1) A soft-pack laminated dry battery cell (nickel-cobalt-manganese NCM622 ternary positive electrode and graphite negative electrode) including a positive electrode, a negative electrode and a separator was prepared, and then a precursor solution 1 was injected. The injection environment was a glove box with a water and oxygen content of less than 0.1 ppm. After the injection was completed and the sealing was completed, the precursor solution was placed at 20° C. for 30 hours for initial formation and initial exhaust. The precursor solution 1 was prepared by the following method: 16.0 g of ethylene carbonate, 12.0 g of diethyl carbonate, 12.0 g of ethyl methyl carbonate, 1.0 g of fluoroethylene carbonate, 5.0 g of lithium hexafluorophosphate, 0.3 g of zirconium tungstate and 0.7 g of acrylamide were mixed and injected into an electrolyte bottle, and the mixture was stirred for 4 hours to obtain a precursor solution 1.
[0042] (2) Injecting precursor solution 2, the injection environment is a glove box with a water and oxygen content of less than 0.1ppm, and after the injection is completed and sealed, it is allowed to stand and soak for 30 hours at a constant temperature of 20°C, and then heated to 70°C at a heating rate of 1°C / min, and maintained for 2 hours for in-situ polymerization to solidify the electrolyte, perform secondary formation, aging, secondary exhaust, and volume separation after packaging to obtain a temperature-responsive high-safety lithium-ion battery; Precursor solution 1 is prepared by the following method: 4.0g of ethylene carbonate, 3.0g of diethyl carbonate, 3.0g of ethyl methyl carbonate, 0.2g of vinylene carbonate, 1.5g of lithium hexafluorophosphate, 1.4g of pentaerythritol tetraacrylate, and 0.15g of initiator azobisisobutyronitrile are mixed and injected into the electrolyte bottle, and fully stirred for 4h to obtain precursor solution 2.
[0043] Example 5
[0044] A temperature-responsive high-safety lithium-ion battery, the preparation method of which comprises the following steps in sequence:
[0045] (1) A soft-packaged laminated dry battery cell (nickel-cobalt-manganese NCM622 ternary positive electrode and graphite negative electrode) including a positive electrode, a negative electrode and a separator was prepared, and then a precursor solution 1 was injected. The injection environment was a glove box with a water and oxygen content of less than 0.1 ppm. After the injection was completed and the sealing was completed, the mixture was placed at 20° C. for 30 h for initial formation and initial exhaust. The precursor solution 1 was prepared by the following method: 16.0 g of ethylene carbonate, 12.0 g of diethyl carbonate, 12.0 g of ethyl methyl carbonate, 1.0 g of fluoroethylene carbonate, 5.0 g of lithium hexafluorophosphate, 0.3 g of niobium tungstate and 0.7 g of diacetone acrylamide were mixed and injected into an electrolyte bottle, and the mixture was stirred for 4 h to obtain a precursor solution 1.
[0046] (2) Injecting precursor solution 2, the injection environment is a glove box with a water and oxygen content of less than 0.1ppm, and after the injection is completed and sealed, it is allowed to stand and soak for 30 hours at a constant temperature of 20°C, and then heated to 70°C at a rate of 1°C / min, and maintained for 2 hours for in-situ polymerization to solidify the electrolyte, perform secondary formation, aging, secondary exhaust, and volume separation after packaging to obtain a temperature-responsive high-safety lithium-ion battery; Precursor solution 1 is prepared by the following method: 4.0g of ethylene carbonate, 3.0g of diethyl carbonate, 3.0g of ethyl methyl carbonate, 0.2g of vinylene carbonate, 1.5g of lithium hexafluorophosphate, 1.4g of polyethylene glycol diacrylate, and 0.15g of initiator azobisisobutyronitrile are mixed and injected into the electrolyte bottle, and stirred for 4 hours to obtain precursor solution 2.
[0047] Example 6
[0048] A temperature-responsive high-safety lithium-ion battery, the preparation method of which comprises the following steps in sequence:
[0049] (1) A soft-packaged laminated dry battery cell (nickel-cobalt-manganese NCM622 ternary positive electrode and graphite negative electrode) including a positive electrode, a negative electrode and a separator was prepared, and then a precursor solution 1 was injected. The injection environment was a glove box with a water and oxygen content of less than 0.1 ppm. After the injection was completed and the sealing was completed, the mixture was placed at 20° C. for 30 h for initial formation and initial exhaust. The precursor solution 1 was prepared by the following method: 16.0 g of ethylene carbonate, 12.0 g of diethyl carbonate, 12.0 g of ethyl methyl carbonate, 1.0 g of fluoroethylene carbonate, 5.0 g of lithium hexafluorophosphate, 0.3 g of niobium tungstate and 0.7 g of diacetone acrylamide were mixed and injected into an electrolyte bottle, and the mixture was stirred for 4 h to obtain a precursor solution 1.
[0050] (2) Injecting precursor solution 2, the injection environment is a glove box with a water and oxygen content of less than 0.1ppm, and after the injection is completed and sealed, it is allowed to stand and soak for 30 hours at a constant temperature of 20°C, and the temperature is raised to 60°C at a heating rate of 1°C / min, and maintained for 6 hours for in-situ polymerization to solidify the electrolyte, perform secondary formation, aging, secondary exhaust, and volume separation after packaging to obtain a temperature-responsive high-safety lithium-ion battery; Precursor solution 1 is prepared by the following method: 4.0g of ethylene carbonate, 3.0g of diethyl carbonate, 3.0g of ethyl methyl carbonate, 0.2g of vinylene carbonate, 1.5g of lithium hexafluorophosphate, 1.4g of pentaerythritol tetraacrylate, and 0.15g of initiator azobisisobutyronitrile are mixed and injected into the electrolyte bottle, and stirred for 4 hours to obtain precursor solution 2.
[0051] Comparative Example 1
[0052] The difference between Comparative Example 1 and Example 1 is that in step (2), no in-situ polymerization is performed to solidify the electrolyte.
[0053] Comparative Example 2
[0054] A lithium ion battery, the preparation method of which comprises the following steps:
[0055] A soft-packaged laminated dry battery cell (nickel-cobalt-manganese NCM622 ternary positive electrode, graphite negative electrode) including a positive electrode, a negative electrode and a separator is prepared, and then an electrolyte is injected. The injection environment is a glove box with a water and oxygen content of less than 0.1 ppm. After the injection is completed and the sealing is completed, it is placed at 25°C for 30 hours, formed, aged, exhausted, packaged and then divided to obtain a lithium-ion battery; the electrolyte is prepared by the following method: 20.0 g of ethylene carbonate, 15.0 g of diethyl carbonate, 15.0 g of ethyl methyl carbonate, 2.5 g of fluoroethylene carbonate, 0.2 g of vinylene carbonate, and 7.5 g of lithium hexafluorophosphate are mixed and injected into an electrolyte bottle, and the mixture is fully stirred for 4 hours to obtain an electrolyte.
[0056] Test example
[0057] The lithium ion batteries obtained in Examples 1-6 and Comparative Examples 1-2 were subjected to cycle and rate electrochemical performance tests and needle puncture and heating safety performance tests, as shown in Table 1.
[0058] The specific experimental process is as follows:
[0059] (1) Voltage and internal resistance test at different temperatures: At 25±3℃, the battery is charged at a constant current of 1C to 4.2V, then switched to constant voltage (4.2V) charging until the charging current is less than 0.05C and then left for 0.5h; first test the battery voltage and internal resistance at 25±3℃; then test the battery voltage and internal resistance at 85±3℃.
[0060] (2) Cycle test: At 25±3℃, the battery is charged at a constant current of 1C to 4.2V, then switched to constant voltage (4.2V) charging until the charging current is less than 0.05C and then left for 0.5h; discharged at a constant current of 1C to a termination voltage of 2.75V and left for 0.5h, which counts as one cycle. The cycle is repeated 300 times and the discharge capacity is recorded.
[0061] (3) Rate test: At 25±3℃, the battery was charged at a constant current of 0.33C to 4.2V, then switched to constant voltage (4.2V) charging until the charging current was less than 0.05C and stopped, and left for 0.5h; discharged at a constant current of 5C to a termination voltage of 2.75V, and the discharge capacity was recorded.
[0062] (4) Needle penetration test: At 25±3℃, the battery is charged at a constant current of 1C to 4.2V, then switched to constant voltage (4.2V) charging until the charging current is less than 0.05C and then left for 0.5h. A 5mm diameter high temperature resistant steel needle (the cone angle of the needle tip is 45°-60°, and the surface of the needle is smooth, free of rust, oxide layer and oil) is used to penetrate the battery at a speed of 25±5mm / s from a direction perpendicular to the battery. The penetration position should be close to the geometric center of the punctured surface, and the steel needle stays in the battery. Observe for 1h.
[0063] (5) Heating test: At 25±3℃, the battery is charged at a constant current of 1C to 4.2V, then switched to constant voltage (4.2V) charging until the charging current is less than 0.05C and then left for 0.5h. The battery is then heated from 25±3℃ to 130℃ at a rate of 5℃ / min and kept at this temperature for 1h.
[0064] Table 1 Statistics of battery test results of Examples 1-6 and Comparative Examples 1-2
[0065]
[0066] The following conclusions can be drawn from Table 1:
[0067] 1. From the results of Examples 1-6, it can be seen that the in-situ polymerization process route of the present invention is highly compatible with the existing lithium-ion battery production line, and the required high-safety lithium-ion batteries can be prepared without the need to customize special equipment. The results of Examples 1-3 show that the in-situ polymerization process route of the present invention is applicable to a variety of positive and negative electrode systems, and the process route has a wide range of applications. The results of Examples 1, 4, 5, and 6 show that the present invention can be expanded to multiple in-situ polymerization systems and has a wide range of applicability.
[0068] 2. Comparison of the voltage changes of Examples 1-6 and Comparative Examples 1-2 at 25°C and 85°C shows that the battery voltage drops below 1V at 85°C, and the battery is in a short circuit state. Figure 1It can be seen that the main reason is that the electrolyte shrinks after the temperature rises to 80° C., cutting off the connection between the positive and negative electrode materials and the electrolyte. Further comparison of the needle puncture test and heating test results shows that the battery safety performance of Examples 1-6 is significantly improved.
[0069] 3. By comparing the rate performance and cycle performance of Examples 1-6 and Comparative Examples 1-2, it can be seen that the rate performance and cycle performance are not reduced, indicating that the temperature response characteristics introduced through the in-situ polymerization process route have no negative impact on the electrochemical performance of the battery.
[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims
1. A method for preparing a temperature-responsive high-safety lithium-ion battery, characterized in that: The following steps are included in sequence: (1) preparing a soft-packaged laminated dry battery cell including a positive electrode, a negative electrode and a separator, and then injecting a precursor solution 1, setting aside, performing a primary formation, and performing a primary exhaust; the precursor solution 1 includes an organic solvent, a lithium salt, a negative thermal expansion inorganic material, and a heat shrinkable organic material; (2) injecting the second precursor solution, placing it aside, causing polymerization reaction after heating, secondary formation, aging, secondary exhaust, and volume separation after packaging to obtain a temperature-responsive high-safety lithium-ion battery; The second precursor solution includes multifunctional polymer monomers, initiators, organic solvents and lithium salts.
2. The method for preparing a temperature-responsive high-safety lithium-ion battery according to claim 1, characterized in that: In step (1), in the precursor solution 1, the molar concentration of lithium salt is 0.9-1.1 M, and the negative thermal expansion inorganic material and the thermal shrinkage organic material account for 0.5-1.5 wt% and 1.5-3.5 wt% respectively.
3. The method for preparing a temperature-responsive high-safety lithium-ion battery according to claim 1, characterized in that: In step (1), the organic solvent is at least one of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, vinylene carbonate, fluoroethylene carbonate, methyl butyrate, ethyl butyrate and ethyl acetate; and the lithium salt is at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium bis(trifluoromethanesulfonyl imide) and lithium bis(fluorosulfonyl imide).
4. The method for preparing a temperature-responsive high-safety lithium-ion battery according to claim 1, characterized in that: In step (1), the negative thermal expansion inorganic material is a tungstate, including at least one of niobium tungstate, zirconium tungstate and yttrium tungstate; the heat shrinkable organic material is at least one of acrylamide, methacrylamide, diacetone acrylamide and N-methyl-2-acrylamide.
5. The method for preparing a temperature-responsive high-safety lithium-ion battery according to claim 1, characterized in that: In step (1), the mixture is placed at 20-30° C. for 24-48 hours.
6. The method for preparing a temperature-responsive high-safety lithium-ion battery according to claim 1, characterized in that: In step (2), in the precursor solution 2, the molar concentration of lithium salt is 0.9-1.1 M, and the proportions of multifunctional polymer monomer and initiator are 8-10 wt% and 0.5-1.5 wt% respectively.
7. The method for preparing a temperature-responsive high-safety lithium-ion battery according to claim 1, characterized in that: In step (2), the multifunctional polymer monomer is at least one of pentaerythritol tetraacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, ethoxylated trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate and trimethylolpropane triacrylate; and the initiator is an azo compound, including at least one of azobisisobutyronitrile, dimethyl azobisisobutyrate and azobisisoheptanonitrile.
8. The method for preparing a temperature-responsive high-safety lithium-ion battery according to claim 1, characterized in that: In step (2), the organic solvent is at least one of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, vinylene carbonate, fluoroethylene carbonate, methyl butyrate, ethyl butyrate and ethyl acetate; and the lithium salt is at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium bis(trifluoromethanesulfonyl imide) and lithium bis(fluorosulfonyl imide).
9. The method for preparing a temperature-responsive high-safety lithium-ion battery according to claim 1, characterized in that: In step (2), the mixture is placed at 15-25° C. for 24-48 hours and the polymerization reaction is carried out at 45-75° C. for 4-12 hours.
10. A temperature-responsive high-safety lithium-ion battery prepared by the method for preparing a temperature-responsive high-safety lithium-ion battery according to any one of claims 1 to 9.