Flexible package lithium ion battery for space and preparation method thereof

Abstract

The invention relates to the technical field of lithium ion batteries, and particularly discloses a space flexible package lithium ion battery and a preparation method thereof.The preparation method comprises the steps that S01, a positive pole piece, a polymer film and a negative pole piece are treated through a lamination technology, and then thermal compounding is conducted to prepare a battery cell; or treating the positive pole piece, the polymer film and the negative pole piece by adopting a lamination process, then winding by adopting a winding process, and then carrying out thermal compounding to obtain the battery cell; step S02, packaging and drying the battery cell by using a packaging film to obtain a soft package battery cell without liquid injection; s03, injecting a vacuum-resistant lithium ion battery electrolyte into the non-injected soft package battery core, and packaging to obtain a semi-finished soft package battery; and step S04, performing formation, vacuum pumping and packaging on the semi-finished soft package battery to obtain the space soft package lithium ion battery. The problems of interface failure, electrolyte volatilization, irradiation damage and the like of an existing battery in a vacuum environment are solved, the space environment adaptability of the battery is improved, and the service life of the battery is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a soft-package lithium ion battery for space use and a preparation method thereof. Background Art

[0002] Driven by advances in aerospace technology, the scale of commercial spaceflight has become possible. Commercial satellites are essential for the development of the modern aerospace industry, and satellite energy systems are the foundation for their normal operation. Lithium-ion batteries, thanks to their excellent performance, are widely used in the satellite sector.

[0003] When the satellite is in service, the power system operates at a high vacuum (1×10 -3 Pa) environment, and because satellites frequently enter and exit the Earth's shadow, the battery needs to have excellent cycle stability. In order for lithium-ion batteries to operate stably in a vacuum environment, the existing technology mostly uses pressure-resistant steel-cased lithium-ion batteries, and the structural parts that do not provide energy use high-density steel shells, which reduces the energy density of the lithium-ion battery pack. Soft-pack lithium-ion batteries are packaged in a lightweight aluminum-plastic film, which has almost no effect on the energy density. The energy density of soft-pack lithium-ion batteries can be as high as 300Wh / kg. However, traditional liquid soft-pack batteries contain flowable and volatile electrolytes. The volatile electrolyte can cause the battery to bulge, and even worse, it can cause the interface inside the battery cell to be misaligned. Space radiation can also penetrate the aluminum-plastic film of the soft-pack battery and cause the positive and negative electrode materials to fail rapidly. The above-mentioned shortcomings of traditional soft-pack batteries seriously limit their application in space environments. Summary of the Invention

[0004] In response to the above problems, the first purpose of the present invention is to provide a method for preparing soft-packaged lithium-ion batteries for space use. By optimizing the electrode-diaphragm composite process, vacuum-resistant electrolyte design, high vacuum packaging technology and radiation-resistant packaging film structure, the problems of interface failure, electrolyte volatilization, radiation damage and other problems of existing batteries in vacuum environments are solved, thereby improving the battery's adaptability to space environments and service life.

[0005] The second object of the present invention is to provide a soft-package lithium-ion battery for space use, in which the positive electrode sheet and the negative electrode sheet are tightly bonded to the polymer film, which significantly improves the interface stability of the electrode sheet, has a 1C charge and discharge cycle of ≥1000 times, and a capacity retention rate of ≥80%, thereby obtaining a soft-package lithium-ion battery that can be used stably in a high vacuum environment.

[0006] To achieve the first objective, the first technical solution of the present invention is: a method for preparing a soft-package lithium-ion battery for space use, comprising: step S01: processing a positive electrode sheet, a polymer film, and a negative electrode sheet using a lamination process, and then thermally compounding them to obtain a battery cell;

[0007] Alternatively, the positive electrode sheet, polymer film and negative electrode sheet are processed by a lamination process, then wound by a winding process, and then thermally composited to obtain a battery cell;

[0008] Step S02: using a packaging film to package the battery cell and perform drying treatment to obtain a soft-pack battery cell without liquid injection;

[0009] Step S03: injecting vacuum-resistant lithium-ion battery electrolyte into the uninjected soft-pack battery cell, encapsulating, and obtaining a semi-finished soft-pack battery;

[0010] The vacuum-resistant lithium-ion battery electrolyte is a liquid electrolyte or a solid electrolyte;

[0011] Step S04: forming, vacuum-evacuating, and packaging the semi-finished soft-package battery to obtain a soft-package lithium-ion battery for space use.

[0012] Its positive electrode sheet and negative electrode sheet are tightly bonded to the polymer film, which significantly improves the interface stability of the electrode sheet.

[0013] Preferably, the conditions for the thermal compounding in step S01 are: compounding temperature 50-160° C., pressure 0.3-5 MPa, and the thermal compounding makes the positive electrode sheet, the negative electrode sheet and the polymer film tightly bonded, significantly improving the interface stability of the electrode sheet;

[0014] The adhesive used in the thermal composite comprises one or more of polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, styrene-butadiene rubber, sodium carboxymethyl cellulose and polyimide.

[0015] Preferably, step S01 further includes welding the positive electrode tab and the negative electrode tab to the positive and negative electrode sheets and the negative electrode sheet in the battery cell respectively.

[0016] Preferably, in step S02, the packaging film is an aluminum-plastic packaging film with a thickness of 50-240 μm, which reduces the radiation absorption dose of the internal battery cells.

[0017] Preferably, in step S02, the packaging film is a packaging film comprising an anti-radiation functional layer, has a thickness of 50-300 μm, and an absorbed radiation dose of ≥30 krad, so as to prevent the internal battery cells from being irradiated;

[0018] The thickness of the anti-radiation functional layer is 1-100 μm, and the anti-radiation functional layer is one or more of epoxy resin-based, silicone-based, ceramic-based, and functionalized radiation-resistant coating.

[0019] Preferably, in step S03, when the vacuum-resistant lithium-ion battery electrolyte is the liquid electrolyte, the liquid electrolyte includes a vacuum-resistant solvent, a lithium salt, and a vacuum-resistant additive, which reduces the electrolyte saturated vapor pressure and the solvent volatilization rate;

[0020] The vacuum-resistant solvent is one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, γ-butyrolactone, methyl formate, ethyl formate, propyl formate, ethyl propionate, propyl propionate, butyl formate, butyl acetate, butyl propionate, butyl butyrate, and ethylene glycol dimethyl ether;

[0021] The lithium salt is at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium trifluorosulfonyl, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide and tris(trifluoromethylsulfonyl)methyllithium.

[0022] The vacuum-resistant additive accounts for 0.01% to 80% of the total mass of the vacuum-resistant lithium-ion battery electrolyte, and the vacuum-resistant additive includes at least one AB-type ionic liquid, which further reduces the saturated vapor pressure of the electrolyte and improves the packaging vacuum degree (≤3kPa);

[0023] The cation A in the AB type ionic liquid + is one of an alkyl imidazolium cation, a pyrrolidinium cation, an N-alkylpyridine, a tetraalkylammonium, and a tetraalkylphosphonium; the tetraalkyl group is one of a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a decyl group, a dodecyl group, a tetradecyl group, a hexadecyl group, and an octadecyl group;

[0024] The anion B in the AB type ionic liquid - It is one of bis(trifluoromethylsulfonyl)imide, bis(fluorosulfonyl)imide, tetrafluoroborate, and hexafluorophosphate.

[0025] Preferably, in step S03, when the vacuum-resistant lithium-ion battery electrolyte is the solid electrolyte, the solid electrolyte includes a vacuum-resistant solvent, a lithium salt and a vacuum-resistant additive; and also includes a polymerizable precursor and an initiator; after in situ polymerization, the components form a solid electrolyte to improve the vacuum degree of the battery cell packaging (≤2kPa).

[0026] The total mass of the vacuum-resistant solvent, the lithium salt and the vacuum-resistant additive accounts for 5% to 80% of the total mass of the vacuum-resistant lithium-ion battery electrolyte.

[0027] The polymerizable precursor is one or more of an acrylate monomer, an epoxy resin monomer, an ether monomer, a carbonate polymerizable monomer, and a silicon-based monomer;

[0028] The initiator is one or more of azo and peroxide.

[0029] Preferably, when the vacuum-resistant lithium-ion battery electrolyte is the solid electrolyte, step S03 further includes performing an in-situ polymerization reaction on the semi-finished soft-pack battery at 60-100°C for 2-8h, with a monomer polymerization conversion rate of ≥95%, to form a solid polymer electrolyte distributed in the pores of the positive and negative electrode sheets and the polymer membrane.

[0030] The battery electrolyte used is a vacuum-resistant electrolyte, which can effectively reduce the saturated vapor pressure of the electrolyte, slow down the volatilization of the electrolyte, increase the packaging pressure of the soft-pack battery, and the volume expansion rate in a vacuum environment (2kPa) is ≤2%, effectively suppressing bulging and improving the structure and cycle stability of the soft-pack battery.

[0031] Preferably, in step S04, the packaging conditions are packaging pressure <3 kPa and packaging temperature 100-200°C.

[0032] Low packaging pressure can reduce the internal and external pressure difference of soft-pack batteries in space environment and inhibit the volume expansion of soft-pack batteries.

[0033] To achieve the second purpose, the second technical solution of the present invention is: a soft-package lithium-ion battery for space use. The volume expansion rate in a vacuum environment (2kPa) is ≤2%, and the leakage rate in helium gas at 303kPa is not greater than 1×10 -7 Pa·m 3 / s. 1C charge and discharge cycles ≥ 1000 times, capacity retention rate ≥ 80%.

[0034] Beneficial effects of the above technical solution:

[0035] The present invention provides a soft-package lithium-ion battery for space use and a preparation method thereof. The soft-package lithium-ion battery is prepared by hot pressing and compounding. The positive electrode sheet, the negative electrode sheet and the polymer film are tightly bonded, which significantly improves the interface stability of the electrode sheet. The method solves the problems of interface failure, electrolyte volatilization, and radiation damage of existing batteries in a vacuum environment by optimizing the electrode-diaphragm composite process, vacuum-resistant electrolyte design, high-vacuum packaging technology and radiation-resistant packaging film structure, thereby improving the battery's adaptability to space environments and service life.

[0036] The electrolyte of the soft-pack lithium-ion battery provided by the present invention is a vacuum-resistant electrolyte that can effectively reduce the saturated vapor pressure of the electrolyte, increase the packaging pressure of the soft-pack battery, slow down the volatilization of the electrolyte, and achieve a volume expansion rate of ≤2% in a vacuum environment (2kPa), effectively suppressing bulging. It has radiation resistance stability, and the capacity of the battery cell decreases by less than 0.1% after irradiation with a 30krad dose of gamma rays. The soft-pack lithium-ion battery is kept at a pressure of no less than 303kPa for 2 hours. The soft-pack battery is tested by a mass spectrometer within 2 hours, and the leakage rate is no more than 1×10-7Pa·m 3 / s. The soft-pack lithium-ion battery can be used stably in a high vacuum environment with a 1C charge and discharge cycle of ≥1000 times and a capacity retention rate of ≥80%. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0038] Figure 1 This is a flow chart of the method for preparing a soft-packaged lithium-ion battery for space use provided by the present invention. DETAILED DESCRIPTION

[0039] The following further describes the implementation methods of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than an exhaustive list of all embodiments. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other unless there is a conflict.

[0040] The terms "first," "second," and the like (if any) in the specification and claims are used to distinguish similar objects and are not necessarily used to describe a particular order or sequential sequence. It should be understood that the terms used in this manner are interchangeable where appropriate so that the embodiments described herein can be implemented in an order other than that illustrated (if any) or described herein. In addition, the terms "including" and "having," and any variations thereof, are intended to cover non-exclusive inclusions, e.g., a process, method, system, product, or apparatus that includes a series of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, product, or apparatus.

[0041] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0042] The present invention provides a method for preparing a soft-package lithium-ion battery for space use, wherein the materials used include a positive electrode sheet, a negative electrode sheet, a polymer film, an electrolyte, an aluminum-plastic packaging film, a positive electrode tab, and a negative electrode tab. Figure 1 As shown, the following steps are included:

[0043] Step S01: using a laminate to place a polymer film between the positive electrode sheet and the negative electrode sheet, and then using a thermal composite process to perform hot pressing so that the positive electrode sheet, the negative electrode sheet and the polymer film interface are tightly bonded into a whole, and a winding process is used to form a battery cell;

[0044] Thermal composite process parameters: the binder is selected from at least one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride (PVDF-HFP), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC) or polyimide (PI);

[0045] The compounding temperature is 50-160℃ and the pressure is 0.3-5MPa.

[0046] Step S02: Weld the positive and negative tabs to the positive and negative electrode sheets, respectively. The cell is then packaged with packaging film, heat-sealed on three sides with a heat sealer, leaving one side open, and then vacuum-dried at 70°C for 24 hours to obtain a soft-pack cell without liquid injection.

[0047] The packaging film includes an aluminum-plastic packaging film or a packaging film including an anti-radiation functional layer, wherein the aluminum-plastic packaging film has a thickness of 50-240 μm, the packaging film including the anti-radiation functional layer has a thickness of 50-300 μm, and its radiation absorption dose is ≥30 krad. The anti-radiation layer is a combination of one or more of epoxy resin-based radiation resistance (such as epoxy polyacrylate), silicone-based (such as polysiloxane), ceramic-based (such as silicon carbide), and functionalized radiation-resistant coating (such as polyimide layer containing boron carbide), with a thickness of 1-100 μm.

[0048] Step S03: injecting vacuum-resistant lithium-ion battery electrolyte into the unfilled soft-pack battery cell, and packaging it using a vacuum sealing machine to obtain a semi-finished soft-pack battery;

[0049] The packaging process is: packaging pressure ≤ 3kPa, packaging temperature 100-200℃.

[0050] Vacuum-resistant electrolytes include liquid electrolyte solutions and solid electrolyte solutions:

[0051] The liquid electrolyte solution: the solvent is selected from low vapor pressure organic solvents such as ethylene carbonate, propylene carbonate, and diethyl carbonate; the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, trifluorosulfonyl lithium, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, and tris(trifluoromethylsulfonyl)methyl lithium.

[0052] The vacuum-resistant additive is at least one AB-type ionic liquid. The cation A+ is selected from an alkyl imidazolium cation, a pyrrolidinium cation, an N-alkylpyridine, a tetraalkylammonium, or a tetraalkylphosphonium. The tetraalkyl groups are selected from one or more of methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl. B is bis(trifluoromethylsulfonyl)imide, bis(fluorosulfonyl)imide, tetrafluoroborate, or hexafluorophosphate. The weight of the vacuum-resistant additive accounts for 0.01% to 80% of the total weight of the vacuum-resistant electrolyte.

[0053] Solid electrolyte solution: includes the same solvent, lithium salt and vacuum-resistant additive as the liquid electrolyte solution (the three substances account for 5%-80% of the total mass of the solid electrolyte), and also includes a polymerizable precursor comprising: monomers are one or more combinations of acrylate monomers (such as pentaerythritol tetraacrylate PETEA), epoxy resin monomers (such as bisphenol A epoxy resin), ether monomers (such as 1,3-dioxolane), carbonate polymerizable monomers (such as vinyl ethylene carbonate VEC), and silicon-based monomers (such as vinyltrimethoxysilane).

[0054] The initiator is a combination of one or more azo initiators (such as azobisisobutyronitrile (AIBN)) and peroxides (benzoyl peroxide (BPO). When a solid electrolyte solution is used, step S03 further includes subjecting the semi-finished soft-pack battery to in-situ polymerization at 60-100°C for 2-8 hours. The conversion rate is ≥95%, forming a continuous ion transport network.

[0055] The positive and negative electrode sheets and polymer films of the present invention all have gaps. The polymerizable precursors and initiators are in liquid form. After being injected into the soft-pack battery, the positive and negative electrode sheets and the polymer films are fully soaked by the precursors and initiators. After heating and polymerization under in-situ polymerization conditions, they are polymerized in the pores into a solid or gel state.

[0056] Step S04: The semi-finished battery is subjected to formation, secondary vacuum pumping, and secondary packaging to obtain a finished soft-pack lithium-ion battery for space use.

[0057] Performance test of the prepared soft-pack lithium-ion battery for space use

[0058] The soft-pack lithium-ion battery is placed in a 2kPa environment for testing to obtain the volume expansion rate; the pressure is maintained in helium at no less than 303kPa for 2 hours, and the soft-pack battery is tested with a mass spectrometer within 2 hours to obtain the leakage rate; 1C charge and discharge cycles are performed ≥1000 times to obtain the capacity retention rate.

[0059] Example 1

[0060] A soft-package lithium-ion battery for space use includes a polymer electrolyte membrane and positive and negative electrode plates, wherein the electrolyte membrane and the positive and negative electrode membrane binders are both PVDF-HFP. The preparation method is as follows:

[0061] The electrolyte membrane is placed between the positive and negative electrode sheets using a lamination process, stacked neatly, and placed in a hot press. The hot pressing temperature is controlled to be 110°C, the thermal composite time is 80s, and the pressure is 1.05MPa. The positive and negative electrode sheets and the electrolyte membrane are composited into a whole in the hot press.

[0062] The battery cell is welded to the tabs and placed in an aluminum-plastic packaging film. The three sides are heat-sealed with a heat sealer, with one side open, and then vacuum-dried at 70°C for 24 hours.

[0063] In a drying room, the prepared electrolyte is injected into the dried battery cells and then sealed using a vacuum sealer with a sealing pressure of 1 kPa, a sealing temperature of 180°C, and a sealing time of 3 seconds.

[0064] Electrolyte preparation: LiPF6 was dissolved in an EC / DEC mixed solvent to prepare a 1 mol / L LiPF6-EC / DEC (v / v = 1:1) electrolyte, and 10 wt% of an ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate) was added. The electrolyte preparation process was completed in an argon-filled glove box.

[0065] After the gel polymer battery was formed and tested in a 2kPa environment, the volume expansion rate was 0.9%. After 1000 cycles of 1C charge and discharge, the capacity retention rate was 87%. After being pressurized in 350kPa helium for 2 hours, the soft-pack battery was tested using a mass spectrometer, and the leakage rate was 9.3×10 -8 Pa·m 3 / s.

[0066] Example 2

[0067] Gel polymer batteries were prepared using the same process as in Example 1. The differences were that 1 mol / L LiPF6-EC / DEC (v / v = 1:1), ethyl phthalate monomer, and azobisisobutyronitrile were added to the electrolyte solution. The volume ratio of LiPF6-EC / DEC to ethyl phthalate was 1:1, and the amount of azobisisobutyronitrile was 0.5%. The packaging pressure was 1 kPa, and after packaging, the cells were heated in an oven at 60°C for 12 hours to polymerize. All other conditions remained the same as in Example 1.

[0068] After the gel polymer battery was formed and tested in a 2kPa environment, the volume expansion rate was 0.4%, and the capacity retention rate was 85% after 1000 cycles of 1C charge and discharge. The gel polymer battery was kept at 350kPa helium pressure for 2 hours, and the soft pack battery was tested using a mass spectrometer, with a leakage rate of 8×10 -8Pa·m 3 / s.

[0069] Example 3

[0070] This embodiment provides a polymer battery, including a polymer separator, positive and negative electrode plates, wherein the positive electrode plate binder is PVDF, the negative electrode plate binder is LA133 binder (PAA type binder), and both sides of the polymer separator additionally include a PVDF coating with a thickness of 2μm. The preparation method is as follows:

[0071] The polymer separator is placed between the positive and negative electrode sheets using a lamination process, thermally composited and then wound to form the battery cell. The hot pressing temperature for the thermal composite is controlled at 60°C to 100°C, the thermal composite time is 20s to 80s, and the pressure is 1.05MPa.

[0072] The obtained battery cell was welded with the pole ears and placed in an aluminum-plastic packaging film. The three sides were heat-sealed with a heat sealer, one side was left open, and vacuum dried at 70°C for 24 hours.

[0073] In a drying room, the prepared electrolyte is injected into the dried cells. After removal, they are sealed using a vacuum sealer at a pressure of 1 kPa, a temperature of 180°C, and a sealing time of 3 seconds.

[0074] LiPF6 was dissolved in a mixed solvent of EC / DEC to prepare a 1 mol / L LiPF6-EC / DEC (v / v=1:1) electrolyte, and 10 wt% of an ionic liquid was added. The ionic liquid was 1-ethyl-3-methylimidazolium tetrafluoroborate. The electrolyte preparation process was completed in an argon-filled glove box.

[0075] After the polymer battery was formed, it was tested in a 2kPa environment. The volume expansion rate was 1%. After 1000 cycles of 1C charge and discharge, the capacity retention rate was 83.7%. After being pressurized in 350kPa helium for 2 hours, the soft-pack battery was tested using a mass spectrometer. The leakage rate was 9.8×10 -8 Pa·m 3 / s.

[0076] Example 4

[0077] The polymer battery was prepared by referring to the preparation process of Example 3. The difference was that the aluminum-plastic film used had a polyimide layer doped with boron carbide on its surface, with a thickness of 10 μm. The other steps were the same as in Example 1.

[0078] The obtained polymer battery was irradiated in a gamma ray irradiation device with a total dose of 30 krad. The discharge capacity of the irradiated battery was tested, and the capacity retention rate after irradiation was 99.98%.

[0079] Comparative Example 1

[0080] The gel polymer battery was prepared according to the preparation process of Example 1, except that the liquid electrolyte was 1 mol / L LiPF6-EC / DEC (v / v=1:1) electrolyte, no ionic liquid was added, and the other steps were consistent with Example 1. Comparative Example 1 had a volume expansion rate of 5.3% in a 2 kPa environment, a capacity retention rate of 80% after 1000 cycles, and a mass spectrometer was used to detect the soft-pack battery after maintaining the pressure at 350 kPa for 2 h. The leakage rate was 1.0×10 -7 Pa·m 3 Because no ionic liquid was added to the comparative example, the saturated vapor pressure of the electrolyte was relatively high, and the volume expansion caused by solvent evaporation reduced the cycle stability to a certain extent and also caused a slight increase in the leakage rate.

[0081] Comparative Example 2

[0082] The gel polymer battery was prepared by referring to the preparation process of Example 2. The difference was that the added electrolyte was 1 mol / L LiPF6-EC / DEC (v / v=1:1), and the heating polymerization process was omitted. The other steps were consistent with Example 2.

[0083] Comparative Example 2 shows a volume expansion rate of 23% in a 2kPa environment, and a capacity retention rate of 35% after 1000 cycles of 1C charge and discharge. The gel polymer battery was kept at 350kPa helium pressure for 2 hours, and the soft pack battery was tested using a mass spectrometer. The leakage rate was 1.2×10 -7 Pa·m 3 / s. Since the precursor did not form a solid electrolyte due to the lack of heating and polymerization, the solvent volatilization caused a huge volume expansion, resulting in a sharp decrease in cycle stability and an increase in leakage rate to 1.2×10 -7 Pa·m 3 / s.

[0084] Comparative Example 3

[0085] The soft-pack lithium-ion battery was prepared by referring to the preparation process of Example 3. The difference is that the battery cell is not processed by the thermal composite process, and the positive and negative electrode sheets and polymer separator are directly assembled by the winding process. Comparative Example 3, the battery was tested in a 2kPa vacuum environment, the volume expansion rate was 1.2%, the 1C charge and discharge cycle was 1000 cycles, the capacity retention rate was 75%, and the soft-pack battery was pressurized in 350kPa helium for 2h and tested by mass spectrometer, the leakage rate was 9.8×10 -8 Pa·m 3 Because the positive and negative electrodes and the polymer separator are not thermally bonded into a whole, the 2kPa vacuum environment reduces the electrode interface stability during the soft-pack battery cycle, thereby reducing the cycle stability of the soft-pack battery.

[0086] Comparative Example 4

[0087] The polymer battery was prepared using the same process as in Example 4. The difference was that the aluminum-plastic film used did not contain a polyimide layer containing boron carbide and had a thickness of 150 μm. All other steps remained the same as in Example 4. In Comparative Example 4, the resulting polymer battery was irradiated in a gamma-ray irradiation apparatus for a total of 30 krad. The irradiated battery was tested for discharge capacity, and the post-irradiation capacity retention was 96%. Because the aluminum-plastic film in Comparative Example 4 did not contain an anti-radiation coating, some of the radiation was absorbed by the battery cell, causing damage to the positive and negative electrodes, resulting in reduced capacity.

[0088] It can be seen that the soft-package lithium-ion battery for space use and the preparation method thereof provided by the present invention adopt a hot pressing composite method to prepare the soft-package lithium-ion battery. The positive electrode sheet, the negative electrode sheet and the polymer film are tightly bonded, which significantly improves the interface stability of the sheet. This method solves the problems of interface failure, electrolyte volatilization, and radiation damage of existing batteries in a vacuum environment by optimizing the electrode-diaphragm composite process, vacuum-resistant electrolyte design, high vacuum packaging technology and radiation-resistant packaging film structure, thereby improving the battery's adaptability to the space environment and service life.

[0089] The electrolyte of the soft-pack lithium-ion battery provided by the present invention is a vacuum-resistant electrolyte that can effectively reduce the saturated vapor pressure of the electrolyte, increase the packaging pressure of the soft-pack battery, slow down the volatilization of the electrolyte, and achieve a volume expansion rate of ≤2% in a vacuum environment (2kPa), effectively suppressing bulging. It has radiation resistance stability, and the capacity of the battery cell decreases by less than 0.1% after irradiation with a 30krad dose of gamma rays. The soft-pack lithium-ion battery is kept at a pressure of no less than 303kPa for 2 hours. The soft-pack battery is tested by a mass spectrometer within 2 hours, and the leakage rate is no more than 1×10-7Pa·m 3 / s. The soft-pack lithium-ion battery can be used stably in a high vacuum environment with a 1C charge and discharge cycle of ≥1000 times and a capacity retention rate of ≥80%.

[0090] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing a soft-package lithium-ion battery for space use, characterized in that: include: Step S01: processing the positive electrode sheet, the polymer film and the negative electrode sheet using a lamination process, and then thermally compounding them to obtain a battery cell; Alternatively, the positive electrode sheet, polymer film and negative electrode sheet are processed by a lamination process, then wound by a winding process, and then thermally composited to obtain a battery cell; Step S02: using a packaging film to package the battery cell and perform drying treatment to obtain a soft-pack battery cell without liquid injection; Step S03: injecting vacuum-resistant lithium-ion battery electrolyte into the uninjected soft-pack battery cell, encapsulating, and obtaining a semi-finished soft-pack battery; The vacuum-resistant lithium-ion battery electrolyte is a liquid electrolyte or a solid electrolyte; Step S04: forming, vacuum-evacuating, and packaging the semi-finished soft-package battery to obtain a soft-package lithium-ion battery for space use.

2. The method for preparing a soft-package lithium-ion battery for space use according to claim 1, wherein: The conditions for the thermal compounding in step S01 are: compounding temperature 50-160° C., pressure 0.3-5 MPa; The adhesive used in the thermal composite comprises one or more of polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, styrene-butadiene rubber, sodium carboxymethyl cellulose and polyimide.

3. The method for preparing a soft-package lithium-ion battery for space use according to claim 1, wherein: Step S01 also includes welding the positive electrode tab and the negative electrode tab to the positive and negative electrode sheets and the negative electrode sheet in the battery cell respectively.

4. The method for preparing a soft-package lithium-ion battery for space use according to claim 1, wherein: In step S02, the packaging film is an aluminum-plastic packaging film with a thickness of 50-240 μm.

5. The method for preparing a soft-package lithium-ion battery for space use according to claim 1, wherein: In step S02, the packaging film is a packaging film including an anti-radiation functional layer, has a thickness of 50-300 μm, and a radiation absorbed dose of ≥30 krad; The thickness of the anti-radiation functional layer is 1-100 μm, and the anti-radiation functional layer is one or more of epoxy resin-based, silicone-based, ceramic-based, and functionalized radiation-resistant coating.

6. The method for preparing a soft-package lithium-ion battery for space use according to claim 1, wherein: In step S03, when the vacuum-resistant lithium-ion battery electrolyte is the liquid electrolyte, the liquid electrolyte includes a vacuum-resistant solvent, a lithium salt, and a vacuum-resistant solvent; The vacuum-resistant solvent is one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, γ-butyrolactone, methyl formate, ethyl formate, propyl formate, ethyl propionate, propyl propionate, butyl formate, butyl acetate, butyl propionate, butyl butyrate, and ethylene glycol dimethyl ether; The lithium salt is at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium trifluorosulfonyl, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide and lithium tris(trifluoromethylsulfonyl)methyl; The vacuum-resistant additive accounts for 0.01% to 80% of the total mass of the vacuum-resistant lithium-ion battery electrolyte, and the vacuum-resistant additive includes at least one AB-type ionic liquid; The cation A in the AB type ionic liquid + is one of an alkyl imidazolium cation, a pyrrolidinium cation, an N-alkylpyridine, a tetraalkylammonium, and a tetraalkylphosphonium; the tetraalkyl group is one of a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a decyl group, a dodecyl group, a tetradecyl group, a hexadecyl group, and an octadecyl group; The anion B in the AB type ionic liquid - It is one of bis(trifluoromethylsulfonyl)imide, bis(fluorosulfonyl)imide, tetrafluoroborate, and hexafluorophosphate.

7. The method for preparing a soft-package lithium-ion battery for space use according to claim 6, wherein: In step S03, when the vacuum-resistant lithium-ion battery electrolyte is the solid electrolyte, the solid electrolyte includes a vacuum-resistant solvent, a lithium salt, and a vacuum-resistant additive; and further includes a polymerizable precursor and an initiator; The total mass of the vacuum-resistant solvent, the lithium salt and the vacuum-resistant additive accounts for 5% to 80% of the total mass of the vacuum-resistant lithium-ion battery electrolyte. The polymerizable precursor is one or more of an acrylate monomer, an epoxy resin monomer, an ether monomer, a carbonate polymerizable monomer, and a silicon-based monomer; The initiator is one or more of azo and peroxide.

8. The method for preparing a soft-package lithium-ion battery for space use according to claim 7, wherein: When the vacuum-resistant lithium-ion battery electrolyte is the solid electrolyte, step S03 further includes performing an in-situ polymerization reaction on the semi-finished soft-pack battery at 60-100° C. for 2-8 hours.

9. The method for preparing a soft-package lithium-ion battery for space use according to claim 1, wherein: In step S04, the packaging conditions are packaging pressure <3 kPa and packaging temperature 100-200°C.

10. A soft-package lithium-ion battery for space use, characterized in that: The method according to any one of claims 1 to 9 is used for preparation.

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