A semi-solid pouch battery and a preparation method thereof

Abstract

This invention discloses a semi-solid-state pouch battery and its preparation method. Addressing the shortcomings of existing one-step in-situ polymerization lithium-ion pouch batteries, such as excessive gas production, simultaneous solidification of bubbles, low initial efficiency, and poor cycle life, this invention proposes a process route for semi-solid-state lithium-ion pouch batteries using in-situ polymerization, incorporating a secondary electrolyte injection step. This ensures that the electrolyte is fully formed and reacted before in-situ polymerization, effectively eliminating gas production and degassing, and achieving bubble-free solidification, thereby improving initial efficiency and cell cycle performance. This makes the technology transfer from academic research to practical products possible, enabling the production of semi-solid-state lithium-ion batteries that meet real-world requirements.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery technology, and in particular relates to a semi-solid soft-pack battery and its preparation method. Background Technology

[0002] Electrolytes are a crucial component of lithium-ion batteries. Currently used electrolytes are all organic compounds, which can lead to problems such as leakage and combustion under extreme conditions. To address lithium battery safety issues, all-solid-state electrolytes have been extensively researched. While all-solid-state electrolytes can improve battery safety, all-solid-state lithium-ion batteries have higher interfacial impedance, resulting in poor rate capability and cycle performance. Current technology is not mature enough to meet current usage requirements.

[0003] Gel electrolytes, commonly used in semi-solid-state batteries, combine the excellent ionic conductivity of liquid electrolytes with the safety performance of all-solid-state electrolytes. Furthermore, they can be produced on existing lithium-ion battery manufacturing equipment, reducing equipment and factory investment. Therefore, gel electrolytes are widely studied by major research institutions and large lithium-ion battery companies. Many gel electrolytes are prepared using in-situ polymerization methods, often referred to as in-situ solidification technology. This typically involves injecting liquid monomers into the battery cell via a liquid injection method. After impregnation, the monomers are polymerized under certain conditions to form an in-situ solidified battery. For example, Chinese invention patent application CN105914405A proposes injecting liquid epoxy compounds and lithium salts into the battery, initiating in-situ ring-opening solidification under heating conditions to form an integrated all-solid-state polymer battery. Chinese invention patent application CN108493486A uses acrylate and an initiator dissolved in an electrolyte, injected into the battery, and initiating unsaturated double bond polymerization under heating conditions to form an integrated gel polymer battery. Chinese invention patent application CN111533851A uses a mixture of small-molecule carbonate olefins containing double bonds, ethylene glycol acrylate, and an initiator injected into the solid-state battery interface for thermally initiated polymerization to form an integrated electrode-electrolyte all-solid-state battery. Chinese invention patent application CN111540956A dissolves isocyanate and polypropylene glycol in the electrolyte and injects them into the battery for electropolymerization to form an integrated battery, reducing the electrode-electrolyte interface impedance.

[0004] Meanwhile, there are other methods for preparing batteries using in-situ polymerization. For example, Chinese invention patent application CN110048158A utilizes a casting method to form a bilayer electrolyte membrane with one side being ester and the other ether through in-situ polymerization on both sides of a porous membrane. This membrane simultaneously meets the stability requirements of both high-voltage positive and low-voltage negative electrodes. Chinese invention patent application CN110581314A coats the positive electrode contact side of the support separator with an inorganic solid electrolyte and the negative electrode contact side with a polymer electrolyte, reducing electrolyte oxidation and improving battery safety and cycle stability. However, currently reported multilayer composite membrane processes are complex, often involving coating the membrane outside the cell and then combining it with the electrode sheet. This results in poor electrolyte-electrode interface contact, high impedance, and is detrimental to battery capacity. Chinese invention patent application CN114335716A mixes reactive monomers into the positive and negative electrodes and adds crosslinking agents and other reaction aids to the electrolyte for in-situ polymerization.

[0005] Considering factors such as compatibility with existing lithium batteries, cost, and ease of equipment modification for lithium battery industrialization, regardless of changes in the in-situ polymerization method, processes such as electrolyte injection and in-situ polymerization remain indispensable. Furthermore, direct electrolyte injection followed by in-situ polymerization is the simplest and most convenient battery manufacturing process. However, researchers have focused primarily on the material structure and polymerization reaction in their studies of in-situ polymerization, with limited research into the practical processes for semi-solid-state battery industrialization, such as electrolyte injection. Solutions to process problems encountered during industrialization, such as severe gas generation, uneven polymerization, and low initial efficiency, are also rarely proposed. Summary of the Invention

[0006] To address the above issues, we propose an industrially viable manufacturing process for interface-free semi-solid pouch cells with a three-dimensional network electrolyte.

[0007] A method for preparing a semi-solid-state pouch cell, the semi-solid-state pouch cell comprising a dry cell, the method comprising the following steps:

[0008] (1) In the dry cell, the first electrolyte injection is carried out, and electrolyte precursor one is injected. The electrolyte precursor one includes a reactive monomer, a crosslinking agent, a small molecule plasticizer and a lithium salt.

[0009] (2) First transformation, then first venting;

[0010] (3) Second injection: Inject electrolyte precursor II, which includes an initiator and a small molecule plasticizer, and may or may not include lithium salt. The reactants and crosslinking agents undergo in-situ polymerization under the action of the initiator.

[0011] (4) The second transformation occurs, followed by the second venting.

[0012] The reactive monomer is an organic reactive monomer containing double bonds or cyclic functional groups, capable of free radical polymerization to generate a long-chain polymer with freely movable chain segments;

[0013] The initiator is an azo initiator, a peroxide initiator, or anionic and cationic initiators that initiate the free radical polymerization of the reactant monomers.

[0014] The crosslinking agent is an organic compound containing bifunctional or polyfunctional groups that can combine with free radical reactive monomers.

[0015] The reactant monomer is at least one of the following: vinyl acetate, dimethyl allyl dicarboxylate, diethyl allyl malonate, methyl allyl carbonate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, methyl methacrylate, butyl methacrylate, vinylene carbonate, ethylene ethylene carbonate, methyl vinyl sulfone, ethyl vinyl sulfone, ethoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, acrylamide, N,N-methylenebisacrylamide, etc. Butyrolactam, Acrylonitrile, 2-Acrylonitrile ethyl acrylate, 2-Acrylonitrile-2-butyl acrylate, 2-Acrylonitrile-3,3-Diphenylacrylate isooctyl acrylate, 1-Cyclohexeneacetonitrile, Hexafluorobutyl methacrylate, Trifluoroethyl methacrylate, Polyethylene glycol methacrylate, Polyethylene glycol dimethacrylate, Polyethylene glycol diacrylate, Ethoxyethyl acrylate, Polyethylene glycol, 1,3-Dioxolane, Dioxane, Vinylmethoxysilane, 2-(Trimethylsiloxy)methacrylate, Trivinylcyclotrisiloxane, Tri(2-methoxyethoxy)vinylsilane.

[0016] The crosslinking agent is at least one of the following: polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, and polyether polyacrylate.

[0017] The initiator is at least one of the following: azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, tert-butyl peroxide, methyl ethyl ketone peroxide, aluminum trifluoromethanesulfonate, magnesium trifluoromethanesulfonate, lithium difluorosulfonylimide, and tin trifluoromethanesulfonate.

[0018] The lithium salt is at least one of the following: LiBF4, LiBF6, LiAsF6, LiPF6, LiClO4, LiFSI, LiTFSI, LiB(C6H5)4, LiAlCl4, LiBr, LiCF3SO3, LiN(CF3SO2)2, LiC(CF3SOSO2)3.

[0019] The small molecule plasticizer is at least one of the following: ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, fluorinated ethylene carbonate, dipropyl carbonate, dimethyl sulfoxide dimethoxyethane, N-methyl-2-pyrrolidone, γ-butyrolactone, and polyethylene glycol dimethyl ether.

[0020] Preferably, the mass fraction of the reactive monomer in the electrolyte precursor is 10% to 18%;

[0021] The mass fraction of the crosslinking agent in electrolyte precursor one is 1% to 2.2%;

[0022] The initiator has a mass fraction of 0.50% to 0.95% in the electrolyte precursor II;

[0023] The mass fraction of lithium salt in electrolyte precursor one is 10% to 15%;

[0024] The mass fraction of lithium salt in electrolyte precursor II is 0%–15%;

[0025] The other components in precursor one and precursor two are small molecule plasticizers.

[0026] Preferably, electrolyte precursor one and electrolyte precursor two are added at a mass ratio of 1.8 to 1.9:1.

[0027] Preferably, in step (3), the temperature during in-situ polymerization is 60-90℃, the polymerization time is 0.1-72h, and the polymerization pressure is controlled between 0.2Mpa and 500Mpa.

[0028] The conditions for the first formation are: charging current of 0.01C to 0.33C, and charging time of 60 to 120 minutes;

[0029] The conditions for the second formation are: charging current of 0.01C to 0.5C, and charging cut-off voltage of rated voltage.

[0030] Preferably, the venting time for the first and second venting is 1 to 20 seconds, and the venting vacuum is between -98 kPa and -20 kPa.

[0031] After the first exhaust, high-temperature aging is carried out at a temperature of 45℃~80℃ for 12~120h.

[0032] After the second venting, allow the mixture to stand for 1 to 30 minutes.

[0033] Preferably, the ambient dew point during the first and second electrolyte injections is controlled at -60℃ to -35℃, and the vacuum degree is -98kPa to -20kPa. After the first electrolyte injection, the cell should be left to stand at room temperature for at least 48 hours to allow the electrolyte precursor to fully wet the cell.

[0034] The above formulations and process parameters are optimized conditions confirmed through multiple experiments, allowing the reactive monomers to polymerize and meet the electrical performance requirements of the battery cell. If the experiments are not conducted according to the optimized conditions, either the reactive monomers will fail to polymerize or overpolymerize, or the electrical performance of the battery cell will be severely degraded.

[0035] The present invention also provides a semi-solid-state pouch cell prepared by the aforementioned preparation method.

[0036] The beneficial effects of this invention are as follows: Addressing the shortcomings of existing in-situ polymerized lithium-ion pouch batteries using a one-step electrolyte injection polymerization method, such as excessive gas production, simultaneous solidification of bubbles, low initial efficiency, and poor cycle life, this invention proposes a process route for semi-solid-state lithium-ion pouch batteries employing in-situ polymerization, adding a secondary electrolyte injection step. This ensures that the electrolyte is fully formed, reacted, and vented before in-situ polymerization, achieving bubble-free solidification, thus improving initial efficiency and cell cycle performance. This makes the technology transfer from academic research to actual products possible, enabling the production of semi-solid-state lithium-ion batteries that meet real-world requirements. Detailed Implementation

[0037] Example 1

[0038] A specific scheme for preparing an interface-free semi-solid-state pouch cell is as follows:

[0039] 1. Ternary positive electrode sheets are prepared by processes such as homogenization, coating, rolling, slitting, and die cutting; graphite negative electrode sheets are prepared by processes such as homogenization, coating, rolling, slitting, and die cutting; and alumina-coated separators are used to stack the positive and negative electrodes.

[0040] 2. Prepare the first precursor of in-situ polymerization electrolyte: Mix 9g of the reactant vinylene carbonate VC, 2g of the crosslinking agent polyethylene glycol diacrylate PEGDA, 20g of the small molecule plasticizer ethylene carbonate, 25g of methyl ethyl carbonate, 25g of diethyl carbonate, and 9g of lithium salt LiPF6 into an electrolyte bottle and stir thoroughly for 4 hours to obtain the first precursor of in-situ polymerization electrolyte.

[0041] 3. Prepare the second precursor of in-situ polymerization electrolyte: Mix 0.25g of initiator azobisisobutyronitrile (AIBN), 15g of small molecule plasticizers ethylene carbonate, 15g of methyl ethyl carbonate, 15g of diethyl carbonate, and 5g of lithium salt LiFSI into an electrolyte bottle and stir thoroughly for 6 hours to obtain the second precursor of in-situ polymerization electrolyte.

[0042] 4. Stack and assemble the positive and negative electrode sheets and separator prepared in step 1, and dry them to prepare a dry battery cell without liquid injection.

[0043] 5. The in-situ polymerized electrolyte precursor prepared in step 2 is injected into the dry cell prepared in step 4 for the first liquid injection. The dew point of the liquid injection environment is controlled at -60℃ and the vacuum degree is -98kPa. After liquid injection, the cell is left to stand at room temperature for 48 hours to soak.

[0044] 6. The electrolyte-filled cells prepared in step 5 are subjected to formation, degassing, and high-temperature aging processes. The formation conditions are: charging current 0.01C, charging time 60 minutes; degassing time 20s, degassing vacuum degree -98kPa; aging temperature 45℃, aging time 120h.

[0045] 7. The in-situ polymerized electrolyte precursor prepared in step 3 is injected into the battery cell prepared in step 6 for a second electrolyte injection. The dew point of the electrolyte injection environment is controlled at -60℃ and the vacuum degree is -98kPa.

[0046] 8. Place the electrolyte-filled battery cell prepared in step 7 in a high-temperature environment of 60°C for in-situ polymerization at a polymerization pressure of 0.2 MPa for 72 hours to solidify the electrolyte.

[0047] 9. Perform secondary formation, secondary venting, settling, and capacity testing on the cells prepared in step 8 to complete the preparation of the semi-solid-state battery. The charging current for secondary formation is 0.5C, and the charging cutoff voltage is 4.2V. The secondary venting time is 20s, and the venting vacuum degree is -98kPa. The settling time is 30min.

[0048] 10. The prepared semi-solid battery was subjected to capacity, cycle, electrical performance tests and safety performance tests such as nail penetration and overcharge. The cell was disassembled to observe the amount of bubbles in the solidified electrolyte. It was found that no bubbles were observed in the solidified electrolyte.

[0049] Example 2

[0050] The overall method is the same as in Example 1, except that in step 2, the reactant is 18g of polyethylene glycol methacrylate (PEGMA), the crosslinking agent is 2g of polyethylene glycol dimethacrylate (PEGDMA), the lithium salt is 15g of LiCF3O3, and the small molecule plasticizers are 25g of dimethyl carbonate, 20g each of N-methyl-2-pyrrolidone and propylene carbonate. In step 3, the initiator is 0.5g of benzoyl peroxide, the lithium salt is 7.9g of LiTFSI, and the small molecule plasticizers are 16g of dimethyl carbonate, 14.1g each of N-methyl-2-pyrrolidone and propylene carbonate.

[0051] The prepared semi-solid battery was subjected to capacity, cycle, electrical performance tests, and safety performance tests such as nail penetration and overcharge. The cell was disassembled to observe the amount of air bubbles in the solidified electrolyte. No air bubbles were observed in the solidified electrolyte.

[0052] Example 3

[0053] The overall method is the same as in Example 1, except that in step 2, the reactant monomer is 11g of 1,3-dioxolane, the crosslinking agent is 1g of pentaerythritol tetraacrylate, the lithium salt is 15g of LiClO4, and the small molecule plasticizers are 23g of fluorinated ethylene carbonate, 25g of dipropyl carbonate, and 25g of polyethylene glycol dimethyl ether. In step 3, the initiator is 0.5g of aluminum trifluoromethanesulfonate, without lithium salt, and the small molecule plasticizers are 16g of fluorinated ethylene carbonate, 23g of dipropyl carbonate, and 14.1g of polyethylene glycol dimethyl ether.

[0054] The prepared semi-solid battery was subjected to capacity, cycle, electrical performance tests, and safety performance tests such as nail penetration and overcharge. The cell was disassembled to observe the amount of air bubbles in the solidified electrolyte. No air bubbles were observed in the solidified electrolyte.

[0055] Example 4

[0056] The overall method is the same as in Example 1, except that in step 2 the reactants are vinylmethoxysilane and acrylonitrile; the precursor lithium salt is LiBF6, the precursor dilithium salt is LiTFSI; the crosslinking agent is polyether polyacrylate; and the small molecule plasticizers are ethylene carbonate, dimethyl sulfoxide dimethoxyethane, and γ-butyrolactone. The addition mass of each component is the same as in Example 1.

[0057] The prepared semi-solid battery was subjected to capacity, cycle, electrical performance tests, and safety performance tests such as nail penetration and overcharge. The cell was disassembled to observe the amount of air bubbles in the solidified electrolyte. No air bubbles were observed in the solidified electrolyte.

[0058] Example 5

[0059] The overall method is the same as in Example 1, except that in step 2 the reactants are methyl vinyl sulfone and methyl methacrylate; the precursor lithium salt is LiPF6, the precursor dilithium salt is LiFSI; the crosslinking agent is ethoxylated trimethylolpropane triacrylate; and the small molecule plasticizers are ethylene carbonate, dimethyl carbonate, and fluorinated ethylene carbonate. The addition mass of each component is the same as in Example 1.

[0060] The prepared semi-solid battery was subjected to capacity, cycle, electrical performance tests, and safety performance tests such as nail penetration and overcharge. The cell was disassembled to observe the amount of air bubbles in the solidified electrolyte. No air bubbles were observed in the solidified electrolyte.

[0061] Example 6

[0062] The overall method is the same as in Example 1, except that the dew point of the injection environment in steps 5-9 is -35°C, the injection vacuum is -20kPa, the venting time is 1s, and the venting vacuum is -20kPa.

[0063] The prepared semi-solid battery was subjected to capacity, cycle, electrical performance tests, and safety performance tests such as nail penetration and overcharge. The cell was disassembled to observe the amount of air bubbles in the solidified electrolyte. No air bubbles were observed in the solidified electrolyte.

[0064] Example 7

[0065] The overall method is the same as in Example 1, except that the conditions for the first formation in steps 5 to 9 are: charging current 0.33C and charging time 120 minutes; and the conditions for the second formation are: charging current 0.01C and charging cut-off voltage 4.2V.

[0066] The prepared semi-solid battery was subjected to capacity, cycle, electrical performance tests, and safety performance tests such as nail penetration and overcharge. The cell was disassembled to observe the amount of air bubbles in the solidified electrolyte. No air bubbles were observed in the solidified electrolyte.

[0067] Example 8

[0068] The overall method is the same as in Example 2, except that the high-temperature aging temperature in steps 5-9 is 80°C and the time is 12h; the temperature during in-situ polymerization is 90°C, the polymerization time is 0.1h, and the polymerization pressure is controlled at 500MPa.

[0069] The prepared semi-solid battery was subjected to capacity, cycle, electrical performance tests, and safety performance tests such as nail penetration and overcharge. The cell was disassembled to observe the amount of air bubbles in the solidified electrolyte. No air bubbles were observed in the solidified electrolyte.

[0070] Comparative Example 1

[0071] A conventional interfaceless semi-solid-state pouch cell was prepared using a single liquid injection method. The specific scheme is as follows:

[0072] Steps 1-4 are the same as in Example 1, except that the injection in steps 5-9 is changed to a single injection, and the specific method is as follows:

[0073] 5. Mix the in-situ polymerization electrolyte precursor 1 prepared in step 2 with the in-situ polymerization precursor 2 prepared in step 3 and stir at room temperature for 2 hours until homogeneous. Inject the mixture into the dry cell prepared in step 4. The dew point of the injection environment is controlled at -60℃ and the vacuum degree is -98kPa. After injection, allow the mixture to stand at room temperature for 48 hours to soak.

[0074] 6. Place the electrolyte-filled battery cell prepared in step 5 in a high-temperature environment of 60°C for in-situ polymerization at a polymerization pressure of 0.2 MPa for 72 hours to solidify the electrolyte.

[0075] 7. The electrolyte-filled cells prepared in step 6 are subjected to formation, degassing, and high-temperature aging processes. The formation conditions are: charging current 0.01C, charging time 60 minutes, secondary formation charging current 0.5C, and charging cut-off voltage 4.2V; degassing time 20s, degassing vacuum degree -98kPa; aging temperature 45℃, and aging time 120h.

[0076] The prepared semi-solid battery was subjected to capacity, cycle, electrical performance tests, and safety performance tests such as nail penetration and overcharge. The cell was disassembled to observe the amount of bubbles in the solidified electrolyte, and bubbles were found to be present in the solidified electrolyte.

[0077] Comparative Example 2

[0078] The specific scheme for preparing liquid pouch batteries is as follows:

[0079] 1. The lithium-ion battery manufacturing process is used to prepare ternary positive electrode sheets, and the lithium-ion battery manufacturing process is used to prepare graphite negative electrode sheets. An alumina-coated separator is used to stack the positive and negative electrodes.

[0080] 2. Stack and assemble the positive and negative electrode sheets and separator prepared in step 1, and dry them to prepare a dry battery cell without liquid injection.

[0081] 3. Prepare an electrolyte solution (EC∶EMC∶DEC=1∶1∶1, LiPF6 is 1mol / L) and inject it into the dry cell prepared in step 2. The dew point of the electrolyte injection environment is controlled at -60℃ and the vacuum degree is -98kPa. After the electrolyte injection, let it stand at room temperature for 48h to soak.

[0082] 4. The electrolyte-filled cells prepared in step 3 are subjected to formation, degassing, and high-temperature aging processes. The formation conditions are: charging current 0.01C, charging time 60 minutes, secondary formation charging current 0.5C, and charging cut-off voltage 4.2V; degassing time 20s, degassing vacuum degree -98kPa; aging temperature 45℃, and aging time 120h.

[0083] 5. The prepared liquid lithium battery was subjected to electrical performance tests such as capacity, internal resistance, cycle life, rate capability, and high-temperature storage, as well as safety performance tests such as nail penetration and overcharge. The cell was disassembled to observe the amount of bubbles in the solidified electrolyte. It was found that no bubbles were observed in the solidified electrolyte.

[0084] Comparative Example 3

[0085] The overall method is the same as in Example 1, except that in step 2, the reactant monomer is 5g of VC and the crosslinking agent is 0.5g. The other components and their added quantities are the same as in Example 1.

[0086] The prepared semi-solid battery was subjected to capacity, cycle, electrical performance tests, and safety performance tests such as nail penetration and overcharge. The cell was disassembled to observe the amount of air bubbles in the solidified electrolyte. No air bubbles were observed in the solidified electrolyte.

[0087] Comparative Example 4

[0088] The overall method is the same as in Example 1, except that the initiator mass in step 3 is 0.05g, and the mass of other components and materials added is the same as in Example 1.

[0089] The prepared semi-solid battery was subjected to capacity, cycle, electrical performance tests, and safety performance tests such as nail penetration and overcharge. The cell was disassembled to observe the amount of air bubbles in the solidified electrolyte. No air bubbles were observed in the solidified electrolyte.

[0090] Comparative Example 5

[0091] The overall method is the same as in Example 1, except that the mass of lithium salt in step 2 is 5g and the mass of lithium salt in step 3 is 1g. The other components and their added masses are the same as in Example 1.

[0092] The prepared semi-solid battery was subjected to capacity, cycle, electrical performance tests, and safety performance tests such as nail penetration and overcharge. The cell was disassembled to observe the amount of air bubbles in the solidified electrolyte. No air bubbles were observed in the solidified electrolyte.

[0093] Detection Example 1

[0094] 1. Cyclic testing: Cyclic testing is conducted according to the national standard GB / T31484-2015. The specific steps are as follows:

[0095] (a) Discharge to 2.75V with a constant current of 1I1(A);

[0096] (b) Let it sit for 30 minutes;

[0097] (c) Charge at a constant current of 1I1(A) to 4.2V, and then charge at a constant voltage to 0.05I1(A);

[0098] (d) Let it rest for 30 minutes;

[0099] (e) Discharge to 2.75V with a constant current of 1I1(A);

[0100] (f) Repeat steps (b) to (e) 100 to 1000 times.

[0101] 2. Needle penetration test: The needle penetration test is conducted according to the national standard GB / T31485-2015. The specific steps are as follows:

[0102] (a) The battery is charged at a constant current of 1I1(A) to 4.2V and then charged at a constant voltage of 0.05I1(A);

[0103] (b) Use a Φ5mm high-temperature resistant steel needle (the cone angle of the needle tip is 45°~60°, the surface of the needle is smooth, free of rust, oxide layer and oil stains), and penetrate from the direction perpendicular to the battery plate at a speed of (25±5)mm / s. The penetration position should be close to the geometric center of the pierced surface, and the steel needle stays in the battery.

[0104] (c) Observe for 1 hour.

[0105] Table 1. Statistics of battery test results for examples and comparative examples.

[0106]

[0107]

[0108] Results Analysis: As can be seen from the results of Examples 1-5, the in-situ polymerization process route of the present invention is applicable to a variety of in-situ polymerization systems and has a wide range of applications. The present invention can use one lithium salt system or two lithium salt systems (a small amount of lithium salt additives do not belong to the lithium salt system). The in-situ polymerization process route of the present invention has high compatibility with existing lithium-ion battery production lines and can prepare the required semi-solid batteries without the need for customized special equipment.

[0109] A comparison of the results of Examples 4 and 5 with those of Example 1 shows that the present invention can be extended to an in-situ polymerization system containing two monomers. The two polymerization systems prepared are intertwined, and the safety performance of the resulting semi-solid polymer battery is further improved.

[0110] A comparison of the results of Example 6 and Example 1 shows that...

[0111] A comparison of the results of the examples and Comparative Example 2 shows that the in-situ polymerization process of the present invention significantly improves the safety of the semi-solid battery compared with the conventional liquid lithium battery process. The semi-solid battery of the present invention can pass tests such as needle penetration and high voltage overcharging, which cannot be passed by liquid batteries.

Claims

1. A method for preparing a semi-solid-state pouch cell, wherein the semi-solid-state pouch cell comprises a dry cell, characterized in that, The preparation method includes the following steps: (1) In the dry cell, the first electrolyte injection is carried out, and electrolyte precursor one is injected. The electrolyte precursor one includes a reactive monomer, a crosslinking agent, a small molecule plasticizer and a lithium salt. (2) First transformation, then first venting; (3) Second injection: Inject electrolyte precursor II, which includes an initiator and a small molecule plasticizer, and may or may not include lithium salt. The reactants and crosslinking agents undergo in-situ polymerization under the action of the initiator. (4) Second transformation, then second venting; The mass fraction of the reactive monomer in electrolyte precursor 1 is 10%~18%; The mass fraction of the crosslinking agent in electrolyte precursor one is 1%~2.2%; The initiator has a mass fraction of 0.50% to 0.95% in the electrolyte precursor II; The mass fraction of lithium salt in electrolyte precursor one is 10%~15%; The mass fraction of lithium salt in electrolyte precursor II is 0%~15%; The other components in precursor one and precursor two are small molecule plasticizers; Electrolyte precursor one and electrolyte precursor two are added at a mass ratio of 1.8~1.9:

1.

2. The method for preparing the semi-solid-state pouch cell according to claim 1, characterized in that, The reactant monomer is at least one of the following: vinyl acetate, dimethyl allyl dicarboxylate, diethyl allyl malonate, methyl methacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, methyl methacrylate, butyl methacrylate, vinylene carbonate, ethylene ethylene carbonate, methyl vinyl sulfone, ethyl vinyl sulfone, ethoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, acrylamide, N,N-methylenebisacrylamide, etc. Butyrolactam, Acrylonitrile, 2-Acrylonitrile ethyl acrylate, 2-Acrylonitrile-2-butyl acrylate, 2-Acrylonitrile-3,3-Diphenylacrylate isooctyl acrylate, 1-Cyclohexeneacetonitrile, Hexafluorobutyl methacrylate, Trifluoroethyl methacrylate, Polyethylene glycol methacrylate, Polyethylene glycol dimethacrylate, Polyethylene glycol diacrylate, Ethoxyethyl acrylate, Polyethylene glycol, 1,3-Dioxolane, Dioxane, Vinylmethoxysilane, 2-(Trimethylsiloxy)methacrylate, Trivinylcyclotrisiloxane, Tri(2-methoxyethoxy)vinylsilane; The crosslinking agent is at least one of the following: polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, and polyether polyacrylate. The initiator is at least one of the following: azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, tert-butyl peroxide, and methyl ethyl ketone peroxide; The lithium salt is at least one of the following: LiBF4, LiBF6, LiAsF6, LiPF6, LiClO4, LiFSI, LiTFSI, LiB(C6H5)4, LiAlCl4, LiBr, LiCF3SO3, LiN(CF3SO2)2, LiC(CF3SOSO2)3; The small molecule plasticizer is at least one of the following: ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, fluorinated ethylene carbonate, dipropyl carbonate, dimethyl sulfoxide dimethoxyethane, N-methyl-2-pyrrolidone, γ-butyrolactone, and polyethylene glycol dimethyl ether.

3. The method for preparing the semi-solid-state pouch cell according to claim 1, characterized in that, In step (3), the temperature during in-situ polymerization is 60~90℃, the polymerization time is 0.1~72h, and the polymerization pressure is controlled at 0.2Mpa~500Mpa.

4. The method for preparing the semi-solid-state pouch cell according to claim 1, characterized in that, The conditions for the first formation are: charging current of 0.01C to 0.33C and charging time of 60 to 120 minutes; The conditions for the second formation are: charging current 0.01C~0.5C, and charging cut-off voltage is the rated voltage.

5. The method for preparing the semi-solid-state pouch cell according to claim 1, characterized in that, The exhaust time for the first and second exhausts is 1 to 20 seconds, and the exhaust vacuum is between -98 kPa and -20 kPa. After the first exhaust, high-temperature aging is carried out at a temperature of 45℃~80℃ for 12~120 hours. After the second venting, allow the mixture to stand for 1 to 30 minutes.

6. The method for preparing the semi-solid-state pouch cell according to claim 1, characterized in that, The ambient dew point during the first and second injections was controlled at -60℃ to -35℃, and the vacuum degree was -98kPa to -20kPa. After the first injection, the mixture was allowed to stand at room temperature for at least 48 hours.

7. A semi-solid-state pouch cell prepared by any of the preparation methods described in claims 1 to 6.

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