A semi-solid battery and a method of manufacturing the same

Abstract

This invention provides a semi-solid-state battery and its preparation method. The preparation method includes the following steps: assembling a positive electrode containing a first gel monomer, a negative electrode containing a second gel monomer, and a separator; then injecting an electrolyte; the first and second gel monomers undergoing polymerization reactions respectively to obtain the semi-solid-state battery; the first and second gel monomers independently contain cationic groups, anionic groups, and unsaturated bonds simultaneously. The semi-solid-state battery prepared by the method of this invention has good interfacial compatibility, excellent mechanical properties and ionic conductivity, and excellent high and low temperature cycling performance and electrolyte lock-in capability, solving the potential leakage risk of electrolyte and improving adaptability to extreme environments.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, and particularly relates to a semi-solid battery and a preparation method thereof. BACKGROUND

[0002] Lithium ion batteries, as the dominant chemical power technology, are widely used in new energy vehicles, energy storage systems and consumer electronics. However, the traditional liquid lithium ion battery uses flammable organic electrolyte, and has the risk of thermal runaway. Its safety problem has become the core bottleneck restricting the development of the industry. Semi-solid batteries are considered as an important transitional path to realize high-safety energy storage systems because they combine the safety of solid-state batteries with the excellent ion conductivity and interface contact characteristics of liquid batteries.

[0003] Although semi-solid batteries have broad prospects, their technical development still faces a series of severe challenges, which are rooted in the inherent defects of traditional material systems and preparation processes, mainly concentrated in the following aspects: first, in the traditional semi-solid battery, the electrolyte and electrode interface form a physical gap due to insufficient affinity, resulting in high interface impedance and inability to effectively inhibit the heterogeneous nucleation and growth of lithium dendrites, causing rapid capacity decay and short circuit risk; second, in the traditional process, the polymer monomer is directly dissolved in the electrolyte, and due to the fast diffusion rate and lack of gradient control of the polymerization reaction, it is easy to cause uneven distribution of the gel network on the electrode surface and the electrolyte body, form density difference, and result in high ion conductivity deviation rate, affecting the battery consistency; third, the traditional liquid monomer is easy to lose in the process of battery preparation and storage due to its strong volatility and insufficient thermal stability, and the liquid state may penetrate the electrode pores to damage the combination of active materials and adhesives, resulting in a decline in the structural integrity of the electrode; fourth, the traditional gel electrolyte relies on simple physical wrapping for electrolyte locking, and the polymer structure network is easy to break under high and low temperature cycles (-40~80℃) or mechanical impact, resulting in electrolyte leakage; the pre-polymerized gel electrolyte is difficult to balance high mechanical strength (high cross-linking is required) and high ion conductivity (low cross-linking is required) due to the formation of network structure in advance, and has poor wettability with the electrode.

[0004] CN119361841A discloses a method for preparing a gel semi-solid battery, comprising the following steps: (a) mixing a positive electrode active material, a positive electrode conductive agent, a gel monomer, an initiator, and a positive electrode binder to form a positive electrode material, and then fabricating a dry positive electrode sheet using a dry electrode technique; mixing a negative electrode active material, a negative electrode conductive agent, a gel monomer, an initiator, and a negative electrode binder to form a negative electrode material, and then fabricating a dry negative electrode sheet using a dry electrode technique; (b) providing a gel electrolyte prepolymer formed by mixing a gel monomer, an initiator, and an electrolyte; (c) assembling the dry positive electrode sheet and the dry negative electrode sheet obtained in step (a) with a separator to form a dry battery cell, injecting the gel electrolyte prepolymer obtained in step (b) into the dry battery cell and allowing it to stand and wet, and then heating it to perform in-situ polymerization and solidification to obtain a gel semi-solid battery. This patent involves adding gel monomers during electrode preparation and subsequently adding gel monomers to the electrolyte. This reduces the dissolution capacity of the monomers, resulting in uneven polymer concentration in the electrolyte and affecting the consistency of battery performance.

[0005] CN111019041A discloses a method for preparing a highly conductive, stretchable, compressible, and repairable zwitterionic gel polymer electrolyte, which is formed by in-situ polymerization of (2-(methacryloyloxy)ethyl)dimethyl-3-sulfopropyl)ammonium hydroxide, hydroxyethyl methacrylate, and lithium salt in the presence of an initiator. A zwitterionic SBMA, HEMA (a monomer that enhances mechanical properties without affecting conductivity), and LiCl are used to prepare a gel polymer electrolyte with good performance through a simple in-situ polymerization reaction. CN116247288A discloses a gel electrolyte prepared by in-situ polymerization and / or condensation of a bifunctional amide monomer, an initiator, lithium salt, and an organic solvent. The gel electrolyte can participate in the film-forming reaction on the electrolyte surface, thereby forming an organic-inorganic composite interfacial film, effectively reducing side reactions between the electrode and the electrolyte, resulting in excellent rate performance and cycle stability of the semi-solid-state battery, and ensuring the electrochemical performance of the semi-solid-state battery. However, the above-mentioned gel electrolytes suffer from a trade-off between mechanical properties, ionic conductivity, and interfacial compatibility.

[0006] Therefore, developing a semi-solid-state battery that can fundamentally improve interfacial compatibility while also achieving high ionic conductivity, excellent mechanical properties, and electrochemical stability has become an urgent technical problem to be solved in this field. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a semi-solid-state battery and its preparation method. This invention uses a gel monomer containing cationic groups, anionic groups, and unsaturated bonds, mixed with active materials, conductive agents, binders, and solvents to form a slurry. This slurry is then uniformly dispersed in the electrode, ensuring the smooth progress of the polymerization reaction and forming a gradient structure with gradually decreasing crosslinking density from the interface to the bulk. The semi-solid-state battery prepared using this method exhibits good interfacial compatibility, excellent mechanical properties and ionic conductivity, as well as excellent cycle performance and electrolyte lock-in capability. This solves the potential leakage problem of the electrolyte and improves adaptability to extreme environments.

[0008] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a semi-solid-state battery, the method comprising the following steps: A positive electrode containing a first gel monomer, a negative electrode containing a second gel monomer, and a separator are assembled, and then an electrolyte is injected. The first gel monomer and the second gel monomer undergo polymerization reactions respectively to obtain the semi-solid battery. The first gel monomer and the second gel monomer each independently contain cationic groups, anionic groups and unsaturated bonds.

[0009] This invention achieves molecular-level pre-bonding between the gel monomers and the electrode active material by uniformly dispersing the gel monomers in solid form within the electrode. This is achieved through hydrogen bonding or coordination between the anionic and cationic groups and the groups on the surface of the electrode active material (such as hydroxyl groups on lithium iron phosphate and carboxyl groups on graphite). This eliminates the physical gap between the electrolyte and the electrode, reducing interfacial impedance. After the electrolyte is injected into the battery cell, the gel monomers gradually dissolve from the electrode and preferentially polymerize at the electrode-electrolyte interface, forming a gel layer that adheres tightly to the electrode. This eliminates interfacial gaps and solves the problem of poor interfacial compatibility. Simultaneously, the high hydrophilicity and dynamic ionic environment of the gel monomers homogenize the lithium-ion flow, balance the lithium-ion migration rate, and prevent heterogeneous nucleation of lithium dendrites caused by localized high concentrations, effectively inhibiting lithium dendrite growth. As the gel monomers gradually diffuse, their dynamic coordination with lithium salts slows down the diffusion rate of the gel monomers. This slow release reduces the concentration fluctuation of the gel monomers in the electrolyte, allowing the polymerization reaction to proceed in a gradient from the interface to the electrolyte bulk, ensuring a uniform gel network structure, reducing the deviation rate of ionic conductivity, and improving the consistency of the battery.

[0010] This invention employs solid gel monomers, avoiding volatilization and thermal decomposition. Through synergy with the binder, these monomers are uniformly dispersed within the electrode sheet without compromising the electrode's porous structure and the bonding force between the active material, thus ensuring the integrity of the electrode structure. Furthermore, the gel network formed by gel monomers containing both anionic and cationic groups enhances cross-linking density and mechanical properties due to the strong electrostatic interactions and hydrogen bonding between zwitterions. This achieves a dual chemical and physical locking mechanism for the electrolyte, significantly improving locking capability and maintaining structural integrity even under extreme environments. This effectively prevents electrolyte leakage and precipitation, improving battery reliability in extreme application scenarios.

[0011] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0012] Preferably, the cationic group has any one of the following structures: ; The R1-R 15 Each is independently selected from C1-C12 alkyl groups.

[0013] Preferably, C1-C12 can be C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11 or C12.

[0014] Preferably, the C1-C12 alkyl group includes any one of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, hexyl, heptyl, octyl, nonyl, undecyl, or dodecyl.

[0015] Preferably, the anionic group includes -SO3 - -PO3 2- -OPO3 2- -OSO3 - Or any one of -SO2-, N-SO2-.

[0016] Preferably, the first gel monomer and the second gel monomer each independently comprise any one or a combination of at least two of the following: sulfobetaine methacrylate, sulfobetaine acrylamide, carboxybetaine methacrylate, 2-methacryloyloxyethyl phosphocholine, (3-(methacryloylamino)propyl)dimethyl(3-thiopropyl)ammonium hydroxide, 3-((2-(methacryloyloxy)ethyl)dimethylammonium)propionate, or sodium salt of 3-(N,N-dimethyl-(2-(2-methylprop-2-enoyloxy)ethyl)ammonium)propane-1-sulfonate.

[0017] Preferably, the first gel monomer and the second gel monomer each independently further include any one or a combination of at least two of the following: methyl methacrylate, pentaerythritol tetraacrylate, polyethylene glycol dimethacrylate, N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, or hydroxyethyl methacrylate.

[0018] Preferably, the polymerization reaction includes in-situ polymerization.

[0019] Preferably, the in-situ polymerization includes interface polymerization and bulk polymerization.

[0020] In this invention, in-situ polymerization is divided into two stages. First, the gel monomers in the electrode dissolve and rapidly polymerize at the electrode-electrolyte interface (interfacial polymerization) to form a highly cross-linked gel layer with a thickness of 5-20 μm, ensuring good wettability of the gel network to the electrode and high mechanical strength. Second, as the gel monomers continue to diffuse into the electrolyte, they continue to polymerize (bulk polymerization). The electrolyte bulk has a low degree of cross-linking to improve the ionic conductivity of the battery. The polymer electrolyte obtained by the in-situ polymerization method of this invention has a gradient structure with gradually decreasing cross-linking density from the interface to the bulk, avoiding the local over-cross-linking caused by rapid monomer diffusion in traditional processes, improving the consistency of battery performance, and solving the contradiction of difficulty in simultaneously achieving wettability, mechanical properties, and ionic conductivity.

[0021] Preferably, the polymerization reaction temperature is 40-80℃, such as 40℃, 44℃, 48℃, 52℃, 56℃, 60℃, 64℃, 68℃, 72℃, 76℃ or 80℃.

[0022] Preferably, the polymerization reaction time is 1-6 hours, such as 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, or 6 hours.

[0023] Preferably, the polymerization reaction is carried out in the presence of an initiator.

[0024] Preferably, the initiator is present in the electrolyte.

[0025] Preferably, the amount of the initiator is 0.5-4%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5% or 4%, with the sum of the amounts of the first gel monomer and the second gel monomer being 100%.

[0026] Preferably, the initiator includes any one or a combination of at least two of azobisisobutyronitrile, azobisisoheptanenitrile, or benzoyl peroxide.

[0027] Preferably, the positive electrode sheet includes a current collector, a positive electrode solid powder material, and a first gel monomer.

[0028] Preferably, the positive electrode solid powder material includes a positive electrode active material, a first conductive agent, and a first binder.

[0029] Preferably, the negative electrode sheet comprises a current collector, a negative electrode solid powder material, and a second gel monomer.

[0030] Preferably, the negative electrode solid powder material includes a negative electrode active material, a second conductive agent, and a second binder.

[0031] Preferably, based on the mass of the positive / negative electrode solid powder material as 100%, the amount of the first gel monomer and the second gel monomer is independently 0.6%-7%, for example, 0.6%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5% or 7%, etc.

[0032] Preferably, the positive electrode solid powder material comprises, by mass percentage, 90%-97% positive electrode active material, 0.5%-5% first conductive agent, and 1%-5% first binder.

[0033] Preferably, the negative electrode solid powder material comprises, by mass percentage, 90%-95% negative electrode active material, 0.5%-5% second conductive agent, and 1%-5% second binder.

[0034] Preferably, the amount of the positive electrode active material can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, or 97%, etc.

[0035] Preferably, the amount of the negative electrode active material can be 90%, 91%, 92%, 93%, 94%, or 95%, etc.

[0036] Preferably, the amounts of the first conductive agent and the second conductive agent can each be independently 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, etc.

[0037] Preferably, the amount of the first adhesive and the second adhesive in the positive / negative electrode sheet can be independently 1%, 2%, 3%, 4% or 5%, etc.

[0038] Preferably, the positive electrode active material includes any one or a combination of at least two of lithium iron phosphate, lithium cobalt oxide, ternary nickel cobalt manganese, ternary nickel cobalt aluminum, lithium nickel oxide, lithium manganese oxide, lithium manganese iron phosphate, lithium-rich manganese-based materials, or sulfides.

[0039] Preferably, the negative electrode active material includes any one or a combination of at least two of graphite, lithium foil, lithium metal composite negative electrode, silicon-carbon composite material, or lithium titanate.

[0040] Preferably, the first adhesive and the second adhesive each independently comprise any one or a combination of at least two of polyvinylidene fluoride, polyacrylic acid, sodium alginate, styrene-butadiene rubber, or sodium carboxymethyl cellulose.

[0041] Preferably, the first conductive agent and the second conductive agent each independently comprise any one or a combination of at least two of conductive carbon black, acetylene black, carbon nanotubes, graphene, or carbon nanofibers.

[0042] Preferably, the electrolyte comprises lithium salt, solvent, and additives.

[0043] Preferably, the lithium salt comprises any one or a combination of at least two of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, or lithium bis(fluorosulfonyl)imide.

[0044] Preferably, the solvent includes any one or a combination of at least two of the following: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, fluoroethylene carbonate, vinylene carbonate, ethyl acetate, methyl acetate, ethyl propionate, 1,3-dioxolane, 1,2-dimethoxyethane, or ethyl methyl carbonate.

[0045] Preferably, the additive includes any one or a combination of at least two of vinyl sulfate, propylene sulfonate lactone, tris(trimethylsilyl) phosphate, trimethyl phosphate, biphenyl, lithium difluorooxalate borate, lithium difluorobis(oxalate) phosphate, or lithium difluorophosphate.

[0046] Preferably, the amount of the additive is 0.2-5% based on 100% of the electrolyte mass, for example, 0.2%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%.

[0047] Preferably, the concentration of the lithium salt is 0.5-2 mol / L, such as 0.5 mol / L, 1 mol / L, 1.5 mol / L or 2 mol / L.

[0048] Preferably, the preparation method specifically includes the following steps: (1) According to the formula dosage, the positive electrode active material, the first conductive agent, the first binder, the first gel monomer and the first solvent are mixed to form a slurry, which is coated on the positive electrode current collector, dried and rolled to obtain the positive electrode sheet; According to the formula dosage, the negative electrode active material, the second conductive agent, the second binder, the second gel monomer and the second solvent are mixed to form a slurry, which is then coated on the negative electrode current collector, dried and rolled to obtain the negative electrode sheet. (2) Assemble the positive electrode, the negative electrode and the separator, inject electrolyte, add initiator, and polymerize at 40-80℃ for 1-6 hours to obtain the semi-solid battery; The first gel monomer and the second gel monomer each independently contain cationic groups, anionic groups and unsaturated bonds simultaneously; The cationic group has any one of the following structures: ; The R1-R 15 Each is independently selected from C1-C12 alkyl groups; The anionic group includes -SO3 - -PO3 2- -OPO3 2- -OSO3 - Or any one of -SO2-, N-, or SO2-; The polymerization reaction includes in-situ polymerization; The in-situ aggregation includes interface aggregation and bulk aggregation; The first solvent and the second solvent each independently comprise water and / or N-methylpyrrolidone.

[0049] In a second aspect, the present invention provides a semi-solid battery, which is prepared by the preparation method described in the first aspect.

[0050] Compared with the prior art, the present invention has the following beneficial effects: (1) The gel monomers of the present invention are uniformly dispersed in the electrode in solid form and preferentially polymerize at the electrode-electrolyte interface to form a gel layer that is molecularly bonded to the electrode surface; at the same time, the gel layer forms hydrogen bonds or coordination interactions with the active substances on the electrode surface through anionic and cationic groups, eliminating the physical gap between the electrode and the electrolyte, and reducing the interfacial resistance to 40 Ω·cm. 2 the following.

[0051] (2) The highly hydrophilic amphoteric gel layer formed by in-situ polymerization in this invention can form a stable hydration film, and the dynamic charge distribution of the zwitterionic ions of the gel monomer can homogenize the lithium ion flow, balance the lithium ion migration rate, avoid the heterogeneous nucleation of lithium dendrites caused by local high concentration, and effectively suppress the growth of dendrites on the surface of lithium anode.

[0052] (3) The composite membrane (gel + diaphragm) of the present invention has excellent mechanical properties, with a puncture resistance strength between 490-520 gf and a Young's modulus between 80-90 MPa, which provides a guarantee for effectively inhibiting the growth of lithium dendrites.

[0053] (4) The gel polymer network in this invention has a gradient structure with a gradually decreasing crosslinking density from the interface to the bulk. The interface has a high crosslinking density and the electrolyte bulk has a low crosslinking density, which helps ion transport and has good ionic conductivity. The ionic conductivity at 25℃ is 7.0-7.8 mS / cm. At the same time, this polymerization method avoids the local over-crosslinking caused by the rapid diffusion of monomers in traditional processes, making the polymer network structure more uniform and significantly improving the consistency of battery performance.

[0054] (5) The semi-solid battery provided by the present invention has a high capacity retention rate and high and low temperature cycling characteristics. After 500 charge-discharge cycles at 45℃, the capacity retention rate is 90%-92%, and after 500 charge-discharge cycles at -10℃, the capacity retention rate is 78%-81.1%.

[0055] (6) The gel polymer network in this invention has excellent liquid retention capacity, effectively locking in a large amount of electrolyte, and the liquid retention performance of the cell is between 97-99%.

[0056] (7) In this invention, the gel monomer exists in the electrode in solid form, and its thermal decomposition temperature is 30-50°C higher than that of liquid monomer, with no loss of volatility. During battery preparation and storage, the monomer retention rate is effectively improved compared to the traditional liquid addition method, avoiding incomplete polymerization caused by monomer loss. The gel monomer works together with the binder and does not penetrate and damage the bonding between the active material and the current collector like liquid monomer, which is beneficial to maintaining the integrity of the electrode structure. Detailed Implementation

[0057] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0058] The sources of information for some of the raw materials in this invention embodiment are as follows: Polyvinylidene fluoride: Shanghai Yuanye Biotechnology Co., Ltd., S25907; Acetylene Black: Shanghai Xianding Biotechnology Co., Ltd., MY38641; Graphite: Shanghai Shanshan Technology Co., Ltd., EP5-H; Styrene-butadiene rubber: Shanghai Maclean Biochemical Technology Co., Ltd., P728771; Carbon nanotubes: Shanghai McLean Biochemical Technology Co., Ltd., G991390; Sodium carboxymethyl cellulose: Shanghai Aladdin Biochemical Technology Co., Ltd., S1373765; Diaphragm: Shanghai Enjie New Material Technology Co., Ltd., wet-process biaxially oriented diaphragm.

[0059] Example 1 This embodiment provides a method for preparing a semi-solid-state battery, the method comprising the following steps: (1) Add 85g of lithium iron phosphate, 3g of acetylene black, 5g of polyvinylidene fluoride and 6g of 2-methacryloyloxyethyl choline phosphate to 1000mL of N-methylpyrrolidone, stir mechanically at 2000rpm for 0.5h to make a slurry, coat it on the aluminum foil of the positive current collector, and dry and roll to obtain the positive electrode sheet. Add 88g of graphite, 5g of acetylene black, 5g of polyvinylidene fluoride, and 2g of 2-methacryloyloxyethyl phosphocholine to 1000mL of deionized water. Stir mechanically at 2000rpm for 0.5h to make a slurry. Coat the negative electrode current collector copper foil with the slurry, and then dry and roll to obtain the negative electrode sheet. (2) Mix ethylene carbonate, propylene carbonate and diethyl carbonate in a volume ratio of 1:2:2 to a total volume of 1L, add LiPF6 and 6.47g of ethylene sulfate to prepare a 1mol / L LiPF6 electrolyte. The positive electrode, the negative electrode, and the separator are assembled, and an electrolyte is injected with an injection coefficient of 2 g / Ah. 1% azobisisobutyronitrile is added, and the polymerization reaction is carried out at 70°C for 3 h to obtain the semi-solid battery.

[0060] Example 2 This embodiment provides a method for preparing a semi-solid-state battery, the method comprising the following steps: (1) In 1000mL of N-methylpyrrolidone, add 90g of lithium manganese oxide, 5g of conductive carbon black, 2g of styrene-butadiene rubber, and 3g of (3-(methacrylamide)propyl)dimethyl(3-thiopropyl)ammonium hydroxide, and mechanically stir at 2000rpm for 0.5h to make a slurry. Coat the slurry onto the positive current collector aluminum foil, and after drying and rolling, obtain the positive electrode sheet. Add 90g of graphite, 2g of conductive carbon black, 7g of styrene-butadiene rubber, and 1g of (3-(methacryloylamino)propyl)dimethyl(3-thiopropyl)ammonium hydroxide to 1000mL of deionized water. Stir mechanically at 2000rpm for 0.5h to make a slurry. Coat the negative electrode current collector copper foil with the slurry, and then dry and roll to obtain the negative electrode sheet. (2) Ethyl propionate, methyl ethyl carbonate and diethyl carbonate were mixed in a volume ratio of 2:1:1 to a total volume of 1L. Lithium bis(trifluoromethanesulfonylimide) (LiTFSI) and 7.61g of propylene sulfonate lactone were added to prepare a 2mol / L electrolyte. The positive electrode, the negative electrode, and the separator are assembled, and an electrolyte is injected with an injection coefficient of 2 g / Ah. 1.8% azobisisoheptanenitrile is added, and the polymerization reaction is carried out at 80°C for 1 h to obtain the semi-solid battery.

[0061] Example 3 This embodiment provides a method for preparing a semi-solid-state battery, the method comprising the following steps: (1) In 1000mL of N-methylpyrrolidone, add 75g of lithium manganese iron phosphate, 15g of carbon nanotubes, 8g of sodium carboxymethyl cellulose and 2g of 3-((2-(methacryloyloxy)ethyl)dimethylammonium)propionate, and mechanically stir at 2000rpm for 0.5h to make a slurry. Coat the slurry onto the aluminum foil of the positive current collector, and after drying and rolling, obtain the positive electrode sheet. Add 78g of graphite, 10g of carbon nanotubes, 8g of sodium carboxymethyl cellulose, and 4g of 3-((2-(methacryloyloxy)ethyl)dimethylammonium)propionate to 1000mL of deionized water. Stir mechanically at 2000rpm for 0.5h to make a slurry. Coat the slurry onto the copper foil of the negative electrode current collector. After drying and rolling, the negative electrode sheet is obtained. (2) Mix ethylene carbonate, 1,2-dimethoxyethane and propylene carbonate in a volume ratio of 1:3:2 to a total volume of 1L, add lithium difluorosulfonylimide (LiFSI) and 14.4g of lithium difluorooxalate borate to prepare a 2mol / L electrolyte. The positive electrode, the negative electrode, and the separator are assembled, and an electrolyte is injected with an injection coefficient of 2 g / Ah. 0.5% benzoyl peroxide is added, and the polymerization reaction is carried out at 40°C for 6 h to obtain the semi-solid battery.

[0062] Example 4 The only difference between this embodiment and Embodiment 1 is that the raw materials for preparing the positive electrode sheet include: 83g of lithium iron phosphate, 3g of acetylene black, 5g of polyvinylidene fluoride, and 9g of 2-methacryloyloxyethyl phosphocholine. The raw materials for preparing the negative electrode sheet include: 84g of graphite, 3g of acetylene black, 5g of polyvinylidene fluoride, and 8g of 2-methacryloyloxyethyl phosphocholine. The rest are the same as in Example 1.

[0063] Example 5 The only difference between this embodiment and Example 1 is that the polymerization temperature is 35°C and the polymerization time is 8 hours; all other aspects are the same as in Example 1.

[0064] Example 6 The only difference between this embodiment and Example 1 is that the polymerization temperature is 85°C and the polymerization time is 3 hours. All other aspects are the same as in Example 1.

[0065] Comparative Example 1 The only difference between this comparative example and Example 1 is that 2-methacryloyloxyethyl phosphocholine is replaced with an equal amount of hydroxyethyl methacrylate; all other aspects are the same as in Example 1.

[0066] Comparative Example 2 The preparation method of the semi-solid-state battery in this comparative example includes the following steps: (1) Add 85g of lithium iron phosphate, 3g of acetylene black and 5g of polyvinylidene fluoride to 1000mL of N-methylpyrrolidone, stir mechanically at 2000rpm for 0.5h to make a slurry, coat it on the aluminum foil of the positive current collector, and obtain the positive electrode sheet by drying and rolling. Add 88g of graphite, 5g of acetylene black, and 5g of polyvinylidene fluoride to 1000mL of deionized water, and mechanically stir at 2000rpm for 0.5h to make a slurry. Coat the negative electrode current collector copper foil, and after drying and rolling, obtain the negative electrode sheet. (2) Mix ethylene carbonate, propylene carbonate and diethyl carbonate in a volume ratio of 1:2:2 to a total of 1L, add 8g of 2-methacryloyloxyethyl phosphocholine, then add LiPF6 and 6.47g of ethylene sulfate to prepare a 1mol / L electrolyte. The positive electrode, the negative electrode, and the separator are assembled, and an electrolyte is injected with an injection coefficient of 2 g / Ah. 1% azobisisobutyronitrile is added, and the polymerization reaction is carried out at 70°C for 3 h to obtain the semi-solid battery.

[0067] Comparative Example 3 The only difference between this comparative example and Example 1 is that the preparation method includes the following steps: (1) Add 85g of lithium iron phosphate, 3g of acetylene black, 5g of polyvinylidene fluoride and 4g of 2-methacryloyloxyethyl choline phosphate to 1000mL of N-methylpyrrolidone, stir mechanically at 2000rpm for 0.5h to make a slurry, coat it on the positive current collector aluminum foil, and dry and roll to obtain the positive electrode sheet. Add 88g of graphite, 5g of acetylene black, 5g of polyvinylidene fluoride, and 2g of 2-methacryloyloxyethyl phosphocholine to 1000mL of deionized water. Stir mechanically at 2000rpm for 0.5h to make a slurry. Coat the negative electrode current collector copper foil with the slurry, and then dry and roll to obtain the negative electrode sheet. (2) Mix ethylene carbonate, propylene carbonate and diethyl carbonate in a volume ratio of 1:2:2 to a total of 1L, add 2g of 2-methacryloyloxyethyl phosphocholine, then add LiPF6 and 6.47g of ethylene sulfate to prepare a 1mol / L electrolyte. The positive electrode, the negative electrode, and the separator are assembled, and an electrolyte is injected with an injection coefficient of 2 g / Ah. 1% azobisisobutyronitrile is added, and the polymerization reaction is carried out at 70°C for 3 h to obtain the semi-solid battery.

[0068] Performance testing: (1) Interface resistance: Referencing IEC 61960-3:2017, a standard for electrical engineering and batteries, the electrochemical AC impedance method was used. A Shanghai Chenhua electrochemical workstation was employed. The typical value was 5~10mV, and over an ultra-wide frequency range (typically 10mV). 6 Hz~10 - 2 The impedance spectrum of the system was obtained by scanning within Hz.

[0069] (2) Puncture resistance: Referring to GB / T 36363-2018 "Polyolefin separators for lithium-ion batteries", 30×30mm square samples (including the base separator and gel electrolyte) were prepared using an electronic universal testing machine, 10 pieces / batch (average value of 10 pieces). The samples were left to stand for 4 hours in an environment of 23±2℃ and 50±10%RH. Before testing, it was confirmed that the gel was free of bubbles, wrinkles, and damage, and that the thickness was uniform. The gel sample was placed flat in the center of the ring clamp, moderately tensioned (to avoid stretching deformation), and clamped evenly to ensure that the sample was perpendicular to the clamp. The puncture needle was adjusted to be directly above the center of the sample, with the needle tip 2-5mm away from the sample surface. The puncture speed was 100±10mm / min. The sampling frequency was ≥100Hz. The force-displacement curve was automatically recorded until the test was completed.

[0070] (3) Young's modulus: Refer to GB / T 1040.3-2006 Tensile properties of plastics - Part 3: Films and sheets. Use an electronic universal testing machine to measure the thickness of the sample (including the base membrane and gel electrolyte) at 3 points and take the average value d (mm). Place the sample in the anti-slip clamp, ensuring it is vertical, not skewed, and not pre-stretched. Set the gauge length to 20 mm, start the stretching, and the machine will automatically record the stress-strain curve. Stop when the sample breaks or elongates to 100%. Measure 5 parallel samples, remove outliers, and take the average value. The slope of the initial straight segment of the stress-strain curve = Young's modulus.

[0071] (4) Ionic conductivity: Refer to GB / T 20042.3-2020 Proton exchange membranes Part 3: Conductivity determination. Prepare the sample in a glove box, measure its thickness, assemble a symmetrical cell, place it in a constant temperature environment of 25℃ for 30 min, and use the Shanghai Chenhua electrochemical workstation to perform electrochemical impedance spectroscopy to obtain the Nyquist curve. Take the intersection of the high frequency and the real axis as the bulk resistance Rb (Ω). Perform parallel tests 3 to 5 times and take the average value.

[0072] (5) Capacity retention rate after high and low temperature cycling: Referring to GB / T 31484-2015 Requirements and test methods for cycle life of power batteries for electric vehicles, the cycle performance of the cells was tested using a battery charge-discharge tester and a high and low temperature test chamber. Cell activation: 3 cycles at 25℃ with a small current (0.1C~0.2C) to stabilize the capacity. The initial capacity C0 was measured. 3 cycles of charge-discharge at 25℃ and 0.5C were performed, and the discharge capacity of the 3rd cycle was taken as the initial capacity C0. High and low temperature cycling: The cells were placed in the high and low temperature chamber, the temperature was set, and continuous cycling was performed at 0.5C. Capacity Cn was remeasured after cycling: After the cycle was completed, the cells were placed back at 25℃ for 2 hours and discharged at 0.5C to measure Cn. Parallel samples: ≥3 cells per group, and the average value was taken. Capacity retention rate = Cn / C0 × 100%.

[0073] (6) Cell liquid retention performance: Referring to GB / T 43568-2026, the soft-pack battery was discharged to 0V (0% SOC) using a charge-discharge tester and left to stand for 1 hour; a puncture (length ≥ 2 cm) was made at the side seal of the soft-pack battery with a ceramic scalpel in a glove box, and the battery was inverted for 30 minutes; the mass of the sample after the puncture (m1, accuracy 0.1 mg) was accurately weighed using an analytical balance and recorded as the initial mass; the sample was placed in a high-temperature resistant sealed weighing bottle and placed in a vacuum drying oven with the following parameters set: temperature: 120℃, vacuum degree: ≤ 10 Pa, baking time: 6 h, heating rate: 5℃ / min (to avoid thermal shock to the sample), the program was started, and the timing was started after the temperature stabilized, maintaining a vacuum state throughout the process. After baking, the sample was kept in a vacuum state and cooled to room temperature (about 2 h) to prevent the sample from absorbing moisture; the sample was quickly transferred to a sealed weighing bottle in a glove box, and the final mass (m2, accuracy 0.1 mg) was immediately weighed. The weighing was repeated 3 times, and the average value was taken, with a relative deviation ≤ 0.1%. The liquid retention rate is calculated using the following formula: Liquid retention rate = (m1-m2) / m1 × 100%.

[0074] The semi-solid-state batteries provided in the examples and comparative examples were tested according to the above test methods. The test results are shown in Table 1. Table 1 As shown in Table 1, the semi-solid-state battery provided by this invention has a low interface resistance of 40 Ω·cm. 2The following characteristics are observed: excellent mechanical properties, with puncture resistance between 490-520 gf and Young's modulus between 80-90 MPa, effectively suppressing dendrite growth; good ionic conductivity, with an ionic conductivity of 7.0-7.8 mS / cm at 25℃; high capacity retention and resistance to high and low temperature cycling, with a capacity retention of 90%-92% after 500 charge-discharge cycles at 45℃ and 78%-81.1% after 500 charge-discharge cycles at -10℃; and excellent liquid retention capacity, with a cell liquid retention performance between 97-99%.

[0075] As can be seen from the comparison between Example 1 and Example 4, the overall performance of the battery is excellent when the amount of gel monomer used in the present invention is in the range of 0.6-7%. If the amount is too large, it will lead to an increase in interface resistance, a decrease in Young's modulus, puncture resistance and ionic conductivity, a decrease in capacity retention after high and low temperature cycling, and a decrease in the liquid retention performance of the cell.

[0076] As can be seen from the comparison between Examples 1 and Examples 5-6, if the temperature and time of the polymerization reaction are not within the limits of the present invention, the interfacial resistance increases sharply, Young's modulus, puncture resistance and ionic conductivity decrease, the capacity retention rate after high and low temperature cycling deteriorates, and the liquid retention performance of the cell decreases.

[0077] In Comparative Example 1, hydroxyethyl methacrylate was used as the gel monomer. In Comparative Example 2, all the gel monomers were added to the electrolyte for polymerization. In Comparative Example 3, part of the gel monomers were distributed in the electrode and part were in the electrolyte. All of these results in a sharp increase in interfacial resistance, an increase in Young's modulus, a decrease in puncture resistance and ionic conductivity, and a decrease in capacity retention and electrolyte retention performance of the cell after high and low temperature cycling.

[0078] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a semi-solid-state battery, characterized in that, The preparation method includes the following steps: A positive electrode containing a first gel monomer, a negative electrode containing a second gel monomer, and a separator are assembled, and then an electrolyte is injected. The first gel monomer and the second gel monomer undergo polymerization reactions respectively to obtain the semi-solid battery. The first gel monomer and the second gel monomer each independently contain cationic groups, anionic groups and unsaturated bonds.

2. The preparation method according to claim 1, characterized in that, The cationic group has any one of the following structures: ； The R1-R 15 Each is independently selected from C1-C12 alkyl groups; Preferably, the anionic group includes -SO3. - -PO3 2- -OPO3 2- -OSO3 - Or any one of -SO2-, N-, or SO2-; Preferably, the first gel monomer and the second gel monomer each independently comprise any one or a combination of at least two of the following: sulfobetaine methacrylate, sulfobetaine acrylamide, carboxybetaine methacrylate, 2-methacryloyloxyethyl phosphocholine, (3-(methacryloylamino)propyl)dimethyl(3-thiopropyl)ammonium hydroxide, 3-((2-(methacryloyloxy)ethyl)dimethylammonium)propionate, or sodium salt of 3-(N,N-dimethyl-(2-(2-methylprop-2-enoyloxy)ethyl)ammonium)propane-1-sulfonate. Preferably, the first gel monomer and the second gel monomer each independently further include any one or a combination of at least two of the following: methyl methacrylate, pentaerythritol tetraacrylate, polyethylene glycol dimethacrylate, N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, or hydroxyethyl methacrylate.

3. The preparation method according to claim 1 or 2, characterized in that, The polymerization reaction includes in-situ polymerization; Preferably, the in-situ polymerization includes interface polymerization and bulk polymerization; Preferably, the polymerization reaction is carried out at a temperature of 40-80°C; Preferably, the polymerization reaction takes 1-6 hours.

4. The preparation method according to any one of claims 1-3, characterized in that, The polymerization reaction is carried out in the presence of an initiator; Preferably, the initiator is present in the electrolyte; Preferably, the amount of the initiator is 0.5-4%, based on the sum of the amounts of the first gel monomer and the second gel monomer being 100%. Preferably, the initiator includes any one or a combination of at least two of azobisisobutyronitrile, azobisisoheptanenitrile, or benzoyl peroxide.

5. The preparation method according to any one of claims 1-4, characterized in that, The positive electrode sheet includes a current collector, a positive electrode solid powder material, and a first gel monomer; Preferably, the positive electrode solid powder material includes a positive electrode active material, a first conductive agent, and a first binder; Preferably, the negative electrode sheet comprises a current collector, a negative electrode solid powder material, and a second gel monomer; Preferably, the negative electrode solid powder material includes a negative electrode active material, a second conductive agent, and a second binder; Preferably, based on the mass of the positive / negative electrode solid powder material as 100%, the amount of the first gel monomer and the second gel monomer is independently 0.6%-7% each.

6. The preparation method according to any one of claims 1-5, characterized in that, The positive electrode solid powder material comprises, by mass percentage, 90%-97% positive electrode active material, 0.5%-5% first conductive agent, and 1%-5% first binder; Preferably, the negative electrode solid powder material comprises, by mass percentage, 90%-95% negative electrode active material, 0.5%-5% second conductive agent, and 1%-5% second binder.

7. The preparation method according to any one of claims 1-6, characterized in that, The positive electrode active material includes any one or a combination of at least two of lithium iron phosphate, lithium cobalt oxide, ternary nickel cobalt manganese, ternary nickel cobalt aluminum, lithium nickel oxide, lithium manganese oxide, lithium manganese iron phosphate, lithium-rich manganese-based or sulfides. Preferably, the negative electrode active material includes any one or a combination of at least two of graphite, lithium foil, lithium metal composite negative electrode, silicon-carbon composite material or lithium titanate; Preferably, the first adhesive and the second adhesive each independently comprise any one or a combination of at least two of polyvinylidene fluoride, polyacrylic acid, sodium alginate, styrene-butadiene rubber, or sodium carboxymethyl cellulose; Preferably, the first conductive agent and the second conductive agent each independently comprise any one or a combination of at least two of conductive carbon black, acetylene black, carbon nanotubes, graphene, or carbon nanofibers.

8. The preparation method according to any one of claims 1-7, characterized in that, The electrolyte includes lithium salt, solvent, and additives; Preferably, the lithium salt comprises any one or a combination of at least two of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, or lithium bis(fluorosulfonyl)imide. Preferably, the solvent includes any one or a combination of at least two of the following: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, fluoroethylene carbonate, vinylene carbonate, ethyl acetate, methyl acetate, ethyl propionate, 1,3-dioxolane, 1,2-dimethoxyethane, or ethyl methyl carbonate. Preferably, the additive includes any one or a combination of at least two of the following: vinyl sulfate, propylene sulfonate lactone, tris(trimethylsilyl) phosphate, trimethyl phosphate, biphenyl, lithium difluorooxalate borate, lithium difluorobis(oxalate) phosphate, or lithium difluorophosphate. Preferably, the amount of the additive is 0.2-5% based on 100% of the mass of the electrolyte; Preferably, the concentration of the lithium salt is 0.5-2 mol / L.

9. The preparation method according to any one of claims 1-8, characterized in that, The preparation method specifically includes the following steps: (1) According to the formula dosage, the positive electrode active material, the first conductive agent, the first binder, the first gel monomer and the first solvent are mixed to form a slurry, which is coated on the positive electrode current collector, dried and rolled to obtain the positive electrode sheet; According to the formula dosage, the negative electrode active material, the second conductive agent, the second binder, the second gel monomer and the second solvent are mixed to form a slurry, which is then coated on the negative electrode current collector, dried and rolled to obtain the negative electrode sheet. (2) Assemble the positive electrode, the negative electrode and the separator, inject electrolyte, add initiator, and polymerize at 40-80℃ for 1-6 hours to obtain the semi-solid battery; The first gel monomer and the second gel monomer each independently contain cationic groups, anionic groups and unsaturated bonds simultaneously; The cationic group has any one of the following structures: ； The R1-R 15 Each is independently selected from C1-C12 alkyl groups; The anionic group includes -SO3 - -PO3 2- -OPO3 2- -OSO3 - Or any one of -SO2-, N-, or SO2-; The polymerization reaction includes in-situ polymerization; The in-situ aggregation includes interface aggregation and bulk aggregation; The first solvent and the second solvent each independently comprise water and / or N-methylpyrrolidone.

10. A semi-solid-state battery, characterized in that, The semi-solid battery is prepared by the preparation method according to any one of claims 1-9.

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