WO2023226345A1 - 一种自由基原位聚合半固态电池 - Google Patents

一种自由基原位聚合半固态电池 Download PDF

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WO2023226345A1
WO2023226345A1 PCT/CN2022/134971 CN2022134971W WO2023226345A1 WO 2023226345 A1 WO2023226345 A1 WO 2023226345A1 CN 2022134971 W CN2022134971 W CN 2022134971W WO 2023226345 A1 WO2023226345 A1 WO 2023226345A1
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semi
situ polymerization
lithium
solid
free radical
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English (en)
French (fr)
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曹辉
崔屹
侯敏
聂荣荣
刘婵
陈丹丹
刘微
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瑞浦兰钧能源股份有限公司
上海瑞浦青创新能源有限公司
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the invention belongs to the technical field of batteries, relates to the technical field of semi-solid batteries, and specifically relates to a free radical in-situ polymerization semi-solid battery.
  • lithium-ion batteries With the increasingly urgent demand for improving the energy density of lithium-ion batteries, traditional lithium-ion batteries have been difficult to meet the demand for ultra-high specific energy.
  • commercialized lithium battery anode materials are mainly modified natural graphite and artificial graphite. Although the preparation technology is quite mature, the theoretical specific capacity of graphite is only 372mAh ⁇ g -1 , which is difficult to meet the market demand for high energy density lithium-ion batteries. . Therefore, based on the demand for high energy density batteries, anode materials with ultra-high specific energy advantages have become a research hotspot. For example: silicon anode, metal alloy anode and lithium metal anode. Taking silicon anode materials as an example, currently a certain amount of silicon material is mainly used to increase the specific capacity.
  • the metallic lithium anode As an example, its specific capacity is 3860mAh ⁇ g -1 and the electrochemical potential is -3.04V (vs. standard hydrogen electrode). Batteries made of these anode materials can effectively increase energy density and can even reach over 400Wh kg -1 or even higher. Medium and high nickel ternary lithium batteries have high activity, and when paired with high specific capacity negative electrode materials, while increasing the specific energy density, improving battery safety is also a top priority.
  • Semi-solid batteries can effectively reduce the usage of liquid electrolyte in the battery. While increasing the energy density of the battery, it also simultaneously reduces potential safety hazards caused by liquid electrolyte.
  • the semi-solid gel electrolyte can effectively inhibit the change of the negative electrode structure and the growth of metal dendrites to a certain extent, which can greatly improve the safety of the battery while increasing the specific energy.
  • existing semi-solid gel electrolytes often have shortcomings such as higher battery impedance and greater performance loss after polymerization.
  • CN 112018438 A uses vinylene carbonate as the gel polymerization monomer, azobisisobutyronitrile as the initiator, and is combined with an acrylic ester flexibility agent and cross-linking agent to initiate in-situ polymerization.
  • vinylene carbonate as the gel polymerization monomer
  • azobisisobutyronitrile as the initiator
  • acrylic ester flexibility agent and cross-linking agent to initiate in-situ polymerization.
  • its component combination and content will also lead to higher impedance of the polymerized battery and greater performance loss.
  • the purpose of the present invention is to provide a free radical in-situ polymerization semi-solid battery; the present invention uses an in-situ polymerization method to prepare and produce a semi-solid battery, specifically using polymerized monomers, plasticizers and initiators. points, forming a semi-solid electrolyte under certain conditions.
  • the invention provides a free radical in-situ polymerization semi-solid battery, which includes a positive electrode, a negative electrode and a semi-solid electrolyte.
  • the semi-solid electrolyte is a semi-solid electrolyte formed by in-situ polymerization of polymerized monomers, plasticizers and initiators added to a liquid electrolyte.
  • Solid electrolyte; the polymerized monomer is a combination of vinylene carbonate VC and trimethylene carbonate TMC with a mass ratio of 20-35:0.1-1.5.
  • the liquid electrolyte contains lithium salts.
  • the lithium salt may be selected from the group consisting of lithium hexafluorophosphate LiPF6, lithium difluorophosphate LiPO2F2, lithium bisfluorosulfonimide LiFSI, lithium bistrifluoromethanesulfonimide LiTFSI, lithium trifluoromethanesulfonate LiCF3SO3, and lithium tetrafluoroborate.
  • LiBF4 lithium bisoxaloborate LiBOB, lithium difluoroborate borate LiODFB, and lithium difluorobisoxalate phosphate LiDFBP.
  • the polymerized monomer is preferably a combination of vinylene carbonate VC and trimethylene carbonate TMC with a mass ratio of 20-35:0.1-1.5. It is preferred that the total content of polymerized monomers VC and TMC in the semi-solid electrolyte is 20-36.5wt.%, such as 20-30wt.%, 25wt.%, 27wt.%, 29wt.%. Preferably, the content of polymerized monomer VC in the semi-solid electrolyte is 20-35wt.%, such as 20-29wt.%, 25wt.%, 27wt.%, 28wt.%, and the TMC content is 0.1-1.5wt.%, such as 0.5-1wt.
  • VC is the main polymerization monomer
  • TMC is the auxiliary polymerization monomer, both of which are indispensable.
  • the main function of TMC after polymerization is to increase the viscosity of the polymerized VC-based semi-solid electrolyte. If TMC is used as the main polymerized monomer and VC is used as a supplement, the semi-solid electrolyte will be unstable and cannot effectively form a semi-solid electrolyte.
  • the plasticizer is selected from the group consisting of polyvinyl alcohol PEG, polyethylene glycol dimethyl ether PEGDME, dibutyl phthalate DBP, dimethyl phthalate DMP, dibutyl phthalate One or more of octyl DOP, acetonitrile ACN, succinonitrile SN, and thermoplastic polyurethane TPU.
  • the plasticizer is preferably succinonitrile SN.
  • Succinonitrile SN has a relatively stable structure. It has good ionic conductivity, good thermal stability and high oxidation stability. It is used in semi-solid electrolytes and helps to increase the resistance of semi-solid electrolytes at high temperatures and high voltages. stability with less negative impact on impedance and performance.
  • the initiator is selected from 2,2-azobisisobutyronitrile AIBN, azobisisoheptanitrile ABVN, dimethyl azobisisobutyrate AIBME, benzoyl peroxide BPO of one or more.
  • AIBN 2,2-azobisisobutyronitrile
  • ABVN azobisisoheptanitrile
  • ABVN dimethyl azobisisobutyrate
  • AIBME dimethyl azobisisobutyrate
  • benzoyl peroxide BPO of one or more.
  • the initiator preferably contains or consists of AIBN and BPO.
  • the initiator is a combination of 2,2-azobisisobutyronitrile AIBN and benzoyl peroxide BPO in a mass ratio of (0.01-4):(0.01-4).
  • the mass ratio of AIBN and BPO as initiators is 2:1-5:1, such as 3:1-4:1.
  • the initiator AIBN content in the semi-solid electrolyte is 0.1-0.5wt.%, such as 0.15-0.2wt.%, and the BPO content is 0.03-0.1wt.%, such as 0.04-0.06wt.%.
  • the AIBN content in the semi-solid electrolyte is 0.18wt.% and the BPO content is 0.05wt.%.
  • the polymerization reaction rate initiated by AIBN is higher and the reaction is more violent, while the polymerization reaction initiated by BRO is relatively mild.
  • the combination of the two can effectively control the polymerization reaction rate. On the one hand, it ensures the effective infiltration of the electrolyte before polymerization, and on the other hand, it ensures that the polymerization reaction does not occur. It will be too violent and destroy the microstructure and morphology of the pole piece. If a high content of BPO and a very small amount of AIBN are used, the reaction rate will be too slow and the high temperature time required will be too long. Under continuous high temperature conditions, the pole pieces, materials and electrolytes will have undesirable decomposition side reactions.
  • the semi-solid electrolyte has a polymerized monomer content of 20-40 wt.%, a plasticizer content of 0.1-5 wt.%, and an initiator content of 0.02-8 wt.%.
  • the polymerized monomer content in the semi-solid electrolyte is 20-36.5wt.%, such as 20-30wt.%, 25wt.%, 27wt.%, 29wt.%.
  • the plasticizer content in the semi-solid electrolyte is 0.5-5wt.%, such as 1wt.%, 1.2wt.%, 1.5wt.%, 2wt.%, 2.5wt.%, 3wt.%.
  • the initiator content in the semi-solid electrolyte is 0.1-1wt.%, such as 0.2wt.%, 0.23wt.%, 0.25wt.%, 0.3wt.%, 0.5wt.%.
  • the negative electrode is a silicon-doped graphite negative electrode, a lithium metal negative electrode or a metal alloy negative electrode.
  • the main material of the positive electrode is nickel material, nickel manganese aluminum material NCA, lithium iron manganese phosphate LMFP or lithium iron phosphate LiFePO4.
  • the amount of silicon doped in the silicon-doped graphite negative electrode is 3%-80%, preferably 5-60%, such as 5-30%, and further preferably 8-30%.
  • Metal alloy negative electrodes suitable for use in the present invention include Ga-Sn, Ge-Se or Sn-Al negative electrodes.
  • the nickel material includes one or more selected from NCM811, Ni90, NCM111, NCM532, NCM622, and NCM712.
  • both the positive and negative electrodes contain conductive agents.
  • the conductive agent suitable for the present invention includes one or more selected from carbon black super P, acetylene black, and carbon nanotubes.
  • the carbon nanotubes may be selected from one or more of multi-walled carbon nanotubes MWCNT and single-walled carbon nanotubes SWCNT.
  • both the positive and negative electrodes contain a binder.
  • the binder may be selected from polyethylene oxide PEO, polyvinylidene fluoride PVDF, sodium carboxymethyl cellulose CMC-Na, polyurethane PU, styrene-butadiene rubber SBR, polyvinyl alcohol PVA, polyacrylic acid PAA, polyacrylonitrile One or more of PAN.
  • the temperature of the in-situ polymerization is 58-65°C, and the time of the in-situ polymerization is 1.25-3h.
  • Some additives in the electrolyte will be unstable under sustained high temperatures for a long time, and can easily cause undesirable decomposition side reactions with the pole piece materials. Therefore, it is necessary to control the temperature not to be too high and the time not to be too long.
  • the present invention also provides a method for preparing the free radical in-situ polymerization semi-solid battery according to any embodiment herein, the method comprising the following steps:
  • liquid electrolyte is polymerized in situ to form the semi-solid electrolyte.
  • step (2) the battery is aged before in-situ polymerization, and the battery can be formed, aged, and divided after in-situ polymerization.
  • the present invention has the following beneficial effects:
  • the present invention obtains lower battery impedance and improves battery performance by improving the gel electrolyte (semi-solid electrolyte) components; when the polymerized monomer is preferably a combination of vinylene carbonate and trimethylene carbonate, adjustments and improvements can be made
  • the hardness of the gel electrolyte allows the gel electrolyte to be in a viscous flow state in the pores between the pole piece particles and between the pole piece and the separator, which not only enables the effective transmission of lithium ions but also makes the pole piece particles contact and adhere, which is beneficial to the battery. Effective contact and ion transport at the solid-solid interface;
  • the present invention improves the safety of the battery through the optimization of components; for example, the use of plasticizer succinonitrile, etc., is beneficial to improving the flexibility of the gel electrolyte and helping to improve the safety of the battery;
  • the initiator in the present invention is preferably a combination of 2,2-azobisisobutyronitrile and a small amount of benzoyl peroxide; the reaction speed of 2,2-azobisisobutyronitrile is too fast, and benzoyl peroxide
  • the polymerization reaction is milder, so a specific combination of the two is used to cooperate with the battery production process to perform a gentle in-situ polymerization reaction, which is more conducive to the formation of in-situ gel electrolyte;
  • the present invention improves the battery production process.
  • the in-situ polymerization of the present invention has lower temperature and faster polymerization, which can effectively improve efficiency and reduce production costs; and the production, in-situ polymerization and Gelization is more suitable for actual battery production lines, which can better improve efficiency and reduce costs.
  • Figure 1 is a schematic diagram of the semi-solid battery production process
  • Figure 2 is an inverted view of the semi-solid electrolyte of Example 3;
  • Figure 3 is an impedance diagram of the conductivity test of the semi-solid electrolyte in Example 3;
  • Figure 4 shows the test results of the lithium ion migration number of the semi-solid electrolyte in Example 3, (a) the lithium symmetric impedance spectrum of the initial state and the stable state, (b) the polarization current diagram under the chronoamperometry;
  • Figure 5 is a room temperature impedance diagram of the semi-solid state battery of Examples 1-7.
  • the main material of the negative electrode layer is preferably silicon-doped graphite, lithium metal or a metal alloy.
  • Silicon-doped graphite includes silicon-containing materials as well as graphite.
  • the silicon-containing material includes one or more selected from silicon-oxygen materials and silicon-carbon materials.
  • the silicon-doped content of the silicon-doped graphite can be 3%-80%, preferably 5-60%, such as 5-30% , further preferably 8-30%.
  • Available metal alloys include Ga-Sn alloys, Ge-Se alloys, Sn-Al alloys, etc.
  • the main material of the positive electrode layer is preferably a high-nickel material (i.e., LiNix Co y Mn z O 2 , where x ⁇ 0.8, such as NCM811 and Ni90 materials), and may also be NCM111, NCM532, or NCM622 , NCM712, nickel manganese aluminum material NCA, lithium iron manganese phosphate LMFP or lithium iron phosphate LiFePO4.
  • a high-nickel material i.e., LiNix Co y Mn z O 2 , where x ⁇ 0.8, such as NCM811 and Ni90 materials
  • the conductive agent suitable for the present invention can be one or more selected from carbon black super P, acetylene black, multi-walled carbon nanotubes MWCNT, and single-walled carbon nanotubes SWCNT.
  • the positive and negative electrode sheets also contain binders.
  • the binder suitable for the present invention can be selected from PEO (polyethylene oxide), PVDF (polyvinylidene fluoride), CMC-Na (sodium carboxymethylcellulose), PU (polyurethane), SBR (styrene-butadiene rubber) , one or more of PVA (polyvinyl alcohol), PAA (polyacrylic acid), PAN (polyacrylonitrile).
  • the contents of active materials, conductive agents and binders in the positive and negative electrodes may be conventional.
  • the semi-solid electrolyte is formed by adding polymerized monomers, plasticizers and initiators to the liquid electrolyte through polymerization.
  • the liquid electrolyte suitable for the present invention can be a conventional lithium battery liquid electrolyte.
  • the liquid electrolyte contains lithium salts.
  • Available lithium salts include those selected from the group consisting of lithium hexafluorophosphate LiPF6, lithium difluorophosphate LiPO2F2, lithium bisfluorosulfonimide LiFSI, lithium bistrifluoromethanesulfonimide LiTFSI, lithium trifluoromethanesulfonate LiCF3SO3, and lithium tetrafluoroborate LiBF4 , one or more of lithium bisoxaloborate LiBOB, lithium difluoroborate borate LiODFB, and lithium difluorobisoxalate phosphate LiDFBP.
  • the concentration of lithium salt in the liquid electrolyte may be conventional, for example, 0.5-2 mol/L.
  • Liquid electrolytes also contain organic solvents.
  • the organic solvent may be a carbonate solvent.
  • Available carbonate solvents include, but are not limited to, selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate
  • the carbonate solvent contains at least one cyclic carbonate and at least one chain carbonate. Examples of cyclic carbonates include EC, PC and butylene carbonate.
  • chain carbonates examples include DMC, DEC and EMC.
  • the mass ratio of cyclic carbonate and chain carbonate may be 1:5 to 5:1. For example, 1:3, 1:2, 1:1.
  • the liquid electrolyte may also contain additives as needed, such as fluoroethylene carbonate (FEC), vinyl sulfate (DTD), etc.
  • FEC fluoroethylene carbonate
  • DTD vinyl sulfate
  • the amounts of additives may be conventional.
  • the polymerized monomer is a monomer with unsaturated double bonds or triple bonds, preferably a combination of VC (vinylene carbonate) and TMC (trimethylene carbonate).
  • the plasticizer may be selected from PEG (polyvinyl alcohol), PEGDME (polyethylene glycol dimethyl ether), DBP (dibutyl phthalate), DMP (dimethyl phthalate) , one or more of DOP (dioctyl phthalate), ACN (acetonitrile), SN (succinonitrile), TPU (thermoplastic polyurethane), preferably SN.
  • the initiator may be selected from AIBN (2,2-azobisisobutyronitrile), azobisisoheptanitrile (ABVN), dimethyl azobisisobutyrate (AIBME), BPO (benzoyl peroxide ), preferably a combination of AIBN and SN.
  • the polymerized monomer is a combination of vinylene carbonate VC and trimethylene carbonate TMC with a mass ratio of 20-35:0.1-1.5;
  • the initiator is 2,2-azobisisobutyronitrile
  • the combination of AIBN and benzoyl peroxide BPO; the polymer monomer VC content in the semi-solid electrolyte is 20-35wt.%, the TMC content is 0.1-1.5wt.%; the plasticizer content is 0.1-5wt.%, preferably 1.2-3wt.%; the initiator AIBN content is 0.01-4wt.%, and the BPO content is 0.01-4wt.%.
  • the AIBN content is 0.1-0.5wt.%, and the BPO content is 0.03-0.1wt.%.
  • the assembled battery when preparing the free radical in-situ polymerization semi-solid battery of the present invention, is injected with liquid, and then aged after the liquid injection.
  • the aging temperature is 20-50°C, preferably 45-48°C. °C, the aging time can be 12-36h, such as 24h.
  • the battery is then placed in a high-temperature environment to perform a gel reaction.
  • the high-temperature temperature is 50-70°C, preferably 58-65°C, and the reaction time is 0.5-24h, preferably 1.25-3h.
  • the battery is then subjected to formation, aging and capacity dividing processes to obtain the finished battery cell.
  • Examples 1 to 7 provide a series of free radical in-situ polymerization semi-solid batteries, including positive electrodes, negative electrodes and semi-solid electrolytes;
  • the process of preparing the battery is as follows:
  • the positive electrode slurry is applied to the aluminum foil, and the negative electrode slurry is applied to the copper foil, and then dried and rolled. Afterwards, rolling was performed, and the compacted density of the positive electrode was 3.48g ⁇ cm -3 and that of the negative electrode was 1.67g ⁇ cm -3 , and then slit. Afterwards, the pole core is wound, and the produced positive and negative electrode sheets and separators are used.
  • the separators are made of PE composite separators (3 ⁇ m PVDF adhesive layer + 9 ⁇ m PE base film + 3 ⁇ m Al 2 O 3 ceramic layer + 3 ⁇ m PVDF adhesive layer). The rolled pole core is hot-pressed, the top cover is welded, and then assembled into a shell to make a dry battery core.
  • the liquid is injected.
  • the battery After soaking, the battery undergoes formation, gelation and volume separation to obtain the finished battery core.
  • the preparation process is shown in Figure 1; the battery is assembled according to the normal battery production process; the assembled battery is injected (add the polymerized monomers, plasticizers and initiators shown in Table 1 to the liquid electrolyte) , perform aging after liquid injection, the aging temperature is 45°C, and aged for 24h; then the battery is placed in a high-temperature environment for gelation reaction, and the reaction is performed at 60°C for 2h, which triggers the gel polymerization of the electrolyte to form a semi-solid electrolyte; Then the battery is formed under high temperature and high pressure conditions (temperature is 40 ⁇ 5°C, pressure is controlled by a clamp, 2000N), aged at 45°C, and divided into volumes at room temperature to obtain the finished battery core.
  • high temperature and high pressure conditions temperature is 40 ⁇ 5°C, pressure is controlled by a clamp, 2000N
  • Comparative Examples 1 to 5 provide a series of free radical in-situ polymerization semi-solid batteries, which are basically the same as Example 1, except for the composition of the semi-solid electrolyte. See Table 1 for details.
  • ETPTA is trimethylolpropane triacrylate monomer.
  • Table 1 Components and amounts other than electrolyte in the semi-solid electrolyte of each example and comparative example
  • the dosage is wt.% relative to the total weight of the semi-solid electrolyte.
  • Figure 2 is a photograph of the synthesized semi-solid electrolyte (Example 3) in an inverted state, indicating that it is in a viscous solid state rather than a liquid state.
  • the test method of the impedance spectrum of the normal temperature conductivity test and the calculation method of the ionic conductivity are as follows: use the semi-solid electrolyte obtained in Example 3 to assemble a steel sheet symmetrical button cell for testing, in which Example 3 is filled between the steel sheets.
  • the semi-solid electrolyte in the battery is then connected to the electrochemical workstation, a disturbance voltage of 5mV is applied, the scanning frequency is from 100kHz to 1Hz, and the Nyquist spectrum (EIS impedance spectrum) of the battery is tested.
  • the lithium symmetry impedance diagram (EIS impedance spectrum) and the polarization current diagram under the chronoamperometry of the lithium ion migration number test of the semi-solid electrolyte prepared in Example 3 are shown in Figure 4.
  • the lithium ion migration number of the semi-solid electrolyte was calculated.
  • the ion migration number is approximately 0.512.
  • the test method of lithium symmetrical impedance diagram, polarization current diagram and the calculation method of lithium ion migration number are as follows: using the semi-solid electrolyte in Example 3 to assemble a lithium chip symmetric button battery for testing, in which the filling between lithium chips is carried out
  • the semi-solid electrolyte in Example 3 then connect the button battery to the electrochemical workstation, apply a disturbance voltage of 10mV, scan the frequency from 100kHz to 0.05Hz, test the Nyquist spectrum of the battery (the EIS impedance spectrum of the starting state), and read the Initial impedance value R 0 .
  • V is the applied voltage
  • R 0 is the starting impedance
  • R ss is the steady-state impedance
  • I 0 is the starting current value
  • I ss is the steady-state current value.
  • t Li + is the required lithium ion migration number.
  • the normal temperature impedance (EIS) diagram of the semi-solid state battery of Examples 1-7 is shown in Figure 5.
  • the test method for normal temperature impedance is as follows: connect the batteries of Examples 1 to 7 to an electrochemical workstation respectively, apply a disturbance current of 300 mA, scan the frequency from 200 kHz to 0.05 Hz, test the Nyquist spectrum of the battery, and read the impedance value. It can be seen from Figure 5 that the impedances of Examples 1-3 are low, and among them, the impedance of Example 3 is the lowest.
  • Table 2 shows the performance of the semi-solid electrolytes in Examples 1-7 and Comparative Examples 1-5 in full cells.
  • the impedance test method is: connect the battery to the electrochemical workstation, apply a disturbance voltage of 10mV, scan the frequency from 200kHz to 0.05Hz, test the Nyquist spectrum of the battery, and read the impedance value.
  • the method to determine the hardness is as follows: Make a semi-solid electrolyte sheet with a thickness of 1cm, use a glass rod to squeeze the semi-solid electrolyte sheet, and observe its extrusion state; if the semi-solid electrolyte is visually crystal-like and cannot be squeezed, it is judged to be hard; If the semi-solid electrolyte is visually elastomer-like and can be squeezed slightly, it is judged to be relatively hard; if the semi-solid electrolyte is visually inspected to be sticky and paste-like and can be squeezed to a large extent, it is judged to be slightly hard; if the semi-solid electrolyte is visually inspected it is If it is in a viscous fluid state and can easily extend the glass rod into the semi-solid electrolyte, it is judged as moderate; if the semi-solid electrolyte is always in a near-fluid state, it is judged as soft.
  • the battery hot box test method is: use the battery obtained in the example to conduct a hot box test according to the SAE-J2464 step temperature rise test method.
  • the higher the temperature that the battery can withstand the highest temperature platform at which the battery does not suffer from thermal runaway, fire, or explosion), the better the thermal stability of the battery.
  • Example 2 By comparing Example 2 and Comparative Example 1, it can be seen that when the amount of TMC in the semi-solid electrolyte is too high, the impedance of the battery is larger.
  • Example 2 By comparing Example 2 and Examples 4-6, it can be seen that using a combination of AIBN and BPO as an initiator in a semi-solid electrolyte is more beneficial to reducing the impedance of the battery than using AIBN, BPO or AIBME alone.
  • Example 2 By comparing Example 2 and Example 7, it can be seen that using SN as a plasticizer in a semi-solid electrolyte is more beneficial to reducing the impedance of the battery than DBP.
  • the present invention is not limited to lithium-ion batteries, but is also applicable to other types of electrochemical system batteries such as sodium-ion semi-solid batteries, potassium-ion semi-solid batteries, magnesium-ion semi-solid batteries, and aluminum-ion semi-solid batteries.
  • electrochemical system batteries such as sodium-ion semi-solid batteries, potassium-ion semi-solid batteries, magnesium-ion semi-solid batteries, and aluminum-ion semi-solid batteries.
  • positive and negative electrode materials and lithium salts with the corresponding sodium materials and sodium salts, or potassium materials and potassium salts, or magnesium materials and magnesium salts, or aluminum materials and aluminum salts.

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Abstract

本发明公开了一种自由基原位聚合半固态电池，包括正极、负极和半固态电解质；所述半固态电解质为液态电解液中添加聚合单体、增塑剂和引发剂原位聚合形成的半固态电解质；所述聚合单体为质量比20-35∶0.1-1.5的碳酸亚乙烯酯VC和三亚甲基碳酸酯TMC的组合。本发明通过改进凝胶电解质组分，降低电池阻抗，提升电池性能，改善凝胶电解质的硬度，有利于电池中的固固界面，提升电池的安全性。

Description

一种自由基原位聚合半固态电池 技术领域
本发明属于电池技术领域，涉及半固态电池技术领域，具体涉及一种自由基原位聚合半固态电池。
背景技术
随着人们对提高锂离子电池能量密度的日益迫切的要求，传统锂离子电池已经很难满足超高比能量的需求。当前商业化的锂电池负极材料主要为改性天然石墨和人造石墨，尽管制备技术已相当成熟，但石墨的理论比容量只有372mAh·g -1，难以满足市场对高能量密度锂离子电池的需求。于是，基于高能量密度电池的需求，具有超高比能量优势的负极材料成为研究热点。例如：硅负极、金属合金负极和金属锂负极。以硅负极材料为例，目前主要使用掺比一定量的硅材料以达到提升比容量的目的。以金属锂负极为例，其比容量为3860mAh·g -1，电化学势为-3.04V(vs.标准氢电极)。以这些负极材料制作的电池可以有效提升能量密度，甚至可以达到400Wh kg -1以上甚至更高。而中、高镍三元锂电池因其活性较高，搭配高比容量负极材料后，在提高比能量密度的同时，对于电池安全性的提升也是重中之重。
然而，基于传统锂离子电池体系，高能量密度电池材料目前仍有很多安全隐患。材料本身较大的体积膨胀，结构的改变，和与液态电解液搭配时的循环寿命与安全性隐患。液态电解液无法有效抑制硅负极的巨大膨胀，或锂金属负极结构的变化和金属枝晶的生长，且枝晶可能刺穿隔膜而引发电池内部的短路，引发更大的安全问题。
目前已经出现了比较多的凝胶半固态电池技术。半固态电池可以有效降低电池中液态电解液的使用量，在提升电池的能量密度的同时，也将液态电解液可能引发的安全隐患同步降低。另外，半固态凝胶电解质在一定程度上可以有效抑制负极结构的改变和金属枝晶的生长，在提升比能量的同时可以较大程度地提高电池的安全性。然而，现有半固态凝胶电解质往往存在聚合后电池阻抗较高，性能损失较大等不足。
对现有专利文献检索发现，CN 112018438 A应用了碳酸亚乙烯酯作为凝胶聚合单体，偶氮二异丁腈作为引发剂，并配合丙烯酸酯类的柔性剂及交联剂，引发原位聚合。但是其成分组合和含量同样会导致聚合后电池阻抗较高，性能损失较大。
发明内容
基于上述问题，本发明的目的在于提供一种自由基原位聚合半固态电池；本发明使用原位聚合方法制作及生产半固态电池，具体是使用聚合单体、增塑剂及引发剂等组分，在一定条件下形成半固态电解质。
本发明的目的是通过下述技术方案予以实现：
本发明提供一种自由基原位聚合半固态电池，包括正极、负极和半固态电解质，所述半固态电解质为液态电解液中添加聚合单体、增塑剂和引发剂原位聚合形成的半固态电解质；所述聚合单体为质量比20-35∶0.1-1.5的碳酸亚乙烯酯VC和三亚甲基碳酸酯TMC的组合。
液态电解液含有锂盐。所述锂盐可以是选自六氟磷酸锂LiPF6、二氟磷酸锂LiPO2F2、双氟磺酰亚胺锂LiFSI、双三氟甲磺酰亚胺锂LiTFSI、三氟甲基磺酸锂LiCF3SO3、四氟硼酸锂LiBF4、双草酸硼酸锂LiBOB、二氟草酸硼酸锂LiODFB、二氟双草酸磷酸锂LiDFBP中的一种或多种。
本发明中，所述聚合单体优选为质量比20-35∶0.1-1.5的碳酸亚乙烯酯VC和三亚甲基碳酸酯TMC的组合。优选半固态电解质中聚合单体VC和TMC的总含量为20-36.5wt.％、例如20-30wt.％、25wt.％、27wt.％、29wt.％。优选半固态电解质中聚合单体VC含量为20-35wt.％、例如20-29wt.％、25wt.％、27wt.％、28wt.％，TMC含量为0.1-1.5wt.％、例如0.5-1wt.％、0.7wt.％、0.9wt.％。在本发明的体系中，VC为主要聚合单体，TMC为辅助聚合单体，二者缺一不可。TMC聚合后的主要作用为增加聚合后的VC基半固态电解质的粘性。如果以TMC为主要聚合单体，VC为辅，其半固态电解质性质不稳定，无法有效形成半固态电解质。
在一些实施方案中，所述增塑剂选自聚乙烯醇PEG、聚乙二醇二甲醚PEGDME、邻苯二甲酸二丁酯DBP、邻苯二甲酸二甲酯DMP、邻苯二甲酸二辛酯DOP、乙腈ACN、丁二腈SN、热塑性聚氨酯TPU中的一种或多种。增塑剂优选为丁二腈SN。丁二腈SN结构较稳定，其具有良好的离子导电性，较好的热稳定性和较高的氧化稳定性，在半固态电解质中使用，有助于增加半固态电解质在高温和高电压下的稳定性，且其对阻抗和性能的负面影响较小。
在一些实施方案中，所述引发剂选自2，2-偶氮二异丁腈AIBN、偶氮二异庚腈ABVN、偶氮二异丁酸二甲酯AIBME、过氧化苯甲酰BPO中的一种或多种。引发剂优选包含AIBN和BPO，或由AIBN和BPO组成。
在一些优选的实施方案中，所述引发剂为质量比(0.01-4)∶(0.01-4)的2，2-偶氮二异丁腈AIBN和过氧化苯甲酰BPO的组合。在一些实施方案中，作为引发剂的AIBN和BPO的质量比为2∶1-5∶1，例如3∶1-4∶1。优选半固态电解质中引发剂AIBN含量为0.1-0.5wt.％、例如0.15-0.2wt.％，BPO含量为0.03-0.1wt.％、例如0.04-0.06wt.％。最优选半固态电解质中AIBN含量为0.18wt.％，BPO含量为0.05wt.％。AIBN引发的聚合反应速率较高，反应较剧烈，而BRO 引发的聚合反应相对温和；二者组合可以有效的控制聚合反应速率，一方面保证聚合前电解液的有效浸润，一方面保证聚合反应不会过于剧烈而破坏极片的微观结构和形貌。如果使用高含量BPO和极少量AIBN，则反应速率过慢，需要的高温时间过长，极片、材料以及电解液在持续的高温情况下，会有不理想的分解副反应。
在一些实施方案中，所述半固态电解质中聚合单体含量为20-40wt.％，增塑剂含量为0.1-5wt.％，引发剂含量为0.02-8wt.％。优选半固态电解质中聚合单体含量为20-36.5wt.％、例如20-30wt.％、25wt.％、27wt.％、29wt.％。优选半固态电解质中增塑剂含量为0.5-5wt.％，例如1wt.％、1.2wt.％、1.5wt.％、2wt.％、2.5wt.％、3wt.％。优选半固态电解质中引发剂含量为0.1-1wt.％，例如0.2wt.％、0.23wt.％、0.25wt.％、0.3wt.％、0.5wt.％。
在一些优选的实施方案中，所述负极为掺硅石墨负极、锂金属负极或金属合金负极。
在一些实施方案中，所述正极的主材(即活性材料)为镍材料、镍锰铝材料NCA、磷酸锰铁锂LMFP或磷酸亚铁锂LiFePO4。
在一些实施方案中，所述掺硅石墨负极中掺硅量为3％-80％，优选为5-60％，例如5-30％，进一步优选为8-30％。
适用于本发明的金属合金负极包括Ga-Sn、Ge-Se或Sn-Al负极。
在一些实施方案中，所述镍材料包括选自NCM811、Ni90、NCM111、NCM532、NCM622、NCM712中的一种或多种。
在一些实施方案中，所述正、负极均含有导电剂。适用于本发明的导电剂包括选自炭黑super P、乙炔黑、碳纳米管中的一种或多种。碳纳米管可以选自多壁碳纳米管MWCNT、单壁碳纳米管SWCNT中的一种或多种。
在一些实施方案中，所述正、负极均含有粘结剂。所述粘结剂可以为选自聚氧化乙烯PEO、聚偏氟乙烯PVDF、羧甲基纤维素钠CMC-Na、聚氨酯PU、丁苯橡胶SBR、聚乙烯醇PVA、聚丙烯酸PAA、聚丙烯腈PAN中的一种或多种。
在一些优选的实施方案中，所述原位聚合的温度为58-65℃，原位聚合的时间为1.25-3h。电解液中一些添加剂在持续的长时间高温下会不稳定，容易与极片材料引发不理想的分解副反应。因此需要控制温度不能过高，且时间不能过长。
本发明还提供制备本文任一实施方案所述的自由基原位聚合半固态电池的方法，所述方法包括以下步骤：
(1)向电芯中注入液态电解液，所述液态电解液中添加有所述聚合单体、增塑剂和引发剂；
(2)使所述液态电解液发生原位聚合形成所述半固态电解质。
在一些实施方案中，步骤(2)中，在原位聚合前先对电池进行陈化，在原位聚合后可以对电池进行化成、老化和分容。
与现有技术相比，本发明具有如下有益效果：
1)本发明通过改进凝胶电解质(半固态电解质)组分，获得较低的电池阻抗，提升电池性能；当聚合单体优选碳酸亚乙烯酯与三亚甲基碳酸酯的组合时，可以调整改善凝胶电解质的硬度，使凝胶电解质以粘流态处于极片颗粒之间的孔隙中和极片与隔膜之间，既使锂离子有效传输又使极片颗粒接触黏合，有利于电池中的固固界面的有效接触和离子传输；
2)本发明通过组分的优化，提升电池的安全性；如使用了增塑剂丁二腈等，有利于提升凝胶电解质的柔韧度，并有助于提升电池安全性；
3)本发明中引发剂优选2，2-偶氮二异丁腈与少量过氧化苯甲酰的组合；2，2-偶氮二异丁腈的反应速度过快，而过氧化苯甲酰的聚合反应更温和，因此二者采用特定的组合配合电池的生产流程进行平缓的原位聚合反应，更有助于原位凝胶电解质的形成；
4)本发明改进了电池生产工艺，本发明的原位聚合具有较低的温度和较快的聚合，可以有效提升效率，降低生产成本；并且是在实际的电池中进行生产、原位聚合以及凝胶化，更适用于实际的电池生产产线，能更好地提高效率，降低成本。
附图说明
通过阅读参照以下附图对非限制性实施例所作的详细描述，本发明的其它特征、目的和优点将会变得更明显：
图1为半固态电池生产流程示意图；
图2为实施例3半固态电解质的倒置图；
图3为实施例3半固态电解质电导率测试阻抗图；
图4为实施例3半固态电解质的锂离子迁移数测试结果，(a)起始态与稳定态的锂对称阻抗谱图，(b)计时电流法下的极化电流图；
图5为实施例1-7半固态电池的常温阻抗图。
具体实施方式
下面结合实施例对本发明进行详细说明。以下实施例将有助于本领域的技术人员进一步理解本发明，但不以任何形式限制本发明。应当指出的是，对本领域的普通技术人员来说，在不脱离本发明构思的前提下，还可以做出若干调整和改进。这些都属于本发明的保护范围。
本发明的自由基原位聚合半固态电池中，负极层主材(即负极活性材料)优选为掺硅石墨、锂金属或金属合金。掺硅石墨包括含硅的材料以及石墨。含硅的材料包括选自硅氧材料和硅碳材料中的一种或多种。使用掺硅石墨作为负极活性物质时，掺硅石墨的掺硅量(含硅 的材料占掺硅石墨的质量分数)可以为3％-80％，优选为5-60％，例如5-30％，进一步优选为8-30％。可用的金属合金包括Ga-Sn合金、Ge-Se合金、Sn-Al合金等。
本发明中，正极层主材(即正极活性材料)优选为高镍材料(即LiNi xCo yMn zO 2，其中x≥0.8，例如NCM811和Ni90材料)，也可以是NCM111、NCM532、NCM622、NCM712、镍锰铝材料NCA、磷酸锰铁锂LMFP或磷酸亚铁锂LiFePO4。
正、负极极片中均需要混合导电剂。适用于本发明的导电剂可以为选自炭黑super P、乙炔黑、多壁碳纳米管MWCNT，单壁碳纳米管SWCNT中的一种或多种。正、负极片还含有粘结剂。适用于本发明的粘结剂可以为选自PEO(聚氧化乙烯)、PVDF(聚偏氟乙烯)、CMC-Na(羧甲基纤维素钠)、PU(聚氨酯)、SBR(丁苯橡胶)、PVA(聚乙烯醇)、PAA(聚丙烯酸)、PAN(聚丙烯腈)中的一种或多种。
本发明中，正、负极中活性材料、导电剂和粘结剂的含量可以是常规的。
本发明中，半固态电解质通过在液态电解液中添加聚合单体、增塑剂和引发剂经过聚合而形成。
适用于本发明的液态电解液可以为常规的锂电池液态电解液。液态电解液含有锂盐。可用的锂盐包括选自六氟磷酸锂LiPF6、二氟磷酸锂LiPO2F2、双氟磺酰亚胺锂LiFSI，双三氟甲磺酰亚胺锂LiTFSI，三氟甲基磺酸锂LiCF3SO3，四氟硼酸锂LiBF4，双草酸硼酸锂LiBOB，二氟草酸硼酸锂LiODFB，二氟双草酸磷酸锂LiDFBP中的一种或多种。液态电解液中锂盐的浓度可以是常规的，例如可以为0.5-2mol/L。液态电解液还含有有机溶剂。有机溶剂可以是碳酸酯类溶剂。可用的碳酸酯类溶剂包括但不限于选自碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸丁烯酯、碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)中的一种或多种，优选两种或两种以上。优选地，碳酸酯类溶剂包含至少一种环状碳酸酯和至少一种链状碳酸酯。环状碳酸酯的实例包括EC、PC和碳酸丁烯酯。链状碳酸酯的实例包括DMC、DEC和EMC。环状碳酸酯和链状碳酸酯的质量比可以为1∶5到5∶1。例如1∶3、1∶2、1∶1。液态电解液根据需要还可以包含添加剂，例如氟代碳酸乙烯酯(FEC)、硫酸乙烯酯(DTD)等。添加剂的用量可以是常规的。
本发明中，聚合单体为带有不饱和双键或三键的单体，优选是VC(碳酸亚乙烯酯)和TMC(三亚甲基碳酸酯)的组合。
本发明中，增塑剂可以是选自PEG(聚乙烯醇)、PEGDME(聚乙二醇二甲醚)、DBP(邻苯二甲酸二丁酯)、DMP(邻苯二甲酸二甲酯)、DOP(邻苯二甲酸二辛酯)、ACN(乙腈)、SN(丁二腈)、TPU(热塑性聚氨酯)中的一种或多种，优选为SN。引发剂可以是选自AIBN(2，2-偶氮二异丁腈)、偶氮二异庚腈(ABVN)、偶氮二异丁酸二甲酯(AIBME)、BPO(过氧化苯甲酰) 中的一种或多种，优选为AIBN和SN的组合。
在一些优选的实施方案中，聚合单体为质量比20-35∶0.1-1.5的碳酸亚乙烯酯VC和三亚甲基碳酸酯TMC的组合；引发剂为2，2-偶氮二异丁腈AIBN和过氧化苯甲酰BPO的组合；半固态电解质中聚合单体VC含量为20-35wt.％，TMC含量为0.1-1.5wt.％；增塑剂含量为0.1-5wt.％，优选为1.2-3wt.％；引发剂AIBN含量为0.01-4wt.％，BPO含量为0.01-4wt.％，优选为AIBN含量为0.1-0.5wt.％，BPO含量为0.03-0.1wt.％。
在一些实施方案中，制备本发明的自由基原位聚合半固态电池时，对装配后的电池进行注液，注液后进行陈化，陈化温度为20-50℃，优选为45-48℃，陈化时间可以为12-36h、例如24h。然后将电池放入高温环境中进行凝胶反应，高温温度为50-70℃，优选为58-65℃，反应时间为0.5-24h，优选为1.25-3h。然后对电池进行化成、老化以及分容工序，获得成品电芯。
下文将以具体实施例的方式阐述本发明。应理解，这些实施例仅仅是阐述性的，并非意图限制本发明的范围。实施例中所用到的方法、试剂和材料，除非另有说明，否则为本领域常规的方法、试剂和材料。实施例中的原材料均可通过市售途径购得。
实施例1～7
实施例1～7提供了一系列自由基原位聚合半固态电池，包括正极、负极和半固态电解质；
制备电池的过程如下：
首先混合浆料，其中，正极浆料干物质的质量配比为，9系三元材料(NCM-Ni90，LiNi 0.9Co 0.05Mn 0.05O 2)∶导电炭黑(Super P)∶碳纳米管(CNT800)∶粘结剂(聚偏氟乙烯PVDF_1100)＝97∶1.1∶0.8∶1.1，溶剂为N-甲基吡咯烷酮(NMP)；
负极浆料干物质的质量配比为，石墨(BF)∶硅氧材料(氧化亚硅SiO)∶导电炭黑(Super P)∶碳纳米管(CNT800)∶粘结剂(聚丙烯酸PAA)∶粘结剂(丁苯橡胶SBR)＝88.1∶6.5∶1.8∶0.2∶1.2∶2.2，溶剂为去离子水；
然后进行涂布，将正极浆料涂到铝箔上，负极浆料涂到铜箔上，进行烘干收卷。之后进行辊压，正极压实密度为3.48g·cm -3，负极压实密度为1.67g·cm -3，然后进行分切。之后进行极芯卷绕，使用制作的正、负极片和隔膜，隔膜采用PE复合隔膜(3μm PVDF胶层+9μmPE基膜+3μm Al 2O 3陶瓷层+3μm PVDF胶层)。将卷绕后的极芯热压后对顶盖进行焊接，然后装配入壳制成干电芯。
干电芯烘烤后进行注液。
半固态电解质中电解液各组分的质量配比为，碳酸乙烯酯(EC)∶碳酸甲乙酯 (EMC)∶碳酸二乙酯(DEC)∶LiPF 6∶LiFSI∶LiPO 2F 2∶氟代碳酸乙烯酯(FEC)∶硫酸乙烯酯(DTD)＝22∶28.2∶20∶12∶12∶0.5∶4.5∶0.8，各实施例保持不变；半固态电解质中其他组分和用量分别如表1所示。
浸润之后的电池，进行化成、凝胶工序和分容，得到成品电芯。
制备流程如图1所示；按正常的电池生产流程进行电池的装配；对装配后的电池进行注液(在液态电解液中添加表1所示的聚合单体、增塑剂和引发剂)，注液后进行陈化，陈化温度为45℃，陈化24h；然后将电池放入高温环境中进行凝胶反应，在60℃反应2h，引发电解液的凝胶聚合形成半固态电解质；然后电池在高温高压条件下(温度为40±5℃，压力通过夹具控制，为2000N)化成，在45℃条件下老化，室温条件下进行分容，得到成品电芯。
对比例1～5
对比例1～5提供了一系列自由基原位聚合半固态电池，基本同实施例1，所不同之处在于：半固态电解质的组成。详见表1。表1中，ETPTA为三羟甲基丙烷三丙烯酸酯单体。
表1：各实施例和对比例的半固态电解质中除电解液以外的组分和用量
Figure PCTCN2022134971-appb-000001
注：用量是相对于半固态电解质总重的含量wt.％。
图2为合成的半固态电解质(实施例3)倒置状态下的照片，说明其为粘固态而非液态。
实施例3制得的半固态电解质的常温电导率测试的阻抗谱图如图3所示，计算得出其常温下离子电导率约为2-3mS/cm。
常温电导率测试的阻抗谱图的测试方法和离子电导率的计算方法为：使用实施例3得到的半固态电解质组装钢片对称纽扣电池进行测试，其中钢片与钢片之间填充实施例3中的半 固态电解质，然后将纽扣电池连接电化学工作站，施加5mV的扰动电压，扫描频率从100kHz至1Hz，测试电池的Nyquist谱图(EIS阻抗图谱)。测试半固态电解质的厚度和面积，通过Nyquist曲线与X轴的交点阻抗计算半固态电解质的离子电导率。
实施例3制得的半固态电解质的锂离子迁移数测试的锂对称阻抗图(EIS阻抗图谱)及计时电流法下的极化电流图如图4所示，计算得出该半固态电解质的锂离子迁移数约为0.512。
锂对称阻抗图、极化电流图的测试方法和锂离子迁移数的计算方法为：使用实施例3中的半固态电解质组装锂片对称纽扣电池进行测试，其中锂片与锂片之间填充实施例3中的半固态电解质，然后将纽扣电池连接电化学工作站，施加10mV的扰动电压，扫描频率从100kHz至0.05Hz，测试电池的Nyquist谱图(起始态的EIS阻抗图谱)，读取其初始阻抗值R 0。之后采用计时电流法，同样施加10mV的电压测试初始电流I 0，之后进行持续极化至电流稳定(约18000s后)，获得极化电流图，读取其稳态电流值I ss，并采用同样的方法测试其极化后的Nyquist谱图(稳定态的EIS阻抗图谱)，读取其稳态阻抗值R ss。采用如下公式进行锂离子迁移数计算：
Figure PCTCN2022134971-appb-000002
其中：V为所施加电压，R 0为起始阻抗，R ss为稳态阻抗，I 0为起始电流值，I ss为稳态电流值。t Li +为所求锂离子迁移数。
实施例1-7的半固态电池的常温阻抗(EIS)图如图5所示。常温阻抗的测试方法为：将实施例1-7的电池分别连接电化学工作站，施加300mA的扰动电流，扫描频率从200kHz至0.05Hz，测试电池的Nyquist谱图，读取阻抗数值。由图5可知，实施例1-3的阻抗低，且其中实施例3的阻抗最低。
表2示出了实施例1-7和对比例1-5中的半固态电解质在全电池中的性能。其中，阻抗的测试方法为：将电池连接电化学工作站，施加10mV的扰动电压，扫描频率从200kHz至0.05Hz，测试电池的Nyquist谱图，读取阻抗数值。
硬度的判定方法为：制作1cm厚度的半固态电解质薄片，使用玻璃棒对半固态电解质薄片进行挤压，观测其挤压状态；半固态电解质目测呈晶体状并且无法挤压，则判定为硬；半固态电解质目测呈弹性体状并且可以轻微被挤压，则判定为较硬；半固态电解质目测呈粘膏体状并且可以较大程度被挤压，则判定为稍硬；半固态电解质目测呈粘流态并且可以轻易将玻璃棒伸入半固态电解质中，则判定为适中；半固态电解质始终呈近流体态，则判定为较软。
电池热箱测试方法为：使用实施例所获得的电池按照SAE-J2464阶梯升温测试法进行热箱测试。电池可以承受的温度越高(电池不发生热失控、着火、爆炸所对应的最高温度平台)， 则代表电池的热稳定性越好。
表2：各实施例和对比例的半固态电解质在全电池中的性能对比
Figure PCTCN2022134971-appb-000003
通过比较实施例2和对比例1可知，当半固态电解质中TMC的用量过高时，电池的阻抗较大。
由对比例2可知，不向半固态电解质中添加增塑剂会使得电池的阻抗较大。
由对比例3和4(均和实施例2对比)可知，当半固态电解质只使用碳酸亚乙烯酯单体或三亚甲基碳酸酯单体其中之一时，电池的阻抗较大。
由对比例5可知，当半固态电解质使用碳酸亚乙烯酯和三羟甲基丙烷三丙烯酸酯这两种单体时，电池的阻抗较大。
通过比较实施例2和实施例4-6可知，在半固态电解质中使用AIBN和BPO的组合作为引发剂相比单独使用AIBN、BPO或AIBME有利于降低电池的阻抗。
通过比较实施例2和实施例7可知，在半固态电解质中使用SN作为增塑剂相比DBP有利于降低电池的阻抗。
需要特别说明的是：本发明不止局限于锂离子电池，同样适用于制作钠离子半固态电池、钾离子半固态电池、镁离子半固态电池、铝离子半固态电池的其他种类电化学体系电池，只需将正、负极材料和锂盐更换为相应的钠材料和钠盐，或钾材料和钾盐，或镁材料和镁盐，或铝材料和铝盐。
以上对本发明的具体实施例进行了描述。需要理解的是，本发明并不局限于上述特定实施方式，本领域技术人员可以在权利要求的范围内做出各种变形或修改，这并不影响本发明的实质内容。

Claims (13)

  1. 一种自由基原位聚合半固态电池，包括正极、负极和半固态电解质，其特征在于，所述半固态电解质为液态电解液中添加聚合单体、增塑剂和引发剂原位聚合形成的半固态电解质；所述聚合单体为质量比20-35∶0.1-1.5的碳酸亚乙烯酯和三亚甲基碳酸酯的组合。
  2. 根据权利要求1所述的自由基原位聚合半固态电池，其特征在于，所述液态电解液含有锂盐；所述锂盐选自六氟磷酸锂、二氟磷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲基磺酸锂、四氟硼酸锂、双草酸硼酸锂、二氟草酸硼酸锂、二氟双草酸磷酸锂中的一种或多种。
  3. 根据权利要求1所述的自由基原位聚合半固态电池，其特征在于，所述增塑剂选自聚乙烯醇、聚乙二醇二甲醚、邻苯二甲酸二丁酯、邻苯二甲酸二甲酯、邻苯二甲酸二辛酯、乙腈、丁二腈、热塑性聚氨酯中的一种或多种。
  4. 根据权利要求1所述的自由基原位聚合半固态电池，其特征在于，所述增塑剂为丁二腈。
  5. 根据权利要求1所述的自由基原位聚合半固态电池，其特征在于，所述引发剂选自2，2-偶氮二异丁腈、偶氮二异庚腈、偶氮二异丁酸二甲酯、过氧化苯甲酰中的一种或多种。
  6. 根据权利要求4所述的自由基原位聚合半固态电池，其特征在于，所述引发剂为质量比0.01-4∶0.01-4的2，2-偶氮二异丁腈和过氧化苯甲酰的组合。
  7. 根据权利要求1所述的自由基原位聚合半固态电池，其特征在于，所述半固态电解质中聚合单体含量为20-40wt.％，增塑剂含量为0.1-5wt.％，引发剂含量为0.02-8wt.％。
  8. 根据权利要求1所述的自由基原位聚合半固态电池，其特征在于，所述半固态电解质中聚合单体含量为20-36.5wt.％。
  9. 根据权利要求1所述的自由基原位聚合半固态电池，其特征在于，所述负极为掺硅石墨负极、锂金属负极或金属合金负极，所述正极的活性材料为镍材料、镍锰铝材料、磷酸锰铁锂或磷酸亚铁锂。
  10. 根据权利要求9所述的自由基原位聚合半固态电池，其特征在于，所述镍材料包括选自NCM811、Ni90、NCM111、NCM532、NCM622、NCM712中的一种或多种。
  11. 根据权利要求1所述的自由基原位聚合半固态电池，其特征在于，所述正、负极均含有导电剂和粘结剂；所述导电剂包括选自炭黑、乙炔黑、碳纳米管中的一种或多种；所述粘结剂选自聚氧化乙烯、聚偏氟乙烯、羧甲基纤维素钠、聚氨酯、丁苯橡胶、聚乙烯醇、聚 丙烯酸、聚丙烯腈中的一种或多种。
  12. 根据权利要求1所述的自由基原位聚合半固态电池，其特征在于，所述原位聚合的温度为58-65℃，原位聚合的时间为1.25-3h。
  13. 制备权利要求1-12中任一项所述的自由基原位聚合半固态电池的方法，其特征在于，所述方法包括以下步骤：
    (1)向电芯中注入液态电解液，所述液态电解液中添加有所述聚合单体、增塑剂和引发剂；
    (2)使所述液态电解液发生原位聚合形成所述半固态电解质。
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