In-situ cross-linked polymer solid electrolyte, preparation method and application thereof

Abstract

The application discloses a preparation and application of an in-situ crosslinking polymer solid electrolyte, and belongs to the technical field of lithium battery materials.A novel flame-retardant solid polymer electrolyte is provided, in which a flame-retardant crosslinking component can be crosslinked and polymerized together with electrolyte monomers to form a three-dimensional polymer crosslinking network, which can promote the rapid transmission of lithium ions together, and can significantly improve the thermal stability and flame retardancy of the electrolyte, and can greatly improve the thermal safety performance and cycle stability of the secondary battery, and the process is simple and has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of lithium battery materials, and specifically relates to the preparation and application of an in-situ cross-linked polymerized solid electrolyte with high thermal stability. Background Art

[0002] Secondary lithium batteries have already occupied a vital position in various electronic and electrical fields. Building large-scale energy storage facilities composed of lithium batteries can improve the efficient storage and reuse of energy. However, the electrolytes currently used in lithium batteries include liquid electrolytes, gel electrolytes (i.e., quasi-solid electrolytes), and solid electrolytes.

[0003] Among them, 1) Liquid electrolyte: The electrolyte as a whole has good fluidity and is easy to volatilize and burn. 2) Gel electrolyte (i.e., quasi-solid electrolyte): The liquid electrolyte is bound in the polymer skeleton, has poor fluidity or no fluidity, and lithium ion transmission mainly relies on liquid components. The content of liquid components is high (50-80wt.%), and it is easy to volatilize and burn at high temperatures. 3) Solid electrolyte: The electrolyte itself is solid and can support the transmission of lithium ions by itself. It has almost no liquid components (<5%wt.%), is not easy to decompose at high temperatures, and has low flammability.

[0004] The solvents based on liquid electrolytes are mostly carbonates (ethylene carbonate, diethyl carbonate), ethers (ethylene glycol dimethyl ether, tetrahydrofuran), carboxylates (methyl acetate), etc. These substances used in liquid electrolytes are prone to leakage, volatility, decomposition, and explosion. Their characteristics make lithium batteries easy to burn during storage. Therefore, flammable liquid electrolytes with poor thermal stability pose serious safety risks to their large-scale storage.

[0005] In order to solve the safety risks of large-scale storage of lithium batteries, the use of gel electrolytes (i.e., quasi-solid electrolytes) or solid electrolytes is one of the directions to improve the thermal stability of electrolytes and battery safety.

[0006] Among them, gel electrolytes (i.e., quasi-solid electrolytes) cannot completely solve the safety problems in batteries. The larger liquid components will also volatilize and explode, bringing safety hazards to the use of lithium batteries. For example, patent CN2021110517527 discloses the use of a flame-retardant polymer network and a conventional liquid electrolyte to construct a flame-retardant gel electrolyte, but the thermal stability of the gel electrolyte itself still depends on the liquid components therein, and its volatility and explosion characteristics have not been improved. In addition, its flame-retardant polymer network does not directly participate in lithium ion transmission, and its larger molecular weight and rigidity may even inhibit the movement of lithium ions in the liquid electrolyte, weakening its electrochemical properties.

[0007] In-situ polymerized solid electrolytes have the advantages of good electrode interface compatibility and high thermal stability. Polymer electrolytes using polymer monomers such as cyclic ethers and olefin carbonates have high ionic conductivity, simple preparation methods, and low costs, and have attracted widespread attention from scientific researchers. However, their thermal stability is poor and their flammability is high, making it difficult to fundamentally improve the thermal safety performance of lithium batteries. For example, as described in the literature (Angew. Chem. Int. Ed., 2022, 61, e202114805.), the linear cross-linked polymer electrolyte poly 1,3-epoxypentane has poor thermal stability and will completely decompose at 110°C. It is easy to decompose and volatilize flammable gases at high temperatures, reducing the safe operating space of the electrolyte. The ionic conductivity of olefin carbonate polymers is low, and additional liquid electrolyte components need to be added. Significant monomer volatilization will occur at <40°C, producing flammable gases (Energy Storage Mater., 2021, 39, 186.).

[0008] Based on the above problems, there is an urgent need to provide an electrolyte material that has both high thermal stability and flame retardancy, as well as excellent electrochemical properties, and can be widely used in various secondary batteries such as lithium batteries and sodium batteries. Summary of the Invention

[0009] Based on the above problems, the present invention provides an in-situ cross-linked polymerized solid electrolyte with high thermal stability and flame retardancy. The three-dimensional cross-linked network center formed in the solid electrolyte is used to improve the polymerization degree of the electrolyte, further enhancing the electrolyte's ① thermal stability and ② flame retardancy; at the same time, ③ during the application process, it can promote the conduction of lithium ions in the battery, further improving the battery's electrochemical performance (cycle stability) at room temperature and high temperature (20-130°C); and ④ ensuring its safety during use.

[0010] The technical solutions of the present invention are as follows:

[0011] An in-situ cross-linked polymerized solid electrolyte, comprising a lithium salt, an electrolyte and a flame-retardant cross-linking agent; preferably, further comprising a polymerization initiator and / or an electrolyte performance modifier; the electrolyte and the flame-retardant cross-linking agent undergo an in-situ polymerization reaction to generate a solid electrolyte having a three-dimensional cross-linked network central structure.

[0012] Wherein, the flame retardant crosslinking agent contains one or more structures of formula I and / or formula II;

[0013]

[0014] In some preferred embodiments, in Formula I and Formula II, R, R1, R2, and R3 are selected from alkyl and / or halogen-substituted alkyl; wherein the number of C atoms is 1 to 8.

[0015] In some more preferred embodiments, the alkyl group and the halogen-substituted alkyl group contain one or more of the following groups: hydroxyl group, epoxy group, olefin group, and amine group.

[0016] The flame retardant crosslinking agent contains a group having a three-dimensional network crosslinking center structure; the three-dimensional network crosslinking center with high flame retardant properties participates in the polymerization process of the solvent monomer, thereby improving the three-dimensional crosslinking degree, thermal stability and flame retardancy of the polyelectrolyte:

[0017] In some preferred embodiments, the flame retardant crosslinking agent is selected from any one or more of the following: triglycidyl isocyanurate (TGIC), tris(2-hydroxyethyl)isocyanurate (THEIC), triallyl isocyanurate (TAIC), 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-ethanol 10-oxide (DOPO) and its derivatives.

[0018] In some preferred embodiments, the electrolyte is a cyclic ether structured substance.

[0019] In some more preferred embodiments, the cyclic ether structured substance is selected from any one or more of the following: 1,3-dioxolane (DOL), 1,3,5-trioxane, 1,4-dioxane, 1,2-epoxycyclopentene, 3,4-epoxy-1-butene and derivatives thereof.

[0020] In some preferred embodiments, the electrolyte further comprises any one or more of the following: ethylene carbonate, dimethyl carbonate, fluoroethylene carbonate, and diethyl carbonate.

[0021] In some preferred embodiments, the polymerization initiator is selected from any one or more of the following: anionic initiator, cationic initiator, free radical initiator.

[0022] In some more preferred embodiments, the polymerization initiator is selected from any one or more of the following: lithium hexafluorophosphate, aluminum trifluoromethanesulfonate, stannous octoate, and azobisisobutyronitrile.

[0023] In some preferred embodiments, the electrolyte performance improver can enhance the cycle performance of the battery, and specifically includes at least one of a functionalized polymer, a functionalized filler, and a functionalized additive.

[0024] In some more preferred embodiments, the functionalized polymer has one or more of the following functions: improving polymerization molecular weight, flexibility, and film-forming properties; and is selected from any one or more of the following: polyethylene oxide, polyethyleneimine, poly(vinylidene fluoride-co-hexafluoropropylene), and polyacrylonitrile.

[0025] In some more preferred embodiments, the functional filler includes an inorganic inactive ceramic filler and / or a lithium ion conductive active filler; selected from any one or more of the following: Al2O3, SiO2, BaTiO3, CeO2, Li 6.4 La3Zr 1.4 Ta 0.6 O 12 、Li7La3Zr2O 12 、Li6PS5Cl、Li3PS4。

[0026] In some more preferred embodiments, the functional additive is selected from any one or more of the following: an interface stabilizer, a film-forming additive, an anti-overcharge additive; or selected from any one or more of the following: at least one of lithium nitrate, fluoroethylene carbonate, and lithium difluorooxalatoborate.

[0027] In some preferred embodiments, the lithium salt is selected from any one or more of the following: lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium hexafluorophosphate, lithium perchlorate, and lithium tetrafluoroborate.

[0028] The present application also provides a method for preparing the in-situ cross-linked polymerized solid electrolyte, comprising the following steps:

[0029] The in-situ cross-linked polymerized solid electrolyte can be obtained by dissolving lithium salt, flame retardant cross-linking agent and pre-selected components in electrolyte to cause in-situ polymerization reaction.

[0030] In some preferred embodiments, lithium salt, flame retardant crosslinking agent, electrolyte performance modifier and polymerization initiator are dispersed in the electrolyte, and an in-situ polymerization reaction occurs to obtain the in-situ crosslinked polymerized solid electrolyte.

[0031] In some more preferred embodiments, the preparation method is:

[0032] 1) First, dissolve the lithium salt in the electrolyte to form a basic electrolyte;

[0033] 2) dispersing a flame retardant crosslinking agent and an electrolyte performance improver in a basic electrolyte to form a mixed solution;

[0034] 3) The in-situ polymerization initiator is sequentially dispersed in the mixed solution to form an overall electrolyte solution, which is allowed to stand at 20° C. to 110° C. to carry out an in-situ polymerization reaction to form an in-situ cross-linked polymerized solid electrolyte.

[0035] In some preferred embodiments, in the mixed solution, the molar ratio of the flame retardant cross-linking agent to the electrolyte (cyclic ether solvent) is 1:50-100.

[0036] In some preferred embodiments, the concentration of the lithium salt in the mixed solution is 1.0M to 3.0M.

[0037] In some preferred embodiments, the mass fraction of the electrolyte performance improver in the mixed solution is 0.5-20%, preferably 5-20%.

[0038] In some preferred embodiments, the mass fraction of the polymerization initiator in the overall electrolyte is 0.5-3%.

[0039] The present application also provides a use of the in-situ cross-linked polymerized solid electrolyte in a lithium battery, wherein the components of the in-situ cross-linked polymerized solid electrolyte are mixed to form a mixed solution, which is then placed in a battery housing for an in-situ polymerization reaction to obtain a lithium battery having the in-situ cross-linked polymerized solid electrolyte;

[0040] The lithium battery further includes a positive electrode, a negative electrode and a separator.

[0041] In some preferred embodiments, the positive electrode comprises a lithium ion positive electrode material and / or a sodium ion positive electrode material;

[0042] In some more preferred embodiments, the lithium ion cathode material is selected from any one of the following: embedded LiCoO2, LiMnO2, Li2MnO3, LiNi x CO y Mn (1-x-y) O2; conversion S, Li2S, O2, air, FeF3, CuF3;

[0043] In some more preferred embodiments, the sodium ion positive electrode material is selected from any one of the following: NaFePO4, Na2MnO3.

[0044] In some preferred embodiments, the negative electrode comprises a lithium ion negative electrode material and / or a sodium ion negative electrode material;

[0045] In some preferred embodiments, the negative electrode includes a lithium ion negative electrode material and / or a sodium ion negative electrode material;

[0046] In some more preferred embodiments, the lithium ion negative electrode material is selected from any one of the following: graphite, metallic lithium, silicon, lithium alloy, lithium titanate;

[0047] In some more preferred embodiments, the sodium ion negative electrode material is selected from any one of the following: metallic sodium, sodium vanadium phosphate.

[0048] Beneficial effects of the present invention:

[0049] (1) The in-situ cross-linked polymerized solid electrolyte of the present invention improves the ion transmission rate of the polymer network by introducing flame retardant cross-linking agents such as isocyanurate and phosphaphenanthrene as the center of the three-dimensional cross-linked network, and performs ring-opening copolymerization with a cyclic ether solvent electrolyte. At the same time, it significantly improves the thermal stability (stable circulation in the range of 20 to 130°C), flame retardancy (cannot be ignited at a heating power of 0 to 10 kW) and electrochemical properties of the polymer solid electrolyte.

[0050] Thermal stability: Lithium metal batteries using the in-situ cross-linked polymeric solid electrolyte of the present invention can stably cycle for more than 100 cycles at 130°C, and lithium metal batteries using this electrolyte can stably cycle for more than 500 cycles at 20°C, with a capacity retention rate of >80%;

[0051] Flame retardancy: The in-situ cross-linked polymeric solid electrolyte of the present invention can inhibit the combustion and fire of the electrolyte and cannot be ignited under a heating power of 10kW, greatly improving the safety of the battery in extreme environments.

[0052] Electrochemical performance: The high thermal stability in-situ cross-linked polymeric solid electrolyte of the present invention improves both the bulk ion migration rate and the interfacial electrochemical stability of the electrolyte. The cross-linked network core and branches of the polymer electrolyte are also beneficial to the improvement of ionic conductivity (>3mS cm -1 ), and the three-dimensional network inhibits the migration of large-volume anions, improves the ion migration number (>0.8) and high-voltage resistance (>5V), and the high interface stability, ionic conductivity, and ion migration number jointly inhibit the decomposition of the electrolyte and the side reactions with the electrode, promotes the uniform deposition of the negative electrode, and thus ensures stable cycling in the range of 20 to 130 ° C.

[0053] (2) In the in-situ cross-linked polymerized solid electrolyte of the present invention, the components of the flame retardant cross-linking agent participate in the cross-linking polymerization process of the electrolyte cyclic ether structural monomers to form a solid three-dimensional polymer cross-linked network, which participates in lithium ion conduction and avoids the residual liquid components by copolymerization. There is no need to add other liquid electrolytes to participate in the lithium conduction process, thus avoiding the disadvantages of easy leakage, volatilization, decomposition and explosion of the liquid electrolyte, thereby ensuring safety.

[0054] The in-situ cross-linked polymerized solid electrolyte of the present invention can also add a small amount (liquid component <1wt.%) of commonly used liquid electrolyte (for example, ethylene carbonate, dimethyl carbonate, fluoroethylene carbonate, diethyl carbonate) to the solid electrolyte generated by in-situ polymerization, and utilize the liquid electrolyte and the solid three-dimensional polymer cross-linked network to simultaneously participate in the lithium ion conduction process, thereby further improving the electrochemical performance.

[0055] (3) Compared with conventional PEO / PVDF polymer electrolytes, the electrolyte of the present invention has lower viscosity and better fluidity, can fully penetrate into the particles of positive electrode materials and negative electrode materials, significantly improving the compatibility between the electrolyte and the electrode. The electrolyte obtained by polymerization has high ionic conductivity, which reduces the internal resistance of the battery and further improves the battery cycle performance.

[0056] (4) When the electrolyte described in the present invention is used, it is only necessary to evenly disperse the components and inject them into the battery to induce an in-situ polymerization reaction, thereby forming a polymer solid electrolyte in situ; the battery assembly process is simple, the polymerization method is simple, and the amount of additives used is low; it is conducive to reducing the cost of energy storage batteries and improving the prospects for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a flammability test of the high thermal stability in-situ cross-linked polymeric solid electrolyte in Example 1 of the present invention;

[0058] Figure 2 The charge and discharge curves of the lithium battery obtained using metallic lithium as the negative electrode, LiFePO4 as the working electrode, and the electrolyte of Example 1 at room temperature and 0.5C;

[0059] Figure 3 The charge and discharge curves of a lithium battery obtained by using metallic lithium as the negative electrode, LiFePO4 as the working electrode, and the electrolyte of Example 1 at 130°C and 0.5C. DETAILED DESCRIPTION

[0060] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0061] The abbreviations of the lithium salts and flame retardant crosslinking agents described in the following examples are as follows:

[0062] Lithium salts: lithium bis(fluorosulfonyl)imide is LiFSI, lithium bis(trifluoromethanesulfonyl)imide is LiTFSI, lithium nitrate is LiNO3, lithium difluorooxalatoborate is LiDFOB, lithium hexafluorophosphate is LiPF6, lithium tetrafluoroborate is LiBF4, and lithium bis(oxalatoborate) is LiBOB.

[0063] Flame retardant crosslinking agents: triglycidyl isocyanurate (TGIC), tris(2-hydroxyethyl) isocyanurate (THEIC), triallyl isocyanurate (TAIC), 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-ethanol 10-oxide (DOPO).

[0064] In the embodiment, 2032 type button battery was used for evaluation. The test conditions were as follows: lithium iron phosphate and lithium nickel cobalt manganese oxide were used as positive electrode materials, and the surface capacity was 1.0 mAh / cm 2A 500μm-thick lithium sheet was used as the negative electrode, and the amount of electrolyte used in each battery was 50μl. The battery cycle life was calculated based on an 80% capacity retention rate.

[0065] Example 1

[0066] A high thermal stability in-situ cross-linked polymerized solid electrolyte, wherein the lithium salt is LiTFSI, the electrolyte is 1,3-dioxolane (DOL) with a basic cyclic ether structure, the flame retardant cross-linker is triglycidyl isocyanurate (TGIC), the in-situ polymerization initiator is stannous octoate, and the electrolyte performance improver is LiNO3.

[0067] Its preparation method is:

[0068] 1) First, the main lithium salt LiTFSI is dissolved in the electrolyte DOL to form a basic electrolyte; the lithium salt concentration in the basic electrolyte is 2.0 mol / L;

[0069] 2) Based on the volume and mass of the basic electrolyte, 1 mol.% of a flame retardant crosslinking agent TGIC and 0.5 wt.% of an electrolyte performance improver LiNO3 are sequentially dispersed in the basic electrolyte to form a mixed solution;

[0070] 3) Based on the mass of the mixed solution, 1 wt% of an in-situ polymerization initiator, stannous octoate, was added and dispersed in the mixed solution to obtain a bulk electrolyte. The bulk electrolyte was placed in a battery casing and polymerized at 60°C for 24 hours, followed by a secondary polymerization at 80°C for 24 hours.

[0071] In the in-situ cross-linked polymerized solid electrolyte, the components of the flame retardant cross-linking agent participate in the cross-linking polymerization process of the electrolyte cyclic ether structural monomers to form a solid three-dimensional polymer cross-linked network, which participates in lithium ion conduction; among them, R is a CO lithium-conducting chain group of the matrix unit -COCCOC-, and the number of units ranges from 5 to 15.

[0072]

[0073] The lithium ion conductivity of the obtained polymer electrolyte is 5.54 mS cm -1 The upper limit of the voltage window is 5.30 V, the ion migration number is 0.808, there is no obvious decomposition at 100 ° C (quality retention is 99.8%), and it is not ignited when heated for 30 minutes at a heating power of 10 kW (shown in Figure 1 ).

[0074] Element substance Dosage lithium salts LiTFSI 2mol / L Electrolyte (basic cyclic ether substance) 1,3-Dioxolane (DOL) / Flame retardant crosslinker Triglycidyl isocyanurate (TGIC) 1 mol.% Electrolyte performance improver <![CDATA[LiNO3]]> 0.5wt.% In situ polymerization initiator Stannous octoate 1wt%

[0075] The polymer prepared above, i.e., the in-situ cross-linked polymeric solid electrolyte, was used for full battery testing with a metal lithium sheet as the negative electrode and LiFePO4 as the positive electrode. Figure 2 and Figure 3 The test results show that at room temperature, the battery's cycle life can reach 400 cycles, and at 130°C, the battery's cycle life can reach 100 cycles.

[0076] Comparative Example 1-1

[0077] On the basis of Example 1, the flame retardant cross-linking agent was omitted, and other components and steps remained unchanged to prepare the in-situ linear polymerization solid electrolyte and battery.

[0078] Based on Comparative Example 1-1, the flame retardant cross-linking agent was omitted, and cross-linking polymerization could not be performed to form a three-dimensional network central structure. Only the cyclic ether solvent monomers of the electrolyte were linearly polymerized, and their molecular weight was between 100 and 5000. Therefore, the solid electrolyte formed had a low degree of polymerization and the polymer product had poor thermal stability.

[0079]

[0080] Ionic conductivity is 4.73 mS cm -1 , the ion transference number is 0.553, the upper limit of the voltage window is 3.59 V, it decomposes to 47.9% of the initial mass at 100 °C, and is completely ignited in 6 seconds at a heating power of 10 kW.

[0081] At room temperature, the cycle life of the battery is only 62 cycles, and the battery cannot be stably cycled at temperatures of 60°C and above. Therefore, the flame retardancy, thermal stability, cross-linking degree, and battery performance are significantly lower than those in Example 1.

[0082] Comparative Example 1-2

[0083] Based on Example 1, the electrolyte containing cyclic ether solvents was omitted, so the prepared molecules had no long-chain ion transport path, and the obtained polymer ion conductivity was extremely low. Therefore, 80wt.% of 1M LiPF6-ethylene carbonate / diethyl carbonate (1:1v / v) liquid electrolyte was added as a lithium ion transport medium to prepare the electrolyte and battery.

[0084] At room temperature, the cycle life of the battery is only 154 cycles, and the number of cycles of the battery at 60°C is 53 cycles. It cannot be cycled stably at higher temperatures. Therefore, the flame retardancy, thermal stability, cross-linking degree, and battery performance are significantly lower than those in Example 1.

[0085] Example 2

[0086] On the basis of Example 1, the components were replaced as shown in the following table to prepare an in-situ cross-linked polymerized solid electrolyte and a battery thereof.

[0087]

[0088] The obtained monolithic electrolyte was placed in a battery case and polymerized at 60° C. for 24 hours, followed by secondary polymerization at 80° C. for 24 hours.

[0089] The polymer electrolyte was used to prepare a lithium metal sheet as the negative electrode at 60 ° C with LiNi 0.5 Co 0.2 Mn 0.3 The full battery test was carried out using O2 as the positive electrode. It was found that the battery cycle life can reach 200 cycles.

[0090] Comparative Example 2

[0091] On the basis of Example 2, the flame retardant cross-linking agent was omitted, and other components and steps remained unchanged to prepare the in-situ linear polymerization solid electrolyte and battery.

[0092] At room temperature, the cycle life of the battery is only 8 cycles, so the flame retardancy, thermal stability, cross-linking degree and battery performance are significantly lower than those in Example 2.

[0093] Example 3

[0094] Element substance Dosage lithium salts LiTFSI 2mol / L Electrolyte (basic cyclic ether substance) 1,3,5-Trioxane / Flame retardant crosslinker Triglycidyl isocyanurate (THEIC) 1 mol.% Electrolyte performance improver <![CDATA[Vinyl Fluoroethylene Carbonate (FEC) and LiNO3]]> 5wt.% and 1wt.% In situ polymerization initiator Stannous octoate 1wt.%

[0095] The obtained monolithic electrolyte was placed in a battery case and polymerized at 60° C. for 24 hours, followed by secondary polymerization at 110° C. for 24 hours.

[0096] The gel electrolyte was used to conduct a full battery test with a metal lithium sheet as the negative electrode and LiFePO4 as the positive electrode at 100°C. The test found that the battery cycle life can reach 50 cycles.

[0097] Comparative Example 3

[0098] On the basis of Example 3, the flame retardant cross-linking agent was omitted, and other components and steps remained unchanged to prepare the in-situ linear polymerization solid electrolyte and battery.

[0099] At 100°C, the battery cannot cycle normally.

[0100] Example 4

[0101] Element substance Dosage lithium salts LiTFSI 3mol / L Electrolyte (basic cyclic ether substance) 1,3-Dioxolane (DOL) / Flame retardant crosslinking agent TGIC 1 mol.% Electrolyte performance improver Fluoroethylene carbonate (FEC) 5wt.% In situ polymerization initiator <![CDATA[LiPF6]]> 1wt.%

[0102] The obtained monolithic electrolyte was placed in a battery case and polymerized at 60° C. for 24 hours, followed by secondary polymerization at 80° C. for 24 hours.

[0103] The prepared in-situ cross-linked polymerized solid electrolyte was used to take lithium metal sheet as negative electrode, LiNi 0.5 Co 0.2 Mn 0.3A full battery test with O2 as the positive electrode found that the battery cycle life can reach 120 cycles at room temperature.

[0104] Comparative Example 4

[0105] On the basis of Example 4, the flame retardant cross-linking agent was omitted, and other components and steps remained unchanged to prepare the in-situ linear polymerization solid electrolyte and battery.

[0106] At room temperature, the cycle life of the battery is only 82 cycles, so the flame retardancy, thermal stability, cross-linking degree and battery performance are significantly lower than those in Example 4.

[0107] Example 5

[0108] Element substance Dosage lithium salts LiTFSI and LiFSI 1mol / L and 1mol / L Electrolyte (basic cyclic ether substance) 1,4-Dioxane / Flame retardant crosslinking agent THEIC 1 mol.% Electrolyte performance improver <![CDATA[Polyethylene oxide and Li 6.4 La3Zr 1.4 Ta 0.6 O 12 > 10wt.% and 10wt.% In situ polymerization initiator Stannous octoate 1wt.%

[0109] The obtained monolithic electrolyte was placed in a battery case and polymerized at 60° C. for 24 hours, followed by secondary polymerization at 80° C. for 24 hours.

[0110] The prepared in-situ cross-linked polymerized solid electrolyte was used to take lithium metal sheet as negative electrode, LiNi 0.8 Co 0.1 Mn 0.1 A full battery test with O2 as the positive electrode found that the battery cycle life can reach 420 cycles at room temperature.

[0111] Comparative Example 5

[0112] On the basis of Example 5, the flame retardant cross-linking agent was omitted, and other components and steps remained unchanged to prepare the in-situ linear polymerization solid electrolyte and battery.

[0113] At room temperature, the cycle life of the battery is only 200 cycles, which is more than 1 times lower than that of Example 5. Therefore, the flame retardancy, thermal stability, cross-linking degree and battery performance are significantly lower than those of Example 5.

[0114] Example 6

[0115]

[0116] The preparation method is as follows: lithium salt is added to a mixed solution of 1,3,5-trioxane and DOL to a concentration of 3.0 mol / L. 15% by mass of PVDF-HFP, 2.0% by mass of FEC, and 2% by mole of TGIC are then added, and the mixture is stirred at room temperature for 24 hours. Finally, 0.5% by mass of Al(otf)3 is added.

[0117] The above-mentioned overall electrolyte was placed in a battery casing and polymerized in the battery at 60° C. for 24 hours.

[0118] The polymer electrolyte is used to use lithium metal sheet as negative electrode, LiNi 0.6 Co 0.2 Mn 0.2 A full battery test with O2 as the positive electrode found that the battery's cycle life can reach 275 cycles at room temperature.

[0119] Comparative Example 6

[0120] On the basis of Example 6, the flame retardant cross-linking agent was omitted, and other components and steps remained unchanged to prepare the in-situ linear polymerization solid electrolyte and battery.

[0121] At room temperature, the cycle life of the battery is only 180 cycles, which is significantly lower than that of Example 6. Therefore, the flame retardancy, thermal stability, cross-linking degree and battery performance are significantly lower than those of Example 6.

[0122] Example 7

[0123] Element substance Dosage lithium salts LiTFSI and LiDFOB 3mol / L Electrolyte (basic cyclic ether substance) DOL / Flame retardant crosslinker TAIC 1 mol.% Electrolyte performance improver <![CDATA[PAN, Al2O3, and LiNO3]]> 15wt.% and 5wt.% and 0.5wt.% In situ polymerization initiator LiDFOB 5wt.%

[0124] The preparation method is as follows: LiTFSI salt is added to DOL to a concentration of 3.0 mol / L. Then, 15% by mass of PAN, 5% by mass of Al2O3, 0.5% by mass of LiNO3, and 1% by mole of TAIC are added and stirred at 60°C for 24 hours to form a well-mixed solution. Finally, 5% by mass of LiDFOB is added. This overall electrolyte solution is placed in the battery casing and polymerized at 60°C for 24 hours, followed by a secondary polymerization at 80°C for 24 hours.

[0125] The polymer electrolyte is used to use lithium metal sheet as negative electrode, LiNi 0.6 Co 0.2 Mn 0.2 A full battery test with O2 as the positive electrode found that the battery's cycle life can reach 210 cycles at room temperature.

[0126] Comparative Example 7

[0127] On the basis of Example 7, the flame retardant cross-linking agent was omitted, and other components and steps remained unchanged to prepare the in-situ linear polymerization solid electrolyte and battery.

[0128] At room temperature, the cycle life of the battery is only 142 cycles, which is significantly lower than that of Example 7. Therefore, the flame retardancy, thermal stability, cross-linking degree and battery performance are significantly lower than those of Example 7.

[0129] Example 8

[0130]

[0131]

[0132] The above-mentioned overall electrolyte was first polymerized at 60°C for 30 minutes, then placed in a battery shell, polymerized at 60°C for 24 hours, and then polymerized again at 80°C for 24 hours. 0.6 Co 0.2 Mn 0.2 A full battery test with O2 as the positive electrode found that the battery's cycle life can reach 160 cycles at room temperature.

[0133] Comparative Example 8

[0134] On the basis of Example 8, the flame retardant cross-linking agent was omitted, and other components and steps remained unchanged to prepare the in-situ linear polymerization solid electrolyte and battery.

[0135] At room temperature, the cycle life of the battery is only 86 cycles, which is 1 times lower than that of Example 8. Therefore, the flame retardancy, thermal stability, cross-linking degree and battery performance are significantly lower than those of Example 8.

[0136] Example 9

[0137]

[0138] The above-mentioned overall electrolyte was first polymerized at 60°C for 30 minutes, then placed in the battery shell, polymerized at 60°C for 24 hours in the battery, and then polymerized again at 80°C for 24 hours. 0.6 Co 0.2 Mn 0.2 A full battery test with O2 as the positive electrode found that the battery's cycle life can reach 189 cycles at room temperature.

[0139] Comparative Example 9

[0140] On the basis of Example 9, the flame retardant cross-linking agent was omitted, and other components and steps remained unchanged to prepare the in-situ linear polymerization solid electrolyte and battery.

[0141] At room temperature, the cycle life of the battery is only 122 cycles, which is significantly lower than that of Example 9. Therefore, the flame retardancy, thermal stability, cross-linking degree and battery performance are significantly lower than those of Example 9.

[0142] Example 10

[0143]

[0144]

[0145] The above-mentioned overall electrolyte was placed in the battery shell and polymerized at 80°C for 24 hours. The polymer electrolyte was used to prepare a lithium metal sheet as the negative electrode, LiNi 0.6 Co 0.2 Mn 0.2 A full battery test with O2 as the positive electrode found that the battery's cycle life can reach 220 cycles at room temperature.

[0146] Comparative Example 10

[0147] On the basis of Example 10, the flame retardant cross-linking agent was omitted, and other components and steps remained unchanged to prepare the in-situ linear polymerization solid electrolyte and battery.

[0148] At room temperature, the cycle life of the battery is only 162 cycles, which is significantly lower than that of Example 10. Therefore, the flame retardancy, thermal stability, cross-linking degree and battery performance are significantly lower than those of Example 10.

[0149] Example 11

[0150]

[0151] The above-mentioned overall electrolyte was polymerized in the battery case at 80°C for 24 hours. The polymer electrolyte was used to prepare a lithium metal sheet as the negative electrode, LiNi 0.5 Co 0.2 Mn 0.3 A full battery test with O2 as the positive electrode found that the battery's cycle life can reach 240 cycles at room temperature.

[0152] Comparative Example 11

[0153] On the basis of Example 11, the flame retardant cross-linking agent was omitted, and other components and steps remained unchanged to prepare the in-situ linear polymerization solid electrolyte and battery.

[0154] At room temperature, the cycle life of the battery is only 164 cycles, which is significantly lower than that of Example 11. Therefore, the flame retardancy, thermal stability, cross-linking degree and battery performance are significantly lower than those of Example 11.

[0155] Example 12

[0156]

[0157] The preparation method is as follows: DOL, 1,3,5-trioxane and 1,2-epoxycyclopentene are mixed in a ratio of 2:2:1, and then lithium salt (LiFSI:LiBOB molar ratio is 4:1) is added to make the concentration reach 3.0 mol / L.

[0158] Then add 10% by mass of PVDF-HFP and 10% by mass of Li6.4 La3Zr 1.4 Ta 0.6 O 12 , 1.5% mole fraction of flame retardant crosslinking agent, after stirring at room temperature for 24 hours, add 1% mass fraction of polymerization initiator and stir to a uniform solution.

[0159] The above-mentioned overall electrolyte was polymerized in a battery at 80°C for 24 hours. The polymer electrolyte was used to prepare a lithium metal sheet as the negative electrode, LiNi 0.5 Co 0.2 Mn 0.3 A full battery test with O2 as the positive electrode found that the battery's cycle life can reach 198 cycles at room temperature.

[0160] Comparative Example 12

[0161] On the basis of Example 12, the flame retardant cross-linking agent was omitted, and other components and steps remained unchanged to prepare the in-situ linear polymerization solid electrolyte and battery.

[0162] At room temperature, the cycle life of the battery is only 120 cycles, which is significantly lower than that of Example 12. Therefore, the flame retardancy, thermal stability, cross-linking degree and battery performance are significantly lower than those of Example 12.

Claims

1. An in-situ cross-linked polymerized solid electrolyte, wherein: The raw materials for preparing the solid electrolyte include lithium salt, electrolyte and flame retardant crosslinking agent; the electrolyte and flame retardant crosslinking agent undergo in-situ polymerization reaction to generate a solid electrolyte with a three-dimensional crosslinked network core structure; The flame retardant crosslinking agent is selected from any one or more of the following: triglycidyl isocyanurate (TGIC), tris(2-hydroxyethyl)isocyanurate (THEIC), triallyl isocyanurate (TAIC), 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-ethanol 10-oxide (DOPO) and its derivatives; The electrolyte is a cyclic ether structured substance selected from any one or more of the following: 1,3-dioxolane (DOL), 1,3,5-trioxane, 1,4-dioxane, 1,2-epoxycyclopentene, 3,4-epoxy-1-butene and their derivatives; The lithium salt is selected from any one or more of the following: lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium hexafluorophosphate, and lithium tetrafluoroborate.

2. An in-situ cross-linked polymerized solid electrolyte according to claim 1, wherein: Also included are polymerization initiators and / or electrolyte performance improvers.

3. An in-situ cross-linked polymerized solid electrolyte according to claim 2, wherein: The polymerization initiator is selected from any one or more of the following: anionic initiator, cationic initiator, free radical initiator.

4. An in-situ cross-linked polymerized solid electrolyte according to claim 3, wherein: The polymerization initiator is selected from any one or more of the following: aluminum trifluoromethanesulfonate, stannous octoate, and azobisisobutyronitrile.

5. The in-situ cross-linked polymerized solid electrolyte according to claim 2, wherein: The electrolyte performance improver includes at least one of functionalized polymers, functionalized fillers, and functionalized additives.

6. The in-situ cross-linked polymerized solid electrolyte according to claim 5, wherein: The functionalized polymer is selected from any one or more of the following: polyethylene oxide, polyethyleneimine, poly(vinylidene fluoride-co-hexafluoropropylene), and polyacrylonitrile.

7. The in-situ cross-linked polymerized solid electrolyte according to claim 5, wherein: The functionalized filler includes an inorganic inactive ceramic filler and / or a lithium ion conductive active filler.

8. An in-situ cross-linked polymerized solid electrolyte according to claim 5 or 7, wherein: The functional filler is selected from any one or more of the following: Al2O3, SiO2, BaTiO3, CeO2, Li 6.4 La3Zr 1.4 Ta 0.6 O 12 、Li7La3Zr2O 12 、Li6PS5Cl、Li3PS4。 9. The in-situ cross-linked polymerized solid electrolyte according to claim 5, wherein: The functional additive is selected from any one or more of the following: an interface stabilizer, a film-forming additive, and an anti-overcharge additive.

10. An in-situ cross-linked polymerized solid electrolyte according to claim 5 or 9, wherein: The functional additive is selected from any one or more of the following: lithium nitrate, fluoroethylene carbonate, and lithium difluorooxalatoborate.

11. The method for preparing the in-situ cross-linked polymerized solid electrolyte according to any one of claims 1 to 10, comprising the following steps: The in-situ cross-linked polymerized solid electrolyte can be obtained by dissolving lithium salt, flame retardant cross-linking agent and pre-selected components in electrolyte to cause in-situ polymerization reaction.

12. Use of the in situ cross-linked polymerized solid electrolyte according to any one of claims 1 to 10 in a lithium battery, comprising mixing the component raw materials of the in situ cross-linked polymerized solid electrolyte to form a mixed solution, and then placing the mixed solution in a battery shell to carry out an in situ polymerization reaction to obtain a lithium battery having the in situ cross-linked polymerized solid electrolyte.

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