In-situ polymerization solid-state organic-inorganic composite electrolyte, preparation method and sodium ion battery

Abstract

The present invention relates to an in-situ polymerized solid-state organic-inorganic composite electrolyte, a preparation method and a sodium ion battery. The in-situ polymerized solid-state organic-inorganic composite electrolyte is obtained by initiating polymerization of an inorganic solid electrolyte particle coating on a diaphragm and an in-situ polymerized precursor electrolyte at 40°C-80°C; the inorganic solid electrolyte material constituting the inorganic solid electrolyte particle coating includes one or more of the fast ion conductors NASICON, Na-β"-Al2O3 or Na3PS4; the in-situ polymerized precursor electrolyte includes a polymerizable monomer, a cross-linking agent, a sodium salt, a solvent, an additive and a free radical initiator; wherein the proportion of the solvent is 0 or not 0, and the proportion of the additive is 0 or not 0; the solid-liquid interface contact angle between the inorganic solid electrolyte particle coating on the diaphragm and the in-situ polymerized precursor electrolyte is 0° to 10°.

Description

Technical Field

[0001] The present invention relates to the field of material technology, and in particular to an in-situ polymerized solid-state organic-inorganic composite electrolyte and a sodium ion battery. Background Art

[0002] Global lithium reserves are limited, making lithium-ion batteries inadequate for both electric vehicles and large-scale energy storage. Furthermore, conventional lithium-ion batteries, due to their widespread use of flammable organic liquid electrolytes, present serious safety risks. Sodium-ion batteries share a similar "rocking chair" operating mechanism to lithium-ion batteries. Furthermore, sodium resources are naturally abundant, readily available, and compatible with lithium-ion battery production lines. Their low cost makes them a viable alternative to lithium-ion batteries in some scenarios.

[0003] Solidifying the electrolyte is an effective way to improve battery safety performance. Therefore, the development of highly safe solid-state sodium-based batteries has become one of the important technical routes to meet the needs of large-scale energy storage.

[0004] However, the production process of conventional solid-state batteries is incompatible with traditional liquid battery production lines, resulting in high battery manufacturing costs. Furthermore, battery interface problems caused by solid-solid interface contact can seriously affect the performance of solid-state batteries.

[0005] To this end, the industry has begun researching pure polymer in-situ polymerized electrolytes. For example, patent applications CN111944099A, "Method and application of in-situ thermally initiated preparation of all-solid-state polymer electrolytes," and CN108493486A, "Method for preparing an in-situ polymerized solid-state battery," present certain challenges in practical applications. Sodium salts have low solubility in low-solvent conditions, and the polymerization precursor electrolyte has a higher viscosity than conventional electrolytes, resulting in low injection efficiency. Furthermore, the crosslinker in the system primarily serves to enhance the mechanical strength and thermal stability of the solid electrolyte after in-situ polymerization. However, using crosslinker monomers containing multiple double bonds makes it difficult to fully polymerize the double bonds in a single process due to the excessively high localized double bond content. Consequently, residual unsaturated bonds remain after polymerization, affecting the electrochemical performance of the solid electrolyte. Therefore, pure polymer in-situ polymerized electrolytes, with these drawbacks, cannot be widely applied. Summary of the Invention

[0006] Embodiments of the present invention provide an in-situ polymerized solid-state organic-inorganic composite electrolyte, a preparation method, and a sodium-ion battery. This method involves injecting an in-situ polymerized precursor electrolyte into a battery housing with a separator coated with inorganic solid electrolyte particles, and then thermally initiating in-situ polymerization to achieve in-situ solidification of the electrolyte within the battery. This results in an in-situ polymerized solid-state organic-inorganic composite electrolyte, which provides the battery with improved dendrite suppression and high capacity retention.

[0007] In a first aspect, an embodiment of the present invention provides an in-situ polymerized solid-state organic-inorganic composite electrolyte, wherein the in-situ polymerized solid-state organic-inorganic composite electrolyte is obtained by initiating polymerization of an inorganic solid electrolyte particle coating on a diaphragm and an in-situ polymerized precursor electrolyte at 40°C-80°C;

[0008] The inorganic solid electrolyte material constituting the inorganic solid electrolyte particle coating includes one or more of the fast ion conductors NASICON, Na-β"-Al2O3 or Na3PS4;

[0009] The in-situ polymerization precursor electrolyte comprises: a polymerization monomer, a cross-linking agent, a sodium salt, a solvent, an additive, and a free radical initiator; wherein the proportion of the solvent is 0 or not 0, and the proportion of the additive is 0 or not 0;

[0010] The solid-liquid interface contact angle between the inorganic solid electrolyte particle coating on the diaphragm and the in-situ polymerization precursor electrolyte is 0° to 10°.

[0011] Preferably, the polymerizable monomers include: one or more of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and methyl methacrylate (MMA);

[0012] The cross-linking agent includes: trimethylolpropane triacrylate and / or pentaerythritol tetraacrylate;

[0013] The sodium salt includes one or more of NaPF6, NaClO4, NaTFSI, NaFSI, NaBF4, and NaDFOB;

[0014] The solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether;

[0015] The additives include: one or more of fluoroethylene carbonate and vinyl sulfate;

[0016] The free radical initiator includes: azobisisobutyronitrile and / or dibenzoyl oxide;

[0017] Among them, the sum of the mass of the polymerization monomer and the cross-linking agent accounts for 1%-90% of the total mass of the in situ polymerization precursor electrolyte, the mass of the sodium salt accounts for 3%-60% of the total mass of the in situ polymerization precursor electrolyte, the mass of the solvent accounts for 0-95% of the total mass of the in situ polymerization precursor electrolyte, the mass of the additive accounts for 0-10% of the total mass of the in situ polymerization precursor electrolyte, and the mass of the free radical initiator accounts for 0.5%-3% of the total mass of the in situ polymerization precursor electrolyte.

[0018] Preferably, the inorganic solid electrolyte particle coating is a double-sided coating or a single-sided coating on the diaphragm, and the coating thickness on each side is 0.5-10 μm; the base film of the diaphragm is a polypropylene PP single-layer film or a polyethylene PE single-layer film or a PP / PE / PP multi-layer composite microporous film.

[0019] In a second aspect, an embodiment of the present invention provides a method for preparing the in-situ polymerization solid-state organic-inorganic composite electrolyte according to the first aspect, the preparation method comprising:

[0020] After fully mixing the polymerization monomer, cross-linking agent, sodium salt, solvent, additive and free radical initiator in advance to form an in-situ polymerization precursor electrolyte, inject it into a battery equipped with a diaphragm coated with inorganic solid electrolyte particles, and keep it at 40°C-80°C for 6-24 hours to initiate polymerization, so that the in-situ polymerization precursor electrolyte and the inorganic solid electrolyte are in-situ solidified on the diaphragm inside the battery to form the in-situ polymerization solidified organic-inorganic composite electrolyte;

[0021] Wherein, the inorganic solid electrolyte material includes: one or more of the fast ion conductor NASICON, Na-β"-Al2O3 or Na3PS4;

[0022] The proportion of the solvent is 0 or not 0, and the proportion of the additive is 0 or not 0;

[0023] The solid-liquid interface contact angle between the inorganic solid electrolyte particle coating on the diaphragm and the in-situ polymerization precursor electrolyte is 0° to 10°.

[0024] Preferably, the polymerizable monomers include: one or more of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and methyl methacrylate (MMA);

[0025] The cross-linking agent includes: trimethylolpropane triacrylate and / or pentaerythritol tetraacrylate;

[0026] The sodium salt includes one or more of NaPF6, NaClO4, NaTFSI, NaFSI, NaBF4, and NaDFOB;

[0027] The solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether;

[0028] The additives include: one or more of fluoroethylene carbonate and vinyl sulfate;

[0029] The free radical initiator includes: azobisisobutyronitrile and / or dibenzoyl oxide;

[0030] Among them, the sum of the mass of the polymerization monomer and the cross-linking agent accounts for 1%-90% of the total mass of the in situ polymerization precursor electrolyte, the mass of the sodium salt accounts for 3%-60% of the total mass of the in situ polymerization precursor electrolyte, the mass of the solvent accounts for 0-95% of the total mass of the in situ polymerization precursor electrolyte, the mass of the additive accounts for 0-10% of the total mass of the in situ polymerization precursor electrolyte, and the mass of the free radical initiator accounts for 0.5%-3% of the total mass of the in situ polymerization precursor electrolyte.

[0031] Preferably, the inorganic solid electrolyte particle coating is a double-sided coating or a single-sided coating on the diaphragm, and the coating thickness on each side is 0.5-10 μm; the base film of the diaphragm is a polypropylene PP single-layer film or a polyethylene PE single-layer film or a PP / PE / PP multi-layer composite microporous film.

[0032] In a third aspect, an embodiment of the present invention provides a sodium ion battery comprising the in-situ polymerized solid-state organic-inorganic composite electrolyte described in the first aspect above.

[0033] The in-situ polymerization solid-state organic-inorganic composite electrolyte proposed by the present invention is obtained by injecting an in-situ polymerization precursor electrolyte into a battery housing having a diaphragm coated with inorganic solid electrolyte particles and performing thermal in-situ polymerization. Since a diaphragm having an inorganic solid electrolyte particle coating is used, the solid-liquid interface contact angle between the diaphragm and the in-situ polymerization precursor electrolyte is 0-10°, so that the injected in-situ polymerization precursor electrolyte can be quickly spread to achieve the purpose of complete infiltration. The excellent wettability of the diaphragm will increase the injection efficiency. Since the electrode is fully infiltrated before polymerization, the in-situ polymerization solid-state organic-inorganic composite electrolyte formed has good contact with the electrode, and a protective layer will also be formed at the interface to avoid continuous decomposition of the internal inorganic solid electrolyte. The main effect of adding a cross-linking agent to the system is to improve the mechanical strength of the solid electrolyte after in-situ polymerization and increase the thermal stability of the solid electrolyte. However, as a cross-linking agent monomer containing multiple double bonds (trimethylolpropane triacrylate contains three double bonds, pentaerythritol tetraacrylate contains four double bonds), due to the excessively high content of double bonds in the local space, it is difficult to complete the complete polymerization of its own double bonds under separate conditions. After the polymerization, there will be residual unsaturated bonds, which will affect the electrochemical properties of the solid electrolyte. The present invention can fully copolymerize with the cross-linking agent to improve the conversion rate by introducing monomers such as VC, VEC and MMA, and has the effect of protecting the electrode interface by a film-forming additive. At the same time, it improves the solubility of the sodium salt under the condition of no solvent or little solvent, reduces the viscosity of the in-situ polymerization precursor electrolyte, and improves the injection efficiency. The in-situ polymerization solid-state organic-inorganic composite electrolyte of the present invention is applied in sodium ion batteries and has good dendrite suppression ability and high battery capacity retention rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The technical solutions of the embodiments of the present invention are further described in detail below through the accompanying drawings and examples.

[0035] Figure 1 A is a SEM characterization image of the PP separator in Example 1 of the present invention;

[0036] Figure 1 B is a graph showing the contact angle between the PP separator and the polymer precursor electrolyte in Example 1 of the present invention;

[0037] Figure 1 C is a SEM characterization image of the NAS ICON coated diaphragm of Example 1 of the present invention;

[0038] Figure 1 D is a graph showing the contact angle between the diaphragm formed by polymerization and the polymerization precursor electrolyte in Example 1 of the present invention;

[0039] Figure 2 1 is a comparison of the cycle performance curves of Example 1, Comparative Example 1 and Comparative Example 2 of the present invention;

[0040] Figure 3 is the cycle performance curve of Example 2 of the present invention;

[0041] Figure 4 This is the cycle performance curve of Example 3 of the present invention. DETAILED DESCRIPTION

[0042] The present invention will be further described below through the accompanying drawings and specific embodiments, but it should be understood that these embodiments are only used for more detailed description and should not be understood as limiting the present invention in any form, that is, they are not intended to limit the scope of protection of the present invention.

[0043] The present invention proposes an in-situ polymerized solid-state organic-inorganic composite electrolyte, which is obtained by initiating polymerization of an inorganic solid electrolyte particle coating on a diaphragm and an in-situ polymerized precursor electrolyte at 40°C-80°C.

[0044] The inorganic solid electrolyte material constituting the inorganic solid electrolyte particle coating includes one or more of the fast ion conductors NASICON, Na-β"-Al2O3 or Na3PS4;

[0045] The in-situ polymerization precursor electrolyte includes: a polymerization monomer, a cross-linking agent, a sodium salt, a solvent, an additive, and a free radical initiator; wherein the proportion of the solvent may be 0 or not 0, and the proportion of the additive may also be 0 or not 0;

[0046] The solid-liquid interface contact angle between the inorganic solid electrolyte particle coating on the diaphragm and the in-situ polymerization precursor electrolyte is 0° to 10°.

[0047] The polymerizable monomers include: one or more of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and methyl methacrylate (MMA);

[0048] Crosslinking agents include: trimethylolpropane triacrylate and / or pentaerythritol tetraacrylate;

[0049] Sodium salts include one or more of NaPF6, NaClO4, NaTFSI, NaFSI, NaBF4, and NaDFOB;

[0050] The solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether;

[0051] The additives include: one or more of fluoroethylene carbonate and vinyl sulfate;

[0052] Free radical initiators include: azobisisobutyronitrile and / or dibenzoyl oxide;

[0053] Among them, the sum of the mass of the polymerization monomer and the cross-linking agent accounts for 1%-90% of the total mass of the in situ polymerization precursor electrolyte, the mass of the sodium salt accounts for 3%-60% of the total mass of the in situ polymerization precursor electrolyte, the mass of the solvent accounts for 0-95% of the total mass of the in situ polymerization precursor electrolyte, the mass of the additive accounts for 0-10% of the total mass of the in situ polymerization precursor electrolyte, and the mass of the free radical initiator accounts for 0.5%-3% of the total mass of the in situ polymerization precursor electrolyte.

[0054] The inorganic solid electrolyte particle coating is a double-sided coating or a single-sided coating on the diaphragm, and the coating thickness on each side is 0.5-10 μm; the base film of the diaphragm is a polypropylene (PP) single-layer film or a polyethylene (PE) single-layer film or a PP / PE / PP multi-layer composite microporous film.

[0055] During preparation, the above-mentioned polymerization monomers, cross-linking agent, sodium salt, solvent, additives and free radical initiator are fully mixed in advance to form an in-situ polymerization precursor electrolyte, which is then injected into a battery equipped with a diaphragm coated with inorganic solid electrolyte particles. The mixture is kept warm at 40°C-80°C for 6-24 hours to initiate polymerization, so that the in-situ polymerization precursor electrolyte and the inorganic solid electrolyte are in-situ solidified on the diaphragm inside the battery to form an in-situ polymerized solidified organic-inorganic composite electrolyte.

[0056] The present invention adopts the barrier film with inorganic solid electrolyte particle coating, and the solid-liquid interface contact angle of itself and in-situ polymerization precursor electrolyte is 0-10 °, so that the injection in-situ polymerization precursor electrolyte of injection can be spread rapidly, reaches the purpose of soaking in completely.The excellent wettability of barrier film can increase liquid injection efficiency.Owing to fully soaking in electrode before polymerization, therefore the contact property of formed in-situ polymerization solidification organic-inorganic composite electrolyte and electrode is good, also can form protective layer at interface, avoid the continuous decomposition of internal inorganic solid electrolyte.The main effect of adding cross-linking agent in system is to improve the mechanical strength of solid electrolyte after in-situ polymerization, increase the thermal stability of solid electrolyte, but as the cross-linking agent monomer (trimethylolpropane triacrylate contains three double bonds, pentaerythritol tetraacrylate contains four double bonds) containing multiple double bonds, because local space double bond content is too high, be difficult to complete the whole polymerization of self double bond under independent condition, have residual unsaturated bond to exist after autopolymerization, affect the electrochemical performance of solid electrolyte. The present invention, by introducing monomers such as VC, VEC, and MMA, can fully copolymerize with the crosslinker to improve the conversion rate, and has the function of protecting the electrode interface as a film-forming additive. At the same time, it improves the solubility of sodium salts under solvent-free or low-solvent conditions, reduces the viscosity of the in-situ polymerization precursor electrolyte, and improves the injection efficiency. The in-situ polymerization solid-state organic-inorganic composite electrolyte of the present invention is used in sodium-ion batteries and has good dendrite suppression ability and high battery capacity retention rate.

[0057] To better understand the technical solution provided by the present invention, the following specific examples are used to illustrate the specific process for preparing the in-situ polymerized solid-state organic-inorganic composite electrolyte of the present invention and its characteristics.

[0058] Example 1

[0059] This embodiment uses NaNi 2 / 9 Cu 1 / 9 Fe 1 / 3 Mn 1 / 3 O2 is the positive electrode material and hard carbon is the negative electrode material. The active material accounts for 90wt% of the electrode, the conductive additive Super P accounts for 5wt%, and the binder polyvinylidene fluoride (PVDF) accounts for 5wt%. The positive electrode surface loading is 11mg / cm 2 , the negative electrode surface loading is 6.2 mg / cm 2 The diaphragm is a PP diaphragm coated on both sides with NASICON particles, and the coating thickness on one side is 2μm.

[0060] The polymerization precursor electrolyte consists of vinylene carbonate (7.2wt%), pentaerythritol tetraacrylate (1.6wt%), NaPF6 (11.2wt%), ethylene carbonate (38.5wt%), diethyl carbonate (38.5wt%), fluoroethylene carbonate (2wt%), and azobisisobutyronitrile (AIBN) (1wt%). After injection, the battery is packaged, kept at 70°C for 16 hours, and then cooled to room temperature to complete the preparation of the solid-state battery. It should be noted here that the electrolyte becomes solid after heating and polymerization. Although it contains a solvent and is in a semi-solid state, it is also a solid-state battery.

[0061] Figure 1 A is a SEM characterization image of the PP separator in Example 1 of the present invention; Figure 1 B is a graph showing the contact angle between the PP separator and the polymer precursor electrolyte in Example 1 of the present invention; Figure 1 C is a SEM characterization image of the NASICON coated diaphragm formed by in-situ polymerization in Example 1 of the present invention; Figure 1 D is a contact angle test diagram of the diaphragm formed by polymerization in Example 1 of the present invention and the polymerization precursor electrolyte; it can be seen that the contact angle changes from the original 59.1° to 0°.

[0062] A sodium ion battery using the same positive electrode, negative electrode, conventional electrolyte (1MNaClO4, EC / diethyl carbonate (DEC=1:1, 2wt% fluoroethylene carbonate (FEC)) and PP separator was used as comparative example 1, and a sodium ion battery using the same positive electrode, negative electrode, PP separator coated with the same NASICON particles and conventional electrolyte was used as comparative example 2, and the performance was compared with that of Example 1. The test conditions were an operating voltage range of 1.5-4V, and a cycle rate of 0.33C for 200 cycles. Figure 2The following is a comparison of the cycling performance curves of Example 1, Comparative Example 1, and Comparative Example 2. As can be seen, Example 1 has the highest capacity retention, reaching 78.7%. This demonstrates that the in-situ polymerized solid-state organic-inorganic composite electrolyte, due to its stable interface at the electrode interface, reduces side reactions and extends the battery life.

[0063] Example 2

[0064] This embodiment uses Na3(VOPO4)2F as the positive electrode material (working voltage range 2.8-4.2V), sodium foil as the negative electrode material, the active material mass of the electrode sheet accounts for 70wt%, the conductive additive SuperP accounts for 20wt%, and the binder sodium alginate accounts for 10wt%. The positive electrode surface loading is 5mg / cm 2 The diaphragm is a PP diaphragm coated on both sides with NASICON particles, and the coating thickness on one side is 2μm.

[0065] The polymerization precursor electrolyte consists of vinylene carbonate (8.1 wt%), pentaerythritol tetraacrylate (1.7 wt%), NaClO4 (8.1 wt%), ethylene carbonate (44.0 wt%), diethyl carbonate (35.7 wt%), fluoroethylene carbonate (1.9 wt%), and AIBN (0.5 wt%). After injection, the battery is packaged, kept at 60°C for 16 hours, and then cooled to room temperature to complete the solid-state battery preparation.

[0066] Test conditions: operating voltage range 2.8-4.2V, cycle 200 times at 0.33C rate, Figure 3 This is the cycle performance curve of Example 2 of the present invention. Testing shows that even with the high-voltage electrode Na3(VOPO4)2F, the solid-state battery still maintains good cycle performance, with no significant capacity decay observed after 200 cycles. This demonstrates that the in-situ polymerized solid-state organic-inorganic composite electrolyte of the present invention has strong resistance to electrochemical oxidation and few interfacial side reactions.

[0067] Example 3

[0068] This embodiment uses NaNi 2 / 9 Cu 1 / 9 Fe 1 / 3 Mn 1 / 3 O2 is the positive electrode material and hard carbon is the negative electrode material. The active material accounts for 90wt% of the pole piece, the conductive additive SuperP accounts for 5wt%, and the binder polyvinylidene fluoride (PVDF) accounts for 5wt%. The positive electrode surface loading is 11mg / cm 2 , the negative electrode surface loading is 6.2 mg / cm 2 The separator uses a PP separator coated on one side with NASICON particles. The coating thickness on one side is 2μm, and the coating side faces the negative electrode side.

[0069] The polymerization precursor electrolyte consists of ethylene carbonate (5.8 wt%), pentaerythritol tetraacrylate (1.7 wt%), NaClO4 (8.3 wt%), ethylene carbonate (45.2 wt%), diethyl carbonate (36.6 wt%), fluoroethylene carbonate (1.9 wt%), and AIBN (0.5 wt%). After injection, the battery is packaged, kept at 60°C for 16 hours, and then cooled to room temperature to complete the solid-state battery preparation.

[0070] Test conditions: working voltage range 1.5-4V, cycle 100 times at 0.33C rate, pass Figure 4 It can be seen that the capacity retention rate of Example 3 reaches 70.4%.

[0071] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An in-situ polymerized solid-state organic-inorganic composite electrolyte, characterized in that: The in-situ polymerized solid organic-inorganic composite electrolyte is: the inorganic solid electrolyte particle coating on the diaphragm and the in-situ polymerized precursor electrolyte are mixed at 40 o C-80 o C to initiate polymerization; The inorganic solid electrolyte material constituting the inorganic solid electrolyte particle coating comprises one or more of the fast ion conductors NASICON, Na-β''-Al2O3 or Na3PS4; The in-situ polymerization precursor electrolyte comprises: polymerization monomers, cross-linking agents, sodium salts, solvents, additives and free radical initiators; The contact angle between the inorganic solid electrolyte particle coating on the diaphragm and the solid-liquid interface of the in-situ polymerization precursor electrolyte is 0 o ~10 o ; The polymerizable monomers include: one or more of vinylene carbonate VC, vinyl ethylene carbonate VEC, and methyl methacrylate MMA; The cross-linking agent includes: trimethylolpropane triacrylate and / or pentaerythritol tetraacrylate; The sodium salt includes one or more of NaPF6, NaClO4, NaTFSI, NaFSI, NaBF4, and NaDFOB; The solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether; The additives include: one or more of fluoroethylene carbonate and vinyl sulfate; The free radical initiator includes: azobisisobutyronitrile and / or dibenzoyl oxide; The sum of the mass of the polymerizable monomer and the cross-linking agent accounts for 1%-90% of the total mass of the in situ polymerization precursor electrolyte, the mass of the sodium salt accounts for 3%-60% of the total mass of the in situ polymerization precursor electrolyte, the mass of the solvent accounts for 0-95% of the total mass of the in situ polymerization precursor electrolyte, the mass of the additive accounts for 0-10% of the total mass of the in situ polymerization precursor electrolyte, and the mass of the free radical initiator accounts for 0.5%-3% of the total mass of the in situ polymerization precursor electrolyte; The inorganic solid electrolyte particle coating is a double-sided coating or a single-sided coating on the diaphragm, and the coating thickness on each side is 0.5-10 μm; the base film of the diaphragm is a polypropylene PP single-layer film or a polyethylene PE single-layer film or a PP / PE / PP multi-layer composite microporous film.

2. A method for preparing the in-situ polymerization solid-state organic-inorganic composite electrolyte according to claim 1, characterized in that: The preparation method comprises: The polymerization monomer, cross-linking agent, sodium salt, solvent, additive and free radical initiator are fully mixed in advance to form an in-situ polymerization precursor electrolyte, which is then injected into a battery equipped with a separator coated with inorganic solid electrolyte particles. o C-80 o C for 6-24 hours to initiate polymerization, so that the in-situ polymerization precursor electrolyte and the inorganic solid electrolyte are in-situ solidified on the diaphragm inside the battery to form the in-situ polymerization solidified organic-inorganic composite electrolyte; Wherein, the inorganic solid electrolyte material includes: one or more of the fast ion conductor NASICON, Na-β''-Al2O3 or Na3PS4; The contact angle range of the inorganic solid electrolyte particle coating on the diaphragm and the solid-liquid interface of the in-situ polymerization precursor electrolyte is 0 o ~10 o .

3. The preparation method according to claim 2, characterized in that The polymerizable monomers include one or more of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and methyl methacrylate (MMA); The cross-linking agent includes: trimethylolpropane triacrylate and / or pentaerythritol tetraacrylate; The sodium salt includes one or more of NaPF6, NaClO4, NaTFSI, NaFSI, NaBF4, and NaDFOB; The solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether; The additives include: one or more of fluoroethylene carbonate and vinyl sulfate; The free radical initiator includes: azobisisobutyronitrile and / or dibenzoyl oxide; Among them, the sum of the mass of the polymerization monomer and the cross-linking agent accounts for 1%-90% of the total mass of the in situ polymerization precursor electrolyte, the mass of the sodium salt accounts for 3%-60% of the total mass of the in situ polymerization precursor electrolyte, the mass of the solvent accounts for 0-95% of the total mass of the in situ polymerization precursor electrolyte, the mass of the additive accounts for 0-10% of the total mass of the in situ polymerization precursor electrolyte, and the mass of the free radical initiator accounts for 0.5%-3% of the total mass of the in situ polymerization precursor electrolyte.

4. The preparation method according to claim 3, characterized in that The inorganic solid electrolyte particle coating is a double-sided coating or a single-sided coating on the diaphragm, and the coating thickness on each side is 0.5-10 μm; the base film of the diaphragm is a polypropylene PP single-layer film or a polyethylene PE single-layer film or a PP / PE / PP multi-layer composite microporous film.

5. A sodium ion battery, characterized in that: The sodium ion battery comprises the in-situ polymerized solid-state organic-inorganic composite electrolyte according to claim 1.

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