PEO composite negative pole piece as well as preparation method and application thereof

Abstract

The invention relates to a PEO composite negative pole piece as well as a preparation method and application thereof. The PEO composite negative pole piece comprises a current collector and a negative composite material attached to one side of the current collector, the negative electrode composite material comprises a negative electrode active material and PEO wrapped on the surface and in gaps of the negative electrode active material; pEO provides a sodium ion transmission channel; pEO accounts for 1%-30% of the total mass of the negative electrode composite material; the mass of the negative electrode active material accounts for 50-99% of the total mass of the negative electrode composite material; the PEO composite negative pole piece is used in the all-solid-state sodium ion battery; in the circulation process of the all-solid-state sodium ion battery, groups on the molecular chain segment of the PEO adsorb and desorb sodium ions, a sodium ion transmission channel is formed in the PEO composite negative electrode piece, and the sodium ion transmission rate is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of all-solid-state sodium ion battery materials, and in particular to a PEO composite negative electrode sheet and a preparation method and application thereof. Background Art

[0002] With the continuous development of modern science and technology, the vigorous promotion of national policies, and the advocacy of global decarbonization, lithium-ion battery technology has become more mature. New energy technologies are booming, and their application scope is constantly expanding, covering various fields from electric vehicles to large-scale energy storage grids. However, the rapid growth of lithium consumption and the shortage of lithium resources form a contradictory opposite, which has triggered people's thinking about the utilization rate of lithium resources and the exposure of problems such as the inevitable rise in lithium costs. Therefore, people have set their sights on sodium resources that can replace lithium resources. Because sodium ions have similar chemical properties to lithium ions, they were developed and researched together with lithium-ion batteries in the early days. In addition, sodium resources are abundant in the world, and sodium-ion batteries have been proposed again.

[0003] Liquid sodium-ion batteries have the same disadvantages as liquid lithium-ion batteries: dendrites are prone to pierce the battery during battery cycling, and liquid electrolytes are flammable and explosive when used. In order to avoid these problems, researchers have proposed the concept of solid-state sodium-ion batteries. Solid electrolytes with certain mechanical strength can inhibit the growth of sodium dendrites and avoid the inherent shortcomings of liquid electrolytes, which has extremely high research significance in battery applications.

[0004] All-solid-state sodium-ion batteries (ASSSB) are crucial to improving the safety of sodium-ion battery industrialization. In recent years, researchers have begun to conduct related research, with the main research areas focusing on improving the ionic conductivity and electronic conductivity of solid electrolytes and solving the problem of poor interface contact with electrode materials. In terms of reducing the interface contact between electrode materials and solid electrolytes, most solutions are to add an interlayer between the solid electrolyte and the positive and negative electrodes to modify the interface and reduce the interface impedance.

[0005] Electrode materials also play a vital role in the application of all-solid-state sodium-ion batteries, especially the negative electrode materials of all-solid-state sodium-ion batteries, which have rarely been studied. Currently, most of the materials used on the negative electrode side of all-solid-state sodium batteries are sodium alloys or metallic sodium, but sodium metal has safety risks, which limits its large-scale application in sodium-ion batteries.

[0006] At present, there are very few studies on other negative electrodes of solid-state sodium-ion batteries. In solid-state lithium batteries, there are a lot of studies on using silicon thin film negative electrodes to match sulfide solid electrolytes, and using polyacrylonitrile (PAN) doped with tin (Sn) active materials to prepare composite negative electrodes to match sulfide solid electrolytes. However, sulfide solid electrolytes have extremely strong interfacial side reactions, so the negative electrodes used are usually doped with a large amount of solid electrolytes and binders, and the proportion of active materials is low (14%-70%). This makes the solid-state sodium-ion battery using this negative electrode have the problem of low specific energy, and the doped sulfide solid electrolyte has poor air stability, which also has certain disadvantages in large-scale preparation in the future.

[0007] Hard carbon anodes have long been proven to have high sodium storage capacity (200mAh / g-400mAh / g) in sodium-ion batteries and are widely used in various types of sodium-ion batteries. As a mature anode material for sodium-ion batteries, there are also a few studies on the use of composite hard carbon as anode in all-solid-state sodium-ion batteries. The modification measures usually include adding a high proportion of inorganic solid electrolytes to hard carbon to improve the ionic conductivity of sodium ions in the hard carbon anode, but this will greatly reduce the energy density of sodium-ion batteries.

[0008] PEO (polyethylene oxide) has non-shared electron pairs of ether oxygen and has a strong affinity for hydrogen bonds. It can form complexes with many organic low molecular weight compounds, polymers and certain inorganic electrolytes. Studies have shown that it can be used to modify the negative electrode of all-solid-state sodium ion batteries to solve the above problems. Summary of the invention

[0009] The embodiment of the present invention provides a hard carbon PEO composite negative electrode plate and its preparation method and application, the purpose of which is to solve the problem of improving the interface side reaction of the existing solid-state sodium battery, adding a traditional PEO polymer solid electrolyte to the negative electrode active material, reducing the negative electrode interface defects, and improving the ionic conductivity while also reducing the battery energy density.

[0010] The present invention adds PEO during the preparation of the PEO composite negative electrode sheet, so that the surface of the negative electrode active material is wrapped by PEO, and sodium ions are transported through PEO to construct a transmission channel for sodium ions in the negative electrode, thereby relatively improving the ion transmission efficiency of the negative electrode material; at the same time, the surface defects of the negative electrode active material are reduced, and the side reactions of the negative electrode active material and the solid electrolyte, especially the surface defects of hard carbon, and the side reactions of hard carbon and the solid electrolyte are alleviated to a certain extent. The PEO composite negative electrode sheet is applied to an all-solid-state sodium ion battery, which can improve the first-cycle coulomb efficiency of the all-solid-state sodium ion battery and the stable reversible cycle of the all-solid-state sodium ion battery.

[0011] The present invention is different from the traditional composite electrode material made by adding a large amount of inorganic electrolyte. The proportion of the introduced polymer solid electrolyte PEO additive is low, which increases the proportion of active substances in the composite negative electrode material, while improving the first cycle coulomb efficiency of the battery, and also ensures the specific energy density of the negative electrode material. In addition, the amount of PEO added in the present invention is safer than that of some inorganic solid electrolytes (such as sulfide solid electrolytes and halide solid electrolytes), and has a wider application prospect.

[0012] To this end, in a first aspect, an embodiment of the present invention provides a PEO composite negative electrode plate, wherein the PEO composite negative electrode plate comprises: a current collector, and a negative electrode composite material attached to one side of the current collector.

[0013] The negative electrode composite material comprises: a negative electrode active material, a binder, and polyethylene oxide PEO wrapped on the surface and in the gaps of the negative electrode active material.

[0014] The PEO has a molecular chain segment for adsorbing sodium ions; the molecular chain segment forms a sodium ion transmission channel on the surface of the negative electrode active material; and the molecular weight of the PEO ranges from 20W to 100W.

[0015] The mass of the PEO accounts for 1%-30% of the total mass of the negative electrode composite material.

[0016] The mass of the negative electrode active material accounts for 50%-99% of the total mass of the negative electrode composite material.

[0017] The PEO composite negative electrode plate is used in an all-solid-state sodium ion battery; during the cycle of the all-solid-state sodium ion battery, the sodium ions repeat the adsorption and desorption process with the groups of the PEO along the molecular chain segments, so that the sodium ions are transported on the molecular chain segments.

[0018] Preferably, the negative electrode active material includes: one or more of carbon-based materials, silicon-based materials, titanium-based materials, metal oxide negative electrode materials, and alloy materials.

[0019] The current collector includes copper foil or aluminum foil.

[0020] Further preferably, the carbon-based material is an amorphous carbon material, including hard carbon or soft carbon; and the silicon-based material includes silicon-oxygen material and / or silicon-carbon composite material.

[0021] The titanium-based materials include: Na2Ti3O7, Li4Ti5O 12 、Na 0.66 [L i 0.22 T i 0.78 ]O2、Na 0.6 [Cr0.6 Ti 0.4 ]One or more of Na2T i OPO4, Na2T i2(PO4)3.

[0022] Preferably, the binder comprises: one or more of polyvinylidene fluoride, polyvinyl alcohol, polyacrylamide, sodium hydroxymethyl cellulose, polyacrylic acid, polytetrafluoroethylene, and sodium alginate; the binder accounts for 0-10% of the total mass percentage of the negative electrode composite material.

[0023] Preferably, the negative electrode composite material further comprises sodium salt; the sodium salt comprises: NaFS I and / or NaTFS I; the sodium salt accounts for 0-20% of the total mass percentage of the negative electrode composite material.

[0024] In a second aspect, an embodiment of the present invention provides a method for preparing the PEO composite negative electrode sheet described in the first aspect, and the preparation method comprises:

[0025] The negative electrode active material, PEO, sodium salt and binder are added to the dispersant and stirred evenly to obtain a negative electrode slurry.

[0026] The negative electrode slurry is coated on one side of the current collector, cut or sliced ​​after drying, and then vacuum dried to obtain a PEO composite negative electrode sheet containing the negative electrode composite material.

[0027] Preferably, the negative electrode active material includes: one or more of carbon-based materials, silicon-based materials, titanium-based materials, metal oxide negative electrode materials, and alloy materials; wherein, the carbon-based material is an amorphous carbon material, including hard carbon or soft carbon; the silicon-based material includes silicon-oxygen materials and / or silicon-carbon composite materials; the titanium-based material includes: Na2Ti3O7, Li4Ti5O 12 、Na 0.66 [L i 0.22 T i 0.78 ]O2、Na 0.6 [Cr 0.6 T i 0.4 ]One or more of Na2T i OPO4, Na2T i2(PO4)3.

[0028] The PEO includes a molecular weight range of 20W-100W.

[0029] The binder includes: one or more of polyvinylidene fluoride, polyvinyl alcohol, polyacrylamide, sodium hydroxyethyl cellulose, polyacrylamide, and polytetrafluoroethylene.

[0030] The sodium salt includes: NaFS I and / or NaTFS I.

[0031] The mass ratio of the negative electrode active material, PEO, sodium salt and binder is [50-90]: [1-30]: [0-20]: [0-10].

[0032] The dispersant includes deionized water or N-methylpyrrolidone.

[0033] The current collector includes copper foil or aluminum foil.

[0034] Preferably, the drying temperature is 80° C.-100° C., and the drying time is 40 minutes-8 hours.

[0035] The vacuum drying temperature is 120° C., and the vacuum drying time is 10 hours to 15 hours.

[0036] In a third aspect, an embodiment of the present invention provides an all-solid-state sodium ion battery, comprising a positive electrode plate, a solid electrolyte membrane and the PEO composite negative electrode plate described in the first aspect above.

[0037] The solid electrolyte membrane is prepared by one or more of an inorganic solid electrolyte, a polymer solid electrolyte, and an inorganic-organic composite solid electrolyte.

[0038] Preferably, the inorganic solid electrolyte includes: one or more of halide-based, oxide-based solid electrolytes and modified derivatives thereof, LLZO and modified derivatives thereof, LATP and modified derivatives thereof, LLTO and modified derivatives thereof, sulfide-based solid electrolytes, boron-based solid electrolytes and modified derivatives thereof.

[0039] The polymer solid electrolyte includes one or more of polyethylene oxide and its modified derivatives, polycarbonate and its derivatives, polyacrylonitrile and its derivatives, polyvinyl alcohol and its derivatives, polyvinyl pyrrolidone and its derivatives, polyvinylidene fluoride and its derivatives, polypropylene oxide and its derivatives, polymethyl methacrylate and its derivatives.

[0040] The inorganic-organic composite solid electrolyte is a composite of the inorganic solid electrolyte and the organic solid electrolyte.

[0041] The positive electrode active material of the positive electrode plate includes any one of phosphates, ternary materials, vanadium oxides, vanadates, transition metal oxides, Prussian blue compounds, and polyanion compounds.

[0042] The embodiment of the present invention provides a PEO composite negative electrode plate and a preparation method and application thereof. By adding PEO during the preparation process of the composite negative electrode plate, the surface of the negative electrode active material is coated with PEO, the gaps between the negative electrode active material particles are filled with PEO, and sodium ions are transmitted through the molecular chain segments of PEO to construct a transmission channel for sodium ions in the negative electrode plate, thereby relatively improving the ion transmission efficiency of the negative electrode material. The PEO composite negative electrode plate is applied to an all-solid-state sodium ion battery, which can ensure the first-cycle coulomb efficiency of the all-solid-state sodium ion battery and the stable reversible cycle of the all-solid-state sodium ion battery.

[0043] The present invention is different from the traditional composite electrode material made by adding a large amount of inorganic electrolyte. The introduced PEO addition ratio is low, which increases the proportion of active substances in the composite negative electrode material. While ensuring the first-cycle coulomb efficiency of the battery, it also ensures the specific energy density of the negative electrode material.

[0044] The invention provides a method for preparing a PEO composite negative electrode sheet, which is simple to operate, low in cost, and applicable to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Schematic diagram of sodium ion transmission in the PEO composite negative electrode plate provided in an embodiment of the present invention.

[0046] Figure 2 A flow chart of a method for preparing a PEO composite negative electrode sheet provided in an embodiment of the present invention.

[0047] Figure 3 Raman characterization diagram of the PEO composite negative electrode sheet provided in Example 1 of the present invention and the negative electrode sheet without adding PEO in Comparative Example 1.

[0048] Figure 4 This is a first cycle charge and discharge curve diagram of an all-solid-state sodium metal battery assembled with a PEO composite negative electrode plate provided in Example 1 of the present invention.

[0049] Figure 5 This is a first cycle charge and discharge curve diagram of an all-solid-state sodium metal battery assembled with a hard carbon negative electrode sheet provided in Comparative Example 1 of the present invention.

[0050] Figure 6 This is a first cycle charge and discharge curve diagram of an all-solid-state sodium metal battery assembled with a PEO composite negative electrode plate provided in Example 2 of the present invention.

[0051] Figure 7 This is a first cycle charge and discharge curve diagram of an all-solid-state sodium metal battery assembled with a PEO composite negative electrode plate provided in Example 3 of the present invention.

[0052] Figure 8The charge and discharge curves of the first and fifth cycles of the all-solid-state sodium metal battery assembled with the PEO composite negative electrode plate provided in Example 4 of the present invention.

[0053] Fig. 9 This is a first cycle charge and discharge curve diagram of an all-solid-state sodium ion battery assembled with a PEO composite negative electrode plate provided in Example 4 of the present invention.

[0054] Fig.10 The cycle efficiency and specific capacity curve of the all-solid-state sodium ion battery single-layer soft-pack battery assembled with the PEO composite negative electrode plate provided in Example 4 of the present invention.

[0055] Fig.11 This is a first cycle charge and discharge curve diagram of an all-solid-state sodium metal battery assembled with a PEO composite negative electrode plate provided in Example 5 of the present invention.

[0056] Fig.12 The charge and discharge curves of the first and fifth cycles of the all-solid-state sodium metal battery assembled with the PEO composite negative electrode plate provided in Example 6 of the present invention.

[0057] Fig.13 This is a first cycle charge and discharge curve diagram of an all-solid-state sodium ion battery assembled with a PEO composite negative electrode plate provided in Example 7 of the present invention. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0060] The embodiment of the present invention provides a PEO composite negative electrode plate, comprising: a current collector, and a negative electrode composite material attached to one side of the current collector.

[0061] Wherein, the current collector includes copper foil or aluminum foil.

[0062] The negative electrode composite material includes: a negative electrode active material, a binder, and a polymer wrapped on the surface and in the gaps of the negative electrode active material.

[0063] The molecular weight range of PEO selected in the embodiment of the present invention is between 20W-100W, preferably 60W; the mass of PEO accounts for 1%-30% of the total mass of the negative electrode composite material, preferably 5%-15%, and more preferably 5%; the mass of the negative electrode active material accounts for 50%-99% of the total mass of the negative electrode composite material, preferably 85%-90%, and more preferably 85%.

[0064] The negative electrode active material includes: one or more of carbon-based materials, silicon-based materials, titanium-based materials, metal oxide negative electrode materials, and alloy materials.

[0065] Among them, the carbon-based material is an amorphous carbon material, including hard carbon or soft carbon; the precursors of the amorphous carbon material include but are not limited to: one or more of biomass precursors, synthetic resin precursors, and asphalt precursors; among them, the biomass precursors include but are not limited to: one or more of coconut shells, straws, walnut shells, sugar, and starch; the synthetic resin precursors specifically include but are not limited to: phenolic resins and / or epoxy resins.

[0066] Silicon-based materials include, but are not limited to, silicon-oxygen materials and / or silicon-carbon composite materials.

[0067] Titanium-based materials include but are not limited to: Na2Ti3O7, Li4Ti5O 12 、Na 0.66 [L i 0.22 T i 0.78 ]O2、Na 0.6 [Cr 0.6 T i 0.4 ]One or more of Na2T i OPO4, Na2T i2(PO4)3.

[0068] The binder includes: one or more of polyvinylidene fluoride, polyvinyl alcohol, polyacrylamide, sodium hydroxymethyl cellulose, polyacrylamide, and polytetrafluoroethylene; the binder accounts for 0-10% of the total mass percentage of the negative electrode composite material, preferably 5%.

[0069] The molecular chain segments of PEO in the above-mentioned negative electrode composite material provided by an embodiment of the present invention have groups that can adsorb sodium ions, such as ether bonds (-COC-) and hydroxyl groups (-OH). These groups can act on the surface of the negative electrode active material and fill the gaps in the active material to provide channels for the transmission of sodium ions.

[0070] PEO composite negative electrode is used in all-solid-state sodium ion batteries. During the cycle of all-solid-state sodium ion batteries, sodium ions and groups on PEO molecular segments repeatedly adsorb and desorb, thereby allowing sodium ions to be transported on PEO molecular segments. The groups on PEO molecular segments can interact with the groups on the hard carbon surface, such as the hydroxyl group (-OH) on the surface of hard carbon particles and the ether bond of PEO.

[0071] (-COC-) forms hydrogen bond interactions, and the hydroxyl groups (-OH) on the surface of the hard carbon particles interact with the hydroxyl groups (-OH) of PEO to form hydrogen bonds. This allows the sodium ions that are far away from the hard carbon particles to get rid of the disadvantages of solid-solid interface transmission, and are transmitted along the molecular chain segments of PEO to quickly reach the surface of the hard carbon particles, thereby achieving the deintercalation of distant sodium ions on the hard carbon surface, thereby improving the ion transmission efficiency and further improving the first-week coulomb efficiency of the battery.

[0072] The PEO of the present invention is coated on the surface of the negative electrode active material and filled in the gaps of the negative electrode active material, so that the negative electrode active material and the solid electrolyte membrane of the all-solid-state sodium ion battery will not be in direct contact. During the initial cycle of the all-solid-state sodium ion battery, the interface side reaction between the negative electrode active material and the solid electrolyte in the solid electrolyte membrane is reduced, thereby ensuring certain electrochemical performance of the battery.

[0073] In addition, there is a solid-solid interface contact between the negative electrode composite material and the solid electrolyte membrane, and the interface impedance is large. As the all-solid-state sodium ion battery cycles at a certain temperature, the PEO in the negative electrode composite material begins to transform from a glassy state to a viscoelastic state, so that the gaps in the solid-solid interface between the negative electrode composite material and the solid electrolyte membrane are fully filled with PEO, thereby reducing the interface impedance, reducing the internal resistance of the battery, and improving the first-cycle coulomb efficiency and first-cycle reversible capacity of the battery.

[0074] In a preferred embodiment, the negative electrode composite material further includes sodium salt; the sodium salt includes sodium bis(fluorosulfonyl)imide (NaFSI) and / or sodium bis(trifluoromethylsulfonyl)imide (NaTFSI); the sodium salt accounts for 0-20% of the total mass percentage of the negative electrode composite material, preferably 5%.

[0075] Schematic diagram of the sodium ion transmission in the sodium ion transmission channel formed by the molecular chain segments of PEO in the PEO composite negative electrode sheet (taking hard carbon as the negative electrode active material as an example), as shown in Figure 1 As shown, Figure 1 (a) shows the process of sodium ion transmission on the PEO molecular chain segment. It can be seen that the sodium ions in the PEO composite negative electrode plate are transferred within the chain or between chains at different positions and different segments of the PEO molecular chain through the adsorption and desorption process with the PEO groups on the PEO molecular chain segment, thereby achieving the purpose of sodium ion transmission.

[0076] pass Figure 1 (b) It can be seen that the surface and gaps of the hard carbon particles (HC) in the PEO composite negative electrode are wrapped and filled with PEO, and the hydroxyl groups (-OH) on the surface of the hard carbon particles interact with the ether bonds (-COC-) to form hydrogen bonds, and the sulfinyl groups (-S(O)-) interact with the hydroxyl groups (-OH) on the surface of the hard carbon particles. This allows sodium ions that are far away from the hard carbon particles to be quickly transported along the molecular chain segments of PEO to reach the surface of the hard carbon particles, thereby achieving the deintercalation of sodium ions that are far away from the hard carbon particles on the hard carbon surface, thereby improving the transmission efficiency of sodium ions, improving the coulombic efficiency of the battery, and ensuring the first-cycle reversible specific capacity of the hard carbon negative electrode. It should be noted that Figure 1 Lithium salt is added to the negative electrode composite material exemplified in the example, so the lithium salt reacts with PEO to form a sulfinyl group (-S(O)-).

[0077] The present invention provides a method for preparing the above-mentioned PEO composite negative electrode sheet, such as Figure 2 As shown, the specific steps include the following steps.

[0078] Step 110, adding the negative electrode active material, PEO, sodium salt and binder into the dispersant, stirring evenly, to obtain a negative electrode slurry.

[0079] Wherein, the molecular weight of polyethylene oxide PEO ranges from 20W to 100W, preferably 60W;

[0080] The negative electrode active material includes: one or more of carbon-based materials, silicon-based materials, titanium-based materials, metal oxide negative electrode materials, and alloy materials.

[0081] The carbon-based material is an amorphous carbon material, including hard carbon and soft carbon; the precursors of the amorphous carbon material include but are not limited to: one or more of biomass precursors, synthetic resin precursors, and asphalt precursors; wherein the biomass precursors include but are not limited to: one or more of coconut shells, straws, walnut shells, sugar, and starch; the synthetic resin precursors specifically include but are not limited to: phenolic resins and / or epoxy resins.

[0082] Silicon-based materials include silicon-oxygen materials and / or silicon-carbon composite materials; titanium-based materials include but are not limited to: Na2Ti3O7, Li4Ti5O 12 、Na 0.66 [L i 0.22 T i 0.78 ]O2、Na 0.6 [Cr 0.6 T i 0.4]One or more of Na2T i OPO4, Na2T i2(PO4)3.

[0083] The binder includes: one or more of polyvinylidene fluoride, polyvinyl alcohol, polyacrylamide, sodium hydroxyethyl cellulose, polyacrylamide, and polytetrafluoroethylene.

[0084] Sodium salts include, but are not limited to, NaFS I and / or NaTFS I.

[0085] The mass ratio of the negative electrode active material, PEO, sodium salt and binder is [50-90]: [1-30]:

[0086] [0-20]:[0-10].

[0087] The dispersant includes deionized water or N-methylpyrrolidone; the solid content in the negative electrode slurry is 45wt%-60wt%.

[0088] The stirring in this step can be carried out using conventional equipment to ensure that the material is evenly dispersed in the dispersant.

[0089] Step 120, coating the negative electrode slurry on one side of the current collector, cutting or slicing after drying, and then vacuum drying to obtain a PEO composite negative electrode sheet containing the negative electrode composite material.

[0090] Wherein, the current collector includes copper foil or aluminum foil.

[0091] The drying temperature is between 80°C and 100°C, and the drying time is 40 minutes to 8 hours. The purpose of drying is to facilitate cutting or cutting.

[0092] The temperature of vacuum drying is 120° C., and the time of vacuum drying is 10 to 15 hours. The purpose of vacuum drying is to completely remove the dispersant.

[0093] The coating method in this step is a conventional known method, and the coating thickness is 10 μm-100 μm.

[0094] The diameter of the pole piece cut or shot is 8mm or 12mm round.

[0095] In the present invention, the negative electrode active material of the PEO composite negative electrode plate is wrapped by PEO (polyethylene oxide), and the gaps between the negative electrode active materials are also filled with PEO. The molecular chain segments in the non-crystalline region of PEO flow, and the violent movement of the chain segments at a certain temperature and under the action of an electric field can conduct the directional transmission of sodium ions.

[0096] In the present invention, the PEO composite negative electrode plate also includes sodium salt. The alkali metal ions in the sodium salt form weak coordination with the polymer polar groups. The coordination bond strength is relatively weak, easy to form and easy to break. When the temperature is above the glass transition temperature of PEO, under the action of the electric field, the polymer molecules vibrate, and the sodium ions and the molecular chain segments of PEO are continuously adsorbed and desorbed, forming a transmission channel for the sodium ions. In addition, the sodium ion transmission path is complex, and intra-segment hopping transmission or chain-to-chain hopping transmission can be performed, which greatly improves the transmission efficiency.

[0097] The molecular weight range of PEO in the present invention is between 20W-100W, and can be any value within the above range, for example: 20W, 25W, 30W, 35W, 40W, 45W, 50W, 55W, 60W, 65W, 70W, 75W, 80W, 85W, 90W, 95W, 100W, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable. The molecular weight of PEO in the present invention is preferably 60W. If PEO with a molecular weight less than 20W is selected, the molecular chain segment is shorter, and its end group activity is poor, which is not conducive to the formation of a sodium ion transmission channel; and if PEO with a molecular weight greater than 100W is selected, the molecular chain segment is longer, which will affect the sodium ion transmission efficiency.

[0098] The mass of PEO in the present invention accounts for 1%-30% of the total mass of the negative electrode composite material, which can be any value within the above range, for example: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, etc., but are not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable. The mass of PEO in the present invention accounts for 5%-15% of the total mass of the negative electrode composite material, and more preferably 5%. The mass of the sodium salt in the present invention is 0%-20%, and more preferably 5%.

[0099] The mass of the sodium salt in the present invention accounts for 0%-20% of the total mass of the negative electrode composite material, which can be any value within the above range, for example: 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable. The mass of the sodium salt in the present invention accounts for the total mass of the negative electrode composite material. The percentage is preferably 5%.

[0100] The PEO composite negative electrode sheets prepared by the above two methods in the embodiments of the present invention can be used in all-solid-state sodium ion batteries.

[0101] The all-solid-state sodium ion battery also includes a solid electrolyte membrane and a positive electrode plate.

[0102] Among them, the positive electrode sheet is prepared by the existing conventional method. The specific process is: the positive electrode active material, other additive materials, and solvent are evenly mixed in proportion to form a positive electrode slurry, and then the positive electrode slurry is coated on one side of the current collector, and the positive electrode sheet is obtained after drying.

[0103] The positive electrode active material includes, but is not limited to, any one of phosphates, ternary materials, vanadium oxides, vanadates, transition metal oxides, Prussian blue compounds, and polyanion compounds.

[0104] The current collector for preparing the positive electrode sheet is copper foil or aluminum foil.

[0105] Other additive materials include conductive materials and binders.

[0106] Specifically, the conductive material includes: one or more of graphite conductive agent, conductive carbon black, and graphene; the graphite conductive agent includes: one or more of KS-6, KS-15, SFG-6, and SFG-15; the conductive carbon black includes: one or more of acetylene black, Super P, Super S, 350G, carbon fiber VGCF, carbon nanotubes CNTs, Ketjen black, and activated carbon.

[0107] The binder includes one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, carboxymethyl cellulose, sodium carboxymethyl cellulose, polymethyl methacrylate, polyacrylic acid, polyacrylonitrile, styrene-butadiene rubber, polyvinyl alcohol, polytetrafluoroethylene, polyacrylamide, polyvinyl acetate or polyurethane.

[0108] In an optional scheme, the slurry preparation process of the positive electrode plate can also be the preparation process of the PEO composite negative electrode plate provided in the embodiment of the present invention. PEO is added during the preparation of the positive electrode slurry, so that the surface and gaps of the positive electrode active material are coated with PEO, and the molecular chain segments of PEO form sodium ion transmission channels on the surface of the positive electrode active material.

[0109] The solid electrolyte membrane of the above-mentioned all-solid-state sodium ion battery is prepared by one or more of an inorganic solid electrolyte, a polymer solid electrolyte, and an inorganic-organic composite solid electrolyte.

[0110] Among them, the inorganic solid electrolytes include: one or more of halide-based, oxide-based solid electrolytes and their modified derivatives, LLZO and its modified derivatives, LATP and its modified derivatives, LLTO and its modified derivatives, sulfide-based solid electrolytes, boron-based solid electrolytes and their modified derivatives.

[0111] The polymer solid electrolyte includes one or more of polyethylene oxide and its modified derivatives, polycarbonate and its derivatives, polyacrylonitrile and its derivatives, polyvinyl alcohol and its derivatives, polyvinyl pyrrolidone and its derivatives, polyvinylidene fluoride and its derivatives, polypropylene oxide and its derivatives, polymethyl methacrylate and its derivatives.

[0112] Inorganic-organic composite solid electrolyte is a composite of inorganic solid electrolyte and organic solid electrolyte.

[0113] Since the all-solid-state sodium ion battery uses the PEO composite negative electrode plate provided by the embodiment of the present invention, and since the surface of the negative electrode active material in the PEO composite negative electrode plate is coated with PEO, the sodium ions are repeatedly adsorbed and desorbed by the groups on the molecular chain segments of PEO, so that the sodium ions move along the molecular chain segments of PEO, and a transmission channel for sodium ions in the negative electrode is constructed, thereby improving the ion transmission efficiency of the negative electrode material, and can ensure the first-cycle coulomb efficiency of the all-solid-state sodium ion battery and the stable reversible cycle of the all-solid-state sodium ion battery.

[0114] The PEO composite negative electrode plate of the present invention can still meet the normal cycle effect of the all-solid-state sodium ion battery even without adding sodium salt, that is, the proportion of sodium salt is 0%, because the molecular chain segments of PEO provide a transmission channel for sodium ions in the negative electrode.

[0115] In order to better understand the technical solution provided by the present invention, the preparation process and characteristics of the PEO composite negative electrode sheet of the present invention are respectively described below with multiple specific examples.

[0116] The hard carbon used in the following examples and comparative examples was purchased from Kuraray Co., Ltd. If no specific experimental steps or conditions are specified in each example or comparative example, the conventional experimental steps or conditions described in the literature in the field can be used. The materials, reagents or instruments used without indicating the manufacturer are all conventional products purchased from the market.

[0117] Example 1

[0118] This embodiment provides a preparation process and performance test of a PEO composite negative electrode sheet, and the specific preparation process is as follows.

[0119] (1) Take 100 g of 85 wt % hard carbon, 5 wt % PEO (molecular weight 60 W) and 5 wt % CMC, disperse them in deionized water, stir evenly, and obtain a negative electrode slurry with a solid content of 45 wt %; no sodium salt is added in this step.

[0120] (2) The negative electrode slurry was coated on the surface of one side of the current collector copper foil, dried at 80°C for 40 minutes, and then cut into discs with a diameter of 12 mm, and then vacuum dried at 120°C for 24 hours to obtain a PEO composite negative electrode sheet containing a negative electrode composite material. The negative electrode active material surface loading on the PEO composite negative electrode sheet was 1 mg / cm 2 .

[0121] The prepared PEO composite negative electrode sheet was transferred to a vacuum glove box for later use.

[0122] The Raman characterization image of the PEO composite negative electrode prepared in this embodiment is as follows: Figure 3 shown.

[0123] The PEO composite negative electrode sheet prepared in this embodiment was assembled into an all-solid-state sodium metal battery and tested. The specific process is as follows.

[0124] The solid electrolyte membrane of the all-solid-state sodium metal battery of this embodiment is a PEO polymer electrolyte membrane. The preparation process of the solid electrolyte membrane is as follows: PEO (molecular weight Mw is 600000) and NaFS I are dissolved in acetonitrile (EO and Na + The molar ratio of 20:1 was prepared into a 0.05 g / L viscous solution, which was cast into a polytetrafluoroethylene mold and vacuum dried at 55°C for 24 hours to obtain a PEO polymer electrolyte membrane.

[0125] Assembly of all-solid-state sodium metal battery: The PEO composite negative electrode sheet and the PEO polymer electrolyte membrane are matched and assembled into an all-solid-state sodium metal battery by conventional methods.

[0126] Testing of all-solid-state sodium metal batteries: In the 0-2.5V cut-off voltage window, the all-solid-state sodium metal battery can achieve a first-cycle coulombic efficiency (I CE) of 89.44% and a first-cycle reversible capacity of 279.24mAh / g in a cycle test at a current density of 0.1C at a temperature of 70°C.

[0127] The first cycle charge and discharge curve of the all-solid-state sodium metal battery prepared in this embodiment is as follows: Figure 4 shown.

[0128] In order to better illustrate the effect of the embodiment of the present invention, comparative example 1 is compared with embodiment 1.

[0129] Comparative Example 1

[0130] This comparative example provides a preparation process of a hard carbon negative electrode sheet, which is different from Example 1 in that PEO is not added in step (1), and only 100 g of 95 wt% hard carbon and 5 wt% CMC are taken, dispersed in deionized water, and stirred evenly to obtain a negative electrode slurry with a solid content of 45 wt%; the other steps are the same as Example 1.

[0131] The Raman characterization diagram of the hard carbon negative electrode sheet without adding PEO in this comparative example is as follows: Figure 3 As shown, it can be seen that the ID / IG value in the Raman characterization diagram of Comparative Example 1 is higher than the ID / IG value of the negative electrode sheet after adding PEO in Example 1, indicating that the degree of defects of the hard carbon negative electrode sheet in Comparative Example 1 without adding PEO is high.

[0132] The hard carbon negative electrode sheet prepared in this comparative example was assembled into an all-solid-state sodium metal battery and tested. The assembly and testing processes were the same as those in Example 1.

[0133] The first-cycle coulombic efficiency (I CE) of the all-solid-state sodium metal battery assembled in this comparative example was tested to be 87.52%, and the first-cycle reversible capacity was 210.56 mAh / g.

[0134] The first cycle charge and discharge curve of the all-solid-state sodium metal battery prepared in this comparative example is as follows: Figure 5 shown.

[0135] Example 2

[0136] This embodiment provides a preparation process and performance test of a PEO composite negative electrode sheet, and the specific preparation process is as follows.

[0137] (1) Take 100 g of 85 wt % hard carbon, 5 wt % PEO (molecular weight 60 W), 1 wt % NaFS I and 5 wt % CMC, disperse them in deionized water, and stir them evenly to obtain a negative electrode slurry with a solid content of 45 wt %.

[0138] (2) The negative electrode slurry was coated on the surface of one side of the current collector copper foil, dried at 80°C for 40 minutes, and then cut into discs with a diameter of 12 mm, and then vacuum dried at 120°C for 24 hours to obtain a PEO composite negative electrode sheet containing a negative electrode composite material. The negative electrode active material surface loading on the PEO composite negative electrode sheet was 1 mg / cm 2 .

[0139] The prepared PEO composite negative electrode sheet was transferred to a vacuum glove box for later use.

[0140] The PEO composite negative electrode sheet prepared in this embodiment was assembled into an all-solid-state sodium metal battery and tested. The specific process is as follows.

[0141] The solid electrolyte membrane of the all-solid-state sodium metal battery of this embodiment is a PEO polymer electrolyte membrane. The preparation process of the solid electrolyte membrane is as follows: PEO (molecular weight Mw is 600000) and NaFS I are dissolved in acetonitrile (EO and Na + The molar ratio of 20:1 was prepared into a 0.05 g / L viscous solution, which was cast into a polytetrafluoroethylene mold and vacuum dried at 55°C for 24 hours to obtain a PEO polymer electrolyte membrane.

[0142] Assembly of all-solid-state sodium metal battery: The PEO composite negative electrode sheet and the PEO polymer electrolyte membrane are matched and assembled into an all-solid-state sodium metal battery by conventional methods.

[0143] Testing of all-solid-state sodium metal batteries: In the 0-2.5V cut-off voltage window, the all-solid-state sodium metal battery can achieve a first-cycle coulombic efficiency (I CE) of 89.43% and a first-cycle reversible capacity of 281.3mAh / g in a cycle test at a temperature of 70°C and a current density of 0.1C.

[0144] The first cycle charge and discharge curve of the all-solid-state sodium metal battery prepared in this embodiment is as follows: Figure 6 shown.

[0145] Example 3

[0146] This embodiment provides a preparation process and performance test of a PEO composite negative electrode sheet, and the specific preparation process is as follows.

[0147] (1) Take 100 g of 85 wt % hard carbon, 5 wt % PEO (molecular weight 60 W), 2 wt % NaFS I and 5 wt % CMC, disperse them in deionized water, and stir them evenly to obtain a negative electrode slurry with a solid content of 45 wt %.

[0148] (2) The negative electrode slurry was coated on the surface of one side of the current collector copper foil, dried at 80°C for 40 minutes, and then cut into discs with a diameter of 12 mm, and then vacuum dried at 120°C for 24 hours to obtain a PEO composite negative electrode sheet containing a negative electrode composite material. The negative electrode active material surface loading on the PEO composite negative electrode sheet was 1 mg / cm 2 .

[0149] The prepared PEO composite negative electrode sheet was transferred to a vacuum glove box for later use.

[0150] The PEO composite negative electrode sheet prepared in this embodiment was assembled into an all-solid-state sodium metal battery and tested. The specific process is as follows.

[0151] The solid electrolyte membrane of the all-solid-state sodium metal battery of this embodiment is a PEO polymer electrolyte membrane. The preparation process of the solid electrolyte membrane is as follows: PEO (molecular weight Mw is 600000) and NaFS I are dissolved in acetonitrile (EO and Na + The molar ratio of 20:1 was prepared into a 0.05 g / L viscous solution, which was cast into a polytetrafluoroethylene mold and vacuum dried at 55°C for 24 hours to obtain a PEO polymer electrolyte membrane.

[0152] Assembly of all-solid-state sodium metal battery: The PEO composite negative electrode sheet and the PEO polymer electrolyte membrane are matched and assembled into an all-solid-state sodium metal battery by conventional methods.

[0153] Testing of all-solid-state sodium metal batteries: In the 0-2.5V cut-off voltage window, the all-solid-state sodium metal battery can achieve a first-cycle coulombic efficiency (I CE) of 89.57% and a first-cycle reversible capacity of 274.97mAh / g in a cycle test at a current density of 0.1C at a temperature of 70°C.

[0154] The first cycle charge and discharge curve of the all-solid-state sodium metal battery prepared in this embodiment is as follows: Figure 7 shown.

[0155] Example 4

[0156] This embodiment provides a preparation process and performance test of a PEO composite negative electrode sheet, and the specific preparation process is as follows.

[0157] (1) Take 100 g of 85 wt % hard carbon, 5 wt % PEO (molecular weight 60 W), 5 wt % NaFS I and 5 wt % CMC, disperse them in deionized water, and stir them evenly to obtain a negative electrode slurry with a solid content of 45 wt %.

[0158] (2) The negative electrode slurry was coated on the surface of one side of the current collector copper foil, dried at 80°C for 40 minutes, and then cut into discs with a diameter of 12 mm, and then vacuum dried at 120°C for 24 hours to obtain a PEO composite negative electrode sheet containing a negative electrode composite material. The negative electrode active material surface loading on the PEO composite negative electrode sheet was 1 mg / cm 2 .

[0159] The prepared PEO composite negative electrode sheet was transferred to a vacuum glove box for later use.

[0160] The PEO composite negative electrode sheet prepared in this embodiment was assembled into an all-solid-state sodium metal battery and tested. The specific process is as follows.

[0161] The solid electrolyte membrane of the all-solid-state sodium metal battery of this embodiment is a PEO polymer electrolyte membrane. The preparation process of the solid electrolyte membrane is as follows: PEO (molecular weight Mw is 600000) and NaFS I are dissolved in acetonitrile (EO and Na + The molar ratio of 20:1 was prepared into a 0.05 g / L viscous solution, which was cast into a polytetrafluoroethylene mold and vacuum dried at 55°C for 24 hours to obtain a PEO polymer electrolyte membrane.

[0162] Assembly of all-solid-state sodium metal battery: The PEO composite negative electrode sheet and the PEO polymer electrolyte membrane are matched and assembled into an all-solid-state sodium metal battery by conventional methods.

[0163] Testing of all-solid-state sodium metal batteries: In the 0-2.5V cut-off voltage window, the all-solid-state sodium metal battery can achieve a first-cycle coulombic efficiency (I CE) of 89.8% and a first-cycle reversible capacity of 283.9mAh / g in a cycle test at a current density of 0.1C at 70°C.

[0164] The first cycle charge and discharge curve of the all-solid-state sodium metal battery prepared in this embodiment is as follows: Figure 8 shown.

[0165] The PEO composite negative electrode sheet prepared in this embodiment was assembled into an all-solid-state sodium ion battery and tested. The specific process is as follows.

[0166] The solid electrolyte membrane of the all-solid-state sodium ion battery of this embodiment adopts the same PEO polymer electrolyte membrane as the all-solid-state sodium metal battery.

[0167] The positive electrode of the all-solid-state sodium-ion battery adopts a composite phosphate positive electrode. The specific preparation process is as follows: 40 mg of polyethylene oxide ether, 40 mg of NaFSI, 80 mg of conductive agent Super P, 800 uL of polyvinylidene fluoride (PVDF) solution (PVDF is dissolved in NMP solvent with a concentration of 0.05 g / L) and 600 mg of sodium vanadium phosphate are taken, and a uniform solution is formed by degassing and stirring at a high speed of 900 r / min to obtain a positive electrode slurry, which is evenly coated on aluminum foil with a coating thickness of 75 μm, and the electrode is dried in a blast drying oven at 80°C, and then punched into a circular electrode with a diameter of 12 mm, and dried in a vacuum drying oven at 120°C for 12 hours to obtain a composite phosphate positive electrode. It is then transferred to a vacuum glove box for standby use.

[0168] The assembly of the all-solid-state sodium ion battery is a conventional method, wherein the PEO composite negative electrode plate of this embodiment is bonded to one side of the above-mentioned PEO polymer electrolyte membrane, and the prepared composite phosphate positive electrode plate is bonded to the other side of the PEO polymer electrolyte membrane.

[0169] The electrochemical performance test of the assembled all-solid-state sodium ion battery was carried out using a blue electric tester, specifically: in the 0-4V cut-off voltage window, the first cycle coulomb efficiency of the all-solid-state sodium ion battery was 75.4% at a current density of 0.1C at a temperature of 70°C. The first cycle charge and discharge curve of the all-solid-state sodium ion battery assembled in this embodiment is shown in FIG. Fig. 9 shown.

[0170] The all-solid-state sodium ion battery single-layer soft pack (-COC-modified HC|PEO|-COC-modified NVP soft pack battery) assembled by the method is cycled in a 0-4V cut-off voltage window at a temperature of 70°C and a current density of 0.1C. The first cycle coulomb efficiency of the all-solid-state sodium ion battery is 78.4%. The cycle efficiency (i.e., the percentage of the charge specific capacity to the discharge specific capacity in each cycle) and the specific capacity curve of the all-solid-state sodium ion battery single-layer soft pack of this embodiment are as follows, Fig.10 shown.

[0171] Example 5

[0172] This embodiment provides a preparation process and performance test of a PEO composite negative electrode sheet, and the specific preparation process is as follows.

[0173] (1) Take 100 g of 85 wt % hard carbon, 5 wt % PEO (molecular weight 40 W), 10 wt % NaFS I and 5 wt % CMC, disperse them in deionized water, and stir them evenly to obtain a negative electrode slurry with a solid content of 45 wt %.

[0174] (2) The negative electrode slurry was coated on the surface of one side of the current collector copper foil, dried at 80°C for 40 minutes, and then cut into discs with a diameter of 12 mm, and then vacuum dried at 120°C for 24 hours to obtain a PEO composite negative electrode sheet containing a negative electrode composite material. The negative electrode active material surface loading on the PEO composite negative electrode sheet was 1 mg / cm 2 .

[0175] The prepared PEO composite negative electrode sheet was transferred to a vacuum glove box for later use.

[0176] The PEO composite negative electrode sheet prepared in this embodiment was assembled into an all-solid-state sodium metal battery and tested. The specific process is as follows.

[0177] The solid electrolyte membrane of the all-solid-state sodium metal battery of this embodiment is a PEO polymer electrolyte membrane. The preparation process of the solid electrolyte membrane is as follows: PEO (molecular weight Mw is 600000) and NaFS I are dissolved in acetonitrile (EO and Na +The molar ratio of 20:1 was prepared into a 0.05 g / L viscous solution, which was cast into a polytetrafluoroethylene mold and vacuum dried at 55°C for 24 hours to obtain a PEO polymer electrolyte membrane.

[0178] Assembly of all-solid-state sodium metal battery: The PEO composite negative electrode sheet and the PEO polymer electrolyte membrane are matched and assembled into an all-solid-state sodium metal battery by conventional methods.

[0179] Testing of all-solid-state sodium metal batteries: In the 0-2.5V cut-off voltage window, the all-solid-state sodium metal battery can achieve a first-cycle coulombic efficiency (I CE) of 88.86% and a first-cycle reversible capacity of 288.61mAh / g in a cycle test at a current density of 0.1C at 70°C.

[0180] The first cycle charge and discharge curve of the all-solid-state sodium metal battery prepared in this embodiment is as follows: Fig.11 shown.

[0181] Example 6

[0182] This embodiment provides a preparation process and performance test of a PEO composite negative electrode sheet, and the specific preparation process is as follows.

[0183] (1) Take 100 g of 85 wt % hard carbon, 5 wt % PEO (molecular weight 80 W), 15 wt % NaFS I and 5 wt % CMC, disperse them in deionized water, and stir them evenly to obtain a negative electrode slurry with a solid content of 45 wt %.

[0184] (2) The negative electrode slurry was coated on the surface of one side of the current collector copper foil, dried at 80°C for 40 minutes, and then cut into discs with a diameter of 12 mm, and then vacuum dried at 120°C for 24 hours to obtain a PEO composite negative electrode sheet containing a negative electrode composite material. The negative electrode active material surface loading on the PEO composite negative electrode sheet was 1 mg / cm 2 .

[0185] The prepared PEO composite negative electrode sheet was transferred to a vacuum glove box for later use.

[0186] The PEO composite negative electrode sheet prepared in this embodiment was assembled into an all-solid-state sodium metal battery and tested. The specific process is as follows.

[0187] The solid electrolyte membrane of the all-solid-state sodium metal battery of this embodiment is a PEO polymer electrolyte membrane. The preparation process of the solid electrolyte membrane is as follows: PEO (molecular weight Mw is 600000) and NaFS I are dissolved in acetonitrile (EO and Na +The molar ratio of 20:1 was prepared into a 0.05 g / L viscous solution, which was cast into a polytetrafluoroethylene mold and vacuum dried at 55°C for 24 hours to obtain a PEO polymer electrolyte membrane.

[0188] Assembly of all-solid-state sodium metal battery: The PEO composite negative electrode sheet and the PEO polymer electrolyte membrane are matched and assembled into an all-solid-state sodium metal battery by conventional methods.

[0189] Testing of all-solid-state sodium metal batteries: In the 0-2.5V cut-off voltage window, the all-solid-state sodium metal battery can achieve a first-cycle coulombic efficiency (I CE) of 87.97% and a first-cycle reversible capacity of 277.4mAh / g in a cycle test at a current density of 0.1C at 70°C.

[0190] The first cycle charge and discharge curve of the all-solid-state sodium metal battery prepared in this embodiment is as follows: Fig.12 shown.

[0191] Example 7

[0192] This embodiment provides a preparation process and performance test of a PEO composite negative electrode sheet, and the specific preparation process is as follows.

[0193] (1) Take 100 g of 85 wt % hard carbon, 5 wt % PEO (molecular weight 60 W), 20 wt % NaFS I and 5 wt % CMC, disperse them in deionized water, and stir them evenly to obtain a negative electrode slurry with a solid content of 45 wt %.

[0194] (2) The negative electrode slurry was coated on the surface of one side of the current collector copper foil, dried at 80°C for 40 minutes, and then cut into discs with a diameter of 12 mm, and then vacuum dried at 120°C for 24 hours to obtain a PEO composite negative electrode sheet containing a negative electrode composite material. The negative electrode active material surface loading on the PEO composite negative electrode sheet was 1 mg / cm 2 .

[0195] The prepared PEO composite negative electrode sheet was transferred to a vacuum glove box for later use.

[0196] The PEO composite negative electrode sheet prepared in this embodiment was assembled into an all-solid-state sodium metal battery and tested. The specific process is as follows.

[0197] The solid electrolyte membrane of the all-solid-state sodium metal battery of this embodiment is a PEO polymer electrolyte membrane. The preparation process of the solid electrolyte membrane is as follows: PEO (molecular weight Mw is 600000) and NaFS I are dissolved in acetonitrile (EO and Na + The molar ratio of 20:1 was prepared into a 0.05 g / L viscous solution, which was cast into a polytetrafluoroethylene mold and vacuum dried at 55°C for 24 hours to obtain a PEO polymer electrolyte membrane.

[0198] Assembly of all-solid-state sodium metal battery: The PEO composite negative electrode sheet and the PEO polymer electrolyte membrane are matched and assembled into an all-solid-state sodium metal battery by conventional methods.

[0199] Testing of all-solid-state sodium metal batteries: In the 0-2.5V cut-off voltage window, the all-solid-state sodium metal battery can achieve a first-cycle coulombic efficiency (I CE) of 89.17% and a first-cycle reversible capacity of 281.37mAh / g in a cycle test at a current density of 0.1C at 70°C.

[0200] The first cycle charge and discharge curve of the all-solid-state sodium metal battery prepared in this embodiment is as follows: Fig.13 shown.

[0201] 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. A PEO composite negative electrode plate, characterized in that: The PEO composite negative electrode plate includes: a current collector, and a negative electrode composite material attached to one side of the current collector; The negative electrode composite material comprises: a negative electrode active material, a binder, and polyethylene oxide (PEO) wrapped on the surface and in the gaps of the negative electrode active material; The PEO has a molecular chain segment that absorbs sodium ions; the molecular chain segment forms a sodium ion transmission channel on the surface of the negative electrode active material; the molecular weight of the PEO ranges from 20W to 100W; The mass of the PEO accounts for 1% to 30% of the total mass of the negative electrode composite material; The mass of the negative electrode active material accounts for 50%-99% of the total mass of the negative electrode composite material; The PEO composite negative electrode plate is used in an all-solid-state sodium ion battery; during the cycle of the all-solid-state sodium ion battery, the sodium ions repeat the adsorption and desorption process with the PEO groups along the molecular chain segments, so that the sodium ions are transported on the molecular chain segments.

2. The PEO composite negative electrode sheet according to claim 1, characterized in that: The negative electrode active material includes: one or more of carbon-based materials, silicon-based materials, titanium-based materials, metal oxide negative electrode materials, and alloy materials; The current collector includes copper foil or aluminum foil.

3. The PEO composite negative electrode sheet according to claim 2, characterized in that: The carbon-based material is an amorphous carbon material, including hard carbon or soft carbon; the silicon-based material includes a silicon-oxygen material and / or a silicon-carbon composite material; The titanium-based materials include: Na2Ti3O7, Li4Ti5O 12 、Na 0.66 [Li 0.22 Ti 0.78 ]O2、Na 0.6 [Cr 0.6 Ti 0.4 ]One or more of O2, Na2TiOPO4, Na2Ti2(PO4)3.

4. The PEO composite negative electrode sheet according to claim 1, characterized in that: The binder comprises: one or more of polyvinylidene fluoride, polyvinyl alcohol, polyacrylamide, sodium hydroxymethyl cellulose, polyacrylic acid, polytetrafluoroethylene, and sodium alginate; the binder accounts for 0-10% of the total mass percentage of the negative electrode composite material.

5. The PEO composite negative electrode sheet according to claim 1, characterized in that: The negative electrode composite material further includes a sodium salt; the sodium salt includes: NaFSI and / or NaTFSI; the sodium salt accounts for 0-20% of the total mass percentage of the negative electrode composite material.

6. A method for preparing a PEO composite negative electrode sheet according to any one of claims 1 to 5, characterized in that: The preparation method comprises: Adding the negative electrode active material, PEO, sodium salt and binder to the dispersant and stirring evenly to obtain a negative electrode slurry; The negative electrode slurry is coated on one side of the current collector, cut or sliced ​​after drying, and then vacuum dried to obtain a PEO composite negative electrode sheet containing the negative electrode composite material.

7. The preparation method according to claim 6, characterized in that The negative electrode active material includes: one or more of carbon-based materials, silicon-based materials, titanium-based materials, metal oxide negative electrode materials, and alloy materials; wherein, the carbon-based material is an amorphous carbon material, including hard carbon or soft carbon; the silicon-based material includes silicon-oxygen materials and / or silicon-carbon composite materials; the titanium-based material includes: Na2Ti3O7, Li4Ti5O 12 、Na 0.66 [Li 0.22 Ti 0.78 ]O2、Na 0.6 [Cr 0.6 Ti 0.4 ]One or more of O2, Na2TiOPO4, Na2Ti2(PO4)3; The PEO includes a molecular weight range of 20W-100W; The binder includes: one or more of polyvinylidene fluoride, polyvinyl alcohol, polyacrylamide, sodium hydroxyethyl cellulose, polyacrylamide, and polytetrafluoroethylene; The sodium salts include: NaFSI and / or NaTFS I; The mass ratio of the negative electrode active material, PEO, sodium salt and binder is [50-90]: [1-30]: [0-20]: [0-10]; The dispersant includes deionized water or N-methylpyrrolidone; The current collector includes copper foil or aluminum foil.

8. The preparation method according to claim 6, characterized in that The drying temperature is 80°C-100°C, and the drying time is 40 minutes-8 hours; The vacuum drying temperature is 120° C., and the vacuum drying time is 10 to 15 hours.

9. An all-solid-state sodium ion battery, characterized in that: The all-solid-state sodium ion battery comprises a positive electrode sheet, a solid electrolyte membrane and a PEO composite negative electrode sheet according to any one of claims 1 to 5; The solid electrolyte membrane is prepared by using one or more of an inorganic solid electrolyte, a polymer solid electrolyte, and an inorganic-organic composite solid electrolyte.

10. The all-solid-state sodium ion battery according to claim 9, characterized in that: The inorganic solid electrolyte includes: one or more of halide-based, oxide-based solid electrolytes and modified derivatives thereof, LLZO and modified derivatives thereof, LATP and modified derivatives thereof, LLTO and modified derivatives thereof, sulfide-based solid electrolytes, boron-based solid electrolytes and modified derivatives thereof; The polymer solid electrolyte comprises one or more of polyethylene oxide and its modified derivatives, polycarbonate and its derivatives, polyacrylonitrile and its derivatives, polyvinyl alcohol and its derivatives, polyvinyl pyrrolidone and its derivatives, polyvinylidene fluoride and its derivatives, polypropylene oxide and its derivatives, polymethyl methacrylate and its derivatives; The inorganic-organic composite solid electrolyte is a composite of the inorganic solid electrolyte and the organic solid electrolyte; The positive electrode active material of the positive electrode plate includes any one of phosphates, ternary materials, vanadium oxides, vanadates, transition metal oxides, Prussian blue compounds, and polyanion compounds.

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