Composite inorganic solid-state electrolyte coating, negative electrode sheet, and sodium battery

Abstract

The application discloses a composite inorganic solid-state electrolyte coating, a negative electrode sheet and a sodium battery, and the composite inorganic solid-state electrolyte coating comprises a first conductive agent, an inorganic solid-state electrolyte and a first binder. 1+x Zr2Si x P 3‑x O 12 , Na3PSe4, wherein 0<=x<=3; the first binder comprises sodium carboxymethyl cellulose (CMC) and / or styrene butadiene rubber (SBR); the mass percentage of the first conductive agent in the total mass of the composite inorganic solid-state electrolyte coating is 10%-50%; the mass percentage of the inorganic solid-state electrolyte in the total mass of the composite inorganic solid-state electrolyte coating is 40%-90%; and the mass percentage of the first binder in the total mass of the composite inorganic solid-state electrolyte coating is 2%-20%. The composite inorganic solid-state electrolyte coating is applied to the sodium battery, so that the ionic conductivity, the overcharge and overdischarge resistance and the rate performance of the sodium battery are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium battery materials, in particular to a composite inorganic solid-state electrolyte coating, a negative electrode sheet and a sodium battery. BACKGROUND

[0002] In the past three decades, lithium ion batteries have been widely used in electric vehicles, consumer electronics, aerospace, smart devices, medical devices and large-scale energy storage. However, the scarcity of lithium resources has greatly compressed the profit space of lithium ion batteries, and the rising prices of raw materials such as lithium carbonate have also stimulated the vigorous development of low-cost secondary batteries such as sodium ion batteries. The sodium element on earth is abundant in reserves, although the energy density of sodium ion batteries is slightly inferior to that of lithium ion batteries, but the low-cost competitive advantage makes sodium ion batteries the star of secondary batteries.

[0003] However, sodium ion batteries are prone to short circuit under the environment of overcharge, overdischarge, high temperature, drop, extrusion and collision. Battery short circuit can cause severe heat release in a short time, resulting in battery heating and smoking, severe gas production, battery volume expansion, and even fire and explosion. In order to realize the large-scale application of sodium ion batteries, this safety hazard problem must be solved.

[0004] In order to solve the above problems, the common strategy is to coat and dope the negative electrode material of sodium ion battery to improve the thermal stability. However, this will reduce the energy density of sodium ion battery and reduce the battery dynamics performance, and cannot effectively prevent the short circuit problem that often occurs in the use of extrusion, collision, drop and other scenarios. In order to solve this problem, ceramic coating modification of the negative electrode current collector of sodium ion battery is a simple and effective new strategy. Solid-state electrolyte has good chemical stability, thermal stability, wide electrochemical window, better oxidation and reduction resistance, and no electronic conductivity.

[0005] Therefore, the development of a solid-state electrolyte coating makes the solid-state electrolyte used for the surface coating of the negative electrode current collector of sodium battery, which can effectively prevent the short circuit problem of the battery under adverse working conditions, reduce the safety risk of sodium battery application, and also make the negative electrode current collector have certain ionic conductivity in addition to electronic conductivity, reduce the polarization in the electrode cycle process, and be beneficial to the construction of high-rate and safer sodium battery, which becomes our research direction. SUMMARY

[0006] The composite inorganic solid-state electrolyte coating, the negative electrode sheet and the sodium battery provided by the embodiment of the present application coat the inorganic solid-state electrolyte beta-Al2O3, Na 1+x Zr2Si x P 3-x O 12The composite inorganic solid-state electrolyte coating is prepared by one or more of Na3PSe4, Na3PS4 and Na3PSe4, and the three inorganic solid-state electrolytes have good chemical stability and electrochemical stability, a wide electrochemical window, are not easy to be reduced, are not electronic conductive, and can improve the adhesion of the negative electrode coating on the surface of the current collector. When the negative electrode sheet coated with the composite inorganic solid-state electrolyte coating is applied to a sodium battery, the ionic conductivity of the sodium battery can be improved, the sheet resistance of the negative electrode sheet can be reduced, the polarization in the cycle process can be reduced, the rate performance of the sodium battery can be improved, the overcharge and overdischarge resistance of the sodium battery can be improved, and the short-circuit resistance of the negative electrode under adverse working conditions can be improved, so that the safety hidden danger of the sodium battery in the actual application process can be greatly reduced.

[0007] In a first aspect, an embodiment of the present application provides a composite inorganic solid-state electrolyte coating, the composite inorganic solid-state electrolyte coating comprising: a first conductive agent, an inorganic solid-state electrolyte and a first binder;

[0008] The first conductive agent comprises one or more of carbon black, carbon nanotubes and graphene.

[0009] The inorganic solid-state electrolyte comprises one or more of β-Al2O3, Na3PSe4, Na3PS4 and Na3PSe4, wherein 0≤x≤3. 1+x Zr2Si x P 3-x O 12 The first conductive agent comprises one or more of carbon black, carbon nanotubes and graphene.

[0010] The first binder comprises sodium carboxymethyl cellulose (CMC) and / or styrene butadiene rubber (SBR).

[0011] The mass percentage of the first conductive agent in the total mass of the composite inorganic solid-state electrolyte coating is 10%-50%.

[0012] The mass percentage of the inorganic solid-state electrolyte in the total mass of the composite inorganic solid-state electrolyte coating is 40%-90%.

[0013] The mass percentage of the first binder in the total mass of the composite inorganic solid-state electrolyte coating is 2%-20%.

[0014] In a second aspect, an embodiment of the present application provides a negative electrode sheet, the negative electrode sheet comprising the composite inorganic solid-state electrolyte coating of the first aspect.

[0015] The negative electrode sheet further comprises a negative electrode current collector and a negative electrode active material coating.

[0016] Preferably, the composite inorganic solid-state electrolyte coating is coated on both sides of the negative electrode current collector; and the negative electrode current collector is a copper foil.

[0017] The composite inorganic solid-state electrolyte coating is a single layer, and the thickness is 1-5 μm;

[0018] The negative active material coating is coated on the surface of the composite inorganic solid-state electrolyte coating.

[0019] The thickness of the negative active material coating is 50-100 μm.

[0020] Preferably, the negative active material coating comprises a negative active material, a second conductive agent and a second binder.

[0021] Further preferably, the negative active material comprises one or more of hard carbon, soft carbon, TiO2, Na2Ti3O7, Na2Ti6O 13 , Na 0.6 [Cr 0.6 Ti 0.4 ]O2, NaTiOPO4, NaTi2(PO4)3, Li4Ti5O 12 , MoS2.

[0022] The second conductive agent comprises one or more of carbon black, carbon nanotubes, graphene.

[0023] The second binder comprises one or more of polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyimide (PI), sodium carboxymethyl cellulose (CMC) or styrene butadiene rubber (SBR).

[0024] Further preferably, the mass percentage of the second conductive agent in the total mass of the negative active material coating is 1.5%-8%.

[0025] The mass percentage of the negative active material in the total mass of the negative active material coating is 84%-97%.

[0026] The mass percentage of the second binder in the total mass of the negative active material coating is 1.5%-8%.

[0027] In a third aspect, an embodiment of the present application provides a sodium battery, which comprises the negative electrode sheet of the second aspect.

[0028] Preferably, the sodium battery comprises any one of a liquid sodium-ion battery, a sodium-sulfur battery, a sodium-air battery, a solid-liquid hybrid sodium battery or a full-solid-state sodium battery.

[0029] The composite inorganic solid-state electrolyte coating, the negative electrode sheet and the sodium battery provided by the embodiments of the present application use inorganic solid-state electrolyte β-Al2O3, Na 1+x Zr2Si x P3-x O 12 One or more of Na3PSe4 are prepared to obtain a composite inorganic solid-state electrolyte coating, since the three inorganic solid-state electrolytes have good chemical stability and electrochemical stability, have a wide electrochemical window, are not easy to be reduced, are not electron-conducting, and can improve the adhesion of the negative electrode coating on the surface of the current collector, the negative electrode sheet coated with the composite inorganic solid-state electrolyte coating can improve the ionic conductivity of the sodium battery, reduce the sheet resistance value of the negative electrode sheet, reduce the polarization in the cycle process, improve the rate performance of the sodium battery, can improve the overcharge and overdischarge resistance of the sodium battery, improve the short-circuit resistance of the negative electrode side under adverse working conditions, thereby greatly reducing the safety hazards of the sodium battery in the actual application process. BRIEF DESCRIPTION OF DRAWINGS

[0030] The technical solutions of the embodiments of the present application will be further described in detail below with the help of the drawings and examples.

[0031] Figure 1 is a structural schematic diagram of the negative electrode sheet provided by the embodiments of the present application;

[0032] Figure 2 is a flow chart of the preparation method of the negative electrode sheet provided by the embodiments of the present application. DETAILED DESCRIPTION

[0033] The present application will be further described in detail below with the help of the drawings and specific examples, but it should be understood that these examples are only used for more detailed description, and should not be understood as limiting the present application in any form, i.e. not intended to limit the protection scope of the present application.

[0034] The embodiments of the present application provide a composite inorganic solid-state electrolyte coating, which comprises: a first conductive agent, an inorganic solid-state electrolyte and a first binder.

[0035] The first conductive agent comprises one or more of carbon black, carbon nanotubes and graphene, and the mass percentage of the first conductive agent in the total mass of the composite inorganic solid-state electrolyte coating is 10%-50%.

[0036] The inorganic solid-state electrolyte comprises: β-Al2O3, Na 1+x Zr2Si x P 3-x O 12one or more of Na3PSe4, wherein 0≤x≤3; the three inorganic solid-state electrolytes have better chemical stability and electrochemical stability, are not easy to be reduced, can improve the adhesion of the negative electrode coating on the surface of the current collector, thereby improving the ionic conductivity of the surface of the sodium battery, reducing the sheet resistance of the negative electrode sheet, reducing the polarization in the cycle process, and improving the rate performance of the sodium battery; the mass percentage of the inorganic solid-state electrolyte in the total mass of the composite inorganic solid-state electrolyte coating is 40%-90%.

[0037] The first binder includes sodium carboxymethyl cellulose (CMC) and / or styrene butadiene rubber (SBR); the mass percentage of the first binder in the total mass of the composite inorganic solid-state electrolyte coating is 2%-20%.

[0038] The embodiment of the present application provides a negative electrode sheet, which includes the above-mentioned composite inorganic solid-state electrolyte coating, a negative electrode current collector and a negative electrode active material coating.

[0039] The negative electrode active material coating includes a negative electrode active material, a second conductive agent and a second binder.

[0040] The negative electrode active material includes one or more of hard carbon, soft carbon, TiO2, Na2Ti3O7, Na2Ti6O 13 , Na 0.6 [Cr 0.6 Ti 0.4 ]O2, NaTiOPO4, NaTi2(PO4)3, Li4Ti5O 12 , MoS2; the mass percentage of the negative electrode active material in the total mass of the negative electrode active material coating is 84%-97%.

[0041] The second conductive agent includes one or more of carbon black, carbon nanotubes and graphene; the mass percentage of the second conductive agent in the total mass of the negative electrode active material coating is 1.5%-8%.

[0042] The second binder includes one or more of polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyimide (PI), sodium carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR); the mass percentage of the second binder in the total mass of the negative electrode active material coating is 1.5%-8%.

[0043] The composite inorganic solid-state electrolyte coating is coated on both sides of the surface of the negative electrode current collector copper foil, the coating is a single layer, and the thickness is between 1 μm and 5 μm; the negative electrode active material coating is coated on the surface of the composite inorganic solid-state electrolyte coating, and the thickness is between 50 μm and 100 μm.

[0044] The structural diagram of the negative electrode sheet provided by the embodiment of the present application is as shown in the following figure:Figure 1 As shown, it can be seen that each of the two sides of the negative current collector is coated with a layer of composite inorganic solid-state electrolyte coating, and each of the surfaces of the composite inorganic solid-state electrolyte coating is coated with a layer of negative active material coating.

[0045] The embodiment of the present application provides a preparation method of the above negative pole piece, which specifically comprises the following steps: Figure 2 As shown, specifically comprising the following steps:

[0046] In step 210, the inorganic solid-state electrolyte, the first conductive agent, the first binder and the first solvent are mixed and uniformly dispersed in a dispersion device to prepare a slurry of the composite inorganic solid-state electrolyte coating.

[0047] The inorganic solid-state electrolyte comprises one or more of β-Al2O3, Na 1+x Zr2Si x P 3-x O 12 , Na3PSe4, wherein 0≤x≤3.

[0048] The first conductive agent comprises one or more of carbon black, carbon nanotube and graphene.

[0049] The first binder comprises sodium carboxymethyl cellulose (CMC) and / or styrene butadiene rubber (SBR).

[0050] The first solvent is deionized water or acetone.

[0051] The dispersion device comprises any one of a disperser, a sand mill, a homogenizer, a ball mill and an ultrasonic stirrer, and the dispersion device is not particularly required, and the inorganic solid-state electrolyte, the first conductive agent and the second binder in the slurry can be uniformly dispersed.

[0052] In step 220, the slurry of the composite inorganic solid-state electrolyte coating is coated on each of the two sides of the negative current collector copper foil, and is placed in an oven for baking, so that the negative current collector copper foil with the composite inorganic solid-state electrolyte coating is obtained after drying, and is ready for use.

[0053] The coating method comprises any one of roller coating, spraying or micro-gravure coating.

[0054] The baking condition is specifically that the slurry is dried at 60-110°C for 0.5-2 hours, so that the solvent in the slurry is volatilized.

[0055] In step 230, the negative active material, the second conductive agent, the second binder and the second solvent are mixed and uniformly dispersed in a dispersion device to prepare a slurry of the negative active material coating.

[0056] Among them, the negative electrode active materials include: hard carbon, soft carbon, TiO2, Na2Ti3O7, Na2Ti6O 13 、Na 0.6 [Cr 0.6 Ti 0.4 ]O2, NaTiOPO4, NaTi2(PO4)3, Li4Ti5O 12 , MoS2;

[0057] The second conductive agent includes one or more of carbon black, carbon nanotubes, and graphene;

[0058] The second binder includes: one or more of polyacrylonitrile PAN, polyvinyl alcohol PVA, polytetrafluoroethylene PTFE, polyvinylidene fluoride PVDF, polyimide PI, sodium carboxymethyl cellulose CMC or styrene-butadiene rubber SBR;

[0059] The second solvent is deionized water and / or N-methylpyrrolidone (NMP);

[0060] The dispersing equipment includes but is not limited to any one of a disperser, a sand mill, a homogenizer, a ball mill, and an ultrasonic mixer. There are no special requirements for the dispersing equipment, as long as the negative electrode active material, the second conductive agent, and the second binder in the slurry can be evenly dispersed.

[0061] Step 240 , coating a layer of negative electrode active material coating slurry on both sides of the composite inorganic solid electrolyte coating on both sides of the negative electrode current collector, baking in an oven, and drying to obtain a negative electrode sheet;

[0062] Wherein, the coating process in this step is roller coating or spray coating process;

[0063] The baking conditions are as follows: drying at 90° C. to 210° C. for 0.5 to 2 hours to volatilize the solvent in the slurry of the negative electrode active material coating.

[0064] The method for preparing the negative electrode sheet provided in the embodiment of the present invention is simple to operate and applicable to large-scale batch production.

[0065] The negative electrode sheet containing the composite inorganic solid electrolyte coating and the negative electrode active material coating in the embodiment of the present invention can be used in sodium batteries, which include but are not limited to any one of liquid sodium ion batteries, sodium sulfur batteries, sodium air batteries, solid-liquid hybrid sodium batteries or all-solid-state sodium batteries.

[0066] The inorganic solid-state electrolyte in the composite inorganic solid-state electrolyte coating has good chemical stability and electrochemical stability, so that the adhesion of the negative electrode coating on the surface of the current collector can be improved, the ionic conductivity of the surface of the sodium battery is further improved, the sheet resistance of the negative electrode sheet is reduced, the polarization in the cycle process is reduced, the rate performance of the sodium battery is improved, the overcharge and overdischarge resistance of the sodium battery can be improved, and the short circuit resistance of the negative electrode under adverse working conditions is improved, so that the safety hidden danger of the sodium battery in the actual application process is greatly reduced.

[0067] In order to better understand the technical solutions provided by the present application, the preparation method and characteristics of the composite inorganic solid-state electrolyte coating and the negative electrode sheet are described below with specific examples.

[0068] Example 1

[0069] The present embodiment provides a preparation process and performance test of a negative electrode sheet containing a composite inorganic solid-state electrolyte coating, and the specific steps are as follows.

[0070] (1) The inorganic solid-state electrolyte β-Al2O3, the first conductive agent carbon black and the first binder CMC are weighed according to the mass ratio of 70:10:20, mixed with deionized water, and uniformly dispersed in a dispersing machine to prepare a slurry of the composite inorganic solid-state electrolyte coating, wherein the solid content in the slurry is 50%.

[0071] (2) A layer of the slurry of the composite inorganic solid-state electrolyte coating is coated on both sides of the negative electrode current collector copper foil, and is placed in an oven at 100℃ for 1 hour, and after drying, a negative electrode current collector with a composite inorganic solid-state electrolyte coating is obtained, wherein the thickness of the composite inorganic solid-state electrolyte coating is 2μm.

[0072] (3) The negative electrode active material hard carbon, the second conductive agent carbon black and the second binder PVDF are mixed according to the mass ratio of 90:6:4, mixed with the solvent NMP, and uniformly dispersed in a dispersing device to prepare a slurry of the negative electrode active material coating, wherein the solid content in the slurry is 80%.

[0073] (4) A layer of the slurry of the negative electrode active material coating is coated on both sides of the surface of the composite inorganic solid-state electrolyte coating, and is placed in an oven at 210℃ for 1 hour, and after drying, a negative electrode sheet is obtained, wherein the thickness of the negative electrode active material coating is 80μm.

[0074] The negative electrode sheet prepared in the present embodiment is tested for sheet resistance and ionic conductivity, and the test results are shown in Table 1.

[0075] Among them, the ionic conductivity is obtained by electrochemical workstation (ZENNIUM, ZAHNER) test, and the sheet resistance of the electrode sheet is obtained by electrode resistance tester (IEST Yuaneng Technology, model BER2500).

[0076] The negative electrode sheet prepared in this example and the NaFePO4 positive electrode sheet were assembled into a sodium battery by a conventional method and tested.

[0077] The test method was as follows: charging at 0.1C, 0.2C, 0.33C, 1C and 3C rates to the charge termination voltage, and then discharging at the same rate to the discharge termination voltage, and the average discharge capacity at each rate was calculated after 5 cycles at each rate. The test results are shown in Table 2.

[0078] Example 2

[0079] This example provides a preparation process and performance test of a negative electrode sheet containing a composite inorganic solid-state electrolyte coating, and the specific steps are as follows.

[0080] (1) Inorganic solid-state electrolyte Na 1.3 Zr2Si 0.3 P 2.7 O 12 , first conductive agent graphene, first binder CMC and SBR in a mass ratio of 90:8:1:1, and deionized water were mixed and uniformly dispersed in a dispersion device to prepare a composite inorganic solid-state electrolyte coating slurry, wherein the solid content in the slurry was 30%.

[0081] (2) The slurry of the composite inorganic solid-state electrolyte coating was coated on both sides of the negative electrode current collector copper foil by spraying, and was placed in an oven at 110°C for 2 hours. After drying, a negative electrode current collector with a composite inorganic solid-state electrolyte coating was obtained, wherein the thickness of the composite inorganic solid-state electrolyte coating was 5μm.

[0082] (3) The negative electrode active material soft carbon, the second conductive agent carbon nanotube, and the second binder PVA in a mass ratio of 88:6:6 were mixed with the solvent NMP, and were uniformly dispersed in a dispersion device to prepare a negative electrode active material coating slurry, wherein the solid content in the slurry was 60%.

[0083] (4) The slurry of the negative electrode active material coating was coated on both surfaces of the composite inorganic solid-state electrolyte coating by roll coating, and was placed in an oven at 210°C for 2 hours. After drying, a negative electrode sheet was obtained, wherein the thickness of the negative electrode active material coating was 50μm.

[0084] The negative electrode sheet prepared in this example was tested for sheet resistance and ionic conductivity, and the test method was the same as in Example 1. The test results are shown in Table 1.

[0085] The negative electrode sheet prepared in this example was assembled into a sodium battery and tested, and the assembly process and test process were the same as in Example 1. The test results are shown in Table 2.

[0086] Example 3

[0087] This example provides a preparation process and performance test of a negative electrode sheet containing a composite inorganic solid-state electrolyte coating. The specific steps are as follows.

[0088] (1) Inorganic solid-state electrolyte Na3PSe4, first conductive agent carbon nanotube, and first binder SBR were weighed according to a mass ratio of 40:50:10, mixed with deionized water, and placed in a dispersing machine for uniform dispersion to prepare a slurry of the composite inorganic solid-state electrolyte coating, wherein the solid content in the slurry was 10%.

[0089] (2) The slurry of the composite inorganic solid-state electrolyte coating was coated on both sides of the negative electrode current collector copper foil, and placed in an oven for baking at 70°C for 1.5 hours. After drying, the negative electrode current collector with the composite inorganic solid-state electrolyte coating was obtained, wherein the thickness of the composite inorganic solid-state electrolyte coating was 1 μm.

[0090] (3) The negative electrode active material Na2Ti3O7, second conductive agent carbon nanotube, and second binder PI were mixed with the solvent NMP according to a mass ratio of 85:10:5, and placed in a dispersing device for uniform dispersion to prepare a slurry of the negative electrode active material coating, wherein the solid content in the slurry was 70%.

[0091] (4) The slurry of the negative electrode active material coating was coated on both sides of the surface of the composite inorganic solid-state electrolyte coating, and placed in an oven for baking at 210°C for 1 hour. After drying, the negative electrode sheet was obtained, wherein the thickness of the negative electrode active material coating was 100 μm.

[0092] The negative electrode sheet prepared in this example was tested for sheet resistance and ionic conductivity, and the test method was the same as in Example 1. The test results are shown in Table 1.

[0093] The negative electrode sheet prepared in this example was assembled into a sodium battery and tested, and the assembly process and test process were the same as in Example 1. The test results are shown in Table 2.

[0094] Example 4

[0095] This example provides a preparation process and performance test of a negative electrode sheet containing a composite inorganic solid-state electrolyte coating. The specific steps are as follows.

[0096] (1) Inorganic solid-state electrolyte β-Al2O3, Na 1+x Zr2Si x P 3-x O 12Na3PSe4(three solid-state electrolytes in a mass ratio of 1:2:1), a first conductive agent carbon black, and a first binder CMC in a mass ratio of 70:10:20 are weighed, mixed with deionized water, and placed in a dispersing machine to be uniformly dispersed to prepare a slurry of the composite inorganic solid-state electrolyte coating, wherein the solid content in the slurry is 50%.

[0097] (2) The slurry of the composite inorganic solid-state electrolyte coating is coated on both sides of the negative electrode current collector copper foil, and placed in an oven to be baked at 100°C for 1 hour. After drying, the negative electrode current collector with the composite inorganic solid-state electrolyte coating is obtained, wherein the thickness of the composite inorganic solid-state electrolyte coating is 2 μm.

[0098] (3) The negative electrode active material Na2Ti3O7, a second conductive agent carbon black, and a second binder PVDF in a mass ratio of 90:6:4 are mixed with deionized water, and placed in a dispersing device to be uniformly dispersed to prepare a slurry of the negative electrode active material coating, wherein the solid content in the slurry is 80%.

[0099] (4) The slurry of the negative electrode active material coating is coated on both sides of the surface of the composite inorganic solid-state electrolyte coating, and placed in an oven to be baked at 110°C for 1.5 hours. After drying, the negative electrode sheet is obtained, wherein the thickness of the negative electrode active material coating is 80 μm.

[0100] The square resistance and ionic conductivity of the negative electrode sheet prepared in this example are tested, and the test method is the same as that in Example 1. The test results are shown in Table 1.

[0101] The negative electrode sheet prepared in this example is assembled into a sodium battery and tested, and the assembly process and the test process are the same as those in Example 1. The test results are shown in Table 2.

[0102] In order to better illustrate the effect of the embodiment of the present application, Comparative Example 1 is compared with the above examples.

[0103] Comparative Example 1

[0104] The difference between this comparative example and Example 1 is that the negative electrode sheet without the composite inorganic solid-state electrolyte coating is used, and the negative electrode active material coating of the negative electrode sheet and the preparation method are the same as those in Example 1.

[0105] The square resistance and ionic conductivity of the negative electrode sheet of this comparative example are tested, and the test method is the same as that in Example 1. The test results are shown in Table 1.

[0106] The negative electrode sheet prepared in this comparative example is assembled into a sodium battery and tested, and the assembly process and the test process are the same as those in Example 1. The test results are shown in Table 2.

[0107] Table 1 is a summary of the test data of the coating thickness of Examples 1-4 and the sheet resistance and ionic conductivity of the current collector after coating.

[0108]

[0109]

[0110] Table 1

[0111] As can be seen from the comparison of the test data in Table 1, the ionic conductivity of the negative electrode sheet containing the composite inorganic solid-state electrolyte coating of Examples 1-4 is much greater than that of Comparative Example 1, indicating that the negative electrode sheet containing the composite inorganic solid-state electrolyte coating provided by the present application has good sodium ion conductivity, which is beneficial to the performance of the sodium battery negative active material kinetics.

[0112] Table 2 is a summary of the average discharge capacity test data of the sodium batteries assembled by Examples 1-4.

[0113] Number Room temperature rate (1 C / 0.33 C average discharge capacity) Room temperature rate (3 C / 1 C average discharge capacity) Example 1 92.5％ 86.7％ Example 2 95.6％ 90.9％ Example 3 93.4％ 88.5％ Comparative Example 1 89.7％ 67.8％

[0114] Table 2

[0115] As can be seen from the comparison of the test data in Table 2, the room temperature rate performance of the battery assembled by the negative electrode sheet containing the composite inorganic solid-state electrolyte coating of Examples 1-4 is much greater than that of Comparative Example 1, indicating that the negative electrode sheet containing the composite inorganic solid-state electrolyte coating provided by the present application is beneficial to improve the rate performance of the sodium battery.

[0116] The composite inorganic solid-state electrolyte coating, negative electrode sheet and sodium battery provided by the present application can improve the ionic conductivity of the surface of the sodium battery, reduce the sheet resistance value of the negative electrode sheet, reduce the polarization in the cycle process, improve the rate performance of the sodium battery, improve the overcharge and overdischarge resistance of the sodium battery, and improve the short-circuit resistance of the negative electrode side under adverse working conditions, thereby greatly reducing the safety hazards of the sodium battery in actual application. 1+x Zr2Si x P 3-x O 12 , Na3PSe4, to prepare a composite inorganic solid-state electrolyte coating. Since these three inorganic solid-state electrolytes have good chemical stability and electrochemical stability, a wide electrochemical window, are not easily reduced, do not conduct electrons, and can improve the adhesion of the negative electrode coating on the surface of the current collector, the negative electrode sheet coated with the composite inorganic solid-state electrolyte coating can be applied to a sodium battery, which can improve the ionic conductivity of the surface of the sodium battery, reduce the sheet resistance value of the negative electrode sheet, reduce the polarization in the cycle process, improve the rate performance of the sodium battery, improve the overcharge and overdischarge resistance of the sodium battery, and improve the short-circuit resistance of the negative electrode side under adverse working conditions, thereby greatly reducing the safety hazards of the sodium battery in actual application.

[0117] The above detailed description of the specific embodiments of the present application has been given to understand the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A sodium battery, characterized by, The sodium battery comprises a negative electrode sheet; the negative electrode sheet comprises a composite inorganic solid-state electrolyte coating; the negative electrode sheet further comprises a negative electrode current collector and a negative electrode active material coating; the composite inorganic solid-state electrolyte coating is coated on the two side surfaces of the negative electrode current collector; and the negative electrode active material coating is coated on the surface of the composite inorganic solid-state electrolyte coating. The composite inorganic solid-state electrolyte coating comprises a first conductive agent, an inorganic solid-state electrolyte and a first binder. The first conductive agent comprises one or more of carbon black, carbon nanotubes and graphene. The inorganic solid-state electrolyte includes one or more of: β-Al2O3, Na 1+x Zr2Si x P 3-x O 12 , Na3PSe4, wherein 0≤x≤3; The first binder comprises sodium carboxymethyl cellulose and / or styrene butadiene rubber SBR. The mass percentage of the first conductive agent in the total mass of the composite inorganic solid-state electrolyte coating is 10%-50%. The mass percentage of the inorganic solid-state electrolyte in the total mass of the composite inorganic solid-state electrolyte coating is 40%-90%. The mass percentage of the first binder in the total mass of the composite inorganic solid-state electrolyte coating is 2%-20%. The negative electrode active material coating comprises: negative electrode active material; the negative electrode active material comprises: hard carbon, soft carbon, TiO2, Na2Ti3O7, Na2Ti6O 13 、Na 0.6 [Cr 0.6 Ti 0.4 ]O2, NaTiOPO4, NaTi2(PO4)3, Li4Ti5O 12 , MoS2 or more.

2. The sodium battery of claim 1, wherein, The negative electrode current collector is a copper foil. The composite inorganic solid-state electrolyte coating is a single layer with a thickness of 1-5 μm. The thickness of the negative electrode active material coating is 50-100 μm.

3. The sodium battery of claim 1, wherein, The negative electrode active material coating further comprises a second conductive agent and a second binder.

4. The sodium battery of claim 3, wherein, The second conductive agent comprises one or more of carbon black, carbon nanotubes and graphene. The second binder comprises one or more of polyacrylonitrile PAN, polyvinyl alcohol PVA, polytetrafluoroethylene PTFE, polyvinylidene fluoride PVDF, polyimide PI, sodium carboxymethyl cellulose or styrene butadiene rubber SBR.

5. The sodium battery of claim 3, wherein, The mass percentage of the second conductive agent in the total mass of the negative electrode active material coating is 1.5%-8%. The mass percentage of the negative electrode active material in the total mass of the negative electrode active material coating is 84%-97%. The mass percentage of the second binder in the total mass of the negative electrode active material coating is 1.5%-8%.

6. The sodium battery of claim 1, wherein, The sodium battery comprises any one of a liquid sodium ion battery, a sodium-sulfur battery, a sodium-air battery, a solid-liquid hybrid sodium battery or a full-solid-state sodium battery.

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