Solid electrolyte, its manufacturing method, secondary battery, battery module, battery pack, and power consumption device

Abstract

This application provides a solid electrolyte, its manufacturing method, a secondary battery, a battery module, a battery pack, and a power consumption device. The solid electrolyte includes a dense layer and a porous layer located on at least one side of the dense layer, the porosity of the porous layer being greater than that of the dense layer. The porous layer is advantageous for improving the interfacial wettability between the solid electrolyte and the positive electrode plate / negative electrode plate and for filling the positive and negative active materials into the pores, thereby reducing the interfacial resistance of the battery and improving the rate and low-temperature performance of the battery.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is incorporated by reference into Chinese patent application No. 202310070432.9, filed on January 16, 2023, entitled "Solid electrolyte, and manufacturing method thereof, secondary battery, battery module, battery pack and power consumption device," the entire contents of which are incorporated by reference into this application. [Technical Field]

[0002] The present application relates to the field of secondary battery technology, and in particular to a solid electrolyte and its manufacturing method, a secondary battery, a battery module, a battery pack, and a power consuming device. [Background technology]

[0003] In recent years, secondary batteries have been widely used in energy storage power systems such as hydroelectric, thermal, wind and solar power plants, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. As the applications of secondary batteries become more widespread, higher requirements are being placed on their performance, safety, etc.

[0004] Currently, secondary batteries generally use liquid electrolytes. However, the solvent in the liquid electrolyte is prone to side reactions with the metal anode, affecting the battery's storage performance and service life. Furthermore, the dissolution of salts degrades the lowest occupied molecular orbital of the solvent, accelerating the decomposition of the liquid electrolyte and gas precipitation, significantly reducing the battery's safety performance. Solid electrolytes, which are solvent-free and can avoid reactions with the metal anode, have attracted the attention of researchers. However, most solid electrolytes have difficulty forming good interfacial contact with the electrode, affecting interfacial dynamics and reducing the battery's rate and low-temperature performance, making them unable to meet the application needs of new-generation electrochemical systems. Summary of the Invention

[0005] The present application has been made in view of the above-mentioned problems, and an object thereof is to provide a solid electrolyte, which includes a dense layer and a porous layer located on at least one side of the dense layer, and the porous layer is advantageous for improving the interfacial wettability between the solid electrolyte and a positive electrode plate / anode electrode plate or a positive electrode-side current collector / anode electrode-side current collector, and for directly introducing a positive electrode active material / anode electrode active material into the pores, thereby reducing the interfacial resistance of the battery and improving the rate and low-temperature performance of the battery.

[0006] A first aspect of the present application provides a solid electrolyte for a secondary battery, the solid electrolyte for a secondary battery including a dense layer and a porous layer located on at least one side of the dense layer, wherein the porosity of the porous layer is greater than the porosity of the dense layer.

[0007] The solid electrolyte includes a dense layer and a porous layer located on at least one side of the dense layer, and the porosity of the porous layer is greater than that of the dense layer, which is beneficial for improving the interfacial wettability between the solid electrolyte and the positive electrode plate / negative electrode plate or the positive electrode current collector / negative electrode current collector, thereby reducing the interfacial resistance of the battery and improving the rate performance and cycle stability at room and low temperatures of the battery. On the other hand, a porous layer is located on at least one side of the dense layer, and the porosity of the porous layer is greater than that of the dense layer, which is beneficial for increasing the specific surface area of ​​the solid electrolyte and for directly incorporating the positive electrode active material / negative electrode active material into the pores, thereby improving the interfacial wettability between the solid electrolyte and the positive electrode plate / negative electrode plate or the positive electrode current collector / negative electrode current collector, improving the kinetic process between the solid electrolyte and the positive electrode plate / negative electrode plate interface or the positive electrode current collector / negative electrode current collector, and significantly improving the rate performance of the battery. On the other hand, a porous layer having a porosity larger than that of the solid electrolyte is advantageous in reducing the interfacial resistance between the solid electrolyte and the positive electrode plate / negative electrode plate, and improving the cycle stability of the battery at room temperature / low temperature.

[0008] In either embodiment, the porous layer is disposed on the surface of the dense layer.

[0009] Forming a porous layer on the surface of a dense layer not only effectively reduces the interfacial resistance of the battery, but is also advantageous in improving the rate performance and cycle stability at room and low temperatures of the battery.

[0010] In either embodiment, there are two porous layers, each connected to two opposing surfaces of the dense layer.

[0011] A porous layer is provided on each of the two opposing surfaces of the dense layer, which simultaneously improves the interfacial dynamics between the solid electrolyte and the positive and negative electrodes, reduces the interfacial resistance of the battery, and is advantageous in improving the rate performance and cycle stability at room and low temperatures of the battery.

[0012] In any embodiment, the ratio of the thickness of any one of the porous layers to the dense layer is 0.5-7.5, and optionally 1-4.

[0013] Controlling the thickness ratio of any one of the porous layers to the dense layer between 0.5 and 7.5 controls the electrochemical-mechanical effect and prevents mechanical stress during cycling from causing deformation of the solid electrolyte, which would otherwise degrade the battery's cycling performance. This reduces the interfacial resistance of the battery, improving its rate performance and cycle stability at room and low temperatures, and is advantageous for achieving both mechanical and electrical performance of the solid electrolyte. Furthermore, controlling the thickness ratio of the porous layer to the dense layer between 1 and 4 ensures a low internal resistance of the solid electrolyte's bulk phase while simultaneously providing a larger specific surface area. This further reduces the battery's internal resistance, increases the specific surface area of ​​the porous layer, and optimizes the battery's dynamic performance.

[0014] In either embodiment, the ionic conductivity of the porous layer is at least 1 / 10 of the ionic conductivity of the dense layer.

[0015] The ionic conductivity of the porous layer is controlled to more than 1 / 10 of that of the dense layer, improving the interfacial dynamics between the solid electrolyte and the positive and negative electrodes while ensuring the ionic conductivity of the solid electrolyte, thereby achieving both the interfacial dynamics and ionic conductivity of the solid electrolyte.

[0016] In either embodiment, the contact angle of molten sodium on the surface of the solid electrolyte porous layer is ≦90°, and optionally ≦70°.

[0017] The contact angle of molten sodium on the surface of the solid electrolyte porous layer is ≦90°, indicating superior wettability between the solid electrolyte porous layer and molten sodium. Combining the porous layer with the positive and negative active materials improves the interfacial dynamics between the solid electrolyte and the positive and negative electrodes, reducing the interfacial resistance of the battery and improving its rate performance and cycle stability at room and low temperatures. The contact angle of molten sodium on the surface of the solid electrolyte porous layer is ≦70°, further reducing the interfacial resistance of the battery and improving its rate performance and cycle stability at room and low temperatures.

[0018] In any embodiment, both the dense layer and the porous layer include an inorganic solid electrolyte material, which includes one or more of a sulfur-based electrolyte, a sodium fast-ion conductor, and an oxide electrolyte.

[0019] In any embodiment, the sulfur-based electrolyte is Na2S-P2S5, Na 11 Sn2PnX 12 , Na3Pn y Pn' 1-y X z X' 4-z wherein Pn includes at least one of P and Sb, X includes at least one of S and Se, Pn' includes at least one of Si, Sn and Ge, and X' includes at least one of F, Br and Cl, and 0 <y≦1、0<z≦4であり、 Sodium fast ion conductor is Na 3+x My M' 2-y Si 2-z P z O 12 wherein M and M' may independently comprise at least one of Zr, Ca, Mg, Zn, La, Ti, and Nb; and 0≦x≦1, 0 <y≦2、0≦z<2であり、 The oxide electrolyte includes at least one of Na-β-Al2O3 and Na-β"-Al2O3, wherein the Na-β-Al2O3 includes β-Na2O, and the Na-β"-Al2O3 includes β"-Na2O.5Al2O3. Optionally, the oxide electrolyte further includes an inorganic oxide, which includes one or more of Li2O, MgO, TiO2, ZrO2, YO3, MnO2, SiO2, and Fe2O3. The mass content of the inorganic oxide is 0.5% to 30% based on the total mass of the oxide electrolyte.

[0020] The above-mentioned sulfur-based electrolyte, sodium fast ion conductor, and oxide electrolyte are inorganic solid electrolyte materials for the dense layer and porous layer, and are all advantageous in reducing the interfacial resistance of the battery and improving the rate performance and cycle stability at room temperature and low temperature.

[0021] A second aspect of the present application provides a method for producing a solid electrolyte for a secondary battery, the method comprising the following steps: First tableting: The inorganic solid electrolyte powder is mixed with the pore-forming agent and compressed to obtain a porous layer precursor. Second tableting: The inorganic solid electrolyte powder is compressed to obtain a dense layer. Third tableting: The sequentially stacked porous layer precursors are compressed with the dense layer to obtain a solid electrolyte precursor. The solid electrolyte precursor is calcined to obtain a solid electrolyte, wherein the porous layer precursor is formed into a porous layer, the porosity of the porous layer being greater than the porosity of the dense layer.

[0022] The above-mentioned preparation method is simple and easy to operate, and the prepared solid electrolyte is advantageous in improving the interfacial wettability between the solid electrolyte and the positive electrode plate / negative electrode plate, thereby reducing the interfacial resistance of the battery and improving the rate performance and cycle stability at room temperature / low temperature of the battery.

[0023] In any embodiment, the pore-forming agent comprises one or more of activated carbon, carbon black, ethyl cellulose, starch, ammonium carbonate, ammonium bicarbonate, polyethylene glycol, polymethacrylic acid, polymethyl methacrylate.

[0024] The pore-forming agent is easily decomposed at high temperatures, leaving voids inside the porous layer, improving the porosity of the porous layer, making the porosity of the porous layer greater than that of the dense layer, and increasing the specific surface area of ​​the porous layer. The remaining carbon elements also improve the interfacial dynamics between the solid electrolyte and the positive and negative electrodes, reducing the interfacial resistance of the battery and improving the rate performance and cycle stability at room and low temperatures of the battery.

[0025] In any embodiment, the mass content of the pore-forming agent is 5% to 50% based on the total mass of the porous layer precursor.

[0026] Controlling the mass content of the pore-forming agent within an appropriate range can balance the ionic conductivity of the porous layer and the interfacial dynamics of the solid electrolyte, reduce the interfacial resistance of the battery, and improve the rate performance and cycle stability at room temperature / low temperature of the battery.

[0027] In any embodiment, the mass content of the dense layer is 30% to 70%, and optionally 50% to 70%, based on the total mass of the solid electrolyte precursor.

[0028] Controlling the mass content of the dense layer to 30% to 70% of the total mass of the solid electrolyte precursor can ensure the ionic conductivity of the solid electrolyte and simultaneously reduce the interfacial resistance of the battery, improving the rate performance and cycle stability at room and low temperatures. Controlling the mass content of the dense layer to 50% to 70% of the total mass of the solid electrolyte precursor can further reduce the interfacial resistance of the battery, further improving the rate performance and cycle stability at room and low temperatures.

[0029] In any embodiment, the firing conditions are firstly to keep the temperature at 400°C to 600°C for 0.5 to 4 hours, and then to keep the temperature at 800°C to 1300°C for 0.5 to 24 hours.

[0030] Appropriate firing temperature and firing time are favorable for sufficient release of the pore-forming agent, increasing the porosity of the porous layer, improving the specific surface area and ionic conductivity of the porous layer, improving the interfacial wettability between the solid electrolyte and the positive electrode plate / negative electrode plate, reducing the interfacial resistance of the battery, and improving the rate performance and normal / low temperature cycle stability of the battery.

[0031] In any embodiment, the pressure for the first tableting and the second tableting is 10 MPa to 50 MPa, and the pressure for the third tableting is 50 MPa to 300 MPa.

[0032] Controlling the pressures of the first tableting, the second tableting, and the third tableting within an appropriate range is advantageous for forming the solid electrolyte, and prevents or reduces detachment between the porous layer and the dense layer during the production process of the solid electrolyte.

[0033] In any embodiment, the particle size of the inorganic solid electrolyte powder is 1 μm to 10 μm.

[0034] Controlling the particle size of the inorganic solid electrolyte powder to 1 μm to 10 μm is advantageous for achieving uniform mixing between the inorganic solid electrolyte powder and the pore-forming agent, uniforming the pore distribution of the porous layer, reducing the interfacial resistance of the battery, and improving the rate performance and cycle stability at room and low temperatures of the battery. On the other hand, controlling the particle size of the inorganic solid electrolyte powder to 1 μm to 10 μm is advantageous for reducing the increase in tableting pressure due to excessively large particle size, thereby reducing equipment loss.

[0035] A third aspect of the present application provides a secondary battery, which includes a positive electrode plate, a negative electrode plate, and a solid electrolyte according to the first aspect or a solid electrolyte produced by the method for producing a solid electrolyte according to the second aspect.

[0036] In either embodiment, the secondary battery includes a positive electrode active material located within the pores of a porous layer on the positive electrode plate side of the solid electrolyte.

[0037] The positive electrode active material is distributed within the pores of the porous layer on the positive electrode plate side of the solid electrolyte, which, on the one hand, avoids or reduces the use of adhesives and improves the occupancy rate of the positive electrode active material and the dynamics of the positive electrode plate. On the other hand, the porous layer has a high specific surface area, and the positive electrode active material distributed within the pores of the porous layer increases the contact area between the positive electrode active material and the solid electrolyte, reducing the interfacial resistance of the battery and favorably improving the rate performance and cycle stability at room and low temperatures of the battery.

[0038] In any embodiment, the cathode active material is synthesized in situ in the porous layer of the solid electrolyte, and the in situ synthesis method includes at least one of hydrothermal, electrodeposition, sol-gel, electrospinning, chemical vapor deposition, physical vapor deposition, and immersion. The physical vapor deposition method includes at least one of vacuum evaporation, magnetron sputtering, ion sputtering, molecular beam epitaxy, and atomic layer deposition.

[0039] All of the above in situ synthesis methods can achieve distribution of the positive electrode active material in the pores of the porous layer of the solid electrolyte, and reduce the interfacial resistance between the positive electrode active material and the solid electrolyte.

[0040] In any embodiment, the positive electrode active material includes at least one of a transition metal layered oxide, a polyanion compound, and a Prussian blue compound, and optionally includes NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, Na(Cu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 )O2, Na 2 / 3 Ni 1 / 6 Mn 2 / 3 Cu 1 / 9 Mg 1 / 18 O2, Na4Fe3(PO4)2P2O7, NaFePO4, Na3V2(PO4)3, Na 1.9 It includes one or more of CoFe(CN)6, Na2NiFe(CN)6, and NaMnFe(CN)6.

[0041] Any of the above positive electrode active materials is advantageous in reducing the interface resistance of the battery and improving the rate performance and cycle stability at room temperature / low temperature of the battery.

[0042] In any embodiment, the surface of the positive electrode active material has a coating layer, and the coating layer includes one or more of a carbon material, ZrO, TiO, polyaniline, polypyrrole, poly(3,4-ethylenedioxythiophene), aluminum oxide, zinc oxide, titanium oxide, zirconium oxide, magnesium oxide, silicon oxide, lanthanum oxide, sodium fluoride, lithium fluoride, and aluminum fluoride. The carbon material includes one or more of amorphous carbon, graphite, and graphene.

[0043] A positive electrode active material including a coating layer is advantageous in improving the high voltage cycling stability and room temperature / low temperature cycling stability of a battery.

[0044] In any embodiment, the thickness of the coating layer is from 2 nm to 1000 nm, and optionally from 10 nm to 100 nm.

[0045] Controlling the thickness of the coating layer within an appropriate range is advantageous for improving the cycle stability and electrical performance at high voltage of the battery.

[0046] In either embodiment, the secondary battery includes a negative electrode active material located within the pores of a porous layer on the negative electrode plate side of the solid electrolyte.

[0047] The negative electrode active material is distributed in the pores of the porous layer on the negative electrode side of the solid electrolyte, which, on the one hand, improves the occupancy rate of the negative electrode active material, increases the charge / discharge capacity of the battery, and improves the interfacial dynamics between the solid electrolyte and the negative electrode plate. On the other hand, the porous layer has a high specific surface area, and the negative electrode active material distributed in the pores of the porous layer increases the contact area between the negative electrode active material and the solid electrolyte, reducing the interfacial resistance of the battery and favoring the rate performance and cycle stability at room and low temperatures of the battery.

[0048] In either embodiment, the negative electrode active material is filled into the pores of the porous layer of the solid electrolyte by hot injection.

[0049] The method of heat injection significantly improves the interfacial kinetic process.

[0050] In any embodiment, the negative electrode active material includes sodium metal or a sodium alloy, and optionally the sodium alloy includes any one of a sodium-potassium alloy, a sodium-potassium-lithium alloy, a sodium-magnesium alloy, and a sodium-zinc alloy.

[0051] In either embodiment, the secondary battery is a sodium secondary battery without a negative electrode.

[0052] In any embodiment, the solid electrolyte includes a conductive material located within pores of a porous layer on the positive electrode plate side and / or the negative electrode plate side of the solid electrolyte, the conductive material being selected from one or more of carbon nanotubes, graphite, graphene, and Super P.

[0053] The conductive material is located in the pores of the porous layer on the negative electrode plate side of the solid electrolyte, which is advantageous for increasing electronic conductivity.

[0054] In any embodiment, the negative electrode plate includes a negative electrode current collector and an undercoating disposed on at least one surface of the negative electrode current collector, the undercoating including one or more of carbon nanotubes, graphite, graphene, silver composite carbon nanoparticles, and tin composite carbon nanoparticles.

[0055] The undercoating not only has excellent electrical conductivity but also favors uniform deposition of metal ions on the surface of the current collector, improving the cycle performance and safety of the battery.

[0056] In any embodiment, the areal density of the undercoating is 5 g / m 2 ~50g / m 2 is.

[0057] Surface density is 5g / m 2 ~50g / m 2 The undercoating, which is favorable for a uniform distribution of nucleation sites, promotes uniform deposition of metal, and at the same time does not affect the electron transport behavior.

[0058] In either embodiment, the undercoating has a thickness of from 2 μm to 100 μm.

[0059] Controlling the thickness of the undercoating between 2 μm and 100 μm is beneficial to the uniform deposition of metal ions by providing sufficient nucleation sites, and can suppress dendrites.

[0060] A fourth aspect of the present application provides a battery module, which includes the secondary battery of the third aspect of the present application.

[0061] A fifth aspect of the present application provides a battery pack, which includes the secondary battery of the third aspect of the present application or the battery module of the fourth aspect of the present application.

[0062] A sixth aspect of the present application provides a power consumption device, the power consumption device including at least one of the secondary battery of the third aspect of the present application, the battery module of the fourth aspect of the present application, and the battery pack of the fifth aspect of the present application. [Brief explanation of the drawings]

[0063] [Figure 1] 1 is a schematic diagram of a secondary battery according to an embodiment of the present application; [Figure 2] FIG. 2 is an exploded view of the secondary battery shown in FIG. 1 according to the embodiment of the present application. [Figure 3] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 4] 1 is a schematic diagram of a battery pack according to an embodiment of the present application. [Figure 5] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application. [Figure 6] 1 is a schematic diagram of a power consumption device powered by a secondary battery according to an embodiment of the present application; DETAILED DESCRIPTION OF THE INVENTION

[0064] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the solid electrolyte, its manufacturing method, secondary battery, battery module, battery pack, and power consumption device of the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters or repeated description of structures that are actually the same may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0065] The "ranges" disclosed in this application are defined in the form of lower and upper limits. A given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive, and may be arbitrarily combined; i.e., any lower limit may be combined with any upper limit to form a single range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if 1 and 2 are listed as minimum range values ​​and 3, 4, and 5 are listed as maximum range values, the following ranges are also contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. Unless otherwise specified, the numerical range "ab" in this application is a shorthand notation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" represents a list of all real numbers between "0-5" already listed in this specification, and "0-5" is merely a shorthand representation of combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that this parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0066] Unless otherwise stated, all embodiments and optional embodiments in the present application can be combined with each other to form a new technical solution.

[0067] Unless otherwise stated, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0068] Unless otherwise specified, all steps in this application may be performed in order or randomly, and are preferably performed in order. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, when the method mentioned above may further include step (c), it means that step (c) may be added to the method in any order, and for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0069] Unless otherwise specified, the terms "comprise" and "comprises" used in this application may be open ended or closed ended. For example, the terms "comprise" and "comprises" may indicate that other components not listed may be further included or included, or that only the listed components may be included or included.

[0070] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, "A or B" is satisfied when A is true (or exists) and B is false (or does not exist), when A is false (or does not exist) but B is true (or exists), or when both A and B are true (or exist).

[0071] In general, inorganic solid electrolytes have become a popular research topic due to their excellent chemical stability and wide electrochemical stability window. However, inorganic solid electrolytes have difficulty forming good interfacial contact with electrodes, resulting in poor surface wettability, which affects the kinetic processes at the electrode / inorganic solid electrolyte interface and significantly reduces the overall battery rate performance. Therefore, it is necessary to develop new solid electrolytes to meet the application demands of new-generation electrochemical systems.

[0072] [Solid electrolyte] Based on this, the present application provides a solid electrolyte for a secondary battery, comprising a dense layer and a porous layer located on at least one side of the dense layer, wherein the porosity of the porous layer is greater than the porosity of the dense layer.

[0073] As can be appreciated, the porous layer may be located on at least one side of the dense layer, i.e., the porous layer may be located on one side of the dense layer or the porous layer may be located on both sides of the dense layer. The dense and porous layers may be in face-to-face contact, or may have an intervening layer between them.

[0074] In some embodiments, the solid electrolyte comprises a dense layer and one porous layer, the porous layer being located on one side of the dense layer facing the positive electrode plate.

[0075] In some embodiments, the solid electrolyte comprises a dense layer and one porous layer, the porous layer being located on one side of the dense layer facing the negative electrode plate.

[0076] In some embodiments, the solid electrolyte comprises a dense layer and two porous layers, the dense layer being located between the two porous layers.

[0077] The solid electrolyte includes a dense layer and a porous layer located on at least one side of the dense layer. The porosity of the porous layer is greater than that of the dense layer, which is beneficial for improving the interfacial wettability between the solid electrolyte and the positive and negative electrodes, thereby reducing the interfacial resistance of the battery and improving the rate performance and cycle stability at room and low temperatures. On the other hand, a porous layer is located on at least one side of the dense layer, and the porosity of the porous layer is greater than that of the dense layer, which is beneficial for increasing the specific surface area of ​​the solid electrolyte, improving the interfacial wettability between the solid electrolyte and the positive and negative electrodes, improving the kinetic process at the interface between the solid electrolyte and the positive and negative electrodes, and significantly improving the rate performance of the battery. On the other hand, a porous layer with a greater porosity than the dense layer is beneficial for reducing the interfacial resistance between the solid electrolyte and the positive and negative electrodes, thereby improving the cycle stability of the battery at room and low temperatures.

[0078] In some embodiments, the porous layer is disposed on the surface of the dense layer.

[0079] Forming a porous layer on the surface of a dense layer not only effectively reduces the interface resistance of the battery, but also has the advantage of improving the rate performance and cycle stability at room temperature / low temperature of the battery.

[0080] In some embodiments, there are two porous layers, each connected to two opposing surfaces of the dense layer.

[0081] Porous layers are provided on both opposing surfaces of the dense layer, one of which contacts the positive electrode plate and the other of which contacts the negative electrode plate, thereby simultaneously improving the interfacial dynamics between the solid electrolyte and the positive and negative electrode plates, reducing the interfacial resistance of the battery, and improving the rate performance and cycle stability at room and low temperatures of the battery.

[0082] In some embodiments, the thicknesses of the two porous layers respectively connected to the two opposite surfaces of the dense layer are the same, i.e., the solid electrolyte has a symmetrical structure.

[0083] In some embodiments, the thicknesses of the two porous layers respectively connected to the two opposite surfaces of the dense layer are different, i.e., the solid electrolyte has an asymmetric structure.

[0084] In some embodiments, the ratio of the thickness of any one of the porous layers to the dense layer is 0.5-7.5, and optionally 1-4.

[0085] In some embodiments, the ratio of the thickness of any one porous layer to the dense layer is optionally 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6.5, 7, or 7.5.

[0086] Controlling the thickness ratio of any one of the porous layers to the dense layer between 0.5 and 7.5 controls the electrochemical-mechanical effect and prevents the solid electrolyte from being deformed by mechanical stress during cycling, which would otherwise cause a decrease in battery cycling performance. This reduces the interfacial resistance of the battery, improving its rate performance and cycle stability at room and low temperatures, and is advantageous for achieving both mechanical and electrical performance of the solid electrolyte. Furthermore, controlling the thickness ratio of the porous layer to the dense layer between 1 and 4 ensures the ionic conductivity of the solid electrolyte while providing a larger specific surface area. This further reduces the battery's internal resistance, increases the specific surface area of ​​the porous layer, and optimizes the battery's dynamic performance.

[0087] In some embodiments, the dense layer has a thickness of 0.2 mm to 0.6 mm, and any one of the porous layers has a thickness of 0.3 mm to 1.5 mm. In some embodiments, the dense layer optionally has a thickness of 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, or 0.6 mm. In some embodiments, the porous layer optionally has a thickness of 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, or 1.5 mm.

[0088] The dense layer and the porous layer within this range can further improve the battery performance and prevent the battery from having too high internal resistance.

[0089] In some embodiments, the ionic conductivity of the porous layer is at least 10 times lower than the ionic conductivity of the dense layer.

[0090] In some embodiments, the ratio of the ionic conductivity of the porous layer to the ionic conductivity of the dense layer is optionally 1 / 9, 1 / 8, 1 / 7, 1 / 6, 1 / 5, 1 / 4, 1 / 3, 1 / 2, or 2 / 3.

[0091] In this specification, the ionic conductivity of the porous layer and the dense layer can be tested by selecting a method known in the art. For example, the ohmic impedance of a button battery (positive and negative electrodes are platinum or titanium sheets with the same area) is measured at 25°C using a 1470 multi-channel electrochemical workstation manufactured by Solartron, UK, in a frequency range of 1 Hz to 1 MHz with a perturbation signal of 5 mV, where the ionic conductivity is calculated as follows: (thickness of solid electrolyte) / (area of ​​platinum or titanium sheet × ohmic impedance of solid electrolyte).

[0092] The ionic conductivity of the porous layer is controlled to more than 1 / 10 of that of the dense layer, improving the interfacial dynamics between the solid electrolyte and the positive and negative electrodes while ensuring the ionic conductivity of the solid electrolyte, thereby achieving both the interfacial dynamics and ionic conductivity of the solid electrolyte.

[0093] In some embodiments, the ionic conductivity of the porous layer is 5×10 -4 S cm -1 ~2×10 -3 S cm -1 In some embodiments, the ionic conductivity of the porous layer is preferably 5×10 -4 S cm -1 , 6×10 -4 S cm -1 , 7×10 -4 S cm -1 , 8×10 -4 S cm -1 , 9×10 -4 S cm -1 , 1×10 -3 S cm -1 , 1.2 × 10 -3 S cm -1 , 1.4×10 -3 S cm -1 , 1.5×10 -3 S cm -1 , 1.6×10 -3 S cm -1 , 1.8×10 -3 S cm -1 Or 2×10 -3 S cm -1 is.

[0094] In some embodiments, the ionic conductivity of the dense layer is greater than or equal to 1×10 -3 S cm -1 ~1×10 -2 S cm -1 In some embodiments, the ionic conductivity of the dense layer is preferably 1×10 -3 S cm -1 , 1.5×10 -3 S cm -1 , 2 × 10 -3 S cm -1 , 2.5×10 -3 S cm -1 , 3×10 -3 S cm -1 , 3.5×10 -3 S cm -1 , 4×10 -3 S cm -1 , 4.5×10 -3 S cm -1 , 5×10 -3 S cm -1 , 5.5×10 -3 S cm -1 , 6×10 -3 S cm -1 , 6.5×10 -3 S cm -1 , 7×10 -3 S cm -1 , 7.5×10 -3 S cm -1 , 8×10 -3 S cm -1 , 8.5×10 -3 S cm -1 , 9×10 -3 S cm -1 , 9.5×10 -3 S cm -1 or 1 x 10 -2 S cm -1 is.

[0095] Controlling the ionic conductivity of the dense layer and the porous layer within an appropriate range provides the solid electrolyte with excellent ion transport ability, improving the electrical performance of the battery.

[0096] In some embodiments, the contact angle of molten sodium on the surface of the solid electrolyte porous layer is ≦90°, optionally ≦70°, In some embodiments, the contact angle of molten sodium on the surface of the solid electrolyte porous layer is optionally 90°, 85°, 80°, 75°, 70°, 60°, 50°, 40°, 30°, 20°, 10°, or 5°.

[0097] In this specification, the contact angle of molten sodium on the surface of a porous layer of a solid electrolyte can be tested by selecting a method known in the art, for example, by dropping molten sodium on the surface of a porous layer / dense layer / porous layer solid electrolyte or a porous layer / dense layer solid electrolyte, taking an image of the electrolyte surface with a high-resolution camera (Grasshopper GRAS-50S5M-C) equipped with a Fujinon HF75SA-1 lens, and measuring the contact angle using ImageJ software. The test process for the comparative example and other examples is the same as above.

[0098] The contact angle of molten sodium on the surface of the solid electrolyte porous layer is ≦90°, indicating better wettability between the solid electrolyte porous layer and molten sodium. Combining the porous layer with the negative active material improves the interfacial dynamics between the solid electrolyte and the positive and negative electrodes, reducing the interfacial resistance of the battery and improving its rate performance and room / low temperature cycling stability. The contact angle of molten sodium on the surface of the solid electrolyte porous layer is ≦70°, further reducing the interfacial resistance of the battery and improving its rate performance and room / low temperature cycling stability.

[0099] In some embodiments, both the dense layer and the porous layer comprise an inorganic solid electrolyte material, which comprises one or more of a sulfur-based electrolyte, a sodium fast-ion conductor, and an oxide electrolyte.

[0100] In some embodiments, the sulfur-based electrolyte is Na2S-P2S5, Na 11 Sn2PnX 12 , Na3Pny Pn' 1-y X z X' 4-z wherein Pn includes at least one of P and Sb, X includes at least one of S and Se, Pn' includes at least one of Si, Sn and Ge, and X' includes at least one of F, Br and Cl, and 0 <y≦1、0<z≦4である。

[0101] In some embodiments, y is optionally 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.

[0102] In some embodiments, z is optionally 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.4, 1.5, 1.6, 1.8, 2, 2.2, 2.4, 2.5, 2.6, 2.8, 3, 3.2, 3.4, 3.5, 3.6, 3.8, or 4.

[0103] In some embodiments, the sulfur-based electrolyte is Na 11 Sn2PS 12 , Na 11 Sn2PS 12 , Na 10 SnP2S 12 , Na 10 GeP2S 12 , Na 2.9375 PS 3.9375 Cl 0.0625 Includes.

[0104] In some embodiments, the sodium fast ion conductor is Na 3+x M y M' 2-y Si 2-z P z O 12 wherein M and M' may independently comprise at least one of Zr, Ca, Mg, Zn, La, Ti, and Nb; and 0≦x≦1, 0 <y≦2、0≦z<2である。

[0105] In some embodiments, x may alternatively be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.

[0106] In some embodiments, y is optionally 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, or 1.9.

[0107] In some embodiments, z is optionally 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, or 1.9.

[0108] In some embodiments, the sodium fast ion conductor solid electrolyte is Na 3.4 Zr 1.9 Zn 0.1 Si 2.2 P 0.8 O 12 , Na3Zr 1.75 Mg 0.25 SiPO 12 , Na 3.3 Zr 1.7 La 0.3 SiPO 12 , Na 3.1 Ca 0.05 Zr 1.95 SiPO 12 It includes at least one of the following.

[0109] In some embodiments, the oxide electrolyte includes at least one of Na-β-AlO, Na-β″-AlO, where Na-β-AlO includes β-NaO·11AlO, and Na-β″-AlO includes β″-NaO·5AlO.

[0110] In some embodiments, the oxide electrolyte further comprises an inorganic oxide, the inorganic oxide comprising one or more of Li2O, MgO, TiO2, ZrO2, YO3, MnO2, SiO2, and Fe2O3, and the mass content of the inorganic oxide is 0.5% to 30%, based on the total mass of the oxide electrolyte.

[0111] In some embodiments, the inorganic oxide mass content is optionally 0.5%, 1%, 5%, 7%, 10%, 12%, 15%, 18%, 20%, 23%, 25%, 28%, or 30% based on the total mass of the oxide electrolyte.

[0112] The above-mentioned sulfur-based electrolyte, sodium fast ion conductor, and oxide electrolyte are inorganic solid electrolyte materials for the dense layer and porous layer, and are all advantageous in reducing the interfacial resistance of the battery and improving the rate performance and cycle stability at room temperature and low temperature.

[0113] The present application further provides a method for manufacturing a solid electrolyte for a secondary battery, the method comprising the following steps: First tableting: The inorganic solid electrolyte powder is mixed with the pore-forming agent and compressed to obtain a porous layer precursor. Second tableting: The inorganic solid electrolyte powder is compressed to obtain a dense layer. Third tableting: The sequentially stacked porous layer precursors are compressed with the dense layer to obtain a solid electrolyte precursor. The solid electrolyte precursor is calcined to obtain a solid electrolyte, wherein the porous layer precursor is formed into a porous layer, the porosity of the porous layer being greater than the porosity of the dense layer.

[0114] As can be understood, the first and second tableting steps can be performed in any order. In some embodiments, a porous layer precursor is first produced, then an inorganic solid electrolyte powder is laid on the porous layer precursor and tableted a second time, resulting in a dense layer located on the surface of the porous layer precursor, and then tableted directly a third time. In some embodiments, a dense layer is first produced, then an inorganic solid electrolyte powder and a pore-forming agent are laid on the dense layer to obtain a porous layer precursor located on the surface of the dense layer, and then tableted directly a third time. In some embodiments, a porous layer precursor and a dense layer are separately produced, then the two are layered in the order of porous layer precursor / dense layer or porous layer precursor / dense layer / porous layer precursor, and then tableted and compacted a third time to obtain a solid electrolyte precursor. In some embodiments, the structure of the solid electrolyte precursor is porous layer precursor / dense layer. In some embodiments, the structure of the solid electrolyte precursor is porous layer precursor / dense layer / porous layer precursor.

[0115] The above-mentioned preparation method is simple and easy to operate, and the prepared solid electrolyte is advantageous in improving the interfacial wettability between the solid electrolyte and the positive electrode plate / negative electrode plate, thereby reducing the interfacial resistance of the battery and improving the rate performance and cycle stability at room temperature / low temperature of the battery.

[0116] In some embodiments, the pore-forming agent comprises one or more of activated carbon, carbon black, ethyl cellulose, starch, ammonium carbonate, ammonium bicarbonate, polyethylene glycol, polymethacrylic acid, polymethyl methacrylate.

[0117] The pore-forming agent is easily decomposed at high temperatures, leaving voids inside the porous layer, improving the porosity of the porous layer, making the porosity of the porous layer greater than that of the dense layer, and increasing the specific surface area of ​​the porous layer. The remaining carbon elements also improve the interfacial dynamics between the solid electrolyte and the positive and negative electrodes, reducing the interfacial resistance of the battery and improving the rate performance and cycle stability at room and low temperatures of the battery.

[0118] In some embodiments, the mass content of the pore-forming agent is 5% to 50% based on the total mass of the porous layer precursor.

[0119] In some embodiments, the mass content of the pore-forming agent is optionally 5%, 6%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 42%, 44%, 45%, 46%, 48%, or 50%, based on the total mass of the porous layer precursor.

[0120] Controlling the mass content of the pore-forming agent within an appropriate range can balance the ionic conductivity of the porous layer and the interfacial dynamics of the solid electrolyte, reduce the interfacial resistance of the battery, and improve the rate performance and cycle stability at room temperature / low temperature of the battery.

[0121] In some embodiments, based on the total mass of the solid electrolyte precursor, the mass content of the dense layer is 30% to 70%, and optionally 50% to 70%.

[0122] In some embodiments, the mass content of the dense layer is optionally 30%, 32%, 34%, 35%, 36%, 38%, 40%, 45%, 50%, 55%, 60%, 62%, 64%, 65%, 66%, 68%, or 70% based on the total mass of the solid electrolyte precursor.

[0123] Controlling the mass content of the dense layer to 30% to 70% of the total mass of the solid electrolyte precursor can ensure the ionic conductivity of the solid electrolyte and simultaneously reduce the interfacial resistance of the battery, improving the rate performance and cycle stability at room and low temperatures. Controlling the mass content of the dense layer to 50% to 70% of the total mass of the solid electrolyte precursor can further reduce the interfacial resistance of the battery, further improving the rate performance and cycle stability at room and low temperatures.

[0124] In some embodiments, the firing conditions are firstly maintaining the temperature at 400°C to 600°C for 0.5 hours to 4 hours, and then maintaining the temperature at 800°C to 1300°C for 0.5 hours to 24 hours.

[0125] In some embodiments, the firing conditions are first at 400° C. with an incubation time of 4 hours, then at 1300° C. with an incubation time of 0.5 hours.

[0126] In some embodiments, the firing conditions are first maintained at a temperature of 500° C. for 3 hours, and then maintained at a temperature of 1000° C. for 20 hours.

[0127] In some embodiments, the firing conditions include first maintaining the temperature at 600° C. for 0.5 hours, and then maintaining the temperature at 800° C. for 15 hours.

[0128] In some embodiments, the firing conditions include first maintaining the temperature at 500° C. for 3 hours, and then maintaining the temperature at 800° C. for 24 hours.

[0129] Appropriate firing temperature and firing time are favorable for sufficient combustion of the pore-forming agent, increasing the porosity of the porous layer, improving the specific surface area and ionic conductivity of the porous layer, improving the interfacial wettability between the solid electrolyte and the positive electrode plate / negative electrode plate, reducing the interfacial resistance of the battery, and improving the rate performance and cycle stability at room temperature / low temperature of the battery.

[0130] In some embodiments, the pressure for the first and second tableting is 10 MPa to 50 MPa, and the pressure for the third tableting is 50 MPa to 300 MPa.

[0131] In some embodiments, the pressure for the first and second compressions is optionally 10 MPa, 15 MPa, 20 MPa, 25 MPa, 30 MPa, 35 MPa, 40 MPa, 45 MPa, or 50 MPa, and the pressure for the third compression is optionally 50 MPa, 60 MPa, 80 MPa, 100 MPa, 150 MPa, 220 MPa, 230 MPa, 250 MPa, 260 MPa, 280 MPa, or 300 MPa.

[0132] Controlling the pressures of the first tableting, the second tableting, and the third tableting within an appropriate range is advantageous for forming the solid electrolyte, and prevents or reduces detachment between the porous layer and the dense layer during the production process of the solid electrolyte.

[0133] In some embodiments, the particle size of the inorganic solid electrolyte powder is 1 μm to 10 μm, and in some embodiments, the particle size of the inorganic solid electrolyte powder is optionally 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm.

[0134] Controlling the particle size of the inorganic solid electrolyte powder to 1 μm to 10 μm is advantageous for achieving uniform mixing between the inorganic solid electrolyte powder and the pore-forming agent, uniforming the pore distribution of the porous layer, reducing the interfacial resistance of the battery, and improving the rate performance and cycle stability at room and low temperatures of the battery. On the other hand, controlling the particle size of the inorganic solid electrolyte powder to 1 μm to 10 μm is advantageous for reducing the increase in tableting pressure due to excessively large particle size, thereby reducing equipment loss.

[0135] [Secondary battery] The secondary battery includes a positive electrode plate, a negative electrode plate, and a solid electrolyte according to some embodiments or a solid electrolyte produced by the method according to some embodiments.

[0136] In some embodiments, the secondary battery includes a positive electrode active material located within the pores of a porous layer on the positive electrode plate side of the solid electrolyte.

[0137] In this specification, the positive electrode active material being located in the pores of the porous layer on the positive electrode plate side of the solid electrolyte means that the positive electrode active material is located in the pores of the porous layer on one side of the solid electrolyte facing the positive electrode plate.

[0138] The positive electrode active material is distributed within the pores of the porous layer on the positive electrode plate side of the solid electrolyte, which, on the one hand, avoids or reduces the use of adhesives and improves the occupancy rate of the positive electrode active material and the dynamics of the positive electrode plate. On the other hand, the porous layer has a high specific surface area, and the positive electrode active material distributed within the pores of the porous layer increases the contact area between the positive electrode active material and the solid electrolyte, reducing the interfacial resistance of the battery and favorably improving the rate performance and cycle stability at room and low temperatures of the battery.

[0139] In some embodiments, the cathode active material is in situ synthesized in the porous layer of the solid electrolyte, the in situ synthesis method including at least one of hydrothermal, electrodeposition, sol-gel, electrospinning, chemical vapor deposition, physical vapor deposition, and immersion, and the physical vapor deposition method including at least one of vacuum evaporation, magnetron sputtering, ion sputtering, molecular beam epitaxy, and atomic layer deposition.

[0140] All of the above in situ synthesis methods can achieve distribution of the positive electrode active material within the pores of the porous layer of the solid electrolyte.

[0141] In some embodiments, the positive electrode active material comprises at least one of a transition metal layered oxide, a polyanion compound, and a Prussian blue compound, and NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, Na(Cu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 )O2, Na 2 / 3 Ni 1 / 6 Mn 2 / 3 Cu 1 / 9 Mg 1 / 18 O2, Na4Fe3(PO4)2P2O7, NaFePO4, Na3V2(PO4)3, Na 1.9 It includes one or more of CoFe(CN)6, Na2NiFe(CN)6, and NaMnFe(CN)6.

[0142] In some embodiments, the transition metal in the layered transition metal oxide may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Optionally, the layered transition metal oxide may be at least one of, for example, Na. x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu; <x≦1である。

[0143] In some embodiments, the polyanionic compound comprises a metal ion, a transition metal ion, and a tetrahedral (YO4) n- It may be a type of compound having an anionic unit, wherein the metal ion is optionally one of sodium ion, lithium ion, potassium ion, and zinc ion, the transition metal is optionally at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y is optionally at least one of P, S, and Si, and n is (YO4) n - represents the valence state.

[0144] In some embodiments, the Prussian blue-based compound may be a type of compound having a sodium ion, a transition metal ion, and a cyanide ion (CN-). The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The Prussian blue-based compound may be, for example, Na a Me b Me' c (CN)6, where Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn; <a≦2、0<b<1、0<c<1である。

[0145] In some embodiments, the surface of the positive electrode active material has a coating layer, and the coating layer includes one or more of a carbon material, ZrO, TiO, polyaniline, polypyrrole, poly(3,4-ethylenedioxythiophene), aluminum oxide, zinc oxide, titanium oxide, zirconium oxide, magnesium oxide, silicon oxide, lanthanum oxide, sodium fluoride, lithium fluoride, and aluminum fluoride, and the carbon material includes one or more of amorphous carbon, graphite, and graphene.

[0146] As used herein, the term "amorphous carbon" refers to a carbon material that has a very low degree of graphitization crystallization and is close to an amorphous form, and does not have a specific shape or periodic structure. By way of example, amorphous carbon includes, but is not limited to, carbon black, charcoal, or coke.

[0147] As used herein, the term "graphite" refers to allotropes of carbon, including natural and synthetic graphite.

[0148] As used herein, the term "graphene" refers to sp 2 It refers to a carbon material in which hybridized bonded carbon atoms are densely stacked in a single layer, two-dimensional honeycomb lattice structure. By way of example, graphene includes, but is not limited to, single-layer graphene or multi-layer graphene.

[0149] As used herein, the term "single-layer graphene" refers to a single-layer sheet-like structure in which carbon atoms are tightly and periodically arranged in a hexagonal honeycomb structure. For example, the thickness of single-layer graphene is only 0.3 nm to 0.4 nm.

[0150] As used herein, the term "multilayer graphene" refers to a graphene produced by stacking 2 to 10 single-layer graphene layers together to a total thickness of less than 100 nm.

[0151] A positive electrode active material including a coating layer is advantageous in improving the high voltage cycling stability and room temperature / low temperature cycling stability of a battery.

[0152] In some embodiments, the thickness of the coating layer is between 2 nm and 1000 nm, and optionally between 10 nm and 100 nm.

[0153] In some embodiments, the thickness of the coating layer is optionally 2 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, or 1000 nm.

[0154] Controlling the thickness of the coating layer within an appropriate range is advantageous for improving the cycle stability and electrical performance at high voltage of the battery.

[0155] In some embodiments, the secondary battery includes a negative electrode active material located within the pores of a porous layer on the negative electrode plate side of the solid electrolyte.

[0156] In this specification, the negative electrode active material being located in the pores of the porous layer on the negative electrode plate side of the solid electrolyte means that the negative electrode active material is located in the pores of the porous layer on one side of the solid electrolyte facing the negative electrode plate.

[0157] The negative electrode active material is distributed in the pores of the porous layer on the negative electrode side of the solid electrolyte, which, on the one hand, improves the occupancy rate of the negative electrode active material, increases the charge / discharge capacity of the battery, and improves the interfacial dynamics between the solid electrolyte and the negative electrode plate. On the other hand, the porous layer has a high specific surface area, and the negative electrode active material distributed in the pores of the porous layer increases the contact area between the negative electrode active material and the solid electrolyte, reducing the interfacial resistance of the battery and favoring the rate performance and cycle stability at room and low temperatures of the battery.

[0158] In some embodiments, the negative electrode active material is filled into the pores of the porous layer of the solid electrolyte by hot injection.

[0159] The method of heat injection significantly improves the interfacial kinetic process.

[0160] In some embodiments, the negative electrode active material comprises sodium metal or a sodium alloy, and optionally the sodium alloy comprises any one of a sodium-potassium alloy, a sodium-potassium-lithium alloy, a sodium-magnesium alloy, and a sodium-zinc alloy.

[0161] The sodium metal phase or sodium alloy may be pre-deposited on the negative electrode current collector as the negative electrode active material, or the sodium metal phase or sodium alloy may be filled into the pores of the porous layer of the solid electrolyte by hot injection. Compared to pre-depositing the sodium metal phase or sodium alloy on the negative electrode current collector as the negative electrode active material, the sodium metal phase or sodium alloy may be filled into the pores of the porous layer of the solid electrolyte by hot injection, which is advantageous for reducing the nucleation overpotential and interfacial resistance of the battery and improving the rate performance and room temperature / low temperature cycle performance of the battery.

[0162] Compared to sodium metal, sodium alloys have the advantage of lowering the melting point, lowering the nucleation overpotential, and increasing the critical current density.

[0163] In some embodiments, the secondary battery is a sodium secondary battery without a negative electrode.

[0164] Anode-less sodium secondary batteries contain only anode current collectors and no anode active material. During the initial charge, sodium ions gain electrons at the anode side and deposit as metallic sodium on the collector surface, forming a sodium metal phase. During discharge, the metallic sodium converts back to sodium ions and returns to the cathode, enabling cycle charging and discharging. Compared to sodium-ion batteries, anode-less sodium secondary batteries are not limited by the anode material and can therefore achieve higher energy density.

[0165] In some embodiments, the solid electrolyte comprises a conductive material, the conductive material being located within pores of a porous layer on the positive electrode plate side / negative electrode plate side of the solid electrolyte, and the conductive material being selected from one or more of carbon nanotubes, graphite, graphene, and Super P.

[0166] The conductive material is located in the pores of the porous layer on the negative electrode plate side of the solid electrolyte, which is advantageous in improving the conductivity of the porous layer and improving the uniformity of sodium deposition at the negative electrode in a sodium secondary battery without a negative electrode.

[0167] In some embodiments, the CB value of a sodium secondary battery without a negative electrode is 0.1 or less.

[0168] The CB value is the capacity per unit area of ​​the negative electrode plate in a secondary battery divided by the capacity per unit area of ​​the positive electrode plate. Since batteries without a negative electrode do not contain negative electrode active material, the capacity per unit area of ​​the negative electrode plate is relatively small, and the CB value of the secondary battery is 0.1 or less.

[0169] In some embodiments, the negative electrode plate includes a negative electrode current collector and an undercoating disposed on at least one surface of the negative electrode current collector, the undercoating including one or more of carbon nanotubes, graphite, graphene, silver composite carbon nanoparticles, and tin composite carbon nanoparticles.

[0170] As can be appreciated, the negative electrode plate may include only a negative electrode current collector and not include an active negative electrode material. The negative electrode plate may also include sodium metal or a sodium alloy as the active negative electrode material.

[0171] The undercoating not only has excellent electrical conductivity but also favors uniform deposition of metal ions on the surface of the current collector, improving the cycle performance and safety of the battery.

[0172] In some embodiments, the negative electrode current collector may employ a metal foil sheet or a composite current collector. For example, aluminum foil or copper foil may be used as the metal foil sheet. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0173] In some embodiments, the areal density of the undercoating is 5 g / m 2 ~50g / m 2 is.

[0174] In some embodiments, the areal density of the undercoating is optionally 5 g / m 2 , 10g / m 2 , 15g / m 2 , 20g / m 2 , 25g / m 2 , 30g / m 2 , 35g / m 2 , 40g / m 2 , 45g / m 2 or 50g / m 2 be.

[0175] Surface density is 5g / m 2 ~50g / m 2 The undercoating, which is favorable for a uniform distribution of nucleation sites, promotes uniform deposition of metal, and at the same time does not affect the electron transport behavior.

[0176] In some embodiments, the undercoating has a thickness of between 2 μm and 100 μm.

[0177] In some embodiments, the thickness of the undercoating is optionally 2 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, or 100 μm.

[0178] Controlling the thickness of the undercoating between 2 μm and 100 μm is beneficial to the uniform deposition of metal ions by providing sufficient nucleation sites, and can suppress dendrites.

[0179] In some embodiments, the positive electrode plate, the negative electrode plate, and the above-mentioned solid electrolyte can be fabricated into an electrode assembly by a winding process or a lamination process.

[0180] In some embodiments, the secondary battery may include an exterior body, which may be used to package the electrode assembly and the electrolyte.

[0181] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a pouch, such as a bag-shaped pouch. The pouch may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0182] The present application does not particularly limit the shape of the secondary battery, and it may be cylindrical, rectangular, or any other shape. For example, Fig. 1 shows an example of a rectangular secondary battery 5, and Fig. 2 is an exploded view of the secondary battery 5.

[0183] In some embodiments, referring to FIG. 2 , the exterior body may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and side plate together form a surrounding accommodating cavity. The case 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can be installed to cover the opening to seal the accommodating cavity. The positive electrode plate, the negative electrode plate, and the separator may be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the accommodating cavity. An electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and can be selected by those skilled in the art according to specific actual needs.

[0184] In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0185] Fig. 3 shows an example of a battery module 4. Referring to Fig. 3, the battery module 4 may include a plurality of secondary batteries 5 arranged in order along the longitudinal direction of the battery module 4. Of course, the batteries may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fixed by fasteners.

[0186] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of secondary batteries 5 are accommodated in this accommodating space.

[0187] In some embodiments, the battery modules may be assembled into a battery pack, and the battery pack may include one or more battery modules, the specific number of which may be selected by those skilled in the art depending on the application and capacity of the battery pack.

[0188] 4 and 5 show an example of a battery pack 1. Referring to FIGS. 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 may be provided with a lid on the lower housing 3 to form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0189] The present application also provides a power consuming device, the power consuming device including at least one of the secondary battery, battery module, or battery pack according to the present application. The secondary battery, battery module, or battery pack may be used as a power source for the power consuming device or as an energy storage unit for the power consuming device. The power consuming device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0190] The power consumption device can be selected from a secondary battery, a battery module, or a battery pack depending on its usage needs.

[0191] 6 shows an example of a power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the demand for high power output and high energy density of the secondary battery of the power consuming device, a battery pack or battery module can be employed.

[0192] Other examples of the device may include a mobile phone, a tablet computer, a laptop computer, etc. These devices are generally required to be thin and lightweight, and may use a secondary battery as a power source.

[0193] Example The following examples of the present application are described. The examples described below are illustrative and are used only to interpret the present application and should not be understood as limitations on the present application. Unless specific techniques or conditions are specified in the examples, they are carried out according to the techniques or conditions described in literature in the field or according to the product instructions. Unless the manufacturer is specified, the reagents or equipment used are all commercially available products.

[0194] 1. Manufacturing method Example 1 1) Production of solid electrolytes Inorganic solid electrolyte powder Na with particle size of 20 μm 3.4 Zr 1.9 Zn 0.1 Si 2.2 P 0.8 O 12 The mixture was uniformly mixed with 20 wt. % of carbon black to obtain a mixed powder, and a portion of the mixed powder was spread evenly on a mold and flattened at 20 MPa to obtain a porous layer precursor. Inorganic solid electrolyte powder Na with particle size of 20 μm 3.4 Zr 1.9 Zn 0.1 Si 2.2 P 0.8 O 12 The mixture was spread evenly on the porous layer precursor and flattened at 20 MPa to obtain a dense layer. The remaining mixed powder was spread evenly on the dense layer and flattened at 20 MPa to obtain a porous layer precursor. The porous layer precursor / dense layer / porous layer precursor is planarized at 200 MPa to obtain a solid electrolyte precursor, wherein the mass of the dense layer accounts for 60% of the total mass of the solid electrolyte precursor; The solid electrolyte precursor was placed in a muffle furnace and first kept at 500°C for 3 hours, then kept at 1000°C for 20 hours to obtain a three-layered solid electrolyte.

[0195] Here, the dense layer was 0.4 mm thick, the porous layers on both sides of the dense layer were each 0.6 mm thick, and the thickness ratio of the porous layer to the dense layer was 1.5. The contact angle of molten sodium with the solid electrolyte porous layer was 65°, and the contact angle of molten sodium with the solid electrolyte dense layer was 89°.

[0196] 2) Manufacturing of positive electrode plates Carbon nanotubes and carboxymethyl cellulose (CMC) were added to deionized water in a mass ratio of 1:0.4 and stirred to form a uniform slurry. The slurry was then applied to the surface of the aluminum foil positive electrode current collector, which was then transferred to a vacuum oven to dry completely and then punched out to obtain a positive electrode plate without a positive electrode structure.

[0197] 3) Manufacturing of negative electrode plate: Carbon nanotubes and carboxymethyl cellulose (CMC) were added to deionized water in a mass ratio of 1:0.4 and stirred to form a uniform slurry. The slurry was then applied to the surface of the negative electrode current collector copper foil, which was then transferred to a vacuum oven to completely dry and then punched to obtain a negative electrode plate without a negative electrode structure, where the areal density of the undercoating was 10 g / m. 2 where the thickness of the undercoating is 5 μm.

[0198] 4) Separator A polypropylene film was used as the separator.

[0199] 5) Battery manufacturing First, carbon-coated sodium iron pyrophosphate (Na4Fe3(PO4)2P2O7 / C) with a particle size smaller than 10 μm is dispersed in an ethylene glycol dimethyl ether solvent, and then the carbon-coated sodium iron pyrophosphate (Na4Fe3(PO4)2P2O7 / C) of the positive electrode active material is introduced into the positive electrode porous layer by the immersion method so that the corresponding voids can be filled. First, the carbon nanotubes are dispersed in an ethylene glycol dimethyl ether solvent, and then dropped onto the porous layer on the negative solid electrolyte electrode plate side using a dipping method. The dipping is continued for more than 5 hours and heated at 60°C, so that the carbon nanotubes can be inserted into the porous layer on the negative solid electrolyte electrode side and fill the corresponding voids.

[0200] The positive electrode plate, solid electrolyte, and negative electrode plate were stacked in this order and then wound to obtain a bare cell. A tab was welded to the bare cell, and the bare cell was placed in an aluminum case and baked at 80°C to remove water, and then sealed to obtain an uncharged battery. The uncharged battery was further subjected to steps such as standing, hot pressing, cold pressing, chemical formation, shaping, and capacity testing to obtain the sodium secondary battery product without a negative electrode of Example 1.

[0201] Example 2 The battery of Example 2 was manufactured using a method similar to that of Example 1, but the type of solid electrolyte was adjusted. The specific parameters are as shown in Table 1.

[0202] Example 3 Example 3 is a sodium metal secondary battery, and its manufacturing method is basically the same as that of Example 2, except that sodium metal is injected into the pores of the porous layer on the solid electrolyte negative electrode plate side using a thermal injection method, and the specific parameters are as shown in Table 1.

[0203] Examples 4-5 Examples 4 and 5 are sodium metal secondary batteries, and the manufacturing method thereof is basically the same as that of Example 3. The difference is that in Example 4, a sodium-potassium-lithium alloy is injected into the negative electrode-side porous layer, and the mass ratio of the three is 2:3:5; and in Example 5, a sodium-potassium alloy is injected into the negative electrode-side porous layer, and the mass ratio of the two is 2:3; the specific parameters are as shown in Table 1.

[0204] Example 6 The manufacturing methods of Example 6 and Example 1 are basically the same, with the difference being that the type of solid electrolyte was adjusted. The specific parameters are as shown in Table 1.

[0205] Examples 7-8 The manufacturing method of Examples 7 to 8 is basically the same as that of Example 1, except that the type of positive electrode active material was adjusted. Here, the thickness of the coating layer of Example 8 is 30 nm, and the specific parameters are as shown in Table 1.

[0206] Examples 9 to 11 Examples 9 to 11 are sodium metal secondary batteries, and the manufacturing method thereof is basically the same as that of Example 1. The differences are that in Example 9, sodium metal is injected into the pores of the porous layer on the solid electrolyte negative electrode plate side using a thermal injection method, in Example 10, a sodium-potassium-lithium alloy is injected into the negative electrode side porous layer, and the mass ratio of the three is 2:3:5, and in Example 11, a sodium-potassium alloy is injected into the negative electrode side porous layer, and the mass ratio of the two is 2:3, and the specific parameters are as shown in Table 1.

[0207] Examples 12 to 19 Examples 12 to 19 are basically the same as the manufacturing method of Example 1, but the thickness ratio of the porous layer / dense layer or the ionic conductivity ratio of the porous layer / dense layer is adjusted, and the specific parameters are as shown in Table 2.

[0208] Example 20 The manufacturing methods of Example 20 and Example 1 are basically the same, except that a positive electrode active material and a conductive agent are mixed to prepare a slurry, which is then applied to the positive electrode current collector, and the specific parameters are as shown in Table 1.

[0209] Example 21 The manufacturing methods of Examples 21 and 9 are basically the same, except that a positive electrode active material and a conductive agent are mixed to prepare a slurry, which is then applied to the positive electrode current collector, and the specific parameters are as shown in Table 2.

[0210] Example 22 The manufacturing methods of Example 22 and Example 10 are basically the same, except that a positive electrode active material and a conductive agent are mixed to prepare a slurry, which is then applied to the positive electrode current collector, and the specific parameters are as shown in Table 2.

[0211] Example 23 The manufacturing methods of Example 23 and Example 11 are basically the same, except that a positive electrode active material and a conductive agent are mixed to prepare a slurry, which is then applied to the positive electrode current collector, and the specific parameters are as shown in Table 2.

[0212] Examples 24 to 27 The manufacturing methods of Examples 24 to 27 are basically the same as those of Example 1, except that in Examples 24 to 27, the solid electrolyte has a porous layer on only one side of the dense layer, i.e., the solid electrolyte only includes the porous layer on the positive electrode plate side, and the positive electrode active material is distributed in the porous layer. The thicknesses of the porous layer and the dense layer are the same as those of each layer of the solid electrolyte in Example 1, and the negative electrode plate is assembled in contact with the dense layer of the solid electrolyte. The specific parameters are as shown in Table 2.

[0213] Comparative Examples 1 to 8 The battery manufacturing method in Comparative Example 1-8 was almost the same as that in Example 1, but the solid electrolyte had only one dense layer, the thickness of which was the same as that of the dense layer of the solid electrolyte in Example 1.

[0214] 2. Performance test 1, solid electrolyte 1) Sodium ion conductivity Electrochemical AC impedance tests were performed on the porous layer and the dense layer, respectively. The ohmic impedance of the button battery (positive and negative electrodes were platinum or titanium sheets with the same area) was measured at 25°C using a Solartron 1470 multi-channel electrochemical workstation (UK). The frequency range was 1 Hz-1 MHz, the perturbation signal was 5 mV, and the ionic conductivity was calculated as follows: (thickness of solid electrolyte) / (area of ​​platinum or titanium sheet × ohmic impedance of solid electrolyte). The test process for the comparative example and other examples was the same as above.

[0215] 2) Contact angle test After dropping molten sodium onto the surface of the solid electrolyte, an image of the electrolyte surface was taken with a high-resolution camera (Grasshopper GRAS-50S5M-C) equipped with a Fujinon HF75SA-1 lens, and the contact angle was measured using ImageJ software. The test process for the comparative example and other examples was the same as above.

[0216] 2. Battery performance test 1) Nucleation overpotential test The test process for nucleation overpotential is as follows: at 25°C, in a three-electrode battery system, the carbon nanotube-coated aluminum current collector is used as the working electrode, a sodium metal sheet is used as the counter electrode, and another sodium metal sheet is used as the reference electrode, and the current is 0.1 mA / cm 2 at a constant current of 0.3mAh / cm 2 The most negative potential obtained during the process was recorded as the nucleation overpotential. The test process for the comparative example and other examples was the same as above.

[0217] 2) Room temperature / low temperature cycle performance test The test process for room temperature / low temperature cycling performance was as follows: At 25°C / -10°C, the fabricated battery was charged at a constant current of 1C to 3.7V (carbon-coated sodium iron pyrophosphate cathode material) or 4.0V (transition metal layered oxide cathode material), and then discharged at 1C to 2.5V. The resulting capacity was designated as the initial capacity (C0). The above steps were repeated for the same battery, and the battery's discharge capacity (Cn) after the nth cycle was recorded. The battery capacity retention rate after each cycle was calculated as Pn = Cn / C0 × 100%, and the number of cycles at which Pn decreased to 80% was recorded. The test process for the comparative example and other examples was the same as above.

[0218] 3) Interface resistance test The interfacial resistance test process is as follows: an electrochemical AC impedance test is performed on the assembled whole battery. The AC impedance spectrum of the whole battery is measured at 25°C using a 1470 multi-channel electrochemical workstation manufactured by Solartron, UK, with a frequency range of 1 Hz-1 MHz and a perturbation signal of 5 mV. After the relevant electrochemical impedance spectrum is obtained, it is fitted using Zview software, and the capacitive reactance value is found to be 1×10. -7 and 1×10 -5 The diameter obtained after fitting to the arc between the points is taken as the interface resistance. The test process for the comparative example and other examples is the same as above.

[0219] 4) Rate performance test The test process for rate performance is as follows: At 25°C, the fabricated battery is placed in a 25°C thermostatic box and allowed to stand for 4 hours to allow the battery to reach a constant temperature. After the battery has reached a constant temperature, it is charged at 25°C at a constant current of 1C to 3.7V / 4V, then discharged at a constant current of 1C to 2.5V, cycled 5 times and allowed to stand for 5 minutes, then charged at a constant current of 2C to 3.7V / 4V, cycled 5 times and allowed to stand for 5 minutes, then discharged at a constant current of 2C to 2.5V and allowed to stand for 5 minutes. The 2C discharge capacity C2 is obtained, and the charge / discharge current is then increased to nC. The corresponding discharge capacity is recorded as Cn. The rate R is recorded, and the magnitude of the charge / discharge current when (R=C1 / Cn×100%) is just below 50% is recorded.

[0220] 3. Analysis of the test results of each example and comparative example According to the above method, the batteries of each example and comparative example were manufactured, and the performance parameters of each item were measured. The results are shown in Tables 1, 2 and 3 below.

[0221] [Table 1-1] [Table 1-2] [Table 1-3] [Table 1-4]

[0222] [Table 2-1] [Table 2-2] [Table 2-3] [Table 2-4]

[0223] [Table 3-1] [Table 3-2] [Table 3-3] [Table 3-4]

[0224] The above results indicate that the solid electrolytes for secondary batteries in Examples 1 to 27 all included a dense layer and a porous layer located on at least one side of the dense layer, and the porosity of the porous layer was greater than that of the dense layer. Comparisons of Examples 1, 12 to 20, and 24 with Comparative Example 1, Example 2 with Comparative Example 2, Example 6 with Comparative Example 3, Example 7 with Comparative Example 4, Example 8 with Comparative Example 5, Examples 9, 21, and 25 with Comparative Example 6, Examples 10, 22, and 26 with Comparative Example 7, and Examples 11, 23, and 27 with Comparative Example 8 reveal that, compared with conventional solid electrolytes including only a single dense layer, the solid electrolytes of the present application include a dense layer and a porous layer located on at least one side of the dense layer, which improves the number of cycles at 80% capacity of the battery at 25°C and -10°C, reduces the interfacial resistance of the battery, and improves the charge / discharge rate at 50% discharge capacity when the discharge capacity is 1C, thereby improving the electrical performance of the battery and expanding the range of battery applications.

[0225] As can be seen from comparisons of Examples 1, 12 to 20, and 24 with Comparative Example 1, Example 2 with Comparative Example 2, Example 6 with Comparative Example 3, Example 7 with Comparative Example 4, and Example 8 with Comparative Example 5, for sodium secondary batteries without a negative electrode, compared to conventional solid electrolytes including only one dense layer, the present application includes a solid electrolyte including a dense layer and a porous layer located on at least one side of the dense layer, which is advantageous in reducing the nucleation overpotential of the battery, improving the number of cycles at 80% capacity of the battery at 25°C and -10°C, significantly reducing the interfacial resistance of the battery, and improving the charge / discharge rate at 50% discharge capacity when the discharge capacity is 1C.

[0226] As can be seen from the comparison of Examples 9, 21, and 25 with Comparative Example 6, Examples 10, 22, and 26 with Comparative Example 7, and Examples 11, 23, and 27 with Comparative Example 8, compared to the conventional solid electrolyte containing only one dense layer, the present invention includes a solid electrolyte containing a dense layer and a porous layer located on at least one side of the dense layer, which is advantageous for sodium metal secondary batteries in that it significantly improves the number of cycles at 80% capacity at 25°C and -10°C, reduces the interfacial resistance of the battery, and significantly improves the charge / discharge rate at 50% discharge capacity when the discharge capacity is 1C.

[0227] As can be seen from the comparison between Example 1 and Examples 2 and 6, β-Na2O·11Al2O3 or Na 11 Sn2P2S 12 Compared with inorganic solid electrolyte materials containing Na 3.4 M 1.9 M' 0.1 Si 2.2 P 0.8 O 12 The inorganic solid electrolyte material containing the compound (I) is further advantageous in reducing the nucleation overpotential of the battery and improving the number of cycles at 80% capacity of the battery at 25°C and -10°C.

[0228] As can be seen from the comparison between Example 1 and Examples 7 and 8, Na(Cu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 ) Na coated with O2 or ZrO2, TiO2 2 / 3 Ni 1 / 6 Mn2 / 3 Cu 1 / 9 Mg 1 / 18 Compared with using O2 as the positive electrode active material, using Na4Fe3(PO4)2P2O7 as the positive electrode active material is advantageous in improving the number of cycles at 80% capacity of the battery at 25°C and -10°C, reducing the interface resistance of the battery, and improving the charge / discharge rate at 50% discharge capacity when the discharge capacity is 1C.

[0229] As can be seen from the comparison between Example 8 and Example 7, Na(Cu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 ) Compared to using O2 as the positive electrode active material, Na coated with ZrO2 and TiO2 2 / 3 Ni 1 / 6 Mn 2 / 3 Cu 1 / 9 Mg 1 / 18 Using O2 as the positive electrode active material is advantageous in improving the number of cycles at 80% capacity of the battery at 25°C and -10°C.

[0230] As can be seen from the comparisons between Examples 1 and 24, between Examples 9 and 25, between Examples 10 and 26, and between Examples 11 and 27, compared to a secondary battery without a negative electrode or a sodium metal secondary battery in which the solid electrolyte includes a dense layer and a porous layer located on the positive electrode plate side, the solid electrolyte including a dense layer, a porous layer located on the positive electrode plate side, and a porous layer located on the negative electrode plate side is advantageous in reducing the nucleation overpotential of the battery, improving the number of cycles at 80% capacity of the battery at 25°C and -10°C, reducing the interfacial resistance of the battery, and improving the charge / discharge rate at 50% discharge capacity when the discharge capacity is 1C.

[0231] As can be seen from a comparison between Examples 4 and 5 and Example 3, between Examples 10 and 11 and Example 9, between Examples 22 and 23 and Example 21, and between Examples 26 and 27 and Example 25, using a sodium-potassium-lithium alloy or a sodium-potassium alloy as the negative electrode active material is advantageous in reducing the nucleation overpotential of the battery, improving the number of cycles at 80% capacity of the battery at 25°C and -10°C, and reducing the interface resistance of the battery, compared to using sodium metal as the negative electrode active material.

[0232] As can be seen from the comparison between Example 9 and Example 3, and Example 10 and Example 4 and Example 5, for sodium metal secondary batteries, the inorganic solid electrolyte material containing β-Na2O·11Al2O3 is superior to the inorganic solid electrolyte material containing Na 3.4 M 1.9 M' 0.1 Si 2.2 P 0.8 O 12 The inorganic solid electrolyte material containing the inorganic solid electrolyte material is further advantageous in reducing the nucleation overpotential of the battery, improving the number of cycles at 80% capacity of the battery at 25°C and -10°C, reducing the interfacial resistance of the battery, and improving the charge / discharge rate at 50% discharge capacity when the discharge capacity is 1C.

[0233] As can be seen from the comparison between Example 1 and Example 20, Example 9 and Example 21, Example 10 and Example 22, and Example 23, the Na 3.4 M 1.9 M' 0.1 Si 2.2 P 0.8 O 12 Compared to preparing the positive electrode active material and conductive agent into a positive electrode slurry and applying it to the current collector, 3.4 M 1.9 M' 0.1 Si 2.2 P 0.8 O 12 Filling the positive electrode active material into the pores of the porous layer in contact with the positive electrode plate is also advantageous in improving the number of cycles at 80% capacity of the battery at 25°C and -10°C, reducing the interface resistance of the battery, and improving the charge / discharge rate at 50% discharge capacity when the discharge capacity is 1C.

[0234] As can be seen from a comparison between Examples 12 to 15 and Comparative Example 1, controlling the thickness ratio of any one of the porous layers to the dense layer to 0.5 to 7.5 is advantageous in reducing the nucleation overpotential of the battery, improving the number of cycles at 80% capacity of the battery at 25°C and -10°C, reducing the interfacial resistance of the battery, and improving the charge / discharge rate at 50% discharge capacity when the discharge capacity is 1 C. Furthermore, as can be seen from a comparison between Examples 13 and 14 and Examples 12 and 15, controlling the thickness ratio of any one of the porous layers to the dense layer to 1 to 4 can achieve both good interfacial resistance and good cycle performance of the battery.

[0235] As can be seen from a comparison between Examples 16 to 19 and Comparative Example 1, controlling the ionic conductivity of the porous layer to at least 1 / 10 of the ionic conductivity of the dense layer is advantageous in reducing the nucleation overpotential of the battery, improving the number of cycles at 80% capacity of the battery at 25°C and -10°C, reducing the interfacial resistance of the battery, and improving the charge / discharge rate at 50% discharge capacity when the discharge capacity is 1C.

[0236] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiment that has substantially the same configuration as the technical idea and achieves the same effects within the scope of the technical solution of the present application is included within the technical scope of the present application. In addition, various modifications that a person skilled in the art can make to the embodiments and other methods configured by combining some of the components of the embodiments are also included within the scope of the present application, as long as they do not deviate from the spirit of the present application. [Explanation of symbols]

[0237] 1: battery pack, 2: upper housing, 3: lower housing, 4: battery module, 5: secondary battery, 51: case, 52: electrode assembly, 53: cover plate.

Claims

1. 1. A solid electrolyte for a secondary battery, comprising: a dense layer; and a porous layer located on at least one side of the dense layer, wherein the porosity of the porous layer is greater than the porosity of the dense layer.

2. The solid electrolyte according to claim 1 , wherein the porous layer is disposed on the surface of the dense layer.

3. 3. The solid electrolyte according to claim 1, wherein the number of said porous layers is two, and said porous layers are connected to two opposing surfaces of said dense layer, respectively.

4. 4. The solid electrolyte according to claim 1, wherein the thickness ratio of any one of the porous layers to the dense layer is 0.5 to 7.5, and optionally 1 to 4.

5. 5. The solid electrolyte according to claim 1, wherein the ionic conductivity of the porous layer is at least 1 / 10 of the ionic conductivity of the dense layer.

6. 6. The solid electrolyte according to claim 1, wherein the contact angle of molten sodium on the surface of the solid electrolyte porous layer is ≦90°, and optionally ≦70°.

7. 7. The solid electrolyte of claim 1, wherein the dense layer and the porous layer both comprise an inorganic solid electrolyte material, the inorganic solid electrolyte material comprising one or more of a sulfur-based electrolyte, a sodium fast ion conductor, and an oxide electrolyte.

8. The sulfur-based electrolyte is Na ２ S-P ２ S ５ , Na １１ Sn ２ PnX １２ , Na ３ Pn ｙ Pn' １－ｙ X ｚ X' ４－ｚ wherein Pn comprises at least one of P and Sb, X comprises at least one of S and Se, Pn′ comprises at least one of Si, Sn and Ge, and X′ comprises at least one of F, Br and Cl, and 0<y≦1, 0<z≦4; The sodium fast ion conductor is Na ３＋ｘ M ｙ M' ２－ｙ Si ２－ｚ P ｚ O １２ wherein M and M′ may independently comprise at least one of Zr, Ca, Mg, Zn, La, Ti, Nb, and 0≦x≦1, 0<y≦2, and 0≦z<2; The oxide electrolyte is Na-β-Al ２ O ３ , Na-β″-Al ２ O ３ and the Na-β-Al ２ O ３ is β-Na ２ O.11Al ２ O ３ and the Na-β″-Al ２ O ３ is β″-Na ２ O.5Al ２ O ３ Optionally, the oxide electrolyte further comprises an inorganic oxide, and the inorganic oxide comprises Li ２ O, MgO, TiO ２ , ZrO ２ , Y ２ O ３ , MnO ２ , SiO ２ , Fe ２ O ３ 8. The solid electrolyte according to claim 7, wherein the inorganic oxide comprises one or more of the following:

9. A method for producing a solid electrolyte for a secondary battery, comprising the steps of: First tableting: The inorganic solid electrolyte powder is mixed with the pore-forming agent and compressed to obtain a porous layer precursor. Second tableting: Compress the inorganic solid electrolyte powder to obtain a dense layer; Third tableting: The porous layer precursor and the dense layer precursor are compressed together to obtain a solid electrolyte precursor. a method for producing a solid electrolyte for a secondary battery, the method comprising: calcining the solid electrolyte precursor to obtain the solid electrolyte; and forming the porous layer precursor into a porous layer, the porous layer having a porosity greater than the porosity of the dense layer.

10. 10. The method for producing a solid electrolyte according to claim 9, wherein the pore-forming agent comprises one or more of activated carbon, carbon black, ethyl cellulose, starch, ammonium carbonate, ammonium bicarbonate, polyethylene glycol, polymethacrylic acid, and polymethyl methacrylate.

11. 11. The method for producing a solid electrolyte according to claim 9, wherein the mass content of the pore-forming agent is 5% to 50% based on the total mass of the porous layer precursor.

12. 12. The method for producing a solid electrolyte according to claim 9, wherein a mass content of the dense layer is 30% to 70%, and optionally 50% to 70%, based on a total mass of the solid electrolyte precursor.

13. The manufacturing method according to any one of claims 9 to 12, characterized in that the firing conditions are firstly to keep the temperature at 400 ° C to 600 ° C for 0.5 h to 4 h, and then to keep the temperature at 800 ° C to 1300 ° C for 0.5 h to 24 h.

14. The method for producing a solid electrolyte according to any one of claims 9 to 13, wherein the pressures of the first tableting and the second tableting are 10 MPa to 50 MPa, and the pressure of the third tableting is 50 MPa to 300 MPa.

15. 15. The method for producing a solid electrolyte according to claim 9, wherein the inorganic solid electrolyte powder has a particle size of 1 μm to 10 μm.

16. 16. A secondary battery comprising: a positive electrode plate; a negative electrode plate; and the solid electrolyte according to claim 1 or 8, or a solid electrolyte produced by the method for producing a solid electrolyte according to claim 9.

17. 17. The secondary battery according to claim 16, wherein the secondary battery includes a positive electrode active material located in pores of a porous layer of the solid electrolyte on the positive electrode plate side.

18. 18. The secondary battery of claim 17, wherein the positive electrode active material is in situ synthesized in the porous layer of the solid electrolyte, the in situ synthesis method including at least one of a hydrothermal method, an electrodeposition method, a sol-gel method, an electrospinning method, a chemical vapor deposition method, a physical vapor deposition method, and an immersion method, and the physical vapor deposition method including at least one of a vacuum evaporation method, a magnetron sputtering method, an ion sputtering method, a molecular beam epitaxy method, and an atomic layer deposition method.

19. The positive electrode active material includes at least one of a transition metal layered oxide, a polyanion compound, and a Prussian blue compound, and optionally includes NaNi １／３ Fe １／３ Mn １／３ O ２ , Na(Cu １／９ Ni ２／９ Fe １／３ Mn １／３ ) O ２ , Na ２／３ Ni １／６ Mn ２／３ Cu １／９ Mg １／１８ O ２ , Na ４ Fe ３ (P.O. ４ ) ２ P ２ O ７ , NaFePO ４ , Na ３ V ２ (P.O. ４ ) ３ , Na １．９ CoFe(CN) ６ , Na ２ NiFe(CN) ６ , NaMnFe(CN) ６ 19. The secondary battery according to claim 17, wherein the secondary battery comprises one or more of the following:

20. The surface of the positive electrode active material has a coating layer, and the coating layer contains a carbon material, ZrO ２ , TiO ２ 20. The secondary battery according to any one of claims 17 to 19, characterized in that the carbon material comprises one or more of amorphous carbon, graphite, and graphene, and the carbon material comprises one or more of amorphous carbon, graphite, and graphene.

21. 21. The secondary battery according to claim 20, wherein the thickness of the coating layer is 2 nm to 1000 nm, and optionally 10 nm to 100 nm.

22. 22. The secondary battery according to claim 16, wherein the secondary battery includes a negative electrode active material located in pores of a porous layer of the solid electrolyte on the negative electrode plate side.

23. 23. The secondary battery according to claim 22, wherein the negative electrode active material is filled into the pores of the porous layer of the solid electrolyte by thermal injection.

24. 24. The secondary battery of claim 22 or 23, wherein the negative electrode active material includes sodium metal or a sodium alloy, and optionally, the sodium alloy includes any one of a sodium-potassium alloy, a sodium-potassium-lithium alloy, a sodium-magnesium alloy, and a sodium-zinc alloy.

25. 24. The secondary battery according to claim 16, wherein the secondary battery is a sodium secondary battery without a negative electrode.

26. 26. The secondary battery according to claim 16, wherein the solid electrolyte includes a conductive material, the conductive material is located in pores of a porous layer on a positive electrode plate side and / or a negative electrode plate side of the solid electrolyte, and the conductive material is selected from one or more of carbon nanotubes, graphite, graphene, and Super P.

27. 27. The secondary battery according to claim 16, wherein the negative electrode plate includes a negative electrode current collector and an undercoating disposed on at least one surface of the negative electrode current collector, and the undercoating includes one or more of carbon nanotubes, graphite, graphene, silver composite carbon nanoparticles, and tin composite carbon nanoparticles.

28. The areal density of the undercoating is 5 g / m ２ ~50g / m ２ 28. The secondary battery according to claim 27, wherein

29. 29. The secondary battery according to claim 27, wherein the undercoating has a thickness of 2 μm to 100 μm.

30. A battery module comprising the secondary battery according to any one of claims 16 to 29.

31. A battery pack, comprising at least one selected from the secondary battery according to any one of claims 16 to 29 and the battery module according to claim 30.

32. 32. A power consuming device comprising at least one of the secondary battery according to claim 16, the battery module according to claim 30, and the battery pack according to claim 31.

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