High-entropy sodium anode with mixed ionic / electronic conducting network and method of making and solid-state sodium metal battery

Abstract

The application belongs to the technical field of batteries, and particularly relates to a high-entropy sodium anode with a mixed ion / electron conduction network and a preparation method thereof and a solid-state sodium metal battery. Compared with the prior art, the application dopes multiple elements in the sodium anode, so that the sodium anode exhibits excellent affinity to a NASICON type solid-state electrolyte, and the sodium anode has an in-situ formed mixed ion / electron conduction network to efficiently regulate active ion deposition / peeling, has a high ion transmission rate to enable active sodium in a bulk phase to quickly migrate to a solid-state electrolyte||anode interface and participate in an electrochemical reaction, has a high electronic conductivity to make an electric field distribution at the anode and the interface more uniform, and the embedding of the mixed ion / electron conduction network in the anode forms a sodium-trapping cage structure to solve the problems of void formation at the interface and anode volume expansion, and thus the solid-state sodium metal battery containing the high-entropy sodium anode has excellent cycle stability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of batteries, and particularly relates to a high-entropy sodium anode with a mixed ion / electron conduction network and a preparation method and a solid-state sodium metal battery thereof. BACKGROUND

[0002] Metallic sodium is one of the most promising anode materials for high-energy-density rechargeable batteries due to its abundant resources (about 420 times of lithium in the earth's crust), high theoretical specific capacity (~1166 mAh g -1 ), low reduction potential (-2.71 V vs standard hydrogen electrode), and low cost. However, the flammable, explosive, and volatile nature of liquid electrolytes (LE) poses a significant risk to liquid sodium batteries. Compared with liquid electrolytes, solid-state electrolytes (SSE) have attracted extensive attention due to their high safety, high ionic conductivity, high electrochemical and chemical stability.

[0003] The main SSE systems currently available include halides, sulfides, polymers, and oxides. Compared with other SSEs, oxide solid-state electrolytes (OSSEs) represented by Na 3.1 Zr 1.95 Mg 0.05 Si2PO 12 (NZMSP) have become one of the most promising solid-state electrolytes due to their high chemical / electrochemical stability, wide voltage window (2.5-4.3 V), and high ionic conductivity (10 -4 ~ 10 -3 S cm -1 ), high mechanical strength, and potential low-temperature performance. Unfortunately, CO2 and H2O form a passivation layer Na2CO3 on the surface of NZMSP, which results in poor wettability between the sodium metal and NZMSP and generates an interfacial impedance as high as 300-800 Ωcm 2 , which severely hinders the development of solid-state sodium metal batteries (SSSMBs). Moreover, due to the slow ion diffusion rate of the sodium anode, in solid-state sodium metal batteries, as the stripping time increases, the Na + in the bulk phase of the anode cannot be quickly transported to the solid-state electrolyte / anode interface to participate in electrochemical reactions, resulting in the formation of a hole at the interface. As further stripping occurs, the local charge accumulation around the hole is further intensified, eventually forming sodium dendrites and invading the SSE, leading to short-circuiting of the battery. In addition, due to the volume expansion during the sodium ion intercalation / deintercalation process during charging / discharging, the electrode material eventually powders and fails after a long time of cycling. However, there is relatively little research on the modification of the interface of the all-solid-state sodium battery, the ion / electron diffusion kinetics in the bulk phase and at the interface of the anode, and the volume expansion of the sodium anode. SUMMARY

[0004] Therefore, the present application aims to provide a high-entropy sodium anode with a mixed ionic / electronic conduction network, a preparation method thereof and a solid-state sodium metal battery.

[0005] The present application provides a high-entropy sodium anode, comprising elements Na, P, In, Sn, Bi and Zn; the mass of P is 3.7% to 3.8% of the mass of Na; the mass of In is 2.3% to 2.5% of the mass of Na; the mass of Sn is 3.0% to 3.3% of the mass of Na; the mass of Bi is 4.2% to 4.4% of the mass of Na; and the mass of Zn is 2.5% to 2.7% of the mass of Na.

[0006] Preferably, the mass of P is 3.73% of the mass of Na;

[0007] Preferably, the mass of In is 2.39% of the mass of Na;

[0008] Preferably, the mass of Sn is 3.2% of the mass of Na;

[0009] Preferably, the mass of Bi is 4.3% of the mass of Na;

[0010] Preferably, the mass of Zn is 2.6% of the mass of Na.

[0011] Preferably, the phase composition of the high-entropy sodium anode comprises Na, Na3P, Na3Bi, Na 15 Sn4, NaZn 13 and Na3InP2.

[0012] Preferably, the high-entropy sodium anode has Figure 1 an X-ray diffraction pattern as shown in the accompanying drawings.

[0013] Preferably, the ion diffusion coefficient of the high-entropy sodium anode is greater than 3.0*10 -7 cm 2 s -1 .

[0014] Preferably, the electronic conductivity of the high-entropy sodium anode is greater than 10.6*10 6 Sm -1 .

[0015] Preferably, the high-entropy sodium anode has a three-dimensional mixed ionic and / or electronic conduction network.

[0016] The present application also provides a preparation method of the above high-entropy sodium anode, comprising the following steps:

[0017] In a protective atmosphere, phosphorus, indium, tin, bismuth and zinc are added to molten pure sodium and stirred to obtain a high-entropy sodium anode.

[0018] Preferably, the temperature of the mixing is 120-150 DEG C; the time of the stirring mixing is 5-30 min.

[0019] The application further provides a solid-state sodium metal battery comprising the high-entropy sodium anode.

[0020] Preferably, the sodium solid-state electrolyte is selected from a NASICON-type solid-state electrolyte.

[0021] The application provides a high-entropy sodium anode with a mixed ion / electron conduction network, comprising elements Na, P, In, Sn, Bi and Zn; the mass of P is 3.7-3.8% of the mass of Na; the mass of In is 2.3-2.5% of the mass of Na; the mass of Sn is 3.0-3.3% of the mass of Na; the mass of Bi is 4.2-4.4% of the mass of Na; and the mass of Zn is 2.5-2.7% of the mass of Na. Compared with the prior art, the application dopes multiple elements in the sodium anode, so that the sodium anode exhibits excellent affinity for a NASICON-type solid-state electrolyte, and has an in-situ formed mixed ion / electron conduction network for efficiently regulating active ion deposition / peeling, and also has a high ion transmission rate to enable the active sodium in the bulk phase to quickly migrate to the solid-state electrolyte||anode interface and participate in electrochemical reactions, and has a high electronic conductivity to make the electric field distribution at the anode and the interface more uniform, avoiding the formation of dendrites, in addition, the mixed ion / electron conduction network is embedded in the anode to form a sodium-trapping cage structure, so that Na proceeds along the mixed ion / electron conduction network during the deposition / peeling process, solving the problems of void formation at the interface and anode volume expansion, and thus the solid-state sodium metal battery comprising the high-entropy sodium anode has excellent cycle stability. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is an XRD pattern of the HEA obtained in Example 1 of the application;

[0023] Figure 2 It is a time-of-flight secondary ion mass spectrum of each element in the HEA obtained in Example 1 of the application in two-dimensional and three-dimensional directions;

[0024] Figure 3 It is a capacity-voltage curve and ion diffusion coefficient comparison chart of the HEA obtained in Example 1 of the application under unidirectional current application;

[0025] Figure 4 It is an electronic conductivity test result chart of the HEA obtained in Example 1 of the application;

[0026] Figure 5A photograph of the interface wetting of the HEA obtained in Example 1 of the present application and the pure sodium to the solid-state electrolyte;

[0027] Figure 6 An AC impedance spectrum of the full solid-state symmetric battery HEA||NZMSP||HEA obtained in Example 2 of the present application and the solid-state sodium metal battery Na||NZMSP||Na obtained in Comparative Example 1;

[0028] Figure 7 A critical current density curve of the full solid-state symmetric battery HEA||NZMSP||HEA obtained in Example 2 of the present application and the solid-state sodium metal battery Na||NZMSP||Na obtained in Comparative Example 1;

[0029] Figure 8 A galvanostatic electrochemical impedance spectrum and relaxation time distribution diagram of the full solid-state symmetric battery HEA||NZMSP||HEA obtained in Example 2 of the present application and the solid-state sodium metal battery Na||NZMSP||Na obtained in Comparative Example 1;

[0030] Figure 9 A scanning electron microscope diagram of the anode||solid-state electrolyte cross section after applying a unidirectional current to the full solid-state symmetric battery HEA||NZMSP||HEA obtained in Example 2 of the present application and the solid-state sodium metal battery Na||NZMSP||Na obtained in Comparative Example 1;

[0031] Figure 10 A cycle performance test result diagram of the full solid-state symmetric battery HEA||NZMSP||HEA obtained in Example 2 of the present application;

[0032] Figure 11 A rate performance and high-rate cycle performance test result diagram of the full battery HEA||NZMSP||NVP obtained in Example 3 of the present application;

[0033] Figure 12 A cycle performance test result diagram of the high-face-loading solid-state sodium battery HEA||NZMSP||NVP obtained in Example 3 of the present application;

[0034] Figure 13 A cycle performance test result diagram of the full battery HEA||NZMSP||NVP obtained in Example 3 of the present application under the condition of ultra-low temperature of-20°C and-40°C;

[0035] Figure 14 An optical photograph of the HEA||GF||NVP soft package cell obtained in Example 4 of the present application and a cycle performance test result diagram of the HEA||GF||NVP soft package cell under the condition of 1C rate. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of the present application.

[0037] The present application provides a high-entropy sodium anode, comprising elements Na, P, In, Sn, Bi and Zn; the mass of P is 3.7% to 3.8% of the mass of Na; the mass of In is 2.3% to 2.5% of the mass of Na; the mass of Sn is 3.0% to 3.3% of the mass of Na; the mass of Bi is 4.2% to 4.4% of the mass of Na; and the mass of Zn is 2.5% to 2.7% of the mass of Na.

[0038] In a specific embodiment provided by the present application, optionally, the mass of P is 3.7%, 3.71%, 3.72%, 3.73%, 3.74%, 3.75%, 3.76%, 3.77%, 3.78%, 3.79%, 3.8% of the mass of Na, or a range between any two of the above values.

[0039] In a specific embodiment provided by the present application, the mass of P is 3.73% of the mass of Na.

[0040] In a specific embodiment provided by the present application, optionally, the mass of In is 2.3%, 2.32%, 2.34%, 2.35%, 2.36%, 2.38%, 2.39%, 2.4%, 2.42%, 2.45%, 2.46%, 2.48%, 2.49%, 2.5% of the mass of Na, or a range between any two of the above values.

[0041] In a specific embodiment provided by the present application, the mass of In is 2.39% of the mass of Na.

[0042] In a specific embodiment provided by the present application, optionally, the mass of Sn is 3.0%, 3.05%, 3.1%, 3.15%, 3.2%, 3.25%, 3.3% of the mass of Na, or a range between any two of the above values.

[0043] In a specific embodiment provided by the present application, the mass of Sn is 3.2% of the mass of Na.

[0044] In an embodiment provided by the present application, the mass of Bi is 4.2%, 4.22%, 4.25%, 4.28%, 4.3%, 4.32%, 4.35%, 4.38%, 4.4% of the mass of Na, or a range between any two of the above values.

[0045] In an embodiment provided by the present application, the mass of Bi is 4.3% of the mass of Na.

[0046] In an embodiment provided by the present application, the mass of Zn is 2.5%, 2.52%, 2.55%, 2.58%, 2.6%, 2.62%, 2.65%, 2.68%, 2.7% of the mass of Na, or a range between any two of the above values.

[0047] In an embodiment provided by the present application, the mass of Zn is 2.6% of the mass of Na.

[0048] In an embodiment provided by the present application, the phase composition of the high-entropy sodium anode comprises Na, Na3P, Na3Bi, Na 15 Sn4, NaZn 13 and Na3InP2.

[0049] In an embodiment provided by the present application, the high-entropy sodium anode has Figure 1 X-ray diffraction pattern as shown in FIG. 1.

[0050] In an embodiment provided by the present application, the ion diffusion coefficient of the high-entropy sodium anode is preferably greater than 3.0 x 10 -7 cm 2 s -1 , more preferably greater than or equal to 3.05 x 10 -7 cm 2 s -1 , more preferably greater than or equal to 3.1 x 10 -7 cm 2 s -1 .

[0051] In an embodiment provided by the present application, the electronic conductivity of the high-entropy sodium anode is preferably greater than 10.6 x 10 6 Sm -1 , more preferably greater than or equal to 10.65 x 10 6 Sm -1 , more preferably greater than or equal to 10.7 x 10 6 Sm -1 , more preferably greater than or equal to 10.75 x 10 6 Sm -1most preferably 10.78 x 10 6 Sm -1 .

[0052] In a specific embodiment provided by the application, the high-entropy sodium anode has a three-dimensional mixed ionic and / or electronic conduction network.

[0053] The application has extremely excellent affinity for NASICON-type solid-state electrolyte by doping multiple elements in sodium element, and has in-situ formed mixed ionic / electronic conduction network to efficiently regulate active ion deposition / peeling, and also has high ion transmission rate to enable rapid migration of active sodium in the bulk phase to the solid-state electrolyte||anode interface and participate in electrochemical reaction, and also has high electronic conductivity to make the electric field distribution at the interface more uniform, avoiding the formation of dendrites, in addition, the mixed ionic / electronic conduction network is embedded in the anode to form a sodium-trapping cage structure, so that Na deposits / peels along the mixed ionic / electronic conduction network, solving the problems of void formation at the interface and anode volume expansion, thereby enabling the solid-state sodium metal battery containing the high-entropy sodium anode to have excellent cycle stability.

[0054] The application also provides a preparation method of the above-mentioned high-entropy sodium anode, comprising the following steps: in a protective atmosphere, phosphorus, indium, tin, bismuth and zinc are added to molten pure sodium for mixing to obtain a high-entropy sodium anode.

[0055] In the application, there is no special limitation on the source of all raw materials, which can be commercially available.

[0056] According to the application, the protective atmosphere can be any protective atmosphere known to those skilled in the art, and there is no special limitation, and argon and / or nitrogen are preferred in the application.

[0057] In a protective atmosphere, phosphorus, indium, tin, bismuth and zinc are added to molten pure sodium for mixing to obtain a high-entropy sodium anode; the phosphorus is preferably black phosphorus; the mixing temperature is preferably 120-150 DEG C; optionally, the mixing temperature is 120 DEG C, 125 DEG C, 130 DEG C, 135 DEG C, 140 DEG C, 150 DEG C or a range between any two of the above values; the mixing time is preferably 5-30 min; optionally, the mixing time is 5 min, 10 min, 15 min, 20 min, 25 min, 30 min or a range between any two of the above values.

[0058] The application also provides a solid-state sodium metal battery comprising the above-mentioned high-entropy sodium anode.

[0059] In one specific embodiment provided by the present application, the solid-state sodium metal battery further comprises a sodium solid-state electrolyte; the sodium solid-state electrolyte is preferably a NASICON-type solid-state electrolyte, more preferably a compound with a general chemical formula of Na x A y Si a P b O12; wherein A comprises at least one of Zr, Mg, Sc, Hf, 3≤x≤3.5, 1.8≤y≤2.3, 1.8≤a≤2.3, and 0.6≤b≤1.2.

[0060] In one specific embodiment provided by the present application, the sodium solid-state electrolyte is Na 3.1 Zr 1.95 Mg 0.05 Si2PO 12 .

[0061] In one specific embodiment provided by the present application, the solid-state sodium metal battery is a symmetric battery.

[0062] In one specific embodiment provided by the present application, the solid-state sodium metal battery comprises a positive electrode, a sodium solid-state electrolyte, and a negative electrode; the positive electrode is the high-entropy sodium anode described above; and / or, the negative electrode is the high-entropy sodium anode described above.

[0063] In one specific embodiment provided by the present application, when the negative electrode is the high-entropy sodium anode described above, the positive electrode is Na3V2(PO4)3.

[0064] In one specific embodiment provided by the present application, the side of the sodium solid-state electrolyte facing the positive electrode is further dripped with a sodium-ion electrolyte; the sodium-ion electrolyte comprises a solvent, a sodium salt, and an additive; the solvent is one or more of a carbonate solvent, an ether solvent, and an alcohol solvent; the carbonate solvent comprises, but is not limited to, one or more of propylene carbonate (PC), dimethyl carbonate (DMC), and ethylene carbonate (EC); the ether solvent comprises, but is not limited to, glycol dimethyl ether (GEM); the alcohol solvent comprises, but is not limited to, methanol; the sodium salt provides sodium ions (Na + ), preferably sodium hexafluorophosphate (NaPF6) and / or sodium perchlorate (NaClO4); the mass of the additive is preferably 0.5% to 5% of the mass of the electrolyte; the additive comprises, but is not limited to, fluoroethylene carbonate (FEC) that can improve the stability of the electrode interface.

[0065] In order to further illustrate the present application, one high-entropy sodium anode with a mixed ion / electron conduction network, a preparation method thereof, and a solid-state sodium metal battery provided by the present application are described in detail below with reference to the embodiments.

[0066] The reagents used in the following examples are all commercially available.

[0067] Example 1

[0068] In an argon-filled glove box, a certain mass of pure sodium was melted at 135 °C, and then 3.73 wt.% of black phosphorus, 2.39 wt.% of indium, 3.20 wt.% of tin, 4.30 wt.% of bismuth, and 2.60 wt.% of zinc were added in sequence according to the mass of sodium metal, and the mixture was stirred for 15 minutes to obtain a high-entropy sodium metal anode, denoted as HEA.

[0069] The phase composition of the HEA was analyzed by X-ray diffraction (XRD), and the XRD pattern thereof is shown in Figure 1 As can be seen from Figure 1 , the HEA is composed of Na, Na3P, Na3Bi, Na 15 Sn4, NaZn 13 , and Na3InP2 phases.

[0070] The distribution of each phase in the HEA in two-dimensional and three-dimensional directions was analyzed by time-of-flight secondary ion mass spectrometry, and the time-of-flight secondary ion mass spectra of each element in the HEA in two-dimensional and three-dimensional directions are shown in Figure 2 As can be seen from Figure 2 , the constituent elements of the HEA are uniformly distributed in two-dimensional and three-dimensional directions, indicating that a three-dimensional mixed ionic / electronic conduction network is successfully constructed.

[0071] The ion diffusion coefficient of the HEA was calculated using the Sand equation, and the capacity-voltage curve and ion diffusion coefficient of the HEA under the application of a unidirectional current are shown in Figure 3 As can be seen from Figure 3 , the ion diffusion coefficient of the HEA is increased from 2.5 × 10 -8 cm 2 s -1 of pure sodium to 3.1 × 10 -7 cm 2 s -1 , an increase of 12.4 times. The faster ion transmission rate enables the active sodium in the bulk phase to rapidly migrate to the solid-state electrolyte||anode interface and participate in the electrochemical reaction, significantly improving the kinetics.

[0072] The electronic conductivity of the HEA was tested by the four-probe method, and the electronic conductivity test results thereof are shown in Figure 4 As can be seen from Figure 4 , the electronic conductivity of the HEA is increased from 10.54 × 10 6 Sm -1 of pure sodium to 10.78 × 10 6 Sm -1The fast electron conduction network makes the electric field distribution inside the anode more uniform, suppressing dendrite formation at the source and realizing a truly dendrite-free sodium battery.

[0073] Example 2

[0074] Molten HEA was coated onto a 1 mm thick layer of Na. 3.1 Zr 1.95 Mg 0.05 Si2PO 12 On one side of (NZMSP), the coating thickness is about 1mm. After it condenses, the HEA is coated on the other side in the same way, with a coating thickness of about 1mm. After the HEA condenses, the all-solid-state symmetric cell HEA||NZMSP||HEA is assembled.

[0075] Comparative Example 1

[0076] In an argon-filled glove box, a certain mass of sodium metal was transferred to a stainless steel container, heated to 130°C to melt it, and then coated onto a 1mm thick Na layer. 3.1 Zr 1.95 Mg 0.05 Si2PO 12 On one side of (NZMSP), a coating thickness of about 1 mm is applied. After it solidifies, molten sodium is applied to the other side in the same way, with a coating thickness of about 1 mm. After solidification, a solid sodium metal battery Na||NZMSP||Na is assembled.

[0077] Photographs of the interfacial wettability of pure sodium and HEA to solid electrolytes are shown below. Figure 5 The above refers to the interfacial wetting property of pure sodium to the solid electrolyte, and (b) refers to the interfacial wetting property of HEA to the solid electrolyte. Figure 5 It can be seen that HEA exhibits extremely excellent wettability to solid electrolytes.

[0078] The AC impedance spectra of the all-solid-state symmetric battery HEA||NZMSP||HEA obtained in Example 2 and the solid-state sodium metal battery Na||NZMSP||Na obtained in Comparative Example 1 were measured, and their AC impedance spectra are shown below. Figure 6 As shown. By Figure 6 It can be seen that the interfacial impedance of the solid sodium metal battery Na||NZMSP||Na is as high as 749.2 Ωcm. 2 The interfacial impedance of the all-solid-state symmetric cell HEA||NZMSP||HEA is reduced to 12Ωcm. 2 The impedance is only 1.6% of that of a pure sodium symmetric cell, indicating that HEA exhibits extremely excellent wettability to solid electrolytes.

[0079] The critical current density (CCD) of the all-solid-state symmetric battery HEA||NZMSP||HEA obtained in Example 2 and the solid-state sodium metal battery Na||NZMSP||Na obtained in Comparative Example 1 were tested using the constant current method. The critical current density curves are shown in the figure below. Figure 7 As shown. By Figure 7 It can be seen that the CCD of the solid sodium metal battery Na||NZMSP||Na is only 0.1 mA cm⁻¹. -2 The all-solid-state symmetric battery HEA||NZMSP||HEA obtained in Example 2 has a CCD of up to 2.1 mA cm⁻¹. -2 The current density is 21 times that of a pure sodium symmetric cell. This is because the mixed ion / electron conduction network formed in situ in the sodium metal anode can efficiently regulate the deposition / stripping of active ions. The faster ion transport rate allows active sodium in the bulk phase to migrate rapidly to the solid electrolyte || anode interface and participate in electrochemical reactions, thus significantly increasing the critical current density of the symmetric cell.

[0080] The evolution process and areal capacity of the Na||NZMSP and HEA||NZMSP interface were analyzed using electrochemical impedance spectroscopy (GEIS) combined with relaxation time distribution (DRT), and the GEIS and relaxation time distribution diagrams are shown below. Figure 8 As shown, (a) is the galvanostatic electrochemical impedance spectroscopy (galvanostatic impedance spectroscopy) of the solid sodium metal battery Na||NZMSP||Na, (e) is the relaxation time distribution corresponding to (a), (b) to (d) are the galvanostatic electrochemical impedance spectroscopy (galvanostatic impedance spectroscopy) of the solid sodium symmetric battery HEA||NZMSP||HEA, and (f) to (h) are the relaxation time distributions corresponding to (b) to (d), respectively. Figure 8 It can be seen that the solid sodium metal battery Na||NZMSP||Na obtained in Comparative Example 1 has a performance of 0.1 mA cm⁻¹ -2 A short circuit occurred after only 25 minutes of continuous stripping at the current density, and the areal capacity was only 0.04 mAh cm⁻¹. -2 The solid-state sodium symmetric solar cell HEA||NZMSP||HEA obtained in Example 2 has a range of 0.1, 0.3, and 0.5 mA cm⁻¹. -2 It can continuously desorb at current densities of 180, 85, and 50 hours, achieving a breakthrough areal capacity of 25.5 mAh cm⁻¹. -2 It is 637.5 times the volume of pure sodium.

[0081] The all-solid-state symmetric battery HEA||NZMSP||HEA obtained in Example 2 and the solid-state sodium metal battery Na||NZMSP||Na obtained in Comparative Example 1 were subjected to unidirectional current stripping with a unidirectional current density of 0.1 mA cm⁻¹. -2 After 25 minutes, it was analyzed using a scanning electron microscope, and the resulting scanning electron microscope image is shown below.Figure 9 As shown, (a) is a SEM image of the solid-state sodium metal battery Na||NZMSP||Na after unidirectional current stripping, and (b) is a SEM image of the all-solid-state symmetric battery HEA||NZMSP||HEA after unidirectional current stripping. Figure 9 It can be seen that during the symmetrical cell stripping process, the stripping of the pure sodium anode always takes place in one location, while the embedded mixed ion / electron conduction network of the HEA forms a cage structure that traps sodium inside the anode, allowing Na to travel along the mixed ion / electron conduction network during the deposition / stripping process, thus solving the problems of void formation at the interface and anode volume expansion.

[0082] The cycle performance of the all-solid-state symmetric battery HEA||NZMSP||HEA obtained in Example 2 was tested, and its cycle stability test results are as follows: Figure 10 As shown, (a) is a solid-state sodium symmetric battery HEA||NZMSP||HEA at an ultra-low temperature of -40℃ and 0.01mA cm⁻¹. -2 The cycle stability of (b) is 0.1 mA cm⁻¹ for a solid-state sodium symmetric battery HEA||NZMSP||HEA at room temperature. -2 The cycle stability of (c) is 0.3 mA / cm² for a solid-state sodium symmetric battery HEA||NZMSP||HEA at room temperature. -2 The cyclic stability. (By...) Figure 10 It can be seen that the solid sodium symmetric battery HEA||NZMSP||HEA prepared in Example 2 has a performance of 0.1 mA cm⁻¹ -2 and 0.3mA cm -2 It can stably cycle for over 9300h and 4400h at current densities, exhibiting an ultra-long cycle life. To demonstrate the excellent regulation capability of the hybrid ion / electron conduction network in HEA on ion / electron diffusion at ultra-low temperatures and to broaden the operating temperature range of solid-state sodium batteries, an all-solid-state symmetric cell of HEA||NZMSP||HEA was assembled. Cyclic stability tests were conducted at an ultra-low temperature of -40℃. It was found that this symmetric cell can maintain stable operation at ultra-low temperatures of -40℃ and 0.01mA cm⁻¹. -2 It can operate stably for over 3000 hours at current density (this is the lowest operating temperature and longest ultra-low temperature cycling time reported in the NASICON system to date), with the overpotential consistently maintained at 17mV and no short circuits. This demonstrates that the hybrid ion / electron conduction network can efficiently regulate the participation of ions / electrons in electrochemical reactions at ultra-low temperatures, enabling the all-solid-state symmetric battery to exhibit extremely excellent ultra-low temperature performance. Notably, no short circuits were observed after all the above-mentioned symmetric battery tests were completed.

[0083] Depend on Figure 9 and Figure 10It can be known that the anode structure is kept highly stable by designing the mixed ion / electron conducting network, the interlaced disordered network constitutes a sodium ion trapping cage structure, the formation of holes at the interface during the continuous peeling process is inhibited, and the volume expansion is inhibited, and the ion / electron diffusion in the electrochemical process is efficiently adjusted, and the formation of dendrites is inhibited from the source, so that the truly dendrite-free sodium battery is realized. Thanks to this advanced design, the symmetrical battery can be stably cycled for more than 3000h at an ultra-low temperature of-40 DEG C. This is unique in all previous studies on NASICON-based solid-state sodium batteries, and a major breakthrough has been made.

[0084] Example 3

[0085] A solid-state sodium battery HEA||NZMSP||NVP is assembled by taking HEA as the anode matching active material Na3V2(PO4)3(NVP). The specific implementation steps are as follows: the molten HEA is coated on one side of the NZMSP with a thickness of 1mm, the coating thickness is about 1mm, after cooling, 5 microliters of 1M NaClO4 solvent PC and 5% FEC electrolyte are added dropwise on the other side to soak the positive electrode, and then a NVP positive electrode sheet with a surface loading of 1.6mg cm -2 of the battery is obtained.

[0086] The rate performance and cycle performance of the full battery HEA||NZMSP||NVP are tested at room temperature, and the test result graph is as shown in Figure 11 , wherein (a) is the rate performance result graph of the full battery HEA||NZMSP||NVP, (b) is the charge-discharge curve graph corresponding to the rate performance, (c) is the high-rate (5C) cycle curve graph, and (d) is the charge-discharge curve graph corresponding to the 5C rate cycle curve. It can be known from Figure 11 that the capacity of the full battery HEA||NZMSP||NVP is 110.96, 106.9, 104.99, 100.96, 87.87 and 76.88mAh g -1 respectively at 0.1C, 0.3C, 0.5C, 1V, 3C and 5C rates. -1 When returning from 5C to 0.1C, the capacity is 109.05mAh g -2 , which is 98.3% of the initial 0.1C capacity, showing extremely excellent rate performance. Further, the full battery is tested for long cycle at room temperature, and it is found that it can be stably cycled for more than 10000 cycles at a rate of 5C, and the capacity retention rate is 88.5%, which is the longest cycle life at a high rate in the NASICON system so far.

[0087] In order to further improve the energy density of the full battery, the positive active material loading is increased to 2.4mg cm -2Rise to 15 mg cm -2 The cycle performance of the assembled high surface loading solid-state sodium battery HEA||NZMSP||NVP was tested, and the cycle performance test result graph thereof is as shown in Figure 12 , wherein (a) is a cycle curve, and (b) is a charge-discharge curve. It can be known from Figure 12 that the high surface loading solid-state sodium battery HEA||NZMSP||NVP still stably cycles more than 150 times, and the capacity retention rate is 99%, which is the highest loading and longest cycling in the same research.

[0088] Further, in order to prove the excellent regulation ability of the mixed ion / electron conduction network in HEA to ion / electron diffusion at ultra-low temperature, broaden the operating temperature of the solid-state sodium battery, the full battery HEA||NZMSP||NVP prepared in Example 3 was subjected to cycle stability test at-20℃ and-40℃ ultra-low temperature conditions respectively, and the cycle stability test result graph thereof is as shown in Figure 13 , wherein (a) is a-20℃ cycle curve, (b) is a-20℃ charge-discharge curve, (c) is a-40℃ cycle curve, and (d) is a-20℃ charge-discharge curve. It can be known from Figure 13 that it can stably cycle more than 120 times at-40℃, and the capacity retention rate is 80%, and it can stably operate more than 420 times at-20℃, and the capacity retention rate is as high as 97%, showing extremely excellent ultra-low temperature performance. It is worth noting that all the HEA||NZMSP||NVP solid-state sodium batteries after the above tests are not short-circuited, and all the electrochemical performances in this research are unique in the research so far, which is a great breakthrough.

[0089] In summary, the solid-state sodium metal battery assembled using the high-entropy sodium anode matching NVP has made a major breakthrough in the field of solid-state sodium batteries, and has shown great research and commercial value.

[0090] Example 4

[0091] A soft pack battery HEA||GF||NVP was assembled with HEA as the anode matching active material Na3V2(PO4)3(NVP) and glass fiber separator (GF). The specific implementation steps are as follows: the HEA anode was prepared by a melting method, and was mechanically rolled into a 0.3mm thick HEA foil, which was then cut into 4x5cm, and the glass fiber separator was placed on it, and a 4x5cm NVP positive electrode with a surface loading of 1.6mg cm -2 was placed on it, 2mL of 1M NaClO4 solvent PC and 5% FEC electrolyte were added, and then it was vacuum sealed to obtain the HEA||GF||NVP soft pack battery, and the cycle stability was tested after 12h of static state, as shown in Figure 14 .

[0092] Figure 14 is the optical photo and HEA||GF||NVP pouch cell cycle performance test result graph of example 4. After 100 cycles at 1C rate, the capacity retention rate of HEA||GF||NVP pouch cell is 100%( Figure 14 b), without any attenuation, showing excellent cycle stability. In summary, the HEA||GF||NVP pouch cell assembled using the high-entropy sodium anode matching NVP has made a major breakthrough in the field of sodium batteries, showing great research and commercial value.

[0093] In summary, the HEA anode synthesized by the present application with a mixed ion / electron conduction network can efficiently regulate ion / electron diffusion in electrochemical processes, and the advantage under ultra-low temperature conditions is particularly obvious, and the formation of dendrites is inhibited from the source, thereby realizing a truly dendrite-free sodium battery. The all-solid-state symmetric battery assembled using HEA exhibits incredible cycle life (>9000h, >3000h at-40℃) and ultra-high areal capacity (25.5mAh cm -2 ), making a major breakthrough in the field of solid-state sodium batteries. More importantly, the HEA||NZMSP||NVP assembled using HEA exhibits a solid-state sodium battery with more than 10000 stable cycles at 5C high rate, and can stably operate under ultra-low temperature conditions of-20 and-40℃, showing great research and commercial value. In addition, the soft package cell HEA||GF||NVP assembled using HEA has a surprising capacity retention rate of 100% after 100 cycles, without any attenuation, showing great commercial value.

[0094] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A solid-state sodium metal battery, characterized by, The high-entropy sodium anode comprises a mixed ion / electron conduction network; the high-entropy sodium anode is composed of elements Na, P, In, Sn, Bi and Zn; the mass of P is 3.7% to 3.8% of the mass of Na; the mass of In is 2.3% to 2.5% of the mass of Na; the mass of Sn is 3.0% to 3.3% of the mass of Na; the mass of Bi is 4.2% to 4.4% of the mass of Na; the mass of Zn is 2.5% to 2.7% of the mass of Na; the phase composition of the high-entropy sodium anode comprises Na, Na3P, Na3Bi, Na 15 Sn4, NaZn 13 and Na3InP2; Also included is a sodium solid-state electrolyte; the sodium solid-state electrolyte is selected from a NASICON type solid-state electrolyte.

2. The solid-state sodium metal battery of claim 1, wherein, The mass of P is 3.73% of the mass of Na; And / or, the mass of In is 2.39% of the mass of Na; And / or, the mass of Sn is 3.2% of the mass of Na; And / or, the mass of Bi is 4.3% of the mass of Na; And / or, the mass of Zn is 2.6% of the mass of Na.

3. The solid-state sodium metal battery of claim 1, wherein, The ion diffusion coefficient of the high-entropy sodium anode is greater than 3.0 x 10 -7 cm 2 s -1 ; and / or the high-entropy sodium anode has an electronic conductivity greater than 10.6 x 10 6 S m -1 .

4. The solid-state sodium metal battery of claim 1, wherein, The high-entropy sodium anode has a three-dimensional mixed ion and / or electron conduction network.

5. The solid-state sodium metal battery of claim 1, wherein, The preparation method of the high-entropy sodium anode comprises the following steps: In a protective atmosphere, phosphorus, indium, tin, bismuth and zinc are added to molten pure sodium and stirred and mixed to obtain a high-entropy sodium anode.

6. The solid-state sodium metal battery of claim 5, wherein, The temperature of the mixing is 120℃-150℃; the time of the stirring and mixing is 5-30 min.

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