Secondary battery and electric equipment

Abstract

The invention belongs to the technical field of secondary batteries, and particularly relates to a secondary battery and electric equipment. The invention provides a secondary battery, which comprises a negative pole piece, and the negative pole piece comprises a sodium metal matrix; the interface layer is arranged on at least one surface of the sodium metal matrix, the interface layer comprises a non-metal sodium ion compound and at least two sodium metal alloys, and the non-metal sodium ion compound comprises at least one of telluride, selenide and sulfide. The secondary battery provided by the invention has excellent cycle performance, rate capability and mechanical strength.

Description

Technical Field

[0001] This application belongs to the field of secondary battery technology, specifically relating to a secondary battery and an electrical device. Background Technology

[0002] Pure sodium metal anodes are considered ideal materials for high-energy-density energy storage systems due to their high theoretical specific capacity (1166 mAh / g) and low cost. However, pure sodium metal is prone to forming needle-like dendrites during cycling, leading to interface inhomogeneity and increased interfacial impedance, which severely restricts its practical application. To address this issue, existing technologies mainly regulate sodium ion deposition behavior by constructing artificial interface layers, such as using polymer coatings (e.g., polyvinylidene fluoride, polyethylene oxide), carbon materials (e.g., graphene, carbon nanotubes), or traditional metal alloys (e.g., Cu, Ni, Al) as interface buffer layers. However, these methods have significant limitations: polymer coatings are easily pierced by dendrites and lack mechanical strength; carbon materials have limited conductivity, making it difficult to achieve uniform ion transport; and traditional metal alloys have poor chemical stability, making it difficult to effectively suppress dendrite growth. Summary of the Invention

[0003] The main objective of this application is to provide a secondary battery and an electrical device to solve the problem of poor cycle performance of batteries made with sodium metal as the negative electrode in the prior art.

[0004] To achieve the above objectives, according to one aspect of this application, a secondary battery is provided, including a negative electrode sheet, said negative electrode sheet comprising: Sodium metal matrix; An interface layer is disposed on at least one surface of the sodium metal substrate, the interface layer comprising a non-metallic sodium ion compound and at least two sodium metal alloys, the non-metallic sodium ion compound comprising at least one of telluride, selenide and sulfide.

[0005] In one alternative embodiment, the thickness of the interface layer is 100nm-300nm.

[0006] In one optional embodiment, the mass ratio of the non-metallic sodium ion compound to the sodium metal alloy is 1:(0.44~1.35).

[0007] In one alternative embodiment, the telluride comprises sodium telluride.

[0008] In one alternative embodiment, the selenide comprises sodium selenide.

[0009] In one alternative embodiment, the sulfide comprises sodium sulfide.

[0010] In one alternative embodiment, the sodium metal alloy includes at least two of sodium-tin alloy, sodium-lead alloy, sodium-zinc alloy, sodium-bismuth alloy, sodium-gallium alloy, and sodium-indium alloy.

[0011] In one alternative embodiment, the sodium metal alloy includes at least five of the following: sodium-tin alloy, sodium-lead alloy, sodium-zinc alloy, sodium-bismuth alloy, sodium-gallium alloy, and sodium-indium alloy.

[0012] In one alternative implementation, the Young's modulus of the interface layer is 9 GPa-13 GPa.

[0013] In one optional embodiment, the exchange current density of the interface layer is 1.5 mA / cm². 2 -2.5mA / cm 2 .

[0014] In one alternative embodiment, the activation energy of the interface layer is 18 kJ / mol to 40 kJ / mol.

[0015] In one alternative implementation, the interface layer is at a current density of 1 mA / cm². 2 The nucleation overpotential is 35mV-50mV.

[0016] According to another aspect of this application, the aforementioned secondary battery is included, wherein the secondary battery serves as the power supply for the electrical device.

[0017] The technical solution of this application has the following advantages: The secondary battery provided in this application includes a negative electrode sheet, which comprises: a sodium metal substrate; and an interface layer disposed on at least one surface of the sodium metal substrate. The interface layer comprises a non-metallic sodium ion compound and at least two sodium metal alloys, wherein the non-metallic sodium ion compound includes at least one of telluride, selenide, and sulfide. The secondary battery provided in this application exhibits excellent cycle performance, rate performance, and mechanical strength. Specifically, the sodium metal alloy and the non-metallic sodium ion compound can synergistically promote the uniform deposition of sodium ions and inhibit the formation of sodium dendrites, thereby improving the cycle performance and rate performance of the sodium metal negative electrode. Simultaneously, compared to a single alloy component, the at least two sodium metal alloys provided in this application, through synergistic action, firstly, can reduce local current density and inhibit dendrite nucleation and growth; secondly, can form a heterogeneous structure, which, through the difference in the thermal expansion coefficients of different sodium metal alloys, disperses mechanical stress during cycling, reduces crack and dendrite formation, and is beneficial to the cycle performance of the battery; thirdly, the multi-component sodium metal alloys can also reduce the side reactions between sodium metal and the electrolyte through synergistic action. Furthermore, non-metallic sodium ion compounds can form a stable interfacial phase with the sodium metal matrix surface, promoting uniform sodium ion transport, reducing interfacial impedance, thereby increasing the sodium ion deposition rate of the battery at high rates, which is beneficial to improving the rate performance of the battery. Detailed Implementation

[0018] The following embodiments are provided to better understand this application and are not limited to the preferred embodiments described herein. They do not constitute a limitation on the content and scope of protection of this application. Any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining features of this application with other prior art, falls within the scope of protection of this application.

[0019] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0020] In a first aspect, this application provides a secondary battery, including a negative electrode sheet, said negative electrode sheet comprising: Sodium metal matrix; An interface layer is disposed on at least one surface of the sodium metal substrate, the interface layer comprising a non-metallic sodium ion compound and at least two sodium metal alloys, the non-metallic sodium ion compound comprising at least one of telluride, selenide and sulfide.

[0021] When pure sodium metal is used as the negative electrode in sodium-metal batteries, sodium dendrite growth is induced during high-rate cycling. This is because the surface of the pure sodium metal negative electrode has insufficient sodium deposition nucleation sites, and the SEI film (solid electrolyte interface film) formed by pure sodium metal and electrolyte has insufficient sodium ion transport efficiency, making the SEI film easily punctured by dendrites. These problems seriously affect the cycle and rate performance of the battery. Based on this, this application sets an interface layer on one side of the sodium metal substrate to modify the surface of the sodium metal substrate.

[0022] The interface layer comprises a non-metallic sodium ion compound and at least two sodium metal alloys. These sodium metal alloys have a strong affinity for sodium metal, resulting in more nucleation sites on their surface. This allows sodium ions to nucleate uniformly on the interface layer, rather than concentrating in protruding regions, thus inhibiting dendrite growth and improving the sodium ion transport efficiency of the interface layer. Furthermore, the interface layer exhibits good mechanical strength, resisting dendrite penetration. In addition, sodium metal undergoes significant volume expansion (>80%) during cycling; the sodium metal alloys can mitigate this volume change, reducing mechanical stress in the interface layer and inhibiting crack and dendrite formation. Meanwhile, the non-metallic sodium ion compound, as a fast ion conductor, has good ionic conductivity, which can promote the uniform transport of sodium ions in the interface layer, reduce the unevenness of local current density, inhibit dendrite growth, and improve the cycle and rate performance of the battery. Furthermore, it can act as a physical barrier, isolating the sodium metal substrate from direct contact with the electrolyte, thereby inhibiting sodium oxidation or electrolyte decomposition, thus improving the chemical stability of the sodium ion deposition interface and enhancing the battery's cycle performance. In addition, the non-metallic sodium ion compound can also form a stable interface phase with the sodium metal substrate surface, promoting the uniform transport of sodium ions, reducing interface impedance, and thus increasing the sodium ion deposition rate at high rates, which is beneficial for improving the battery's rate performance.

[0023] Sodium metal alloys and non-metallic sodium ion compounds can synergistically promote the uniform deposition of sodium ions, thereby inhibiting the formation of sodium dendrites and improving the cycle performance of sodium metal anodes. Simultaneously, the sodium metal alloy on the surface of a pure sodium anode can provide nucleation sites, promoting sodium ion growth. The interlayer sodium metal alloy can synergistically work with non-metallic sodium ion compounds with high sodium ion conductivity to promote the deposition of sodium ions in the electrolyte. + Adsorption with Na + During interlayer transport, the two work together to form a composite ion transport network, which significantly improves sodium ion transport and deposition rates, thereby enhancing the rate performance of the battery.

[0024] The at least two sodium metal alloys described in this application work synergistically to reduce local current density and suppress dendrite nucleation and growth. Simultaneously, the multi-component sodium metal alloys form a heterogeneous structure, and the differences in the thermal expansion coefficients of the different components disperse the mechanical stress during sodium metal cycling, reducing crack and dendrite formation and improving battery cycle performance. Furthermore, the multi-component sodium alloys exhibit better structural stability, significantly improving the chemical stability of the interface layer and reducing side reactions between the interface layer and the sodium metal matrix or electrolyte. Conversely, if only a single sodium metal alloy is used as the interface layer on the sodium metal matrix surface, the interface layer's ability to alleviate the mechanical stress of the sodium metal is weak, failing to completely suppress crack and dendrite formation. Moreover, the interface layer has poor stability and is prone to generating numerous side reactions with the electrolyte, affecting battery cycle performance.

[0025] Meanwhile, if the interface layer does not contain non-metallic sodium ion compounds, the ionic conductivity of the interface layer is weak, the local current density is uneven, and dendrite formation is easily induced; at the same time, the stability of the interface layer deteriorates and the interface impedance increases significantly, thereby affecting the cycle and rate performance of the battery.

[0026] The material contained in the interface layer of the negative electrode sheet can be determined by X-ray diffraction analysis (XRD). Specifically, the sample is cut and placed into the XRD test slot under a protective atmosphere for testing. The scanning range is 5-80°, the scanning speed is 1° / min, and the step size is 0.1°.

[0027] Based on this, the sodium metal anode of this application has high sodium ion diffusion rate, high mechanical strength, long lifespan, and high rate performance.

[0028] In one optional embodiment, the thickness of the interface layer is 100 nm-300 nm. Exemplarily, the thickness of the interface layer can be any one or both of 100 nm, 150 nm, 180 nm, 230 nm, 280 nm, and 300 nm. In this application, the interface layer thickness is limited to the range of 100 nm-300 nm, thus resulting in better bonding between the interface layer and the sodium metal substrate. + The low internal resistance improves current density uniformity, thereby avoiding side reactions that could affect battery cycle performance. The interface layer also exhibits good mechanical strength, capable of withstanding volume expansion caused by sodium deposition / stripping during cycling, preventing localized cracking or stress concentration and thus inhibiting dendrite growth, which is beneficial for battery cycle performance. The thickness of the interface layer can be measured using a transmission electron microscope (TEM).

[0029] In one optional embodiment, the mass ratio of the non-metallic sodium ion compound to the sodium metal alloy is 1:(0.44~1.35). Exemplarily, the mass ratio of the non-metallic sodium ion compound to the sodium metal alloy can be any one or a combination of 1:0.44, 1:0.59, 1:0.66, 1:0.75, 1:0.79, 1:1.02, 1:1.11, and 1:1.35. This effectively increases ion flux, reduces interfacial impedance, thereby reducing interfacial side reactions and suppressing dendrite growth. Simultaneously, it improves the uniformity of sodium ion deposition, thereby improving current density uniformity, avoiding localized sodium deposition, and the interface layer has good mechanical strength, making it less prone to cracking during the deposition and peeling process, which is beneficial to the battery's cycle performance. The method for testing the mass ratio of the non-metallic sodium ion compound and the sodium metal alloy is as follows: After scraping off the coating on the sodium metal surface, ICP test is used to identify the molar amount of the metal component and the molar amount of the compound element. Combined with the substance category obtained by XRD test, the mass ratio is calculated as follows: (molar number of non-metallic elements × molar mass of sodium compound) / (molar number of metallic elements × molar mass of sodium alloy).

[0030] In one alternative embodiment, the telluride comprises sodium telluride. This further facilitates uniform transport of sodium ions and reduces interfacial impedance.

[0031] In one alternative embodiment, the selenide comprises sodium selenide. This further facilitates uniform transport of sodium ions and reduces interfacial impedance.

[0032] In one alternative embodiment, the sulfide comprises sodium sulfide. This further facilitates uniform transport of sodium ions and reduces interfacial impedance.

[0033] In one optional embodiment, the sodium metal alloy includes at least two of sodium-tin alloy, sodium-lead alloy, sodium-zinc alloy, sodium-bismuth alloy, sodium-gallium alloy, and sodium-indium alloy. This can improve the sodium ion mass transfer performance and deposition sites of the interface layer, thereby enhancing the electrical performance of the battery.

[0034] In one optional embodiment, the sodium metal alloy includes at least five of the following: sodium-tin alloy, sodium-lead alloy, sodium-zinc alloy, sodium-bismuth alloy, sodium-gallium alloy, and sodium-indium alloy. This significantly improves the ion transport efficiency, mechanical stability, and chemical stability of the interface layer, suppresses dendrite growth, and enhances cycle performance.

[0035] In one optional embodiment, the Young's modulus of the interface layer is 9 GPa-13 GPa; thus, the negative electrode sheet has good mechanical strength, resulting in good interfacial stability during cycling and reducing the likelihood of plastic deformation or local collapse; simultaneously, the thermal expansion coefficient of the interface layer matches that of sodium metal, reducing stress concentration during cycling and improving the cycle performance of the battery. Exemplarily, the Young's modulus of the interface layer can be any one or any two of 9 GPa, 10 GPa, 11 GPa, 12 GPa, and 13 GPa. The Young's modulus of the interface layer can be obtained using atomic force microscopy (AFM), including: placing the sample on a sample stage, then immersing it in an AFM apparatus with a protective atmosphere, performing force-displacement curve testing, and calculating the Young's modulus using a Hertz contact mechanics model.

[0036] In one optional embodiment, the exchange current density of the interface layer is 1.5 mA / cm². 2 -2.5mA / cm 2 When the exchange current density of the interface layer is within the above range, it ensures a suitable sodium deposition / stripping rate, suppresses local overpotential rise, inhibits dendrite growth, and improves the cycle and rate performance of the battery. For example, the exchange current density of the interface layer can be 1.5 mA / cm². 2 1.7mA / cm 2 2mA / cm 2 2.3mA / cm 2 2.5mA / cm 2 The range of any one or both of these values. Method for testing the exchange current density of the interface layer: Test the Tafel curve of the symmetrical cell at a scan rate of 1 mV / s and a voltage range of -0.2 to 0.2V. Determine the linear portion (Tafel region) of the anode and cathode regions. Determine the exchange current density by extrapolation. Extrapolate the Tafel linear portion to the point where the overpotential is 0; the current density corresponding to this point is the exchange current density.

[0037] In one optional embodiment, the activation energy of the interface layer is 18 kJ / mol-40 kJ / mol. This results in a high sodium ion migration rate, uniform current distribution, and better stability at high temperatures, reducing the likelihood of side reactions and improving battery cycle and rate performance. Exemplarily, the activation energy of the interface layer can be any one or both of the following ranges: 18 kJ / mol, 20 kJ / mol, 25 kJ / mol, 30 kJ / mol, 35 kJ / mol, and 40 kJ / mol. The activation energy of the interface layer is tested by placing the assembled symmetrical battery containing the negative electrode of this application at 25°C, 30°C, 35°C, 40°C, and 45°C to measure the electrochemical impedance spectroscopy (EIS). The high-frequency impedance (Z) is extracted using EIS to calculate the ionic conductivity σ (σ = A / Zd), and ln(σ) is plotted against 1 / T to obtain the activation energy (Ea) = -R·slope. Where d is the electrolyte thickness, A is the electrode area, and R is the gas constant.

[0038] In one alternative implementation, the interface layer is at a current density of 1 mA / cm². 2 The nucleation overpotential is 35mV-50mV. This facilitates sodium ion deposition while preventing excessively rapid deposition, effectively improving the uniformity of current density distribution, thereby suppressing dendrite growth and benefiting the battery's cycle and rate performance. For example, the interface layer is designed for a current density of 1mA / cm². 2 The nucleation overpotential can be any one or any two of the following: 35mV, 38mV, 40mV, 42mV, 45mV, 47mV, and 50mV. The interface layer operates at a current density of 1mA / cm². 2 The test method for nucleation overpotential includes: assembling a symmetrical cell containing the negative electrode of this application, and testing at a current density of 1 mA / cm². 2 Under certain conditions, stripping is performed, and the overpotential corresponding to the abrupt change point of the voltage curve is the nucleation overpotential.

[0039] Secondly, this application provides an electrical device including the aforementioned secondary battery, wherein the secondary battery serves as the power supply for the electrical device.

[0040] This application also provides a method for preparing a sodium metal anode, comprising the following steps: S1. Mixing at least two metal compounds to obtain a mixed material; S2. In a glove box, the mixed material is coated on at least one side of the sodium metal substrate to obtain the sodium metal negative electrode.

[0041] The mechanism of action is as follows: after the metal compound reacts with sodium metal, at least two sodium metal alloys and non-metallic sodium ion compounds are formed.

[0042] This application reduces the exposure of pure sodium by first mixing at least two metal compounds to obtain a mixed material, and then coating the mixed material onto the surface of a sodium metal substrate to form an interface layer. This avoids adverse phenomena such as a reduction in the nucleation sites of sodium ions and an increase in interfacial impedance due to side reactions with the electrolyte.

[0043] In one possible implementation, the metal compound includes at least one of a metal sulfide, a metal selenide, and a metal telluride.

[0044] In one possible implementation, after coating the composite material onto one side of a sodium metal matrix, it is left to stand at 25-40°C for 8-40 hours to allow for sufficient reaction, and then excess composite material powder is removed. The 8-40 hour standing period allows for better formation of the interface layer.

[0045] Example 1 This embodiment provides a secondary battery, including a negative electrode sheet. The negative electrode sheet comprises: a sodium metal substrate; and an interface layer disposed on one surface of the sodium metal substrate. The interface layer comprises a non-metallic sodium ion compound (sodium telluride) and a sodium metal alloy (sodium-tin alloy, sodium-zinc alloy, sodium-bismuth alloy, sodium-gallium alloy, and sodium-indium alloy). The Young's modulus of the interface layer is 9.9 GPa; and the exchange current density of the interface layer is 2.5 mA / cm². 2 The activation energy of the interface layer is 18 kJ / mol; the interface layer operates at a current density of 1 mA / cm². 2 The nucleation overpotential is 35 mV. The thickness of the interface layer is 100 nm; in the interface layer, the mass ratio of non-metallic sodium ion compound to sodium metal alloy is 1:0.59. The method for preparing the negative electrode sheet in this embodiment includes the following steps: 1) Mix 0.52g gallium telluride (Ga2Te3), 0.62g indium telluride (In2Te3), 0.38g zinc telluride (ZnTe), 0.8g bismuth telluride (Bi2Te3), and 0.5g tin telluride (SnTe). After mixing, transfer the mixture to a ball mill jar. Replace the air in the ball mill jar with an inert gas. The ball-to-material ratio is 20:1, the rotation speed is 800r / min, and the mixture is milled for 30min and then allowed to stand for 30min. After milling for 72h, a mixed material with a D50 of 80nm is obtained. 2) In a glove box (where the water and oxygen content are both less than 0.1 ppm), after removing the surface oxide layer of the sodium metal block, it is placed in a polypropylene (PP) sample bag and repeatedly rolled to obtain a sodium metal sheet with a thickness of 200 μm. The mixed material obtained in step 1) is coated on the surface of the sodium metal sheet and left to stand at 40°C for 40 h (to complete the reaction). Unreacted excess powder is removed with a soft brush, and the negative electrode sheet is obtained after cutting into round sheets with a diameter of 12 mm for later use.

[0046] This embodiment also provides a method for preparing a symmetrical battery, including the following steps: In a glove box with a water oxygen content of less than 0.1 ppm, the prepared negative electrode sheets are assembled into a symmetrical battery using a glass fiber separator and a sodium perchlorate electrolyte (1 mol / L NaClO4, ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1, with the total mass of the electrolyte as the basis and the mass content of fluoroethylene carbonate (FEC) being 5 wt%). That is, two identical negative electrode sheets serve as the positive and negative electrodes of the battery, and the side with the interface layer is close to the separator.

[0047] This embodiment also provides a method for preparing a secondary battery, including the following steps: (1) Sodium vanadium phosphate (specific capacity of 117 mAh / g) was used as the positive electrode material. Sodium vanadium phosphate, acetylene black and polyvinylidene fluoride were mixed in a mass ratio of 7:2:1. After grinding and mixing evenly, an electrode slurry was prepared, coated on aluminum foil, and vacuum dried at 80°C for 24 hours. After punching holes, small round pieces with a diameter of 12 mm were obtained to obtain the positive electrode sheet. (2) In a glove box with a water oxygen content of less than 0.1 ppm, the prepared negative electrode, positive electrode, glass fiber separator, sodium perchlorate electrolyte (1 mol / L NaClO4, ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1, based on the total mass of the electrolyte, the mass content of fluoroethylene carbonate (FEC) is 5 wt%) is assembled into a button cell.

[0048] Examples 2-6 This embodiment provides a negative electrode sheet, which is basically the same as that in Embodiment 1. The main difference is that the D50 nm of the mixed material is adjusted by adjusting the rotation speed and time of the ball mill during the preparation process, thereby adjusting the thickness of the interface layer. The D50 of the mixed material in Embodiment 2 is 92 nm, and the thickness of the interface layer is 111 nm. The D50 of the mixed material in Embodiment 3 is 100 nm, and the thickness of the interface layer is 120 nm. The D50 of the mixed material in Embodiment 4 is 103 nm, and the thickness of the interface layer is 127 nm. The D50 of the mixed material in Embodiment 5 is 115 nm, and the thickness of the interface layer is 135 nm. The D50 of the mixed material in Embodiment 6 is 230 nm, and the thickness of the interface layer is 300 nm.

[0049] Examples 2-6 also provide a symmetrical battery, which uses the negative electrode sheet provided in Examples 2-6 instead of the negative electrode sheet provided in Example 1, and is otherwise basically the same as Example 1.

[0050] Examples 2-6 also provide a secondary battery, which uses the negative electrode sheet provided in Examples 2-6 to replace the negative electrode sheet provided in Example 1, and is otherwise basically the same as Example 1.

[0051] Examples 7-8 This embodiment provides a negative electrode sheet, which is basically the same as that in embodiment 3, the main difference being the adjustment of the non-metallic ion compound in the negative electrode sheet; Specifically, in Example 7, gallium sulfide (Ga2S3), indium sulfide (In2S3), zinc sulfide (ZnS), bismuth sulfide (Bi2S3), and tin sulfide (SnS) in equimolar amounts of the corresponding metal elements in Example 3 were weighed to replace gallium telluride, indium telluride, zinc telluride, bismuth telluride, and tin telluride in Example 3. At this time, the mass ratio of the non-metallic sodium ion compound to the sodium metal alloy was 1:1.31. In Example 8, gallium selenide (Ga2Se3), indium selenide (In2Se3), zinc selenide (ZnSe), bismuth selenide (Bi2Se3), and tin selenide (SnSe) in equimolar amounts of the corresponding metal elements in Example 3 were weighed to replace gallium telluride, indium telluride, zinc telluride, bismuth telluride, and tin telluride in Example 3. In this case, the mass ratio of the non-metallic sodium ion compound to the sodium metal alloy was 1:0.82.

[0052] Examples 7-8 also provide a symmetrical battery, which uses the negative electrode sheet provided in Examples 7-8 instead of the negative electrode sheet provided in Example 3, and is otherwise basically the same as Example 3.

[0053] Examples 7-8 also provide a secondary battery, which uses the negative electrode sheet provided in Examples 7-8 to replace the negative electrode sheet provided in Example 3, and is otherwise basically the same as Example 3.

[0054] Example 9 This embodiment provides a negative electrode sheet, which is basically the same as that in embodiment 3, the main difference being the adjustment of the type of sodium metal alloy in the negative electrode sheet; Specifically, lead telluride was used instead of gallium telluride in Example 3, and the molar amounts of lead and gallium were equal. In this case, the mass ratio of the non-metallic sodium ion compound to the sodium metal alloy was 1:0.77.

[0055] Example 9 also provides a symmetrical battery, which uses the negative electrode sheet provided in Example 9 instead of the negative electrode sheet provided in Example 3, and is otherwise basically the same as Example 3.

[0056] Example 9 also provides a secondary battery, which uses the negative electrode sheet provided in Example 9 instead of the negative electrode sheet provided in Example 3, and is otherwise basically the same as Example 3.

[0057] Example 10 This embodiment provides a negative electrode sheet, which is basically the same as that in embodiment 4, the main difference being the adjustment of the type of sodium metal alloy in the negative electrode sheet; Specifically, lead telluride was used instead of tin telluride in Example 4, and the molar amounts of lead and tin were equal. In this case, the mass ratio of the non-metallic sodium ion compound to the sodium metal alloy was 1:0.68.

[0058] Example 10 also provides a symmetrical battery, which uses the negative electrode sheet provided in Example 10 instead of the negative electrode sheet provided in Example 4, and is otherwise basically the same as Example 4.

[0059] Example 10 also provides a secondary battery, which uses the negative electrode sheet provided in Example 10 instead of the negative electrode sheet provided in Example 4, and is otherwise basically the same as Example 4.

[0060] Example 11 This embodiment provides a negative electrode sheet, which is basically the same as that in embodiment 6, the main difference being the adjustment of the type of sodium metal alloy in the negative electrode sheet; Specifically, lead telluride was used instead of zinc telluride in Example 6, and the molar amounts of lead and zinc were equal. In this case, the mass ratio of the nonmetallic sodium ion compound to the sodium metal alloy was 1:0.73.

[0061] Example 11 also provides a symmetrical battery, which uses the negative electrode sheet provided in Example 11 instead of the negative electrode sheet provided in Example 6, and is otherwise basically the same as Example 6.

[0062] Example 11 also provides a secondary battery, which uses the negative electrode sheet provided in Example 11 instead of the negative electrode sheet provided in Example 6, and is otherwise basically the same as Example 6.

[0063] Example 12 This embodiment provides a negative electrode sheet, which is basically the same as that in embodiment 5, the main difference being the adjustment of the type of sodium metal alloy in the negative electrode sheet; Specifically, lead telluride was used instead of bismuth telluride in Example 5, and the molar amounts of lead and bismuth were equal. In this case, the mass ratio of the nonmetallic sodium ion compound to the sodium metal alloy was 1:0.64.

[0064] Example 12 also provides a symmetrical battery, which uses the negative electrode sheet provided in Example 12 instead of the negative electrode sheet provided in Example 5, and is otherwise basically the same as Example 5.

[0065] Example 12 also provides a secondary battery, which uses the negative electrode sheet provided in Example 12 instead of the negative electrode sheet provided in Example 5, and is otherwise basically the same as Example 5.

[0066] Examples 13-16 This embodiment provides a negative electrode sheet, which is basically the same as that in embodiment 1. The main difference is that the type of sodium metal alloy in the negative electrode sheet is adjusted, and the rotation speed and time of the ball mill jar are adjusted during the preparation process. Specifically, in Example 13, zinc telluride, bismuth telluride, and tin telluride were not added. In this case, the D50 of the mixed material in Example 13 was 110 nm, the thickness of the interface layer was 125 nm, and the mass ratio of the non-metallic sodium ion compound to the sodium metal alloy was 1:0.44. Example 14 does not include gallium telluride, indium telluride, zinc telluride, or bismuth telluride, but adds lead telluride. The molar amounts of lead and tin are equal. In this case, the D50 of the mixed material in Example 14 is 110 nm, the thickness of the interface layer is 125 nm, and the mass ratio of the non-metallic sodium ion compound to the sodium metal alloy is 1:1.04. In Example 15, gallium telluride, indium telluride, and tin telluride were not added. In this case, the D50 of the mixed material in Example 15 was 110 nm, the thickness of the interface layer was 125 nm, and the mass ratio of the non-metallic sodium ion compound to the sodium metal alloy was 1:0.70. In Example 16, gallium telluride, zinc telluride, and tin telluride were not added. In this case, the D50 of the mixed material in Example 16 was 110 nm, the thickness of the interface layer was 125 nm, and the mass ratio of the non-metallic sodium ion compound to the sodium metal alloy was 1:0.71.

[0067] Examples 13-16 also provide a symmetrical battery, which uses the negative electrode sheet provided in Examples 13-16 instead of the negative electrode sheet provided in Example 1, and is otherwise basically the same as Example 1.

[0068] Examples 13-16 also provide a secondary battery, which uses the negative electrode sheet provided in Examples 13-16 instead of the negative electrode sheet provided in Example 1, and is otherwise basically the same as Example 1.

[0069] Comparative Example 1 The difference from Example 1 is that a sodium metal substrate is cut into a circular sheet with a diameter of 12 mm, instead of the negative electrode sheet described in Example 1.

[0070] This comparative example also provides a symmetrical battery, which uses the negative electrode sheet provided in Comparative Example 1, and is otherwise basically the same as Example 1.

[0071] This comparative example also provides a secondary battery that uses the negative electrode sheet provided in Comparative Example 1, and is otherwise basically the same as in Example 1.

[0072] Comparative Example 2 This comparative example provides a negative electrode sheet. The preparation method of the negative electrode sheet of this comparative example includes the following steps: 1) Weigh out the same amount of gallium powder, indium powder, zinc powder, bismuth powder, and tin powder as the metal elements corresponding to those in Example 1. 2) In a glove box (where the water and oxygen content are both less than 0.1 ppm), after removing the surface oxide layer of the sodium metal block, place it in a polypropylene (PP) sample bag and repeatedly roll it to obtain a sodium metal sheet with a thickness of 200 μm; coat the elemental metal powder from step 1) into the sodium metal, and then repeatedly roll it for 3 hours (to complete the reaction). After cutting, the negative electrode sheet can be obtained and cut into round sheets with a diameter of 12 mm for later use.

[0073] This comparative example also provides a symmetrical battery, which uses the negative electrode sheet provided in Comparative Example 2, and is otherwise basically the same as in Example 1.

[0074] This comparative example also provides a secondary battery that uses the negative electrode sheet provided in Comparative Example 2, and is otherwise basically the same as in Example 1.

[0075] Comparative Example 3 This comparative example provides a secondary battery, including a negative electrode sheet. XRD analysis of the negative electrode sheet reveals that the interface layer contains a non-metallic sodium ion compound (sodium telluride). The Young's modulus of the interface layer is 8.7 GPa, and the exchange current density of the interface layer is 1.6 mA / cm². 2 The activation energy of the interface layer is 29.3 kJ / mol; the interface layer operates at a current density of 1 mA / cm². 2 The nucleation overpotential was 42 mV, and the thickness of the interface layer was 212 nm. The preparation method of the negative electrode sheet in this comparative example includes the following steps: In a glove box (with water and oxygen content less than 0.1 ppm), the surface oxide layer of the sodium metal block was removed, and it was placed in a polypropylene (PP) sample bag and repeatedly rolled to obtain a sodium metal sheet with a thickness of 200 μm. Tellurium powder was coated on the surface of the sodium metal sheet, and it was left to stand at 40°C for 40 hours (to complete the reaction). Excess powder on the surface of the sodium negative electrode was removed with a soft brush, and the negative electrode sheet was cut into 12 mm diameter discs for later use. The amount of tellurium added to the tellurium powder was equal to the total molar amount of tellurium in gallium telluride, indium telluride, zinc telluride, bismuth telluride, and tin telluride in Example 1.

[0076] This comparative example also provides a symmetrical battery, which uses the negative electrode sheet provided in Comparative Example 3, and is otherwise basically the same as Example 1.

[0077] This comparative example also provides a secondary battery that uses the negative electrode sheet provided in Comparative Example 3, and is otherwise basically the same as Example 1.

[0078] Comparative Example 4 This comparative example provides a secondary battery, including a negative electrode sheet. XRD analysis of the negative electrode sheet reveals that the interface layer comprises a sodium metal alloy (sodium-tin alloy, sodium-zinc alloy, sodium-bismuth alloy, sodium-gallium alloy, and sodium-indium alloy). The Young's modulus of the interface layer is 21.5 GPa, and the exchange current density of the interface layer is 1.8 mA / cm². 2 The activation energy of the interface layer is 31.2 kJ / mol; the interface layer operates at a current density of 1 mA / cm². 2 The nucleation overpotential was 54 mV, and the thickness of the interface layer was 145 nm. The preparation method of the negative electrode sheet in this comparative example includes the following steps: 1) Weigh out the same amount of gallium powder, indium powder, zinc powder, bismuth powder, and tin powder as the metal elements corresponding to those in Example 1. 2) In a glove box (where the water and oxygen content are both less than 0.1 ppm), after removing the surface oxide layer of the sodium metal block, it is placed in a polypropylene (PP) sample bag and repeatedly rolled to obtain a sodium metal sheet with a thickness of 200 μm. The elemental metal powder from step 1) is coated on the surface of the sodium metal sheet and left to stand at 40°C for 40 h (to complete the reaction). Excess powder on the surface of the sodium negative electrode is removed with a soft brush. After cutting, the negative electrode sheet can be obtained and cut into round sheets with a diameter of 12 mm for later use.

[0079] This comparative example also provides a symmetrical battery, which uses the negative electrode sheet provided in Comparative Example 4, and is otherwise basically the same as Example 1.

[0080] This comparative example also provides a secondary battery that uses the negative electrode sheet provided in Comparative Example 4, and is otherwise basically the same as in Example 1.

[0081] The parameters of the above embodiments and comparative examples are shown in Table 1.

[0082] Table 1 Parameters for each embodiment and comparative example

[0083] Test case This test case provides the performance of the batteries in various embodiments and comparative examples, as detailed below: Symmetrical battery test: The test was conducted on a Newway battery tester, with a test current density of 1 mA / cm². 2 The deposition stripping capacity is 1 mAh / cm³. 2Symmetrical battery cycle tests were conducted. When the cycle voltage suddenly changed, the test was stopped, and the cycle test time at this point was recorded as the battery's cycle life. The results are shown in Table 2.

[0084] Full battery test: Cycle capacity retention test: The test was conducted on a Newway battery tester, with a test voltage range of 2.5V. At 3.8V, charge-discharge cycle performance was tested at 8C to obtain the capacity of the first cycle. After 1000 cycles, the cycle capacity retention rate was calculated as (capacity of 1000 cycles / capacity of the first cycle) × 100%. The results are shown in Table 2.

[0085] Rate performance testing: Tested using a Newway battery tester, with a test voltage range of 2.5V. The battery was fully charged at 0.5C at 3.8V, and then the discharge capacity was tested at 1C and 8C respectively. The rate performance was calculated as 8C discharge capacity / 1C discharge capacity × 100%. The results are shown in Table 2.

[0086] Table 2 Performance Test Results

[0087] As shown in Table 2, the negative electrode sheet of the secondary battery provided in this application includes a sodium metal substrate and an interface layer. The interface layer contains a non-metallic sodium ion compound and at least two sodium metal alloys. The sodium metal alloy and the non-metallic sodium ion compound can synergistically promote the uniform deposition of sodium ions and suppress the formation of sodium dendrites, thereby improving the cycle performance of the sodium metal negative electrode. At the same time, the non-metallic sodium ion compound can also form a stable interface phase with the surface of the sodium metal substrate, promote the uniform transport of sodium ions, and help improve the rate performance of the battery.

[0088] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A secondary battery, characterized in that, Includes a negative electrode sheet, wherein the negative electrode sheet comprises: Sodium metal matrix; An interface layer is disposed on at least one surface of the sodium metal substrate, the interface layer comprising a non-metallic sodium ion compound and at least two sodium metal alloys, the non-metallic sodium ion compound comprising at least one of telluride, selenide and sulfide.

2. The secondary battery according to claim 1, characterized in that, The thickness of the interface layer is 100nm-300nm; and / or, The mass ratio of the non-metallic sodium ion compound to the sodium metal alloy is 1:(0.44~1.35).

3. The secondary battery according to claim 2, characterized in that, The telluride includes sodium telluride; and / or, the selenide includes sodium selenide; and / or, the sulfide includes sodium sulfide.

4. The secondary battery according to claim 1, characterized in that, The sodium metal alloy includes at least two of the following: sodium-tin alloy, sodium-lead alloy, sodium-zinc alloy, sodium-bismuth alloy, sodium-gallium alloy, and sodium-indium alloy.

5. The secondary battery according to claim 1, characterized in that, The sodium metal alloy includes at least five of the following: sodium-tin alloy, sodium-lead alloy, sodium-zinc alloy, sodium-bismuth alloy, sodium-gallium alloy, and sodium-indium alloy.

6. The secondary battery according to any one of claims 1-5, characterized in that, The Young's modulus of the interface layer is 9 GPa-13 GPa.

7. The secondary battery according to any one of claims 1-5, characterized in that, The exchange current density of the interface layer is 1.5 mA / cm². 2 -2.5mA / cm 2 .

8. The secondary battery according to any one of claims 1-5, characterized in that, The activation energy of the interface layer is 18 kJ / mol - 40 kJ / mol.

9. The secondary battery according to any one of claims 1-5, characterized in that, The interface layer is at a current density of 1 mA / cm² 2 The nucleation overpotential is 35mV-50mV.

10. An electrical appliance, characterized in that, The device includes the secondary battery as described in any one of claims 1-9, wherein the secondary battery serves as the power supply for the electrical equipment.

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