Secondary battery and electric device

Abstract

This application provides a secondary battery and an electrical device. The secondary battery uses a high-entropy alloy matrix comprising a first element and a second element as the main body of the negative electrode, ensuring high capacity, high conductivity, and good cycle performance. Simultaneously, a modification layer comprising an amorphous alloy is provided on the surface of the high-entropy alloy matrix. Since the amorphous alloy lacks grain boundaries, the series resistance can be reduced, thereby reducing the battery's resistance. Furthermore, because the amorphous alloy is in a metastable state with high surface energy, dendrites will grow into the interior of the amorphous alloy after nucleation, reducing the risk of dendrites piercing the separator and providing higher safety. Therefore, this application improves upon the problem that existing ion battery negative electrode structures cannot simultaneously achieve high energy density, excellent rate performance, and long cycle life.

Description

Technical Field

[0001] This application relates to the field of battery manufacturing technology, and in particular to a secondary battery and electrical equipment. Background Technology

[0002] With the rapid development of the new energy industry, sodium-ion batteries, which are abundant in resources and inexpensive, have become an important backup battery technology.

[0003] However, its anode system still faces many challenges, which restricts further improvement in battery performance.

[0004] Current mainstream sodium-ion batteries use hard carbon anodes, with actual specific capacity typically ranging from 300 to 400 mAh / g, which is insufficient to meet the demand for high energy density. At the same time, the high internal resistance of sodium-ion batteries is caused by the inherent impedance of the copper foil current collector, the interfacial impedance between the current collector and the coating, and the internal contact impedance of the coating, which limits the high-power charge and discharge performance of the battery.

[0005] Sodium metal anodes are considered an ideal choice for improving energy density, but they are prone to forming sodium dendrites during cycling, which may puncture the diaphragm and cause internal short circuits, posing a serious safety hazard. Summary of the Invention

[0006] The technical problem to be solved by this application is to provide a secondary battery and an electrical device to solve the problem that the negative electrode structure of existing secondary batteries cannot simultaneously achieve high energy density, excellent rate performance and long cycle life.

[0007] To solve the above problems, this application provides the following technical solution: This application discloses a secondary battery, wherein the secondary battery includes a negative electrode, and the negative electrode includes: A high-entropy alloy matrix, wherein the high-entropy alloy matrix comprises a first element and a second element, wherein the first element comprises at least four of Al, Cu, Co, Ni, Fe, Mn, Cr, Ti, V, and Mo, and the second element comprises at least one of Sn, P, Sb, Bi, Ga, and In; A modification layer is disposed on the surface of the high-entropy alloy substrate, wherein the modification layer comprises an amorphous alloy.

[0008] Furthermore, in the secondary battery, the first element includes Cu, Ni, Co, and Al, and the second element includes Sn and / or P.

[0009] Furthermore, in the secondary battery, the amorphous alloy includes at least one of Cu-Sn amorphous alloy, Ni-Sn amorphous alloy, Co-Sn amorphous alloy, Al-Sn amorphous alloy, Al-Ni amorphous alloy, Al-Cu amorphous alloy, Cu-P amorphous alloy, Ni-P amorphous alloy, Co-P amorphous alloy, and Al-P amorphous alloy.

[0010] Furthermore, the atomic percentage of the second element in the high-entropy alloy matrix is ​​30% to 35%.

[0011] Furthermore, in the secondary battery, the atomic percentages of Cu, Ni, Co, Al, Sn, and P in the negative electrode are independently 5% to 35%.

[0012] Furthermore, in the secondary battery, the modification layer further includes a nanocrystalline alloy, which includes at least one of Cu-Sn nanocrystalline alloy, Ni-Sn nanocrystalline alloy, Co-Sn nanocrystalline alloy, Al-Sn nanocrystalline alloy, Al-Ni nanocrystalline alloy, Al-Cu nanocrystalline alloy, Cu-P nanocrystalline alloy, Ni-P nanocrystalline alloy, Co-P nanocrystalline alloy, and Al-P nanocrystalline alloy.

[0013] Furthermore, in the secondary battery, the thickness of the modification layer is 0.45 μm to 1.5 μm; and / or The thickness of the high-entropy alloy matrix is ​​4μm~12μm.

[0014] Furthermore, in the secondary battery, the average particle size of the nanocrystalline alloy is 1 nm to 5 nm.

[0015] Furthermore, the secondary battery satisfies at least one of the following conditions: (I) The tensile strength of the negative electrode sheet is 750MPa~850MPa; and / or (II) The Brinell hardness of the negative electrode sheet is 150 HB to 220 HB; and / or (III) The conductivity of the negative electrode is 10. 4 S / m~10 6 S / m.

[0016] This application also proposes an electrical device, which includes the aforementioned secondary battery, serving as the power supply for the electrical device.

[0017] Compared with the prior art, the embodiments of this application have the following advantages: In this embodiment, the secondary battery includes a negative electrode sheet, which comprises a high-entropy alloy substrate. The high-entropy alloy includes a first element and a second element. The first element includes at least four of Al, Cu, Co, Ni, Fe, Mn, Cr, Ti, V, and Mo, and the second element includes at least one of Sn, P, Sb, Bi, Ga, and In. A modification layer is disposed on the surface of the alloy substrate, and the modification layer includes an amorphous alloy. The high-entropy alloy substrate, including the first and second elements, serves as the main body of the negative electrode sheet, ensuring high capacity, high conductivity, and good cycle performance. Simultaneously, the modification layer comprising an amorphous alloy is disposed on the surface of the high-entropy alloy substrate. Since the amorphous alloy lacks grain boundaries, it reduces series resistance, thereby reducing the battery's resistance. Furthermore, because the amorphous alloy is in a metastable state with high surface energy, dendrites will grow into the interior of the amorphous alloy after nucleation, reducing the risk of dendrites piercing the separator and providing higher safety. Therefore, this embodiment improves upon the problem that existing ion battery negative electrode structures cannot simultaneously achieve high energy density, excellent rate performance, and long cycle life.

[0018] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the negative electrode sheet in the embodiments of this application.

[0020] Explanation of reference numerals in the attached figures: 10-Negative electrode sheet, 11-High entropy alloy matrix, 12-Modifying layer. Detailed Implementation

[0021] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] To address the aforementioned problems, this application provides a secondary battery, such as... Figure 1 As shown, the secondary battery includes a negative electrode 10, which includes: a high-entropy alloy substrate 11, which includes a first element and a second element. The first element includes at least four of Al, Cu, Co, Ni, Fe, Mn, Cr, Ti, V, and Mo, and the second element includes at least one of Sn, P, Sb, Bi, Ga, and In; and a modification layer 12 disposed on the surface of the high-entropy alloy substrate 11, which includes an amorphous alloy.

[0023] In this embodiment, a high-entropy alloy matrix comprising the first and second elements is used as the main body of the negative electrode sheet, ensuring high capacity, high conductivity, and good cycle performance. Simultaneously, a modification layer comprising an amorphous alloy is formed on the surface of the high-entropy alloy matrix. Since the amorphous alloy lacks grain boundaries, the series resistance is reduced, thereby lowering the resistance of the negative electrode sheet. Furthermore, because the amorphous alloy is in a metastable state with high surface energy, dendrites will grow into the interior of the amorphous alloy after nucleation, thus reducing the risk of dendrites piercing the separator and providing higher safety. Therefore, the embodiments of this application improve upon the problem that existing secondary battery negative electrode structures cannot simultaneously achieve high energy density, excellent rate performance, and long cycle life.

[0024] Optionally, in one embodiment, the first element includes Cu, Ni, Co, and Al, and the second element includes Sn and / or P.

[0025] Among them, Al has good ductility, high theoretical capacity, low discharge potential, and low price; Co can buffer volume expansion and enhance conductivity and inhibit agglomeration; Cu can alleviate volume expansion and enhance conductivity; while Ni has good ductility, can act as a mechanical support, and improve conductivity. The above-mentioned first element as the main material can ensure the high theoretical capacity of the electrode, improve the mechanical strength of the electrode, and have good conductivity.

[0026] Sn has a high theoretical specific capacity, and sufficient tin helps to improve the negative electrode capacity. Sn and Na / Li undergo an alloying reaction, and the charge-discharge process has good reversibility. P also has a high theoretical specific capacity. It forms a reversible compound Na3P / Li3P with Na / Li, and the P element can stabilize the structure and improve the mechanical strength of the alloy.

[0027] In this embodiment, by adding Sn and P to the alloy with Cu, Ni, Co and Al as the main materials, it is possible not only to utilize the fact that Sn or P can react with Na / Li to complete sodium insertion / deintercalation / lithium insertion / deintercalation, but also to improve the specific capacity of the negative electrode material and significantly improve the conductivity of the pure high-entropy alloy matrix.

[0028] Optionally, in one embodiment, the above-mentioned modification layer can be formed in situ on the high-entropy alloy substrate by laser cladding process, and the improvement can be achieved by introducing laser cladding process into the existing process.

[0029] Optionally, in one embodiment, the laser cladding process includes: applying a pulsed or continuous laser beam to the surface of a high-entropy alloy substrate to a point above the melting point of the high-entropy alloy substrate material, followed by cooling through the thermal conductivity of the foil itself; wherein the laser application time can be 10... -3 ~10 -5 The laser's operating temperature can be 1500℃~1700℃.

[0030] Optionally, in one embodiment, the amorphous alloy includes at least one of Cu-Sn amorphous alloy, Ni-Sn amorphous alloy, Co-Sn amorphous alloy, Al-Sn amorphous alloy, Al-Ni amorphous alloy, Al-Cu amorphous alloy, Cu-P amorphous alloy, Ni-P amorphous alloy, Co-P amorphous alloy, and Al-P amorphous alloy. Because the impedance of the aforementioned amorphous alloy materials is much lower than that of conventional crystalline materials and they have better charge-discharge reversibility, by providing a modification layer including the aforementioned amorphous alloy material on the surface of the negative electrode, the negative electrode can have good conductivity while ensuring high theoretical capacity and mechanical strength of the electrode, and can reduce the risk of dendrite puncturing the separator, thus providing higher safety.

[0031] Optionally, in one embodiment, the modified layer further includes a nanocrystalline alloy, that is, the modified layer is a mixed material layer of amorphous alloy and nanocrystalline alloy, wherein the nanocrystalline alloy includes at least one of Cu-Sn nanocrystalline alloy, Ni-Sn nanocrystalline alloy, Co-Sn nanocrystalline alloy, Al-Sn nanocrystalline alloy, Al-Ni nanocrystalline alloy, Al-Cu nanocrystalline alloy, Cu-P nanocrystalline alloy, Ni-P nanocrystalline alloy, Co-P nanocrystalline alloy, and Al-P nanocrystalline alloy, making the modified layer easy to prepare by laser cladding process, and enabling the use of amorphous alloy to reduce series resistance and reduce the risk of dendrite piercing the diaphragm, thus ensuring higher safety.

[0032] When the laser power is low, the scanning speed is fast, and the foil is thin, the heat conduction is fast, the alloy composition has a high glass-forming ability, and the cooling rate is fast. For example, Sn / P will form more amorphous alloy components. When the laser power is high, the scanning speed is slow, and the foil is thick, the heat conduction is slow, the alloy contains nucleation points or segregation, the cooling rate is moderate, and more nanocrystalline alloys will be formed.

[0033] Optionally, in one embodiment, the atomic percentages of Cu, Ni, Co, Al, Sn and P in the negative electrode sheet are independently 5% to 35%, for example, they can be one or any two of the following values: 5%, 6%, 8%, 10%, 12%, 15%, 20%, 25%, 30%, 35%, which can give full play to the advantages of high-entropy alloys, thereby providing good mechanical properties while reducing the thickness of the foil.

[0034] Optionally, in one embodiment, the atomic percentage of the second element in the negative electrode sheet is 30% to 35%, for example, it can be one or any two of the following values: 30%, 31%, 32%, 33%, 34%, and 35%, which can effectively balance mechanical performance, negative electrode capacity, and good charge-discharge reversibility.

[0035] Optionally, in one embodiment, the atomic percentage of the second element in the high-entropy alloy matrix is ​​30% to 35%, for example, it can be one or any two of 30%, 31%, 32%, 33%, 34%, and 35%. This can leverage the high specific capacity advantage of the second element while maintaining the excellent mechanical properties of the high-entropy alloy, effectively improving the negative electrode capacity. Furthermore, good charge-discharge reversibility can be achieved through the alloying reaction between the second element and active ions such as Na and Li.

[0036] Optionally, in one embodiment, the atomic percentage of the second element in the modification layer is 30% to 35%, for example, it can be one or any two of 30%, 31%, 32%, 33%, 34%, and 35%. This can significantly improve the conductivity of the pure high-entropy alloy matrix while maintaining the good mechanical properties of the high-entropy alloy matrix. Furthermore, the second element can undergo alloying reactions with active ions such as Na and Li to complete sodium insertion / deintercalation and lithium insertion / deintercalation, thereby significantly improving the specific capacity of the negative electrode material.

[0037] Optionally, in one embodiment, the thickness of the above-mentioned modification layer is 0.45μm to 1.5μm, for example, it can be one or any two of the following values: 0.45μm, 0.5μm, 0.6μm, 0.8μm, 1.0μm, 1.2μm, 1.5μm. This allows the modification layer to better achieve the beneficial functions of reducing series resistance, inducing sodium dendrites to grow inward, and improving structural stability. It is also less likely to cause cracking or peeling of the modification layer due to thermal stress caused by the difference in thermal expansion coefficients between the high-entropy alloy matrix and the modification layer. It can also balance the increase in manufacturing process complexity and cost.

[0038] Optionally, in one embodiment, the thickness of the high-entropy alloy substrate is 4μm to 12μm, for example, it can be one or any two of the following values: 4μm, 5μm, 6μm, 8μm, 9μm, 10μm, 11μm, and 12μm. This not only makes the substrate processing less difficult, avoiding waste of capacity and energy and increased manufacturing costs, but also ensures good conductivity, thermal conductivity, mechanical properties and electrochemical properties of the negative electrode sheet.

[0039] Optionally, in one embodiment, the particle size of the above-mentioned nanocrystalline alloy is 1nm~5nm, for example, it can be one or any two of 1nm, 2nm, 3nm, 4nm, 5nm, which can take into account the strength, hardness, corrosion resistance and other properties of the material, ensure the unique advantages of nanocrystals, and avoid problems such as grain boundary migration or crystallization in high-energy states that cause structural instability.

[0040] In the secondary battery provided in this application embodiment, the negative electrode sheet is made of a high-entropy alloy material, which has excellent mechanical properties and can provide good mechanical properties while reducing the thickness of the foil. Optionally, in one embodiment, the thickness of the negative electrode sheet is maintained between 4μm and 12μm, without the need for additional coating of active material, and its yield strength can reach more than 400MPa, while its tensile strength is 750MPa to 850MPa, for example, it can be one or any two of the following values: 750MPa, 760MPa, 770MPa, 780MPa, 790MPa, 800MPa, 810MPa, 820MPa, 830MPa, 840MPa, and 850MPa.

[0041] In the secondary battery provided in this application embodiment, the negative electrode sheet includes a high-entropy alloy material, and the Brinell hardness of the negative electrode sheet is 150HB~220HB. For example, it can be one or any two of the following values: 150HB, 160HB, 170HB, 180HB, 190HB, 200HB, 810HB, and 220HB. This can effectively strengthen the strength of the entire battery cell core and significantly reduce the risk of deformation and penetration of the battery cell under external force.

[0042] In the secondary battery provided in this application embodiment, due to the incorporation of the second element, it can not only undergo alloying reactions with active ions such as Na and Li to complete sodium insertion / deintercalation and lithium insertion / deintercalation, thus achieving a reversible charge-discharge process, but also prevents the second element from forming a crystalline phase in the amorphous alloy, i.e., there are no grain boundaries. Therefore, the ohmic resistance (Rs) can be significantly reduced, resulting in a conductivity of 10 for the negative electrode. 4 S / m~10 6 S / m.

[0043] In some embodiments, the above-mentioned negative electrode sheet is prepared according to the following process: Metal raw materials are added according to the design ratio, heated and melted, and cooled and solidified to form alloy ingots; wherein, the metal raw materials include a first element and a second element; The alloy ingots are shredded, reheated and melted, sprayed and rolled, and then rapidly cooled to form high-entropy alloy foil. The surface of the foil is heated to a molten state by a laser beam and then rapidly cooled by the foil itself, forming an amorphous alloy layer on the original high-entropy alloy foil surface as a modification layer, while the rest of the high-entropy alloy foil serves as the high-entropy alloy substrate, together forming the negative electrode sheet.

[0044] Alternatively, in one embodiment, the heating and melting can be carried out in the crucible of an electric arc furnace or an induction furnace.

[0045] Alternatively, in one embodiment, the raw materials are heated to above the melting point of the metal with the highest melting point by means of an electric arc or coil induction, and the metal elements are uniformly distributed by repeated melting to ensure that all raw materials are melted.

[0046] For example, when the metal raw materials include aluminum-tin alloys (or aluminum and phosphorus powder) and copper, nickel-cobalt alloys, all raw materials need to be heated to above 1500°C.

[0047] Optionally, in one specific embodiment, the atomic proportion of tin in the aluminum-tin alloy is 5% to 50%, and the atomic proportion of cobalt in the nickel-cobalt alloy is 25% to 45%.

[0048] Among them, the atomic ratio of tin in aluminum-tin alloy is limited to 5%~50%, which can take into account the advantages of aluminum, such as light weight, high capacity, good conductivity and low price, and effectively suppress the expansion of Sn to improve structural stability. It can also utilize Sn to effectively realize reversible alloying reaction. Among them, limiting the atomic proportion of cobalt in the nickel-cobalt alloy to 25%~45% can effectively balance conductivity, structural stability and good reversibility.

[0049] The alloy ratio can be adjusted by adding pure metal particles to achieve the design standard.

[0050] Optionally, in one embodiment, during the process of reheating and melting the spray coating roller, the crushed alloy ingot is reheated and melted by a single-roller rapid cooling technique and sprayed onto the surface of a high-speed rotating cooling roller, and a high-entropy alloy foil is obtained after rapid cooling.

[0051] Optionally, in one embodiment, the reheating and melting temperature is slightly higher than the reheating and melting temperature, and the reheating and melting time is slightly lower than the reheating and melting time, to ensure that the alloy melts and there is a sufficient temperature difference between it and the cooling roller. For example, when the metal raw materials include aluminum-tin alloy (or aluminum and phosphorus powder) and copper, nickel-cobalt alloy, the reheating and melting temperature range is 1550~1650°C, and the time is 20~30 minutes.

[0052] Optionally, in one embodiment, in order to reduce the evaporation of the second element such as Sn or P, the number of repeated meltings should be 3 to 5, and the melting time for each melting should be 20 to 30 minutes.

[0053] Optionally, in one embodiment, in the single-roller rapid cooling technology, a copper roller with a thermal conductivity of 350~400 W / (m·K) can be used, and the rotation speed of the copper roller can be 2500~5000 rpm, which can efficiently cool and obtain high-entropy alloy foil with stable quality.

[0054] Optionally, in one embodiment, after the modification layer is formed, the foil is sprayed and cleaned with anhydrous ethanol, deionized water or distilled water, and then subsequent cutting and other processes are performed to obtain the above-mentioned negative electrode sheet.

[0055] The secondary battery provided in this application also includes a positive electrode and an electrolyte.

[0056] The aforementioned positive electrode sheet includes a positive current collector and a positive active material layer disposed on the positive current collector, wherein the positive active material layer includes a positive active material. Optionally, in one embodiment, the secondary battery can be a sodium-ion battery, and the positive electrode active material is a sodium-containing positive electrode active material.

[0057] When the secondary battery provided in this application is a sodium-ion battery, because an amorphous alloy and / or nanocrystalline alloy Al-Co-Cu-Ni-Sn alloy or Al-Co-Cu-Ni-P is formed on the surface of the high-entropy alloy matrix, there are no intermetallic compounds, and Sn and P in the amorphous alloy do not form crystalline phases, they can react with Na to complete sodium insertion and subsequent sodium removal. After 100 cycles of charge and discharge, the reversible capacity of the battery reaches 500~600 mAh / g. The reaction formula of Sn and Na is: Sn + xNa + + xe - →Na x Sn.

[0058] Optionally, in one specific embodiment, the sodium-containing positive electrode active material includes at least one of sodium ion transition metal oxides, sodium ion transition metal phosphates and variants, sodium ion transition metal sulfates, and Prussian blue compounds.

[0059] Optionally, in one specific embodiment, the sodium-containing positive electrode active material comprises NaCoO2, NaMnO2, and NaNi. 0.33 Fe 0.33 Mn 0.33 One or more of O2, NaFePO4, NaCoPO4, and Na3V2(PO4)3.

[0060] Alternatively, in another embodiment, the secondary battery can be a lithium-ion battery, and the positive electrode active material is a lithium-containing positive electrode active material.

[0061] Optionally, in one specific embodiment, the lithium-containing positive electrode active material includes a lithium-ion transition metal oxide. The lithium-ion transition metal oxide includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, and nickel-cobalt-manganese ternary compounds, specifically such as Li(Ni) 0.8 Mn 0.1 Co0.1 O2, Li(Ni) 1 / 3 Mn 1 / 3 Co 1 / 3 O2, Li(Ni) 0.5 Mn 0.2 Co 0.3 O2, Li(Ni) 0.6 Mn 0.2 Co 0.2 O2, etc.

[0062] Optionally, in one embodiment, the positive electrode sheet further includes an adhesive and a conductive agent. The adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-hexafluoropropylene-tetrafluoroethylene terpolymer, and tetrafluoroethylene-hexafluoropropylene copolymer. The conductive agent may be acetylene black, carbon fiber, carbon nanotubes, carbon black, graphene, etc.

[0063] In some embodiments, the positive electrode sheet is prepared as follows: the components used to prepare the positive electrode sheet, such as the positive active material, binder and any other components, are dispersed in a solvent such as N-methylpyrrolidone to form a positive electrode slurry; the positive electrode slurry is uniformly coated on both sides of a positive electrode current collector such as an aluminum foil; after baking, rolling, cutting and other processes, the positive electrode sheet can be obtained.

[0064] In this embodiment, the electrolyte acts as a conductor of ions between the positive and negative electrodes. The electrolyte can be liquid, gel-like, or entirely solid. In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent, wherein the electrolyte salt is a lithium salt.

[0065] Optionally, the aforementioned secondary battery includes any one of liquid lithium-ion batteries, quasi-solid-state lithium-ion batteries, quasi-solid-state lithium metal batteries, all-solid-state lithium-ion batteries, and solid-state lithium metal batteries.

[0066] In practical applications, the negative electrode, separator and positive electrode are stacked in sequence and wound to obtain a cell assembly. The cell assembly is then packaged to obtain a bare cell. After baking, the bare cell is injected with electrolyte, formed, resealed and sorted to obtain the above-mentioned secondary battery.

[0067] This application also proposes an electrical device, which includes the aforementioned secondary battery, serving as the power supply for the electrical device.

[0068] The above-described electrical equipment embodiment includes the aforementioned secondary battery and achieves the same technical effect. To avoid repetition, it will not be described again here. For relevant details, please refer to the description of the secondary battery embodiment.

[0069] To make the inventive objectives, technical solutions, and beneficial effects of this application clearer, the application is further described below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this application.

[0070] The present application will be described in detail below through embodiments.

[0071] Test methods (1) Capacity retention test: At 25℃, the battery was charged and discharged at 3C / 3C (the mainstream cycle rate) within a voltage range of 2.5~4.2V until the battery capacity was cycled 2000 times. The capacity retention rate of the battery after 2000 cycles was then calculated.

[0072] (2) Energy density test: Connect the battery to the test channel in the test cabinet, charge it to 4.2V at a rate of 0.05C, and then discharge it to 2.5V at a rate of 0.33C. The energy during the discharge process is E2, and the mass of the battery cell is m. Then the energy density = E2 / m.

[0073] (3) Charging rate performance test: Place the secondary battery in a constant temperature chamber at 25°C for a period of time (e.g., 4 hours) to reach thermal equilibrium; Discharge to 2.5V (0% SOC) with a constant current of 0.33C, let stand for 0.5h, then charge with a constant current and constant voltage of 0.33C, with an upper voltage limit of 4.2V and a cutoff current of 0.05C. Record the charging capacity C1, and then let stand for 0.5h. Then discharge at a constant current of 0.33C to 2.5V (0% SOC), let stand for 0.5h, and then charge at a constant current and constant voltage of 5C, with an upper voltage limit of 4.2V and a cutoff current of 0.05C. Record the charging capacity C2. Compared to the 0.33C charging capacity, the 5C charging capacity retention rate is C2 / C1×100%, which serves as a test indicator for charging rate performance.

[0074] (4) Tensile strength test: Cut the clean, flat negative electrode sheet to a specific size according to testing standards. Mount the sample in the clamps of the universal testing machine, ensuring proper clamping and preventing slippage or skewing. Set the tensile speed and stroke range of the testing machine; typically, the tensile speed is between 1 and 5 mm / min, depending on the standard or material properties. Start the testing machine and apply axial tensile force to the sample until it breaks. The testing machine will record the tensile force and displacement data, from which the tensile strength can be calculated. Tensile strength σ b= F / A (F is the maximum tensile force, and A is the original cross-sectional area of ​​the sample).

[0075] (5) Brinell hardness test: Cut a clean, flat negative electrode sheet to a specific size according to testing standards. Place the sample on the test stage of the hardness tester and apply an indenter (D is the indenter diameter, in mm) under a set load F (in N). Hold the indenter for a certain time (e.g., 10-15 seconds). After removing the load, measure the diameter d of the indentation, in mm. The Brinell hardness value HBW is then calculated as: HBW = 2F / (πD(D)). )).

[0076] (6) Conductivity test: Since the negative electrode is a micron-thin alloy, the four-probe method is used for conductivity testing. Cut a known thickness t (in meters) of a clean and flat negative electrode sheet into a certain size according to the test standard. Place the sample flat on the test stage, ensuring that the probe can contact the sample surface and that the sample is well fixed to avoid movement or deformation. Arrange the four probes at equal intervals to ensure that the probes are in perpendicular contact with the sample surface and avoid tilting. The two outer probes (1 and 4) carry a constant current I (such as 0.001A, 0.005A or 0.01A), and the two inner probes (2 and 3) measure the voltage and record the voltage value V (in V). After ensuring that the voltage is stable, read the data. Calculate the conductivity σ = (I / V) × (π / ln2) / t (unit: S / m).

[0077] Example 1 (1) Preparation of negative electrode sheet S1, aluminum-tin alloy Al 50 Sn 50 and pure copper and nickel-cobalt alloy Ni 80 Co 20 The mixture is placed into the crucible of the electric arc melting furnace according to the design ratio, so that the atomic ratio of Al:Sn:Ni:Co:Cu is 30:30:16:4:20. S2. Heat all raw materials to 1500℃ using an electric arc, and melt them repeatedly 3 times, each melting time being 30 minutes, to ensure that all raw materials are melted. S3. After solidification into an alloy ingot, the alloy ingot is reheated and melted to 1600℃ using a single-roller rapid cooling technology, and sprayed onto the surface of a cooling copper roller with a rotation speed of 4000rpm. After rapid cooling, a 12μm high-entropy alloy foil is obtained. S4. Through the laser beam, at 10 -4The surface of the high-entropy alloy foil is rapidly heated to 1600°C and then rapidly cooled through the foil's own thermal conductivity to obtain a modification layer with an average thickness of 1.5 μm on the surface of the high-entropy alloy Al-Sn-Cu-Ni-Co foil. The foil is then cut to obtain the negative electrode sheet.

[0078] (2) Preparation of positive electrode sheet NaNi, the positive electrode active material 0.33 Fe 0.33 Mn 0.33 O2, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 95:2.5:2.5, and solvent NMP is added. The mixture is stirred under vacuum to obtain a positive electrode slurry. The positive electrode slurry is evenly coated on both sides of the positive electrode current collector carbon-coated aluminum foil, dried at room temperature, and then transferred to an oven for further drying. Finally, the positive electrode sheet is obtained by rolling and cutting.

[0079] (3) Preparation of electrolyte Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1. Then, 1 mol / L NaPF6 was dissolved in the mixed organic solvent and mixed thoroughly to prepare an electrolyte.

[0080] (4) Preparation of secondary batteries The positive electrode, separator (12μm thick polypropylene separator), and negative electrode are stacked in sequence, then wound into a bare cell and installed in an aluminum shell. After top-side sealing, liquid injection, formation, sorting and other processes, a sodium-ion battery is obtained.

[0081] Example 2 The only difference from Example 1 is in the preparation process of the negative electrode sheet: Commercially available pure aluminum and pure copper, phosphorus powder, and nickel-cobalt alloy Ni 80 Co 20 The mixture is placed into the crucible of the induction melting furnace according to the design ratio, so that the atomic ratio of Al:P:Ni:Co:Cu is 30:35:8:2:25. All raw materials are heated to 1500℃ by coil induction and repeatedly melted 4 times, each melting time being 30 minutes, to ensure that all raw materials are melted. After solidification into an alloy ingot, the alloy ingot is reheated and melted to 1600°C using a single-roller rapid cooling technique, and then sprayed onto the surface of a cooling copper roller rotating at 5000 rpm. After rapid cooling, a 10μm high-entropy alloy foil is obtained. Through the laser beam, at 10 -4 The surface of the high-entropy alloy foil was rapidly heated to 1650°C and then rapidly cooled by the foil's own thermal conductivity, resulting in a modification layer with an average thickness of 1.2 μm on the surface of the high-entropy alloy Al-P-Cu-Ni-Co foil.

[0082] Example 3 The only difference from Example 1 is that, in the preparation process of the negative electrode sheet, the atomic ratio of the mixture Al:Sn:Ni:Co:Cu is adjusted to 20:32:20:8:20.

[0083] Example 4 The only difference from Example 3 is that, in the preparation process of the negative electrode sheet, phosphorus powder is added to the raw materials, and the atomic ratio of Al:Sn:P:Ni:Co:Cu is controlled to be 20:15:15:20:10:20.

[0084] Example 5 The only difference from Example 3 is that, in the preparation process of the negative electrode sheet: the raw materials are adjusted to be pure iron, pure manganese, pure chromium, pure titanium, pure vanadium, pure molybdenum, and pure tin, and the atomic ratio is controlled to be Fe:Mn:Cr:Ti:V:Mo:Sn=12:12:12:12:10:10:32, and the heating temperature is adjusted to be at least 2650℃ (exceeding the melting point of the highest melting point metal molybdenum, 2622℃).

[0085] Example 6 The difference from Example 3 is only that, in the preparation process of the negative electrode sheet: the raw materials are adjusted to be pure aluminum, pure copper, pure nickel, pure cobalt, pure antimony, pure bismuth, pure gallium, and pure indium, and the atomic ratio is controlled to Al:Cu:Ni:Co:Sb:Bi:Ga:In=20:20:14:14:8:8:8:8, and the heating temperature is adjusted to at least 1100℃ (exceeding the melting point of copper, the highest melting point metal, at 1085℃).

[0086] Examples 7-8 The only difference from Example 3 is that, in the preparation process of the negative electrode sheet, the atomic ratios of each element are adjusted to Al:Sn:Ni:Co:Cu=20:30:20:10:20 and Al:Sn:Ni:Co:Cu=20:35:20:5:20 respectively.

[0087] Example 9 The only difference from Example 3 is that, during the preparation of the negative electrode sheet, the laser irradiation time was adjusted to 10 seconds. -5 s, rapidly heats the surface of high-entropy alloy foil to 1500°C (fast scan, low power).

[0088] Example 10 The only difference from Example 3 is that, in the preparation process of the negative electrode sheet: the rotation speed of the cooling copper roller was adjusted to 5000 rpm, and the laser treatment time was 10 minutes. -5 s.

[0089] Examples 11-12 The only difference from Example 3 is that, in step S4 of preparing the negative electrode, the laser irradiation time is adjusted to 5*10. -4 The surface of the high-entropy alloy foil was rapidly heated to 1650°C, and the laser treatment time was 5*10 seconds. -5 The surface of the high-entropy alloy foil is rapidly heated to 1550°C.

[0090] Example 13 The only difference from Example 3 is that, in the preparation process of the positive electrode sheet: the positive electrode active material is adjusted to be a lithium ternary material Li(Ni) 1 / 3 Mn 1 / 3 Co 1 / 3 O2; During the preparation of the electrolyte, the salt is adjusted to LiPF6.

[0091] Comparative Example 1 The difference between Comparative Example 1 and Example 3 is that, during the preparation of the negative electrode sheet, the laser irradiation time was adjusted to 10 minutes. -3 The surface of the high-entropy alloy foil is rapidly heated to 1700°C (slow scan, high power).

[0092] Comparative Example 2 The difference between Comparative Example 2 and Example 3 is that step S4 is omitted in the preparation process of the negative electrode sheet, and the high-entropy alloy foil is directly cut to obtain the negative electrode sheet.

[0093] The process parameters for each embodiment and comparative example are shown in Table 1.

[0094] Table 1

[0095] The tensile strength, Brinell hardness and conductivity of the negative electrode sheets of each embodiment and comparative example were tested, and the test data are shown in Table 2.

[0096] Energy density, rate performance, and capacity retention were tested on the secondary batteries of each embodiment and comparative example. The test data are shown in Table 2.

[0097] Table 2

[0098] The experimental results from Examples 1-13 and Comparative Examples 1 and 2 show that the embodiments of this application use a high-entropy alloy matrix including the first and second elements as the main body of the negative electrode sheet, ensuring high capacity, high conductivity, and good cycle performance of the negative electrode sheet. Simultaneously, a modification layer including an amorphous alloy is provided on the surface of the high-entropy alloy matrix. Since the amorphous alloy lacks grain boundaries, the series resistance can be reduced, thereby reducing the battery resistance. Furthermore, because the amorphous alloy is in a metastable state, its surface energy is relatively high, and dendrites will grow into the interior of the amorphous alloy after nucleation, thereby reducing the risk of dendrites piercing the separator and providing higher safety. Therefore, the embodiments of this application improve the problem that the existing negative electrode structure of ion batteries cannot simultaneously achieve high energy density, excellent rate performance, and long cycle life.

[0099] Although preferred embodiments of the present application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present application.

[0100] The above provides a detailed description of a secondary battery and electrical device provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A secondary battery, characterized in that, Includes a negative electrode sheet, wherein the negative electrode sheet comprises: A high-entropy alloy matrix, wherein the high-entropy alloy matrix comprises a first element and a second element, wherein the first element comprises at least four of Al, Cu, Co, Ni, Fe, Mn, Cr, Ti, V, and Mo, and the second element comprises at least one of Sn, P, Sb, Bi, Ga, and In; A modification layer is disposed on the surface of the high-entropy alloy substrate, wherein the modification layer comprises an amorphous alloy.

2. The secondary battery according to claim 1, characterized in that, The first element includes Cu, Ni, Co, and Al, and the second element includes Sn and / or P.

3. The secondary battery according to claim 1, characterized in that, The amorphous alloy includes at least one of Cu-Sn amorphous alloy, Ni-Sn amorphous alloy, Co-Sn amorphous alloy, Al-Sn amorphous alloy, Al-Ni amorphous alloy, Al-Cu amorphous alloy, Cu-P amorphous alloy, Ni-P amorphous alloy, Co-P amorphous alloy, and Al-P amorphous alloy.

4. The secondary battery according to claim 1, characterized in that, The atomic percentage of the second element in the high-entropy alloy matrix is ​​30% to 35%.

5. The secondary battery according to claim 2, characterized in that, The atomic percentages of Cu, Ni, Co, Al, Sn, and P in the negative electrode are independently 5% to 35%.

6. The secondary battery according to claim 1, characterized in that, The modification layer further includes a nanocrystalline alloy, which includes at least one of Cu-Sn nanocrystalline alloy, Ni-Sn nanocrystalline alloy, Co-Sn nanocrystalline alloy, Al-Sn nanocrystalline alloy, Al-Ni nanocrystalline alloy, Al-Cu nanocrystalline alloy, Cu-P nanocrystalline alloy, Ni-P nanocrystalline alloy, Co-P nanocrystalline alloy, and Al-P nanocrystalline alloy.

7. The secondary battery according to claim 1, characterized in that, The thickness of the modified layer is 0.45 μm to 1.5 μm; and / or The thickness of the high-entropy alloy matrix is ​​4μm~12μm.

8. The secondary battery according to claim 6, characterized in that, The average particle size of the nanocrystalline alloy is 1 nm to 5 nm.

9. The secondary battery according to any one of claims 1 to 8, characterized in that, At least one of the following conditions must be met: (I) The tensile strength of the negative electrode sheet is 750MPa~850MPa; and / or (II) The Brinell hardness of the negative electrode sheet is 150 HB to 220 HB; and / or (III) The conductivity of the negative electrode is 10. 4 S / m~10 6 S / m.

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

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