Secondary battery and electric device

Abstract

This application discloses a secondary battery and an electrical device. The secondary battery of this application includes: a negative electrode sheet, which comprises a negative electrode current collector layer, a negative electrode active material layer disposed on the negative electrode current collector layer, and a first negative electrode protective layer disposed on one side of the negative electrode current collector layer. The first negative electrode protective layer comprises metal oxide, silicon oxide, and metal phosphate. The negative electrode active material layer is disposed between the negative electrode current collector layer and the first negative electrode protective layer. The first negative electrode protective layer disposed on one side of the negative electrode sheet of this application can effectively reduce the risk of thermal runaway during a short circuit within the battery, prevent the battery from catching fire or exploding, and improve the battery's safety performance.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, specifically to secondary batteries and electrical devices. Background Technology

[0002] As a zero-emission, green, and environmentally friendly renewable energy source, batteries are gradually replacing traditional drive systems that rely primarily on fossil fuels. Currently, rechargeable batteries are the main power source for new energy vehicles. Compared to cylindrical and prismatic batteries, pouch silicon-based power batteries can achieve higher energy densities. However, due to the characteristics of their packaging materials and their high energy density, the damage caused by severe impacts, abuse leading to short circuits, overcharging, and over-discharging that trigger thermal runaway is also greater. Therefore, the safety of power batteries is of paramount importance.

[0003] Therefore, there is an urgent need to provide a secondary battery to overcome the shortcomings of the existing technology. Summary of the Invention

[0004] The purpose of this application is to provide a secondary battery and an electrical device. The secondary battery of this application improves the battery's safety performance by providing a first negative electrode protection layer on the negative electrode plate.

[0005] This application provides a secondary battery, comprising:

[0006] The negative electrode sheet includes a negative electrode current collector layer, a negative electrode active material layer disposed on the negative electrode current collector layer, and a first negative electrode protective layer disposed on one side of the negative electrode current collector layer. The first negative electrode protective layer includes metal oxide, silicon oxide, and metal phosphate. The negative electrode active material layer is disposed between the negative electrode current collector layer and the first negative electrode protective layer.

[0007] Optionally, in some embodiments of this application, the metal oxide includes Al2O3, TiO2, LLZO (Li7La3Zr2O) 12 ( ), V2O5, Cr2O3, GeO2, ZrO2, TeO2.

[0008] Optionally, in some embodiments of this application, the silicon oxide includes at least one of SiO2 and SiO.

[0009] Optionally, in some embodiments of this application, the metal phosphate includes LAGP (lithium aluminum germanium phosphate, Li...). 1.5 Al 0.5 Ge 1.5 (Po4)3), LiAlPO4, LiTiPO4, LiAl x Ti yAt least one of PO4 and LiPO4, wherein 0.2≤x≤0.4 and 1.6≤y≤1.8.

[0010] Optionally, in some embodiments of this application, the negative electrode sheet further includes a second negative electrode protective layer disposed on the other side of the negative electrode current collector, the second negative electrode protective layer comprising a lithium-containing solid electrolyte.

[0011] Optionally, in some embodiments of this application, the lithium-containing solid electrolyte includes at least one of LLZO, LPS, and LPSC.

[0012] Optionally, in some embodiments of this application, the content of the lithium-containing solid electrolyte is 80wt% to 95wt% based on the mass of the second negative electrode protective layer.

[0013] Optionally, in some embodiments of this application, the lithium-containing solid electrolyte includes one or more of LLZO, LPS, or LPSC.

[0014] Optionally, in some embodiments of this application, the porosity of the first negative electrode protective layer or the second negative electrode protective layer is 20% to 50%.

[0015] Optionally, in some embodiments of this application, the thickness H1 of the first negative electrode protective layer is 0.5μm-50μm.

[0016] Optionally, in some embodiments of this application, the thickness H2 of the second negative electrode protective layer is 0.5μm-50μm.

[0017] Optionally, in some embodiments of this application, the ratio of the thickness H1 of the first negative electrode protective layer to the thickness H2 of the second negative electrode protective layer is 0.9 to 1.1.

[0018] Optionally, in some embodiments of this application, the secondary battery further includes:

[0019] A positive electrode sheet, comprising a positive current collector layer, a positive active material layer disposed on the positive current collector layer, and a positive protective layer covering the surface of the positive active material layer.

[0020] The materials of the positive electrode protective layer include Al2O3, SiO2, TiO2, LATP (lithium aluminum titanium phosphate), and LLZO (lithium lanthanum zirconium oxide, chemical formula Li7La3Zr2O). 12 At least one of ) and LAG (lithium aluminum germanium).

[0021] Optionally, in some embodiments of this application, the thickness of the positive electrode protective layer is 0.5 μm to 50 μm.

[0022] In some embodiments of this application, the thickness of the positive electrode protective layer is 5 μm to 20 μm.

[0023] In addition, this application also provides an electrical device, including the secondary battery as described above, wherein the secondary battery serves as the power supply for the electrical device.

[0024] The beneficial effects of this application are as follows: Compared with the prior art, the secondary battery of this application includes a negative electrode sheet, which includes a negative electrode current collector layer, a negative electrode active material layer disposed on the negative electrode current collector layer, and a first negative electrode protective layer disposed on one side of the negative electrode current collector layer. The first negative electrode protective layer includes metal oxide, silicon oxide, and metal phosphate, and the negative electrode active material layer is disposed between the negative electrode current collector layer and the first negative electrode protective layer. The secondary battery of this application has a first negative electrode protective layer disposed on one side of the negative electrode sheet, which can effectively reduce the risk of thermal runaway during internal short circuits, prevent battery fire and explosion, and improve battery safety performance. Detailed Implementation

[0025] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. In addition, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and conciseness, and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the scope description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. In addition, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0026] To address the technical challenge of further improving the safety of power batteries, this application proposes improving battery safety performance by setting a protective layer on the surface of the negative electrode sheet.

[0027] In some embodiments, this application provides a secondary battery and an electrical device. These are described in detail below. It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments.

[0028] This application provides a secondary battery including a negative electrode sheet. The negative electrode sheet includes a negative electrode current collector layer, a negative electrode active material layer disposed on the negative electrode current collector layer, and a first negative electrode protective layer disposed on one side of the negative electrode current collector layer. The first negative electrode protective layer includes metal oxide, silicon oxide, and metal phosphate. The negative electrode active material layer is disposed between the negative electrode current collector layer and the first negative electrode protective layer. In other words, in this application, the negative electrode active material layer is disposed on the negative electrode current collector layer, and the negative electrode protective layer covers the surface of the negative electrode active material layer. That is, the negative electrode protective layer is disposed on the surface of the negative electrode active material layer opposite to the negative electrode current collector layer.

[0029] The material of the first negative electrode protective layer in this application possesses ionic conductivity and electronic insulation. Covering the surface of the negative electrode active material layer, it effectively prevents direct contact between the negative electrode active material and the positive electrode active material and positive electrode current collector under conditions of collision, compression, or other deformations causing internal battery deformation. This effectively reduces the risk of thermal runaway during internal short circuits, preventing battery fires and explosions and improving safety performance. In this embodiment, silicon oxide possesses excellent mechanical and thermal stability properties, which can improve the thermal stability and mechanical properties of the first negative electrode protective layer, further enhancing battery safety performance. Furthermore, silicon oxide can absorb moisture from the liquid electrolyte, reducing side reactions within the battery. Metal oxides and metal phosphates also have excellent ionic conductivity, improving ion transport efficiency and enhancing battery electrochemical performance.

[0030] In some embodiments, the metal oxide includes at least one of Al2O3, TiO2, LLZO, V2O5, Cr2O3, GeO2, ZrO2, and TeO2.

[0031] In some embodiments, the silicon oxide includes at least one of SiO2 and SiO.

[0032] In some embodiments, metal phosphates include LAGP (lithium aluminum germanium phosphate), LiAlPO4, LiTiPO4, and LiAl x Ti y At least one of PO4 and LiPO4, wherein 0.2≤x≤0.4 and 1.6≤y≤1.8.

[0033] This application further protects the electrodes by selecting the material composition of the protective layer, thus preventing battery thermal runaway. It effectively avoids problems such as volume expansion / contraction, electrolyte wettability, inhibition of lithium dendrite growth, and electrode interface side reactions during cell charging and discharging. While ensuring battery rate performance, the first negative electrode protective layer effectively prevents electrode interface side reactions during cell charging and discharging. In the event of mechanical abuse, it prevents direct contact between the positive and negative electrode active material layers, thereby avoiding the possibility of battery fire and explosion.

[0034] In some embodiments, the mass ratio of silicon oxide, metal oxide, and metal phosphate in the first negative electrode protective layer is 1:(3-4):(5-6). Within this ratio range, both the ionic conductivity and mechanical properties of the first negative electrode protective layer can be considered. This is beneficial for balancing the safety and electrochemical performance of the battery.

[0035] In some embodiments, the negative electrode sheet further includes a second negative electrode protective layer disposed on the other side of the negative electrode current collector, the second negative electrode protective layer comprising a lithium-containing solid electrolyte.

[0036] In this application, the first or second negative electrode protective layer can be deposited on the negative electrode sheet using chemical deposition or magnetron sputtering. The lithium-containing solid electrolyte in the second negative electrode protective layer of this application acts as an ion conductor, further improving battery safety, effectively reducing interfacial impedance, and preventing battery thermal runaway. In some embodiments, the second negative electrode protective layer further includes an elastic organic polymer, which includes at least one of polypropylene, polyurethane, polyolefin, polystyrene, styrene, and polytetrafluoroethylene, and the elastic organic polymer accounts for 5% to 20% of the total mass of the second negative electrode protective layer. The presence of the elastic organic polymer enables the negative electrode sheet to have a certain deformation capacity, preventing cracks caused by material expansion during battery cycling and improving battery cycle performance.

[0037] In some embodiments, the lithium-containing solid electrolyte includes one or more of lithium lanthanum zirconium oxide (LLZO), LPS (amorphous 75Li2S-25P2S5), and LPSC (Li6PS5Cl).

[0038] In some embodiments, the porosity of the first negative electrode protective layer or the second negative electrode protective layer is 20% to 50%.

[0039] The porosity of the first or second negative electrode protective layer in this application is within this range, which can improve the wetting performance of the negative electrode sheet, enhance the performance of lithium ions entering the negative electrode material, improve the lithium ion insertion / extraction rate, and improve the power performance of the battery.

[0040] In some embodiments, the porosity (%) of the first negative electrode protective layer or the second negative electrode protective layer is any value or a range of any two values ​​among 20, 25, 30, 35, 40, 45, and 50.

[0041] In some embodiments, the thickness H1 of the first negative electrode protective layer is 0.5 μm to 50 μm; preferably, the thickness H1 of the first negative electrode protective layer is 5 μm to 20 μm. For example, the thickness H1 of the first negative electrode protective layer is any value or a range of any two values ​​selected from 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm.

[0042] In some embodiments, the thickness H2 of the second negative electrode protective layer is 0.5 μm to 50 μm; preferably, the thickness H2 of the second negative electrode protective layer is 5 μm to 20 μm. For example, the thickness H2 of the second negative electrode protective layer is any value or a range of any two values ​​selected from 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm.

[0043] In some embodiments, the ratio of the thickness H1 of the first negative electrode protective layer to the thickness H2 of the second negative electrode protective layer is 0.9 to 1.1.

[0044] In some embodiments, the ratio of the thickness H1 of the first negative electrode protective layer to the thickness H2 of the second negative electrode protective layer is any value or a range of any two values ​​from 0.9, 0.95, 1.0, 1.05, and 1.1.

[0045] The thickness and ratio of the first negative electrode protective layer and the second negative electrode protective layer in this application are within the above-mentioned range, indicating that the thickness settings of the first negative electrode protective layer and the second negative electrode protective layer are not much different, and the set values ​​are between 0.5μm and 50μm. This can ensure that the protective layer has a suitable porosity, while ensuring that the protective layer has low impedance, which is conducive to the transmission of lithium ion insertion and extraction process and improves the battery rate performance.

[0046] In some embodiments, the negative electrode active material layer comprises graphite and silicon-based materials.

[0047] In some embodiments, the silicon-based material can be elemental silicon or silicon dioxide, or other types of silicon-based oxides. Blending silicon-based materials into graphite as a negative electrode active material can effectively improve the energy density of the battery and enhance its range.

[0048] In some embodiments, the silicon-based material accounts for 1-30% of the mass of the negative electrode active material. The proportion of silicon-oxygen material in the negative electrode active material of this application falls within this range, ensuring high energy density while preventing excessive battery expansion and maintaining battery safety. In some embodiments, the mass fraction of silicon-based material in the negative electrode active material is 9wt%-25wt%. For example, the mass fraction of silicon-based material in the negative electrode active material layer is any value or any combination of two values ​​from 1wt%, 2wt%, 3wt%, 5wt%, 8wt%, 10wt%, 13wt%, 15wt%, 17wt%, 20wt%, 22wt%, 24wt%, 25wt%, 26wt%, 28wt%, or 30wt%.

[0049] In some embodiments, the secondary battery further includes a positive electrode sheet, which comprises a positive current collector layer, a positive active material layer, and a positive protective layer. The positive protective layer comprises at least one of Al2O3, SiO2, TiO2, LATP, LLZO, and LAG. Further, the positive active material layer is disposed on the positive current collector layer. The positive protective layer covers the surface of the positive active material layer. In this embodiment, the provision of a positive protective layer on the positive electrode sheet further reduces the risk of thermal runaway during internal short circuits, preventing battery fire and explosion.

[0050] In some embodiments, the thickness of the positive electrode protective layer is 0.5 μm-50 μm; preferably, the thickness of the positive electrode protective layer is 5 μm-20 μm. For example, the thickness of the positive electrode protective layer is any value or any combination of two values ​​from 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm.

[0051] In some embodiments, the positive electrode active material layer includes a positive electrode active material. The mass fraction of the positive electrode active material in the positive electrode active material layer is 80 wt%-99 wt%; for example, the mass fraction can be any value or a range of any two values ​​from 80 wt%, 81 wt%, 82 wt%, 83 wt%, 85 wt%, 88 wt%, 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, or 99 wt%. Further, the positive electrode active material includes at least one of lithium cobalt oxide material, ternary material, and lithium phosphate material.

[0052] In some embodiments, the positive electrode active material layer further includes a conductive agent, which includes at least one selected from carbon black (SP), carbon nanotubes (CNTs), and graphene. Further, the mass fraction of the conductive agent in the positive electrode active material layer is 1 wt% to 10 wt%. For example, the mass fraction of the conductive agent in the positive electrode active material layer can be any value or a range of any two values ​​from 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%.

[0053] Furthermore, the positive electrode active material layer also includes a binder, the mass fraction of which is 0wt%-10wt%. For example, the mass fraction of the binder in the positive electrode active material layer is any value or any combination of two values ​​from 0wt%, 0.1wt%, 0.2wt%, 0.5wt%, 0.8wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, 8.5wt%, 9wt%, 9.5wt%, or 10wt%.

[0054] In some embodiments, the adhesive is PVDF.

[0055] In some embodiments, the secondary battery further includes a separator, which comprises at least one of a base membrane, ceramic, and a binder layer. In the embodiments of this application, the ceramic-coated separator can reduce separator shrinkage, prevent the short circuit point from expanding, and also play a role in improving safety to a certain extent.

[0056] In some embodiments, the positive electrode current collector layer can be aluminum foil. The negative electrode current collector layer can be copper foil.

[0057] This application embodiment also provides an electrical device, which includes the aforementioned secondary battery, and the secondary battery serves as the power supply for the electrical device.

[0058] This application has undergone multiple experiments, and some of the test results are presented here for reference to further describe the invention in detail. The following is a detailed description in conjunction with specific embodiments.

[0059] Example 1

[0060] This embodiment provides a secondary battery, including a positive electrode and a negative electrode. The positive electrode includes a positive current collector, a positive active material layer, and a positive protective layer.

[0061] Preparation of negative electrode sheet:

[0062] A negative electrode active material (composed of SiO2 and graphite, with SiO2 accounting for 15% of the negative electrode active material by mass), conductive carbon black (SP), CMC, and SBR are mixed in a mass ratio of 96.3:0.7:1.1:1.9, and then thoroughly mixed in deionized water. After uniform mixing, the mixture is coated onto both surfaces of a copper foil. The electrode is then dried, rolled, slit, and cut to obtain the electrode sheet. A mixture of SiO2, Al2O3, and LAGP in a mass ratio of 1:4:5 is uniformly mixed and deposited onto the surface of one active material layer of the electrode sheet using a magnetron sputtering machine. LPSC is then deposited onto the surface of the other active material layer of the electrode sheet using magnetron sputtering, resulting in an electrode sheet with a first negative electrode protective layer and a second negative electrode protective layer. A polypropylene solution (elastic organic polymer) is sprayed onto the second negative electrode protective layer, and the sheet is dried to obtain the negative electrode sheet. The thickness of both the first and second negative electrode protective layers is 25 μm, and the porosity of both is 35%.

[0063] Preparation of the positive electrode sheet:

[0064] NCM811, conductive agent (Super P), and PVDF (PVDF5130) in a mass ratio of 97:0.7:2.3 were added to NMP and thoroughly mixed. After uniform mixing, the mixture was coated on both sides onto an aluminum foil with a thickness of 10 μm. The electrode was then dried, rolled, slit, and cut to obtain the positive electrode.

[0065] The diaphragm is a polyethylene film.

[0066] Electrolyte preparation:

[0067] Vinylene carbonate, ethyl methyl carbonate, and dimethyl carbonate were mixed in a mass ratio of 1:1:1, and then lithium hexafluorophosphate was added. The lithium hexafluorophosphate content was 12% based on the mass of the electrolyte.

[0068] Preparation of secondary batteries:

[0069] The positive electrode, negative electrode, separator and other battery components prepared in this application are assembled and then subjected to processes such as shaping, baking, packaging, liquid injection, formation and capacity testing to obtain a soft-pack battery.

[0070] The specific parameters for this embodiment are shown in Table 1.

[0071] Examples 2-5 were prepared using the same method as Example 1, except that the raw materials for the first and second negative electrode protective layers were adjusted during the preparation of the negative electrode sheet.

[0072] Examples 6-9: The preparation method is the same as in Example 1, except that the proportion of SiO2 in the negative electrode active material is adjusted during the preparation of the negative electrode sheet.

[0073] Examples 10-14: The preparation method is the same as in Example 1, except that the working time of the magnetron sputtering machine is adjusted during the preparation of the negative electrode sheet to adjust the thickness of the first negative electrode protective layer and the second negative electrode protective layer.

[0074] Examples 15-18: The preparation method is the same as in Example 1, except that the working time of the magnetron sputtering machine is adjusted to adjust the thickness of the second negative electrode protective layer, thereby obtaining negative electrode sheets with different non-protective layer ratios.

[0075] Examples 19-24: The preparation method is the same as in Example 1, except that the power of the magnetron sputtering machine is adjusted to adjust the porosity of the first negative electrode protective layer.

[0076] Examples 25-26: The preparation method is the same as in Example 1, except that the amount of LPSC deposited is adjusted to adjust the proportion of LPSC in the second negative electrode protective layer.

[0077] Example 27: The preparation method is the same as in Example 1, except that the step of preparing a second negative electrode protective layer is not included in the preparation of the negative electrode sheet.

[0078] Comparative Example 1: The preparation method is the same as in Example 1, except that the steps of preparing the first and second protective layers are not performed during the preparation of the negative electrode sheet.

[0079] Experimental Example 1

[0080] The safety of the secondary batteries prepared according to Examples 1-27 was further tested, and the specific test results are shown in Table 2.

[0081] Safety tests include needle penetration test, 180°C hot chamber test, and overcharge test, among which:

[0082] Needle penetration test method: Use a 3mm (45°) steel needle to penetrate the battery through the center of the wide side at a speed of 25mm / s, and observe the battery with the needle inside for 1 hour;

[0083] 180℃ Hot Chamber Test Method: Place the battery in the temperature chamber and heat it under the following conditions: The temperature chamber is heated from the ambient temperature to 180℃±2℃ at a rate of 5℃ / min, and the temperature is maintained for 30 minutes before heating is stopped.

[0084] Overcharge test method: Charge the battery with a constant current until it reaches 1.5 times the charging termination voltage, then stop charging.

[0085] Battery cycle performance test method: At room temperature, let the battery rest for 5 minutes, charge it at a constant current rate of 1C to 4.2V, then charge it at a constant voltage rate until the current is less than or equal to 0.05C, let it rest for 5 minutes, and then discharge it at a constant current rate of 1C to 3.0V. This is one charge-discharge cycle. Perform the above steps on the battery 500 times, record the battery discharge capacity of the 1st and 500th cycles, and calculate the battery capacity retention rate of the 500th cycle.

[0086] Table 1

[0087]

[0088]

[0089]

[0090] Table 2

[0091]

[0092]

[0093] As can be seen from the above data, in the case of mechanical abuse leading to internal short circuit, the protective coating on the surface of the negative electrode sheet of the secondary battery of this application can effectively reduce the risk of thermal runaway during internal short circuit and prevent the battery from catching fire and exploding. At the same time, the presence of the safety coating is conducive to the performance of battery cycle.

[0094] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0095] The above provides a detailed description of a secondary battery and electrical device provided in the embodiments of 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, comprising a negative electrode and a positive electrode, characterized in that, The negative electrode sheet includes a negative electrode current collector layer, a negative electrode active material layer disposed on the negative electrode current collector layer, and a first negative electrode protective layer disposed on one side of the negative electrode current collector layer. The first negative electrode protective layer includes metal oxide, silicon oxide, and metal phosphate. The negative electrode active material layer is disposed between the negative electrode current collector layer and the first negative electrode protective layer. The mass ratio of the silicon oxide, the metal oxide, and the metal phosphate is 1:(3-4):(5-6); The metal phosphate includes at least one of LAGP and LiTiPO4.

2. The secondary battery according to claim 1, characterized in that, The metal oxide includes at least one of Al2O3, TiO2, LLZO, V2O5, Cr2O3, GeO2, ZrO2, and TeO2; The silicon oxide includes at least one of SiO2 and SiO.

3. The secondary battery according to claim 1, characterized in that, The negative electrode active material layer is disposed on both surfaces of the negative electrode current collector layer; The negative electrode sheet also includes a second negative electrode protective layer disposed on the other side of the negative electrode current collector, wherein the second negative electrode protective layer and the first negative electrode protective layer are disposed on different negative electrode active material layers; The second negative electrode protective layer includes a lithium-containing solid electrolyte.

4. The secondary battery according to claim 3, characterized in that, The lithium-containing solid electrolyte includes one or more of LLZO, LPS, or LPSC.

5. The secondary battery according to claim 3, characterized in that, Based on the mass of the second negative electrode protective layer, the content of the lithium-containing solid electrolyte is 80wt%~95wt%.

6. The secondary battery according to claim 3, characterized in that, The porosity of the first negative electrode protective layer is 20%~50%.

7. The secondary battery according to claim 3, characterized in that, The thickness H1 of the first negative electrode protective layer is 0.5 μm to 50 μm; and / or, The thickness H2 of the second negative electrode protective layer is 0.5μm~50μm.

8. The secondary battery according to claim 7, characterized in that, The ratio of the thickness H1 of the first negative electrode protective layer to the thickness H2 of the second negative electrode protective layer is 0.9 to 1.

1.

9. The secondary battery according to any one of claims 1 to 8, characterized in that, The negative electrode active material layer includes a negative electrode active material, which includes graphite and silicon-based materials.

10. The secondary battery according to claim 9, characterized in that, Based on the mass of the negative electrode active material, the mass ratio of the silicon-based material is 1-30%.

11. Electrical equipment, characterized in that, Includes a secondary battery as described in any one of claims 1 to 10, wherein the secondary battery serves as the power supply for the electrical equipment.

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