Secondary battery, preparation method thereof and electric device

Abstract

The invention provides a secondary battery, a preparation method thereof and a power utilization device. The secondary battery comprises a positive pole piece, a composite diaphragm and a negative pole piece which are sequentially stacked, the composite diaphragm comprises a porous base membrane, a ceramic layer and a first non-liquid electrolyte layer which are arranged in a laminated manner; the thickness T1 of the porous base membrane is smaller than or equal to 4 microns, and pores of the porous base membrane are filled with a second non-liquid electrolyte. The secondary battery provided by the invention has relatively high energy density and relatively good rate capability and cycle performance.

Description

[0001] Cross-references

[0002] This application claims priority to Chinese Patent Application No. 202411167027.X, filed on August 23, 2024, entitled “Secondary Battery and Method for Preparation Thereof, Electrical Device”, which is incorporated herein by reference in its entirety. Technical Field

[0003] This application relates to the field of secondary battery technology, and in particular to a secondary battery, its preparation method, and an electrical device thereof. Background Technology

[0004] In recent years, as the application scope of secondary batteries has become increasingly wide, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles and electric vehicles.

[0005] Solid-state batteries use solid electrolytes instead of organic electrolytes, avoiding safety hazards caused by electrolyte leakage and other issues. This significantly improves battery safety performance and better meets the future development needs of electric vehicles and large-scale energy storage. With the rapid development of solid-state battery technology, higher requirements are being placed on its energy density and cycle performance.

[0006] Therefore, seeking a solid-state battery with high energy density and good cycle performance is one of the key areas of focus for those skilled in the art. Summary of the Invention

[0007] This application was made in view of the aforementioned problems, and one of its objectives is to provide a secondary battery with high energy density and good cycle performance. Accordingly, a method for preparing the aforementioned secondary battery and an electrical device using the aforementioned secondary battery are provided.

[0008] To achieve the above objectives, the first aspect of this application provides a secondary battery, comprising: a positive electrode, a composite separator, and a negative electrode stacked sequentially.

[0009] The composite membrane comprises a porous base membrane, a ceramic layer, and a first non-liquid electrolyte layer stacked together; the thickness T1 of the porous base membrane is ≤4μm, and the pores of the porous base membrane are filled with a second non-liquid electrolyte.

[0010] A composite separator is formed by stacking a porous base membrane (with a thickness of less than 4 μm), a ceramic layer, and a first non-liquid electrolyte layer, with a second non-liquid electrolyte filling the pores of the porous base membrane. The porous base membrane provides support for the first non-liquid electrolyte layer, acting as a skeletal support and mitigating the degradation of battery cycle performance caused by the breakage and collapse of solid electrolyte powder during battery cycling. By filling the pores of the porous base membrane with the second non-liquid electrolyte, in conjunction with the first non-liquid electrolyte layer on the base membrane surface, the composite separator achieves high ionic conductivity and flexibility even at a very thin thickness, thereby improving the energy density and rate performance of the secondary battery. This secondary battery exhibits high energy density, good rate performance, and good cycle performance.

[0011] In any embodiment, the puncture resistance of the porous base membrane is 0.7N or more, optionally 0.9N or more, and further optionally 1.0N or more.

[0012] In any embodiment, the thickness T1 of the porous base membrane and the thickness T of the composite separator satisfy 0.02≤T1 / T≤0.33.

[0013] In any embodiment, the positive electrode sheet includes a positive current collector, and the ratio of the thickness of the composite separator to the thickness of the positive current collector is 0.5~4:1, optionally 1.0~3.2:1.

[0014] In any embodiment, the energy density of the secondary battery is ≥250Wh / kg, and the amount of free electrolyte in the secondary battery is ≤0.1mg / Ah.

[0015] In any embodiment, the porosity of the porous base membrane is P1, the porosity of the composite separator is P2, and the P2 / P1 ratio is 0.05~0.9. This allows the composite separator to possess excellent ionic conductivity while maintaining a relatively thin thickness, resulting in a secondary battery with high energy density, good rate performance, and good cycle performance.

[0016] In any embodiment, P2 / P1 is 0.1 to 0.5. This further improves the ionic conductivity of the composite membrane, thereby enhancing the energy density, rate performance, and cycle performance of the secondary battery.

[0017] In any embodiment, the porosity P1 of the porous base membrane is 20%~70%. This allows lithium ions to pass smoothly through the porous base membrane during battery charging and discharging, giving the composite separator high ionic conductivity and enabling the secondary battery to have good rate performance.

[0018] In any embodiment, the porosity P2 of the composite membrane is 5% to 50%.

[0019] In any embodiment, the thickness of the porous base membrane is 1 μm to 3.5 μm. Thus, the porous base membrane has a relatively thin thickness, which, while providing effective skeletal support for the first non-liquid electrolyte layer, can shorten the ion transport path, improve the ionic conductivity of the composite membrane, and thereby enhance the rate performance and energy density of the secondary battery.

[0020] In any embodiment, the thickness of the porous base film is 1.2 μm to 3 μm.

[0021] In any embodiment, the thickness of the porous base film is 1.5 μm to 3 μm.

[0022] In any embodiment, the pore size of the porous base membrane is 50 nm to 300 nm. This enables the composite separator to possess high ionic conductivity, thereby improving the rate performance and energy density of the secondary battery.

[0023] In any embodiment, the thickness of the first non-liquid electrolyte layer is 5 μm to 20 μm.

[0024] In any embodiment, the thickness of the composite separator is 10 μm to 50 μm. Thus, the overall thickness of the composite separator is very thin, while possessing excellent ionic conductivity, which can improve the energy density and rate performance of the secondary battery.

[0025] In any embodiment, the thickness of the composite membrane is 20 μm to 50 μm.

[0026] In any embodiment, the materials of the first non-liquid electrolyte layer and the second non-liquid electrolyte are each independently a gel electrolyte or a solid electrolyte.

[0027] In any embodiment, the first non-liquid electrolyte layer and the second non-liquid electrolyte may be made of the same or different materials.

[0028] In any embodiment, the materials of the first non-liquid electrolyte layer and the second non-liquid electrolyte include one or more of inorganic solid electrolytes and polymer solid electrolytes, wherein the inorganic solid electrolyte includes one or more of sulfide solid electrolytes and oxide solid electrolytes.

[0029] In any embodiment, the sulfide solid electrolyte includes Li2S-P2S5 and Li2S-P2S5-MS. x Li 10 GeP2S 12 Li 10 SiP2S 12 and PEO / Li 10GeP2S 12 One or more of / SN.

[0030] In any embodiment, the oxide solid electrolyte includes one or more of lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium lanthanum zirconium titanium oxide, lithium titanium aluminum phosphate, lithium zinc germanate, lithium germanium aluminum phosphate, lithium boron oxide, lithium phosphate, lithium aluminum titanium phosphate, and lithium nitride.

[0031] In any embodiment, the polymer solid electrolyte includes one or more of the following: PEO-based solid electrolyte, PAN-based solid electrolyte, PMMA-based solid electrolyte, PVDF-based solid electrolyte, PEO-PAN-based solid electrolyte, PEO-PMMA-based solid electrolyte, PEO-PVDF-based solid electrolyte, PMMA-PVDF-based solid electrolyte, PMMA-PAN-based solid electrolyte, PAN-PVDF-based solid electrolyte, PEO-PAN-PMMA-based solid electrolyte, PEO-PVDF-PMMA-based solid electrolyte, PEO-PAN-PVDF-based solid electrolyte, and PAN-PMMA-PVDF-based solid electrolyte. Thus, the polymer solid electrolyte exhibits good viscoelasticity and low weight, enabling the composite separator to maintain good flexibility and better adapt to wound battery structures, resulting in improved applicability.

[0032] In any embodiment, the first non-liquid electrolyte layer comprises an oxide solid electrolyte, and the second non-liquid electrolyte comprises a sulfide solid electrolyte. Thus, while improving the ionic conductivity of the composite separator and enhancing the rate performance of the secondary battery, the secondary battery also exhibits good stability.

[0033] In any embodiment, the thickness of the ceramic layer is 1 μm to 5 μm. This effectively enhances the strength of the composite membrane, suppresses thermal shrinkage of the porous base membrane, and inhibits the growth of lithium / sodium dendrites, thus mitigating the risk of dendrites piercing the composite membrane.

[0034] In any embodiment, the ceramic layer contains a non-liquid electrolyte, and / or the first non-liquid electrolyte layer contains ceramic particles.

[0035] In any embodiment, the ceramic layer contains a non-liquid electrolyte, and the first non-liquid electrolyte layer contains ceramic particles.

[0036] In any embodiment, the ceramic layer is disposed between the porous base membrane and the first non-liquid electrolyte layer.

[0037] In any embodiment, the composite separator further includes an adhesive layer comprising an adhesive, the adhesive layer being located on the outermost side of the composite separator. Thus, the adhesive layer can bond the electrode to the composite separator, improving the solid-solid interface contact performance between the composite separator and the electrode, enhancing the ion transport performance between the composite separator and the electrode, and thereby improving the rate performance, energy density, and cycle performance of the secondary battery.

[0038] In any embodiment, the first non-liquid electrolyte layer is disposed on the porous base membrane, and the ceramic layer is disposed on the surface of the first non-liquid electrolyte layer opposite to the porous membrane.

[0039] In any embodiment, the ceramic layer includes ceramic particles and a binder.

[0040] In any embodiment, the ceramic particles comprise one or more of boehmite, alumina, silicon dioxide, magnesium oxide, zinc oxide, titanium oxide, cesium dioxide, and magnesium hydroxide.

[0041] In any embodiment, the adhesive comprises one or more of polyvinyl alcohol, polyacrylate, polyurethane, modified cellulose, polyvinylidene fluoride and its copolymers, polymethyl methacrylate, polyacrylamide, lithium polyacrylate, styrene-butadiene rubber, and acrylic / acrylate / acrylic block copolymers.

[0042] In any embodiment, the porous base membrane includes one or more of the following: polyolefin membrane, woven membrane, nonwoven membrane, rolled membrane, alumina ceramic membrane, polyvinylidene fluoride and its copolymer membrane, composite nanofiber membrane, polyethylene oxide-lithium salt composite lithium-ion conductive membrane, and polymethyl methacrylate composite membrane.

[0043] In any embodiment, the ceramic layer in the composite separator is disposed on the side of the porous base membrane facing the positive electrode. This enhances the strength of the base membrane, suppresses thermal shrinkage and dendrite growth, and simultaneously inhibits oxidation reactions between the solid electrolyte and the high-voltage positive electrode, thereby improving the cycle performance of the secondary battery.

[0044] In any embodiment, the positive electrode sheet contains a positive electrode active material, which includes a lithium-containing transition metal oxide, wherein the molar content of nickel in the lithium-containing transition metal oxide accounts for more than 55% of the total molar content of nickel, cobalt and manganese.

[0045] In any embodiment, the positive electrode sheet contains a positive electrode active material, which includes a lithium-containing transition metal oxide, wherein the molar content of nickel in the lithium-containing transition metal oxide accounts for more than 80% of the total molar content of nickel, cobalt and manganese.

[0046] The second aspect of this application provides a method for preparing a secondary battery, comprising the following steps:

[0047] A second non-liquid electrolyte is filled into the pores of the porous base membrane;

[0048] A ceramic layer and a first non-liquid electrolyte layer are disposed on the surface of a porous base membrane with a thickness T1≤4μm, wherein the first non-liquid electrolyte layer is disposed on at least one side surface of the porous base membrane, thereby forming a composite separator; and

[0049] The positive electrode, the composite separator, and the negative electrode are stacked in sequence.

[0050] A composite separator is formed by stacking a porous base membrane with a thickness T1≤4μm, a ceramic layer, and a first non-liquid electrolyte layer, and filling the pores of the porous base membrane with a second non-liquid electrolyte; the secondary battery prepared by this method has high energy density, good rate performance, and good cycle performance.

[0051] In any embodiment, during the step of sequentially stacking the positive electrode, the composite separator, and the negative electrode, the ceramic layer in the composite separator is positioned on the side of the porous base film facing the positive electrode. Thus, this ceramic layer enhances the strength of the base film, suppresses thermal shrinkage and dendrite growth, and inhibits oxidation reactions between the solid electrolyte and the high-voltage positive electrode, thereby improving the cycle performance of the secondary battery.

[0052] In any embodiment, filling the pores of the porous base membrane with a second non-liquid electrolyte includes the following steps:

[0053] Provide the porous base membrane;

[0054] The second non-liquid electrolyte slurry is prepared by using the powder of the second non-liquid electrolyte;

[0055] The second non-liquid electrolyte slurry is coated on the surface of the porous base membrane and allowed to penetrate into the pores inside the porous base membrane, then dried.

[0056] In any embodiment, filling the pores of the porous base membrane with a second non-liquid electrolyte includes the following steps:

[0057] Provide the porous base membrane;

[0058] The monomer of the second non-liquid electrolyte is dissolved in a solvent to obtain a reaction solution;

[0059] The porous base membrane is placed in the reaction solution and fully immersed;

[0060] An in-situ polymerization reaction is carried out after an initiator is added to the reaction solution;

[0061] The porous membrane obtained after the reaction is filtered, washed, and dried.

[0062] In any embodiment, a ceramic layer and a first non-liquid electrolyte layer are disposed on the surface of a porous base membrane, including the following steps:

[0063] The ceramic layer is disposed on the surface of the porous base membrane; and

[0064] The first non-liquid electrolyte layer is disposed on the surface of the ceramic layer opposite to the porous base membrane.

[0065] In any embodiment, the composite separator further includes an adhesive layer located on at least one surface of the composite separator; in the step of sequentially stacking the positive electrode, the composite separator, and the negative electrode, the composite separator is bonded and fixed to the positive electrode and / or the negative electrode through the adhesive layer. This improves the solid-solid interface contact performance between the composite separator and the positive electrode and / or the negative electrode, enhances the ion transport performance between the composite separator and the electrode, and thus improves the rate performance, energy density, and cycle performance of the secondary battery.

[0066] In any embodiment, a ceramic layer and a first non-liquid electrolyte layer are disposed on the surface of a porous base membrane, including the following steps:

[0067] The first non-liquid electrolyte layer is disposed on the surface of the porous base membrane; and

[0068] A ceramic layer is disposed on the surface of the first non-liquid electrolyte layer away from the porous base membrane, the ceramic layer comprising ceramic particles and a binder.

[0069] A third aspect of this application provides an electrical device, including a secondary battery according to the first aspect of this application, or a secondary battery prepared by the method of preparing a secondary battery according to the second aspect of this application.

[0070] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0071] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0072] Figure 1 This is a schematic diagram of the structure of a secondary battery according to one embodiment of this application;

[0073] Figure 2 This is a schematic diagram of the structure of a secondary battery according to another embodiment of this application;

[0074] Figure 3 This is a schematic diagram of the structure of the composite separator in a secondary battery according to an embodiment of this application;

[0075] Figure 4 This is a schematic diagram of the structure of the composite separator in a secondary battery according to another embodiment of this application;

[0076] Figure 5 This is a schematic diagram of a battery cell according to one embodiment of this application;

[0077] Figure 6 for Figure 5 An exploded view of a battery cell according to one embodiment of this application is shown.

[0078] Figure 7 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0079] Explanation of reference numerals in the attached figures:

[0080] 10. Secondary battery; 11. Positive electrode; 12. Composite separator; 121. Porous base membrane; 122. Ceramic layer; 123. First non-liquid electrolyte layer; 124. Adhesive layer; 13. Negative electrode; 5. Battery cell; 51. Casing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device. Detailed Implementation

[0081] The following describes in detail, with appropriate reference to the accompanying drawings, the secondary battery of this application, its preparation method, and embodiments of the power-using device. However, some unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0082] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints. Any endpoint can be independently included or excluded, and they can be combined arbitrarily; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0083] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0084] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0085] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0086] Those skilled in the art will understand that the order in which the steps are written in the methods of various embodiments or examples does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0087] In this application, open-ended technical features or solutions described using terms such as "containing," "including," or "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may also include other members or exclude additional members unless otherwise specified. This can be considered as providing both the feature or solution that "A consists of a1, a2, and a3" and the feature or solution that "A includes not only a1, a2, and a3, but also other members." In this application, unless otherwise specified, A (e.g., B) indicates that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0088] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0089] Currently, with the rapid development of solid-state battery technology, higher requirements are being placed on the performance of solid-state batteries. Seeking a solid-state battery with good charge / discharge rate performance and good cycle performance has become one of the important research directions in this field. To address this, this application improves the structure of the solid-state battery, effectively enhancing its rate performance and cycle performance.

[0090] Please see Figure 1 , Figure 2 , Figure 3 and Figure 4Some embodiments of this application provide a secondary battery 10, which includes a positive electrode 11, a composite separator 12, and a negative electrode 13 stacked sequentially; wherein, the composite separator 12 includes a porous base membrane 121, a ceramic layer 122, and a first non-liquid electrolyte layer 123 stacked sequentially; the thickness T1 of the porous base membrane 121 is ≤ 4 μm, and the pores of the porous base membrane 121 are filled with a second non-liquid electrolyte.

[0091] Traditional solid-state batteries typically use a solid electrolyte sheet between the positive and negative electrodes for ion conduction. Solid electrolyte sheets have high hardness, and due to gaps between the solid electrolyte powder particles, their thickness is relatively large, making it impossible to achieve a thickness of tens of micrometers. This results in poor applicability and affects the energy density of solid-state batteries. Furthermore, traditional solid electrolyte sheets lack internal structural support, leading to poor stress resistance. Especially during the breathing charge-discharge process within the battery, the solid electrolyte material is subjected to high voltage for extended periods, causing the internal chemical bonds to slowly break down, leading to structural collapse, powder fragmentation, severe damage to the battery interface, and significant performance degradation, thus affecting the battery's cycle performance.

[0092] The secondary battery 10 described in this application comprises a composite separator 12 formed by stacking a porous base membrane 121 with a thickness T1≤4μm, a ceramic layer 122, and a first non-liquid electrolyte layer 123, and filling the pores of the porous base membrane 121 with a second non-liquid electrolyte. The porous base membrane 121 provides support for the first non-liquid electrolyte layer 123, acting as a skeletal support and mitigating the degradation of battery cycle performance caused by the breakage and collapse of solid electrolyte powder during battery cycling. By filling the pores of the porous base membrane 121 with the second non-liquid electrolyte, which works in conjunction with the first non-liquid electrolyte layer 123 on the surface of the base membrane, the composite separator 12 exhibits high ionic conductivity and flexibility even at a very thin thickness, thereby improving the energy density and rate performance of the secondary battery 10. The aforementioned secondary battery 10 possesses high energy density, good rate performance, and good cycle performance.

[0093] In some embodiments, the puncture resistance of the porous base membrane is 0.7 N or higher. Optionally, it is 0.9 N or higher. More preferably, it is 1.0 N or higher. Using the aforementioned ultrathin base membrane with high mechanical strength improves the processability of the composite separator and ensures its structural stability during subsequent use, thus contributing to improved cycle performance of the secondary battery.

[0094] In some embodiments, the thickness T1 of the porous base membrane and the thickness T of the composite separator satisfy 0.02 ≤ T1 / T ≤ 0.33. It can be selected as 0.05~0.2 or higher. Controlling the thickness of the porous base membrane within the above range in this application helps to improve the overall mechanical strength of the composite separator, while also ensuring that the composite separator has high ion conduction capability, which is beneficial to ensuring that the battery has high energy density and good cycle performance.

[0095] In some embodiments, the positive electrode includes a positive current collector, and the ratio of the thickness of the composite separator to the thickness of the positive current collector is 0.5 to 4:1, optionally 1.0 to 3.2:1.

[0096] In some specific examples, the energy density of the secondary battery is ≥250Wh / kg; further, the energy density is ≥300Wh / kg. The amount of free electrolyte in the secondary battery is ≤0.1mg / Ah. By using an ultra-thin porous membrane composite separator, the overall thickness is also relatively thin. Without affecting cycle performance, the amount of free electrolyte in the secondary battery can be effectively reduced, which is beneficial to improving the battery's energy density.

[0097] In some embodiments, the porosity of the porous base membrane 121 is P1, the porosity of the composite membrane 12 is P2, and the P2 / P1 ratio is 0.05~0.9. After a first non-liquid electrolyte layer 123 is formed on the surface of the porous base membrane 121 and a second non-liquid electrolyte is filled into the pores of the porous base membrane 121, the porosity of the composite membrane 12 will decrease relative to the porosity of the porous base membrane 121.

[0098] The ratio P2 / P1, where the porosity of the composite separator 12 is equal to the porosity of the porous base membrane 121, reflects the amount of the first non-liquid electrolyte layer 123 and the second non-liquid electrolyte in the composite separator 12. Generally, a smaller P2 / P1 indicates a larger amount of the first non-liquid electrolyte layer 123 and the second non-liquid electrolyte on the porous base membrane 121; a larger P2 / P1 indicates a smaller amount of the first non-liquid electrolyte layer 123 and the second non-liquid electrolyte on the porous base membrane 121. By controlling the value of P2 / P1 within the above range, an appropriate amount of solid electrolyte can be present on the surface and within the pores of the porous base membrane 121. This allows the composite separator 12 to have excellent ionic conductivity while maintaining a relatively thin thickness, thereby enabling the secondary battery 10 to have high energy density and good rate performance.

[0099] It is understandable that the ratio P2 / P1 of the porosity of the composite membrane 12 to the porosity of the porous base membrane 121 can be 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, 0.32, 0.35, 0.38, 0.4, 0.42, 0.45, 0.48, 0.5, 0.52, 0.55, 0.58, 0.6, 0.62, 0.65, 0.68, 0.7, 0.72, 0.75, 0.78, 0.8, 0.82, 0.85, 0.88, 0.9, or any value within the range formed by any two of the above values.

[0100] Optionally, P2 / P1 is 0.3~0.6. More preferably, P2 / P1 is 0.1~0.5. By controlling the value of P2 / P1 within the above range, it is more advantageous to maintain the thinness of the composite separator 12 while enabling the composite separator 12 to have excellent ionic conductivity, thereby enabling the secondary battery 10 to have higher energy density and better rate performance.

[0101] In some embodiments, the porosity P1 of the porous base membrane 121 is 20% to 70%. Controlling the porosity of the porous base membrane 121 within this range allows lithium ions to pass smoothly through the porous base membrane 121 during battery charging and discharging, resulting in higher ionic conductivity of the composite separator 12 and better rate performance of the secondary battery 10. It is understood that the porosity P1 of the porous base membrane 121 can be 20%, 25%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, or any value within the range formed by any two of the above values.

[0102] In some embodiments, the porosity P2 of the composite membrane 12 is 5% to 50%; optionally, it is 30% to 50%. It is understood that the porosity P2 of the composite membrane 12 can be 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, or any value within the range formed by any two of the above values.

[0103] In some embodiments, the porous base membrane 121 has a thickness of 1 μm to 3.5 μm, the first non-liquid electrolyte layer 123 has a thickness of 5 μm to 20 μm, and the composite separator 12 has a thickness of 10 μm to 50 μm. In the secondary battery 10 of this application, the porous base membrane 121 in the composite separator 12 is very thin, and the overall thickness of the composite separator 12 is also very thin, which can improve the ion transport performance of the composite separator 12 and enhance the rate performance and energy density of the secondary battery 10.

[0104] It is understood that the thickness of the porous base film 121 can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, or any value within the range formed by any two of the above values. The thickness of the first non-liquid electrolyte layer 123 can be 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, or any value within the range formed by any two of the above values. The thickness of the composite diaphragm 12 can be 10μm, 12μm, 15μm, 18μm, 20μm, 22μm, 25μm, 28μm, 30μm, 32μm, 35μm, 38μm, 40μm, 42μm, 45μm, 48μm, 50μm, or any value within the range formed by any two of the above values.

[0105] In some embodiments, the thickness of the porous base membrane 121 is 1.2 μm to 3 μm. By controlling the thickness of the porous base membrane 121 within the above range, the porous base membrane 121 has a relatively thin thickness. While providing effective skeletal support for the first non-liquid electrolyte layer 123, it is also more conducive to shortening the ion transport path, improving the ionic conductivity of the composite separator 12, and thus enhancing the rate performance and energy density of the secondary battery 10.

[0106] Alternatively, the thickness of the porous base film 121 is 1.5 μm to 3 μm. Further controlling the thickness of the porous base film 121 within the aforementioned range is more beneficial for improving the rate performance and energy density of the secondary battery 10.

[0107] In some embodiments, the pore size of the porous base membrane 121 is 50 nm to 300 nm. The pore size of the porous base membrane 121 also affects the ionic conductivity of the composite separator 12. By controlling the pore size of the porous base membrane 121 within the above range, the composite separator 12 can have a higher ionic conductivity, thereby improving the rate performance and energy density of the secondary battery 10. It is understood that the pore size of the porous base membrane 121 can be 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, or any value within the range formed by any two of the above values.

[0108] In some embodiments, the thickness of the composite separator 12 is 10 μm to 50 μm; optionally, it is 20 μm to 50 μm. Further controlling the thickness of the composite separator 12 within the above range allows for a thinner composite separator 12 while maintaining excellent ionic conductivity. This is beneficial for further improving the energy density and rate performance of the secondary battery 10.

[0109] In some embodiments, the materials of the first non-liquid electrolyte layer 123 and the second non-liquid electrolyte are each independently a gel electrolyte or a solid electrolyte. The materials of the first non-liquid electrolyte layer 123 and the second non-liquid electrolyte may be the same or different.

[0110] In some embodiments, the materials of the first non-liquid electrolyte layer 123 and the second non-liquid electrolyte include one or more of inorganic solid electrolytes and polymer solid electrolytes; the inorganic solid electrolyte includes one or more of sulfide solid electrolytes and oxide solid electrolytes.

[0111] Furthermore, sulfide solid electrolytes include Li2S-P2S5 and Li2S-P2S5-MS. x Li 10 GeP2S 12 Li 10 SiP2S 12 PEO / Li 10 GeP2S 12One or more of / SN; oxide solid electrolytes include one or more of lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium lanthanum zirconium titanium oxide, lithium titanium aluminum phosphate, lithium zinc germanate, lithium germanium aluminum phosphate, lithium boron oxide, lithium phosphate, lithium aluminum titanium phosphate, and lithium nitride; polymer solid electrolytes include polyethylene oxide (PEO) based solid electrolytes, polyacrylonitrile (PAN) based solid electrolytes, polymethyl methacrylate (PMMA) based solid electrolytes, polyvinylidene fluoride (PVDF) based solid electrolytes, polyethylene oxide-polyacrylonitrile (PEO-PAN) based solid electrolytes, polyethylene oxide-polymethyl methacrylate (PEO-PMMA) based solid electrolytes, and polyethylene oxide-polyvinylidene fluoride (PEO-PVDF) based solid electrolytes. One or more of the following: polymethyl methacrylate-polyvinylidene fluoride (PMMA-PVDF) based solid electrolyte, polymethyl methacrylate-polyacrylonitrile (PMMA-PAN) based solid electrolyte, polyacrylonitrile-polyvinylidene fluoride (PAN-PVDF) based solid electrolyte, polyethylene oxide-polyacrylonitrile-polymethyl methacrylate (PEO-PAN-PMMA) based solid electrolyte, polyethylene oxide-polyvinylidene fluoride-polymethyl methacrylate (PEO-PVDF-PMMA) based solid electrolyte, polyethylene oxide-polyacrylonitrile-polyvinylidene fluoride (PEO-PAN-PVDF) based solid electrolyte, and polyacrylonitrile-polymethyl methacrylate-polyvinylidene fluoride (PAN-PMMA-PVDF) based solid electrolyte.

[0112] In some embodiments, the second non-liquid electrolyte includes an inorganic solid electrolyte, which includes one or more of sulfide solid electrolytes and oxide solid electrolytes. Using the aforementioned inorganic solid electrolyte can effectively improve the transport performance of lithium ions / sodium ions within the base membrane, increase the ionic conductivity of the composite separator 12, and thereby enhance the rate performance and energy density of the secondary battery 10.

[0113] In some embodiments, the second non-liquid electrolyte comprises a polymer solid electrolyte. By filling the pores of the porous base membrane 121 with a polymer solid electrolyte, the good viscoelasticity and light weight of the polymer solid electrolyte allow the composite membrane 12 to maintain good flexibility, enabling it to better adapt to wound battery structures and thus improving its applicability.

[0114] In some embodiments, the second non-liquid electrolyte comprises a sulfide solid electrolyte, and the first non-liquid electrolyte layer 123 comprises an oxide solid electrolyte. The second non-liquid electrolyte filling the pores of the porous base membrane 121 is a sulfide solid electrolyte, which has high ionic conductivity; the first non-liquid electrolyte layer 123 disposed on the surface of the porous base membrane 121 is an oxide solid electrolyte, which has good stability. This arrangement is more conducive to improving the ionic conductivity of the composite separator 12 and enhancing the rate performance of the secondary battery 10, while also ensuring good stability of the secondary battery 10.

[0115] In some embodiments, the thickness of the ceramic layer 122 is 1 μm to 5 μm. The main function of providing the ceramic layer 122 in the composite membrane 12 is to enhance the strength of the composite membrane 12, suppress the thermal shrinkage of the porous base membrane 121, and at the same time suppress the growth of lithium dendrites / sodium dendrites, thereby alleviating the dendrite growth that could puncture the composite membrane 12.

[0116] It is understood that the ceramic layer 122 can be stacked and disposed at various locations on the composite membrane 12. For example, the ceramic layer 122 can be disposed between the porous base membrane 121 and the first non-liquid electrolyte layer 123, or disposed on the surface of the first non-liquid electrolyte layer 123 facing away from the porous base membrane 121. The ceramic layer 122 can be a single layer disposed on one side of the porous base membrane 121; or it can be two layers disposed on opposite sides of the porous base membrane 121. The thickness of the ceramic layer 122 can be 1μm, 1.2μm, 1.5μm, 1.8μm, 2μm, 2.2μm, 2.5μm, 2.8μm, 3μm, 3.2μm, 3.5μm, 3.8μm, 4μm, 4.2μm, 4.5μm, 4.8μm, 5μm, or any value within the range formed by any two of the above values.

[0117] In some embodiments, the ceramic layer 122 contains a non-liquid electrolyte, and / or the first non-liquid electrolyte layer 123 contains ceramic particles. That is, the ceramic layer 122 may be a mixed layer of ceramic particles and a non-liquid electrolyte; the first non-liquid electrolyte layer 123 may also be a mixed layer of ceramic particles and a non-liquid electrolyte; or the ceramic layer 122 and the first non-liquid electrolyte layer 123 may both be mixed layers of ceramic particles and a non-liquid electrolyte.

[0118] In some specific examples, the ceramic layer 122 contains a non-liquid electrolyte, and the first non-liquid electrolyte layer 123 contains ceramic particles. Thus, the ceramic layer 122 is a mixed layer of ceramic particles and a non-liquid electrolyte; simultaneously, the first non-liquid electrolyte layer 123 is also a mixed layer of ceramic particles and a non-liquid electrolyte. The mass ratio of ceramic particles to non-liquid electrolyte in the ceramic layer 122 and the first non-liquid electrolyte layer 123 can be the same or different. When the mass ratio is the same, the ceramic layer 122 and the first non-liquid electrolyte layer 123 can be prepared separately or in a single step. When the ceramic layer 122 and the first non-liquid electrolyte layer 123 are prepared in a single step, there is no clear boundary between them; they are essentially combined into one layer.

[0119] Please see Figure 2 In some embodiments, the ceramic layer 122 in the composite separator 12 is disposed on the side of the porous base membrane 121 facing the positive electrode 11. By disposing the ceramic layer 122 on the side facing the positive electrode 11, the strength of the base membrane is enhanced, thermal shrinkage and dendrite growth of the base membrane are suppressed, and oxidation reaction between the solid electrolyte and the high-voltage positive electrode 11 is suppressed, thereby improving the cycle performance of the secondary battery 10.

[0120] Please see Figure 3 and Figure 4 In some embodiments, the composite separator 12 further includes an adhesive layer 124 comprising an adhesive, and the adhesive layer 124 is located on the outermost side of the composite separator 12. By providing the adhesive layer 124 on the outermost side of the composite separator 12, when the composite separator 12 and the electrode are stacked, the electrode and the composite separator 12 can be bonded together through the adhesive layer 124, thereby improving the solid-solid interface contact performance between the composite separator 12 and the electrode, improving the ion transport performance between the composite separator 12 and the electrode, and thus improving the rate performance, energy density, and cycle performance of the secondary battery 10.

[0121] It is understood that the adhesive layer 124 can be disposed on the side of the composite separator 12 near the positive electrode 11 to bond the positive electrode 11 to the composite separator 12; similarly, the adhesive layer 124 can also be disposed on the side of the composite separator 12 near the negative electrode 13 to bond the negative electrode 13 to the composite separator 12; or adhesive layers 124 can be disposed on both sides of the composite separator 12 to bond the composite separator 12 to the positive electrode 11 and the negative electrode 13, respectively.

[0122] In some embodiments, a first non-liquid electrolyte layer 123 is disposed on a porous base membrane 121, and a ceramic layer 122 is disposed on the surface of the first non-liquid electrolyte layer 123 facing away from the porous base membrane 121. That is, the first non-liquid electrolyte layer 123 is disposed between the porous base membrane 121 and the ceramic layer 122, with the ceramic layer 122 located on the outermost side of the composite separator 12. Further, the ceramic layer 122 includes ceramic particles and a binder. The ceramic particles enhance the strength of the base membrane and inhibit thermal shrinkage and dendrite growth; the binder enables the ceramic layer 122 to also function as an adhesive layer 124, capable of bonding the composite separator 12 to the electrode.

[0123] In some embodiments, the ceramic particles include one or more of boehmite, alumina, silicon dioxide, magnesium oxide, zinc oxide, titanium oxide, cesium dioxide, and magnesium hydroxide. The binder includes one or more of polyvinyl alcohol, polyacrylate, polyurethane, modified cellulose, polyvinylidene fluoride and its copolymers, polymethyl methacrylate, polyacrylamide, lithium polyacrylate, styrene-butadiene rubber, and acrylic / acrylate / acrylic block copolymers.

[0124] In some embodiments, the porous base membrane 121 includes one or more of the following: polyolefin membrane, woven membrane, nonwoven membrane, rolled membrane, alumina ceramic membrane, polyvinylidene fluoride (PVDF) and its copolymer membrane, composite nanofiber membrane, polyethylene oxide (PEO)-lithium salt composite lithium-ion conductive membrane, and polymethyl methacrylate (PMMA) composite membrane. The polyolefin membrane includes one or more of polypropylene membrane and polyethylene membrane. The polyvinylidene fluoride copolymer membrane can be a polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer membrane.

[0125] In some embodiments, the positive electrode 11 contains a positive electrode active material, which includes a lithium-containing transition metal oxide. The molar content of nickel in the lithium-containing transition metal oxide accounts for more than 55% of the total molar content of nickel, cobalt, and manganese, i.e., a lithium-containing transition metal oxide with medium to high nickel content is used. Further, the molar content of nickel in the lithium-containing transition metal oxide accounts for more than 80% of the total molar content of nickel, cobalt, and manganese, i.e., a lithium-containing transition metal oxide with high nickel content (8 series or higher) is used. This is more conducive to improving the energy density of the secondary battery.

[0126] Some embodiments of this application provide a method for preparing the secondary battery 10 described above. The method includes the following steps: a ceramic layer 122 and a first non-liquid electrolyte layer 123 are disposed on the surface of a porous base film 121 with a thickness T1≤4μm. The first non-liquid electrolyte layer 123 is disposed on at least one side surface of the porous base film 121, and a second non-liquid electrolyte is filled into the pores of the porous base film 121 to form a composite separator 12; a positive electrode 11, the composite separator 12, and a negative electrode 13 are sequentially stacked.

[0127] The method for preparing the secondary battery 10 described above in this application involves stacking the aforementioned porous base membrane 121, ceramic layer 122, and first non-liquid electrolyte layer 123 to form a composite separator 12, and filling the pores of the porous base membrane 121 with a second non-liquid electrolyte; the secondary battery 10 prepared therefrom has high energy density, good rate performance, and good cycle performance.

[0128] In some embodiments, during the step of sequentially stacking the positive electrode 11, the composite separator 12, and the negative electrode 13, the ceramic layer 122 in the composite separator 12 is positioned on the side of the porous base film 121 facing the positive electrode 11. This arrangement allows the ceramic layer 122 to enhance the strength of the base film, suppress thermal shrinkage and dendrite growth, and simultaneously inhibit the oxidation reaction between the solid electrolyte and the high-voltage positive electrode 11, thereby improving the cycle performance of the secondary battery 10.

[0129] In some embodiments, the pores of the porous base membrane 121 are filled with a second non-liquid electrolyte by the following method: providing the porous base membrane 121; preparing a second non-liquid electrolyte slurry from powder of the second non-liquid electrolyte; coating the second non-liquid electrolyte slurry onto the surface of the porous base membrane 121 and allowing it to penetrate into the pores inside the porous base membrane 121; and drying it, thereby filling the pores of the porous base membrane 121 with the second non-liquid electrolyte.

[0130] In other embodiments, the pores of the porous base membrane 121 are filled with a second non-liquid electrolyte by the following method: providing a porous base membrane 121; dissolving the monomer of the second non-liquid electrolyte in a solvent to obtain a reaction solution; placing the porous base membrane 121 in the reaction solution and fully wetting it; adding an initiator to the reaction solution and carrying out an in-situ polymerization reaction; and filtering, washing, and drying the porous base membrane 121 obtained after the reaction, thereby forming the second non-liquid electrolyte in situ within the pores of the porous base membrane 121.

[0131] In some embodiments, a ceramic layer 122 and a first non-liquid electrolyte layer 123 are formed on the surface of a porous base membrane 121 by the following method: first, a ceramic layer 122 is formed on the surface of the porous base membrane 121, and then a first non-liquid electrolyte layer 123 is formed on the surface of the ceramic layer 122 facing away from the porous base membrane 121; thereby forming a composite membrane structure in which the porous base membrane 121, the ceramic layer 122 and the first non-liquid electrolyte layer 123 are sequentially stacked.

[0132] In some embodiments, the composite separator 12 further includes an adhesive layer 124 located on at least one side surface of the composite separator 12. During the step of sequentially stacking the positive electrode 11, the composite separator 12, and the negative electrode 13, the adhesive layer 124 is used to bond and fix the composite separator 12 to the positive electrode 11 and / or the negative electrode 13. This improves the solid-solid interface contact performance between the composite separator 12 and the positive electrode 11 and / or the negative electrode 13, enhances the ion transport performance between the composite separator 12 and the electrode, and thereby improves the rate performance, energy density, and cycle performance of the secondary battery 10.

[0133] In some embodiments, a ceramic layer 122 and a first non-liquid electrolyte layer 123 are formed on the surface of the porous base membrane 121 by the following method: First, a first non-liquid electrolyte layer 123 is formed on the surface of the porous base membrane 121; then, a ceramic layer 122 is formed on the surface of the first non-liquid electrolyte layer 123 facing away from the porous base membrane 121, and the ceramic layer 122 includes ceramic particles and a binder. Thus, the ceramic layer 122 is disposed on the outermost side of the composite separator 12. The ceramic layer 122, containing ceramic particles and a binder, enhances the strength of the base membrane, inhibits thermal shrinkage and dendrite growth of the base membrane, and simultaneously bonds the composite separator 12 to the electrode, improving the solid-solid interface contact performance.

[0134] Some embodiments of this application provide an electrical device, including the secondary battery 10 described above, or a secondary battery 10 prepared by the method described above.

[0135] The secondary battery and power-consuming device of this application will be described below with appropriate reference to the accompanying drawings.

[0136] Unless otherwise specified, the battery components, material types or contents mentioned apply to both lithium-ion and sodium-ion batteries.

[0137] Typically, a secondary battery consists of a positive electrode, a negative electrode, and a solid electrolyte layer. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and extracting. The solid electrolyte acts as a conductor of ions between the positive and negative electrodes.

[0138] Positive electrode sheet

[0139] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector.

[0140] As a non-limiting example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0141] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be obtained by forming a metal material on a polymer material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymer material substrate in the positive electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0142] In some embodiments, the positive electrode active material may comprise a positive electrode active material known in the art for use in batteries.

[0143] As a non-limiting example, the positive electrode active material of a lithium-ion battery may include one or more of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials of batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and their modified compounds. Non-limiting examples of lithium phosphates with an olivine structure include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3Co 1 / 3 Mn 1 / 3O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811), etc.; non-limiting examples of lithium nickel cobalt aluminum oxides may include LiNi 0.85 Co 0.1 Al 0.05 O2.

[0144] In some embodiments, the positive electrode active material includes a lithium-containing transition metal oxide, wherein the molar content of nickel in the lithium-containing transition metal oxide accounts for more than 55% of the total molar content of nickel, cobalt, and manganese. Optionally, the molar content of nickel in the lithium-containing transition metal oxide accounts for more than 80% of the total molar content of nickel, cobalt, and manganese. In this application, the secondary battery further employs a positive electrode active material containing the above-mentioned substances, which is beneficial to further improve the energy density of the battery.

[0145] Understandably, lithium (Li) is intercalated and deintercalated during the charging and discharging process of a battery, and the Li content in the positive electrode varies depending on the state of discharge. Unless otherwise specified, the Li content in the examples of positive electrode materials listed in this application refers to the initial state of the material. When a positive electrode material is applied to a positive electrode in a battery system, the Li content in the positive electrode material typically changes after charge-discharge cycles. The Li content can be measured using molar content, but is not limited to this. Regarding "Li content refers to the initial state of the material," the initial state of the material refers to its state before being added to the positive electrode slurry. It is understood that new materials obtained by appropriately modifying the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for the positive electrode material; non-limiting examples include coating modification.

[0146] In the examples of cathode materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause changes in the molar content of oxygen, and the actual O content will fluctuate. The O content can be measured in molar content, but is not limited to this.

[0147] As a non-limiting example, the positive electrode active material of a sodium-ion battery may include one or more of the following materials: sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, this application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0148] As an optional technical solution in this application, the transition metal in the sodium transition metal oxide can be one or more selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. For example, the sodium transition metal oxide is Na. x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 <x≤1。

[0149] As an optional technical solution in this application, the polyanionic compound can be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds with anionic units. The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be one or more of P, S, and Si; n represents (YO4). n- The price state.

[0150] Polyanionic compounds can also contain sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds containing anionic units and halide anions. The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be one or more of P, S, and Si, and n represents (YO4). n- The valence state; halogens can be one or more of F, Cl and Br.

[0151] Polyanionic compounds can also be sodium-containing tetrahedral (YO4) compounds. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be one or more of P, S, and Si, and n represents (YO4). n- The valence state; Z represents a transition metal, which can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; m represents (ZO) y ) m+ The valence state; halogens can be one or more of F, Cl and Br.

[0152] Polyanionic compounds include, for example, NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F (where M' is one or more of V, Fe, Mn and Ni), and Na3(VO4) y )2(PO4)2F 3-2y One or more of (0≤y≤1).

[0153] Prussian blue compounds can contain sodium ions, transition metal ions, and cyanide ions (CN). - A class of compounds. Transition metals can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue compounds include, for example, Na. a Me b Me' c (CN)6, wherein Me and Me' are each independently one or more of Ni, Cu, Fe, Mn, Co, and Zn, 0 <a≤2,0<b<1,0<c<1。

[0154] The positive electrode active material accounts for 80% to 100% of the weight of the positive electrode film, based on the total weight of the positive electrode film.

[0155] In some embodiments, the positive electrode film layer may optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. The binder constitutes 0% to 20% by weight of the positive electrode film layer, based on the total weight of the positive electrode film layer.

[0156] In some embodiments, the positive electrode film may optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The conductive agent accounts for 0% to 20% by weight of the positive electrode film, based on the total weight of the positive electrode film.

[0157] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, coating the positive electrode slurry on the surface of the positive current collector, drying it and then cold pressing it through a cold rolling mill to form the positive electrode sheet.

[0158] Negative electrode sheet

[0159] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0160] As a non-limiting example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0161] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be obtained by forming a metal material on the polymer material substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymer material substrate in the negative electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0162] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries.

[0163] As a non-limiting example, the negative electrode active material of a lithium-ion battery may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0164] As a non-limiting example, the negative electrode active material of a sodium-ion battery is typically a hard carbon material, a two-dimensional metal carbide, or a nitride. Preferably, the negative electrode active material of a sodium-ion battery is typically a hard carbon material.

[0165] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0166] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0167] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0168] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (a non-limiting example of a solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto at least one surface of the negative electrode current collector, and then obtaining the negative electrode sheet after processes such as drying and cold pressing. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or both surfaces of the negative electrode current collector.

[0169] In some implementations, the positive electrode, negative electrode, and solid electrolyte layer can be fabricated into an electrode assembly using a winding or stacking process.

[0170] In some implementations, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and the electrolyte.

[0171] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch-type soft pack. The material of the soft pack can be plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0172] In some embodiments, the preparation method of the secondary battery includes the following steps: filling the pores of a porous base membrane with a second non-liquid electrolyte; and setting a ceramic layer and a first non-liquid electrolyte layer on the surface of the porous base membrane with a thickness T1≤4μm, wherein the first non-liquid electrolyte layer is disposed on at least one side surface of the porous base membrane, thereby forming a composite separator; and sequentially stacking a positive electrode, the composite separator, and a negative electrode.

[0173] In some embodiments, during the step of sequentially stacking the positive electrode, composite separator, and negative electrode, the ceramic layer in the composite separator is positioned on the side of the porous base membrane facing the positive electrode.

[0174] In some embodiments, filling the pores of a porous base membrane with a second non-liquid electrolyte includes the following steps: providing a porous base membrane; preparing a second non-liquid electrolyte slurry using powder of the second non-liquid electrolyte; coating the second non-liquid electrolyte slurry onto the surface of the porous base membrane and allowing it to penetrate into the pores inside the porous base membrane; and drying.

[0175] In some embodiments, filling the pores of a porous base membrane with a second non-liquid electrolyte includes the following steps: providing a porous base membrane; dissolving the monomer of the second non-liquid electrolyte in a solvent to obtain a reaction solution; placing the porous base membrane in the reaction solution and fully wetting it; adding an initiator to the reaction solution and carrying out an in-situ polymerization reaction; and filtering, washing, and drying the porous base membrane obtained after the reaction.

[0176] In some embodiments, a ceramic layer and a first non-liquid electrolyte layer are disposed on the surface of a porous base membrane, including the following steps: disposing of a ceramic layer on the surface of the porous base membrane; and disposing of a first non-liquid electrolyte layer on the surface of the ceramic layer opposite to the porous base membrane.

[0177] In some embodiments, the composite separator further includes an adhesive layer located on at least one side surface of the composite separator; in the step of sequentially stacking the positive electrode, the composite separator, and the negative electrode, the composite separator is bonded and fixed to the positive electrode and / or the negative electrode by the adhesive layer.

[0178] In some embodiments, the process of forming a ceramic layer and a first non-liquid electrolyte layer on the surface of a porous base membrane includes the following steps: forming a first non-liquid electrolyte layer on the surface of the porous base membrane; and forming a ceramic layer on the surface of the first non-liquid electrolyte layer opposite to the porous base membrane, wherein the ceramic layer comprises ceramic particles and a binder.

[0179] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0180] In this application, unless otherwise specified, "cell battery" refers to the basic unit capable of converting chemical energy into electrical energy, and generally includes at least a positive electrode, a negative electrode, and an electrolyte. During the charging and discharging process of the battery, active ions move back and forth between the positive and negative electrode plates, inserting and extracting. The electrolyte acts as a conductor for the active ions between the positive and negative electrode plates.

[0181] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 5 The example shown is a square-structured battery cell 5.

[0182] In some implementations, refer to Figure 6The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator can be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0183] In some embodiments, the battery cells 5 can be assembled into a battery module, and the number of battery cells 5 contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0184] In the battery module, multiple battery cells 5 can be arranged sequentially along the length of the battery module. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be secured with fasteners.

[0185] Optionally, the battery module may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0186] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0187] The battery pack may include a battery box and multiple battery modules disposed within the battery box. The battery box includes an upper body and a lower body, with the upper body covering the lower body to form a closed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0188] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0189] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0190] Figure 7 Here is an example of an electrical device 6. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0191] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0192] The following are some examples.

[0193] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. 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.

[0194] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0195] 1. Preparation method of composite membrane

[0196] The preparation method of diaphragm 1 is as follows:

[0197] (1) Provide a porous base membrane: Provide a PE base membrane with a porosity P1 of 52%, a pore size of 60 nm, a thickness of 4 μm, and a puncture resistance of 0.9 N;

[0198] (2) Filling a porous base film with a second non-liquid electrolyte: Disperse solid electrolyte lithium lanthanum zirconium oxide powder with a particle size of 30 nm in NMP solvent to prepare lithium lanthanum zirconium oxide slurry; apply the above lithium lanthanum zirconium oxide slurry to the upper and lower surfaces of the PE base film by scraping and let it penetrate into the pores inside the base film, and dry it at 110°C to obtain a base film filled with solid electrolyte particles of lithium lanthanum zirconium oxide.

[0199] (3) Coating ceramic layer: Al2O3 powder and carboxymethyl cellulose binder are dispersed in water at a ratio of 99:1 and stirred thoroughly to obtain inorganic ceramic slurry. Then, the inorganic ceramic slurry is coated on the upper and lower surfaces of the base film filled with lithium lanthanum zirconium oxide solid electrolyte particles and dried. The thickness of the ceramic layer on one side is 3 μm.

[0200] (4) Coating the first non-liquid electrolyte layer: Solid electrolyte aluminum titanium lithium phosphate powder with a particle size of 300 nm and sodium carboxymethyl cellulose are dispersed in N-methylpyrrolidone solvent at a weight ratio of 90:10 and stirred thoroughly to prepare aluminum titanium lithium phosphate slurry; The above aluminum titanium lithium phosphate slurry is coated on the upper and lower surfaces of the base film obtained in step (3) by scraping and drying, wherein the thickness of the first non-liquid electrolyte layer is 10 μm;

[0201] (5) Applying the adhesive layer: Mix PVDF particles and styrene-butadiene rubber in water at a ratio of 4:1 and stir thoroughly to obtain an adhesive layer slurry; spray the above adhesive layer slurry onto the upper and lower surfaces of the diaphragm obtained in step (4), wherein the thickness of the adhesive layer is 0.5 μm, to obtain diaphragm 1.

[0202] The preparation methods of diaphragms 2 to 12 are similar to those of diaphragm 1. For specific base membrane and coating parameters, please refer to Table 1 and Table 2.

[0203] The preparation method of the diaphragm 13 is as follows: In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), solid electrolyte aluminum titanium lithium phosphate powder with a particle size of 300nm and sodium carboxymethyl cellulose are dispersed in N-methylpyrrolidone solvent at a weight ratio of 98:2. The mixture is stirred thoroughly to prepare an aluminum titanium lithium phosphate slurry. After the slurry is fully dissolved, the solid electrolyte membrane with a thickness of 50μm is prepared by conventional solution casting technology and drying.

[0204] The preparation method of diaphragm 14 is as follows:

[0205] (1) Provide a porous base membrane: Provide a PE base membrane with a porosity P1 of 52%, a pore size of 60 nm, a thickness of 4 μm, and a puncture resistance of 0.9 N;

[0206] (2) Filling a porous base film with a second non-liquid electrolyte: Disperse solid electrolyte lithium lanthanum zirconium oxide powder with a particle size of 30 nm in NMP solvent to prepare lithium lanthanum zirconium oxide slurry; apply the above lithium lanthanum zirconium oxide slurry to the upper and lower surfaces of the PE base film by scraping and let it penetrate into the pores inside the base film, and dry it at 110°C to obtain a base film filled with solid electrolyte particles of lithium lanthanum zirconium oxide.

[0207] (3) Coating ceramic layer: Al2O3 powder, solid electrolyte aluminum titanium phosphate lithium powder and carboxymethyl cellulose binder are dispersed in water at a ratio of 49.5:49.5:1 and stirred thoroughly to obtain a mixed slurry of inorganic ceramic and solid electrolyte. The mixed slurry is then coated on the upper and lower surfaces of the base film filled with lithium lanthanum zirconium oxide solid electrolyte particles and dried. The thickness of the ceramic layer on one side is 3 μm.

[0208] (4) Coating the first non-liquid electrolyte layer: Solid electrolyte lithium aluminum titanium phosphate powder, Al2O3 powder and sodium carboxymethyl cellulose are dispersed in N-methylpyrrolidone solvent at a weight ratio of 49.5:49.5:1 and stirred thoroughly to prepare a mixed slurry of solid electrolyte and inorganic ceramic; the above mixed slurry is coated on the upper and lower surfaces of the base film obtained in step (3) by scraping and drying, wherein the thickness of the first non-liquid electrolyte layer is 10 μm;

[0209] (5) Applying the adhesive layer: Mix PVDF particles and styrene-butadiene rubber in water at a ratio of 4:1 and stir thoroughly to obtain an adhesive layer slurry; spray the above adhesive layer slurry onto the upper and lower surfaces of the diaphragm obtained in step (4), wherein the thickness of the adhesive layer is 0.5 μm, to obtain diaphragm 14.

[0210] Table 1

[0211]

[0212] Table 2

[0213]

[0214] Example 1:

[0215] (1) Preparation of positive electrode sheet

[0216] LiNi 0.83 Co 0.10 Mn 0.07 O2, conductive agent superconducting carbon (Super-P), and binder polyvinylidene fluoride (PVDF) are mixed evenly at a mass ratio of 97:1.5:1.5 to prepare a positive electrode active slurry with a certain viscosity. The positive electrode active slurry is coated on both sides of the positive electrode current collector with a thickness of 12μm, dried at 85℃, and then cold-pressed. Then, the edges are cut, sliced, and slit. After slitting, the slits are dried at 110℃ for 4 hours under vacuum to produce the positive electrode sheet.

[0217] (2) Preparation of composite membrane

[0218] The diaphragm 1 prepared by the above method.

[0219] (3) Preparation of negative electrode sheet

[0220] Artificial graphite (anode active material), silicon-carbon composite material, acetylene black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (batch ratio) were mixed evenly in an appropriate amount of deionized water to obtain a cathode slurry. The cathode slurry was coated on both surfaces of the cathode current collector copper foil, and after drying, cold pressing, and slitting, a cathode electrode sheet was obtained.

[0221] (4) Electrolyte

[0222] Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a mass ratio of 20:80 to obtain an organic solvent. Thoroughly dried LiPF6 was dissolved in the organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Then, fluoroethylene carbonate (FEC) and 1,3-propanesulfonic acid lactone (PS) were added. The mass content of FEC was 3 wt% of the total mass of the electrolyte, and the mass content of PS was 0.5 wt% of the total mass of the electrolyte.

[0223] (5) Battery assembly

[0224] The positive electrode, separator, and negative electrode are stacked and wound in sequence to obtain the electrode assembly. The electrode assembly is placed in an outer aluminum shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, the battery is obtained.

[0225] In the fabricated battery, the composite separator has the following layer structure: adhesive layer + first non-liquid electrolyte layer + ceramic layer + porous base membrane (filled with second non-liquid electrolyte) + ceramic layer + first non-liquid electrolyte layer + adhesive layer. The porous base membrane has a thickness of 4 μm and is filled with the second non-liquid electrolyte, lithium lanthanum zirconium oxide. The ceramic layer has a thickness of 3 μm, the first non-liquid electrolyte layer has a thickness of 10 μm, and the adhesive layer has a thickness of 0.5 μm. The total thickness of the composite separator is 31 μm, and the porosity P2 is 25%.

[0226] Examples 2 to 17:

[0227] Examples 2 through 17 are basically the same as Example 1, as detailed in Tables 3 and 4. In Example 9, the positive electrode active material is LiNi. 0.65 Co 0.12 Mn 0.23 O2; The positive electrode active material in Example 10 is LiNi 0.55 Co 0.09 Mn 0.36 O2.

[0228] Comparative Examples 1 to 3:

[0229] Comparative Examples 1 to 3 are basically the same as Example 1, as detailed in Table 4.

[0230] Test method:

[0231] (1) Thickness test of base film and each coating

[0232] The thickness of the base film and each coating can be characterized by scanning electron microscopy (SEM) of the membrane cross-section. To ensure the accuracy of coating thickness measurement, at least 10 different coating locations can be selected for measurement, and the average value is taken as the thickness of the coating, in μm.

[0233] (2) Porosity testing of base membrane and composite membrane

[0234] Porosity is a well-known concept in the art and can be tested using instruments and methods known in the art. For example, refer to pages 2-3 of the national standard GB / T 24586-2009 "Determination of Apparent Density, True Density and Porosity of Iron Ore".

[0235] This embodiment is based on the national standard GB / T 24586-2009. The specific test steps are as follows: Using the inert gas (helium) replacement method with small molecule diameter, combined with Archimedes' principle and Bohr's law, the true volume of the material under test is accurately measured, which is the true volume of the sample, thereby obtaining the porosity of the sample to be tested.

[0236] Porosity ;

[0237] In the formula: V1 is the true volume of the sample, in cm³. 3 V2 is the apparent volume of the sample, in cm³. 3 Apparent volume V² = S × H × A, where S is the area in cm². 2 H represents thickness in cm; A represents the number of samples.

[0238] (3) Base membrane pore size test

[0239] The pore size of the base membrane can be measured directly using equipment such as a capillary flow porosimeter or mercury porosimeter from PMI. The specific testing steps are as follows: ① Completely wet and fill the pores of the base membrane to be tested with liquid, creating positive pressure inside the pores due to capillary action; ② Place the base membrane in a sealed tank and apply gas pressure to force the liquid out of the capillary channels; ③ Based on the relative relationship between the pressure applied when the liquid is completely squeezed out of the capillary channels and the channel diameter, the average pore size of the base membrane can be obtained according to the Laplace equation.

[0240] (4) Test method for puncture resistance of base membrane and composite diaphragm

[0241] A needle with a spherical tip (radius of curvature R: 0.5 mm) and a diameter of 1 mm is used to puncture a test sample with a film thickness T1 (μm), such as a base film or a composite diaphragm, at a speed of 2 mm / s. The maximum load at this point is measured in N, which is its puncture resistance strength.

[0242] (5) Battery cell mass energy density test

[0243] The battery cells were left to stand at 25°C for 2 hours to ensure the temperature remained at 25°C. At 25°C, the battery cells were charged at 0.1C to the charging cutoff voltage of 4.25V, and then continued to be charged at this voltage under constant voltage until the current reached 0.05C, at which point charging was stopped (where C represents the rated capacity of the battery cell). The battery cells were then left to stand at 25°C for 1 hour. At 25°C, the battery cells were discharged at 0.1C to the discharge cutoff voltage of 2.0V. The total discharge capacity C0 and total discharge energy E0 were recorded (unit: Wh).

[0244] The battery cells are weighed, and the mass is recorded as M0, with the unit being kg;

[0245] Battery cell mass energy density = E0 / M0, unit: Wh / kg.

[0246] (6) Battery cycle performance test

[0247] At 25℃, the battery cells were charged and discharged in the range of 2.0V~4.25V corresponding to 0%SOC~100%SOC. The voltage values ​​corresponding to 5%SOC and 95%SOC were calibrated, and cyclic tests were performed within this range until the capacity retention rate of the battery cells decayed to 85%SOH. The number of cycles was recorded.

[0248] The battery performance data for the above embodiments and comparative examples are shown in Tables 3 and 4.

[0249] Table 3

[0250]

[0251] Table 4

[0252]

[0253] As can be seen from the data in Tables 3 and 4 above, the batteries of the various embodiments of this application have high energy density and good cycle performance.

[0254] The description of the various embodiments above tends to emphasize the differences between the various embodiments. The similarities or similarities between them can be referred to, and for the sake of brevity, they will not be repeated here.

[0255] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A secondary battery, comprising: A positive electrode, a composite separator, and a negative electrode are stacked in sequence. The composite membrane comprises a porous base membrane, a ceramic layer, and a first non-liquid electrolyte layer stacked together; the thickness T1 of the porous base membrane is ≤4μm, and the pores of the porous base membrane are filled with a second non-liquid electrolyte.

2. The secondary battery according to claim 1, wherein, The composite diaphragm must satisfy at least one of the following conditions: (1) The puncture resistance of the porous base membrane is above 0.7N; (2) The thickness T1 of the porous base membrane and the thickness T of the composite separator satisfy 0.02≤T1 / T≤0.33; (3) The positive electrode includes a positive current collector, and the ratio of the thickness of the composite separator to the thickness of the positive current collector is 0.5~4:1, which can be selected as 1.0~3.2:

1.

3. The secondary battery according to claim 1, wherein, The energy density of the secondary battery is ≥250Wh / kg, and the amount of free electrolyte in the secondary battery is ≤0.1mg / Ah.

4. The secondary battery according to any one of claims 1 to 3, wherein, The porosity of the porous base membrane is P1, the porosity of the composite membrane is P2, and the ratio of P2 to P1 is 0.05 to 0.

9.

5. The secondary battery according to claim 4, wherein, The ratio of P2 to P1 is 0.1 to 0.

5.

6. The secondary battery according to claim 4, wherein, The porosity P1 of the porous base membrane is 20%~70%.

7. The secondary battery according to claim 4, wherein, The porosity P2 of the composite membrane is 5%~50%.

8. The secondary battery according to any one of claims 1 to 3, 5 to 7, wherein, The thickness of the porous base film is 1 μm to 3.5 μm.

9. The secondary battery according to claim 8, wherein, The thickness of the porous base film is 1 μm to 3.5 μm.

10. The secondary battery according to claim 9, wherein, The thickness of the porous base film is 1.5μm to 3μm.

11. The secondary battery according to any one of claims 1-3, 5-7, 9-10, wherein, The porous base membrane has a pore size of 50 nm to 300 nm.

12. The secondary battery according to any one of claims 1-3, 5-7, and 9-10, wherein, The thickness of the first non-liquid electrolyte layer is 5μm~20μm.

13. The secondary battery according to any one of claims 1-3, 5-7, 9-10, wherein, The thickness of the composite diaphragm is 10μm~50μm.

14. The secondary battery according to claim 13, wherein, The thickness of the composite diaphragm is 20μm~50μm.

15. The secondary battery according to any one of claims 1-3, 5-7, 9-10, and 14, wherein, The materials of the first non-liquid electrolyte layer and the second non-liquid electrolyte are each independently either gel electrolytes or solid electrolytes.

16. The secondary battery according to any one of claims 1-3, 5-7, 9-10, and 14, wherein, The first non-liquid electrolyte layer and the second non-liquid electrolyte may be made of the same or different materials.

17. The secondary battery according to any one of claims 1-3, 5-7, 9-10, and 14, wherein, The materials of the first non-liquid electrolyte layer and the second non-liquid electrolyte include one or more of inorganic solid electrolytes and polymer solid electrolytes, wherein the inorganic solid electrolyte includes one or more of sulfide solid electrolytes and oxide solid electrolytes.

18. The secondary battery according to claim 17, wherein, The secondary battery must meet at least one of the following conditions: (1) The sulfide solid electrolyte includes Li2S-P2S5 and Li2S-P2S5-MS. x Li 10 GeP2S 12 Li 10 SiP2S 12 and PEO / Li 10 GeP2S 12 One or more of / SN; (2) The oxide solid electrolyte includes one or more of lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium lanthanum zirconium titanium oxide, lithium titanium aluminum phosphate, lithium zinc germanate, lithium germanium aluminum phosphate, lithium boron oxide, lithium phosphate, lithium aluminum titanium phosphate and lithium nitride; (3) The polymer solid electrolyte includes one or more of the following: PEO-based solid electrolyte, PAN-based solid electrolyte, PMMA-based solid electrolyte, PVDF-based solid electrolyte, PEO-PAN-based solid electrolyte, PEO-PMMA-based solid electrolyte, PEO-PVDF-based solid electrolyte, PMMA-PVDF-based solid electrolyte, PMMA-PAN-based solid electrolyte, PAN-PVDF-based solid electrolyte, PEO-PAN-PMMA-based solid electrolyte, PEO-PVDF-PMMA-based solid electrolyte, PEO-PAN-PVDF-based solid electrolyte, and PAN-PMMA-PVDF-based solid electrolyte.

19. The secondary battery according to any one of claims 1-3, 5-7, 9-10, 14, and 18, wherein, The first non-liquid electrolyte layer comprises an oxide solid electrolyte, and the second non-liquid electrolyte comprises a sulfide solid electrolyte.

20. The secondary battery according to any one of claims 1-3, 5-7, 9-10, 14, and 18, wherein, The thickness of the ceramic layer is 1μm to 5μm.

21. The secondary battery according to any one of claims 1-3, 5-7, 9-10, 14, and 18, wherein, The secondary battery satisfies at least one of the following: (1) The ceramic layer contains a non-liquid electrolyte; (2) The first non-liquid electrolyte layer contains ceramic particles.

22. The secondary battery according to any one of claims 1-3, 5-7, 9-10, 14, and 18, wherein, The ceramic layer contains a non-liquid electrolyte, and the first non-liquid electrolyte layer contains ceramic particles.

23. The secondary battery according to any one of claims 1-3, 5-7, 9-10, 14, and 18, wherein, The ceramic layer is disposed between the porous base membrane and the first non-liquid electrolyte layer.

24. The secondary battery according to claim 23, wherein, The composite membrane further includes an adhesive layer comprising an adhesive, and the adhesive layer is located on the outermost side of the composite membrane.

25. The secondary battery according to any one of claims 1-3, 5-7, 9-10, 14, 18, and 24, wherein, The first non-liquid electrolyte layer is disposed on the porous base membrane, and the ceramic layer is disposed on the surface of the first non-liquid electrolyte layer away from the porous membrane. The ceramic layer includes ceramic particles and a binder.

26. The secondary battery according to claim 25, wherein, The composite diaphragm must satisfy at least one of the following conditions: (1) The ceramic particles include one or more of boehmite, alumina, silicon dioxide, magnesium oxide, zinc oxide, titanium oxide, cesium dioxide and magnesium hydroxide; (2) The adhesive includes one or more of polyvinyl alcohol, polyacrylate, polyurethane, modified cellulose, polyvinylidene fluoride and its copolymers, polymethyl methacrylate, polyacrylamide, lithium polyacrylate, styrene-butadiene rubber and acrylic / acrylate / acrylic block copolymers.

27. The secondary battery according to any one of claims 1-3, 5-7, 9-10, 14, 18, 24, and 26, wherein, The porous base membrane includes one or more of the following: polyolefin membrane, woven membrane, nonwoven membrane, rolled membrane, alumina ceramic membrane, polyvinylidene fluoride and its copolymer membrane, composite nanofiber membrane, polyethylene oxide-lithium salt composite lithium-ion conductive membrane, and polymethyl methacrylate composite membrane.

28. The secondary battery according to any one of claims 1-3, 5-7, 9-10, 14, 18, 24, and 26, wherein, The ceramic layer in the composite separator is disposed on the side of the porous base membrane facing the positive electrode sheet.

29. The secondary battery according to any one of claims 1-3, 5-7, 9-10, 14, 18, 24, and 26, wherein, The positive electrode sheet contains a positive electrode active material, which includes a lithium-containing transition metal oxide. The molar content of nickel in the lithium-containing transition metal oxide accounts for more than 55% of the total molar content of nickel, cobalt and manganese.

30. The secondary battery according to any one of claims 1-3, 5-7, 9-10, 14, 18, 24, and 26, wherein, The positive electrode sheet contains a positive electrode active material, which includes a lithium-containing transition metal oxide. The molar content of nickel in the lithium-containing transition metal oxide accounts for more than 80% of the total molar content of nickel, cobalt and manganese.

31. A method for preparing a secondary battery, comprising the following steps: A second non-liquid electrolyte is filled into the pores of the porous base membrane; A ceramic layer and a first non-liquid electrolyte layer are disposed on the surface of a porous base membrane with a thickness T1≤4μm, wherein the first non-liquid electrolyte layer is disposed on at least one side surface of the porous base membrane, thereby forming a composite separator; and The positive electrode, the composite separator, and the negative electrode are stacked in sequence.

32. The method for preparing a secondary battery according to claim 31, wherein, In the step of sequentially stacking the positive electrode, the composite separator, and the negative electrode, the ceramic layer in the composite separator is positioned on the side of the porous base membrane facing the positive electrode.

33. The method for preparing a secondary battery according to claim 31, wherein, Filling the pores of the porous base membrane with a second non-liquid electrolyte includes the following steps: Provide the porous base membrane; The second non-liquid electrolyte slurry is prepared by using the powder of the second non-liquid electrolyte; The second non-liquid electrolyte slurry is coated on the surface of the porous base membrane and allowed to penetrate into the pores inside the porous base membrane, then dried.

34. The method for preparing a secondary battery according to claim 31, wherein, Filling the pores of the porous base membrane with a second non-liquid electrolyte includes the following steps: Provide the porous base membrane; The monomer of the second non-liquid electrolyte is dissolved in a solvent to obtain a reaction solution; The porous base membrane is placed in the reaction solution and fully immersed; An in-situ polymerization reaction is carried out after an initiator is added to the reaction solution; The porous membrane obtained after the reaction is filtered, washed, and dried.

35. The method for preparing a secondary battery according to any one of claims 31 to 34, wherein, The process of depositing a ceramic layer and a first non-liquid electrolyte layer on the surface of a porous base membrane includes the following steps: The ceramic layer is disposed on the surface of the porous base membrane; and The first non-liquid electrolyte layer is disposed on the surface of the ceramic layer opposite to the porous base membrane.

36. The method for preparing a secondary battery according to any one of claims 31 to 34, wherein, The composite separator further includes an adhesive layer located on at least one side surface of the composite separator; in the step of sequentially stacking the positive electrode, the composite separator, and the negative electrode, the composite separator is bonded and fixed to the positive electrode and / or the negative electrode through the adhesive layer.

37. The method for preparing a secondary battery according to any one of claims 31 to 34, wherein, The process of depositing a ceramic layer and a first non-liquid electrolyte layer on the surface of a porous base membrane includes the following steps: The first non-liquid electrolyte layer is disposed on the surface of the porous base membrane; and A ceramic layer is disposed on the surface of the first non-liquid electrolyte layer away from the porous base membrane, the ceramic layer comprising ceramic particles and a binder.

38. An electrical device comprising a secondary battery according to any one of claims 1 to 30, or a secondary battery prepared by the method comprising any one of claims 31 to 37.

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