Composite separator, and battery and electric device

Abstract

A composite separator, a battery, and an electric device. The composite separator comprises a first separator layer and a second separator layer that are stacked one on the other, the first separator layer having solid electrolyte particles dispersed therein, and the second separator layer having lithium-rich material particles dispersed therein.

Description

Composite diaphragm, battery and electrical equipment

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure claims priority to a Chinese patent application filed with the Patent Office of China on November 30, 2023, with application number 202323305098.5 and titled “A Composite Diaphragm, Battery, and Electrical Equipment,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application belongs to the field of battery technology, and specifically relates to a composite diaphragm, a battery, and electrical equipment. Background Art

[0004] Polymer separators are a common type of separator used in existing lithium-ion batteries; however, the polymer separator itself lacks heat resistance and is prone to softening or thermal shrinkage under high temperature conditions, leading to short circuits between the positive and negative electrodes. Some studies have improved separator performance by extruding inorganic particles into a blend with polymers, but in reality, the addition of inorganic particles has limited improvement in the heat resistance of polymer separators and will also cause a decrease in the tensile strength of the polymer separator. The addition of inorganic particles will cause the separator's conductivity for lithium ions to decrease, and will also affect the wettability of the electrolyte to the separator, thereby affecting the separator's ionic conductivity, increasing the battery's internal resistance, and leading to uneven deposition of lithium ions and black spots, which is not conducive to the battery's capacity at low temperatures. During the initial formation of the battery, some lithium salts will be consumed to form the SEI film, which reduces the lithium salt concentration in the electrolyte, resulting in irreversible capacity loss and a low initial efficiency of the battery.

[0005] Summary of the Invention

[0006] In order to solve the problem of electrochemical performance degradation caused by the presence of inorganic particles in existing polymer membranes, the present application provides a composite membrane, a battery, and an electrical device.

[0007] The technical solutions adopted by this application to solve the above technical problems are as follows:

[0008] On the one hand, the present application provides a composite diaphragm, comprising a first diaphragm layer and a second diaphragm layer stacked together, wherein the first diaphragm layer comprises solid electrolyte particles, and the second diaphragm layer comprises lithium-rich material particles.

[0009] In some embodiments, the particle size D50 of the solid electrolyte particles is 0.5 μm to 5 μm.

[0010] In some embodiments, the first separator layer further includes a first porous polymer matrix layer, and the solid electrolyte particles are dispersed in the first porous polymer matrix layer.

[0011] In some embodiments, the material of the first porous polymer matrix layer is selected from high-density polyethylene, ultra-high-density polyethylene, low-density polyethylene, high-density polypropylene, ultra-high-density polypropylene, polyimide, or polyvinylidene fluoride.

[0012] In some embodiments, the thickness of the first diaphragm layer is 1 μm to 20 μm, and / or the thickness of the second diaphragm layer is 1 μm to 20 μm.

[0013] In some embodiments, the particle size D50 of the lithium-rich material particles is 0.5 μm to 5 μm.

[0014] In some embodiments, the solid electrolyte particles are selected from Li 1.3 Al 0.3 Ti 1.7 (PO4)3、Li7La3Zr2O 12 、Li 0.34 La 0.56 TiO3 or Li 1.5 Al 0.5 Ge 1.5 (PO4)3, and / or the lithium-rich material particles are selected from Li5FeO4, Li2Ni5O4, Li2MnO3, LiCoO4, Li6MnO4 or LiReO6.

[0015] In some embodiments, the second separator layer further includes a second porous polymer matrix layer, and the lithium-rich material particles are dispersed in the second porous polymer matrix layer.

[0016] In some embodiments, the material of the second porous polymer matrix layer is selected from high-density polyethylene, ultra-high-density polyethylene, low-density polyethylene, high-density polypropylene, ultra-high-density polypropylene, polyimide, or polyvinylidene fluoride.

[0017] In some embodiments, the composite membrane has a thickness of 2 μm to 40 μm.

[0018] In some embodiments, the pore size of the composite membrane is 20 nm to 70 nm, and the porosity of the composite membrane is 20% to 70%.

[0019] On the other hand, the present application provides a battery comprising a positive electrode, a negative electrode, and the composite separator as described above, wherein the composite separator is located between the positive electrode and the negative electrode.

[0020] In some embodiments, the first separator layer of the composite separator faces the negative electrode, and the second separator layer of the composite separator faces the positive electrode.

[0021] On the other hand, the present application provides an electrical device comprising the battery as described above.

[0022] The composite diaphragm provided in the present application adopts a composite structure of a first diaphragm layer dispersed with solid electrolyte particles and a second diaphragm layer dispersed with lithium-rich material particles. Among them, the addition of solid electrolyte particles and lithium-rich material particles not only improves the high-temperature stability of the composite diaphragm, but also the lattice defects and voids inside the solid electrolyte particles can realize the transmission of lithium ions, thereby effectively improving the ion transmission capacity of the diaphragm, reducing the internal resistance of the battery, and improving the low-temperature performance of the battery. In addition, the lithium-rich material particles can decompose and release lithium ions under high voltage conditions, thereby replenishing lithium to the battery in the formation stage. On the premise of improving the high-temperature resistance of the composite diaphragm, the electrochemical performance of the composite diaphragm and the first effect of the battery are effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1 is a schematic structural diagram of the composite diaphragm provided in this application.

[0024] The reference numerals in the drawings of the specification are as follows: 1. first separator layer; 11. solid electrolyte particles; 12. first porous polymer matrix layer; 2. second separator layer; 22. lithium-rich material particles; 21. second porous polymer matrix layer. DETAILED DESCRIPTION

[0025] In order to make the technical problems, technical solutions and beneficial effects solved by this application more clearly understood, this application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0026] As shown in FIG1 , an embodiment of the present application provides a composite diaphragm, comprising a stacked first diaphragm layer 1 and a second diaphragm layer 2 , wherein the first diaphragm layer 1 comprises solid electrolyte particles 11 , and the second diaphragm layer 2 comprises lithium-rich material particles 22 .

[0027] The addition of solid electrolyte particles 11 and lithium-rich material particles 22 not only improves the high-temperature stability of the composite diaphragm, but also the lattice defects and voids inside the solid electrolyte particles 11 can realize the transmission of lithium ions, thereby effectively improving the ion transmission capacity of the diaphragm, reducing the internal resistance of the battery, and improving the low-temperature performance of the battery. The lithium-rich material particles 22 can decompose and release lithium ions under high voltage conditions, thereby replenishing lithium for the battery in the formation stage. On the premise of improving the high-temperature resistance of the composite diaphragm, the electrochemical properties of the composite diaphragm and the initial efficiency of the battery are effectively improved.

[0028] In some embodiments, the particle size D50 of the solid electrolyte particles 11 is 0.5 μm to 5 μm.

[0029] In different embodiments, the particle size D50 of the solid electrolyte particles 11 can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, or 5 μm. The particle size D50 of the solid electrolyte particles 11 refers to the median particle size of the solid electrolyte particles, also known as the volume average particle size, which represents the particle size corresponding to the cumulative volume distribution percentage of the solid electrolyte particles reaching 50%. The particle size D50 of the solid electrolyte particles can be measured using a laser particle size analyzer.

[0030] The degree of dispersion of the solid electrolyte particles 11 in the first diaphragm layer 1 is related to the particle size of the solid electrolyte particles. When the particle size of the solid electrolyte particles 11 is within the above range, it has a larger particle size than conventional inorganic fillers, which can effectively avoid the agglomeration problem between particles caused by van der Waals force or electrostatic force, thereby improving the dispersion uniformity of the solid electrolyte particles 11 in the first diaphragm layer 1 and improving the consistency of the performance of each region of the first diaphragm layer 1.

[0031] In some embodiments, the first separator layer 1 further includes a first porous polymer matrix layer 12 , and the solid electrolyte particles 11 are dispersed in the first porous polymer matrix layer 12 .

[0032] The first porous polymer matrix layer 12 is the main matrix structure for maintaining the shape and toughness of the first diaphragm layer 1, and is also the main carrier for forming a porous structure. The porous structure is conducive to the penetration of the electrolyte, and the polymer material itself has affinity and wettability for the electrolyte, which can ensure the ion exchange of the electrolyte on both sides of the diaphragm.

[0033] In some embodiments, the material of the first porous polymer matrix layer 12 is selected from high-density polyethylene, ultra-high-density polyethylene, low-density polyethylene, high-density polypropylene, ultra-high-density polypropylene, polyimide or polyvinylidene fluoride. In some embodiments, low-density polyethylene may include but is not limited to linear low-density polyethylene.

[0034] In some embodiments, based on the total weight of the first separator layer 1 being 100%, the mass content of the first porous polymer matrix layer 12 is 50% to 90%, and the mass content of the solid electrolyte particles 11 is 10% to 50%.

[0035] In some embodiments, the thickness of the first diaphragm layer 1 is 1 μm to 20 μm.

[0036] In different embodiments, the thickness of the first diaphragm layer 1 may be 1 μm, 3 μm, 5 μm, 7 μm, 8 μm, 10 μm, 11 μm, 13 μm, 15 μm, 17 μm, 18 μm or 20 μm.

[0037] The first diaphragm layer 1 is used to improve the ionic conductivity of the composite diaphragm. When the thickness of the first diaphragm layer 1 is within the above range, the ionic permeability of the composite diaphragm can be effectively improved.

[0038] In some embodiments, the thickness of the second diaphragm layer 2 is 1 μm to 20 μm.

[0039] In different embodiments, the thickness of the second diaphragm layer 2 may be 1 μm, 3 μm, 5 μm, 7 μm, 8 μm, 10 μm, 11 μm, 13 μm, 15 μm, 17 μm, 18 μm or 20 μm.

[0040] The second separator layer 2 has the function of replenishing lithium for the composite separator. When the thickness of the second separator layer 2 is within the above range, it can provide a suitable amount of lithium replenishment while reducing the impact on the ionic conductivity of the separator.

[0041] In some embodiments, the particle size of the lithium-rich material particles 22 is 0.5 μm to 5 μm.

[0042] In various embodiments, the particle size of the lithium-rich material particles 22 may be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, or 5 μm. The particle size D50 of the lithium-rich material particles 22 refers to the median particle size, also known as the volume average particle size, of the lithium-rich material particles, representing the particle size at which the cumulative volume distribution percentage of the lithium-rich material particles reaches 50%. The particle size D50 of the lithium-rich material particles can be measured using a laser particle size analyzer.

[0043] The particle size of the lithium-rich material particles 22 is related to the degree of dispersion thereof in the second diaphragm layer 2. When the particle size of the lithium-rich material particles 22 is within the above range, it has a larger particle size than conventional inorganic fillers, which can effectively avoid the agglomeration problem between particles caused by van der Waals force or electrostatic force, improve the dispersion uniformity of the lithium-rich material particles 22 in the second diaphragm layer 2, and improve the consistency of the performance of each region of the second diaphragm layer 2.

[0044] In some embodiments, the solid electrolyte particles 11 are selected from Li 1.3 Al 0.3 Ti 1.7 (PO4)3、Li7La3Zr2O12 、Li 0.34 La 0.56 TiO3 and Li 1.5 Al 0.5 Ge 1.5 At least one of (PO4)3.

[0045] By selecting LATP(Li 1.3 Al 0.3 Ti 1.7 (PO4)3)、LLZO(Li7La3Zr2O 12 )、LLTO(Li 0.34 La 0.56 TiO3) or LAGP(Li 1.5 Al 0.5 Ge 1.5 When (PO4)3) is used as the solid electrolyte particles 11, it has the advantages of high lithium ion conductivity and thermal stability, which helps reduce the internal resistance of the battery and improve battery safety. The above solid electrolyte particles can be undoped or modified by doping, and their surfaces may or may not have a conductive coating. The material and thickness of the conductive coating can be selected as needed and are not further described in this disclosure.

[0046] In some embodiments, the lithium-rich material particles 22 are selected from at least one of Li5FeO4, Li2Ni5O4, Li2MnO3, LiCoO4, Li6MnO4 and LiReO6.

[0047] By selecting Li5FeO4, Li2Ni5O4, Li2MnO3, LiCoO4, Li6MnO4, or LiReO6 as the lithium-rich material particles 22, they have the advantages of high lithium content and decomposition and release of lithium ions under high voltage, which is conducive to improving the initial efficiency of battery formation. The above lithium-rich material particles can be undoped or modified by doping, and their surfaces can have a conductive coating or not. The material and thickness of the conductive coating can be selected as needed and will not be further described in this disclosure.

[0048] In some embodiments, the second separator layer 2 further includes a second porous polymer matrix layer 21 , and the lithium-rich material particles 22 are dispersed in the second porous polymer matrix layer 21 .

[0049] The second porous polymer matrix layer 21 is the main matrix structure for maintaining the shape and toughness of the second diaphragm layer 2, and is also the main structure for forming a porous structure, wherein the porous structure has the permeability of the electrolyte, and the polymer material itself has affinity and wettability for the electrolyte, which can ensure the ion exchange of the electrolyte on both sides of the diaphragm.

[0050] In some embodiments, the material of the second porous polymer matrix layer 21 is selected from high-density polyethylene, ultra-high-density polyethylene, low-density polyethylene, high-density polypropylene, ultra-high-density polypropylene, polyimide or polyvinylidene fluoride. In some embodiments, low-density polyethylene may include but is not limited to linear low-density polyethylene.

[0051] In some embodiments, based on 100% of the total weight of the second separator layer 2 , the mass content of the porous polymer matrix is ​​90-99%, and the mass content of the lithium-rich material particles 22 is 1-10%.

[0052] In some embodiments, the composite membrane has a thickness of 2 μm to 40 μm.

[0053] When the thickness of the composite separator is within the above range, it can effectively block the positive electrode and the negative electrode while taking into account both ion permeability and lithium replenishment performance, and at the same time has a certain mechanical strength to prevent puncture.

[0054] In some embodiments, the pore size of the composite membrane is 20 nm to 70 nm, and the porosity of the composite membrane is 20% to 70%.

[0055] The pore size and porosity of the composite membrane affect the electrolyte permeability of the composite membrane on the one hand, and on the other hand, they also affect the barrier effect of the composite membrane on the positive and negative electrodes; when the pore size and porosity of the composite membrane are within the above range, the short circuit between the positive and negative electrodes is prevented and the self-discharge rate is reduced; at the same time, it also has good electrolyte permeability and improves ion conductivity.

[0056] Another embodiment of the present application provides a battery, comprising a positive electrode, a negative electrode, and the composite separator as described above, wherein the composite separator is located between the positive electrode and the negative electrode.

[0057] Due to the use of the composite diaphragm as described above, it has a higher ionic conductivity, can reduce the impedance of the battery, improve the battery capacity retention rate and cycle life, and at the same time, the composite diaphragm has a lithium replenishing effect. When the battery is first formed, the lithium ions obtained by decomposing the lithium-rich material particles 22 have a supplementary effect on the lithium ion concentration in the electrolyte, thereby reducing the irreversible capacity loss of the battery during the formation stage.

[0058] In some embodiments, the first separator layer 1 of the composite separator faces the negative electrode, and the second separator layer 2 of the composite separator faces the positive electrode.

[0059] Since lithium-rich material particles 22 are dispersed in the second diaphragm layer 2, the lithium-rich material particles 22 need to decompose under high voltage (3.5~4.1V). Therefore, the second diaphragm layer 2 of the composite diaphragm is directed toward the positive electrode, which is beneficial for contacting the second diaphragm layer 2 with the positive electrode, thereby promoting the decomposition of the lithium-rich material particles 22 in the second diaphragm layer 2 and improving its lithium replenishment effect.

[0060] Another embodiment of the present application provides an electrical device including the battery described above.

[0061] In some embodiments, the electrical equipment is selected from energy storage systems, electric vehicles, electronic products or electrical appliances.

[0062] The present application is further described below through examples.

[0063] Example 1

[0064] This embodiment provides a composite diaphragm and a battery, the battery comprising a positive electrode, a negative electrode and a composite diaphragm, the composite diaphragm comprising a stacked first diaphragm layer and a second diaphragm layer, the first diaphragm layer of the composite diaphragm facing the negative electrode, the second diaphragm layer of the composite diaphragm facing the positive electrode, the first diaphragm layer comprising a first porous polymer matrix layer and solid electrolyte particles dispersed in the first porous polymer matrix layer, the material of the first porous polymer matrix layer is selected from polyvinylidene fluoride having a melting point of 155°C, the solid electrolyte particles are selected from LLZO (Li7La3Zr2O 12 ), the second diaphragm layer includes a second porous polymer matrix layer and lithium-rich material particles dispersed in the second porous polymer matrix layer, the material of the second porous polymer matrix layer is selected from polyvinylidene fluoride with a melting point of 155°C, the lithium-rich material particles are selected from Li5FeO4 with a particle size of 1.5μm, the thickness of the first diaphragm layer is 4.5μm, the thickness of the second diaphragm layer is 4.5μm, and the total thickness of the composite diaphragm is 9μm.

[0065] Example 2

[0066] This embodiment provides a composite diaphragm and a battery, the battery includes a positive electrode, a negative electrode and a composite diaphragm, the composite diaphragm includes a stacked first diaphragm layer and a second diaphragm layer, the first diaphragm layer of the composite diaphragm faces the negative electrode, the second diaphragm layer of the composite diaphragm faces the positive electrode, the first diaphragm layer includes a first porous polymer matrix layer and solid electrolyte particles dispersed in the first porous polymer matrix layer, the material of the first porous polymer matrix layer is selected from ultra-high density polyethylene with a melting point of 135°C, and the solid electrolyte particles are selected from LATP (Li 1.3 Al 0.3 Ti 1.7(PO4)3), the second diaphragm layer includes a second porous polymer matrix layer and lithium-rich material particles dispersed in the second porous polymer matrix layer, the material of the second porous polymer matrix layer is selected from ultra-high density polyethylene with a melting point of 135°C, the lithium-rich material particles are selected from LiCoO4 with a particle size of 1.2μm, the thickness of the first diaphragm layer is 3.5μm, the thickness of the second diaphragm layer is 5.5μm, and the total thickness of the composite diaphragm is 9μm.

[0067] Example 3

[0068] This embodiment provides a composite diaphragm and a battery, the battery comprising a positive electrode, a negative electrode and a composite diaphragm, the composite diaphragm comprising a stacked first diaphragm layer and a second diaphragm layer, the first diaphragm layer of the composite diaphragm facing the negative electrode, the second diaphragm layer of the composite diaphragm facing the positive electrode, the first diaphragm layer comprising a first porous polymer matrix layer and solid electrolyte particles dispersed in the first porous polymer matrix layer, the material of the first porous polymer matrix layer is selected from high-density polypropylene with a melting point of 165°C, the solid electrolyte particles are selected from LLZO (Li7La3Zr2O) with a particle size of 2.0 μm 12 ), the second diaphragm layer includes a second porous polymer matrix layer and lithium-rich material particles dispersed in the second porous polymer matrix layer, the material of the second porous polymer matrix layer is selected from high-density polypropylene with a melting point of 165°C, the lithium-rich material particles are selected from Li5FeO4 with a particle size of 1.5μm, the thickness of the first diaphragm layer is 5μm, the thickness of the second diaphragm layer is 7μm, and the total thickness of the composite diaphragm is 12μm.

[0069] Example 4

[0070] This comparative example provides a battery, which is similar to the battery in Example 2, except that the first separator layer of the composite separator faces the positive electrode, and the second separator layer of the composite separator faces the negative electrode.

[0071] Comparative Example 1

[0072] This comparative example provides a battery comprising a positive electrode, a negative electrode and a commercially available separator with a thickness of 12 μm (comprising a base film and an inorganic material layer disposed on the base film, wherein the inorganic material is aluminum oxide).

[0073] Battery assembly: Assemble the separator with the positive electrode, negative electrode, and electrolyte to form a battery. For the positive electrode, PVDF is dissolved in a certain amount of NMP, lithium iron phosphate and a conductive agent are added, and then coated on aluminum foil. The mass ratio of lithium iron phosphate, conductive agent (carbon black), and PVDF is 96:2:2. For the negative electrode, SBR, graphite material, and conductive agent are added to water, and then coated on copper foil. The mass ratio of graphite, conductive agent (carbon black), and SBR is 96:2:2. The electrolyte composition is: DMC:EMC:DEC:EC = 1:3:1:4, plus 1 mol / L LiPF6.

[0074] Performance Testing

[0075] The battery obtained above was tested as follows:

[0076] 1. Battery first efficiency test: Charge the battery to 3.75V at 0.2C constant current and constant voltage, with a cut-off current of 0.05C, leave it for 5 minutes, and record the charge capacity C1; discharge it to 2V at 0.5C constant current, leave it for 5 minutes, and record the discharge capacity C2; first efficiency = C2 / C1*100%;

[0077] 2. Low-temperature ionic conductivity test: Place the prepared battery in a -20°C constant temperature box for 5 hours, and then perform the ionic conductivity test according to the national standard GB-T36363 test method for ionic conductivity;

[0078] 3. Low-temperature cycle performance test: Place the prepared battery in a -10℃ constant temperature box and keep it warm for 5 hours. Then charge and discharge the battery at 0.5C / 0.5C for 50 cycles. Record the first discharge capacity and the last discharge capacity, and calculate the capacity retention rate.

[0079] 4. Battery capacity retention rate test: Charge and discharge the battery at 1C / 1C for 500 cycles, and record the battery's first cycle capacity and 500-cycle capacity. 500-cycle capacity retention rate = 500-cycle capacity / first cycle capacity * 100%.

[0080] The test results are entered in Table 1.

[0081] Table 1

[0082] From the test results in Table 1, it can be seen that the use of the composite diaphragm provided by the present application is beneficial to improving the ionic conductivity and reducing the internal resistance of the battery, thereby improving the low-temperature cycle performance and cycle life of the battery. On the other hand, the composite diaphragm plays a role in replenishing lithium, reducing the irreversible capacity loss of the battery formation, and improving the first efficiency of the battery. At the same time, from the test results of Example 2 and Comparative Example 2, it can be seen that the orientation of the composite diaphragm between the positive and negative electrodes will affect its effect on improving the battery performance. When the first diaphragm layer is facing the negative electrode and the second diaphragm layer is facing the positive electrode, it is beneficial to further improve the cycle capacity retention rate and low-temperature performance of the battery, while improving the first efficiency of the battery.

[0083] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A composite diaphragm, characterized in that: The invention comprises a first diaphragm layer (1) and a second diaphragm layer (2) which are stacked, wherein the first diaphragm layer (1) comprises solid electrolyte particles (11), and the second diaphragm layer (2) comprises lithium-rich material particles (22).

2. The composite diaphragm according to claim 1, characterized in that: The particle size D50 of the solid electrolyte particles (11) is 0.5 μm to 5 μm.

3. The composite diaphragm according to claim 1 or 2, characterized in that: The first separator layer (1) further comprises a first porous polymer matrix layer (12), and the solid electrolyte particles (11) are dispersed in the first porous polymer matrix layer (12).

4. The composite diaphragm according to any one of claims 1 to 3, characterized in that: The material of the first porous polymer matrix layer (12) is selected from high-density polyethylene, ultra-high-density polyethylene, low-density polyethylene, high-density polypropylene, ultra-high-density polypropylene, polyimide or polyvinylidene fluoride.

5. The composite diaphragm according to any one of claims 1 to 4, characterized in that: The thickness of the first diaphragm layer (1) is 1 μm to 20 μm; and / or the thickness of the second diaphragm layer (2) is 1 μm to 20 μm.

6. The composite diaphragm according to any one of claims 1 to 5, characterized in that: The particle size D50 of the lithium-rich material particles (22) is 0.5 μm to 5 μm.

7. The composite diaphragm according to any one of claims 1 to 6, characterized in that: The solid electrolyte particles (11) are selected from Li 1.3 Al 0.3 Ti 1.7 (PO4)3, Li7La3Zr2O 12 , Li 0.34 La 0.56 TiO3 or Li 1.5 Al 0.5 Ge 1.5 (PO4)3; and / or the lithium-rich material particles (22) are selected from Li5FeO4, Li2Ni5O4, Li2MnO3, LiCoO4, Li6MnO4 or LiReO6.

8. The composite diaphragm according to any one of claims 1 to 7, characterized in that: The second separator layer (2) further comprises a second porous polymer matrix layer (21), and the lithium-rich material particles (22) are dispersed in the second porous polymer matrix layer (21).

9. The composite diaphragm according to any one of claims 1 to 8, characterized in that: The material of the second porous polymer matrix layer (21) is selected from high-density polyethylene, ultra-high-density polyethylene, low-density polyethylene, high-density polypropylene, ultra-high-density polypropylene, polyimide or polyvinylidene fluoride.

10. The composite diaphragm according to any one of claims 1 to 9, characterized in that: The composite diaphragm has a thickness of 2 μm to 40 μm.

11. The composite diaphragm according to any one of claims 1 to 10, characterized in that: The pore size of the composite membrane is 20 μm to 70 nm, and the porosity of the composite membrane is 20% to 70%.

12. A battery, characterized in that: The invention comprises a positive electrode, a negative electrode and a composite separator as claimed in any one of claims 1 to 11, wherein the composite separator is located between the positive electrode and the negative electrode.

13. The battery according to claim 12, characterized in that The first diaphragm layer (1) of the composite diaphragm faces the negative electrode, and the second diaphragm layer (2) of the composite diaphragm faces the positive electrode.

14. An electrical device, characterized in that: A battery comprising any one of claims 12 to 13.

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