Composite electrode sheet roll core and lithium-sodium battery

Abstract

This invention discloses a composite electrode core and a lithium-sodium battery, belonging to the field of energy storage batteries. The composite electrode core and lithium-sodium battery include a composite positive electrode, a composite negative electrode, and a separator. The composite positive electrode includes a positive current collector, a sodium-ion battery material coating, and a lithium-ion battery material coating, which are respectively disposed on both sides of the positive current collector. The areal density of the sodium-ion battery material coating is 50-300 g / m³. 2 The areal density of the lithium battery material coating is 80-300 g / m³. 2 The composite negative electrode sheet includes a negative electrode current collector, a hard carbon material coating, and a graphite material coating, with the hard carbon material coating and graphite material coating respectively disposed on both sides of the negative electrode current collector; the areal density of the hard carbon material coating is 30-200 g / m³. 2 The areal density of the graphite coating is 30-195 g / m³. 2 This lithium-sodium battery combines the advantages of both lithium-ion and sodium-ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of energy storage battery technology, specifically relating to a composite electrode sheet core and a lithium-sodium battery. Background Technology

[0002] Lithium-ion batteries boast advantages such as high energy density, high power density, and a wide charge / discharge voltage window. However, their performance shortcomings are equally significant: First, their low-temperature performance is poor; for example, lithium iron phosphate batteries retain only about 50% of their capacity at -20°C and are almost unable to discharge at -40°C. Second, their over-discharge tolerance is insufficient; when the discharge voltage drops below 1.8V, the copper foil on the negative electrode undergoes irreversible decomposition, rendering the cell unusable. Furthermore, their cycle life varies considerably, ranging from 1500 to 15000 cycles. Lithium resources are limited, while sodium resources are extremely abundant, making sodium-ion batteries a focus of widespread attention. Sodium-ion batteries also exhibit excellent performance in terms of cycle stability, low-temperature discharge performance, and over-discharge tolerance, demonstrating enormous application potential.

[0003] Combining lithium-ion and sodium-ion battery materials allows for the integration of the energy density and wide voltage window of lithium-ion batteries with the low-temperature performance, long cycle life, and over-discharge performance of sodium-ion batteries, thus achieving a balance of advantages in cost, energy density, power density, high and low temperature performance, cycle life, and safety. Some researchers have introduced hybrid ion systems and developed lithium-sodium hybrid batteries. The core components of a lithium-sodium hybrid battery system include positive and negative electrodes, an electrolyte, a separator, and a battery management system. The positive electrode material is primarily a high-specific-capacity lithium / sodium compound, while the negative electrode often uses lithium / sodium metals, alloys, or carbon-based materials.

[0004] Chinese patent document CN117013054A discloses a hybrid lithium-sodium battery, which consists of a positive electrode, a negative electrode, and an electrolyte. The positive electrode material is a mixture of sodium-ion battery positive electrode materials and lithium-ion battery positive electrode materials; the negative electrode is a carbon-based material; and the electrolyte is an ether-containing solvent and / or an ester-containing solvent, using organic lithium salts and / or inorganic lithium salts, as well as organic sodium salts and / or inorganic sodium salts, as solutes. In this hybrid lithium-sodium battery, the synergistic effect of simultaneous insertion and extraction of lithium ions and sodium ions further enhances the battery's energy density and power density. Chinese patent document CN116364880A discloses a composite lithium-sodium ion battery, comprising a lithium positive electrode and a negative electrode containing a composite of hard carbon or soft carbon and graphite or silicon-carbon. The lithium positive electrode comprises a sodium-ion positive electrode material and a lithium positive electrode material. The sodium-ion positive electrode material includes layered oxide sodium-ion positive electrodes, Prussian blue compound sodium-ion positive electrodes, and polyanionic compounds. The lithium positive electrode material includes lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, and lithium-rich manganese-based positive electrode materials. This invention prepares the lithium positive electrode by using sodium-ion positive electrode materials and lithium positive electrode materials, solving the problems of low initial efficiency, low capacity, and low plateau requiring an increase in the number of batteries connected in series. However, the above invention may have issues with cycle stability. Summary of the Invention

[0005] To address the issue that existing single lithium-ion batteries, sodium-ion batteries, or external series-parallel configurations of lithium-ion and sodium-ion batteries cannot simultaneously achieve optimal performance in terms of low temperature, rate capability, safety, and cycle life, this invention provides a composite electrode core and a lithium-sodium battery. It features targeted designs for the positive and negative electrode structures, combining the advantages of both lithium-ion and sodium-ion batteries. This improves the energy density and power density of the cell, enhances low-temperature performance, and, most importantly, achieves ultra-long cycle life and high reliability.

[0006] The specific technical solution adopted is as follows: A composite electrode core includes a composite positive electrode, a composite negative electrode, and a separator; The composite positive electrode includes a positive current collector, a sodium-ion battery material coating, and a lithium-ion battery material coating, with the sodium-ion battery material coating and the lithium-ion battery material coating respectively disposed on both sides of the positive current collector; the thickness of the sodium-ion battery material coating can be set to 20-150 μm, and the areal density is 50-300 g / m³. 2 The thickness of the lithium battery material coating can be set to 30-200 μm, and the areal density to be 80-300 g / m³. 2 ; The composite negative electrode sheet includes a negative electrode current collector, a hard carbon material coating, and a graphite material coating, with the hard carbon material coating and graphite material coating respectively disposed on both sides of the negative electrode current collector; the thickness of the hard carbon material coating can be set to 30-220 μm, and the areal density is 30-200 g / m³.2 The thickness of the graphite coating can be set to 20-150 μm, and the areal density to be 30-195 g / m³. 2 ; In the aforementioned composite cathode, when the sodium electrode material uses NaNi... 0.33 Fe 0.33 Mn 0.33 O2 (NNFM) or NaCu 0.04 Ni 0. 3Fe 0.22 Mn 0.33 Ti 0.11 When using O2 (NCFM), LiNi is used as the lithium battery material. 0.33 Co 0.33 Mn 0.33 O2 (NCM111), LiNi5Co2Mn3O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622) or LiNi 0.8 Co 0.15 Al 0.05 O2 (NCA); when sodium-ion materials use Na 0.67 When MnO2 or Na2Fe(SO4)2 (NFS) is used, LiMn2O4 (LMO) is used as the lithium battery material; when Na4Fe3(PO4)2P2O7 (NFPP), Na3V2(PO4)3 (NVP), Na3V2(PO4)2F3 (NVPF), Na2Mn[Fe(CN)6] or Na2Fe[Fe(CN)6] is used as the sodium battery material, LiFePO4 (LFP) is used as the lithium battery material.

[0007] Unlike existing technologies that combine lithium-ion and sodium-ion batteries separately in series / parallel, this invention fabricates a composite electrode core and a lithium-sodium battery using a specific method. The current collector of the composite positive electrode is coated with both sodium and lithium-ion materials, while the current collector of the composite negative electrode is coated with both hard carbon and graphite materials. The sodium and hard carbon coatings are located on opposite sides of the separator, as are the lithium-ion and graphite coatings. During charging, lithium and sodium are extracted from their respective coatings and enter their corresponding graphite / hard carbon coatings; during discharging, lithium and sodium are extracted from their respective graphite / hard carbon negative electrodes and enter their respective positive electrode coatings. Among them, the phase structure or charge / discharge voltage of the positive electrode material in the composite positive electrode sheet are similar, which can be well matched for charge and discharge. The ester solvent electrolyte and the separator with similar porosity can provide mass transfer space for lithium / sodium solvation. Due to the combination of the structure and characteristics of both lithium and sodium electrodes, it can effectively bring out the high specific energy of lithium batteries and the long cycle, high safety and excellent low temperature performance of sodium batteries, thereby avoiding the weaknesses of lithium batteries such as over-discharge and low temperature and sodium batteries such as low energy density.

[0008] Furthermore, the composite positive electrode sheet and the composite negative electrode sheet are stacked in sequence, separated by a diaphragm, and then rolled to obtain a composite electrode sheet core.

[0009] Furthermore, the membrane is coated with sodium battery material and hard carbon material on both sides, or the membrane is coated with lithium battery material and graphite material on both sides.

[0010] Furthermore, the sodium battery material coating includes sodium battery material, binder, and conductive agent in a mass ratio of 1:1.5%-10%:0.2%-5%; the lithium battery material coating includes lithium battery material, binder, and conductive agent in a mass ratio of 1:1.5%-20%:0.2%-10%; the hard carbon material coating includes hard carbon material, binder, and conductive agent in a mass ratio of 1:1.5%-15%:0.2%-15%; and the graphite material coating includes graphite material, binder, and conductive agent in a mass ratio of 1:1%-15%:0.2%-15%.

[0011] Preferably, the sodium-electric material is NaNi. 0.33 Fe 0.33 Mn 0.33 O2 or Na4Fe3(PO4)2P2O7, the lithium battery material being described is LiNi 0.6 Co 0.2 Mn 0.2O2 or LiFePO4; the hard carbon material includes at least one of biomass hard carbon (GHC300, BSHC300C, BSHC320, BSHC350, type2, type1, YHC-320, YHC330, YHC400, HNa104, etc.), resin hard carbon, pitch-based hard carbon, and composite hard carbon (such as phosphorus carbon, tin carbon, antimony carbon, etc.); the graphite material includes at least one of artificial graphite, natural graphite, mesophase carbon microspheres, and silicon-carbon composite materials.

[0012] The conductive agent includes at least one of carbon nanotubes, conductive carbon black, graphene, Ketjen black, and carbon fiber.

[0013] The adhesive includes at least one of sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PTFE), polyacrylonitrile-acrylonitrile (PAA), polyimide (PI), polymethyl methacrylate (PMMA), and sodium alginate.

[0014] Furthermore, a sodium-ion battery material slurry with a solid content of 45-75 wt% is coated onto the positive electrode current collector to form a sodium-ion battery material coating; a lithium-ion battery material slurry with a solid content of 40-76 wt% is coated onto the positive electrode current collector to form a lithium-ion battery material coating; a hard carbon material slurry with a solid content of 40-65 wt% is coated onto the negative electrode current collector to form a hard carbon material coating; and a graphite material slurry with a solid content of 45-70 wt% is coated onto the negative electrode current collector to form a hard carbon material coating.

[0015] Furthermore, aluminum foil is chosen as the positive current collector, and copper foil is chosen as the negative current collector.

[0016] The separator can be PP separator, PE separator, PI separator, PVDF separator, PET separator, etc., or the above-mentioned separators coated with functional coatings (alumina coating, boehmite coating, lithium / sodium supplementation coating, etc.).

[0017] The present invention also provides a lithium-sodium battery, comprising the composite positive electrode, the composite negative electrode, a separator, and an electrolyte; Electrolytes consist of sodium salts, lithium salts, solvents, and additives; Sodium salts include NaPF6 and NaFSI; Lithium salts include LiPF6; Solvents selected include cyclic solvents (ethylene carbonate EC, propylene carbonate PC, etc.) and chain solvents (dimethyl carbonate DMC, ethyl methyl carbonate EMC, etc.). Additives include fluoroethylene carbonate (FEC), propylene sulfonate lactone (PS), vinylene carbonate (VC), or vinyl sulfate (DTD), etc. The electrolyte injection coefficient is 3.5 g / Ah to 6 g / Ah; The molar ratio of sodium salt to lithium salt is 0.5-2:1, the total molar number of sodium salt and lithium salt is 1-2.5M, the additive content is ≤10%, and the balance is solvent.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention integrates composite positive and negative electrode sheets with specific structures to produce a lithium-sodium battery that overcomes the weaknesses of single sodium-ion batteries (low energy density) and single lithium-ion batteries (poor low-temperature performance, low safety and reliability, and low cycle life). It combines the advantages of sodium-ion batteries (low-temperature performance, rate performance, safety performance, and cycle performance) with the high energy density of lithium-ion batteries, ensuring a more balanced performance in terms of energy density, power density, low-temperature performance, safety performance, and cycle performance, and improving its service life in the energy storage field. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the composite positive electrode.

[0020] Figure 2 This is a schematic diagram of the composite negative electrode.

[0021] Figure 3 This is a schematic diagram of the structure of the composite electrode core.

[0022] Figure 4 The graph shows the cycle performance of the lithium-sodium battery in Example 1 at 0.5°C. Detailed Implementation

[0023] To make the objectives, features, and advantages of this invention more apparent and understandable, a detailed description is provided below through specific embodiments. Many specific details are set forth in the following description to provide a thorough understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below. Technical features in various embodiments of the invention can be combined appropriately without mutual conflict.

[0024] Unless otherwise specified, the operating methods in the following examples are generally performed under conventional conditions or as recommended by the manufacturer. Contents not described in detail in this specification are prior art known to those skilled in the art. Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0025] Example 1 For a detailed schematic diagram of the composite positive electrode sheet prepared in this embodiment, please refer to [link / reference]. Figure 1 The specific preparation method is as follows: LiNi 0.6 Co 0.2Mn 0.2 O2, PVDF, and conductive carbon black SP were uniformly mixed in NMP at a mass ratio of 96.5%, 2%, and 1.5% (lithium battery material slurry solid content 72.5 wt%, viscosity 8500 CP, fineness 15 μm). The mixture was then coated onto one side of an aluminum foil, with the surface density of the coating controlled at 120 ± 2 g / m². 2 ; NaNi 0.33 Fe 0.33 Mn 0.33 O2, PVDF, carbon nanotubes (CNTs), and SP were uniformly mixed in NMP at a mass ratio of 95.5%, 2.5%, 1.5%, and 0.5% (sodium-ion material slurry solid content 52.5 wt%, viscosity 5500 CP, fineness 15 μm). The mixture was then coated onto the other side of an aluminum foil, with the surface density of the coating controlled at 150 ± 2 g / m². 2 This forms a composite positive electrode sheet with a compaction density of 3.25 g / cc.

[0026] For a detailed schematic diagram of the composite negative electrode sheet prepared in this embodiment, please refer to [link / reference]. Figure 2 The specific preparation method is as follows: Artificial graphite, SP, sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are uniformly mixed in H2O at a mass ratio of 95%:0.4%:1.2%:3.4% (graphite slurry solid content 50wt%, viscosity 5000CP, fineness 10μm). This mixture is then coated onto one side of a copper foil, controlling the surface density of the coating on one side to be 75±2 g / m². 2 Biomass-based hard carbon (BSHC320): SP: CMC: SBR were mixed evenly in H2O at a mass ratio of 95.5%:0.5%:1%:3% (hard carbon material slurry solid content 52wt%, viscosity 5500CP, fineness 10μm). The mixture was then coated onto the other side of a copper foil, controlling the surface density of the coating to be 80±2 g / m². 2 This forms a composite negative electrode sheet with a compaction density of 1.05 g / cc.

[0027] The resulting composite positive electrode and composite negative electrode are arranged according to... Figure 3The composite positive and negative electrodes are stacked sequentially, separated by a separator, forming a Li / Na core structure. The core is then encapsulated in a 71173 aluminum shell and vacuum-baked and dried. Electrolyte is then injected into the aluminum shell. The electrolyte specifications are: 1M LiPF6 / 1MNaPF6 / 0.5MNaFSI, with a mixed solvent of PC, EC, DEC, and EMC in a mass ratio of 4:4:2:1. Additives include DTD (specific addition amount can be selected from 1.0wt%~2.0wt%), PS (specific addition amount can be selected from 0.2wt%~0.8wt%), FEC (specific addition amount can be selected from 0.5wt%~2.0wt%), and VC (specific addition amount can be selected from 0.02wt%~0.5wt%). The injection coefficient is 5.5g / Ah. After formation, a second sealing is performed to form a lithium-sodium battery.

[0028] Example 2 The specific preparation method of the composite cathode sheet in this embodiment is as follows: Lithium iron phosphate (LiFePO4) (LFP): PVDF: SP are uniformly mixed in NMP at a mass ratio of 97.0%:2%:1.0% (lithium battery material slurry solid content 65.5wt%, viscosity 6500CP, fineness 12μm), and coated on one side of aluminum foil, controlling the single-sided areal density of the coating to be 120.5±2 g / m². 2 Sodium iron pyrophosphate Na4Fe3(PO4)2P2O7 (NFPP): PVDF: CNTs: SP were uniformly mixed in NMP at a mass ratio of 95.5%:2.5%:1.5%:0.5% (sodium ferric phosphate slurry solid content 52.5 wt%, viscosity 5150 CP, fineness 10 μm), and coated on the other side of aluminum foil, controlling the surface density of the coating on one side to be 175±2 g / m². 2 This forms a composite positive electrode sheet with a compaction density of 2.2 g / cc.

[0029] The specific preparation method of the composite negative electrode in this embodiment is as follows: Artificial graphite:SP:CMC:SBR is uniformly mixed into H2O at a mass ratio of 95%:0.4%:1.2%:3.4% (graphite slurry solid content 50wt%, viscosity 4800CP, fineness 10μm), and coated onto one side of the copper foil, controlling the surface density of the coating on one side to be 70±2g / m². 2 The biomass-based hard carbon (BSHC350):SP:CMC:SBR was mixed evenly in H2O at a mass ratio of 95.5%:0.5%:1%:3% (hard carbon material slurry solid content 52 wt%, viscosity 5200 CP, fineness 10 μm). This mixture was then coated onto the other side of a copper foil, controlling the surface density of the coating to be 70 ± 2 g / m². 2 This forms a composite negative electrode sheet with a compaction density of 1.05 g / cc.

[0030] The resulting composite positive electrode and composite negative electrode are arranged according to... Figure 3 The composite positive and negative electrodes are stacked sequentially, separated by a separator, forming a Li / Na core structure. The core is then encapsulated in a 71173 aluminum shell and vacuum-baked. Electrolyte is then injected into the aluminum shell. The electrolyte specifications are: 1M LiPF6 / 1M NaPF6 / 0.5NaFSI, with a mixed solvent of PC, EC, DEC, and EMC in a mass ratio of 4:4:2:1. Additives include DTD (selectable from 1.0wt% to 2.0wt%), PS (selectable from 0.2wt% to 0.8wt%), FEC (selectable from 0.5wt% to 2.0wt%), and VC (selectable from 0.02wt% to 0.5wt%). The injection coefficient is 5.8g / Ah. After formation, the shell is resealed to form a lithium-sodium battery.

[0031] Comparative Example 1 Preparation of positive electrode: Both sides of the aluminum foil are LiNi 0.6 Co 0.2 Mn 0.2 O2 coating, LiNi on each side 0.6 Co 0.2 Mn 0.2 The preparation method of the O2 coating is the same as that in Example 1, and the process parameters are kept consistent, and a positive electrode sheet is prepared.

[0032] Preparation of negative electrode: Both sides of the copper foil are coated with graphite. The preparation method of the graphite coating on each side is the same as in Example 1, and the process parameters are kept consistent to prepare the negative electrode.

[0033] The separator-negative electrode-separator-positive electrode-separator is stacked to form a core, which is then encapsulated in a 71173 aluminum shell. After baking, it is injected with electrolyte, which is 1 M LiPF6, and the solvent EC / DEC / EMC mass ratio is 1:1:1. Then it undergoes formation and capacity testing to form a lithium battery.

[0034] Comparative Example 2 Preparation of positive electrode: Both sides of the aluminum foil are NaNi 0.33 Fe 0.33 Mn 0.33 O2 coating, NaNi on each side 0.33 Fe 0.33 Mn 0.33 The preparation method of the O2 coating is the same as that in Example 1, and the process parameters are kept consistent, and a positive electrode sheet is prepared.

[0035] Preparation of negative electrode: Both sides of the copper foil are coated with hard carbon. The preparation method of the hard carbon coating on each side is the same as in Example 1, and the process parameters are kept consistent to prepare the negative electrode.

[0036] The separator-negative electrode-separator-positive electrode-separator is stacked to form a core, which is then encapsulated in a 71173 aluminum shell. After baking, the electrolyte is injected. The electrolyte is 1M NaPF6 / 0.5M NaFSI, and the solvent PC / DEC / EMC mass ratio is 1:1:1. Then, it undergoes formation and capacity testing to form a sodium battery.

[0037] Comparative Example 3 Preparation of positive electrode sheet: Both sides of the aluminum foil are coated with LiFePO4. The preparation method of the LiFePO4 coating on each side is the same as in Example 2, and the process parameters are kept consistent to prepare the positive electrode sheet.

[0038] Preparation of negative electrode sheet: In this comparative example, both sides of the copper foil are coated with graphite. The preparation method of the graphite coating on each side is the same as that in Example 2, and the process parameters are kept consistent to prepare the negative electrode sheet.

[0039] The separator-negative electrode-separator-positive electrode-separator is stacked to form a core, which is then encapsulated in a 71173 aluminum shell. After baking, it is injected with electrolyte, which is 1 M LiPF6, and the solvent EC / DEC / EMC mass ratio is 1:1:1. Then it undergoes formation and capacity testing to form a lithium battery.

[0040] Comparative Example 4 Preparation of positive electrode sheet: Both sides of the aluminum foil are coated with NFPP. The preparation method of the NFPP coating on each side is the same as in Example 2, and the process parameters are kept consistent to prepare the positive electrode sheet.

[0041] Preparation of negative electrode: Both sides of the copper foil are coated with hard carbon. The preparation method of the hard carbon coating on each side is the same as in Example 2, and the process parameters are kept consistent to prepare the negative electrode.

[0042] The separator-negative electrode-separator-positive electrode-separator is stacked to form a core, which is then encapsulated in a 71173 aluminum shell. After baking, the electrolyte is injected. The electrolyte is 1M NaPF6 / 0.5M NaFSI, and the solvent PC / DEC / EMC mass ratio is 1:1:1. Then, it undergoes formation and capacity testing to form a sodium battery.

[0043] Sample Analysis from Figure 4 It can be seen that the lithium-sodium battery in Example 1 retains 88.6% of its capacity after 11,584 cycles at room temperature (0.5C / 0.5C). Figure 4 The curves for two identical cells (the dashed line represents the subsequent trend) predict that the retention rate will be over 80% after 30,000 cycles and over 70% after 50,000 cycles, making it a battery with an ultra-long cycle life.

[0044] The battery performance of Examples 1-2 and Comparative Examples 1-4 was tested, and the results are shown in Table 1.

[0045] Table 1 Comparison of Lithium-Sodium Batteries and Single Lithium / Sodium Batteries

[0046] Table 1 shows the performance data of the lithium-sodium secondary battery of the present invention. Compared with lithium batteries of the same system, its low-temperature performance and cycle performance are improved. Moreover, the lithium-sodium secondary battery has the energy density of both lithium batteries and sodium batteries. Compared with sodium batteries alone, it has been greatly improved in terms of energy density, cycle performance and low temperature performance.

[0047] The embodiments described above provide a detailed explanation of the technical solutions of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite electrode core, characterized in that, Includes composite positive electrode, composite negative electrode and separator; The composite positive electrode includes a positive current collector, a sodium-ion battery material coating, and a lithium-ion battery material coating, with the sodium-ion battery material coating and the lithium-ion battery material coating respectively disposed on both sides of the positive current collector; the areal density of the sodium-ion battery material coating is 50-300 g / m³. 2 The areal density of the lithium battery material coating is 80-300 g / m³. 2 ; The composite negative electrode sheet includes a negative electrode current collector, a hard carbon material coating, and a graphite material coating, with the hard carbon material coating and graphite material coating respectively disposed on both sides of the negative electrode current collector; the areal density of the hard carbon material coating is 30-200 g / m³. 2 The areal density of the graphite coating is 30-195 g / m³. 2 ; In the aforementioned composite cathode, when the sodium electrode material uses NaNi... 0.33 Fe 0.33 Mn 0.33 O2 or NaCu 0.04 Ni 0.3 Fe 0.22 Mn 0.33 Ti 0.11 In O2, lithium battery materials use LiNi 0.33 Co 0.33 Mn 0.33 O2, LiNi5Co2Mn3O2, LiNi 0.6 Co 0.2 Mn 0.2 O2 or LiNi 0.8 Co 0.15 Al 0.05 O2; when sodium-ion materials use Na 0.67 When MnO2 or Na2Fe(SO4)2 is used, LiMn2O4 is used as the lithium battery material; when Na4Fe3(PO4)2P2O7, Na3V2(PO4)3, Na3V2(PO4)2F3, Na2Mn[Fe(CN)6] or Na2Fe[Fe(CN)6] is used as the sodium battery material, LiFePO4 is used as the lithium battery material.

2. The composite electrode core according to claim 1, characterized in that, Composite positive and composite negative electrodes are stacked sequentially, separated by a diaphragm, and then rolled to obtain a composite electrode core.

3. The composite electrode core according to claim 2, characterized in that, The membrane has a sodium battery material coating and a hard carbon material coating on both sides, or a lithium battery material coating and a graphite material coating on both sides.

4. The composite electrode core according to claim 1, characterized in that, The sodium battery material coating comprises sodium battery material, binder, and conductive agent in a mass ratio of 1:1.5%-10%:0.2%-5%; the lithium battery material coating comprises lithium battery material, binder, and conductive agent in a mass ratio of 1:1.5%-20%:0.2%-10%; the hard carbon material coating comprises hard carbon material, binder, and conductive agent in a mass ratio of 1:1.5%-15%:0.2%-15%; and the graphite material coating comprises graphite material, binder, and conductive agent in a mass ratio of 1:1%-15%:0.2%-15%.

5. The composite electrode core according to claim 4, characterized in that, The sodium-electric material mentioned is NaNi 0.33 Fe 0.33 Mn 0.33 O2 or Na4Fe3(PO4)2P2O7, the lithium battery material being described is LiNi 0.6 Co 0.2 Mn 0.2 O2 or LiFePO4; And / or, the hard carbon material includes at least one of biomass hard carbon, resin hard carbon, pitch-based hard carbon, and composite hard carbon; And / or, the graphite material includes at least one of artificial graphite, natural graphite, mesophase carbon microspheres, and silicon-carbon composite materials.

6. The composite electrode core according to claim 4, characterized in that, The conductive agent includes at least one of carbon nanotubes, conductive carbon black, graphene, Ketjen black, and carbon fiber.

7. The composite electrode core according to claim 4, characterized in that, The adhesive includes at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber, polyvinylidene fluoride, polyacrylonitrile, polyimide, polymethyl methacrylate, and sodium alginate.

8. The composite electrode core according to claim 1, characterized in that, A sodium-ion battery material slurry with a solid content of 45-75 wt% is coated onto the positive electrode current collector to form a sodium-ion battery material coating. And / or, a lithium battery material slurry with a solid content of 40-76 wt% is coated onto the positive electrode current collector to form a lithium battery material coating; And / or, a hard carbon material slurry with a solid content of 40-65wt% is coated onto the negative electrode current collector to form a hard carbon material coating; And / or, a graphite slurry with a solid content of 45-70 wt% is coated onto the negative electrode current collector to form a hard carbon material coating.

9. A lithium-sodium battery, characterized in that, It includes the composite electrode core and electrolyte as described in any one of claims 1-8.

10. The lithium-sodium battery according to claim 9, characterized in that, The electrolyte includes sodium salt, lithium salt, solvent, and additives; sodium salt includes NaPF6 and NaFSI; lithium salt includes LiPF6; the solvent is selected from cyclic and chain structures; the molar ratio of sodium salt to lithium salt is 0.5-2:1, the total molar number of sodium salt and lithium salt is 1-2.5 M, the additive content is ≤10%, and the balance is solvent.

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