Multi-tab lithium-sodium composite battery and collector plate thereof

Abstract

The composite battery is formed by compounding a tubular sodium ion battery on the outer side and a cylindrical lithium ion battery on the inner side, so that the high safety of the sodium ion battery and the excellent charging and discharging performance at low temperature are exerted; meanwhile, the use of the internal lithium ion battery ensures the high energy density of the battery. The lithium ion battery and the sodium ion battery are both of a multi-tab design, compared with a single-tab structure, the internal resistance of the battery is lower, and the heating condition in the using process can be remarkably reduced. And the current on the sodium ion battery can be conducted to the positive terminal of the lithium ion battery through the current collecting disc, so that the internal resistance of the composite battery is smaller. In a low-temperature environment, the sodium-ion battery can be started firstly, and then the lithium-ion battery is started after the optimal working temperature of the lithium-ion battery is reached, so that the performance of the battery at low temperature is improved, and the service life of the battery is prolonged. The composite battery has the characteristics of high environment temperature adaptability, high safety, long cycle life and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of secondary batteries, and in particular relates to a multi-electrode lithium-sodium composite battery and a current collecting plate thereof. Background Art

[0002] Lithium-ion batteries are widely used in the field of electric vehicles due to their high energy density. With the increasing number of users and the wider range of usage scenarios, the safety and low-temperature adaptability of lithium batteries have received widespread attention. The performance of lithium-ion batteries in low-temperature environments will be significantly affected, mainly manifested in reduced discharge capacity, increased internal resistance, reduced charge and discharge efficiency, and increased side reactions. For example, at -20°C, the discharge capacity of lithium-ion batteries is only about 40% of that at room temperature. At the same time, people have found that sodium-ion batteries have certain advantages in safety. Due to the large radius of sodium ions and higher relative stability, they are not prone to dendrite growth problems common in lithium-ion batteries, thereby reducing battery damage and safety risks. Sodium-ion batteries perform well in safety tests such as overcharging, over-discharging, short circuit, puncture, and extrusion. They are not prone to fire and explosion. In addition, sodium-ion batteries have a wider operating temperature range and can work normally in the temperature range of -40°C to 80°C. The capacity retention rate is close to 90% in an environment of -20°C, which is better than lithium batteries.

[0003] The main shortcomings of lithium-ion batteries in terms of safety include the risk of thermal runaway. Lithium battery thermal runaway is a serious safety issue, involving a series of irreversible failure phenomena caused by a sharp rise in the internal temperature of the battery, such as capacity decay, battery deformation / rupture, fire, etc. Controlling the internal resistance of the battery and reducing the heat generated when the battery is working are the most effective measures to prevent thermal runaway of the battery. When the internal resistance of the battery increases, a large amount of Joule heat will be generated, causing the battery temperature to rise, resulting in a decrease in the battery discharge operating voltage and a shortened discharge time, which will have a serious impact on the battery performance and life. If the internal resistance of the battery is too large, the heat accumulation to a certain threshold may cause a series of problems such as battery combustion and explosion. Summary of the invention

[0004] The present invention provides a multi-electrode lithium-sodium composite battery and a current collecting plate thereof. The multi-electrode lithium-sodium composite battery has the characteristics of more stable structure, higher battery core strength, low battery internal resistance, high efficiency, good low temperature adaptability, more uniform heat dissipation, non-explosion and high safety.

[0005] In order to achieve the above object, the present invention adopts the following specific technical solutions:

[0006] The present invention provides a multi-electrode lithium-sodium composite battery, which comprises a tubular sodium-ion battery, a cylindrical lithium-ion battery and a current collecting plate; the sodium-ion battery is coaxially installed on the outer peripheral side of the lithium-ion battery; the sodium-ion battery and the lithium-ion battery are in a parallel structure and can be charged and discharged independently; the lithium-ion battery is used for energy storage and maintaining the working voltage; the sodium-ion battery is used for providing temperature control to assist the lithium-ion battery in energy storage, and can block the explosion of the lithium-ion battery;

[0007] The lithium-ion battery has a positive terminal and a negative terminal; the positive electrodes of the sodium-ion battery and the lithium-ion battery both adopt a multi-electrode structure; and the current collecting plate is welded and connected to the poles of the sodium-ion battery and the lithium-ion battery.

[0008] Furthermore, the top of the sodium ion battery is evenly distributed with a plurality of tabs along the circumferential direction;

[0009] The outer periphery of the current collecting plate is provided with a shovel-shaped structure corresponding to the pole ears of the sodium ion battery one by one, and a boss is provided in the center;

[0010] The shovel-shaped structure is welded to the corresponding pole ear; the internal cavity of the boss is larger than the positive terminal of the lithium-ion battery, is welded to the pole ear of the lithium-ion battery, and is sleeved on the positive terminal of the lithium-ion battery.

[0011] Furthermore, the shovel-shaped structure and the boss are both provided with welding gaps for welding and connecting the tabs.

[0012] Furthermore, the sodium ion battery and the lithium ion battery are in contact with each other through a circumferential surface.

[0013] Furthermore, a liquid cooling system is arranged between the lithium-ion battery and the sodium-ion battery.

[0014] Furthermore, both the sodium ion battery and the lithium ion battery are manufactured using a battery winding process.

[0015] Furthermore, the inner peripheral shell of the sodium ion battery and the outer peripheral shell of the lithium ion battery share the same shell.

[0016] Furthermore, the manufacturing method of the positive electrode sheet of the sodium ion battery and the lithium ion battery is: the positive electrode material is mixed with a conductive agent and a binder, and then coated on an aluminum foil current collector, and then compacted after drying;

[0017] The manufacturing method of the negative electrode sheet of the sodium ion battery and the lithium ion battery is as follows: the negative electrode material is mixed with a conductive agent and a binder, and then coated on a copper foil current collector, and then compacted after drying.

[0018] Furthermore, the conductive agent is carbon black or the like; the binder is polyvinylidene fluoride (PVDF) or the like;

[0019] The positive electrode material of the lithium-ion battery is selected from one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, nickel cobalt manganese, nickel cobalt aluminum, lithium iron phosphate, lithium-rich manganese-based materials, layered lithium nickel oxide, and lithium manganese oxide;

[0020] The positive electrode material of the sodium ion battery is selected from one or more of metal oxides, polyanion compounds, Prussian blue compounds, phosphate compounds, and Prussian white compounds;

[0021] The negative electrode material of the lithium ion battery and the sodium ion battery is selected from one or more of natural graphite, artificial graphite, mesophase carbon microspheres, soft carbon, hard carbon, graphene, silicon-based and composite materials thereof.

[0022] Furthermore, the outer diameter of the sodium ion battery is 18 mm-100 mm;

[0023] The outer diameter of the lithium-ion battery is 15 mm to 90 mm;

[0024] The heights of the sodium ion battery and the lithium ion battery are both 40 mm-200 mm.

[0025] In addition, the present invention also provides a current collecting plate for the above-mentioned multi-electrode lithium-sodium composite battery, wherein the outer periphery of the current collecting plate is provided with a shovel-shaped structure corresponding to the pole ears of the sodium ion battery one by one, and a boss is provided in the center;

[0026] The shovel-shaped structure is used for welding connection with the corresponding pole lug;

[0027] The inner cavity of the boss is larger than the positive terminal of the lithium-ion battery, is welded to the tab of the lithium-ion battery, and is sleeved on the positive terminal of the lithium-ion battery.

[0028] Furthermore, the shovel-shaped structure and the boss are both provided with welding gaps for welding and connecting the tabs.

[0029] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0030] The multi-electrode lithium-sodium composite battery of the present invention is composed of a cylindrical lithium-ion battery in the center and a tubular sodium-ion battery on the outside, and fully utilizes the high safety and excellent low-temperature charging and discharging performance of the sodium-ion battery, as well as the high energy density of the lithium-ion battery; at the same time, the positive electrodes of the sodium-ion battery and the lithium-ion battery adopt a multi-electrode structure and are welded and connected with a current collecting plate. Compared with a single-electrode structure, the battery has a lower internal resistance and significantly reduces the heat generation during use; the sodium-ion battery and the lithium-ion battery are in a parallel structure and can be charged and discharged independently; the sodium-ion battery is used to provide temperature control to assist the lithium-ion battery in energy storage, and can block the explosion of the lithium-ion battery together with the current collecting plate; the composite battery adopting the above structure has the characteristics of more stable structure under external force conditions, higher battery core strength, low battery internal resistance, good low-temperature adaptability, more uniform heat dissipation, not easy to explode, and good safety.

[0031] The above-mentioned multi-pole lithium-sodium composite battery can be used as an on-board power battery and is suitable for fields such as electric vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the three-dimensional structure of the multi-electrode lithium-sodium composite battery of the present invention;

[0033] Figure 2 It is a schematic diagram of the assembly structure of lithium-ion battery and sodium-ion battery cell;

[0034] Figure 3 It is a schematic diagram of the structure of the collecting plate.

[0035] Among them, 1-sodium ion battery, 2-ear, 3-lithium ion battery, 4-positive terminal, 5-liquid cooling system, 6-shovel-like structure, 7-first welding seam, 8-boss, 9-second welding seam. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] The embodiment of the present invention provides a multi-electrode lithium-sodium composite battery, such as Figure 1As shown in the structure, the composite battery includes a tubular sodium ion battery 1, a cylindrical lithium ion battery 3 and a current collecting plate; the sodium ion battery 1 is coaxially installed on the outer peripheral side of the lithium ion battery 3; the sodium ion battery 1 and the lithium ion battery 3 are in parallel structure and can be charged and discharged independently; the sodium ion battery 1 and the lithium ion battery 3 have independent battery management systems, which can charge and discharge the sodium ion battery 1 and the lithium ion battery 3 respectively; the lithium ion battery 3 is used to store energy and maintain the working voltage of the entire composite battery; the volume of the sodium ion battery 1 is much smaller than that of the lithium ion battery 3, and the sodium ion battery 1 is used to provide temperature control to assist the lithium ion battery 3 in energy storage, and can block further losses caused by the explosion of the lithium ion battery 3 when the lithium ion battery 3 is thermally runaway.

[0038] The lithium-ion battery 3 has a positive terminal 4 and a negative terminal; the positive electrodes of the sodium-ion battery 1 and the lithium-ion battery 3 both adopt a multi-pole ear structure; the current collector is welded to the pole ears 2 of the sodium-ion battery 1 and the lithium-ion battery 3. The sodium-ion battery 1 has no positive terminal 4, and its positive current is exported to the positive terminal 4 of the lithium-ion battery 3 by the current collector, and the battery is controlled by the battery management system. The sodium-ion battery 1 and the lithium-ion battery 3 have only one positive terminal 4, and the positive terminal 4 is welded to the current collector to output current. The current collector of the lithium-ion battery 3 can connect the current of the lithium-ion battery 3 to the positive terminal 4, and the current collector of the sodium-ion battery 1 can connect the positive current of the sodium-ion battery 1 to the positive terminal 4 of the lithium-ion battery 3.

[0039] The temperature control management strategy of the composite battery is as follows: in a low temperature environment, the sodium ion battery 1 is first discharged, and the lithium ion battery 3 is heated to reach the optimal operating temperature before the lithium ion battery 3 is started.

[0040] In the above composite battery, Figure 2As shown, the top of the sodium ion battery 1 is evenly distributed with multiple pole ears 2 along the circumferential direction; the outer periphery of the current collecting plate is provided with a shovel-shaped structure 6 corresponding to the pole ears 2 of the sodium ion battery 1, and a boss 8 is provided in the center; the outer periphery of the current collecting plate is evenly distributed with multiple flat shovel-shaped structures 6, and only one end of the flat shovel-shaped structure 6 is connected to the current collecting plate, and the other part is separated from the current collecting plate, in order to provide tolerance compensation during welding. The shovel-shaped structure 6 is welded and connected with the corresponding pole ears 2; the current collecting plate has a boss 8 in the middle, and the inside of the boss 8 forms a cavity for accommodating the positive terminal 4 of the lithium ion battery 3. The internal cavity of the boss 8 is slightly larger than the positive terminal 4 of the lithium ion battery 3, so that it can be just covered on the positive terminal 4 and welded and connected with the pole ear of the lithium ion battery 3. The boss 8 can be a circular boss, and the diameter of the internal cavity of the boss 8 is larger than the diameter of the positive terminal 4. The current collecting plate can directly conduct the current on the positive pole ear 2 of the sodium ion battery 1 to the positive terminal 4 of the lithium ion battery 3 by welding between the pole ears. The current collecting plate can collect the current of the sodium ion battery 1 and collect it to the positive terminal 4 of the lithium ion battery 3, so as to facilitate the unified management of the battery management system.

[0041] The use of the above-mentioned current collecting plate can reduce the internal resistance of the battery cell and reduce the heating of the battery.

[0042] In order to achieve the connection between the current collecting plate and the lithium-ion battery 3 and the sodium-ion battery 1, the shovel-shaped structure 6 and the boss 8 are both provided with welding gaps for welding and connecting the pole lugs 2, such as Figure 3 As shown, the shovel-shaped structure 6 on the outer peripheral side of the current collecting disk is provided with a first welding gap that penetrates through, and the boss 8 in the center of the current collecting disk is provided with a second welding gap that penetrates through. The shovel-shaped structure 6 and the boss 8 on the current collecting disk are both provided with welding seam structures, the first welding gap on the flat shovel-shaped structure 6 is used to weld the current collecting disk and the positive pole ear 2 of the sodium ion battery 1, and the second welding gap on the boss 8 is used to weld the current collecting disk and the positive terminal 4 of the lithium ion battery 3. The boss 8 in the middle of the current collecting disk is a cylindrical structure, which can be closely matched with the positive terminal 4 of the lithium ion battery 3. The inside of the boss 8 is a hollow structure, which is convenient for the subsequent battery management system to provide structural support for the charging and discharging of the lithium ion battery 3 and the sodium ion battery 1 respectively. The lithium ion battery 3 may also have a collecting disk structure inside. Since the design of the existing collecting disk is relatively complete, this embodiment will not be repeated. There are two collecting disk structures at the positive electrode of the battery, and only the collecting disk of the tubular sodium ion battery 1 is described in the embodiment of the present invention.

[0043] The sodium ion battery 1 and the lithium ion battery 3 can be spaced apart or in contact with each other through a circumferential surface, and there is no point contact or line contact, so that the composite battery has the characteristics of more stable structure and more uniform heat dissipation under external force conditions. Due to the more uniform force, the battery cell has higher strength and is not easy to explode under special circumstances.

[0044] When the inner shell of the sodium ion battery 1 is separated from the outer shell of the lithium ion battery 3, a liquid cooling system 5 is arranged between the lithium ion battery 3 and the sodium ion battery 1. The liquid cooling system 5 can contact the sodium ion battery 1 and the lithium ion battery 3 at the same time to increase the heat dissipation area, and can also transfer heat to the lithium ion battery 3 evenly during the preheating process of the sodium ion battery 1. The sodium ion battery 1 and the lithium ion battery 3 have independent battery shell structures. If the packaged battery has no internal liquid cooling and heat dissipation structure, the inner shell of the sodium ion battery 1 and the outer shell of the lithium ion battery 3 can be integrated together, and the joints of the two batteries share the same battery shell, which can reduce the material used in the shell structure and increase the energy density.

[0045] Since both the sodium ion battery 1 and the lithium ion battery 3 are circular structures, both the sodium ion battery 1 and the lithium ion battery 3 can be made using the battery winding process, which is convenient for the production of structures such as the current collecting plate. The positive and negative plates need to reserve the multi-pole ear 2 part. Both the sodium ion battery 1 and the lithium ion battery 3 can have a shell, a battery positive electrode, a battery negative electrode, a diaphragm and an electrolyte. The positive electrode sheet, diaphragm and negative electrode sheet of the lithium ion battery 3 are wound or stacked in sequence, and the electrolyte is injected to package the lithium ion battery 3. The positive electrode sheet, diaphragm and negative electrode sheet of the sodium ion battery 1 are wound or stacked in sequence, and the electrolyte is injected to package the sodium ion battery 1. If the packaged battery has no internal liquid cooling and heat dissipation structure, the winding operation is performed directly on the shell of the lithium ion battery 3, and then the shell is packaged. The positive and negative electrode sheets of the battery need to reserve the multi-pole ear 2 part before cutting. After convolution, the multi-pole ears 2 are stacked in order.

[0046] The manufacturing method of the positive electrode sheet of the sodium ion battery 1 and the lithium ion battery 3 is: the positive electrode material is mixed with the conductive agent and the binder, and then coated on the aluminum foil current collector, and then compacted after drying. The manufacturing method of the negative electrode sheet of the sodium ion battery 1 and the lithium ion battery 3 is: the negative electrode material is mixed with the conductive agent and the binder, and then coated on the copper foil current collector, and then compacted after drying. The conductive agent is carbon black or the like; the binder is polyvinylidene fluoride PVDF or the like; the positive electrode material of the lithium ion battery 3 is selected from one or more of lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium nickel oxide (LiNiO2), nickel cobalt manganese (NCM), nickel cobalt aluminum (NCA), lithium iron phosphate (LiFePO4), lithium-rich manganese-based materials, layered lithium nickel oxide, and lithium manganese oxide; the positive electrode material of the sodium ion battery 1 is selected from one or more of metal oxides, polyanion compounds, Prussian blue compounds, phosphate compounds, and Prussian white compounds; the negative electrode material of the lithium ion battery 3 and the sodium ion battery 1 is selected from one or more of natural graphite, artificial graphite, mesophase carbon microbeads, soft carbon, hard carbon, graphene, silicon-based and their composite materials.

[0047] The multi-electrode lithium-sodium composite battery of the embodiment of the present invention can adopt the following dimensions: the outer diameter of the sodium-ion battery 1 is 18mm-100mm; the outer diameter of the lithium-ion battery 3 is 15mm-90mm; the height of the sodium-ion battery 1 and the lithium-ion battery 3 are both 40mm-200mm.

[0048] The multi-pole lithium-sodium composite battery is composed of a cylindrical lithium-ion battery 3 in the center and a tubular sodium-ion battery 1 on the outside, which makes full use of the high safety and excellent low-temperature charging and discharging performance of the sodium-ion battery 1 and the high energy density of the lithium-ion battery 3. The use of the lithium-ion battery 3 ensures the high energy density of the battery. At the same time, the positive electrodes of the sodium-ion battery 1 and the lithium-ion battery 3 adopt a multi-pole structure and are welded and connected to the collector plate. Compared with the single-pole structure, the internal resistance of the battery is lower, and the heat generation during use will be significantly reduced. The sodium-ion battery 1 and the lithium-ion battery 3 are in parallel structure and can be charged and discharged independently. The sodium-ion battery 1 is used to provide temperature control to assist the lithium-ion battery 3 in energy storage, and can block the explosion of the lithium-ion battery 3 with the collector plate. The current on the sodium-ion battery 1 can be conducted to the positive terminal 4 of the lithium-ion battery 3 through the collector plate, so that the internal resistance of the composite battery is smaller, the integrity is better, and it is more stable under the action of external force. Due to the multi-pole structure design and the use of the current collecting plate, the multi-pole lithium-sodium composite battery eliminates the positive terminal 4 structure of the sodium ion battery 1, so that the battery has the advantages of small internal resistance and significantly reduced heat generation.

[0049] Therefore, the composite battery using the above structure has the characteristics of more stable structure under external force conditions, higher battery cell strength, low battery internal resistance, good low temperature adaptability, more uniform heat dissipation, less prone to explosion, and good safety.

[0050] The above multi-pole lithium-sodium composite battery has the following multiple starting modes:

[0051] 1. Sodium ion battery 1 starts first, and lithium ion battery 3 starts later. In cold weather with low temperature, sodium ion battery 1 is discharged first to heat lithium ion battery 3 before starting, so that its temperature rises and reaches the optimal working temperature. A temperature sensor is set in the battery pack, and the battery management system starts lithium ion battery 3 after reaching the optimal temperature.

[0052] 2. Sodium ion battery 1 and lithium ion battery 3 are started simultaneously. Under normal ambient temperature and without special safety environment requirements, sodium ion battery 1 and lithium ion battery 3 can be started simultaneously. Since sodium ion battery 1 and lithium ion battery 3 are in parallel structure, the working voltage of the composite battery can be increased, and it can also be applied to scenes requiring high power.

[0053] 3. Lithium-ion battery 3 is started, and sodium-ion battery 1 is not started. In some scenarios that require short-range use and rapid energy replenishment, the charging power of lithium-ion battery 3 is relatively large, and only lithium-ion battery 3 can be started to meet the needs of rapid power replenishment. In some special flammable and explosive scenarios, if the absolute safety of the battery needs to be guaranteed, only lithium-ion battery 3 can be charged and discharged, and the coating of sodium-ion battery 1 can ensure the relative safety of the lithium battery.

[0054] The above-mentioned composite battery is controlled by a battery management system (BMS). In the battery charging and discharging scenario under low temperature environment, the sodium ion battery can be started first, and the lithium ion battery can be started after reaching the optimal operating temperature of the lithium ion battery, thereby improving the battery performance at low temperature and extending the battery life. The sodium ion battery and the lithium ion battery have independent shell structures respectively, so that the battery has a strong structural strength. Since the safety of lithium ion batteries is relatively low, the sodium ion battery structure and the collector plate structure wrapped in them can prevent them from directly affecting nearby lithium batteries when they catch fire and explode.

[0055] Obviously, those skilled in the art can make various changes and modifications to the embodiments of the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A multi-electrode lithium-sodium composite battery, characterized in that: It comprises a tubular sodium ion battery, a cylindrical lithium ion battery and a current collecting plate; the sodium ion battery is coaxially installed on the outer peripheral side of the lithium ion battery; the sodium ion battery and the lithium ion battery are in parallel structure and can be charged and discharged independently; the lithium ion battery is used for energy storage and maintaining the working voltage; the sodium ion battery is used for providing temperature control to assist the lithium ion battery in energy storage and can block the explosion of the lithium ion battery; The lithium-ion battery has a positive terminal and a negative terminal; the positive electrodes of the sodium-ion battery and the lithium-ion battery both adopt a multi-electrode structure; and the current collecting plate is welded and connected to the poles of the sodium-ion battery and the lithium-ion battery.

2. The multi-electrode lithium-sodium composite battery according to claim 1, characterized in that: The top of the sodium ion battery is evenly distributed with a plurality of tabs along the circumferential direction; The outer periphery of the current collecting plate is provided with a shovel-shaped structure corresponding to the pole ears of the sodium ion battery one by one, and a boss is provided in the center; The shovel-shaped structure is welded to the corresponding pole lug; the internal cavity of the boss is larger than the positive terminal of the lithium-ion battery, is welded to the pole lug of the lithium-ion battery, and is sleeved on the positive terminal of the lithium-ion battery; The shovel-shaped structure and the boss are both provided with welding gaps for welding and connecting the pole ears.

3. The multi-electrode lithium-sodium composite battery according to claim 1, characterized in that: The sodium ion battery is in contact with the lithium ion battery via a circumferential surface; The inner outer shell of the sodium ion battery and the outer outer shell of the lithium ion battery share the same outer shell.

4. The multi-electrode lithium-sodium composite battery according to claim 1, characterized in that: A liquid cooling system is arranged between the lithium-ion battery and the sodium-ion battery.

5. The multi-electrode lithium-sodium composite battery according to claim 1, characterized in that: The sodium ion battery and the lithium ion battery are both manufactured using a battery core winding process.

6. The multi-electrode lithium-sodium composite battery according to claim 1, characterized in that: The manufacturing method of the positive electrode sheet of the sodium ion battery and the lithium ion battery is as follows: the positive electrode material is mixed with a conductive agent and a binder, and then coated on an aluminum foil current collector, and then compacted after drying; The manufacturing method of the negative electrode sheet of the sodium ion battery and the lithium ion battery is as follows: the negative electrode material is mixed with a conductive agent and a binder, and then coated on a copper foil current collector, and then compacted after drying.

7. The multi-electrode lithium-sodium composite battery according to claim 6, characterized in that: The conductive agent is carbon black; the binder is polyvinylidene fluoride PVDF; The positive electrode material of the lithium-ion battery is selected from one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, nickel cobalt manganese, nickel cobalt aluminum, lithium iron phosphate, lithium-rich manganese-based materials, layered lithium nickel oxide, and lithium manganese oxide; The positive electrode material of the sodium ion battery is selected from one or more of metal oxides, polyanion compounds, Prussian blue compounds, phosphate compounds, and Prussian white compounds; The negative electrode material of the lithium ion battery and the sodium ion battery is selected from one or more of natural graphite, artificial graphite, mesophase carbon microspheres, soft carbon, hard carbon, graphene, silicon-based and composite materials thereof.

8. The multi-electrode lithium-sodium composite battery according to any one of claims 1 to 7, characterized in that: The outer diameter of the sodium ion battery is 18 mm-100 mm; The outer diameter of the lithium-ion battery is 15 mm to 90 mm; The heights of the sodium ion battery and the lithium ion battery are both 40 mm-200 mm.

9. A current collector for a multi-electrode lithium-sodium composite battery as claimed in any one of claims 1 to 8, characterized in that: The outer periphery of the current collecting plate is provided with a shovel-shaped structure corresponding to the pole ears of the sodium ion battery one by one, and a boss is provided in the center; The shovel-shaped structure is used for welding connection with the corresponding pole lug; The inner cavity of the boss is larger than the positive terminal of the lithium-ion battery, is welded to the tab of the lithium-ion battery, and is sleeved on the positive terminal of the lithium-ion battery.

10. The collecting plate according to claim 9, characterized in that: The shovel-shaped structure and the boss are both provided with welding gaps for welding and connecting the pole ears.

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