High-energy-density sodium-lithium ion hybrid battery

Abstract

The invention belongs to the field of electrochemical energy storage, and particularly relates to a sodium ion battery. Based on the problem of low energy density of the sodium ion battery, the invention combines the advantages of low cost of the sodium ion battery and high energy density of the lithium ion battery, and designs and realizes the sodium-lithium mixed ion battery with high energy density and low cost. The battery is composed of a positive plate, a negative plate, an electrolyte and a diaphragm, a positive active material simultaneously contains sodium manganate and lithium cobalt oxide, and a negative active material simultaneously contains hard carbon (or soft carbon) and yttrium lithium titanate, so that sodium ions and a small amount of lithium ions can be simultaneously transmitted in the charging and discharging processes of the battery, and the energy density is improved compared with that of a sodium ion battery; compared with a traditional lithium ion battery, the cost is reduced, and the long cycle life is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemical energy storage, and particularly relates to a sodium-lithium ion hybrid battery. Background Art

[0002] Low-cost energy storage technology is the key to realizing the sustainable use of large-scale clean energy. Lithium-ion batteries and sodium-ion batteries have the advantages of long cycle life, high energy density, high safety, etc., and are considered competitive new electrochemical energy storage technologies. Lithium-ion batteries have problems such as high raw material costs, resource bottlenecks, and poor low-temperature performance. Although sodium-ion batteries have low raw material costs and good low-temperature performance, they usually have poor energy density and are difficult to meet the application requirements of power batteries. Therefore, there is an urgent need to develop a new type of battery that combines the performance advantages of lithium-ion batteries and sodium-ion batteries. Summary of the Invention

[0003] Based on the problems of low energy density of sodium-ion batteries and high cost of lithium-ion batteries, the present invention combines the advantages of sodium-ion batteries and lithium-ion batteries to design a sodium-lithium ion hybrid battery: taking the sodium-ion battery system as an example, on the basis of a conventional sodium-ion battery, lithium cobaltate and lithium yttrium titanate are introduced into the positive electrode and the negative electrode respectively. Lithium cobaltate has high electronic conductivity and high capacity, which can greatly improve the energy density of the battery. Lithium yttrium titanate has a lower voltage (0.5V) than lithium titanate, and can preferentially realize the deintercalation and intercalation of lithium ions during the charge and discharge process of the sodium-lithium hybrid battery. In addition, lithium yttrium titanate also has high rate performance and better electrolyte wettability than carbon-based negative electrodes, which can achieve better low-temperature performance. Specifically, the present invention is implemented as follows:

[0004] The present invention includes a high-energy density sodium-lithium ion hybrid battery, which is composed of a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charge and discharge process of the battery, sodium ions and lithium ions can be transmitted simultaneously, so that the energy density is improved compared with that of sodium-ion batteries, and the cost is reduced compared with that of traditional lithium-ion batteries.

[0005] Preferably, the positive electrode sheet includes a positive electrode current collector, positive electrode active materials, a conductive agent, and a binder, wherein the positive electrode active materials include sodium manganate and lithium cobaltate.

[0006] Preferably, the molar ratio of sodium manganate to lithium cobaltate in the positive electrode active materials of the positive electrode sheet is between 0.05:1 and 20:1, wherein the molar ratio range applied to the sodium-ion battery system is 3:1 to 20:1, preferably 5:1 to 10:1; the molar ratio range applied to the lithium-ion battery system is 0.05:1 to 0.3:1, preferably 0.1:1 to 0.25:1.

[0007] Preferably, the negative electrode sheet includes a negative electrode current collector, negative electrode active materials, a conductive agent, and a binder, wherein the negative electrode active materials contain lithium yttrium titanate and one or more of hard carbon and soft carbon.

[0008] Preferably, the molar ratio of lithium yttrium titanate to lithium cobaltate in the negative active material of the negative electrode sheet is between 1:1 and 1.5:1, and preferably 1:1 to 1.2:1.

[0009] Preferably, the loading amount of the positive active material on the surface of the positive electrode sheet is 1-50 mg / cm 2 , and preferably 10-30 mg / cm 2 .

[0010] Preferably, the electrolyte contains both sodium salt and lithium salt. The sodium salt includes one or more of NaPF6, NaOTF, NaFSI, NaTFSI, NaBF4, NaBOB, NaDFOB, and NaClO4, and preferably NaPF6; the lithium salt includes one or more of LiPF6, LiClO4, LiBF4, and LiAsF6, and preferably LiPF6 and LiClO4.

[0011] Preferably, the solvents in the electrolyte include one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), propylene carbonate (PC), ethylene carbonate (EC), ethyl methyl carbonate (EMC), and water, and preferably a mixed solvent of propylene carbonate (PC) and ethylene carbonate (EC).

[0012] Preferably, the positive current collector and the negative current collector include one or more of aluminum foil, copper foil, composite aluminum foil, composite copper foil, carbon-coated aluminum foil, carbon-coated copper foil, carbon fiber cloth, and carbon paper, and preferably aluminum foil and copper foil.

[0013] Preferably, the positive electrode conductive agent and the negative electrode conductive agent include one or more of conductive carbon black, acetylene black, hard carbon, soft carbon, graphite, carbon nanotubes, graphene, biomass pyrolysis carbon, graphdiyne, and carbon fiber, and preferably acetylene black.

[0014] The sodium-lithium hybrid positive electrode sheet or negative electrode sheet of the present invention, the sodium-lithium hybrid electrode sheet containing a small amount of lithium can be applied to various conventional sodium batteries, not limited to layered metal oxide cathodes such as sodium manganate. According to the same technical principle, this technology can also be applied to various sodium ion batteries such as sodium vanadium phosphate, Prussian blue, and sodium iron phosphate. According to the same technical principle, this technology can also be applied to the lithium ion battery system. The sodium-lithium hybrid positive electrode sheet or negative electrode sheet containing a small amount of sodium can be applied to various conventional lithium batteries, including but not limited to lithium cobaltate, lithium manganate, lithium iron phosphate, ternary batteries and other lithium ion batteries. Description of the Drawings

[0015] Figure 1 . Shows a physical photo of the battery prepared in Example 1. Detailed Embodiments

[0016] To further illustrate the content, features and actual effects of the present invention, the present invention will be described in detail below with reference to embodiments. It should be noted that the modified methods designed by the present invention are not limited to these specific embodiments. Without departing from the spirit and connotation of the design of the present invention, equivalent substitutions and modifications made by those skilled in the art on the basis of reading the content of the present invention are also within the scope of protection required by the present invention.

[0017] A sodium-lithium mixed-ion battery is prepared by a conventional method in the art. An exemplary preparation process includes: stacking a positive electrode sheet, a separator, and a negative electrode sheet, and performing subsequent processes such as electrolyte injection and encapsulation.

[0018] The battery in the embodiment of the present invention can specifically be a button battery, a cylindrical battery, a soft-pack battery, a square-shell battery, a blade battery, etc., without special limitation.

[0019] Specifically, the separator is a conventional polymer separator material and a polymer / inorganic composite separator material in the art, and has a porous structure in which the electrolyte can be adsorbed. In some preferred embodiments, the polymer separator material includes one or more of polypropylene, polyethylene, and polyimide. The specific implementation needs to select a suitable polymer separator according to the transmission of lithium ions and sodium ions.

[0020] Specifically, the electrolyte includes sodium salts, lithium salts and solvents. If organic solvents are used as solvents, the total concentration of sodium salts and lithium salts can be selected from 0.1-3M, such as 0.5M, 1.0M, 1.2M, 1.5M, and the sodium salts and lithium salts in the electrolyte are adjusted in equal proportion according to the ratio of lithium and sodium in the positive electrode material.

[0021] Specifically, in the embodiment of the invention, the positive electrode sheet is generally prepared by a coating method. A certain proportion of positive electrode active material, conductive agent, and binder are stirred evenly in a solvent to form a slurry, and then the slurry is coated on the surface of the positive electrode current collector, and dried and roll-pressed to obtain the positive electrode sheet. The negative electrode sheet can also be prepared by a coating method. The negative electrode active material, conductive agent, and binder are stirred evenly in a solvent to form a slurry, and then the slurry is coated on the surface of the negative electrode current collector, and dried and roll-pressed to obtain the negative electrode sheet.

[0022] Example 1

[0023] Sodium manganate and lithium cobaltate are mixed into a cathode active material at a molar ratio of 9:1. The cathode active material, PVDF, and acetylene black are placed in an NMP solvent at a mass ratio of 8:1:1 to make a slurry. The slurry is coated on the surface of an aluminum foil, dried, rolled, and cut to prepare a cathode sheet. Hard carbon and lithium yttrium titanate with the same molar ratio as the cathode are mixed to make an anode active material. The anode active material, sodium carboxymethyl cellulose, and acetylene black are mixed at a ratio of 8:1:1 to prepare the anode active material. The slurry is coated on the surface of an aluminum foil, dried, rolled, and cut to prepare an anode sheet. The cathode sheet, separator, and anode sheet are stacked in sequence, injected with electrolyte, and encapsulated to make a battery.

[0024] Referring to the preparation process of Example 1, Examples 2-6 and Comparative Example 1 are prepared. Except for the different compositions of the cathode active material and the anode active material in Table 1, other conditions are the same for the examples and the comparative example.

[0025] At 25 °C, the LAND-CT2001C battery test system of Blue Energy Co., Ltd. is used to conduct constant current charge and discharge tests on the batteries of Examples 1-6 and Comparative Example 1. The charge and discharge specific capacities of each cycle at a 0.5C rate are recorded, and the battery energy density and cycle performance are calculated. The recorded results are shown in the following table:

[0026] Table 1

[0027]

Claims

1. A high energy density sodium-lithium ion hybrid battery, characterized in that: The sodium-lithium ion hybrid battery is composed of a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charge and discharge process of the battery, sodium ions and lithium ions can be transmitted simultaneously, thereby improving the energy density compared to sodium ion batteries and reducing costs compared to traditional lithium ion batteries.

2. The high-energy-density sodium-lithium ion hybrid battery according to claim 1, wherein The positive electrode sheet includes a positive electrode current collector, positive electrode active materials, a conductive agent, and a binder, wherein the positive electrode active materials simultaneously include sodium manganate and lithium cobaltate.

3. The high-energy density sodium-lithium ion hybrid battery according to claim 1, wherein In the positive electrode sheet, the molar ratio of sodium manganate to lithium cobaltate in the positive electrode active materials is between 0.05:1 and 20:

1. Among them, the preferred molar ratio range for application in the sodium ion battery system is between 3:1 and 20:1, and the preferred molar ratio range for the lithium ion battery system is between 0.05:1 and 0.3:

1.

4. The high-energy-density sodium-lithium ion hybrid battery according to claim 1, characterized in that, The negative electrode sheet includes a negative electrode current collector, negative electrode active materials, a conductive agent, and a binder, wherein the negative electrode active materials contain lithium yttrium titanate and one or more of hard carbon and soft carbon.

5. The high-energy density sodium-lithium ion hybrid battery according to claim 1, characterized in that, In the negative electrode sheet, the molar ratio of lithium yttrium titanate to lithium cobaltate in the negative electrode active materials is between 1:1 and 1.5:

1.

6. The high-energy density sodium-lithium ion hybrid battery according to claim 1, characterized in that, The loading amount of the positive electrode active material on the surface of the positive electrode sheet is 1 to 50 mg / cm 2 .

7. The high-energy density sodium-lithium ion hybrid battery according to claim 1, characterized in that The electrolyte simultaneously contains a sodium salt and a lithium salt, wherein the sodium salt includes one or more of NaPF6, NaOTF, NaFSI, NaTFSI, NaBF4, NaBOB, NaDFOB, and NaClO4, and the lithium salt includes one or more of LiPF6, LiClO4, LiBF4, and LiAsF6.

8. The high-energy density sodium-lithium ion hybrid battery according to claim 1, wherein The solvent in the electrolyte includes one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), propylene carbonate (PC), ethylene carbonate (EC), ethyl methyl carbonate (EMC), and water.

9. The high-energy-density sodium-lithium ion hybrid battery according to claim 1, wherein The positive electrode current collector and the negative electrode current collector include one or more of aluminum foil, copper foil, composite aluminum foil, composite copper foil, carbon-coated aluminum foil, carbon-coated copper foil, carbon fiber cloth, and carbon paper.

10. The high-energy-density sodium-lithium ion hybrid battery according to claim 1, characterized in that, The positive electrode conductive agent and the negative electrode conductive agent include one or more of conductive carbon black, acetylene black, hard carbon, soft carbon, graphite, carbon nanotubes, graphene, biomass pyrolysis carbon, graphdiyne, and carbon fiber.

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