A lithium-sodium hybrid ion battery and battery pack

Abstract

This invention discloses a lithium-sodium hybrid ion battery and battery pack. The lithium-sodium hybrid ion battery includes: a positive electrode, a negative electrode, an electrolyte, and a lithium-ion exchanger. The positive electrode contains a sodium-ion positive electrode material; the negative electrode contains a lithium-ion negative electrode material; the electrolyte is a lithium-ion battery electrolyte; the lithium-ion exchanger is disposed on or in at least one of the positive electrode, the negative electrode, and the separator, and is used to replenish lithium ions in the electrolyte during battery charging and discharging. By incorporating a lithium-ion exchanger to replenish lithium ions in the electrolyte during charging and discharging, the lithium intercalation capacity of the negative electrode and the overall capacity of the cell are improved, solving the problem that the actual capacity of commercial lithium-sodium hybrid ion batteries is far lower than the design value due to insufficient lithium-ion supply in the electrolyte.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a lithium-sodium hybrid ion battery and battery pack. Background Technology

[0002] Lithium-ion batteries have become the mainstream in the current battery market due to their advantages such as high energy density, long cycle life, and low self-discharge rate, and are widely used in consumer electronics, electric vehicles, and energy storage. However, the distribution of lithium resources on Earth is extremely uneven, with approximately 57% concentrated in South America, while domestic lithium resources account for only 9%, posing a significant security risk to resource supply. Therefore, countries are actively developing new battery technologies. Sodium resources are widely distributed, abundant, and have a relatively simple refining process, making sodium-ion batteries one of the most promising alternatives; however, their low energy density and high cost remain unresolved.

[0003] Against this backdrop, researchers have proposed a lithium-sodium hybrid ion battery scheme, aiming to combine the advantages of sodium-ion and lithium-ion batteries. This scheme uses sodium-ion battery cathode materials (such as Na3V2(PO4)2F3, Na3V2(PO4)2O2F, Na3V2(PO4)3, etc.) as the cathode, and lithium-ion battery anode materials (such as graphite, mesophase carbon microspheres, etc.) as the anode, using a lithium-ion battery electrolyte. Its working principle is based on the Li / Na intercalation / deintercalation reaction at the cathode and the lithium-ion intercalation / deintercalation reaction at the anode. Compared to sodium-ion batteries, this system has a lower anode potential, a higher overall voltage platform, and improved energy density. Furthermore, the cost of graphite anode and lithium electrolyte is lower than that of materials used in sodium-ion batteries. Compared to lithium-ion batteries, its cathode material is cheaper and exhibits superior low-temperature performance.

[0004] However, during the commercial product verification process, even with the maximum allowable electrolyte injection volume for cell production, the actual cell capacity was still far below the design value. The reason for this is that commercial cells have limited internal electrolyte injection space, and the lithium ions required in the hybrid battery system rely entirely on the lithium salt in the electrolyte. Limited by the lithium salt concentration, the total amount of lithium ions provided by the electrolyte is insufficient to match the lithium intercalation capacity requirements of the negative electrode. It is worth noting that the normal capacity achieved in related research reports is due to the use of a coin cell structure, where the injected electrolyte volume is typically much higher than in commercial lithium-ion battery products. Therefore, the lithium ions provided by the electrolyte are sufficient to meet the negative electrode capacity requirements. This crucial factor in the productization process has been generally overlooked in existing research. Summary of the Invention

[0005] The purpose of this invention is to provide a lithium-sodium hybrid ion battery and battery pack. By setting a lithium-ion exchanger to replenish lithium ions in the electrolyte during charging and discharging, the lithium intercalation capacity of the negative electrode and the overall capacity of the cell are improved, solving the problem that the actual capacity of commercial lithium-sodium hybrid ion batteries is far lower than the design value due to insufficient lithium ion supply in the electrolyte.

[0006] To address the aforementioned technical problems, a first aspect of the present invention provides a lithium-sodium hybrid ion battery, comprising: Positive electrode, wherein the positive electrode comprises a sodium ion positive electrode material; Negative electrode, wherein the negative electrode comprises a lithium-ion negative electrode material; Electrolyte, wherein the electrolyte is an electrolyte for lithium-ion batteries; and A lithium-ion exchanger is disposed on or in at least one of the positive electrode, the negative electrode, and the separator, for replenishing lithium ions in the electrolyte during battery charging and discharging.

[0007] Furthermore, the lithium-ion exchanger includes: Li₂CO₃, LiCl, LiNO₃, and Li₃Zr₂Si₂PO₄. 12 Na 1+x Mn x / 2Zr 2-x / 2 At least one of (PO4)3 and lithium carboxymethyl cellulose; Where 0 < x ≤ 2.

[0008] Furthermore, the formula for calculating the amount of lithium-ion exchanger added is as follows: ; in, The unit area mass of the lithium-ion exchanger is expressed in g / m². 2 , Let n be the molar mass of the lithium-ion exchanger, and n be the number of lithium ions in the molecular formula of the lithium-ion exchanger. This represents the sum of the number of lithium ions in all exchangers corresponding to all unit electrode areas. It is a reversible specific capacity at the negative electrode. The design parameters are the unit area mass of the negative electrode active material. The value range is 1.0 to 1.2. F It is Faraday's constant. This refers to the total volume of electrolyte injected. The sum of the lithium salt molar concentrations injected into the electrolyte, and S is the total area of ​​the negative electrode film. The design parameters The calculation formula is: ; in, This represents the mass per unit area of ​​the positive electrode active material. It represents the reversible specific capacity of the positive electrode.

[0009] Furthermore, the lithium-ion exchanger is mixed with the sodium-ion cathode material slurry and then coated onto the battery cathode current collector; The lithium-ion exchanger is mixed with the lithium-ion anode material slurry and then coated onto the battery anode current collector; and / or The lithium-ion exchanger is coated on one or both sides of the battery separator.

[0010] Furthermore, the sodium ion cathode material includes at least one of layered transition metal oxides, polyanionic compounds, and Prussian blue analogues.

[0011] Furthermore, the layered transition metal oxide is Na. x MO2; Where 0 < x ≤ 1, M includes at least one of Fe, Mn, Ni, Co and Cu.

[0012] Furthermore, the polyanionic compound is Na. x M y (XO z ) n F m ; Wherein, 0 < x ≤ 3, 0 < y ≤ 2, 0 < z ≤ 4, 0 < n ≤ 3, 0 ≤ m ≤ 3, M includes at least one of Fe, V and Mn, X includes at least one of P, S and Si, and F is a doped anion.

[0013] Furthermore, the Prussian blue analogue includes: Na x M[Fe(CN)6] 1-y ·□ y ·nH2O; Where 0 < x ≤ 2, 0 < y < 1, □ represents a lattice vacancy, n represents the number of water molecules, and M includes at least one of Fe, Mn, Ni, and Co.

[0014] Furthermore, the lithium-ion anode material includes at least one of artificial graphite, natural graphite, silicon-carbon materials, and mesophase carbon microspheres.

[0015] Accordingly, a second aspect of the present invention provides a battery pack comprising the aforementioned plurality of lithium-sodium hybrid ion batteries connected in series and / or in parallel.

[0016] The above-described technical solutions of the embodiments of the present invention have the following beneficial technical effects: 1. By introducing lithium-ion exchangers into the positive electrode, negative electrode, or separator of the battery, during charging and discharging, sodium ions released from the positive electrode undergo ion exchange with lithium ions in the exchanger, allowing lithium ions to continuously enter the electrolyte and embed into the negative electrode. This overcomes the limitation of the electrolyte's own lithium salt concentration on the lithium embedding capacity, significantly increasing the total lithium embedding in the negative electrode, and enabling the actual capacity of the cell to reach more than 95% of the design capacity. This effectively solves the key problem of commercial lithium-sodium hybrid ion batteries where the capacity is far below the design value due to insufficient lithium ion supply in the electrolyte.

[0017] 2. By establishing a quantitative relationship between the amount of lithium-ion exchanger added and the negative electrode capacity requirement and the total amount of lithium ions in the electrolyte, the number of moles of supplementary lithium ions provided by the exchanger is precisely matched with the lithium ion gap required for lithium intercalation in the negative electrode. At the same time, by designing the parameter k to constrain the capacity matching relationship between the positive and negative electrode active materials, it is ensured that the amount of exchanger used is neither excessive and wasteful nor insufficient and affects the capacity performance. This achieves precise control of cell capacity from the material design stage, improving the consistency and reliability of product design.

[0018] 3. By designing lithium-ion exchangers to be incorporated into positive electrode slurries, negative electrode slurries, or coated on the surface of separators in multiple ways, this technical solution can be flexibly adapted to existing lithium-ion battery production processes. It can achieve the preparation of hybrid battery systems without major modifications to existing production lines, thereby reducing the process threshold and equipment investment costs for industrialization. At the same time, the combined application of multiple addition methods can further optimize the uniformity of the exchanger distribution inside the cell, ensuring battery cycle performance and safety performance. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of the invention.

[0020] A first aspect of this invention provides a lithium-sodium hybrid ion battery, comprising: a positive electrode, a negative electrode, an electrolyte, and a lithium-ion exchanger. The positive electrode comprises a sodium-ion positive electrode material; the negative electrode comprises a lithium-ion negative electrode material; the electrolyte is a lithium-ion battery electrolyte; and the lithium-ion exchanger is disposed on or in at least one of the positive electrode, the negative electrode, and a separator, for replenishing lithium ions in the electrolyte during battery charging and discharging.

[0021] The lithium-sodium hybrid ion battery uses sodium-ion positive electrode material and lithium-ion negative electrode material. The electrolyte is a lithium-ion battery electrolyte, and a lithium-ion exchanger is incorporated into the positive electrode, negative electrode, or separator. During charging and discharging, sodium ion insertion / extraction occurs at the positive electrode, and lithium ion insertion / extraction occurs at the negative electrode. Due to the large radius of sodium ions, they are difficult to insert into the negative electrode material structure, and the lithium ions required for negative electrode lithium insertion are entirely provided by the electrolyte. However, in commercially available cells, limited by the electrolyte injection space, the concentration and total amount of lithium salts in the electrolyte cannot meet the capacity requirements of the negative electrode, resulting in the actual cell capacity being far lower than the design value. Therefore, a lithium-ion exchanger is introduced inside the battery. During the electrochemical process, the exchanger exchanges ions with the sodium ions extracted from the positive electrode, continuously releasing lithium ions into the electrolyte, thereby compensating for the insufficient lithium ions in the electrolyte and ensuring that the negative electrode receives a sufficient supply of lithium ions to match its lithium insertion capacity.

[0022] Compared to existing hybrid battery solutions that rely solely on electrolytes to provide lithium ions, the innovation of this invention lies in recognizing the fundamental difference in electrolyte volume between commercial products and coin cells. Based on this, it proposes a technical approach of adding a lithium-ion exchanger inside the battery as a supplementary lithium source. This exchanger can be flexibly distributed in the positive electrode, negative electrode, or separator, coupling the sodium ion removal process with the lithium ion replenishment process through an ion exchange mechanism. This overcomes the rigid constraint of the total amount of lithium ions in the electrolyte on the negative electrode capacity. Simultaneously, the amount of exchanger added is matched with the positive and negative electrode capacities and electrolyte parameters through a quantitative formula, enabling the design to move from empirical to precise, laying the foundation for the mass production and reproducibility of the technical solution.

[0023] Based on the aforementioned additives, this invention effectively improves the efficiency of cell capacity utilization, achieving an actual capacity of over 97% of the designed capacity, thus solving the problem of significant capacity loss in commercial lithium-sodium hybrid batteries due to insufficient lithium-ion supply. Through the constraint of the dosage formula, the amount of exchange agent added can be precisely controlled, avoiding both excessive addition affecting energy density and insufficient addition leading to unsatisfactory lithium replenishment. Furthermore, the design of multiple addition methods ensures process compatibility, adapting to existing lithium-ion battery production processes and providing a feasible path for the industrial application of lithium-sodium hybrid battery technology.

[0024] Specifically, lithium-ion exchangers include: Li₂CO₃, LiCl, LiNO₃, and Li₃Zr₂Si₂PO₄. 12 Na 1+x Mn x / 2 Zr 2-x / 2 At least one of (PO4)3 and lithium carboxymethyl cellulose; wherein 0 < x ≤ 2.

[0025] Lithium-ion exchangers can be selected from Li₂CO₃, LiCl, LiNO₃, Li₃Zr₂Si₂PO₄12 Na 1+x Mn x / 2 Zr 2-x / 2 (PO4)3 (where 0 < x ≤ 2) and at least one of lithium carboxymethyl cellulose. All of the above substances possess the ability to release lithium ions under electrochemical conditions. Li2CO3, LiCl, and LiNO3 are common lithium salts that can dissociate into lithium ions in the electrolyte; Li3Zr2Si2PO4... 12 It belongs to lithium-ion conductor materials and has both ion conduction and ion exchange functions; Na 1+x Mn x / 2 Zr 2-x / 2 (PO4)3 is a sodium ion conductor, and in the battery system, lithium ions can be replenished through sodium-lithium ion exchange. Lithium carboxymethyl cellulose, as a polymer lithium salt, can be used as a binder in electrode forming and as a supplementary lithium source. During the preparation process, the above substances can be dispersed in the positive electrode slurry, negative electrode slurry, or coated on the surface of the separator, and come into contact with the electrolyte and participate in the ion exchange reaction during battery charging and discharging.

[0026] Compared to traditional solutions that rely solely on electrolyte lithium salts for lithium ion supply, this invention utilizes a variety of materials, including inorganic lithium salts, lithium-ion conductors, sodium-ion conductors, and polymer lithium salts, to create a diversified lithium source system. Sodium-ion conductors, while not containing lithium themselves, indirectly supplement lithium ions through ion exchange with sodium ions extracted from the electrolyte or cathode, thus expanding the range of exchanger options. The introduction of lithium carboxymethyl cellulose combines the functions of a binder and lithium supplementation, achieving additional lithium ion supply without increasing process complexity. This diverse selection enhances the technical solution's process adaptability, allowing for flexible selection of appropriate exchanger types based on different electrode systems and preparation processes. Inorganic lithium salts are low-cost and widely available, suitable for cost-sensitive large-scale production; lithium-ion conductors and sodium-ion conductors possess high ionic conductivity and electrochemical stability, suitable for applications requiring high rate performance and cycle life; lithium carboxymethyl cellulose simplifies the process while providing lithium supplementation.

[0027] Furthermore, the formula for calculating the amount of lithium-ion exchanger added is as follows: ; (1) in, This refers to the mass per unit area of ​​a certain exchanger, expressed in g / m². 2 ; The molar mass of the exchanger is expressed in g / mol; n is the number of lithium ions in the molecular formula of the exchanger. This represents the sum of the number of lithium ions in all exchangers corresponding to all unit electrode areas, expressed in mol / m². 2 ; The reversible specific capacity of the negative electrode is expressed in mAh / g. This refers to the mass per unit area of ​​the negative electrode active material, expressed in g / m². 2 k is the design parameter, ranging from 1.0 to 1.2; F is the Faraday constant, in C / mol. The total volume of electrolyte injected is expressed in liters (L). S represents the sum of the molar concentrations of lithium salts injected into the electrolyte, in mol / L; S represents the total area of ​​the negative electrode film, in m². 2 .

[0028] Design parameters The calculation formula is: ; (2) in, This represents the mass per unit area of ​​the positive electrode active material. It represents the reversible specific capacity of the positive electrode.

[0029] This invention further defines the calculation formula for the amount of lithium-ion exchanger added. The left side of the formula represents the sum of the number of lithium ions that all lithium-ion exchangers can provide per unit electrode area, and the first term on the right side represents the total number of lithium ions required for lithium intercalation at the negative electrode per unit electrode area (based on the reversible specific capacity of the negative electrode). Mass per unit area of ​​negative electrode active material The second item on the right represents the number of lithium ions that the electrolyte itself can provide per unit electrode area (determined by the total volume of the electrolyte). The sum of the molar concentrations of lithium salts The formula is calculated from the total area S of the negative electrode film. Essentially, it determines the amount of lithium ions that need to be supplemented by the lithium ion exchanger by balancing the difference between the total amount of lithium ions required for lithium intercalation in the negative electrode and the total amount of lithium ions that the electrolyte itself can provide. This allows for the quantitative design of the amount of exchanger used. The design parameter k ranges from 1.0 to 1.2 and is used to adjust the capacity matching margin between the positive and negative electrodes to ensure that the battery can perform its capacity under actual working conditions.

[0030] Compared to existing technologies that rely solely on experience to add electrolyte or excessive electrolyte injection in coin cells, this invention innovates by establishing a quantitative relationship between the amount of lithium-ion exchanger and battery design parameters. Existing hybrid battery solutions typically ignore the engineering realities of limited electrolyte injection space and insufficient total lithium-ion content in commercial cells, resulting in production capacities far below expectations. This invention, by introducing this calculation formula, precisely matches the difference between the number of lithium-ion moles added to the exchanger and the negative electrode capacity requirements and the electrolyte lithium-ion supply. This makes the amount of exchanger no longer an empirical "appropriate amount to add," but a calculable and verifiable quantitative indicator based on the actual battery design parameters. The introduction of the design parameter k further considers the engineering margin of positive and negative electrode capacity matching, making this invention more practical and reliable. Based on the above-mentioned quantitative design method, this invention ensures that the lithium intercalation capacity requirement of the negative electrode is fully met by accurately calculating the amount of lithium ions replenished by the exchanger. The actual capacity of the cell can reach more than 97% of the design capacity, fundamentally solving the problem of insufficient capacity utilization in commercial lithium-sodium hybrid batteries. At the same time, this calculation method incorporates multiple variables such as electrolyte injection volume, lithium salt concentration, negative electrode capacity, and exchanger type into a unified design framework, making different design schemes comparable and reproducible, and providing a theoretical basis for the standardized design of products. In addition, by controlling the capacity matching margin of the positive and negative electrodes by the design parameter k, a reasonable capacity redundancy can be reserved in the design stage, taking into account both the initial charge and discharge efficiency and long-term cycle stability of the battery. This invention achieves the capacity target while taking into account the comprehensive performance of the product.

[0031] In one specific embodiment of the present invention, the lithium ion exchanger is added in at least the following three ways.

[0032] The first method involves mixing a slurry of lithium-ion exchanger and sodium-ion cathode material, and then coating it onto the positive electrode current collector of the battery. Specifically, during the preparation of the cathode slurry, the lithium-ion exchanger, sodium-ion cathode material, conductive agent, binder, and solvent are mixed in a predetermined ratio and dispersed evenly to form a cathode slurry. This slurry is then uniformly coated onto the surface of the cathode current collector (such as carbon-coated aluminum foil), and then dried and cold-pressed to form the cathode sheet. In this method, the lithium-ion exchanger is uniformly distributed in the positive electrode active material layer. During the first charge of the battery, the sodium ions released from the positive electrode undergo ion exchange with the adjacent exchanger, and the lithium ions released by the exchanger immediately enter the electrolyte and migrate to the negative electrode to participate in the lithium intercalation reaction, thereby achieving in-situ replenishment of lithium ions.

[0033] The second method involves mixing a lithium-ion exchanger with a slurry of lithium-ion anode material and then coating it onto the battery's anode current collector. Specifically, during the anode slurry preparation process, the lithium-ion exchanger is uniformly mixed with the lithium-ion anode material (such as graphite or silicon-carbon materials), a conductive agent, a binder, and a solvent to form a negative electrode slurry. This slurry is then coated onto the surface of the anode current collector (such as copper foil), dried, and cold-pressed to form the anode sheet. In this method, the lithium-ion exchanger is uniformly distributed within the anode active material layer. When the battery is charged, as lithium ions in the electrolyte embed into the anode, lithium ions in the exchanger can directly or indirectly replenish the electrolyte, forming an ion exchange pathway with the sodium ions released from the cathode, thus continuously supplying lithium ions to the anode.

[0034] The third method involves directly coating the lithium-ion exchanger onto one or both sides of the battery separator. Specifically, the lithium-ion exchanger is mixed with an appropriate amount of binder and solvent to form a coating slurry. This slurry is then uniformly coated onto one or both sides of the separator substrate using a coating process. After drying, a composite separator with a lithium-ion exchange coating is formed. During battery assembly, this composite separator is placed between the positive and negative electrode plates, with the coating in direct contact with the electrode surfaces. When the battery is charged and discharged, the lithium-ion exchanger in the separator coating comes into full contact with the electrolyte. Sodium ions released from the positive electrode migrate through the electrolyte to the separator surface and exchange with the exchanger. The released lithium ions then enter the electrolyte and participate in the lithium intercalation reaction at the negative electrode. This method decouples the exchanger from the electrode preparation process, avoiding the potential influence of the exchanger on the electrode slurry system, and also facilitates independent control of the type and amount of exchanger.

[0035] The above three methods can be selected individually or used in any combination according to actual process requirements to achieve optimized distribution of lithium-ion exchangers inside the battery cell.

[0036] Specifically, sodium ion cathode materials include at least one of layered transition metal oxides, polyanionic compounds, and Prussian blue analogues.

[0037] Furthermore, the layered transition metal oxide is Na. xMO2; where 0 < x ≤ 1, and M includes at least one of Fe, Mn, Ni, Co, and Cu. This type of material has a typical two-dimensional layered structure, with sodium ions located between the transition metal oxide layers, allowing for reversible insertion and extraction of sodium ions during charge and discharge. Due to the wide ion migration channels provided by the layered structure, this type of material typically exhibits high reversible capacity and good rate performance. In the lithium-sodium hybrid battery system of this invention, the layered transition metal oxide cathode is used in conjunction with a lithium-ion exchanger. Sodium ions extracted from the cathode undergo ion exchange with the exchanger, and the released lithium ions replenish the electrolyte, thereby ensuring that the lithium insertion capacity requirement of the anode is met. Simultaneously, this type of material has a relatively low cost, which helps reduce the overall manufacturing cost of the battery.

[0038] Furthermore, the polyanionic compound is Na x M y (XO z ) n F m Wherein, 0 < x ≤ 3, 0 < y ≤ 2, 0 < z ≤ 4, 0 < n ≤ 3, 0 ≤ m ≤ 3, M includes at least one of Fe, V, and Mn, X includes at least one of P, S, and Si, and F is a doped anion. This type of material forms a three-dimensional framework structure with a tetrahedral or octahedral anionic skeleton linked by strong covalent bonds, exhibiting high structural stability and excellent thermal stability. Simultaneously, the inductive effect of the polyanionic units can regulate the redox potential of the transition metal, resulting in a high average operating voltage. In the hybrid battery system of this invention, the polyanionic compound cathode shows minimal changes in the sodium ion insertion / extraction structure during charging and discharging, exhibits a long cycle life, and demonstrates good compatibility with lithium-ion exchangers and lithium-ion battery electrolytes, making it particularly suitable for applications requiring high safety and cycle life.

[0039] Furthermore, Prussian blue analogues include: Na x M[Fe(CN)6] 1-y ·□ y ·nH₂O; where 0<x≤2, 0<y<1, □ represents lattice vacancies, n represents the number of water molecules, and M includes at least one of Fe, Mn, Ni, and Co. This type of material possesses an open three-dimensional framework structure, with large three-dimensional channels formed by the alternating connection of transition metal ions and cyanide ions, providing favorable conditions for the rapid migration of sodium ions, thus enabling it to possess excellent rate performance and high specific capacity. In the lithium-sodium hybrid battery system of this invention, the Prussian blue analog cathode can achieve rapid insertion and extraction of sodium ions. When working synergistically with the lithium-ion exchanger, the rapid release of sodium ions helps to promptly trigger the ion exchange reaction of the exchanger, ensuring continuous replenishment of lithium ions, thereby balancing high power output and capacity utilization efficiency of the battery, making it suitable for applications with high rate performance requirements.

[0040] Specifically, lithium-ion anode materials include at least one of the following: artificial graphite, natural graphite, silicon-carbon materials, and mesophase carbon microspheres.

[0041] The above-described lithium-sodium ion hybrid battery will be further explained and illustrated below with several embodiments.

[0042] Example 1 This embodiment provides a method for preparing a lithium-sodium hybrid ion battery, including the following steps: Positive electrode preparation: Na 0.75 Cu 0.1 Fe 0.1 Mn 0.8 O2 (reversible specific capacity of 115 mAh / g, full voltage range of 4.35-2.0V), LiNO3, conductive carbon black, carbon nanotube slurry (4wt% solid content), dispersant, polyvinylidene fluoride, and N-methylpyrrolidone were uniformly dispersed in a high-efficiency disperser at a mass ratio of 76.72:20.74:0.55:7.93:0.08:1.59:56 to obtain a positive electrode slurry. This slurry was then uniformly coated on both sides of carbon-coated aluminum foil (positive electrode current collector, substrate thickness of 13μm, surface coated with a 1μm thick carbon layer). After drying, cold pressing, and die-cutting, a positive electrode sheet with a porosity of approximately 25% was obtained. The positive electrode sheet film dimensions were 341.3 × 82.6 mm (length × width, excluding tabs), and the single-sided coating areal density was 257.4 g / m². 2 ; Negative electrode preparation: Graphite (reversible specific capacity of 353 mAh / g), conductive carbon black, sodium carboxymethyl cellulose, styrene-butadiene rubber emulsion (containing 40% styrene-butadiene rubber), and deionized water were uniformly dispersed in a vacuum double planetary mixer at a mass ratio of 96:0.9:1.3:4.5:100 to obtain a negative electrode slurry; the value of k in formula (2) is 1.13, and the single-sided surface density of the negative electrode after cold pressing is calculated to be 75.72 g / m² according to formula (2). 2 After considering the negative electrode rolling elongation, it is calculated to be 76.1 g / m 2 The areal density is coated on copper foil (negative electrode current collector, substrate thickness is 5μm), and after drying, cold pressing and die cutting, a negative electrode sheet with a porosity of about 27% is obtained. The negative electrode sheet film surface size is 344.3×85.1 (length×width, mm, excluding tabs).

[0043] Battery assembly: A 12 μm thick separator is placed between the positive and negative electrode sheets, and a bare cell is formed by stacking and hot pressing. The positive and negative electrodes have 38 and 39 stacked layers, respectively. The tabs are welded to the top cover terminals via connecting pieces, and then a square aluminum shell is installed. After welding the top cover to the aluminum shell, a dry cell is obtained. After baking to remove water, the water content is reduced to less than 250 ppm. 132g of electrolyte is injected, and then the cell undergoes sealing, settling, formation, secondary electrolyte injection (33g), degassing and sealing, and capacity testing to obtain a square aluminum shell battery. The electrolyte is composed of lithium salt LiPF6, ethylene carbonate (EC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC). The volume ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC) is 30:66:1:3. The concentration of LiPF6 in the electrolyte is 1.2 mol / L, and the total volume of injected electrolyte is 138.7 ml.

[0044] The above design, after verification, satisfies formulas (1) and (2), where =353 mAh / g, =75.72×2×0.96=145.4 g / m 2 k=1.13 =0.1387 L, =1.2 mol / L, S=344.3×85.1×39×10 -6 =1.143 m 2 , =115 mAh / g, =257.4×0.7672×2=394.92 g / m 2 , =259.8 × 0.2148 × 2 = 111.6 g / m 2 , =68.95 g / mol, since LiNO3 is only added as a lithium-ion exchanger in the positive electrode of the entire system, therefore =1.62 mol / m 2 .

[0045] The final capacity of the battery cell (25℃, 0.33C, 2.0-4.35V voltage range) is 47.5 Ah. After verification and calculation, the active material specific capacity reaches 112.4 mAh / g, which is 97.7% of the expected capacity.

[0046] Example 2 This embodiment provides a method for preparing a lithium-sodium hybrid ion battery, including the following steps: Positive electrode preparation: Na 0.75 Cu 0.1 Fe 0.1 Mn 0.8 O2 (reversible specific capacity of 115 mAh / g, full voltage range of 4.35-2.0V), Li2CO3, conductive carbon black, carbon nanotube slurry (4wt% solid content), dispersant, polyvinylidene fluoride, and N-methylpyrrolidone were uniformly dispersed in a high-efficiency disperser at a mass ratio of 88.77:8.29:0.64:9.17:0.09:1.83:56 to obtain a positive electrode slurry. This slurry was then uniformly coated on both sides of carbon-coated aluminum foil (positive electrode current collector, substrate thickness of 13μm, surface coated with a 1μm thick carbon layer). After drying, cold pressing, and die-cutting, a positive electrode sheet with a porosity of approximately 25% was obtained. The positive electrode sheet film dimensions were 341.3 × 82.6 mm (length × width, excluding tabs), and the single-sided coating areal density was 231.7 g / m². 2 ; Negative electrode preparation: Graphite (reversible specific capacity of 353 mAh / g), Li2CO3, conductive carbon black, sodium carboxymethyl cellulose, styrene-butadiene rubber emulsion (containing 40% styrene-butadiene rubber), and deionized water were uniformly dispersed in a vacuum double planetary mixer at a mass ratio of 84.81:11.66:0.80:1.15:3.98:100 to obtain a negative electrode slurry; the value of k in formula (2) is 1.085, and the single-sided surface density of the negative electrode after cold pressing is calculated to be 85.72 g / m² according to formula (2). 2 After considering the elongation rate of the negative electrode roll, it is calculated to be 86.2 g / m. 2 The areal density is coated on copper foil (negative electrode current collector, substrate thickness is 5μm), and after drying, cold pressing and die cutting, a negative electrode sheet with a porosity of about 27% is obtained. The negative electrode sheet film surface size is 344.3×85.1 (length×width, mm, excluding tabs).

[0047] Battery assembly: A single-sided coating of Li3Zr2Si2PO4 is applied. 12 A 14 μm thick separator is placed between the positive and negative electrodes, Li3Zr2Si2PO 12 The coating surface density is 6 g / m 2Bare cells are manufactured by lamination and hot pressing, with the positive and negative electrodes having 38 and 39 lamination layers, respectively. The tabs are welded to the top cover terminals via connecting pieces, and then a square aluminum shell is installed. After welding the top cover to the aluminum shell, a dry cell is obtained. After baking to remove water, the water content is reduced to less than 250 ppm. 132g of electrolyte is injected, and then the cell undergoes sealing, settling, formation, secondary electrolyte injection (33g), degassing and sealing, and capacity testing to obtain a square aluminum shell battery. The electrolyte is composed of lithium salt LiPF6, ethylene carbonate (EC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC). The volume ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC) is 30:66:1:3. The concentration of LiPF6 in the electrolyte is 1.2 mol / L, and the total volume of injected electrolyte is 138.7 ml.

[0048] The above design, after verification, satisfies formulas (1) and (2), where =353 mAh / g, =85.72×0.8481×2=145.4 g / m 2 k=1.085 =0.1387 L, =1.2 mol / L, S=344.3×85.1×39×10 -6 =1.143 m 2 , =115 mAh / g, =231.7×0.8877×2=411.36 g / m 2 , =(231.7×0.0829+85.72×0.1166)×2=58.4 g / m 2 , =73.89 g / mol =6 g / m 2 , =482.41 g / mol ≈1.62 mol / m 2 .

[0049] The final average capacity of the battery cells (25℃, 0.33C, 2.0-4.35V voltage range) was 48.2 Ah. After verification and calculation, the active material specific capacity reached 114 mAh / g, achieving 99.1% of the expected capacity.

[0050] Comparative Example 1 Comparative Example 1 provides a method for preparing a lithium-sodium hybrid ion battery, comprising the following steps: Positive electrode preparation: Na 0.75 Cu 0.1 Fe 0.1 Mn 0.8 O2 (reversible specific capacity of 115 mAh / g, full voltage range of 4.35-2.0V), conductive carbon black, carbon nanotube slurry (4wt% solids content), dispersant, polyvinylidene fluoride, and N-methylpyrrolidone were uniformly dispersed in a high-efficiency disperser at a mass ratio of 96.8:0.7:0.4:0.1:2:56 to obtain a positive electrode slurry. This slurry was then uniformly coated on both sides of carbon-coated aluminum foil (positive electrode current collector, substrate thickness of 13μm, surface coated with a 1μm thick carbon layer). After drying, cold pressing, and die-cutting, a positive electrode sheet with a porosity of approximately 25% was obtained. The positive electrode sheet film dimensions were 341.3 × 82.6 mm (length × width, excluding tabs), and the single-sided coating areal density was 204 g / m³. 2 ; Negative electrode preparation: Graphite (reversible specific capacity of 353 mAh / g), conductive carbon black, sodium carboxymethyl cellulose, styrene-butadiene rubber emulsion (containing 40% styrene-butadiene rubber), and deionized water were uniformly dispersed in a vacuum double planetary mixer at a mass ratio of 96:0.9:1.3:4.5:100 to obtain a negative electrode slurry; the value of k in formula (2) is 1.13, and the single-sided surface density of the negative electrode after cold pressing is calculated to be 75.72 g / m² according to formula (2). 2 After considering the negative electrode rolling elongation, it is calculated to be 76.1 g / m 2 The areal density is coated on copper foil (negative electrode current collector, substrate thickness is 5μm), and after drying, cold pressing and die cutting, a negative electrode sheet with a porosity of about 27% is obtained. The negative electrode sheet film surface size is 344.3×85.1 (length×width, mm, excluding tabs).

[0051] Battery assembly: A separator with a single-sided thickness of 12 μm is placed between the positive electrode and the negative electrode, and a bare cell is formed by stacking and hot pressing. The positive electrode and the negative electrode have 38 and 39 stacked layers, respectively. The tabs are welded to the top cover terminals via connecting pieces, and then a square aluminum shell is installed. After welding the top cover to the aluminum shell, a dry cell is obtained. After baking to remove water, the water content is reduced to less than 250 ppm. 132g of electrolyte is injected, and then the cell undergoes sealing, settling, formation, secondary electrolyte injection (33g), degassing and sealing, and capacity testing to obtain a square aluminum shell battery. The electrolyte is composed of lithium salt LiPF6, ethylene carbonate (EC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC). The volume ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC) is 30:66:1:3. The concentration of LiPF6 in the electrolyte is 1.2 mol / L, and the total volume of injected electrolyte is 138.7 ml.

[0052] This comparative example does not include lithium-ion exchangers and only conforms to the conventional battery design of formula (2).

[0053] The final average capacity of the battery cells (25℃, 0.33C, 2.0-4.35V voltage range) was only 5.2 Ah. After verification and calculation, the active material capacity was only 12.3 mAh / g, reaching only 10.7% of the expected capacity.

[0054] Accordingly, a second aspect of the present invention provides a battery pack comprising a plurality of the aforementioned lithium-sodium hybrid-ion batteries, which are connected in series and / or parallel. By combining multiple lithium-sodium hybrid-ion batteries in series and parallel, the output voltage, capacity, and power characteristics of the battery pack can be flexibly adjusted according to actual application needs, meeting the diverse requirements of different electrical devices for energy storage systems. Since each individual cell constituting the battery pack has the lithium replenishment function of lithium-ion exchanger and the quantitative design of exchanger usage, the battery pack as a whole also exhibits advantages such as high capacity utilization efficiency, strong design reproducibility, and good process compatibility. It can be widely used in electric bicycles, electric robots, electric trucks, electric forklifts, electric aircraft, and energy storage power stations, providing a stable and reliable energy supply for various electrical devices.

[0055] The embodiments of the present invention aim to protect a lithium-sodium hybrid ion battery and battery pack, and have the following effects: 1. By introducing lithium-ion exchangers into the positive electrode, negative electrode, or separator of the battery, during charging and discharging, sodium ions released from the positive electrode undergo ion exchange with lithium ions in the exchanger, allowing lithium ions to continuously enter the electrolyte and embed into the negative electrode. This overcomes the limitation of the electrolyte's own lithium salt concentration on the lithium embedding capacity, significantly increasing the total lithium embedding in the negative electrode, and enabling the actual capacity of the cell to reach more than 95% of the design capacity. This effectively solves the key problem of commercial lithium-sodium hybrid ion batteries where the capacity is far below the design value due to insufficient lithium ion supply in the electrolyte.

[0056] 2. By establishing a quantitative relationship between the amount of lithium-ion exchanger added and the negative electrode capacity requirement and the total amount of lithium ions in the electrolyte, the number of moles of supplementary lithium ions provided by the exchanger is precisely matched with the lithium ion gap required for lithium intercalation in the negative electrode. At the same time, by designing the parameter k to constrain the capacity matching relationship between the positive and negative electrode active materials, it is ensured that the amount of exchanger used is neither excessive and wasteful nor insufficient and affects the capacity performance. This achieves precise control of cell capacity from the material design stage, improving the consistency and reliability of product design.

[0057] 3. By designing lithium-ion exchangers to be incorporated into positive electrode slurries, negative electrode slurries, or coated on the surface of separators in multiple ways, this technical solution can be flexibly adapted to existing lithium-ion battery production processes. It can achieve the preparation of hybrid battery systems without major modifications to existing production lines, thereby reducing the process threshold and equipment investment costs for industrialization. At the same time, the combined application of multiple addition methods can further optimize the uniformity of the exchanger distribution inside the cell, ensuring battery cycle performance and safety performance.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A lithium-sodium hybrid ion battery, characterized in that, include: Positive electrode, wherein the positive electrode comprises a sodium ion positive electrode material; Negative electrode, wherein the negative electrode comprises a lithium-ion negative electrode material; Electrolyte, wherein the electrolyte is an electrolyte for lithium-ion batteries; as well as A lithium-ion exchanger is disposed on or in at least one of the positive electrode, the negative electrode, and the separator, for replenishing lithium ions in the electrolyte during battery charging and discharging.

2. The lithium-sodium hybrid ion battery according to claim 1, characterized in that, The lithium ion exchanger includes: Li₂CO₃, LiCl, LiNO₃, and Li₃Zr₂Si₂PO₄. 12 Na 1+x Mn x / 2 Zr 2-x / 2 At least one of (PO4)3 and lithium carboxymethyl cellulose; Where 0 < x ≤ 2.

3. The lithium-sodium hybrid ion battery according to claim 2, characterized in that, The formula for calculating the amount of lithium-ion exchanger added is as follows: ； in, The unit area mass of the lithium-ion exchanger is expressed in g / m². 2 , Let n be the molar mass of the lithium-ion exchanger, and n be the number of lithium ions in the molecular formula of the lithium-ion exchanger. This represents the sum of the number of lithium ions in all exchangers corresponding to all unit electrode areas. It is a reversible specific capacity at the negative electrode. The design parameters are the unit area mass of the negative electrode active material. The value range is 1.0 to 1.

2. F It is Faraday's constant. This refers to the total volume of electrolyte injected. The sum of the lithium salt molar concentrations injected into the electrolyte, and S is the total area of ​​the negative electrode film. The design parameters The calculation formula is: ； in, This represents the mass per unit area of ​​the positive electrode active material. It represents the reversible specific capacity of the positive electrode.

4. The lithium-sodium hybrid ion battery according to claim 1, characterized in that, The lithium-ion exchanger is mixed with the sodium-ion cathode material slurry and then coated onto the positive electrode current collector of the battery. The lithium-ion exchanger is mixed with the lithium-ion anode material slurry and then coated onto the battery anode current collector; and / or The lithium-ion exchanger is coated on one or both sides of the battery separator.

5. The lithium-sodium hybrid ion battery according to any one of claims 1-4, characterized in that, The sodium ion cathode material includes at least one of layered transition metal oxides, polyanionic compounds, and Prussian blue analogues.

6. The lithium-sodium hybrid ion battery according to claim 5, characterized in that, The layered transition metal oxide is Na. x MO2; Where 0 < x ≤ 1, M includes at least one of Fe, Mn, Ni, Co and Cu.

7. The lithium-sodium hybrid ion battery according to claim 5, characterized in that, The polyanionic compound is Na. x M y (XO z ) n F m ; Wherein, 0 < x ≤ 3, 0 < y ≤ 2, 0 < z ≤ 4, 0 < n ≤ 3, 0 ≤ m ≤ 3, M includes at least one of Fe, V and Mn, X includes at least one of P, S and Si, and F is a doped anion.

8. The lithium-sodium hybrid ion battery according to claim 5, characterized in that, The Prussian blue analogues include: Na x M[Fe(CN)6] 1-y ·□ y ·nH2O; Where 0 < x ≤ 2, 0 < y < 1, □ represents a lattice vacancy, n represents the number of water molecules, and M includes at least one of Fe, Mn, Ni, and Co.

9. The lithium-sodium hybrid ion battery according to any one of claims 1-4, characterized in that, The lithium-ion anode material includes at least one of artificial graphite, natural graphite, silicon-carbon materials, and mesophase carbon microspheres.

10. A battery pack, characterized in that, The battery pack comprises a plurality of lithium-sodium hybrid ion batteries as described in any one of claims 1-9, connected in series and / or in parallel.

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