Sodium-ion battery and application thereof

Abstract

The application discloses a sodium ion battery and application thereof, and belongs to the technical field of batteries. The sodium ion battery comprises a positive electrode, a negative electrode, a diaphragm between the positive electrode and the negative electrode, and an electrolyte; and at least one of the positive electrode and the negative electrode contains a sodium ion exchange resin. By setting at least one of the positive electrode and the negative electrode to contain the sodium ion exchange resin, the sodium ion exchange resin has sodium ions capable of exchanging with protons, so that the generation of hydrolysis products is reduced through the sodium ion exchange resin, the structural integrity of the electrode, the interface stability and the dissolution of transition metal ions are improved, and finally the cycle performance of the sodium ion battery, in particular the high-temperature cycle stability, is improved.

Description

Technical Field

[0001] This disclosure relates to the field of battery technology, and in particular to sodium-ion batteries and their applications. Background Technology

[0002] Sodium-ion batteries rely on sodium ions (Na+) + Sodium-ion batteries utilize the insertion and extraction of electrodes between the positive and negative terminals to achieve the charging and discharging process, thereby storing and releasing electrical energy. Compared to lithium-ion batteries, sodium-ion batteries have advantages such as more abundant raw material reserves, wider resource distribution, lower potential costs, and a wider operating temperature range, giving them a potential cost advantage in large-scale energy storage.

[0003] Currently, sodium-ion batteries face the problem of high water content in the system. This leads to the hydrolysis of sodium salts and additives in the electrolyte. For example, water reacts with hexafluorophosphate ions in the electrolyte, hydrolyzing to form hydrofluoric acid. This causes the dissolution of the transition metal in the positive electrode, resulting in capacity decay and decreased cycle performance of the sodium-ion battery. Sulfate ester additives hydrolyze to form strong acids in high water content environments, further exacerbating the corrosive environment inside the battery. Therefore, it is necessary to control the hydrolysis reaction in sodium-ion batteries to reduce the negative impact of hydrolysis products on the battery. Summary of the Invention

[0004] This disclosure provides embodiments of sodium-ion batteries and their applications, which can solve the technical problems of battery capacity decay and cycle performance degradation caused by internal hydrolysis reactions in sodium-ion batteries in related technologies. Specifically, the technical solution is as follows.

[0005] In a first aspect, a sodium-ion battery is provided, the sodium-ion battery comprising: a positive electrode, a negative electrode, a separator located between the positive electrode and the negative electrode, and an electrolyte; at least one of the positive electrode and the negative electrode contains a sodium ion exchange resin.

[0006] The sodium-ion exchange battery provided in this disclosure involves configuring at least one of the positive and negative electrodes to contain a sodium-ion exchange resin. This resin contains exchangeable sodium ions. When the water content in the sodium-ion battery system is high, the sodium-ion exchange resin is in an environment containing protons (i.e., hydrogen ions), and an ion exchange reaction occurs, where its sodium ions exchange with hydrogen ions in the water, thereby reducing the proton concentration in the water. Since the degree of hydrolysis is directly related to the proton concentration, according to chemical equilibrium, when the proton concentration decreases, the degree of hydrolysis is suppressed, thus achieving the purpose of inhibiting the hydrolysis reaction and reducing the formation of hydrolysis products.

[0007] Reducing the formation of hydrolysis products is crucial for the performance of sodium-ion batteries (e.g., battery capacity, cycle performance). This is because acidic hydrolysis products corrode electrode materials, damage the structural integrity of the electrode surface, and alter the composition and properties of the electrolyte at the interface. Furthermore, for electrode materials containing transition metals, acidic hydrolysis products accelerate the dissolution of transition metal ions, all of which contribute to a decline in battery performance. This disclosure utilizes sodium ion exchange resin to reduce the formation of hydrolysis products, thereby improving the structural integrity and interfacial stability of the electrode and inhibiting the dissolution of transition metal ions. Ultimately, this improves the cycle performance of sodium-ion batteries, particularly their high-temperature cycle stability.

[0008] In some possible implementations, both the positive and negative electrodes include: a current collector and an active material layer attached to the surface of the current collector; at least one of the positive and negative electrodes further includes a modified coating attached to the surface of the active material layer, the modified coating comprising the sodium ion exchange resin. In this embodiment, by coating the surface of the active material layer with sodium ion exchange resin, that is, by modifying conventional positive and / or negative electrode sheets to form a modified coating containing sodium ion exchange resin on the surface of the active material layer, the modified coating acquires ion exchange functionality to inhibit hydrolysis reactions and reduce the formation of hydrolysis products.

[0009] In some possible implementations, the active material layer of the positive electrode includes a positive electrode active material, a first conductive agent, and a first binder, wherein the positive electrode active material includes at least one of layered transition metal oxides, polyanionic compounds, and Prussian blue compounds.

[0010] In some possible implementations, the active material layer of the negative electrode includes a negative electrode active material, a second conductive agent, and a second binder. The negative electrode active material includes at least one of graphite, amorphous carbon, hard carbon, soft carbon, alloy materials, titanium-based compounds, and molybdenum-based compounds.

[0011] In some possible implementations, the modified coating further includes a third binder, wherein the sodium ion exchange resin constitutes 60%-99.5% of the modified coating by mass, and the third binder constitutes 0.5%-40% of the modified coating by mass. The third binder ensures the coatability and structural stability of the modified coating.

[0012] In some possible implementations, the thickness of the modified coating is 0.01 μm to 10 μm. This allows for the achievement of the effects of the modified coating while avoiding any adverse impact of the sodium ion exchange resin on the basic properties of the active material layer.

[0013] In some possible implementations, both the positive and negative electrodes include: a current collector and an active material layer attached to the surface of the current collector; the active material layer of at least one of the positive and negative electrodes includes the sodium ion exchange resin. In this embodiment, by doping the active material layer with sodium ion exchange resin as a bulk phase modifier, an improved active material layer is obtained, thus preparing a modified positive and / or modified negative electrode. Therefore, the active material layer possesses ion exchange functionality to inhibit hydrolysis reactions and reduce the formation of hydrolysis products.

[0014] In some possible implementations, the active material layer of the positive electrode includes a positive electrode active material, a first conductive agent, and a first binder, wherein the positive electrode active material includes at least one of layered transition metal oxides, polyanionic compounds, and Prussian blue compounds.

[0015] In some possible implementations, the active material layer of the negative electrode includes a negative electrode active material, a second conductive agent, and a second binder. The negative electrode active material includes at least one of graphite, amorphous carbon, hard carbon, soft carbon, alloy materials, titanium-based compounds, and molybdenum-based compounds.

[0016] In some possible implementations, the sodium ion exchange resin accounts for 0.1%-1% of the mass percentage of the active material layer. This ensures that the active material layer satisfies the requirement of inhibiting hydrolysis while avoiding adverse effects of the sodium ion exchange resin on the basic properties of the active material layer, i.e., avoiding adverse effects on the basic performance (e.g., specific capacity) of the sodium-ion battery.

[0017] In some possible implementations, the sodium ion exchange resin includes a resin backbone and active groups located on the resin backbone; the active groups are -RSO3Na or -RCOONa, wherein the R group is a single bond, an alkyl subunit, or an unsaturated hydrocarbon subunit. The above sodium ion exchange resin can achieve the exchange of sodium ions with hydrogen ions in the battery system, and its exchange effect is particularly excellent when the active group is -RSO3Na.

[0018] In some possible implementations, the resin skeleton includes polystyrene resin, polyacrylic resin, or phenolic resin.

[0019] Secondly, embodiments of this disclosure provide a positive electrode sheet, the positive electrode sheet comprising a positive current collector, a positive active material layer attached to the surface of the positive current collector, and a modified coating attached to the surface of the positive active material layer, the modified coating comprising a sodium ion exchange resin.

[0020] Thirdly, embodiments of this disclosure provide a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive active material layer attached to the surface of the positive current collector, the positive active material layer containing a sodium ion exchange resin.

[0021] Fourthly, embodiments of this disclosure provide a negative electrode sheet, the negative electrode sheet comprising a negative current collector, a negative active material layer attached to the surface of the negative current collector, and a modified coating attached to the surface of the negative active material layer, the modified coating comprising a sodium ion exchange resin.

[0022] Fifthly, embodiments of this disclosure provide a negative electrode sheet, the negative electrode sheet comprising a negative current collector and a negative active material layer attached to the surface of the negative current collector, the negative active material layer containing a sodium ion exchange resin.

[0023] In a sixth aspect, embodiments of this disclosure provide a battery module, the battery module including a housing and a plurality of batteries housed inside the housing, at least a portion of the plurality of batteries being sodium-ion batteries as described above, or at least a portion of the plurality of batteries including the positive electrode plate as described above, or at least a portion of the plurality of batteries including the negative electrode plate as described above.

[0024] The battery module provided in this disclosure has all the advantages of the sodium-ion battery described above, which will not be repeated here. It should be noted that, in addition to the casing for fixing the batteries, the battery module also has a busbar to connect multiple batteries, realizing current collection and distribution among the batteries. The battery module also has a sampling device for monitoring parameters such as battery voltage and temperature.

[0025] The battery module provided in this disclosure can be applied to the following scenarios: electronic devices, electric vehicles, electric equipment, energy storage systems, etc.

[0026] In a seventh aspect, embodiments of this disclosure provide an electrical device, the electrical device including a battery pack, a controller and an electric actuator, the battery pack including a plurality of battery modules as described above, the battery pack being used to output electrical energy to the controller, and the controller being used to control the operation of the electric actuator.

[0027] The electrical device provided in this disclosure has all the advantages of the sodium-ion battery mentioned above, and will not be repeated here. Exemplarily, the electrical device can be an electronic device (e.g., a mobile phone, tablet computer, laptop computer, camera, game console, smartwatch, etc.), or an electric device (e.g., household electric devices (kitchen appliances, home appliances, etc.), industrial electric devices (processing and manufacturing equipment, lifting and transportation equipment, analysis and testing equipment, etc.), power tools, electric toys, etc.), or an electric vehicle (e.g., electric car, electric bicycle, electric motorcycle, etc.).

[0028] Eighthly, this disclosure provides an energy storage system comprising: a battery pack and a power converter; the battery pack comprising a plurality of battery modules as described above; the power converter being configured to convert the voltage output from the battery pack into power and output it to the power grid or a load, and / or to convert the voltage output from an external power source into power and output it to the battery pack.

[0029] The energy storage system provided in this disclosure has all the advantages of the sodium-ion battery mentioned above, and will not be repeated here. The energy storage system provided in this disclosure can be used on the grid side for peak shaving, frequency regulation, and grid congestion relief, or on the user side, such as for energy storage in microgrids, homes, and businesses, to improve energy utilization efficiency and power supply reliability. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of a sodium-ion battery provided in an embodiment of this disclosure;

[0031] Figure 2 A schematic diagram of an exemplary positive electrode sheet provided in an embodiment of this disclosure;

[0032] Figure 3 A schematic diagram of the structure of an exemplary negative electrode sheet provided in an embodiment of this disclosure;

[0033] Figure 4 This is a schematic diagram of the structure of another exemplary positive electrode sheet provided in an embodiment of this disclosure;

[0034] Figure 5 This is a schematic diagram of the structure of another exemplary negative electrode sheet provided in an embodiment of this disclosure;

[0035] Figure 6 This is a schematic diagram of the structure of an exemplary battery module provided in an embodiment of the present disclosure;

[0036] Figure 7 A schematic diagram illustrating the connection relationships of various components in an exemplary electrical device provided in this embodiment of the present disclosure;

[0037] Figure 8 A schematic diagram illustrating the connection relationships of various components in an exemplary energy storage system provided in this disclosure embodiment;

[0038] Figure 9 Infrared spectra of the positive electrodes of different sodium-ion batteries provided in embodiments of this disclosure;

[0039] Figure 10 Cyclic performance test graphs of different sodium-ion batteries provided in the embodiments of this disclosure at an operating temperature of 25°C and under conditions of 0.05C-0.5C;

[0040] Figure 11 Cyclic performance test graphs of different sodium-ion batteries provided in the embodiments of this disclosure at an operating temperature of 25°C and under 1C conditions;

[0041] Figure 12 Cyclic performance test graphs of different sodium-ion batteries provided in the embodiments of this disclosure at an operating temperature of 60°C and under conditions of 0.05C-0.5C;

[0042] Figure 13 Cyclic performance test graphs of different sodium-ion batteries provided in the embodiments of this disclosure at an operating temperature of 60°C and under 1C conditions;

[0043] Figure 14 Impedance test diagrams of different sodium-ion batteries at an operating temperature of 25°C, provided in the embodiments of this disclosure;

[0044] Figure 15 Impedance test diagrams of different sodium-ion batteries at an operating temperature of 60°C, provided in the embodiments of this disclosure.

[0045] in, Figure 10 and Figure 12 In this context, 0.05C corresponds to the 1st to 2nd cycle, 0.2C corresponds to the 3rd to 6th cycle, and 0.5C corresponds to the 7th to 11th cycle.

[0046] The reference numerals in the attached figures represent:

[0047] 101. Positive current collector; 102. Negative current collector; 201. Positive active material layer; 202. Negative active material layer; 300. Modified coating;

[0048] 001. Housing; 002. Battery. Detailed Implementation

[0049] First, some terms used in the embodiments of this disclosure will be explained, see below:

[0050] (1) Cathode: The electrode from which current flows out, with a higher potential, which gains electrons and has a reduction effect. In a sodium-ion battery, the positive electrode releases sodium ions during charging and accepts sodium ions for insertion during discharging.

[0051] (2) Anode: The electrode into which current flows, with a lower potential, which loses electrons and undergoes oxidation. In sodium-ion batteries, the anode provides a site for sodium ions to intercalate and releases sodium ions during discharge.

[0052] (3) Electrolyte: Provides the medium for ion exchange between the positive and negative electrodes of the battery.

[0053] (4) Separator: It is used to separate the positive and negative electrodes of the battery to prevent the two electrodes from contacting and short-circuiting, and to allow electrolyte ions to pass through.

[0054] This disclosure relates to a sodium-ion battery. Figure 1 A schematic diagram of the sodium-ion battery is shown in the attached figure. Figure 1 As shown, a sodium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive and negative electrodes are separated by the separator to prevent short circuits. The electrolyte wets both the positive and negative electrodes and contains a sodium salt electrolyte to serve as a medium for the flow of sodium ions. During charging, sodium ions are deintercalated from the positive electrode and intercalated into the negative electrode via the electrolyte; during discharging, sodium ions are deintercalated from the negative electrode and reintercalated into the positive electrode via the electrolyte.

[0055] Electrolytes typically consist of a sodium electrolyte salt, a solvent, and optional additives (such as sulfate esters). When the water content of a sodium-ion battery system is high, the sodium electrolyte salt and additives in the electrolyte hydrolyze, forming acidic substances. These acidic substances create a corrosive environment inside the battery, leading to the dissolution of both the positive and negative electrode materials. For example, with sodium hexafluorophosphate as the sodium salt, when the water content is high, the hexafluorophosphate ions provided by sodium hexafluorophosphate react with water to produce hydrofluoric acid. This hydrofluoric acid causes the dissolution of transition metals in the positive electrode, resulting in capacity decay and reduced cycle performance of the sodium-ion battery. Similarly, with sulfate esters as additives, these additives hydrolyze in high-water-content environments to generate strong acids. These strong acids further exacerbate the corrosive environment inside the battery, further degrading the capacity and cycle performance of the sodium-ion battery.

[0056] It is evident that current sodium-ion battery systems suffer from high water content, leading to the hydrolysis of sodium salts and additives in the electrolyte. Since the resulting hydrolysis products are typically acidic, they negatively impact the stability of electrode materials and interfaces, consequently causing performance degradation, such as battery capacity and cycle life. Therefore, it is necessary to suppress the aforementioned hydrolysis reactions occurring within the battery.

[0057] Firstly, this disclosure provides a novel sodium-ion battery that has the advantages of inhibiting hydrolysis reactions, reducing the generation of hydrolysis products, and thus improving battery performance, thereby solving the technical problems existing in related technologies. See also... Figure 1 The sodium-ion battery includes: a positive electrode, a negative electrode, a separator located between the positive and negative electrodes, and an electrolyte; at least one of the positive and negative electrodes contains a sodium ion exchange resin.

[0058] Sodium ion exchange resin, also known as sodium-type cation exchange resin, consists of a resin backbone and active groups attached to the resin backbone. The active groups carry exchangeable sodium ions, thus giving sodium ion exchange resin its ion exchange function.

[0059] The sodium-ion exchange battery provided in this disclosure involves configuring at least one of the positive and negative electrodes with a sodium-ion exchange resin. This resin contains exchangeable sodium ions. When the water content in the sodium-ion battery system is high, the sodium-ion exchange resin is in an environment containing protons (i.e., hydrogen ions), and an ion exchange reaction occurs, where its sodium ions exchange with hydrogen ions in the water, thereby reducing the proton concentration in the water. Since the degree of hydrolysis is directly related to the proton concentration, according to chemical equilibrium, when the proton concentration decreases, the degree of hydrolysis is suppressed, thus achieving the purpose of inhibiting the hydrolysis reaction and reducing the formation of hydrolysis products. Reducing the formation of hydrolysis products has a positive impact on the performance of the sodium-ion battery (e.g., battery capacity, cycle performance). This is because acidic hydrolysis products corrode electrode materials, damage the structural integrity of the electrode surface, and change the composition and properties of the electrolyte at the interface. Moreover, for electrode materials containing transition metals, acidic hydrolysis products accelerate the dissolution of transition metal ions, all of which lead to a decrease in battery performance. This disclosure uses sodium ion exchange resin to reduce the generation of hydrolysis products, which helps to improve the structural integrity and interface stability of the electrode and inhibit the dissolution of transition metal ions, ultimately achieving the goal of improving the cycle performance of sodium ion batteries, especially the high-temperature cycle stability.

[0060] It should be noted that the mechanism by which sodium ion exchange resin improves interfacial stability lies in the reduction of acidic hydrolysis products, which improves the chemical environment at the interface between the positive and negative electrodes and the electrolyte. The electrode materials at the interface are no longer corroded by acidic substances, allowing them to maintain their original structure and performance. Simultaneously, the composition and properties of the electrolyte become more stable, facilitating ion transport at the interface; for example, the insertion and extraction of sodium ions between the positive and negative electrodes and the electrolyte proceeds more smoothly. Regarding the mechanism by which sodium ion exchange resin inhibits the dissolution of transition metal ions, it is because ion exchange reduces the proton concentration in the sodium-ion battery system, improving the acidic environment. This weakens the driving force for transition metal ions to dissolve from the electrode materials, allowing them to better remain in their original positions and maintain the structural and compositional stability of the electrode materials. This is particularly beneficial for improving the cycle stability of the battery at high temperatures. Because hydrolysis and the tendency for transition metal ion dissolution are typically intensified at high temperatures, this inhibitory effect is even more crucial.

[0061] As mentioned above, the sodium ion exchange resin includes a resin skeleton and active groups attached to the resin skeleton. The active groups are -RSO3Na or -RCOONa, wherein the R group includes a single bond, an alkyl subunit, or an unsaturated hydrocarbon subunit. This sodium ion exchange resin can achieve the exchange of sodium ions with hydrogen ions in the battery system, and its exchange effect is particularly excellent when the active group is -RSO3Na.

[0062] For example, the alkyl group can be a C1-C10 alkyl group, including but not limited to methyl (with a corresponding methylene subunit), ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, etc. When the R group is alkyl, it is beneficial to enhance the chemical stability of the active group. For unsaturated hydrocarbon groups, they can be alkenyl (vinyl, propenyl, butenyl, etc.), ynyl (ethynyl, propynyl, butynyl, etc.), aromatic (phenyl, etc.), or combinations thereof. When the R group is unsaturated hydrocarbon, it is beneficial to enhance the reactivity of the active group.

[0063] The total exchange capacity of a sodium ion exchange resin refers to the total number of all active groups in a unit mass or unit volume of resin. It represents the theoretically maximum ion exchange capacity that a sodium ion exchange resin can perform, and is typically expressed in mmol / g (millimoles per gram of dry resin). In the embodiments of this disclosure, the total exchange capacity of the sodium ion exchange resin can be ≥3 mmol / g to ensure its effective ion exchange capacity.

[0064] The resin skeleton of the sodium ion exchange resin applicable to the embodiments of this disclosure includes polystyrene-type resin, polyacrylic resin, or phenolic resin.

[0065] The resin skeleton of polystyrene-type resins refers to a polymer synthesized from styrene monomers and divinylbenzene as a crosslinking agent. Styrene units form long-chain structures through polymerization, while divinylbenzene acts as a crosslinking agent between the polymer chains, constructing a three-dimensional network resin skeleton. This skeleton structure exhibits regularity and stability, and its internal pore structure can be adjusted by controlling the polymerization conditions. In some examples, the polystyrene-type resin skeleton does not have obvious macropores in the dry state, but micropores form after absorbing water, with pore sizes ranging from 1 nm to 5 nm.

[0066] Polystyrene-type resins typically possess a high exchange capacity, good exchange selectivity for inorganic cations, and good chemical stability, enabling them to operate over a wide pH range and temperature conditions. For example, an exemplary sodium ion exchange resin may comprise a polystyrene-type resin backbone and active groups -RSO3Na attached to the polystyrene-type resin backbone. As a further example, a strongly acidic polystyrene-type sodium ion exchange resin with the designation 001×7 can be used.

[0067] The resin backbone of polyacrylic acid resins is polymerized from acrylic monomers such as acrylic acid or methacrylic acid. Its molecular chain is mainly composed of acrylic acid units, which contain carboxyl groups (-COOH). During the preparation of sodium ion exchange resins, the hydrogen ions in the carboxyl groups can be partially or completely replaced by sodium ions. The backbone structure of polyacrylic acid resins is relatively soft and has a certain degree of elasticity. Its degree of crosslinking can be controlled by changing the polymerization conditions and the amount of crosslinking agent used.

[0068] The resin backbone of phenolic resins is formed by the condensation reaction of phenols (such as phenol) and aldehydes (such as formaldehyde). During the reaction, condensation reactions occur between phenolic hydroxyl groups and aldehyde groups, generating a polymer with a three-dimensional network structure. This backbone structure contains many aromatic rings, exhibiting high rigidity and thermal stability. Phenolic resins possess good thermal and chemical stability, can withstand high temperatures and some harsh chemical environments, and have high mechanical strength, making them less prone to breakage. This gives them more advantages in applications requiring the resistance to pressure or friction.

[0069] In some examples, the positive electrode of the sodium-ion battery contains sodium ion exchange resin. In other examples, the negative electrode of the sodium-ion battery contains sodium ion exchange resin. In still other examples, both the positive and negative electrodes of the sodium-ion battery contain sodium ion exchange resin.

[0070] The form in which sodium ion exchange resin exists in the positive and / or negative electrodes may include: existing in the active material layer of the positive and / or negative electrodes, or existing in a separately arranged coating. These are illustrated below with relevant examples.

[0071] In some embodiments (1), a type of sodium-ion battery is provided in which both the positive and negative electrodes include: a current collector and an active material layer attached to the surface of the current collector. At least one of the positive and negative electrodes further includes a modified coating attached to the surface of the active material layer, the modified coating comprising a sodium ion exchange resin.

[0072] In this embodiment, sodium ion exchange resin is coated onto the surface of the active material layer in the form of a coating. That is, conventional positive and / or negative electrode sheets can be modified to form a modified coating containing sodium ion exchange resin on the surface of the active material layer. Thus, the modified coating has ion exchange function to inhibit hydrolysis reaction and reduce the generation of hydrolysis products.

[0073] Based on the above implementation scheme (1), as an example (1.1), see [link to implementation scheme (1)]. Figure 2 The positive electrode of a sodium-ion battery includes: a positive electrode current collector 101, a positive electrode active material layer 201 attached to the surface of the positive electrode current collector 101, and a modified coating 300 attached to the surface of the positive electrode active material layer 201, wherein the modified coating 300 includes a sodium ion exchange resin. This is more advantageous for constructing a more stable cathode electrolyte interface (CEI). It is evident that by adding a modified coating containing sodium ion exchange resin to the positive electrode, the generation of hydrolysis products is reduced through the sodium ion exchange resin, thereby improving the structural integrity and interfacial stability of the positive electrode sheet and inhibiting the dissolution of transition metal ions, ultimately achieving the goal of improving the cycle performance of the sodium-ion battery, especially its high-temperature cycle stability.

[0074] As an example (1.2), see Figure 3 The negative electrode of the sodium-ion battery includes: a negative electrode current collector 102, a negative electrode active material layer 202 attached to the surface of the negative electrode current collector 102, and a modified coating 300 attached to the surface of the negative electrode active material layer 202, wherein the modified coating 300 includes a sodium ion exchange resin.

[0075] It is evident that by adding a modified coating containing sodium ion exchange resin to the negative electrode, the generation of hydrolysis products can be reduced through the sodium ion exchange resin, thereby improving the structural integrity and interfacial stability of the negative electrode sheet and inhibiting the dissolution of transition metal ions, ultimately achieving the goal of improving the cycle performance of sodium-ion batteries, especially high-temperature cycle stability.

[0076] As an example (1.3), the positive electrode of a sodium-ion battery includes: a positive electrode current collector 101, a positive electrode active material layer 201 attached to the surface of the positive electrode current collector 101, and a modified coating 300 attached to the surface of the positive electrode active material layer 201. The negative electrode of a sodium-ion battery includes: a negative electrode current collector 102, a negative electrode active material layer 202 attached to the surface of the negative electrode current collector 102, and a modified coating 300 attached to the surface of the negative electrode active material layer 202. The modified coating mentioned above includes a sodium ion exchange resin.

[0077] To ensure the coatability and structural stability of the modified coating, the modified coating also includes a third binder. Specifically, the modified coating comprises sodium ion exchange resin and a third binder, with the sodium ion exchange resin comprising 60%-99.5% of the modified coating by mass, and the third binder comprising 0.5%-40% of the modified coating by mass. For example, the mass percentage of sodium ion exchange resin in the modified coating can be any of the following values ​​or any range of two values: 60%, 65%, 70%, 75%, 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, etc.

[0078] Some suitable third binders can be polyvinylidene fluoride, polyvinyl alcohol, epoxy resin, etc. For example, polyvinylidene fluoride can be used as a third binder. It has good compatibility with sodium ion exchange resin and can maintain its bonding performance in different chemical environments. At the same time, polyvinylidene fluoride has good mechanical properties, such as high tensile strength and toughness, which can provide certain strength and wear resistance for the modified coating.

[0079] In the application of modified coatings, to ensure the coating is coatable, a diluent can be used to dissolve and disperse the sodium ion exchange resin and the third binder. This diluent is then removed during the subsequent drying process after coating. Suitable diluents include N-methylpyrrolidone and ethanol.

[0080] While satisfying the effects brought about by the modified coating, in order to avoid the sodium ion exchange resin from adversely affecting the basic performance of the active material layer, that is, to avoid adversely affecting the basic performance of sodium ion batteries (such as specific capacity), the thickness of the modified coating can be controlled to be 0.01μm-10μm, which can be further 0.1μm-5μm, 0.1μm-4μm, 0.1μm-3μm, 0.1μm-2μm, 0.1μm-1μm, etc.

[0081] Regarding the aforementioned implementation scheme (1), the corresponding positive and / or negative electrodes can be prepared by the following method: Sodium ion exchange resin, a third binder, and a diluent are mixed uniformly according to a set ratio to form a slurry. A positive electrode sheet and / or a negative electrode sheet are provided, wherein both the positive and negative electrode sheets include: a current collector and an active material layer attached to the surface of the current collector. The slurry is coated onto the surface of the active material layer of the positive and / or negative electrode sheets, and then vacuum dried to form a dry modified coating on the surface of the active material layer, thus preparing the positive and / or negative electrodes. The coating process can be, for example, casting coating or spraying.

[0082] Regarding the aforementioned implementation scheme (1), the active material layer of the positive electrode of the sodium-ion battery includes a positive electrode active material, a first conductive agent, and a first binder. The positive electrode active material includes at least one of layered transition metal oxides, polyanionic compounds, and Prussian blue compounds. The aforementioned positive electrode active material allows sodium ions to intercalate and deintercalate, and typically exhibits high specific capacity, good structural stability, and rate performance.

[0083] For example, the positive electrode active material may account for 70%-95% of the mass of the active material layer, the first conductive agent may account for 1%-20% of the mass of the active material layer, and the first binder may account for 1%-20% of the mass of the active material layer.

[0084] For layered transition metal oxides, the chemical formula can be NaMO2, where M is one or more transition metal elements. Further, layered transition metal oxides can be nickel-based layered transition metal oxides (e.g., NaNiO2, NaNi...). 0.5 Mn 0.5 O2, NaNi 0.5 Fe 0.5 O2, etc., can also be manganese-based transition metal oxides (e.g., NaMnO2, Na 0.7 MnO2, etc., can also be cobalt-based transition metal oxides (e.g., NaCoO2, Na...). 0.6 CoO2, etc., can also be multi-layered transition metal oxides (e.g., NaNi). 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, NaCu 0.22 Fe 0.3 Mn 0.48 O2, NaNi 1 / 3 Mn 1 / 3Co 1 / 3 O2, NaNi 0.4 Mn 0.4 Co 0.2(O2, etc.). In the above chemical formulas, the subscripts of each element refer to the atomic ratio.

[0085] For polyanionic compounds, the general chemical formula can be Na. x E y (X a O b ) z Or Na x E y (X a O b ) z F w In the above general chemical formula, E can be at least one of Ti, V, Cr, Mn, Fe, Co, Ni, Ca, Mg, Al, and Nb; X can be at least one of Si, S, P, As, B, Mo, W, and Ge. The subscripts of the elements in the above general chemical formula refer to the atomic ratio. For further examples, polyanionic compounds can be Na4Fe3(PO4)2P2O7, sodium vanadium phosphate Na3V2(PO4)3, sodium vanadium fluorophosphate NaVPO4F, sodium vanadium trifluorophosphate Na3V2(PO4)2F3, and sodium iron phosphate with an olivine structure NaFePO4, etc.

[0086] Prussian blue analogs (PBAs) can be Prussian blue, Prussian white, etc.

[0087] The first conductive agent is used to improve the electronic conductivity between positive electrode active materials and improve the overall performance of the battery. Some suitable first conductive agents can be carbon-based conductive agents, including but not limited to conductive carbon black (such as Ketjen black, acetylene black, etc.), carbon nanotubes, graphene, etc. Of course, it is not excluded that metal conductive agents, composite conductive agents or conductive polymers can also be used as the first conductive agent.

[0088] The first binder is used to achieve stable contact and dispersion between the positive electrode active material and the first conductive agent. Some suitable first binders can be polyvinylidene fluoride, polyvinyl alcohol, sodium carboxymethyl cellulose, polyacrylic acid, polyamide amine, styrene-butadiene rubber, etc.

[0089] Regarding the aforementioned implementation scheme (1), the active material layer of the negative electrode of the sodium-ion battery includes a negative electrode active material, a second conductive agent, and a second binder. The negative electrode active material includes at least one of graphite, amorphous carbon, hard carbon, soft carbon, alloy materials, titanium-based compounds, and molybdenum-based compounds. The aforementioned negative electrode active material allows sodium ions to insert and extract, provides an electron conduction path, and possesses strong structural stability.

[0090] For example, the negative electrode active material may account for 70%-95% of the mass of the active material layer, the second conductive agent may account for 1%-20% of the mass of the active material layer, and the second binder may account for 1%-20% of the mass of the active material layer.

[0091] For alloy materials, they can be tin-based alloy materials, silicon-based alloy materials, etc. For titanium-based compounds, they can be titanium dioxide, etc. For molybdenum-based compounds, they can be molybdenum trioxide, etc.

[0092] The second conductive agent is used to improve the electronic conductivity between the negative electrode active materials and improve the overall performance of the battery. Some suitable second conductive agents can be carbon-based conductive agents, including but not limited to conductive carbon black (such as Ketjen black, acetylene black, etc.), carbon nanotubes, graphene, etc. Of course, it is not excluded that metal conductive agents, composite conductive agents or conductive polymers can also be used as second conductive agents.

[0093] The second binder is used to achieve stable contact and dispersion between the negative electrode active material and the second conductive agent. Some suitable second binders can be polyvinylidene fluoride, polyvinyl alcohol, sodium carboxymethyl cellulose, polyacrylic acid, polyamide amine, styrene-butadiene rubber, etc.

[0094] In some embodiments (2), a type of sodium-ion battery is provided in which both the positive and negative electrodes include: a current collector and an active material layer attached to the surface of the current collector. The active material layer of at least one of the positive and negative electrodes includes a sodium ion exchange resin.

[0095] In this embodiment, an improved active material layer is obtained by doping sodium ion exchange resin into the active material layer, using the sodium ion exchange resin as a bulk phase modifier, thus preparing a modified positive electrode and / or a modified negative electrode. Consequently, the active material layer acquires ion exchange functionality, thereby inhibiting hydrolysis reactions and reducing the formation of hydrolysis products.

[0096] Based on the above implementation scheme (2), as an example (2.1), see Figure 4 The positive electrode of the sodium-ion battery includes: a positive electrode current collector 101, and a positive electrode active material layer 201 attached to the surface of the positive electrode current collector 101, wherein the positive electrode active material layer 201 contains a sodium ion exchange resin (the sodium ion exchange resin can be made from...). Figure 4(Multiple curve segments in the positive electrode active material layer 201 represent this), which is more advantageous for constructing a more stable cathode electrolyte interface (CEI). It is evident that by adding a specific amount of sodium ion exchange resin to the positive electrode active material layer, the generation of hydrolysis products can be reduced, thereby improving the structural integrity and interfacial stability of the positive electrode sheet and inhibiting the dissolution of transition metal ions. Ultimately, this achieves the goal of improving the cycle performance of sodium-ion batteries, especially their high-temperature cycle stability.

[0097] As an example (2.2), see Figure 5 The negative electrode of the sodium-ion battery includes: a negative electrode current collector 102, and a negative electrode active material layer 202 attached to the surface of the negative electrode current collector 102, wherein the negative electrode active material layer 202 contains a sodium ion exchange resin (the sodium ion exchange resin can be made from...). Figure 5 (Multiple curve segments in the negative electrode active material layer 202 are shown). It can be seen that by adding a specific amount of sodium ion exchange resin to the negative electrode active material layer, the generation of hydrolysis products is reduced through the sodium ion exchange resin, thereby improving the structural integrity and interfacial stability of the negative electrode sheet and inhibiting the dissolution of transition metal ions, ultimately achieving the goal of improving the cycle performance of sodium-ion batteries, especially the high-temperature cycle stability.

[0098] As an example (2.3), the positive electrode of the sodium-ion battery includes: a positive electrode current collector 101, and a positive electrode active material layer 201 attached to the surface of the positive electrode current collector 101, wherein the positive electrode active material layer 201 contains sodium ion exchange resin. The negative electrode of the sodium-ion battery includes: a negative electrode current collector 102, and a negative electrode active material layer 202 attached to the surface of the negative electrode current collector 102, wherein the negative electrode active material layer 202 contains sodium ion exchange resin.

[0099] Based on the premise that the active material layer satisfies the requirement of inhibiting hydrolysis reaction, in order to avoid the sodium ion exchange resin from adversely affecting the basic performance of the active material layer, that is, to avoid adversely affecting the basic performance of sodium ion battery (such as specific capacity), the mass percentage of sodium ion exchange resin in the active material layer can be controlled to be 0.1%-1%, which can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc.

[0100] For implementation scheme (2), the active material layer of the positive electrode of the sodium-ion battery includes a positive electrode active material, a first conductive agent and a first binder, wherein the positive electrode active material includes at least one of layered transition metal oxides, polyanionic compounds and Prussian blue compounds.

[0101] When the positive electrode contains sodium ion exchange resin, the active material layer of the positive electrode accordingly includes a positive electrode active material, a first conductive agent, a first binder, and sodium ion exchange resin. For example, the positive electrode active material may account for 70%-95% of the mass of the active material layer, the first conductive agent may account for 1%-20% of the mass of the active material layer, the first binder may account for 1%-20% of the mass of the active material layer, and the sodium ion exchange resin may account for 0.1%-1% of the mass of the active material layer.

[0102] Regarding the positive electrode active material, the first conductive agent and the first binder involved here, please refer to the relevant schemes of the positive electrode active material, the first conductive agent and the first binder in the above-mentioned implementation scheme (1), which will not be repeated here.

[0103] For implementation scheme (2), the active material layer of the negative electrode of the sodium-ion battery includes a negative electrode active material, a second conductive agent and a second binder. The negative electrode active material includes at least one of graphite, amorphous carbon, hard carbon, soft carbon, alloy materials, titanium-based compounds and molybdenum-based compounds.

[0104] When the negative electrode contains sodium ion exchange resin, the corresponding active material layer of the positive electrode includes a negative electrode active material, a second conductive agent, a second binder, and sodium ion exchange resin. For example, the negative electrode active material may account for 70%-95% of the mass of the active material layer, the second conductive agent may account for 1%-20% of the mass of the active material layer, the second binder may account for 1%-20% of the mass of the active material layer, and the sodium ion exchange resin may account for 0.1%-1% of the mass of the active material layer.

[0105] Regarding the negative electrode active material, the second conductive agent, and the second binder involved here, please refer to the relevant schemes of the negative electrode active material, the second conductive agent, and the second binder in the above-mentioned implementation scheme (1), which will not be repeated here.

[0106] Regarding the aforementioned implementation scheme (2), the corresponding positive and / or negative electrodes can be prepared using the following methods: For the preparation of the positive electrode, this includes: uniformly mixing sodium ion exchange resin, positive electrode active material, first conductive agent, and first binder in a certain proportion to form a positive electrode slurry. The positive electrode slurry is then coated onto the surface of the current collector and dried under vacuum to obtain the positive electrode. For the preparation of the negative electrode, this includes: uniformly mixing sodium ion exchange resin, negative electrode active material, second conductive agent, and second binder in a certain proportion to form a negative electrode slurry. The negative electrode slurry is then coated onto the surface of the current collector and dried under vacuum to obtain the negative electrode.

[0107] For any of the sodium-ion batteries mentioned above, the current collector involved in its positive electrode can be aluminum foil. Within the operating voltage range of sodium-ion batteries, aluminum foil is relatively stable and will not undergo serious side reactions with the positive electrode active material. In addition, aluminum foil has advantages such as good conductivity and light weight.

[0108] For any of the sodium-ion batteries mentioned above, the current collector used in the negative electrode can be copper foil. Copper foil has high conductivity, which can effectively collect and transfer the current generated by the negative electrode. Furthermore, copper foil is stable to sodium at low potentials and will not form an alloy with sodium, thus avoiding the current collector from participating in chemical reactions that could affect battery performance.

[0109] For any of the sodium-ion batteries mentioned above, the electrolyte includes an electrolyte sodium salt, a solvent, and optional additives. For example, the electrolyte sodium salt can be a fluorinated sodium salt, a boron-containing sodium salt, or sodium perchlorate. For instance, the fluorinated sodium salt can be sodium hexafluorophosphate (NaPF6), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium tetrafluoroborate (NaBF4), etc. Among these, sodium hexafluorophosphate is currently the most commonly used sodium salt in sodium-ion battery electrolytes, possessing advantages such as good ionic conductivity. The boron-containing sodium salt can be disodium tetrafluoroborate (Na2BF4), sodium difluorooxalate borate (NaDFOB), etc.

[0110] The solvent can be either an ester or an ether. For example, ester solvents can include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC). Esters have good solubility for sodium salts, provide excellent ion transport capabilities, and are structurally stable, oxidation-resistant, and highly safe. Two or more ester solvents can be mixed and used as the electrolyte solvent. Ether solvents can include dimethyl glycol ether (DME) and dioxolane (DOL). Ether solvents can promote the insertion of sodium ions between carbon material layers, improving the material's specific capacity, initial coulombic efficiency, and rate performance.

[0111] Additives are optional; for example, they can be film-forming additives, including fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,3-propanesulfonate lactone (1,3-PS), triallyl phosphate (PST), and sodium difluorophosphate (NaDFP). During the first charge and discharge cycle of the battery, these additives can form a dense, uniform, and relatively thin solid electrolyte interface (SEI) film on the surfaces of the positive and negative electrodes, effectively separating the electrolyte from the electrodes and improving the battery's cycle life and rate performance.

[0112] Additives can also be sodium salts, such as sodium difluorooxalate borate (NaDFOB), which not only provide sodium ions as a solute but also improve electrolyte performance. Further, additives can include sodium saccharin, silane compounds, and phosphazene compounds. Sodium saccharin can increase the initial capacity of sodium-ion batteries; silane compounds, such as tris(trimethylsilane)phosphate (TMSP) and tris(trimethylsilane)borate (TMSB), can improve the performance of the SEI film; and phosphazene compounds, such as ethoxypentafluorotriphosphazene and phenoxypentafluorotriphosphazene, can improve the flame retardancy and thermal stability of the electrolyte. The choice of whether to add additives and the type of additives should be based on actual needs.

[0113] For any of the sodium-ion batteries mentioned above, the separator involved can be a polypropylene separator, a polyethylene separator, a polypropylene / polyethylene composite separator, a polyimide separator, an aramid separator, an alumina ceramic separator, a titanium dioxide ceramic separator, a regenerated cellulose separator, etc., and can be selected according to actual needs.

[0114] Secondly, this disclosure provides a positive electrode sheet, see [link to previous document]. Figure 2 The positive electrode includes a positive current collector 101, a positive active material layer 201 attached to the surface of the positive current collector 101, and a modified coating 300 attached to the surface of the positive active material layer 201, the modified coating 300 including sodium ion exchange resin.

[0115] The positive electrode plate involved in this embodiment is the example (1.1) in the implementation scheme (1) of the sodium-ion battery mentioned in the first aspect above. The implementation scheme of the positive electrode plate can be found in example (1.1), and will not be repeated here.

[0116] By adding a modified coating containing sodium ion exchange resin to the positive electrode, the generation of hydrolysis products can be reduced through the sodium ion exchange resin, thereby improving the structural integrity and interfacial stability of the positive electrode and inhibiting the dissolution of transition metal ions. Ultimately, this achieves the goal of improving the cycle performance of sodium-ion batteries, especially their high-temperature cycle stability.

[0117] Thirdly, this disclosure provides a positive electrode sheet, see [link to relevant documentation]. Figure 4 The positive electrode includes a positive current collector 101 and a positive active material layer 201 attached to the surface of the positive current collector 101. The positive active material layer 201 contains a sodium ion exchange resin (the sodium ion exchange resin can be made from...). Figure 4 (This is represented by multiple curve segments in the positive electrode active material layer 201).

[0118] The positive electrode plate involved in this embodiment is the example (2.1) in the implementation scheme (2) of the sodium-ion battery involved in the first aspect above. The implementation scheme of the positive electrode plate can be found in example (2.1), and will not be repeated here.

[0119] By adding a specific amount of sodium ion exchange resin to the positive electrode active material layer of the positive electrode sheet, the generation of hydrolysis products can be reduced through the sodium ion exchange resin, thereby improving the structural integrity and interfacial stability of the positive electrode sheet and inhibiting the dissolution of transition metal ions, ultimately achieving the goal of improving the cycle performance of sodium-ion batteries, especially the high-temperature cycle stability.

[0120] Fourthly, embodiments of this disclosure provide a negative electrode sheet, see [link to relevant documentation]. Figure 3 The negative electrode sheet includes a negative current collector 102, a negative active material layer 202 attached to the surface of the negative current collector 102, and a modified coating 300 attached to the surface of the negative active material layer 202, the modified coating 300 including sodium ion exchange resin.

[0121] The negative electrode plate involved in this embodiment is the example (1.2) in the implementation scheme (1) of the sodium-ion battery involved in the first aspect above. The implementation scheme of the negative electrode plate can be found in example (1.2), and will not be repeated here.

[0122] By adding a modified coating containing sodium ion exchange resin to the negative electrode, the generation of hydrolysis products can be reduced through the sodium ion exchange resin, thereby improving the structural integrity and interfacial stability of the negative electrode and inhibiting the dissolution of transition metal ions. Ultimately, this achieves the goal of improving the cycle performance of sodium-ion batteries, especially their high-temperature cycle stability.

[0123] Fifthly, embodiments of this disclosure provide a negative electrode sheet, see [link to relevant documentation]. Figure 5 The negative electrode includes a negative current collector 102 and a negative active material layer 202 attached to the surface of the negative current collector 102. The negative active material layer 202 contains a sodium ion exchange resin (the sodium ion exchange resin can be made from...). Figure 5 (This is represented by multiple curve segments in the negative electrode active material layer 202).

[0124] The negative electrode plate involved in this embodiment is the example (2.2) in the implementation scheme (2) of the sodium-ion battery involved in the first aspect above. The implementation scheme of the negative electrode plate can be found in example (2.2), and will not be repeated here.

[0125] By adding a specific amount of sodium ion exchange resin to the negative electrode active material layer of the negative electrode sheet, the generation of hydrolysis products can be reduced through the sodium ion exchange resin, thereby improving the structural integrity and interfacial stability of the negative electrode sheet and inhibiting the dissolution of transition metal ions, ultimately achieving the goal of improving the cycle performance of sodium-ion batteries, especially the high-temperature cycle stability.

[0126] Sixthly, embodiments of this disclosure provide a battery module, see [link to previous document]. Figure 6 The battery module includes a housing 001 and a plurality of batteries 002 housed inside the housing 001. At least a portion of the batteries 002 are sodium-ion batteries as described above, or at least a portion of the batteries 002 include the positive electrode plate as described above, or at least a portion of the batteries 002 include the negative electrode plate as described above. For example, all of the batteries 002 are sodium-ion batteries as described above, or all of the batteries include the positive electrode plate as described above, or all of the batteries include the negative electrode plate as described above.

[0127] The battery module provided in this disclosure has all the advantages of the sodium-ion battery mentioned above, which will not be repeated here.

[0128] It should be noted that multiple batteries 002 are arranged within the casing 001 according to a predetermined arrangement, for example, Figure 6 The example illustrates that the batteries 002 inside the casing 001 are arranged in multiple rows, with each row containing multiple batteries 002 arranged in columns. Insulating foam is placed between the large surfaces of any two adjacent batteries 002 to buffer stress. The casing 001 can be in the form of an outer shell or a frame, depending on the actual requirements.

[0129] In addition to the casing for securing the batteries, the battery module also features a busbar to connect multiple batteries, enabling current collection and distribution among them. The battery module also includes sampling devices to monitor parameters such as battery voltage and temperature.

[0130] The battery module provided in this disclosure can be applied to the following scenarios: electronic devices, electric vehicles, electric equipment, energy storage systems, etc.

[0131] Seventhly, embodiments of this disclosure provide an electrical appliance, see [link to relevant documentation]. Figure 7 The electrical equipment includes a battery pack, a controller, and an electric actuator. The battery pack includes multiple battery modules as described above. The battery pack is used to output electrical energy to the controller, which is used to control the operation of the electric actuator.

[0132] See Figure 7The battery pack is electrically connected to the controller, which is in turn electrically connected to the electric actuator. The controller is used to regulate the electrical energy output (e.g., current and voltage). The electric actuator is a mechanism that can convert electrical energy into mechanical energy, such as a motor.

[0133] The electrical device provided in this disclosure has all the advantages of the sodium-ion battery mentioned above, which will not be repeated here. It should be noted that, in addition to the battery pack, controller, and electric actuator, the electrical device may also include a power management system for managing the battery pack, a housing structure for providing physical support and protection, a heat dissipation system for thermal management of the battery pack and other components, etc.

[0134] For example, the electrical equipment can be an electronic device (e.g., a mobile phone, tablet computer, laptop computer, camera, game console, smartwatch, etc.), or an electric device (e.g., household electric devices (kitchen appliances, home appliances, etc.), industrial electric devices (processing and manufacturing equipment, lifting and transportation equipment, analysis and testing equipment, etc.), power tools, electric toys, etc.), or an electric vehicle (e.g., electric car, electric bicycle, electric motorcycle, etc.).

[0135] Eighthly, embodiments of this disclosure provide an energy storage system, see [link to relevant documentation]. Figure 8 The energy storage system includes a battery pack and a power converter. The battery pack includes multiple battery modules as described above. The power converter is used to convert the voltage output from the battery pack into power and output it to the grid or load, and / or to convert the voltage output from an external power source into power and output it to the battery pack.

[0136] The energy storage system provided in this disclosure has all the advantages of the sodium-ion battery mentioned above, and will not be repeated here. The energy storage system provided in this disclosure can be used on the grid side for peak shaving, frequency regulation, and grid congestion relief, or on the user side, such as for energy storage in microgrids, homes, and businesses, to improve energy utilization efficiency and power supply reliability.

[0137] Exemplary embodiments of this disclosure will now be described in more detail. While exemplary embodiments of this disclosure are described below, it should be understood that this disclosure can be implemented in various forms and should not be limited to the embodiments set forth herein. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with techniques or conditions described in the literature in the art or according to product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0138] Example 1

[0139] Example 1 provides a sodium-ion battery, comprising: a positive electrode, a negative electrode, a separator located between the positive and negative electrodes, and an electrolyte. The positive electrode comprises a current collector aluminum foil, a positive electrode active material layer attached to the surface of the current collector aluminum foil, and a modified coating attached to the surface of the positive electrode active material layer. The positive electrode active material layer comprises 90% NaNi by mass. 1 / 3 Fe 1 / 3Mn 1 / 3 The O2 material comprises 5% Ketjen black and 5% polyvinylidene fluoride by mass. The modified coating comprises 90% sodium ion exchange resin and 10% polyvinylidene fluoride by mass, with a thickness of 0.5 μm. The negative electrode comprises: a current collector copper foil and a negative electrode active material layer attached to the surface of the current collector copper foil, wherein the negative electrode active material layer comprises 90% hard carbon material, 5% Ketjen black, and 5% polyvinylidene fluoride by mass.

[0140] The relevant information of the sodium ion exchange resin used in Example 1 is as follows: its resin backbone is a polystyrene-type resin, and the structural formula of its active groups is as follows:

[0141]

[0142] Typically, sodium ion exchange resin particles are relatively large and contain a high water content. Therefore, they need to be ball-milled and dried before use. This includes: ball-milling sodium ion exchange resin, ethanol, and zirconium beads in a planetary ball mill for 4 hours, drying to remove ethanol, and then grinding to make the particle size of sodium ion exchange resin 0.5mm-1mm. The ground sodium ion exchange resin is then further dried under vacuum and heated for later use. The total exchange capacity of the sodium ion exchange resin is ≥3mmol / g.

[0143] The positive electrode of a sodium-ion battery is prepared by the following method: a positive electrode active material layer is pre-prepared on the surface of a current collector aluminum foil. Sodium ion exchange resin, polyvinylidene fluoride, and N-methylpyrrolidone are mixed uniformly according to a specified ratio, pre-mixed by ultrasonication, and then stirred ultrasonically for 1 hour to form a slurry. The slurry is then coated onto the surface of the pre-prepared positive electrode active material layer using a 10-micron doctor blade, dried in a vacuum oven at 60°C for 4 hours, and then dried in a vacuum oven at 100°C for 12 hours to form a modified coating on the surface of the positive electrode active material layer.

[0144] Example 2

[0145] The difference between Example 2 and Example 1 is that the thickness of the modified coating is 1 μm, while the rest is the same as in Example 1.

[0146] Example 3

[0147] The difference between Example 3 and Example 1 is that the thickness of the modified coating is 2 μm, while the rest is the same as in Example 1.

[0148] Example 4

[0149] The difference between Example 4 and Example 1 is that the positive electrode active material is Na4Fe3(PO4)2P2O7, while the rest are the same as in Example 1.

[0150] Example 5

[0151] The difference between Example 5 and Example 1 is that the active groups of the sodium ion exchange resin have the chemical formula shown below, while the rest are the same as in Example 1.

[0152]

[0153] Comparative Example 1

[0154] The difference between Comparative Example 1 and Example 1 is that the positive electrode does not contain a modified coating, while the rest is the same as Example 1.

[0155] Comparative Example 2

[0156] The difference between Comparative Example 2 and Example 4 is that the positive electrode does not contain a modified coating, while the rest is the same as Example 4.

[0157] Test Example 1

[0158] Test Example 1 conducted performance tests on the sodium-ion batteries provided in Examples 1-3 and Comparative Example 1, as detailed below.

[0159] Firstly, the infrared spectra of the positive electrode of the sodium-ion battery provided in Comparative Example 1, Example 1, and the positive electrode of the sodium-ion battery provided in Example 1 were tested in the initial state, in the state after 10 cycles at 25°C, and in the state after 10 cycles at 60°C. The test results are shown in [reference needed]. Figure 9 .like Figure 9 As shown, the infrared spectra of Example 1 all exhibit characteristic peaks for styrene sulfonic acid (R-SO3H), sodium carbonate (Na2CO3), and carbonate (ROCOOR). These substances are all reaction products of the sodium ion exchange resin with protons, indicating that the sodium ion exchange resin participates in proton exchange. Therefore, compared to Comparative Example 1, the sodium ion exchange resin in the cathode provided in Example 1 can capture free H+ in the electrolyte during battery cycling. + Furthermore, its properties remain unchanged, and the modified coating remains stable even after battery cycling.

[0160] Secondly, the cycle performance of the sodium-ion batteries provided in Examples 1, 2, 3, and Comparative Example 1 was tested at an operating temperature of 25°C and under different charge / discharge rates. The test results are shown in [reference needed]. Figure 10 and Figure 11 And Table 1, in which, Figure 10 The data from Example 2 and Example 3 are quite similar, resulting in their test curves almost overlapping. Figure 11 The data for Examples 1-3 and Comparative Example 1 are shown to be quite similar, resulting in their test curves almost overlapping. The specific data can be found in Table 1. It can be seen that Examples 1-3 exhibit better capacity retention and improved battery cycle performance compared to Comparative Example 1.

[0161] Table 1

[0162]

[0163] Thirdly, the cycle performance of the sodium-ion batteries provided in Examples 1, 2, 3, and Comparative Example 1 was tested at an operating temperature of 60°C and under different charge / discharge rates. The test results are shown in [reference needed]. Figure 12 and Figure 13 And Table 2. Among them, Figure 12 The data from Examples 1-3 are shown to be quite similar, resulting in their test curves almost overlapping. Figure 13 The data from Examples 1-3 are quite similar, resulting in a high degree of overlap in their test curves. For specific data, please refer to Table 2. It can be seen that Examples 1-3 exhibit better capacity retention than Comparative Example 1, and the improvement in capacity retention is more significant at high temperatures, which significantly improves the high-temperature cycling performance of the battery.

[0164] Table 2

[0165]

[0166] Fourth, the sodium-ion batteries provided in Examples 2, 3, and 4, as well as Comparative Examples 1 and 2, were cycled 200 times at operating temperatures of 25°C and 60°C, respectively. Their initial capacity and remaining capacity were measured, and the percentage of remaining capacity to initial capacity was defined as the capacity retention rate. The test results are shown in Table 3. It can be seen that the sodium-ion batteries provided in the above examples show improved capacity retention rates under both room temperature and high temperature conditions compared to the sodium-ion batteries provided in the comparative examples. The improvement in capacity retention rate is particularly significant at high temperatures. Experiments have confirmed that the improvement in capacity retention rate is more pronounced with increasing cycle time (e.g., when the number of cycles exceeds 200).

[0167] Table 3

[0168] project 60℃ retention rate 25℃ retention rate Example 2 76.4％ 80.1％ Example 3 76.6％ 80.9％ Example 5 76.3％ 80.0％ Comparative Example 1 62.1％ 79.5％ Example 4 95.5％ 98.4％ Comparative Example 2 93.9％ 97.4％

[0169] Fifth, the NFM-NFM symmetrical cell impedance of the sodium-ion batteries provided in Examples 1, 2, and Comparative Example 1 was tested. In these examples, the negative electrode of each sodium-ion battery was set to be the same as its positive electrode to form a symmetrical cell. The operating temperatures were 25°C and 60°C, respectively. The test results are shown below. Figure 14 and Figure 15 ,in, Figure 14 and Figure 15 The x-coordinate Z in Re The real part of the impedance is represented by the ordinate -Z. im This represents the imaginary part of the impedance. It is evident that the presence of the modified coating does not significantly affect the interfacial impedance, meaning that the presence of the sodium ion exchange resin does not affect the basic performance of the battery.

[0170] Sixth, the dissolution of positive electrode transition metals in the electrolytes of sodium-ion batteries provided in Example 1 and Comparative Example 1 was tested. The test results are shown in Table 4. As can be seen from Table 4, compared with Comparative Example 1, the dissolution of positive electrode transition metal ions from hydrolysis byproducts in Example 1 was significantly reduced.

[0171] Example 6

[0172] Example 6 provides a sodium-ion battery, comprising: a positive electrode, a negative electrode, a separator located between the positive and negative electrodes, and an electrolyte, wherein the positive electrode comprises a current collector aluminum foil and a positive electrode active material layer attached to the surface of the current collector aluminum foil, the positive electrode active material layer comprising the following components in the indicated mass percentages: 95.5% NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 The material consists of O2, 2.8% graphite, 1.5% polyvinylidene fluoride, and 0.2% sodium ion exchange resin, the same as that used in Example 1. The negative electrode comprises: a current collector copper foil and a negative electrode active material layer attached to the surface of the current collector copper foil, wherein the negative electrode active material layer comprises 95% hard carbon material, 3% graphite, and 2% polyvinylidene fluoride by mass.

[0173] The positive electrode of a sodium-ion battery is prepared by the following method: a positive electrode active material layer is pre-prepared on the surface of a current collector aluminum foil. NaNi... 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 material, sodium ion exchange resin, polyvinylidene fluoride, and graphite were dissolved in N-methylpyrrolidone and stirred for 6 hours to form a mixed slurry. The mixed slurry was then coated onto the surface of the current collector aluminum foil using a doctor blade and dried in a vacuum oven at 100°C for 6 hours to prepare the positive electrode.

[0174] Example 7

[0175] The difference between Example 7 and Example 6 is that the positive electrode active material is Na4Fe3(PO4)2P2O7, while the rest are the same as in Example 6.

[0176] Example 8

[0177] The difference between Example 8 and Example 6 is that the sodium ion exchange resin used is the same as that used in Example 5, while the rest is the same as in Example 6.

[0178] Comparative Example 3

[0179] The difference between Comparative Example 3 and Example 6 is that the positive electrode active material layer does not contain sodium ion exchange resin, and the positive electrode active material layer comprises the following components in the indicated mass percentages: 95% NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 material, 3% graphite, 2% polyvinylidene fluoride.

[0180] Comparative Example 4

[0181] The difference between Comparative Example 4 and Example 7 is that the positive electrode active material layer does not contain sodium ion exchange resin, and the positive electrode active material layer comprises the following components in the following mass percentages: 95% Na4Fe3(PO4)2P2O7 material, 3% graphite, and 2% polyvinylidene fluoride.

[0182] Test Example 2

[0183] Test Example 2 involved the sodium-ion batteries provided in Examples 6 and 7, and Comparative Examples 3 and 4. These batteries were cycled 200 times at operating temperatures of 25°C and 60°C, respectively. The initial capacity and remaining capacity were measured, and the capacity retention rate was obtained based on the percentage of remaining capacity to initial capacity. The test results are shown in Table 4. It can be seen that, compared to the sodium-ion batteries provided in the comparative examples, the sodium-ion batteries provided in the above examples exhibit improved capacity retention rates at both room temperature and high temperatures.

[0184] Table 4

[0185] project 60℃ retention rate 25℃ retention rate Comparative Example 3 74.3％ 78.1％ Example 6 74.6％ 78.6％ Example 8 74.5％ 78.4％ Comparative Example 4 96.5％ 98.6％ Example 7 97.9％ 98.9％

[0186] The above description is only for the purpose of enabling those skilled in the art to understand the technical solutions disclosed herein, and is not intended to limit the scope of this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A sodium-ion battery, characterized in that, The sodium-ion battery includes: a positive electrode, a negative electrode, a separator located between the positive electrode and the negative electrode, and an electrolyte; At least one of the positive electrode and the negative electrode contains a sodium ion exchange resin.

2. The sodium-ion battery according to claim 1, characterized in that, Both the positive electrode and the negative electrode include: a current collector and an active material layer attached to the surface of the current collector; At least one of the positive electrode and the negative electrode further includes a modified coating attached to the surface of the active material layer, the modified coating comprising the sodium ion exchange resin.

3. The sodium-ion battery according to claim 2, characterized in that, The positive electrode active material layer includes a positive electrode active material, a first conductive agent, and a first binder. The positive electrode active material includes at least one of layered transition metal oxides, polyanionic compounds, and Prussian blue compounds.

4. The sodium-ion battery according to claim 2, characterized in that, The active material layer of the negative electrode includes a negative electrode active material, a second conductive agent, and a second binder. The negative electrode active material includes at least one of graphite, amorphous carbon, hard carbon, soft carbon, alloy materials, titanium-based compounds, and molybdenum-based compounds.

5. The sodium-ion battery according to any one of claims 2-4, characterized in that, The modified coating further includes a third binder, wherein the sodium ion exchange resin constitutes 60%-99.5% of the modified coating by mass, and the third binder constitutes 0.5%-40% of the modified coating by mass.

6. The sodium-ion battery according to any one of claims 2-5, characterized in that, The thickness of the modified coating is 0.01μm-10μm.

7. The sodium-ion battery according to claim 1, characterized in that, Both the positive electrode and the negative electrode include: a current collector and an active material layer attached to the surface of the current collector; The active material layer of at least one of the positive electrode and the negative electrode includes the sodium ion exchange resin.

8. The sodium-ion battery according to claim 7, characterized in that, The positive electrode active material layer includes a positive electrode active material, a first conductive agent, and a first binder. The positive electrode active material includes at least one of layered transition metal oxides, polyanionic compounds, and Prussian blue compounds.

9. The sodium-ion battery according to claim 7, characterized in that, The active material layer of the negative electrode includes a negative electrode active material, a second conductive agent, and a second binder. The negative electrode active material includes at least one of graphite, amorphous carbon, hard carbon, soft carbon, alloy materials, titanium-based compounds, and molybdenum-based compounds.

10. The sodium-ion battery according to any one of claims 7-9, characterized in that, The sodium ion exchange resin accounts for 0.1%-1% of the mass of the active material layer.

11. The sodium-ion battery according to any one of claims 1-10, characterized in that, The sodium ion exchange resin includes a resin skeleton and active groups located on the resin skeleton; The active group is -RSO3Na or -RCOONa, wherein the R group is a single bond, an alkyl subunit, or an unsaturated hydrocarbon subunit.

12. The sodium-ion battery according to claim 11, characterized in that, The resin skeleton includes polystyrene resin, polyacrylic resin, or phenolic resin.

13. A positive electrode plate, characterized in that, The positive electrode sheet includes a positive current collector, a positive active material layer attached to the surface of the positive current collector, and a modified coating attached to the surface of the positive active material layer, wherein the modified coating includes a sodium ion exchange resin.

14. A positive electrode plate, characterized in that, The positive electrode includes a positive current collector and a positive active material layer attached to the surface of the positive current collector, wherein the positive active material layer contains sodium ion exchange resin.

15. A negative electrode sheet, characterized in that, The negative electrode sheet includes a negative current collector, a negative active material layer attached to the surface of the negative current collector, and a modified coating attached to the surface of the negative active material layer, wherein the modified coating includes a sodium ion exchange resin.

16. A negative electrode sheet, characterized in that, The negative electrode sheet includes a negative current collector and a negative active material layer attached to the surface of the negative current collector, wherein the negative active material layer contains sodium ion exchange resin.

17. A battery module, characterized in that, The battery module includes a housing and a plurality of batteries housed inside the housing. At least some of the batteries are sodium-ion batteries as described in any one of claims 1-12, or at least some of the batteries include a positive electrode as described in any one of claims 13-14, or at least some of the batteries include a negative electrode as described in any one of claims 15-16.

18. An electrical appliance, characterized in that, The electrical equipment includes a battery pack and an electric actuator, the battery pack including a plurality of battery modules as described in claim 17, the battery pack being used to provide electrical energy to the electric actuator.

19. An energy storage system, characterized in that, The energy storage system includes: a battery pack and a power converter, wherein the battery pack includes a plurality of battery modules as described in claim 17; The power converter is used to convert the voltage output by the battery pack into power and output it to the power grid or load, and / or to convert the voltage output by an external power source into power and output it to the battery pack.

Images