Sodium supplementing material, preparation method therefor, positive electrode plate, and sodium-ion battery

Abstract

A sodium supplementing material, a preparation method therefor, a positive electrode plate, and a sodium-ion battery. The sodium supplementing material comprises a sodium supplementing agent body, and first particles exposed on the surface of the sodium supplementing agent body. In any 300 nm x 200 nm region of the surface of the sodium supplementing material, there are 2-20 first particles, and the first particles comprise conductive agent particles and catalyst particles.

Description

Sodium-supplementing materials and their preparation methods, positive electrode sheets, sodium-ion batteries

[0001] Cross-references

[0002] This disclosure claims priority to Chinese Patent Application No. 202410916800.1, filed on July 9, 2024, entitled "Sodium Supplement Material and Preparation Method Thereof, Positive Electrode Sheet, Sodium-ion Battery", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of electrochemical technology, and in particular to a sodium-supplementing material and its preparation method, a positive electrode sheet, and a sodium-ion battery. Background Technology

[0004] Sodium-ion batteries, with their advantages of low cost, abundant sodium resources, and relatively high energy density, are expected to replace traditional lithium-ion batteries in the field of energy storage.

[0005] Adding sodium to the positive electrode using a sodium replenishing agent can reduce the adverse effects of sodium loss on the electrochemical performance of sodium-ion batteries. Organic sodium replenishing agents are environmentally friendly, low-cost, and non-toxic. Therefore, how to reduce the oxidative decomposition potential of organic sodium replenishing materials to improve their sodium replenishment effect in sodium-ion batteries has become an urgent technical problem to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, this disclosure provides a sodium-replenishing material and its preparation method, a positive electrode sheet, and a sodium-ion battery, thereby improving the sodium-replenishing effect of the sodium-replenishing material and thus enhancing the performance of the sodium-ion battery.

[0007] In a first aspect, this disclosure provides a sodium-supplementing material, comprising a sodium-supplementing agent body and first particles exposed on the surface of the sodium-supplementing agent body. In any 300nm×200nm region on the surface of the sodium-supplementing material, the number of the first particles is between 2 and 20, and the first particles include conductive agent particles and catalyst particles.

[0008] Secondly, this disclosure provides a method for preparing the sodium-supplementing material as described in the first aspect, comprising the following steps:

[0009] The sodium supplement raw material after particle size control treatment is mixed with conductive agent particles and catalyst particles to obtain a mixture, wherein the average particle size D50 of the sodium supplement raw material after particle size control treatment is 0.3μm~2.0μm;

[0010] The mixture was calcined in a gaseous atmosphere at a temperature of 300℃ to 500℃ for 1 to 8 hours to obtain the sodium-supplementing material.

[0011] Thirdly, this disclosure provides a positive electrode sheet, including a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, wherein the positive active material layer includes a sodium-supplementing material as described in the first aspect, or includes a sodium-supplementing material prepared by the preparation method described in the second aspect.

[0012] Fourthly, this disclosure provides a sodium-ion battery, the sodium-ion battery comprising the positive electrode sheet described in the third aspect.

[0013] Fifthly, this disclosure provides an energy storage device, including a housing and at least one sodium-ion battery as described in the fourth aspect, the sodium-ion battery being housed within the housing.

[0014] In a sixth aspect, this disclosure provides an electrical appliance including the energy storage device described in the fifth aspect, wherein the energy storage device supplies power to the electrical appliance.

[0015] Compared with the prior art, this disclosure has at least the following beneficial effects:

[0016] This disclosure provides a sodium-supplementing material and its preparation method, a positive electrode sheet, and a sodium-ion battery. The sodium-supplementing material includes a sodium-supplementing agent body and first particles exposed on the surface of the sodium-supplementing agent body. Within any 300nm × 200nm region on the surface of the sodium-supplementing material, the number of first particles ranges from 2 to 20. The first particles include conductive agent particles and catalyst particles. The sodium-supplementing material with the above characteristics shortens the electron transport distance between the conductive agent and the sodium-supplementing agent body, thereby improving the electron utilization rate of the sodium-supplementing agent body. It also enhances the catalytic effect of the catalyst. Under these combined effects, the oxidative decomposition process of the sodium-supplementing agent body is promoted, resulting in a lower oxidative decomposition potential for the sodium-supplementing material of this disclosure. This improves the initial sodium-supplementing effect of the sodium-supplementing material and enhances the energy density and cycle performance of the sodium-ion battery. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 is a scanning electron microscope (SEM) image of the sodium supplement material prepared in Example 1 of this disclosure.

[0019] Figure 2 is a schematic diagram of the structure of a residential energy storage system according to one embodiment of this disclosure.

[0020] Figure 3 is a schematic diagram of the structure of an energy storage system according to one embodiment of the present disclosure.

[0021] Figure 4 shows the first charge-discharge curve of the first button cell in Example 1.

[0022] Figure 5 shows the first charge-discharge curve of the first coin cell in Comparative Example 1.

[0023] Figure 6 shows the first charge-discharge curve of the second coin cell in Example 1.

[0024] Figure 7 shows the first charge-discharge curve of the second coin cell in Comparative Example 1.

[0025] Explanation of reference numerals in the attached drawings: 1-Energy storage device, 2-Power conversion device, 3-First user load, 4-Second user load, 400-Energy storage system, 410-High voltage cable, 420-First power conversion device, 430-Second power conversion device. Detailed Implementation

[0026] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0027] In this disclosure, the terms “upper,” “lower,” “left,” “right,” “front,” “rear,” “top,” “bottom,” “inner,” “outer,” “vertical,” “horizontal,” “lateral,” and “longitudinal” indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. These terms are primarily for the purpose of better describing this disclosure and its embodiments and are not intended to limit the indicated devices, elements, or components to having a specific orientation or to be constructed and operated in a specific orientation.

[0028] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in certain circumstances to indicate a dependency or connection. Those skilled in the art can understand the specific meaning of these terms in this disclosure according to the specific circumstances.

[0029] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection via an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this disclosure according to the specific circumstances.

[0030] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, elements, or components (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, elements, or components. Unless otherwise stated, "a plurality of" means two or more.

[0031] It should be noted that this disclosure uses sodium-ion batteries as an example of secondary batteries to explain this disclosure, but the secondary batteries in this disclosure are not limited to sodium-ion batteries.

[0032] Currently, in composite sodium-supplementing materials, the sodium-supplementing agent, conductive agent, and catalyst are usually connected through a simple physical mixing method. When such sodium-supplementing materials are added to the positive electrode active material, the sodium-supplementing agent, conductive agent, and catalyst will separate, which greatly affects the effect of the conductive agent and catalyst on the sodium-supplementing agent and limits the actual sodium-supplementing effect of the sodium-supplementing material.

[0033] In view of this, the present disclosure provides a sodium-supplementing material, comprising a sodium-supplementing agent body and first particles exposed on the surface of the sodium-supplementing agent body. Within any 300nm × 200nm region on the surface of the sodium-supplementing material, the number of first particles ranges from 2 to 20, for example, the number of first particles can be 2, 3, 5, 7, 9, 10, 12, 14, 15, 16, 18, or 20. The first particles include conductive agent particles and catalyst particles.

[0034] In this disclosure, the sodium-supplementing material can be observed using a scanning electron microscope at a magnification of 10k to 20k. The 300nm × 200nm region can be any pre-selected area on the surface of the sodium-supplementing material; for example, referring to Figure 1, it can be a rectangular region of 300nm × 200nm. Without being limited to any theory, when the number of first particles exposed on the surface of the sodium-supplementing agent is too small (e.g., less than 2), the conductivity and catalytic activity of the sodium-supplementing material decrease, which is detrimental to reducing the oxidative decomposition potential of the sodium-supplementing material. When the number of first particles exposed on the surface of the sodium-supplementing agent is too large (e.g., more than 20), the relative content of conductive agent particles and catalyst particles is too high, while the relative content of the sodium-supplementing agent itself is too low, which is also detrimental to improving the sodium-supplementing effect of the sodium-supplementing material. This disclosure, by controlling the number of the first particle within the aforementioned range, enables the conductive agent particles to promote electron transport into the sodium replenishment substrate, thereby shortening the electron transport distance between the conductive agent particles and the sodium replenishment substrate and improving the utilization rate of electrons in the sodium replenishment substrate. Furthermore, the addition of conductive agent particles enhances the conductivity of the catalyst particles, thereby improving the catalytic effect of the catalyst and further reducing the oxidation decomposition potential of the sodium replenishment material. Under the combined effect of these factors, the oxidation decomposition process of the sodium replenishment substrate is promoted, resulting in a lower oxidation decomposition potential for the sodium replenishment material of this disclosure. This improves the initial sodium replenishment effect of the sodium replenishment material and enhances the energy density and cycle performance of the sodium-ion battery.

[0035] In some embodiments of this disclosure, the first particle is partially coated with a sodium supplement body, which is formed by melting and cooling a sodium supplement raw material. The melting points of the conductive agent and catalyst in this disclosure are higher than those of the sodium supplement raw material. After the sodium supplement raw material melts, it solidifies and precipitates during cooling and solidification, using the conductive agent particles as a framework, thus forming the sodium supplement body. This allows a portion of the first particle (including conductive agent particles and catalyst particles) to be embedded in the sodium supplement body, while another portion is exposed on the surface of the sodium supplement body. In other words, the first particle is partially coated with the sodium supplement body, shortening the electron transport distance between the conductive agent particles and the sodium supplement body. Furthermore, in the sodium replenishment material disclosed herein, the conductive agent particles and catalyst particles can exist stably within the sodium replenishment material structure, rather than being dispersed in the positive electrode active material. Compared to the sodium replenishment material formed by simply mixing the sodium replenishing agent, conductive agent, and catalyst in the traditional method, the sodium replenishment material disclosed herein can significantly improve the effective utilization rate of the conductive agent and catalyst in the sodium replenishment material, promote the oxidative decomposition process of the sodium replenishing agent, and make the sodium replenishment material disclosed herein have a lower oxidative decomposition potential, which is beneficial to improving the first-cycle sodium replenishment effect of the sodium replenishment material.

[0036] In some embodiments of this disclosure, the sodium-supplementing material includes a sodium-supplementing agent body, conductive agent particles, and catalyst particles. Based on the mass of the sodium-supplementing material, the mass percentage of the sodium-supplementing agent body is 40% to 80%, for example, 40%, 50%, 60%, 70%, or 80%; the mass percentage of the conductive agent particles is 5% to 40%, for example, 5%, 20%, 30%, or 40%; and the mass percentage of the catalyst particles is 5% to 20%, for example, 5%, 10%, 15%, or 20%. By controlling the mass ratio of the sodium-supplementing agent body, conductive agent particles, and catalyst particles in the sodium-supplementing material within the above-mentioned ranges, it is advantageous that the number of conductive agent particles and catalyst particles exposed on the surface of the sodium-supplementing agent body during the formation of the sodium-supplementing material is within the range of this disclosure, thereby forming a sodium-supplementing material having the structure of this disclosure.

[0037] In some embodiments of this disclosure, the average particle size D50 of the sodium-supplementing material is 0.7 μm to 2.0 μm, where D50 represents the particle size corresponding to a cumulative particle size volume distribution percentage of 50%. For example, the average particle size D50 of the sodium-supplementing material is 0.7 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.5 μm, 1.7 μm, or 2.0 μm. By controlling the D50 of the sodium-supplementing material within the above range, the electron transport distance between the sodium-supplementing material particles can be effectively shortened, further promoting the oxidative decomposition process of the sodium-supplementing agent and contributing to a reduction in the oxidative decomposition potential of the sodium-supplementing material.

[0038] In some embodiments of this disclosure, the diameter of the portion of the first particle exposed on the surface of the sodium supplement body is 10 nm to 70 nm. For example, the diameter of the portion of the first particle exposed on the surface of the sodium supplement body is 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, or 70 nm. The inventors have discovered that by controlling the diameter of the portion of the first particle exposed on the surface of the sodium supplement body within the above-mentioned range, it is possible to maintain the conductive agent particles and catalyst particles within a smaller particle size range to improve the coating effect, and also to increase the utilization rate of the conductive agent and catalyst in the sodium supplement material, thereby promoting the oxidative decomposition process of the sodium supplement body.

[0039] In this disclosure, the portion of the first particle exposed on the surface of the sodium supplement body (hereinafter referred to as the exposed portion) is not limited to a geometric circle. When the exposed portion is not a geometric circle, the diameter of the exposed portion is defined as the maximum length of the exposed portion in the horizontal direction in the SEM image of the sodium supplement material.

[0040] In some embodiments of this disclosure, the catalyst particles are made of at least one of titanium dioxide, manganese dioxide, tin dioxide, ruthenium dioxide, molybdenum dioxide, manganese oxide, zirconium dioxide, cobalt tetroxide, and manganese tetroxide. The above-mentioned catalysts are beneficial in reducing the oxidative decomposition potential of the sodium-replenishing material, thereby improving the initial sodium replenishment effect of the sodium-replenishing material.

[0041] In some embodiments of this disclosure, the sodium supplement body is made of at least one of Na2C4O4, Na2CO3, CH3COONa, C6H5Na3O7, Na2C2O4, and Na2C6O6. The above-mentioned sodium supplement is an organic sodium supplement, which has the advantages of being environmentally friendly, widely available, and safe and non-toxic.

[0042] In some embodiments of this disclosure, the conductive agent particles are made of at least one of conductive carbon black, carbon nanotubes (CNTs), Ketjen black (KB), acetylene black (ACET), graphene, graphene oxide, and reduced graphene oxide (rGO). These conductive agents possess good conductivity and a large specific surface area, enabling them to act as a framework during the cooling process of the molten sodium supplement material. This improves the electronic conductivity of the sodium supplement material, promotes electron transport on the surface of the sodium supplement material, and helps reduce the oxidative decomposition potential of the sodium supplement material.

[0043] Secondly, this disclosure provides a method for preparing the sodium-supplementing material as described in the first aspect, comprising the following steps:

[0044] Step A: Mix the sodium supplement raw material after particle size control treatment with conductive agent particles and catalyst particles to obtain a mixture. The average particle size D50 of the sodium supplement raw material after particle size control treatment is 0.3μm to 2.0μm, for example, D50 is 0.3μm, 0.5μm, 0.8μm, 1.0μm, 1.5μm or 2.0μm.

[0045] Step B: Calcine the mixture in a gaseous atmosphere at a temperature of 300℃ to 500℃, preferably 400℃ to 500℃, for example, 300℃, 350℃, 400℃, 450℃ or 500℃; calcination time is 1h to 8h, preferably 4h to 6h, for example, 1h, 4h, 5h, 6h or 8h; after cooling, the sodium-supplementing material is obtained.

[0046] In step A, the sodium supplement raw material within the aforementioned particle size range can be obtained by controlling the particle size of the sodium supplement raw material. As the particle size of the sodium supplement raw material decreases, its specific surface area increases accordingly. When mixed with conductive agent particles and catalyst particles, this facilitates a more uniform distribution of the conductive agent particles and catalyst particles on the surface of the sodium supplement raw material. Consequently, during the subsequent calcination process, the conductive agent particles and catalyst particles can be more uniformly distributed in the molten sodium supplement raw material. Furthermore, during the cooling and solidification process of the sodium supplement raw material, the conductive agent particles and catalyst particles can be more uniformly distributed and exposed on the surface of the solidified sodium supplement body, which is beneficial for improving the sodium supplementation performance of the sodium supplement material.

[0047] This disclosure allows for the control of the particle size of sodium supplement raw materials through treatment methods such as recrystallization, ball milling, crushing, or spray drying; no particular limitations are specified. Commercially available sodium supplement raw materials often have a large particle size; particle size control treatment can effectively reduce the particle size of these raw materials.

[0048] In step B of this disclosure, adjusting the calcination temperature and calcination time within the above-mentioned range enables the sodium supplement raw material to melt but the conductive agent particles and catalyst particles to remain unmelted, which is beneficial for forming a sodium supplement material with the structure of this disclosure.

[0049] This disclosure does not impose any particular limitation on the method of controlling the number of the first particles exposed on the surface of the sodium supplement body, as long as the purpose of this disclosure can be achieved. For example, the number of the first particles exposed on the surface of the sodium supplement body can be controlled by adjusting the content of conductive agent particles and catalyst particles and / or by adjusting the calcination temperature.

[0050] In some embodiments of this disclosure, during the calcination process, the sodium supplement raw material melts, and the conductive agent particles and catalyst particles are dispersed in the molten sodium supplement raw material; during the cooling process, the sodium supplement raw material solidifies and precipitates with the conductive agent particles as the skeleton to form the sodium supplement body, and part of the conductive agent particles and catalyst particles are embedded in the sodium supplement body, while the other part is exposed on the surface of the sodium supplement body.

[0051] Through the calcination and cooling process of this disclosure, the molten sodium supplement raw material can solidify and precipitate with conductive agent particles as the skeleton during the cooling and solidification process, thereby forming a sodium supplement body. Part of the conductive agent particles and catalyst particles are embedded in the sodium supplement body, while the other part is exposed on the surface of the sodium supplement body, thereby forming a sodium supplement material with the structure of this disclosure. The obtained sodium supplement material has a lower oxidation decomposition potential.

[0052] The method for preparing sodium-supplementing materials disclosed herein is simple in process, uses non-toxic and safe raw materials, and produces sodium-supplementing materials with excellent sodium-supplementing performance and low cost, thereby improving the energy density and cycle performance of sodium-ion batteries while reducing the production cost of sodium-ion batteries.

[0053] This disclosure also provides a positive electrode sheet, including a current collector and a positive electrode active material layer disposed on at least one surface of the current collector, wherein the positive electrode active material layer includes the sodium-supplementing material described in any of the above embodiments, or includes the sodium-supplementing material prepared by the preparation method described in any of the above embodiments.

[0054] The positive electrode active material layer of this disclosure can be disposed on one or both surfaces of the positive electrode current collector in the thickness direction. In this disclosure, the positive electrode active material layer is disposed on the surface of the positive electrode current collector; that is, the positive electrode active material layer can be disposed on a portion of one surface of the positive electrode current collector, or it can be disposed on the entire surface of one surface of the positive electrode current collector. This disclosure does not impose any particular limitation on the positive electrode current collector, as long as it achieves the purpose of this disclosure, such as aluminum foil, aluminum alloy foil, or composite current collectors. In this disclosure, there is no particular limitation on the thickness of the positive electrode current collector, as long as it achieves the purpose of this disclosure, such as a thickness of 8 μm to 13 μm. The thickness of the positive electrode active material layer of this disclosure can be 150 μm to 400 μm.

[0055] In this disclosure, the positive electrode active material layer also includes a positive electrode active material. This disclosure does not impose any particular limitation on the positive electrode active material, as long as it can achieve the purpose of this disclosure. For example, it may include at least one of sodium nickel manganate, sodium nickel iron manganate, sodium iron sulfate, sodium vanadium phosphate, sodium copper iron manganate, sodium iron pyrophosphate, and sodium iron pyrophosphate.

[0056] In this disclosure, the positive electrode active material layer may further include a positive electrode conductive agent. This disclosure does not impose any particular limitation on the positive electrode conductive agent, as long as it achieves the purpose of this disclosure. For example, it may include, but is not limited to, at least one of conductive carbon black (Super P), carbon nanotubes (CNT), Ketjen black (KB), graphene, graphene oxide, and acetylene black. The mass percentage of the conductive agent in the positive electrode active material layer is 10% to 40%. In this disclosure, the positive electrode active material layer may further include a positive electrode binder. This disclosure does not impose any particular limitation on the positive electrode binder, as long as it achieves the purpose of this disclosure. For example, it may include, but is not limited to, at least one of fluorinated resins, polypropylene resins, fiber-type binders, rubber-type binders, polyimide-type binders, and polyvinylidene fluoride (PVDF).

[0057] This disclosure also provides a sodium-ion battery, including the positive electrode sheet described in any of the above embodiments.

[0058] The sodium-ion battery disclosed herein also includes a negative electrode, a separator, and an electrolyte, wherein the separator is located between the positive and negative electrodes and serves as a separator.

[0059] This disclosure does not impose any particular limitation on the negative electrode sheet, as long as it achieves the purpose of this disclosure. For example, the negative electrode sheet typically includes a negative current collector and a negative active material layer. The negative active material layer can be disposed on the surface of the negative current collector, that is, the negative active material layer can be disposed on a portion of a surface of the negative current collector, or it can be disposed on the entire surface of a surface of the negative current collector. This disclosure does not impose any particular limitation on the negative current collector, as long as it achieves the purpose of this disclosure. For example, it can include, but is not limited to, copper foil, copper alloy foil, nickel foil, or composite current collectors. In this disclosure, there is no particular limitation on the thickness of the negative current collector, as long as it achieves the purpose of this disclosure, for example, a thickness of 4 μm to 12 μm. The thickness of the negative material layer in this disclosure can be 70 μm to 200 μm.

[0060] In this disclosure, the negative electrode active material layer may further include a negative electrode binder. This disclosure does not impose any particular limitation on the negative electrode binder, as long as it achieves the purpose of this disclosure. For example, it may include at least one of acrylate, polyamide, polyimide, polyamide-imide, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, and sodium carboxymethyl cellulose.

[0061] In some embodiments, the diaphragm material can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The diaphragm can be a single-layer film or a multi-layer composite film, without particular limitation. When the diaphragm is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0062] The sodium-ion battery disclosed herein also includes an electrolyte. This disclosure does not impose any particular limitation on the electrolyte; those skilled in the art can choose according to actual needs, as long as the purpose of this disclosure is achieved. For example, at least one of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl propionate (EP), propyl propionate (PP), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), vinylene carbonate (VC), or fluoroethylene carbonate (FEC) can be mixed in a certain mass or volume ratio to obtain a non-aqueous organic solvent, and then a sodium salt can be added to dissolve and mix evenly. This disclosure does not limit the type of sodium salt, as long as the purpose of this disclosure is achieved. For example, the sodium salt may include at least one of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium trifluoromethanesulfonate, and sodium p-toluenesulfonate. This disclosure does not impose any particular limitation on the concentration of the sodium salt in the electrolyte, as long as the purpose of this disclosure is achieved. For example, the concentration of the sodium salt is 1.0 mol / L to 2.0 mol / L.

[0063] The sodium-ion battery disclosed herein also includes a casing. This disclosure does not impose any particular limitations on the casing; those skilled in the art can choose one according to actual needs, as long as it achieves the purpose of this disclosure. For example, the casing may include an aluminum-plastic film.

[0064] This disclosure does not impose any particular limitation on the preparation method of sodium-ion batteries. Any preparation method known in the art can be used, as long as it can achieve the purpose of this disclosure. For example, the preparation method of sodium-ion batteries includes, but is not limited to, the following steps: stacking the positive electrode, separator, and negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a bare cell with a wound structure; placing the bare cell in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain a sodium-ion battery.

[0065] This disclosure also provides an energy storage device, including a housing and at least one sodium-ion battery as described in any of the above embodiments, the sodium-ion battery being housed within the housing. The energy storage device with this sodium-ion battery exhibits excellent performance, which is beneficial for its use. Housing the battery within the housing increases its stability and protection, thereby extending the lifespan of the energy storage device. It is understood that the energy storage device may contain one or more sodium-ion batteries, and when the energy storage device contains multiple sodium-ion batteries, the multiple sodium-ion batteries can be connected in at least one manner, such as in parallel or in series.

[0066] This disclosure also provides an electrical device including the energy storage device in any of the above embodiments, which is beneficial to improving the product competitiveness and performance of the electrical device. In an optional embodiment, the electrical device includes an electrical device body, and the energy storage device is used to supply power to the electrical device body. In an optional embodiment, the electrical device body includes a positive electrode and a negative electrode, the positive electrode of the sodium-ion battery in the energy storage device is used to electrically connect to the positive electrode of the electrical device body, and the negative electrode of the sodium-ion battery in the energy storage device is used to electrically connect to the negative electrode of the electrical device body, so as to supply power to the electrical device.

[0067] The electrical equipment disclosed herein may include, but is not limited to: containers, household energy storage systems, electric vehicles, electric cars, ships, spacecraft, electric toys, and power tools, etc. Among them, spacecraft include, for example, airplanes, rockets, space shuttles, and spacecraft, etc.; electric toys include, for example, stationary or mobile electric toys, specifically, electric car toys, electric ship toys, and electric airplane toys, etc.; power tools include, for example, metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, specifically, electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers.

[0068] Please refer to Figure 2, which is a structural schematic diagram of a residential energy storage system according to one embodiment of the present disclosure. The embodiment of Figure 2 is illustrated using a residential energy storage scenario in user-side energy storage as an example. The energy storage device disclosed herein is not limited to residential energy storage scenarios.

[0069] This disclosure provides a residential energy storage system, which includes a power conversion device 2 (photovoltaic panel), a first user load 3 (streetlight), a second user load 4 (e.g., household appliances such as air conditioners), and an energy storage device 1. The energy storage device 1 is a small energy storage box that can be wall-mounted to an outdoor wall. Specifically, the photovoltaic panel can convert solar energy into electrical energy during periods of low electricity prices, and the energy storage device 1 is used to store this electrical energy and supply it to streetlights and household appliances during peak electricity prices, or to provide power during power outages / power failures.

[0070] Please refer to Figure 3, which is a structural schematic diagram of an energy storage system 400 according to one embodiment of the present disclosure. The embodiment of Figure 3 is illustrated using a shared energy storage scenario on the generation / distribution side as an example. The energy storage device 1 of the present disclosure is not limited to the energy storage scenario on the generation / distribution side.

[0071] This disclosure provides an energy storage system 400, which includes a high-voltage cable 410, a first power conversion device 420, a second power conversion device 430, and an energy storage device 1 provided in this disclosure. During power generation, the first power conversion device 420 and the second power conversion device 430 convert other forms of energy into electrical energy, which is then connected to the high-voltage cable 410 and supplied to the power consumption side of the distribution network. When the power load is low and the first power conversion device 420 and the second power conversion device 430 generate excess power, the excess power is stored in the energy storage device 1, reducing wind and solar curtailment rates and improving the absorption of new energy power generation. When the power load is high, the power grid issues an instruction to transmit the power stored in the energy storage device 1, along with the high-voltage cable 410, in a grid-connected mode to supply power to the power consumption side. This provides various services for power grid operation, such as peak shaving, frequency regulation, and backup, fully leveraging the peak shaving function of the power grid, promoting peak shaving and valley filling, and alleviating the power supply pressure on the power grid.

[0072] Optionally, the first power conversion device 420 and the second power conversion device 430 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy and mechanical energy into electrical energy.

[0073] The number of energy storage devices 1 can be multiple, and these devices can be connected in series or in parallel. The multiple energy storage devices 1 are supported and electrically connected by an isolation plate (not shown). In this embodiment, "multiple" refers to two or more. An energy storage box can also be provided outside the energy storage device 1 to house it.

[0074] Optionally, the energy storage device 1 may include, but is not limited to, a single cell, a battery module, a battery pack, and a battery system. The single cell may be a sodium-ion battery of this disclosure; the battery module may be a battery module formed by connecting multiple sodium-ion batteries of this disclosure in series or parallel; the battery pack may include multiple sodium-ion batteries of this disclosure; and the battery system may be a charging and discharging system including sodium-ion batteries or a battery pack of this disclosure.

[0075] The actual application of the energy storage device 1 provided in this disclosure can be, but is not limited to, the listed products, and can also be other application forms. This disclosure does not strictly limit the application form of the energy storage device 1. This disclosure only uses a multi-cell battery as an example for illustration. When the energy storage device 1 is a single cell battery, the energy storage device 1 can be at least one of cylindrical batteries, prismatic batteries, etc.

[0076] Example

[0077] The embodiments and comparative examples are given below to illustrate the implementation of the present disclosure in more detail. Various tests and evaluations were conducted according to the methods described below.

[0078] Example 1

[0079] <Preparation of Sodium Supplement Materials>

[0080] 50g of commercially available sodium squartzate (Na2C4O4) powder was added to a crusher for crushing at a speed of 20000 r / min, with a single crushing time of 30 s and a total crushing frequency of 30 times. After sieving, a sodium supplement material with an average particle size D50 of 1 μm was obtained. The obtained sodium supplement material was mixed with conductive carbon black Super P and titanium dioxide (TiO2) catalyst at a mass ratio of 60:20:20 to obtain a mixture. Then, 20g of the mixture was weighed and calcined at 400℃ for 6 h under a nitrogen atmosphere. After crushing and sieving, a sodium supplement material with an average particle size D50 of 0.83 μm was obtained.

[0081] The prepared sodium-supplementing material was observed by SEM at a magnification of 10k. Within any 300nm×200nm region (i.e., per unit area) on the surface of the sodium-supplementing material, the number of particles in the first particle was 6.

[0082] <Preparation of Sodium Supplement Tablets>

[0083] The prepared sodium supplement material, conductive agent Ketjen black (KB), and binder PVDF were mixed at a mass ratio of 60:30:10, and solvent N-methylpyrrolidone (NMP) was added and stirred evenly to obtain a sodium supplement agent slurry with a solid content of 60%. Then, the sodium supplement agent slurry was evenly coated on an aluminum foil with a thickness of 10 μm, with a single-sided coating thickness of 20 μm, and then vacuum dried at 110 °C for 12 h to obtain a sodium supplement agent electrode sheet. The obtained sodium supplement agent electrode sheet was cut into circular pieces with a diameter of 14 μm for use.

[0084] <Preparation of NFPP positive electrode sheet>

[0085] The positive electrode active material Na4Fe3(PO4)2(P2O7) (i.e., NFPP), the prepared sodium supplement material, conductive agent Ketjen black, and binder PVDF were mixed at a mass ratio of 60:20:10:10, and then NMP was added and stirred evenly to obtain a positive electrode slurry with a solid content of 60%. Then, the positive electrode slurry was evenly coated on an aluminum foil with a thickness of 10 μm, with a single-sided coating thickness of 20 μm, and then vacuum dried at 110 °C for 12 h to obtain an NFPP positive electrode sheet. The obtained NFPP positive electrode sheet was cut into circular pieces with a diameter of 14 μm for use.

[0086] <Preparation of electrolyte>

[0087] In an argon atmosphere glove box with a water content ≤ 1 ppm, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 1:1, and then sodium salt NaClO4 was added and dissolved in the above solvent. After mixing evenly, an electrolyte was obtained. Among them, the molar concentration of NaClO4 in the electrolyte was 1 mol / L.

[0088] <Preparation of separator>

[0089] A glass fiber membrane with a thickness of 260 μm was selected as the separator.

[0090] <Assembly of button cell>

[0091] <Assembly of the first button cell>

[0092] A circular sodium sheet with a diameter of 14 μm was used as the counter electrode. The above-prepared circular sodium supplement agent electrode sheet, separator, and circular sodium sheet were stacked in sequence, with the separator placed in the middle between the circular sodium supplement agent electrode sheet and the circular sodium sheet to play an isolation role, and then the prepared electrolyte was injected to assemble the first button cell.

[0093] <Assembly of the second button cell>

[0094] Using a circular sodium sheet with a diameter of 14 μm as the counter electrode, the NFPP positive electrode, the separator, and the circular sodium sheet prepared above are stacked in sequence, with the separator positioned between the NFPP positive electrode and the circular sodium sheet to act as a separator. Then, the prepared electrolyte is injected to assemble a second coin cell.

[0095] Examples 2 to 5

[0096] Except for adjusting the contents of sodium-supplementing agent raw materials, conductive agent and catalyst according to Table 1 in the <Preparation of Sodium Supplementing Material>, the rest is the same as in Example 1.

[0097] Examples 6 to 8

[0098] Except for the section on "Preparation of Sodium Supplement Material", which adjusts the types of raw materials for the sodium supplement according to Table 1, the rest is the same as in Example 1.

[0099] Examples 9 to 11

[0100] Except for adjusting the type of conductive agent according to Table 1 in the <Preparation of Sodium Supplement Material>, the rest is the same as in Example 1.

[0101] Examples 12 to 14

[0102] Except for adjusting the type of catalyst according to Table 1 in the <Preparation of Sodium Supplement Material> section, the rest is the same as in Example 1.

[0103] Examples 15 to 17

[0104] Except for adjusting the calcination temperature and calcination time according to Table 2 in the <Preparation of Sodium Supplement Material>, the rest is the same as in Example 1.

[0105] Comparative Example 1

[0106] Except for using the crushed Na2C4O4 from Example 1 directly as a sodium supplement, everything else is the same as in Example 1.

[0107] Comparative Example 2

[0108] Except for the preparation of sodium supplementation materials, which differs from Example 1, everything else is the same as in Example 1.

[0109] <Preparation of Sodium Supplement Materials>

[0110] Add 50 g of commercially available sodium oxalate (Na2C4O4) powder to a crusher for crushing. The crusher rotates at 20,000 r / min, the single crushing time is 30 s, and the number of crushing times is 30. After particle size regulation and sieving, a sodium supplement agent raw material with an average particle size D50 of 1 μm is obtained. Mix the prepared sodium supplement agent raw material with conductive carbon black Super P and TiO2 catalyst in a mass ratio of 60:20:20 to obtain a mixture, and this mixture is directly used as the sodium supplement material.

[0111] Comparative Example 3

[0112] Do not prepare the sodium supplement material. That is, do not prepare the first coin-type battery, and the NFPP positive electrode sheet does not contain the sodium supplement material, so that the prepared second coin-type battery also does not contain the sodium supplement material. Otherwise, it is the same as Example 1.

[0113] <Preparation of NFPP Positive Electrode Sheet>

[0114] Mix the positive electrode active material NFPP, Ketjen black, and PVDF in a mass ratio of 80:10:10, then add NMP and stir evenly to obtain a positive electrode slurry with a solid content of 60%. Then evenly coat the positive electrode slurry on an aluminum foil with a thickness of 10 μm, and the single-sided coating thickness is 20 μm. Then vacuum dry at 110 °C for 12 h to obtain the NFPP positive electrode sheet. Cut the obtained NFPP positive electrode sheet into circular pieces with a diameter of 14 μm for use.

[0115] Testing methods and equipment:

[0116] Testing the number of the first particles exposed on the surface of the sodium supplement agent body:

[0117] Place the sodium supplement material under SEM and observe it at a magnification of 10k. Select any 5 regions of 300 nm × 200 nm in the field of view, record the number of particles (including conductive agent particles and catalyst particles) exposed on the surface of the sodium supplement agent body in the selected regions, and then take the average value, which is the number of the first particles exposed on the surface of the sodium supplement agent body per unit area. [[ID=q22]]<00002q42>

[0118] Testing the oxidation decomposition potential: [[ID=q26]]

[0119] Use a Blue-Energy (LAND) testing system to perform the first-cycle charge-discharge test on the first coin-type battery to obtain a dQ / dV curve. The oxidation peak of the dQ / dV curve corresponds to the oxidation decomposition reaction of the sodium supplement material, and the potential corresponding to the oxidation peak of the dQ / dV curve is the oxidation decomposition potential of the sodium supplement material.

[0120] Testing the particle size of the material:

[0121] Use a laser particle size analyzer to test the average particle size D50 of the sodium supplement material.

[0122] First charge capacity and first discharge capacity test:

[0123] The test temperature was 25℃. The coin cell battery was charged at a constant current of 0.1C to 4.1V, which is the charging stage. After resting for 10 minutes, it was discharged at a constant current of 0.1C to 2V, and then rested for 10 minutes, which is the discharging stage. The charging capacity of the first charging stage was recorded as the first-cycle charging capacity, in mAh / g; the discharging capacity of the first discharging stage was also recorded as the first-cycle discharging capacity, in mAh / g.

[0124] Cyclic performance test:

[0125] The test temperature was 25℃. The coin cell battery was charged to 4V at a constant current of 0.1C, left to stand for 10 minutes, and then discharged to 2V at 0.1C. The capacity obtained in this step is the initial discharge capacity C. i Perform 20 cycles of 0.1C charge / 0.1C discharge, and record the discharge capacity on the 20th cycle. Cycle capacity retention = (Discharge capacity on the 20th cycle / Initial discharge capacity C) i )×100%.

[0126] Table 1. Preparation parameters of Examples 1-14 and Comparative Examples 1-3

[0127] In Table 1, " / " indicates that no relevant preparation parameters exist.

[0128] Table 2 Preparation parameters for Examples 1, 15-17

[0129] Table 3 Performance data of the first button cell in each embodiment and comparative example

[0130] In Table 3, " / " indicates that no relevant test parameters exist.

[0131] Referring to Tables 1, 2, and 3, and comparing Examples 1 to 17 with Comparative Examples 1 and 2, it can be seen that Comparative Example 1 simply crushes commercially available sodium replenishing agent raw materials, thus lacking the sodium replenishing material structure of this disclosure. Its sodium replenishing material has a high oxidation decomposition potential, resulting in a low first-cycle charging capacity of the first coin cell, making it difficult to improve the first-cycle sodium replenishment effect. Comparative Example 2 simply physically mixes the sodium replenishing agent raw materials, conductive agent, and catalyst. After forming the positive electrode sheet, the conductive agent and catalyst are dispersed in the positive electrode active material. The particles of the positive electrode active material reduce the contact possibility between the conductive agent and catalyst and the sodium replenishing agent, thereby limiting the effect of the conductive agent and catalyst. Its sodium replenishing material also has a high oxidation decomposition potential, and the first-cycle charging capacity of the first coin cell is low, making it equally difficult to improve the first-cycle sodium replenishment effect. In contrast, the sodium replenishing material of this disclosure has a low oxidation decomposition potential, and the first-cycle charging capacity of the first coin cell is significantly improved, indicating that the sodium replenishing material with the structure of this disclosure can effectively improve the first-cycle sodium replenishment effect.

[0132] The type and content of sodium-supplementing raw materials, the type and content of conductive agents, the type and content of catalysts, and the particle size of sodium-supplementing materials generally also affect the performance of sodium-ion batteries. As can be seen from Examples 2 to 14, by adjusting the above parameters within the scope of this disclosure, based on the sodium-supplementing material having the structure of this disclosure, it is beneficial to obtain a sodium-ion battery with a high first-cycle charging capacity.

[0133] Calcination time and temperature typically affect the performance of sodium-ion batteries. As can be seen from Examples 1 and 15-17, based on the structure of the sodium-supplementing material disclosed herein, by controlling the calcination time and temperature within the range of this disclosure, it is beneficial to obtain a sodium-ion battery with high first-cycle charging capacity.

[0134] Figure 1 is a SEM image of the sodium-supplementing material prepared in Example 1. As can be seen from Figure 1, several particles are distributed within a unit area of ​​the sodium-supplementing material (shown by the dashed box). These particles are conductive agent particles and catalyst particles, i.e., the first particles. Part of the first particles is embedded in the sodium-supplementing agent body, while another part is exposed on the surface of the sodium-supplementing agent body, forming a structure in which the first particles are partially covered by the sodium-supplementing agent body. There are 7 first particles per unit area, labeled P1 to P7.

[0135] Figure 4 shows the first charge-discharge curve of the first coin cell of Example 1. As can be seen from Figure 4, the first charge capacity of the first coin cell of Example 1 is 364.1 mAh / g. The dQ / dV curve obtained from the first charge-discharge test of the first coin cell of Example 1 determines the oxidation decomposition potential of the sodium-supplementing material prepared in Example 1 to be 3.50 V. Figure 5 shows the first charge-discharge curve of the first coin cell of Comparative Example 1. As can be seen from Figure 5, the first charge capacity of the first coin cell of Comparative Example 1 is 348 mAh / g. The dQ / dV curve obtained from the first charge-discharge test of the first coin cell of Comparative Example 1 determines the oxidation decomposition potential to be 4.23 V. Therefore, the sodium-supplementing material of this disclosure has a lower oxidation decomposition potential.

[0136] Table 4 Performance data of the second button cell in each embodiment and comparative example

[0137] Referring to Tables 1, 2, and 4, it can be seen from Examples 1 and Comparative Examples 1 to 3 that simply crushing commercially available sodium-replenishing agent raw materials or directly physically mixing sodium-replenishing agent raw materials, conductive agents, and catalysts results in low first-cycle charging and discharging capacities for the second coin cell, due to the lack of sodium-replenishing material structure in Comparative Examples 1 and 2 and the absence of sodium-replenishing material in Comparative Example 3. Consequently, the first-cycle coulombic efficiency is low, which is detrimental to improving the energy density and cycle performance of sodium-ion batteries. Furthermore, since Comparative Example 2 directly mixes the raw materials physically, the actual oxidation decomposition efficiency of the resulting sodium-replenishing material is low, which is also detrimental to improving the performance of sodium-ion batteries. In contrast, the first-cycle charging capacity, first-cycle discharging capacity, and capacity retention rate after 20 cycles of the second coin cell disclosed in this invention are significantly improved, thus contributing to the improvement of the energy density and cycle performance of sodium-ion batteries.

[0138] The type and content of sodium-supplementing raw materials, the type and content of conductive agents, the type and content of catalysts, and the particle size of sodium-supplementing materials generally also affect the performance of sodium-ion batteries. As can be seen from Examples 2 to 14, based on the structure of the sodium-supplementing material disclosed herein, by adjusting the above parameters within the scope of this disclosure, it is beneficial to obtain an NFPP sodium-ion battery with high first-cycle charging capacity, high first-cycle discharging capacity, and excellent cycle performance.

[0139] Calcination time and temperature typically affect the performance of sodium-ion batteries. As can be seen from Examples 1 and 15-17, based on the structure of the sodium-supplementing material disclosed herein, by controlling the calcination time and temperature within the range of this disclosure, it is beneficial to obtain an NFPP sodium-ion battery with high first-cycle charge capacity, high first-cycle discharge capacity, and excellent cycle performance.

[0140] Figure 6 shows the first-cycle charge-discharge curve of the second coin cell in Example 1. As can be seen from Figure 6, the first-cycle charging capacity of the second coin cell in Example 1 is increased to 127.7 mAh / g, and the first-cycle discharge specific capacity is 104.6 mAh / g. Figure 7 shows the first-cycle charge-discharge curve of the second coin cell in Comparative Example 1. As can be seen from Figure 7, the first-cycle charging capacity of the second coin cell in Comparative Example 1 is 115.1 mAh / g, and the first-cycle discharge specific capacity is 100.8 mAh / g. Furthermore, the capacity retention rate of Example 1 after 20 cycles is also improved compared to Comparative Example 1. Therefore, the sodium-supplementing material of this disclosure can effectively compensate for the sodium loss in the first cycle of the NFPP positive electrode, demonstrating good compatibility with the NFPP positive electrode, which is beneficial to improving the energy density and cycle performance of sodium-ion batteries.

[0141] The above provides a detailed description of the sodium-supplementing material, its preparation method, the positive electrode sheet, and the sodium-ion battery disclosed herein. Specific examples have been used to illustrate the principles and implementation methods of this disclosure. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core inventive points of the embodiments of this disclosure. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this disclosure. Therefore, the content of this specification should not be construed as a limitation of this disclosure.

Claims

1. A sodium supplement material, wherein, It includes a sodium supplement body and a first particle exposed on the surface of the sodium supplement body. In any 300nm×200nm region on the surface of the sodium supplement material, the number of the first particle is between 2 and 20. The first particle includes conductive agent particles and catalyst particles.

2. The sodium supplement material according to claim 1, wherein, The first particle is partially coated with the sodium supplement body, which is formed by melting and cooling the sodium supplement raw material.

3. The sodium supplement material according to claim 1, wherein, The sodium supplement material comprises a sodium supplement body, conductive agent particles, and catalyst particles. Based on the mass of the sodium supplement material, the mass percentage of the sodium supplement body is 40% to 80%, the mass percentage of the conductive agent particles is 5% to 40%, and the mass percentage of the catalyst particles is 5% to 20%.

4. The sodium supplement material according to claim 1, wherein, The average particle size D50 of the sodium-supplementing material is 0.7 μm to 2.0 μm.

5. The sodium supplement material according to claim 1, wherein, The diameter of the portion of the first particle exposed on the surface of the sodium supplement body is 10 nm to 70 nm.

6. The sodium supplement material according to any one of claims 1 to 5, wherein, The catalyst particles are made of at least one of titanium dioxide, manganese dioxide, tin dioxide, ruthenium dioxide, molybdenum dioxide, manganese oxide, zirconium dioxide, cobalt tetroxide, and manganese tetroxide.

7. The sodium supplement material according to any one of claims 1 to 5, wherein, The sodium supplement body is made of at least one of Na2C4O4, Na2CO3, CH3COONa, C6H5Na3O7, Na2C2O4, and Na2C6O6.

8. The sodium supplement material according to any one of claims 1 to 5, wherein, The conductive agent particles are made of at least one of conductive carbon black, carbon nanotubes, Ketjen black, acetylene black, carbon black graphene, graphene oxide, and reduced graphene oxide.

9. A method for preparing a sodium-supplementing material as described in any one of claims 1 to 8, wherein, Includes the following steps: The sodium supplement raw material after particle size control treatment is mixed with conductive agent particles and catalyst particles to obtain a mixture, wherein the average particle size D50 of the sodium supplement raw material after particle size control treatment is 0.3μm~2.0μm; The mixture was calcined in a gaseous atmosphere at a temperature of 300℃ to 500℃ for 1 hour to 8 hours, and then cooled to obtain the sodium-supplementing material.

10. The preparation method according to claim 9, wherein, During calcination, the sodium supplement raw material melts, and the conductive agent particles and the catalyst particles are dispersed in the molten sodium supplement raw material. During cooling, the sodium supplement raw material solidifies and precipitates with the conductive agent particles as the skeleton to form the sodium supplement body. Part of the conductive agent particles and the catalyst particles are embedded in the sodium supplement body, and the other part is exposed on the surface of the sodium supplement body.

11. A positive electrode plate, wherein, The device includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, wherein the positive active material layer includes a sodium-supplementing material as described in any one of claims 1 to 8, or includes a sodium-supplementing material prepared by the preparation method as described in any one of claims 9 to 10.

12. A sodium-ion battery, wherein, Includes the positive electrode sheet as described in claim 11.

13. An energy storage device, wherein, It includes a housing and at least one sodium-ion battery as described in claim 12, the sodium-ion battery being housed within the housing.

14. An electrical appliance, wherein, The device includes the energy storage device of claim 13, which supplies power to the electrical equipment.

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