Negative electrode active material, preparation method thereof and sodium ion battery

Abstract

The invention discloses a negative electrode active material, a preparation method thereof and a sodium-ion battery, relates to the technical field of sodium-ion batteries, and aims to solve the problem of slow Na < + > transmission rate of a sodium-ion battery negative electrode material. The negative electrode active material comprises a carbon-based material, and a non-metallic element and a transition metal element doped in the carbon-based material. The non-metallic element is at least configured in such a manner that the mass percentage of the transition metal element in the negative electrode active material is greater than or equal to a set threshold value, and the set threshold value is greater than or equal to 3%.

Description

Technical Field

[0001] This application relates to the field of sodium-ion battery technology, and in particular to negative electrode active materials and their preparation methods, and sodium-ion batteries. Background Technology

[0002] Among sodium-ion battery anode materials, carbon-based materials (such as hard carbon) stand out due to their high specific capacity (e.g., approximately 300 mAh g⁻¹). -1 Sodium-ion batteries possess advantages such as low sodium storage potential (platform voltage, for example, around 0.1V), wide availability, low cost, and no environmental pollution, demonstrating extremely high commercial application prospects. However, carbon-based materials, when used as anode materials in sodium-ion batteries, typically exhibit Na... + The slow transmission rate leads to problems such as poor rate performance and unsatisfactory long-cycle stability of sodium-ion batteries, which hinders the practical application of carbon-based materials in sodium-ion batteries. Summary of the Invention

[0003] The purpose of this application is to provide a negative electrode active material and its preparation method, as well as a sodium-ion battery, aiming to solve the problem of sodium-ion battery negative electrode material Na + The problem of slow transmission rate.

[0004] To achieve the above objectives, this application adopts the following technical solution:

[0005] In a first aspect, this application provides a negative electrode active material. The negative electrode active material comprises: a carbon-based material, non-metallic elements doped into the carbon-based material, and transition metal elements.

[0006] The non-metallic elements are configured such that the mass percentage of the transition metal elements in the negative electrode active material is greater than or equal to a set threshold, and the set threshold is greater than or equal to 3%.

[0007] In the negative electrode active material provided in this application embodiment, the transition metal doped in the carbon-based material can provide more electrochemical sodium storage sites compared to the carbon-based material, promoting the insertion and extraction of sodium ions. The transition metal can also increase the interlayer spacing of the structure in the carbon-based material, making Na... + It can move freely in a larger space, thus improving Na + The problem of slow transmission rate has led to an increase in the capacity of sodium-ion batteries.

[0008] Furthermore, non-metallic elements doped into carbon-based materials possess unique pairs of electrons and / or vacancies, and can regulate the electronic configuration of carbon. This can increase the coordination ability of the non-metallic portion of the negative electrode active material to transition metal elements, allowing the transition metal elements to be stably doped into the carbon-based material. This ensures that the mass percentage of transition metal elements in the negative electrode active material is greater than or equal to a set threshold. Thus, the mass percentage of transition metal elements doped into carbon-based materials can be kept within a high range, thereby enhancing the transition metal's ability to improve Na+ performance. + The effect of transmission rate.

[0009] Furthermore, non-metallic elements can further increase the interlayer spacing in carbon-based materials, further improving the Na... + The problem of slow transmission rate is addressed. Furthermore, non-metallic elements can alter the electronic structure of carbon, enhancing the electronic conductivity of the negative electrode active material. Simultaneously, non-metallic elements, connected to carbon through chemical bonds (such as covalent bonds), can also enhance the structural stability of the negative electrode active material, reducing volume changes during charge and discharge. On another front, transition metals doped into carbon-based materials can act as a support, enhancing the mechanical strength and durability of the negative electrode active material, further improving its structural stability, and thus improving the cycle stability of sodium-ion batteries, thereby increasing the long-term sodium storage capacity of the negative electrode active material.

[0010] Furthermore, non-metallic elements can ensure that the mass percentage of transition metal elements in the negative electrode active material exceeds a specific set threshold, which is greater than or equal to 3%. The doping ratio of transition metal elements can be adjusted so that the negative electrode active material has more sodium storage sites, thereby improving the capacity and cycle stability of sodium-ion batteries.

[0011] In some embodiments, at least a portion of the transition metal element is connected to a nonmetal element.

[0012] In some embodiments, the mass percentage of non-metallic elements in the negative electrode active material is greater than or equal to the mass percentage of transition metal elements in the negative electrode active material.

[0013] In some embodiments, the mass percentage of carbon-based materials in the negative electrode active material ranges from 85% to 92%; the mass percentage of non-metallic elements in the negative electrode active material ranges from 5% to 10%; and the mass percentage of transition metal elements in the negative electrode active material ranges from 3% to 5%.

[0014] In some embodiments, the mass percentage of carbon-based materials in the negative electrode active material ranges from 88% to 90%; the mass percentage of non-metallic elements in the negative electrode active material ranges from 7% to 8%; and the mass percentage of transition metal elements in the negative electrode active material ranges from 3% to 4%.

[0015] In some embodiments, the transition metal element includes at least one of Fe, Co, Ni, Cu, Zn, and Mn.

[0016] In some embodiments, the nonmetallic element includes at least one of B, N, S, P, F, Cl, Br, and I.

[0017] In some embodiments, the specific surface area of ​​the negative electrode active material is in the range of 2m². 2 / g~8m 2 / g.

[0018] In some embodiments, the average particle size of the negative electrode active material ranges from 3 μm to 10 μm.

[0019] Secondly, this application provides a method for preparing the negative electrode active material according to any of the above embodiments. The method for preparing the negative electrode active material includes:

[0020] Using a non-metallic source, non-metallic elements are doped into carbon-based materials to form the first doped product.

[0021] By using a transition metal source, transition metal elements are doped into the first doped product to form a negative electrode active material.

[0022] Understandably, the method for preparing the negative electrode active material provided in the above embodiments of this application first uses a non-metal source to dope non-metallic elements into carbon-based materials, so that an unsaturated coordination structure is formed in the first doped product. Then, a transition metal source is used to make the transition metal elements doped into the non-metallic elements later more easily anchored in the carbon-based materials, thereby increasing the doping effect of non-metallic and metallic elements and significantly improving the sodium storage capacity of sodium-ion batteries.

[0023] In some embodiments, the mass ratio of carbon source to nonmetallic source in the first mixture ranges from 1:1 to 1:2.

[0024] In some embodiments, doping a nonmetallic element into a carbon-based material includes:

[0025] The carbon source is mixed with the non-metallic source to obtain the first mixture.

[0026] The first mixture was carbonized under an inert atmosphere to obtain the first doped product.

[0027] In some embodiments, doping a transition metal element into the first doped product includes:

[0028] The transition metal source is mixed with the first doped product to obtain a second mixture.

[0029] The second mixture was carbonized under an inert atmosphere to obtain the negative electrode active material.

[0030] In some embodiments, mixing the transition metal source with the first doped product includes:

[0031] The transition metal source and the first doped product are dissolved in a solvent to obtain a first solution.

[0032] The first solution was dried to obtain the second mixture.

[0033] In some embodiments, the mass ratio of the transition metal element to the first doped product in the second mixture ranges from 1:(28 to 32).

[0034] In some embodiments, the carbonization temperature of the first mixture is less than or equal to the carbonization temperature of the second mixture.

[0035] In some embodiments, the carbonization temperature of the first mixture ranges from 200°C to 600°C.

[0036] In some embodiments, the carbonization time of the first mixture ranges from 1 hour to 10 hours.

[0037] In some embodiments, the carbonization temperature of the second mixture ranges from 600°C to 1200°C.

[0038] In some embodiments, the carbonization time of the second mixture ranges from 1 hour to 10 hours.

[0039] In some embodiments, the non-metallic source includes at least one of boric acid, urea, thiourea, sodium hypophosphite, ammonium fluoride, ammonium chloride, ammonium bromide, and ammonium iodide.

[0040] In some embodiments, the transition metal salt includes at least one of ferric nitrate, cobalt nitrate, nickel nitrate, copper nitrate, zinc nitrate, and manganese chloride.

[0041] In some embodiments, the carbon source includes at least one of bamboo charcoal, coconut shell, rice husk, bitumen, and coal.

[0042] Thirdly, this application provides a sodium-ion battery. The sodium-ion battery includes a negative electrode and a positive electrode disposed opposite to each other. The material of the negative electrode includes the negative electrode active material as described in any of the above embodiments.

[0043] It is understood that the beneficial effects of the sodium-ion battery provided in the above embodiments of this application can be referred to the beneficial effects of the negative electrode active material mentioned above, and will not be repeated here.

[0044] In some embodiments, the reversible capacity of the sodium-ion battery under a first preset condition ranges from 250 mAh / g to 400 mAh / g. The first preset condition includes charging and discharging at 0.08C to 0.12C, where 1C is 200 mA / g.

[0045] In some embodiments, the capacity retention rate of the sodium-ion battery under a second preset condition ranges from 35% to 45%. The second preset condition includes charging and discharging at 0.8C to 1.2C, where 1C is 200mA / g. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a flowchart illustrating a method for preparing a negative electrode active material according to an embodiment of this application.

[0048] Figure 2 The transmission electron microscope image and elemental distribution map of the negative electrode active material provided in Example 1 are shown. Detailed Implementation

[0049] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0050] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0051] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "communication" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. They can refer to a direct connection or an indirect connection through an intermediate medium, or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0052] In embodiments of this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, article, or apparatus that includes that element.

[0053] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0054] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0055] Sodium-ion batteries, as a new type of rechargeable battery technology, have advantages such as abundant raw materials, low price, high safety and wide operating temperature range, and can be applied in electric new energy vehicles, smart grid energy storage and home energy storage systems.

[0056] An embodiment of this application provides a sodium-ion battery. The sodium-ion battery includes a negative electrode and a positive electrode disposed opposite to each other. The material of the negative electrode includes a negative electrode active material.

[0057] During the charging and discharging process of sodium-ion batteries, Na + It inserts and extracts back and forth between the two electrodes. During charging, Na... + Electrons are deintercalated from the positive electrode and intercalated into the negative electrode via the electrolyte. Simultaneously, compensating charges are supplied to the negative electrode via an external circuit to maintain charge balance between the positive and negative electrodes. The process is reversed during discharge. + It deintercalates from the negative electrode and intercalates into the positive electrode via the electrolyte.

[0058] The negative electrode active material is a key component in the negative electrode, determining its sodium ion storage capacity and reactivity. Negative electrode active materials for sodium-ion batteries include carbon-based materials (such as graphite, hard carbon, and soft carbon), alloy materials (such as tin-based alloys and antimony-based alloys), metal oxides / sulfides, and organic compounds.

[0059] Carbon-based materials typically exhibit good cycle stability and high specific capacity, but pure carbon-based materials often show Na+ characteristics when used as anode materials in sodium-ion batteries. + The slow transmission rate is attributed to the fact that carbon-based materials are layered carbon materials, with layers connected by weak van der Waals forces, while the carbon elements within each layer are tightly bound together by covalent bonds. This results in relatively small interlayer distances in carbon-based materials, while Na... + With a relatively large radius, Na needs to move within this relatively small space during interlayer insertion / extraction in carbon-based materials, making Na… + The slow transmission rate leads to problems such as low initial cycle efficiency (<80%), poor rate performance, and unsatisfactory long-cycle stability of sodium-ion batteries.

[0060] Based on this, embodiments of this application provide a negative electrode active material. The negative electrode active material includes: a carbon-based material, non-metallic elements doped into the carbon-based material, and transition metal elements.

[0061] The non-metallic elements are configured such that the mass percentage of the transition metal elements in the negative electrode active material is greater than or equal to a set threshold, and the set threshold is greater than or equal to 3%.

[0062] For example, the threshold can be set to 3%, 3.5%, 4%, 4.5%, or 5%, etc., and there is no limit here.

[0063] Carbon-based materials possess good electrical conductivity and a relatively stable structure, which facilitates the insertion and extraction of sodium ions. However, as mentioned above, pure carbon-based materials exhibit sodium... + The problem of slow transmission rate.

[0064] Transition metals doped in carbon-based materials can provide more electrochemical sodium storage sites compared to carbon-based materials, promoting the insertion and extraction of sodium ions. Transition metals can also increase the interlayer spacing in the structure of carbon-based materials, allowing Na+ to move freely in a larger space. This can improve the problem of slow Na+ transport rate and increase the capacity of sodium-ion batteries.

[0065] Furthermore, non-metallic elements doped in carbon-based materials possess unique pairs of electrons and / or vacancies, and can regulate the electronic configuration of carbon elements. This can increase the coordination ability of the non-metallic portion of the negative electrode active material to transition metal elements, allowing transition metal elements to be stably doped into carbon-based materials. This ensures that the mass percentage of transition metal elements in the negative electrode active material is greater than or equal to a set threshold. Thus, the mass percentage of transition metal elements doped in carbon-based materials can be kept within a high range, thereby enhancing the effect of transition metals in increasing Na+ transport rates.

[0066] Furthermore, non-metallic elements can further increase the interlayer spacing in carbon-based materials, further mitigating the problem of slow Na+ transport rates. Moreover, non-metallic elements can alter the electronic structure of carbon, enhancing the electronic conductivity of the negative electrode active material. Simultaneously, non-metallic elements, connected to carbon through chemical bonds (such as covalent bonds), can also enhance the structural stability of the negative electrode active material, reducing volume changes during charge and discharge. On another front, transition metals doped into carbon-based materials can act as a support, enhancing the mechanical strength and durability of the negative electrode active material, further improving its structural stability, and thus improving the cycle stability of sodium-ion batteries, thereby enhancing the long-term sodium storage capacity of the negative electrode active material.

[0067] In some embodiments, at least a portion of the transition metal element is connected to a nonmetal element.

[0068] Understandably, by linking transition metal elements with nonmetal elements, such as forming coordination linkages, transition metal elements can be stably doped into carbon-based materials, further enhancing the structural stability of the anode active material and increasing the interlayer spacing of the carbon-based material, thus improving the Na+ structure. + The problem of slow transmission rate.

[0069] In some embodiments, the mass percentage of non-metallic elements in the negative electrode active material is greater than or equal to the mass percentage of transition metal elements in the negative electrode active material.

[0070] Understandably, through the above settings, the mass percentages of non-metallic elements and transition metal elements in the negative electrode active material can be kept within a suitable range. The content of non-metallic elements used to connect the transition metals is relatively high, which is beneficial to increasing the doping ratio of transition metal elements. This results in the negative electrode active material having more sodium storage sites, thereby improving the capacity and cycle stability of the sodium-ion battery.

[0071] In some embodiments, the mass percentage of carbon-based materials in the negative electrode active material ranges from 85% to 92%; the mass percentage of non-metallic elements in the negative electrode active material ranges from 5% to 10%; and the mass percentage of transition metal elements in the negative electrode active material ranges from 3% to 5%.

[0072] For example, the mass percentage of carbon-based materials in the negative electrode active material can be 85%, 87%, 89%, 91%, or 92%, etc., and there is no limitation here.

[0073] For example, the mass percentage of non-metallic elements in the negative electrode active material can be 5%, 6%, 7%, 8%, 9%, or 10%, etc., and there is no limitation here.

[0074] For example, the mass percentage of transition metal elements in the negative electrode active material can be 3%, 3.5%, 4%, 4.5%, or 5%, etc., and there is no limitation here.

[0075] Understandably, through the above setup, the negative electrode active material can achieve good conductivity and a relatively stable structure, enabling Na... + It can move freely in a larger space, improving Na + The problem of slow transmission rate is addressed by enhancing the structural stability of the negative electrode active material, slowing down the volume change during the charging and discharging process of sodium-ion batteries, and providing more sodium storage sites for the negative electrode active material, thereby improving the capacity and cycle stability of sodium-ion batteries.

[0076] In some embodiments, the mass percentage of carbon-based materials in the negative electrode active material ranges from 88% to 90%; the mass percentage of non-metallic elements in the negative electrode active material ranges from 7% to 8%; and the mass percentage of transition metal elements in the negative electrode active material ranges from 3% to 4%.

[0077] For example, the mass percentage of carbon-based materials in the negative electrode active material can be 88%, 88.2%, 88.4%, 88.6%, 88.8%, or 90%, etc., and there is no limitation here.

[0078] For example, the mass percentage of non-metallic elements in the negative electrode active material can be 7%, 7.2%, 7.4%, 7.6%, 7.8%, or 8%, etc., and there is no limitation here.

[0079] For example, the mass percentage of transition metal elements in the negative electrode active material can be 3%, 3.2%, 3.4%, 3.6%, 3.8%, or 4%, etc., and there is no limitation here.

[0080] Understandably, the above settings can further improve Na +The problem of slow transmission rate is solved, and the structural stability of the negative electrode active material is enhanced by non-metallic and transition metal elements, which improves the effect of slowing down the volume change during the charging and discharging process of sodium-ion batteries; and more sodium storage sites are provided for the negative electrode active material, which further improves the capacity and cycle stability of sodium-ion batteries.

[0081] In some embodiments, the transition metal element includes at least one of Fe, Co, Ni, Cu, Zn, and Mn.

[0082] In some examples, the transition metal element includes one element, for example, the transition metal element includes Fe. In still other examples, the transition metal element includes one element, for example, the transition metal element includes both Fe and Co.

[0083] Understandably, the aforementioned transition metal elements have advantages such as being readily available and having low cost, and can provide more electrochemical sodium storage sites, promoting the insertion and extraction of sodium ions; they can also play a supporting role in carbon-based materials, enhancing mechanical strength and durability, fully improving the structural stability of carbon-based materials, and enhancing the long-term sodium storage capacity of sodium-ion batteries.

[0084] In some embodiments, the nonmetallic element includes at least one of B, N, S, P, F, Cl, Br, and I.

[0085] In some examples, the nonmetallic element includes one element, for example, the nonmetallic element includes B. In still other examples, the nonmetallic element includes one element, for example, the nonmetallic element includes both B and N.

[0086] Understandably, doping at least one of the aforementioned non-metallic elements B, N, S, P, F, Cl, Br, and I into carbon-based materials can alter the electronic structure of the carbon-based materials and enhance the electronic conductivity of the negative electrode; it can also enhance the structural stability of carbon-based materials through chemical bonding and improve the cycle stability of sodium-ion batteries.

[0087] In some embodiments, the specific surface area of ​​the negative electrode active material is in the range of 2m². 2 / g~8m 2 / g.

[0088] For example, the specific surface area of ​​the negative electrode active material can be 2m². 2 / g、4m 2 / g、6m 2 / g or 8m 2 / g etc., there are no restrictions here.

[0089] Understandably, with the above configuration, the negative electrode active material has a larger specific surface area, which can provide more active sites and more effectively adsorb and desorb Na. +, making more Na + It can be embedded in the negative electrode material, thereby improving the sodium storage performance of sodium-ion batteries.

[0090] In some embodiments, the average particle size of the negative electrode active material ranges from 3 μm to 10 μm.

[0091] For example, the average particle size of the negative electrode active material can be 3μm, 5μm, 7μm, 9μm or 10μm, etc., and there is no limitation here.

[0092] Understandably, the above configuration allows for a larger specific surface area of ​​the negative electrode active material, providing more active sites and enabling more effective adsorption and desorption of Na. + , making more Na + It can be embedded into the negative electrode material, thereby improving the sodium storage performance of sodium-ion batteries; moreover, it can also make the negative electrode active material have more porous structures, which is beneficial to Na + Rapid ion transport.

[0093] Secondly, embodiments of this application provide a method for preparing the negative electrode active material according to any of the above embodiments. For example... Figure 1 As shown, the preparation method of the negative electrode active material includes: S1 to S2.

[0094] S1: Using a non-metallic source, non-metallic elements are doped into carbon-based materials to form the first doped product.

[0095] S2: Using a transition metal source, transition metal elements are doped into the first doped product to form a negative electrode active material.

[0096] Understandably, through the above setup, non-metallic elements are first doped into the carbon-based material, followed by transition metal elements. This allows the use of non-metallic elements to create unique pairs of electrons and / or vacancies in the first doped product, and to regulate the electron configuration of carbon elements, thereby increasing the coordination ability of the non-metallic portion of the negative electrode active material to the transition metal elements. Consequently, during the doping of the transition metal elements into the first doped product, the transition metal elements are more easily anchored in the carbon-based material, improving the doping effect of both non-metallic and metallic elements. This ensures that the mass percentage of transition metal elements in the negative electrode active material is greater than or equal to a set threshold, and that the mass percentage of transition metal elements doped into the carbon-based material remains within a high range, thus enhancing the transition metal's ability to improve Na+. + The improved transmission rate significantly enhances the sodium storage capacity of sodium-ion batteries.

[0097] In some embodiments, S1 involves doping a non-metallic element into a carbon-based material, including: S1.1 to S1.2.

[0098] S1.1: Mix the carbon source with the non-metallic source to obtain the first mixture.

[0099] For example, non-metallic sources include at least one of boric acid, urea, thiourea, sodium hypophosphite, ammonium fluoride, ammonium chloride, ammonium bromide, and ammonium iodide.

[0100] For example, carbon sources include at least one of bamboo charcoal, coconut shell, rice husk, bitumen, and coal.

[0101] S1.2: The first mixture is carbonized under an inert atmosphere to obtain the first doped product.

[0102] In some examples, the carbonization temperature range for the first mixture is 200°C to 600°C.

[0103] For example, the carbonization temperature of the first mixture can be 200°C, 300°C, 400°C, 500°C or 600°C, etc., and there is no limitation here.

[0104] In some examples, the carbonization time of the first mixture ranges from 1 hour to 10 hours.

[0105] For example, the carbonization time of the first mixture can be 1h, 2h, 3h, 4h, 5h or 6h, etc., and there is no limitation here.

[0106] For example, in the first mixture, the mass ratio of carbon source to non-metallic source ranges from 1:1 to 1:2.

[0107] Understandably, through carbonization, the carbon source and non-metal source in the first mixture will undergo a chemical reaction to form a carbon-based material doped with non-metallic elements (i.e., the first doped product).

[0108] In some embodiments, S2 involves doping a transition metal element into the first doped product, including: S2.1 to S2.2.

[0109] S2.1: Mix the transition metal source with the first doped product to obtain a second mixture.

[0110] For example, transition metal salts include at least one of the following: iron salts, cobalt salts, nickel salts, copper salts, zinc salts, and manganese salts.

[0111] In some examples, the transition metal salt includes at least one of ferric nitrate, cobalt nitrate, nickel nitrate, copper nitrate, zinc nitrate, and manganese chloride.

[0112] S2.2: The second mixture is carbonized under an inert atmosphere to obtain the negative electrode active material.

[0113] In some examples, the carbonization temperature range for the second mixture is 600°C to 1200°C.

[0114] For example, the carbonization temperature of the second mixture can be 600°C, 700°C, 800°C, 1000°C or 1200°C, etc., and there is no limitation here.

[0115] In some examples, the carbonization time of the second mixture ranges from 1 hour to 10 hours.

[0116] For example, the carbonization treatment of the second mixture can be 1h, 2h, 3h, 4h, 5h or 6h, etc., and there is no limitation here.

[0117] In some examples, the inert atmosphere may contain inert gases and / or nitrogen.

[0118] For example, the inert gas can be helium, argon, etc.

[0119] Understandably, by carbonizing the mixture of the first doped product and the transition metal source in an inert atmosphere, the metal ions doped in the first doped product are thermally reduced to elemental metals and uniformly doped into the carbon-based material.

[0120] In some embodiments, S2.1 mixing the transition metal source with the first doped product includes: S2.1.1 to S2.1.2.

[0121] S2.1.1: Dissolve the transition metal source and the first doped product in a solvent to obtain a first solution.

[0122] S2.1.2: Dry the first solution to obtain the second mixture.

[0123] For example, in the second mixture, the mass ratio of the transition metal element to the first doped product ranges from 1:(28 to 32).

[0124] Understandably, the aforementioned transition metal ions can be uniformly doped into the first doped product.

[0125] For example, the above-mentioned negative electrode active material can be prepared by the following steps:

[0126] (1) The non-metallic source is cleaned, crushed, sieved, acid-washed and dried to obtain a purified non-metallic source. The purified non-metallic source and the carbon-based material source are then mixed by ball milling to make the carbon source and non-metallic source mix evenly and fully, thereby obtaining the first mixture.

[0127] (2) The first mixture is carbonized. During the carbonization process, the carbon source will form the first doped product. The non-metal source containing non-metallic elements decomposes and uniformly dops the non-metallic elements into the first doped product, thereby obtaining the first doped product uniformly doped with non-metallic elements.

[0128] (3) The first doped product and the transition metal source are ultrasonically dispersed in an ethanol / water mixed solvent to obtain a first solution; the mixed solvent is heated under magnetic stirring to remove the solvent, so that the transition metal ions are uniformly doped in the first doped product, thereby obtaining a second mixture.

[0129] (4) The second mixture is carbonized in an inert atmosphere to transform the first doped product into a carbon-based material, and the transition metal ions are thermally reduced to metal elements and uniformly doped into the carbon-based material.

[0130] In some embodiments, the carbonization temperature of the first mixture is less than or equal to the carbonization temperature of the second mixture.

[0131] Understandably, the carbonization temperature of the first mixture facilitates the formation of graphite sheets within the carbon-based material and allows non-metallic elements to enter the graphite sheets. Then, the carbonization of the second mixture allows transition metal elements to be incorporated into the carbon-based material.

[0132] In some embodiments, the reversible capacity of the sodium-ion battery under a first preset condition ranges from 250 mAh / g to 400 mAh / g. The first preset condition includes charging and discharging at 0.08C to 0.12C, where 1C is 200 mA / g.

[0133] For example, the reversible capacity of sodium-ion batteries at 0.08C to 0.12C can be 250mAh / g, 300mAh / g, 350mAh / g, or 400mAh / g, etc., and there is no limitation here.

[0134] Understandably, the reversible capacity of the sodium-ion battery described above ranges from 0.08C to 0.12C, from 250mAh / g to 400mAh / g. Sodium-ion batteries can store more energy, thereby providing longer usage time or higher power output after a single charge.

[0135] In some embodiments, the capacity retention rate of the sodium-ion battery under a second preset condition ranges from 35% to 45%. The second preset condition includes charging and discharging at 0.8C to 1.2C, where 1C is 200mA / g.

[0136] For example, the capacity retention rate of a sodium-ion battery at 0.8C to 1.2C can be 35%, 37%, 40%, 42.5%, or 45%, etc., and there is no limitation here.

[0137] Understandably, the sodium-ion battery retains 35% to 45% of its capacity at 0.8C to 1.2C, and sodium-ion batteries can maintain higher capacity at higher discharge rates.

[0138] The invention will be further described in detail below through several specific experiments as examples and in conjunction with the accompanying drawings.

[0139] In the examples and comparative examples, all raw materials used were commercially available products. Boric acid, urea, melamine, thiourea, sulfur powder, phosphoric acid, sodium hypophosphite, ammonium fluoride, ammonium chloride, ammonium bromide, ammonium iodide, nitrates, manganese chloride and other reagents were available from Sigma-Aldrich. All equipment used was conventional equipment and all testing methods were conventional methods.

[0140] Example 1

[0141] Example 1 provides a negative electrode active material, and the preparation method of the negative electrode active material is as follows:

[0142] A1. First, the coconut shells are cleaned, crushed, sieved, acid-washed, and dried to obtain purified coconut shell carbon. Then, the coconut shell carbon and sodium hypophosphite are placed in a ball mill at a mass ratio of 1:1 for crushing, grinding, and sieving to mix evenly, thus obtaining the first mixture.

[0143] A2. The first mixture solid powder is placed in a tube furnace and heated at 300°C for 2 hours in a nitrogen atmosphere to carbonize it, thereby obtaining the first doped product.

[0144] A3. Disperse the first doped product in an ethanol / water mixed solvent (Vol. 水 :Vol 乙醇 In a mixture of nickel and nickel, nickel nitrate hexahydrate was added to the solution at a ratio of 1:1. The mixture was then stirred continuously at 70°C until the solvent was completely evaporated, yielding a second mixture solid powder doped with the transition metal nickel. The mass ratio of the added nickel to the second mixture was 1:30.

[0145] A4. The second mixture of solid powder is placed in a tube furnace and heated at 900°C for 2 hours in a nitrogen atmosphere to carbonize, obtaining a negative electrode active material co-doped with nickel metal and phosphorus nonmetal, wherein the specific surface area of ​​the negative electrode active material is 4.6 m². 2 / g, with an average particle size of 7.62μm, and the mass percentage of P in the negative electrode active material is 7.2%, while the mass percentage of Ni in the negative electrode active material is 4.1%.

[0146] like Figure 2As shown, Figure 2 This provides a transmission electron microscope image and elemental distribution map of a negative electrode active material for Example 1, from... Figure 2 It can be seen that obvious distributions of P and Ni elements can be observed on the surface of carbon-based materials, proving that the non-metallic element P and the transition metal element Ni have been successfully doped into carbon-based materials.

[0147] Example 2

[0148] Example 2 provides a negative electrode active material, and the preparation method of the negative electrode active material is as follows:

[0149] B1. First, the coconut shells are washed, crushed, sieved, acid-washed, and dried to obtain purified coconut shell carbon. Then, the coconut shell carbon and urea are placed in a ball mill at a mass ratio of 1:1 for crushing, grinding, and sieving to mix evenly, thus obtaining the first mixture.

[0150] B2. The first mixture solid powder is placed in a tube furnace and heated at 500°C for 2 hours in a nitrogen atmosphere to carbonize it, thereby obtaining the first doped product.

[0151] B3. Disperse the first doped product in an ethanol / water mixed solvent (Vol. 水 :Vol 乙醇 In a mixture of cobalt nitrate (cobalt nitrate hexahydrate) and nickel (cobalt nitrate) in a ratio of 1:1, cobalt nitrate hexahydrate was added to the solution, and the mixture was stirred continuously at 70°C until the solvent was completely evaporated, yielding a second mixture solid powder doped with the transition metal cobalt. The mass ratio of added nickel to the second mixture was 1:30.

[0152] B4. The second mixture of solid powder is placed in a tube furnace and heated at 900°C for 2 hours in a nitrogen atmosphere for carbonization to obtain a cobalt metal and nitrogen nonmetal co-doped carbon-based negative electrode active material, wherein the specific surface area of ​​the negative electrode active material is 4.7 m². 2 / g, with an average particle size of 7.55μm, nitrogen content in the negative electrode active material is 5.4% by mass, and cobalt content in the negative electrode active material is 4.3% by mass.

[0153] Example 3

[0154] Example 3 provides a negative electrode active material, and the preparation method of the negative electrode active material is as follows:

[0155] C1. First, the bamboo is washed, crushed, sieved, acid-washed, and dried to obtain purified bamboo-based carbon. Then, the bamboo-based carbon and boric acid are placed in a ball mill at a mass ratio of 1:1 for crushing, grinding, and sieving to mix evenly, thus obtaining the first mixture.

[0156] C2. The first mixture solid powder is placed in a tube furnace and heated at 400°C for 2 hours in a nitrogen atmosphere to carbonize it, thereby obtaining the first doped product.

[0157] C3. Disperse the first doped product in an ethanol / water mixed solvent (Vol. 水 :Vol 乙醇 In a mixture of nickel and nickel, the ratio of nickel to copper in the first mixture was 1:1. Copper nitrate hexahydrate was then added to the solution, and the mixture was continuously stirred at 70°C until the solvent was completely evaporated, yielding a second mixture of copper-doped solid powder. The mass ratio of added nickel to the second mixture was 1:25.

[0158] C4. The second mixture of solid powder is placed in a tube furnace and heated at 1200℃ for 2 hours in a nitrogen atmosphere for carbonization, yielding a copper- and boron-doped carbon-based negative electrode active material with a specific surface area of ​​5.2 m². 2 / g, with an average particle size of 7.31μm, boron content in the negative electrode active material is 5.5% by mass, and copper content in the negative electrode active material is 3.6% by mass.

[0159] Example 4

[0160] Example 4 provides a negative electrode active material, and the preparation method of the negative electrode active material is as follows:

[0161] D1. First, the bamboo is washed, crushed, sieved, acid-washed, and dried to obtain purified bamboo-based carbon. Then, the bamboo-based carbon and sulfur powder are placed in a ball mill at a mass ratio of 1:1 for crushing, grinding, and sieving to mix evenly, thus obtaining the first mixture.

[0162] D2. The first mixture solid powder is placed in a tube furnace and heated at 500°C for 2 hours in a nitrogen atmosphere to carbonize it, thereby obtaining the first doped product.

[0163] D3. Disperse the first doped product in an ethanol / water mixed solvent (Vol. 水 :Vol 乙醇 In a mixture of nickel and nickel, the ratio of nickel to copper in the first mixture was 1:1. Copper nitrate hexahydrate was then added to the solution, and the mixture was continuously stirred at 70°C until the solvent was completely evaporated, yielding a second mixture of copper-doped solid powder. The mass ratio of added nickel to the second mixture was 1:30.

[0164] D4. The second mixture of solid powder was placed in a tube furnace and heated at 800°C for 2 hours in a nitrogen atmosphere to carbonize, obtaining a copper-metal and sulfur-nonmetal co-doped carbon-based anode active material, wherein the specific surface area of ​​the anode active material was 5.6 m². 2 / g, with an average particle size of 7.72μm, sulfur accounting for 8.4% of the mass of the anode active material, and copper accounting for 4.2% of the mass of the anode active material.

[0165] Example 5

[0166] Example 5 provides a negative electrode active material, the preparation method of which is as follows:

[0167] E1. First, the bituminous coal is washed, crushed, sieved, acid-washed, and dried to obtain purified bituminous coal carbon. Then, the bituminous coal carbon and sulfur powder are placed in a ball mill at a mass ratio of 1:1 for crushing, grinding, and sieving to mix evenly, thus obtaining the first mixture.

[0168] E2. The first mixture solid powder is placed in a tube furnace and heated at 400°C for 2 hours in a nitrogen atmosphere to carbonize it, thereby obtaining the first doped product.

[0169] E3. Disperse the first doped product in an ethanol / water mixed solvent (Vol. 水 :Vol 乙醇 In a mixture of nickel and nickel, nickel nitrate hexahydrate was added to the solution at a ratio of 1:1. The mixture was then stirred continuously at 70°C until the solvent was completely evaporated, yielding a second mixture solid powder doped with the transition metal nickel. The mass ratio of the added nickel to the second mixture was 1:30.

[0170] E4. The second mixture of solid powder is placed in a tube furnace and heated at 800°C for 2 hours in a nitrogen atmosphere for carbonization to obtain a negative electrode active material co-doped with nickel metal and sulfur nonmetal, wherein the specific surface area of ​​the negative electrode active material is 3.4 m². 2 / g, with an average particle size of 5.86μm, sulfur accounting for 9.2% of the mass of the negative electrode active material, and nickel accounting for 3.1% of the mass of the negative electrode active material.

[0171] Example 6

[0172] Example 6 provides a negative electrode active material, the preparation method of which is as follows:

[0173] F1. First, anthracite is washed, crushed, sieved, acid-washed, and dried to obtain purified anthracite carbon. Then, anthracite carbon and sodium hypophosphite are placed in a ball mill at a mass ratio of 1:2 for crushing, grinding, and sieving to mix evenly, thus obtaining the first mixture.

[0174] F2. The first mixture solid powder is placed in a tube furnace and heated at 300°C for 2 hours in a nitrogen atmosphere to carbonize it, thereby obtaining the first doped product.

[0175] F3. Disperse the first doped product in an ethanol / water mixed solvent (Vol. 水 :Vol 乙醇 In a mixture of cobalt nitrate (cobalt nitrate hexahydrate) and nickel (cobalt nitrate) in a ratio of 1:1, cobalt nitrate hexahydrate was added to the solution, and the mixture was stirred continuously at 70°C until the solvent was completely evaporated, yielding a second mixture solid powder doped with the transition metal cobalt. The mass ratio of added nickel to the second mixture was 1:30.

[0176] F4. The second mixture of solid powder is placed in a tube furnace and heated at 900°C for 2 hours in a nitrogen atmosphere for carbonization, yielding a cobalt metal and phosphorus nonmetal co-doped carbon-based negative electrode active material, wherein the specific surface area of ​​the negative electrode active material is 3.7 m². 2 / g, with an average particle size of 5.69μm, phosphorus content in the negative electrode active material is 7.3% by mass, and cobalt content in the negative electrode active material is 3.6% by mass.

[0177] Comparative Example 1

[0178] Comparative Example 1 provides a negative electrode active material, the preparation method of which is as follows:

[0179] G1. First, the coconut shells are washed, crushed, sieved, acid-washed, and dried to obtain purified coconut shell carbon. Then, the coconut shell carbon is placed in a tube furnace and heated at 300°C for 2 hours in a nitrogen atmosphere to carbonize it, thus obtaining the first product.

[0180] G3. The first product solid powder is placed in a tube furnace and heated at 800°C for 2 hours in a nitrogen atmosphere for carbonization, yielding a carbon material without non-metallic or metallic elements, which serves as the negative electrode active material. The specific surface area of ​​the negative electrode active material is 4.2 m². 2 / g, with an average particle size of 7.19μm.

[0181] Comparative Example 2

[0182] Comparative Example 2 provides a negative electrode active material, the preparation method of which is as follows:

[0183] I1. First, the bamboo is washed, crushed, sieved, acid-washed, and dried to obtain purified bamboo-based carbon. Then, the bamboo-based carbon is placed in a tube furnace and heated at 400°C for 2 hours in a nitrogen atmosphere to carbonize it, thus obtaining the first product.

[0184] I3. The first product solid powder is placed in a tube furnace and heated at 1200℃ for 2 hours in a nitrogen atmosphere for carbonization, yielding a carbon material without non-metallic or metallic elements, which serves as the negative electrode active material. The specific surface area of ​​the negative electrode active material is 5.3 m². 2 / g, with an average particle size of 7.63μm.

[0185] Comparative Example 3

[0186] Comparative Example 3 provides a negative electrode active material, the preparation method of which is as follows:

[0187] P1. First, the bituminous coal is washed, crushed, sieved, acid-washed, and dried to obtain purified bituminous coal carbon. Then, the bituminous coal carbon is placed in a tube furnace and heated at 400°C for 2 hours in a nitrogen atmosphere to carbonize it, thus obtaining the first product.

[0188] P3. The first product solid powder is placed in a tube furnace and heated at 1000℃ for 2 hours in a nitrogen atmosphere for carbonization, yielding carbon materials without non-metallic or metallic elements, which serve as the negative electrode active material. The specific surface area of ​​the negative electrode active material is 3.3 m². 2 / g, with an average particle size of 5.95μm.

[0189] Comparative Example 4

[0190] Comparative Example 4 provides a negative electrode active material, the preparation method of which is as follows:

[0191] T1. First, the anthracite is washed, crushed, sieved, acid-washed, and dried to obtain purified anthracite carbon. Then, the anthracite carbon is placed in a tube furnace and heated at 300°C for 2 hours in a nitrogen atmosphere to carbonize it, thus obtaining the first product.

[0192] T3. The first product solid powder is placed in a tube furnace and heated at 800°C for 2 hours in a nitrogen atmosphere for carbonization, yielding a carbon material without non-metallic or metallic elements as the negative electrode active material. The specific surface area of ​​the negative electrode active material is 3.5 m². 2 / g, with an average particle size of 5.71μm.

[0193] Comparative Example 5

[0194] Comparative Example 5 provides a negative electrode active material, the preparation method of which is as follows:

[0195] Phenolic resin and epoxy resin were mixed and carbonized at 1200℃ for 3 hours to obtain a negative electrode active material with a specific surface area of ​​5.5 m². 2 / g, with an average particle size of 8.33μm.

[0196] Comparative Example 6

[0197] Comparative Example 6 provides a negative electrode active material, the preparation method of which is as follows:

[0198] Q1. First, the coconut shells are washed, crushed, sieved, acid-washed, and dried to obtain purified coconut shell carbon. Then, the coconut shell carbon solid powder is placed in a tube furnace and heated at 300°C for 2 hours in a nitrogen atmosphere to carbonize it, thus obtaining the first product.

[0199] Q2. The first product is dispersed in an ethanol / water mixed solvent (Vol. 水 :Vol 乙醇 In a mixture of cobalt and cobalt, cobalt nitrate hexahydrate was added to the solution, and the mixture was stirred at 70°C to completely evaporate the solvent, yielding a second mixture of cobalt-doped solid powder. The mass ratio of cobalt added to the second mixture was 1:30.

[0200] Q3. The second mixture of solid powder is placed in a tube furnace and heated at 900°C for 2 hours in a nitrogen atmosphere to carbonize, obtaining a cobalt-doped carbon-based negative electrode active material, wherein the specific surface area of ​​the negative electrode active material is 4.3 m². 2 / g, with an average particle size of 7.43μm, and the mass percentage of cobalt in the negative electrode active material is 3.8%.

[0201] Comparative Example 7

[0202] Comparative Example 7 provides a negative electrode active material, the preparation method of which is as follows:

[0203] H1. First, anthracite is washed, crushed, sieved, acid-washed, and dried to obtain purified anthracite carbon. Then, anthracite carbon and sodium hypophosphite are placed in a ball mill at a mass ratio of 1:2 for crushing, grinding, and sieving to mix evenly, thus obtaining the first mixture.

[0204] H2. The first mixture solid powder is placed in a tube furnace and heated at 300°C for 2 hours in a nitrogen atmosphere to carbonize it, thereby obtaining the first doped product.

[0205] H3. The first doped product solid powder was placed in a tube furnace and heated at 900°C for 2 hours in a nitrogen atmosphere to carbonize it, obtaining a phosphorus nonmetal-doped carbon-based negative electrode active material, wherein the specific surface area of ​​the negative electrode active material is 3.7 m². 2 / g, with an average particle size of 5.73μm, and phosphorus content in the negative electrode active material is 7.1% by mass.

[0206] Comparative Example 8

[0207] Comparative Example 8 provides a negative electrode active material, and the preparation method of the negative electrode active material is as follows: K1. First, the coconut shell is washed, crushed, sieved, acid-washed, and dried to obtain purified coconut shell carbon.

[0208] K2, Disperse the purified coconut shell carbon in an ethanol / water mixed solvent (Vol. 水 :Vol 乙醇In a mixture of nickel and nickel, nickel nitrate hexahydrate was added to a solution of nickel and nickel, and the mixture was stirred continuously at 70°C until the solvent was completely evaporated, yielding a second mixture solid powder doped with the transition metal nickel. The mass ratio of the added nickel to the second mixture was 1:30.

[0209] K3. The second mixture solid powder is placed in a tube furnace and heated at 300°C for 2 hours in a nitrogen atmosphere to carbonize it, thereby obtaining the first doped product.

[0210] K4. The first doped product and sodium hypophosphite are placed in a ball mill at a mass ratio of 1:1 and pulverized, ground, and sieved to mix evenly, thus obtaining the first mixture.

[0211] K5. The first mixture of solid powder is placed in a tube furnace and heated at 900°C for 2 hours in a nitrogen atmosphere for carbonization, yielding a negative electrode active material co-doped with nickel metal and phosphorus nonmetal, wherein the specific surface area of ​​the negative electrode active material is 4.4 m². 2 / g, with an average particle size of 7.52μm, phosphorus content in the negative electrode active material is 7.4% by mass, and nickel content in the negative electrode active material is 1.2% by mass.

[0212] Performance testing

[0213] The negative electrode active material (negative electrode active material: CMC:SBR:SP = 100:1.5:3:1) and sodium sheet were used as positive electrodes in the examples and comparative examples, respectively. The electrolyte was NaPF6 / (PC+EMC) (electrolyte solvent volume ratio PC:EMC = 1:1), and the separator was made of glass fiber. The coin cell half-cells were assembled in a glove box filled with high-purity argon gas. The coin cell model was CR2032. The assembled sodium-ion batteries were charged and discharged at a current of 0.1C (1C = 200mA / g) in the battery testing system. The reversible capacity at 0.1C was recorded. Then, the batteries were charged and discharged at a current of 1C. The capacity retention rate at 1C was obtained by dividing the reversible capacity measured at 1C by the reversible capacity at 0.1C. The results are shown in Table 1.

[0214] Table 1 shows the performance of sodium-ion batteries prepared using the negative electrode active materials in the examples and comparative examples.

[0215]

[0216]

[0217] As shown in Table 1, compared with the negative electrode active material of Comparative Example 5, the negative electrode prepared using materials such as coconut shell, bamboo charcoal, and coal has a higher capacity and better performance in Example 1.

[0218] Compared with the negative electrode active materials of Comparative Examples 1-4, Comparative Examples 6 and Comparative Examples 7, the negative electrode active materials of Examples 1-6 exhibited significantly improved reversible capacity and significantly improved rate performance, indicating that the simultaneous synergistic doping of non-metallic elements and transition metal elements in carbon-based materials can significantly improve the reversible capacity and rate performance of sodium-ion batteries.

[0219] In Example 1, the mass percentage of nickel in the negative electrode active material was 7.2%, while in Comparative Example 8, the mass percentage of nickel was 1.2%. This indicates that, with identical doping element and raw material amounts, doping with non-metallic elements first followed by metallic elements is significantly more effective than doping with metallic elements first followed by non-metallic elements, with a capacity difference of 10%. This is attributed to the fact that using non-metallic elements increases their coordination ability with transition metal elements in the negative electrode active material, making it easier for transition metal elements to anchor in carbon-based materials. This allows for a higher mass percentage of transition metal elements in the carbon-based material, improving the doping effect of both non-metallic and metallic elements and enhancing the transition metal's ability to increase Na+. + The improved transmission rate significantly enhances the sodium storage capacity of sodium-ion batteries.

[0220] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A negative electrode active material, characterized in that, include: Carbon-based materials; The carbon-based material is doped with non-metallic elements and transition metal elements, wherein the non-metallic elements are configured such that the mass percentage of the transition metal elements in the negative electrode active material is greater than or equal to a set threshold, wherein the set threshold is greater than or equal to 3%.

2. The negative electrode active material according to claim 1, characterized in that, At least a portion of the transition metal element is connected to the non-metal element.

3. The negative electrode active material according to claim 1, characterized in that, The mass percentage of the non-metallic element in the negative electrode active material is greater than or equal to the mass percentage of the transition metal element in the negative electrode active material.

4. The negative electrode active material according to claim 1, characterized in that, The carbon-based material comprises 85% to 92% of the negative electrode active material by mass; the non-metallic element comprises 5% to 10% of the negative electrode active material by mass; and the transition metal element comprises 3% to 5% of the negative electrode active material by mass.

5. The negative electrode active material according to claim 1, characterized in that, The carbon-based material comprises 88% to 90% of the negative electrode active material by mass; the non-metallic element comprises 7% to 8% of the negative electrode active material by mass; and the transition metal element comprises 3% to 4% of the negative electrode active material by mass.

6. The negative electrode active material according to any one of claims 1 to 5, characterized in that, The transition metal element includes at least one of Fe, Co, Ni, Cu, Zn, and Mn.

7. The negative electrode active material according to any one of claims 1 to 5, characterized in that, The nonmetallic elements include at least one of B, N, S, P, F, Cl, Br, and I.

8. The negative electrode active material according to any one of claims 1 to 5, characterized in that, The specific surface area of ​​the negative electrode active material is in the range of 2m². 2 / g~8m 2 / g.

9. The negative electrode active material according to any one of claims 1 to 5, characterized in that, The average particle size of the negative electrode active material ranges from 3 μm to 10 μm.

10. A method for preparing a negative electrode active material, used to prepare the negative electrode active material according to any one of claims 1 to 9, characterized in that, include: Using a non-metallic source, the non-metallic element is doped into the carbon-based material to form a first doped product; Using a transition metal source, the transition metal element is doped into the first doped product to form the negative electrode active material.

11. The method for preparing the negative electrode active material according to claim 10, characterized in that, The step of doping the non-metallic element into the carbon-based material includes: The carbon source is mixed with the non-metallic source to obtain a first mixture; The first mixture was carbonized under an inert atmosphere to obtain the first doped product.

12. The method for preparing the negative electrode active material according to claim 11, characterized in that, In the first mixture, the mass ratio of the carbon source to the non-metallic source ranges from 1:1 to 1:

2.

13. The method for preparing the negative electrode active material according to claim 10, characterized in that, The step of doping the transition metal element into the first doped product includes: The transition metal source is mixed with the first doped product to obtain a second mixture; The second mixture is carbonized under an inert atmosphere to obtain the negative electrode active material.

14. The method for preparing the negative electrode active material according to claim 13, characterized in that, The step of mixing the transition metal source with the first doped product includes: The transition metal source and the first doped product are dissolved in a solvent to obtain a first solution; The first solution was dried to obtain the second mixture.

15. The method for preparing the negative electrode active material according to claim 13, characterized in that, In the second mixture, the mass ratio of the transition metal element to the first doped product ranges from 1:(28 to 32).

16. The method for preparing the negative electrode active material according to claim 13, characterized in that, The carbonization temperature of the first mixture is less than or equal to the carbonization temperature of the second mixture.

17. The method for preparing the negative electrode active material according to any one of claims 11 to 16, characterized in that, The carbonization temperature range for the first mixture is 200°C to 600°C; and / or, The carbonization time of the first mixture ranges from 1 hour to 10 hours.

18. The method for preparing the negative electrode active material according to any one of claims 13 to 16, characterized in that, The carbonization temperature range for the second mixture is 600°C to 1200°C; and / or, The carbonization time for the second mixture ranges from 1 hour to 10 hours.

19. The method for preparing the negative electrode active material according to any one of claims 10 to 16, characterized in that, The non-metallic source includes at least one of boric acid, urea, thiourea, sodium hypophosphite, ammonium fluoride, ammonium chloride, ammonium bromide, and ammonium iodide.

20. The method for preparing the negative electrode active material according to any one of claims 10 to 16, characterized in that, The transition metal salts include at least one of the following: ferric nitrate, cobalt nitrate, nickel nitrate, copper nitrate, zinc nitrate, and manganese chloride.

21. The method for preparing the negative electrode active material according to any one of claims 11 to 16, characterized in that, The carbon source includes at least one of bamboo charcoal, coconut shell, rice husk, asphalt, and coal.

22. A sodium-ion battery, characterized in that, include: A negative electrode and a positive electrode are arranged opposite to each other; the material of the negative electrode includes the negative electrode active material as described in any one of claims 1 to 9.

23. The sodium-ion battery according to claim 22, characterized in that, The reversible capacity of the sodium-ion battery under the first preset condition is in the range of 250mAh / g to 400mAh / g. The first preset condition includes charging and discharging at 0.08C to 0.12C, where 1C is 200mA / g.

24. The sodium-ion battery according to claim 22, characterized in that, The sodium-ion battery has a capacity retention rate of 35% to 45% under the second preset conditions, which include charging and discharging at 0.8C to 1.2C, where 1C is 200mA / g.

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