Pre-sodium-modified sodium ion battery negative electrode, preparation method thereof and sodium ion battery

Abstract

The invention relates to a pre-sodium-modified sodium ion battery negative electrode, a preparation method thereof and a sodium ion battery, and belongs to the technical field of sodium ion batteries. The battery negative electrode comprises a pre-sodium-modified negative electrode plate and a conductive polymer layer coated on the outer surface of the pre-sodium-modified negative electrode plate. The pre-sodium-modified layer is formed on the outer surface of the negative pole piece, and the conductive polymer layer covers the surface of the pre-sodium-modified layer, so that the problem that the pre-sodium-modified negative pole piece is unstable in the air is effectively solved, and meanwhile, the problems that the sodium amount of pre-embedded sodium or sodium supplement is inactivated and the like are also avoided; the stable pre-sodium-modified sodium ion battery negative electrode provided by the invention can realize the effects of improving the coulombic efficiency (reaching about gt, 85%) and the cycle capacity retention ratio (reaching about gt, 92%) of the battery.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, and specifically relates to a pre-sodium-treated sodium-ion battery negative electrode and its preparation method, as well as a sodium-ion battery. Background Technology

[0002] In recent years, the lithium-ion battery industry has developed rapidly. Due to their high energy density and excellent cycle performance, lithium-ion batteries have been widely used in various fields such as automotive power, power storage, portable electronic products, and power tools. However, as the application areas of lithium-ion batteries continue to expand, their demand is also increasing, while the shortage of lithium resources is becoming an obstacle to their large-scale application.

[0003] Compared to lithium, sodium is more abundant in the Earth's crust, providing a highly competitive cost advantage and resource supply for the future widespread application of sodium-ion batteries. Similar to lithium-ion batteries, during the first charge and discharge cycle, sodium-ion batteries irreversibly consume active sodium ions from the positive electrode due to the formation of an SEI film on the negative electrode surface, resulting in a decrease in reversible capacity and a shortened cycle life.

[0004] Currently, pre-sodiuming is the most direct and universal method to compensate for the loss of active sodium in the negative electrode. Pre-sodiuming involves adding extra active sodium to the negative or positive electrode in advance to compensate for the irreversible capacity loss during the first charge-discharge cycle, thereby significantly improving the energy density and cycle life of the entire battery.

[0005] For example, Chinese patent application CN108336301A discloses a pre-sodiuming method for the negative electrode of a sodium-ion battery. This method involves depositing a layer of metallic sodium on the surface of the active material of the negative electrode sheet, thereby compensating for sodium ion loss caused by the formation of an SEI film or other side reactions during the first charge of the battery. This reduces the loss of active sodium ions in the positive electrode material and improves the initial coulombic efficiency of the sodium-ion battery. Furthermore, this patent application uses physical vapor deposition (PVD) to deposit metallic sodium, further enhancing the performance of the sodium-ion battery.

[0006] Furthermore, Chinese patent application CN116169290A discloses the application of a sodium-supplementing additive in the preparation of cathode materials for sodium-ion batteries. In this application, at least one of disodium iminodiacetate, trisodium nitrilotriacetate, and trisodium dicarboxymethylalanine is used as a sodium-supplementing additive in the preparation of the cathode material. These sodium-supplementing additives undergo irreversible oxidative decomposition during the first charge of the battery, releasing sodium ions. This compensates for the irreversible sodium capacity loss at the negative electrode caused by SEI film formation and other side reactions, thereby improving the battery's coulombic efficiency and energy density.

[0007] However, compared to the pre-lithiation process for lithium-ion batteries, the pre-sodiumization process faces many unresolved industrialization challenges. For example, compared to metallic lithium, metallic sodium lacks the protection of a surface passivation layer, making it more reactive and less stable in air, thus posing a greater risk in practical production applications. Therefore, pre-sodiumization using metallic sodium is more difficult than pre-lithiation. Furthermore, pre-sodiumized negative electrodes, due to pre-intercalation or sodium replenishment, exhibit higher electrode activity. Substances such as O2 and CO2 in the air readily react with the sodium in the electrode, causing sodium loss and preventing pre-sodiumization from achieving its intended effect of improving initial efficiency and capacity. Therefore, one of the key aspects of applying pre-sodiumization technology lies in improving the stability of the pre-sodiumized electrode. Summary of the Invention

[0008] To address the above problems, this invention provides a pre-sodium-modified sodium-ion battery negative electrode, its preparation method, and a sodium-ion battery.

[0009] The first objective of this invention is to provide a pre-sodium-treated sodium-ion battery negative electrode, comprising a pre-sodium-treated negative electrode sheet and a conductive polymer layer coated on the outer surface of the pre-sodium-treated negative electrode sheet.

[0010] In a specific embodiment of the present invention, the pre-sodium-treated negative electrode sheet includes a negative electrode sheet and a pre-sodium-treated layer covering the outer surface of the negative electrode sheet.

[0011] In a specific embodiment of the present invention, the pre-sodiumization layer is a polycyclic aromatic hydrocarbon sodium layer.

[0012] In a specific embodiment of the present invention, the raw material for the polycyclic aromatic hydrocarbon sodium layer is one or more of sodium anthracene, sodium naphthalene, and sodium biphenyl in any ratio.

[0013] In a specific embodiment of the present invention, the thickness of the pre-sodiumized layer is 5-10 μm.

[0014] In a specific embodiment of the present invention, the thickness of the pre-sodium coating is preferably in the range of about 5 to about 10 μm, for example, about 6 μm, about 7 μm, about 8 μm, or about 9 μm. Here, the thickness of the pre-sodium coating should not be too large or too small, for example, it should not exceed about 10 μm, such a pre-sodium coating thickness will not have a negative impact on the battery due to the presence of the sodium-replenishing coating; nor should it be less than about 5 μm, such a pre-sodium coating thickness can provide sufficient sodium ions to compensate for the capacity loss of the negative electrode while ensuring battery performance.

[0015] In a specific embodiment of the present invention, the conductive polymer in the conductive polymer layer is one or more of polypyrrole, polythiophene, and polyaniline in any ratio.

[0016] In a specific embodiment of the present invention, the thickness of the conductive polymer layer is 5-20 μm.

[0017] In a specific embodiment of the present invention, the thickness of the conductive polymer layer is in the range of about 5 to about 20 μm, for example, about 10 μm or about 15 μm. Here, the thickness of the conductive polymer layer should not be too large, for example, not exceeding about 20 μm, otherwise it will easily lead to a decrease in battery energy density, nor should it be too small, for example, not less than about 5 μm, otherwise it will be difficult to ensure the stability of the pre-sodiumized electrode in air.

[0018] In a specific embodiment of the present invention, the negative electrode sheet is composed of a foil and an active layer formed on the foil, and the raw materials of the active layer include a mixture of negative electrode active material, conductive agent and binder.

[0019] In a specific embodiment of the present invention, the negative electrode active material is one or more of hard carbon and soft carbon in any ratio.

[0020] In a specific embodiment of the present invention, the conductive agent is one or more of carbon nanotubes and conductive carbon black in any ratio.

[0021] In a specific embodiment of the present invention, the adhesive is one or more of polyvinylidene fluoride, carboxymethyl cellulose and polyacrylic acid in any ratio.

[0022] In a specific embodiment of the present invention, the mass ratio of the negative electrode active material, the conductive agent, and the binder in the active layer is 100:2-12:3-12.

[0023] In a specific embodiment of the present invention, based on 100 parts by weight of the negative electrode active material, the amount of the conductive agent can be in the range of about 2 to about 12 parts by weight (e.g., about 4 parts by weight, about 6 parts by weight, about 8 parts by weight, or about 10 parts by weight), and the amount of the binder can be in the range of about 3 to about 12 parts by weight (e.g., about 4 parts by weight, about 6 parts by weight, about 8 parts by weight, or about 10 parts by weight). Here, on the one hand, the weight fraction of the conductive agent should not be too high, for example, it should not exceed about 12% by weight of the negative electrode active material, otherwise it may reduce the energy density of the sodium-ion battery and also lead to increased polarization; on the other hand, the weight fraction of the conductive agent should not be too low, for example, it should not be less than about 2% by weight of the negative electrode active material, otherwise it may reduce the electron conduction channels, which is not conducive to high-current charging and discharging; it will cause a decrease in battery capacity and also lead to a shorter cycle life of the battery. On the other hand, the amount of binder should not be too high, for example, it should not exceed about 12% by weight of the negative electrode active material, otherwise it may increase the internal resistance of the battery, resulting in a decrease in battery performance and also a decrease in battery energy density; the amount of binder should not be too low, for example, it should not be less than about 3% by weight of the negative electrode active material, otherwise it may cause the battery electrode to fall off, damage the internal structure of the battery, and shorten the battery cycle life.

[0024] A second objective of this invention is to provide a method for preparing a pre-sodium-modified sodium-ion battery negative electrode, comprising: An organic solution of sodium polycyclic aromatic hydrocarbons is coated onto the outer surface of the negative electrode sheet and dried to obtain a pre-sodiumized negative electrode sheet. An organic solution of a conductive polymer is coated onto the outer surface of a pre-sodium-treated negative electrode sheet, and then dried to obtain the battery negative electrode.

[0025] In specific embodiments of the present invention, the organic solution coating method of the sodium polycyclic aromatic hydrocarbon includes spraying, roller coating, scraping, and dipping.

[0026] In a specific embodiment of the present invention, the drying time is 15-50 min during the process of obtaining the pre-sodiumized negative electrode sheet.

[0027] After the organic solution of sodium polycyclic aromatic hydrocarbons (PAHs) is coated onto the negative electrode sheet, the PAHs in the organic solution react with the negative electrode material contained in the active layer, thereby embedding sodium in the negative electrode. Here, the reaction time between the PAHs organic solution and the negative electrode active material contained in the active layer is generally not limited, but in some preferred exemplary embodiments of the present invention, the drying time can be in the range of about 15 to 50 minutes, for example, about 20 minutes, about 30 minutes, or about 40 minutes. The setting of the drying time is mainly related to the concentration of the solution used; a lower concentration of the reagent requires a longer time, and a higher concentration requires a shorter time; the main purpose is to ensure sufficient reaction between the negative electrode material and the PAHs. Furthermore, after the reaction is complete, in order to remove excess unreacted pre-sodiumization reagent, it is preferable to rinse the pre-sodiumization reagent with a washing solution. The washing solution includes, but is not limited to, toluene.

[0028] In a specific embodiment of the present invention, the concentration of the organic solution of the sodium polycyclic aromatic hydrocarbon is 0.1-10 mol / L.

[0029] In a specific embodiment of the present invention, the concentration of the organic solution of the sodium polycyclic aromatic hydrocarbon is in the range of about 0.1 to about 10 mol / L (e.g., about 0.25 mol / L, about 0.5 mol / L, about 1 mol / L or about 5 mol / L).

[0030] In the organic solution of the sodium polycyclic aromatic hydrocarbon, the concentration of the sodium polycyclic aromatic hydrocarbon should not exceed about 10 mol / L, otherwise the degree of pre-sodiumization may be too high. In addition, the concentration of the pre-sodiumization reagent should not be lower than about 0.1 mol / L, otherwise the degree of pre-sodiumization may not meet the requirements.

[0031] In a specific embodiment of the present invention, the organic solvent in the organic solution of the sodium polycyclic aromatic hydrocarbon is one or more of ethylene glycol diethyl ether, ethylene glycol monomethyl ether, and ethylene glycol dimethyl ether in any ratio.

[0032] In a specific embodiment of the present invention, the concentration of the organic solution of the conductive polymer is 20-50 mg / mL.

[0033] In a specific embodiment of the present invention, the concentration of the organic solution of the conductive polymer is in the range of about 20 to about 50 mg / mL (e.g., about 30 mg / mL, about 40 mg / mL, or about 50 mg / mL). The concentration of the conductive polymer solution should not exceed about 50 mg / mL, as a conductive polymer layer formed by a conductive polymer solution with an excessively high concentration may be too thick, leading to an increase in the battery's internal resistance. In addition, the concentration of the conductive polymer solution should not be lower than about 20 mg / mL, as a conductive polymer layer formed by a conductive polymer solution with an excessively low concentration may not be able to effectively protect the pre-sodiumization layer.

[0034] The organic solution of the conductive polymer can be obtained by mixing the conductive polymer and the organic solvent in one step. For example, the conductive polymer solution can be obtained by thoroughly mixing the conductive polymer and the organic solvent at a stirring speed of about 300 to about 500 rpm, a stirring time of about 60 to about 90 minutes, and a stirring temperature of about 60 to about 100°C.

[0035] In a specific embodiment of the present invention, the organic solvent in the organic solution of the conductive polymer is one or more of the following in any proportion: diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, methyl tert-butyl ether, acetonitrile, N,N-dimethylformamide, tetrahydrofuran, chloroform, and dimethyl sulfoxide.

[0036] In a specific example of the present invention, the organic solution coating method of the conductive polymer includes spraying, roller coating, blade coating, and dipping.

[0037] In a specific example of the present invention, the drying includes freeze drying, oven drying, vacuum drying, and air drying.

[0038] A third objective of this invention is to provide a sodium-ion battery, comprising the aforementioned pre-sodiumized sodium-ion battery negative electrode or the battery negative electrode prepared by the aforementioned preparation method.

[0039] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. The term "about" as used in this invention indicates that the number it modifies may fluctuate within ±20%, ±15%, ±10%, ±5%, or ±2% of that number. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0040] The beneficial effects of this invention are: This invention discloses a pre-sodium-modified sodium-ion battery negative electrode and its preparation method, as well as a sodium-ion battery. By setting a double layer on the surface of the sodium-ion battery negative electrode sheet, namely a pre-sodium-modified layer formed on the outer surface of the negative electrode sheet and a conductive polymer layer covering the surface of the pre-sodium-modified layer, the problem of instability of the pre-sodium-modified negative electrode sheet in air is effectively solved. At the same time, it also avoids problems such as sodium deactivation caused by pre-sodium insertion or sodium supplementation. The stable pre-sodium-modified sodium-ion battery negative electrode of this invention can achieve the effect of improving the battery coulombic efficiency (reaching about >85%) and cycle capacity retention (reaching about >92%).

[0041] In addition, the method for preparing the stable pre-sodium-ion battery anode of the present invention is simple to operate and easy to scale up for production.

[0042] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description and claims. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] The raw materials used in the following examples and comparative examples were all commercially available analytical grade raw materials.

[0045] The negative electrode sheet used consists of a foil and an active layer formed on the foil. The raw materials of the active layer include a negative electrode active material, a conductive agent and a binder in a weight ratio of approximately 92:4:4. The negative electrode active material is hard carbon, the conductive agent is conductive carbon black SuperP, and the binder is polyvinylidene fluoride.

[0046] The polythiophene used was T1101 polythiophenol stock solution (with an electrical conductivity of approximately 10) purchased from Insee New Materials Co., Ltd. -2 To about 10 -1 (within the range of S / cm).

[0047] Example 1: Sodium-ion battery negative electrode: A solution of sodium biphenyl (pre-sodiumizing agent) in ethylene glycol diethyl ether at a concentration of approximately 0.5 mol / L was continuously sprayed onto the surface of the negative electrode sheet for approximately 45 minutes to allow excess sodium biphenyl to react with the negative electrode material, thereby intercalating sodium ions into the negative electrode sheet. The hard carbon negative electrode sheet coated with sodium biphenyl was then washed with toluene to remove excess unreacted sodium biphenyl. After drying (60–80 °C), a hard carbon negative electrode sheet with a pre-sodiumizing layer was obtained. The thickness of the pre-sodiumizing layer formed on the surface of the negative electrode sheet was approximately 8 μm.

[0048] A tetrahydrofuran solution of polythiophene with a concentration of approximately 25 mg / mL was roll-coated onto the surface of a hard carbon negative electrode sheet with a pre-sodiumized layer obtained above, ensuring that the coating solution completely covers the pre-sodiumized layer. After roll coating, the negative electrode sheet was dried (60-80°C) to obtain a stable pre-sodiumized sodium-ion battery negative electrode. The amount of solution used in the roll coating resulted in a polythiophene layer with a pre-sodiumized layer thickness of approximately 10 μm.

[0049] Example 2 Sodium-ion battery negative electrode: A stable pre-sodium-ion battery anode was prepared using a process similar to that in Example 1, except that: The concentration of the sodium biphenyl in ethylene glycol diethyl ether solution used was about 2.5 mol / L, the continuous spraying time was about 35 minutes, and the thickness of the pre-sodium layer formed on the surface of the negative electrode was about 7 μm.

[0050] Example 3 Sodium-ion battery negative electrode: A stable pre-sodium-ion battery anode was prepared using a process similar to that in Example 1, except that: The concentration of the sodium biphenyl in ethylene glycol diethyl ether solution used was about 5 mol / L, the spraying time was about 20 minutes, and the thickness of the pre-sodium layer formed on the surface of the negative electrode was about 9 μm.

[0051] In Examples 1 to 3 above, different concentrations of sodium biphenyl reagent can be used to obtain pre-sodiumized layers that achieve different amounts of sodium replenishment.

[0052] Example 4 Sodium-ion battery negative electrode: A stable pre-sodium-ion battery anode was prepared using a process similar to that in Example 1, except that: A sodium naphthalene glycol diethyl ether solution was used as a pre-sodiumization reagent instead of the sodium biphenyl glycol diethyl ether solution.

[0053] Example 5 Sodium-ion battery negative electrode: A stable pre-sodium-ion battery anode was prepared using a process similar to that in Example 1, except that: By adjusting the amount of polythiophene solution applied by roller coating, the thickness of the polythiophene layer coated with the pre-sodiumized layer is adjusted to approximately 20 μm.

[0054] Comparative Example 1 Sodium-ion battery negative electrode: A tetrahydrofuran solution of polythiophene with a concentration of approximately 25 mg / mL was roll-coated onto the surface of a hard carbon negative electrode sheet. After roll coating, the negative electrode sheet was dried to obtain a sodium-ion battery negative electrode. The thickness of the polythiophene layer was approximately 10 μm.

[0055] Comparative Example 2 Sodium-ion battery negative electrode: A 0.5 mol / L solution of sodium biphenyl in ethylene glycol diethyl ether (pre-sodiumization reagent) was continuously sprayed onto the surface of a hard carbon negative electrode sheet. This allowed the sodium biphenyl to react with the negative electrode material, intercalating sodium ions into the negative electrode sheet. The hard carbon negative electrode sheet coated with the sodium biphenyl reagent was then washed with toluene to remove excess unreacted sodium biphenyl, resulting in a hard carbon negative electrode sheet with a pre-sodiumization layer. The spraying time was approximately 45 minutes, resulting in a pre-sodiumization layer thickness of approximately 5 μm covering the negative electrode sheet.

[0056] Comparative Example 3 Sodium-ion battery negative electrode: A stable pre-sodium-ion battery anode was prepared using a process similar to that in Example 1, except that: The concentration of the sodium biphenyl in ethylene glycol diethyl ether solution used was about 0.05 mol / L, the spraying time was about 20 minutes, and the thickness of the pre-sodium layer formed on the surface of the negative electrode was about 3 μm.

[0057] Comparative Example 4 Sodium-ion battery negative electrode: A stable pre-sodium-ion battery anode was prepared using a process similar to that in Example 1, except that: The concentration of the sodium biphenyl in ethylene glycol diethyl ether solution used was about 12.0 mol / L, the spraying time was about 20 minutes, and the thickness of the pre-sodium layer formed on the surface of the negative electrode was about 11 μm.

[0058] Comparative Example 5 Sodium-ion battery negative electrode: A stable pre-sodium-ion battery anode was prepared using a process similar to that in Example 1, except that: The thickness of the polythiophene layer is approximately 3 μm.

[0059] Comparative Example 6 Sodium-ion battery negative electrode: A stable pre-sodium-ion battery anode was prepared using a process similar to that in Example 1, except that: The thickness of the polythiophene layer is approximately 25 μm.

[0060] The process parameters for preparing sodium-ion battery negative electrode sheets in Examples 1 to 5 and Comparative Examples 1 to 6 are shown in Table 1 below.

[0061] Table 1

[0062] NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Using O2 as the positive electrode, and the negative electrode sheets prepared in Examples 1 to 5 and Comparative Examples 1 to 6 above as the negative electrode, a sodium hexafluorophosphate solution with a concentration of approximately 1.3 mol / L (the solvent containing ethylene carbonate (EC) and dimethyl carbonate (DEC) in a volume ratio of approximately 1:1) was used as the electrolyte, and Celegard 2400 was used as the separator, a 5 Ah soft-pack sodium-ion battery was assembled. The cycle performance of this sodium-ion battery was tested under the following conditions: charge / discharge voltage of approximately 1.5 to approximately 3.95 V, temperature of approximately 25 ± 3.0 °C, and charge / discharge rate of approximately 0.5 C / 0.5 C.

[0063] The coulombic efficiency and cycle performance test results of the sodium-ion batteries of Examples 1 to 5 and Comparative Examples 1 to 6 of the present invention are shown in Table 2 below.

[0064] Table 2

[0065] As can be seen from the test results in Table 2 above, the coulombic efficiency of the sodium-ion batteries in Examples 1 to 5 of the present invention can reach over 85%, which is much higher than the coulombic efficiency of approximately 80.4% of the sodium-ion battery in Comparative Example 1. The capacity retention rate of the sodium-ion batteries in Examples 1 to 5 of the present invention after 1500 cycles can reach over 92%, which is much higher than the capacity retention rate of approximately 88.2% of the sodium-ion battery in Comparative Example 1 after 1500 cycles. Furthermore, compared to Comparative Example 2, the coulombic efficiency and capacity retention rate of the sodium-ion batteries in Examples 1 to 5 are also about 3% higher.

[0066] The test results from Comparative Examples 3 to 6 show that, within the same reaction time, a high concentration of pre-sodiumizing reagent can provide more sodium replenishment, but when the concentration is too high, the sodium replenishment effect is not significant. Meanwhile, increasing the thickness of the protective layer (i.e., the conductive polymer layer) may increase the battery's internal resistance, leading to a decrease in capacity retention; however, if the protective layer thickness is too low, it may not provide effective protection, resulting in the loss of some sodium replenishment. Therefore, the protective layer thickness should be moderate.

[0067] Embodiments 1 to 5 of the present invention effectively solve the problem of instability of pre-sodium-treated negative electrode sheets in air by forming a conductive polymer coating on the surface of the pre-sodium-treated negative electrode sheet, and at the same time solve the problem of sodium deactivation caused by pre-sodium insertion or sodium supplementation, so that the negative electrode sheet can achieve the effect of improving the battery coulombic efficiency and capacity retention rate after cycle.

[0068] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pre-sodium-treated sodium-ion battery negative electrode, characterized in that, It includes a pre-sodium-treated negative electrode sheet and a conductive polymer layer covering the outer surface of the pre-sodium-treated negative electrode sheet.

2. The pre-sodium-treated sodium-ion battery negative electrode according to claim 1, characterized in that, The pre-sodium-treated negative electrode sheet includes a negative electrode sheet and a pre-sodium-treated layer covering the outer surface of the negative electrode sheet.

3. The pre-sodium-treated sodium-ion battery negative electrode according to claim 2, characterized in that, The pre-sodiumized layer is a polycyclic aromatic hydrocarbon sodium layer.

4. The pre-sodium-treated sodium-ion battery negative electrode according to claim 3, characterized in that, The raw material for the polycyclic aromatic hydrocarbon sodium layer is one or more of sodium anthracene, sodium naphthalene, and sodium biphenyl in any ratio.

5. The pre-sodium-treated sodium-ion battery negative electrode according to claim 2, characterized in that, The thickness of the pre-sodiumized layer is 5-10 μm.

6. The pre-sodium-treated sodium-ion battery negative electrode according to claim 1, characterized in that, The conductive polymer in the conductive polymer layer is one or more of polypyrrole, polythiophene, and polyaniline in any ratio; and / or The thickness of the conductive polymer layer is 5-20 μm.

7. A pre-sodium-treated sodium-ion battery negative electrode according to any one of claims 1-6, characterized in that, The negative electrode sheet consists of a foil and an active layer formed on the foil. The active layer is made from a mixture of negative electrode active material, conductive agent, and binder; and / or The negative electrode active material is one or more of hard carbon and soft carbon in any ratio; and / or The conductive agent is one or more of carbon nanotubes and conductive carbon black in any ratio; and / or The adhesive is one or more of polyvinylidene fluoride, carboxymethyl cellulose, and polyacrylic acid in any ratio; and / or In the active layer, the mass ratio of the negative electrode active material, the conductive agent, and the binder is 100:2-12:3-12.

8. A method for preparing a pre-sodium-ion battery negative electrode according to any one of claims 1-7, characterized in that, include: An organic solution of sodium polycyclic aromatic hydrocarbons is coated onto the outer surface of the negative electrode sheet and dried to obtain a pre-sodiumized negative electrode sheet. An organic solution of a conductive polymer is coated onto the outer surface of a pre-sodium-treated negative electrode sheet, and then dried to obtain the battery negative electrode.

9. The method for preparing a pre-sodium-ion battery negative electrode according to claim 8, characterized in that, The concentration of the organic solution of the sodium polycyclic aromatic hydrocarbon is 0.1-10 mol / L; The concentration of the organic solution of the conductive polymer is 20-50 mg / mL.

10. A sodium-ion battery, characterized in that, Includes a pre-sodium-ion battery negative electrode according to any one of claims 1-7.

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