Preparation method of pre-sodium-modified sodium ion battery cell

Abstract

The invention discloses a preparation method of a pre-sodium-modified sodium ion battery cell, which comprises the following steps: taking a sodium ion battery cell without liquid injection, then injecting a pre-sodium-modified reagent into a liquid injection port, standing for full reaction, and then carrying out subsequent packaging formation. The preparation method of the pre-sodium-modified sodium ion battery cell has the characteristics of high energy density, accurate addition amount control and high applicability.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and specifically refers to a method for preparing a pre-sodiumated sodium ion battery cell. Background Art

[0002] Sodium-ion batteries (SIBs) are considered as a powerful alternative to lithium-ion batteries (LIBs) due to their low cost and abundant resources. However, the commercialization of SIBs is limited by the low initial coulombic efficiency (ICE) of negative electrode materials and the loss of active sodium. Pre-sodiumization technology compensates for the loss of active sodium in the first cycle by pre-supplementing active sodium during the battery manufacturing process, thereby improving the energy density and cycle life of the battery. At present, pre-sodiumization technology mainly includes short-circuiting method, electrochemical pre-sodiumization, physical pre-sodiumization of sodium metal and chemical pre-sodiumization. Short-circuiting method and physical pre-sodiumization of sodium metal usually require the use of active metallic sodium, strict operating conditions and potential safety hazards. Although electrochemical pre-sodiumization can achieve precise adjustment of the degree of pre-sodiumization, the operation process is cumbersome, which limits its large-scale application. Chemical pre-sodiumization uses liquid pre-sodiumization reagents, which can easily penetrate into the interior of porous electrodes to achieve efficient and uniform pre-sodiumization treatment. This method has advantages in safety and ease of operation.

[0003] The current research on chemical pre-sodiumization of sodium-ion batteries is limited to the positive or negative electrode. From the perspective of practical application, the integrated pre-sodiumization of the battery cell has more application prospects. At present, there are some inventions for pre-lithiation of lithium-ion batteries: For example, Chinese invention patent CN109119593B provides a lithium-copper composite electrode for pre-lithiation. After electrochemical pre-lithiation by constant current charge and discharge, the third electrode that is easy to be removed is taken out of the battery cell for secondary evacuation-packaging. However, this method is essentially electrochemical pre-lithiation. After pre-lithiation, the third electrode needs to be removed and packaged, which is complicated in actual operation.

[0004] For example, Chinese invention patent application CN201910418237.4 discloses a pre-lithiation method, which uses a lithium metal strip as the third electrode, connects the lithium metal strip and the negative electrode of the battery cell through an external power supply for charging, and realizes pre-lithiation of the negative electrode at the battery cell end. Electrochemical pre-lithiation using active metals is complicated and has safety risks.

[0005] In summary, today's pre-sodiumization technology is often limited to single-side treatment of the positive or negative electrode, such as through sacrificial salt method, electrochemical pre-sodiumization method, and chemical pre-sodiumization method. However, the sacrificial salt method is often affected by decomposition products, which greatly reduces the performance of the battery, and the electrochemical pre-sodiumization method is difficult to promote due to its cumbersome operation. Chemical pre-sodiumization has obvious advantages in safety and ease of operation, but today's chemical pre-sodiumization method is performed on the negative or positive electrode side before assembling the battery cell, but the positive and negative electrodes after pre-sodiumization are sensitive to air and water, which can easily lead to pre-sodiumization failure. Summary of the invention

[0006] The invention aims to provide a method for preparing a pre-sodiumized sodium ion battery cell, which has the characteristics of high energy density, precise control of addition amount and strong applicability.

[0007] The present invention can be implemented by the following technical solutions: The invention discloses a preparation method of a pre-sodiumized sodium ion battery cell, comprising the following steps: taking a sodium ion battery cell without liquid injection, then injecting a pre-sodiumization reagent into a liquid injection port, and performing subsequent encapsulation and formation after standing for sufficient reaction.

[0008] Further, the relationship between the amount of pre-sodium reagent added and the supplemented capacity is C 补 = C0*Vm*M x *M0*η, where C0 is the theoretical specific capacity of the pre-sodium reagent, V m is the volume of the pre-sodium reagent, M x is the molar concentration of the pre-sodium reagent, M0 is the molar mass of the pre-sodium reagent, η is the utilization rate of the pre-sodium reagent, and the theoretical specific capacity of the pre-sodium reagent C0=96485n / 3.6M0, where n is the charge transfer amount.

[0009] The invention proposes a method for pre-sodiumization of a cell of a high-energy sodium-ion battery, which is used to realize the integrated pre-sodiumization of the positive and negative electrodes of the sodium-ion battery cell to obtain a sodium-ion battery with high energy. The method selects the pre-sodiumization reagent according to the type of positive and negative electrode active materials, calculates the required amount of the pre-sodiumization reagent by the capacity to be supplemented, and quantitatively adds the pre-sodiumization reagent to the cell before injecting the electrolyte to realize the independent pre-sodiumization of the negative electrode and the positive electrode, as well as the integrated pre-sodiumization of the positive and negative electrodes of the cell, to obtain a sodium-ion battery with high energy.

[0010] Further, the solute of the pre-sodiumization reagent is a polycyclic aromatic hydrocarbon compound and / or an aromatic ketone compound, the polycyclic aromatic hydrocarbon compound is one or more of biphenyl, naphthalene, methyl biphenyl and its derivatives, the aromatic ketone compound is one or more of 9-fluorenone, benzophenone, methylfluorenone and its derivatives; the solvent is one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, methyltetrahydrofuran, 1,3-dioxolane. Specifically, the principle of solute selection is based on the sodium storage potential of the positive and negative electrodes, and the need for sodium supplementation, based on the feasibility of thermodynamic reactions, the highly reducing pre-sodiumization reagent and the electrode material selectively undergo spontaneous redox reactions, the sodium in the pre-sodiumization reagent is embedded in the electrode material, and the anion radical of the pre-sodiumization reagent itself is oxidized. If a pre-sodiumization reagent with a high reduction potential is selected, the positive electrode can be selectively pre-sodiumized, and if a low potential pre-sodiumization reagent is selected, the positive electrode and the negative electrode are reduced simultaneously.

[0011] Further, the concentration of the pre-sodium reagent is 0.1-2 mol / L, and the utilization rate of the added pre-sodium reagent is very high. The amount of the pre-sodium reagent active substance added is calculated according to the capacity to be supplemented. In order to ensure that the pre-sodium reagent can completely infiltrate the battery core and ensure the efficiency of pre-sodiumization, the concentration of the pre-sodium reagent is specified as above. If the concentration is too low, the pre-sodiumization efficiency is reduced, and if the concentration is too high, the battery core cannot be completely infiltrated. The molar amount of the pre-sodium reagent to be added is calculated according to the capacity to be supplemented and the theoretical capacity of the selected pre-sodium reagent, and the volume of the pre-sodium reagent added is calculated according to the concentration of the pre-sodium reagent. Specifically, the relationship between the amount of the pre-sodium reagent added and the supplemented capacity is C 补 =C0*Vm*M x *M0*η, where C0 is the theoretical specific capacity of the pre-sodium reagent, V m is the volume of the pre-sodium reagent, M x is the molar concentration of the pre-sodium reagent, M0 is the molar mass of the pre-sodium reagent, η is the utilization rate of the pre-sodium reagent, the theoretical specific capacity of the pre-sodium reagent C0 = 96485n / 3.6M0, and n is the charge transfer amount.

[0012] Furthermore, the standing time of the pre-sodiumized battery cell is 1-12 h. Different concentrations and different types of pre-sodiumized reagents have different reaction rates with electrode materials. The stronger the reducing property of the pre-sodiumized reagent and the higher the concentration, the faster the reaction rate and the faster the pre-sodiumized rate. The higher the reduction potential of the pre-sodiumized reagent, the milder the reducing property of the reagent and the slower the pre-sodiumized rate.

[0013] Furthermore, the sodium ion battery cell is also subjected to a washing and drying operation before being packaged and formed: a washing solvent is added to wash the battery cell, and then the battery cell is heated and dried to remove the washing solvent adsorbed on the electrode and the diaphragm; the washing solvent is recovered after rotary evaporation and can be used to prepare a pre-sodium reagent and a washing solvent.

[0014] Furthermore, in the washing and drying, the washing solvent is one or more of ethylene glycol dimethyl ether, tetrahydrofuran, methyltetrahydrofuran, and 1,3-dioxolane, and the pre-sodiumization reagent is added through the injection port. The active component anion radical in the reagent reduces the electrode material, and the anion radical itself is oxidized and still dissolved in the ether. The sodium ions are embedded in the material and the material reacts. The pre-sodiumization reagent after the reaction is poured out from the injection port, but a part of the pre-sodiumization reagent after the reaction is still immersed in the diaphragm or adsorbed on the electrode surface. The purpose of washing the inside of the battery cell is to dilute and dissolve the residue after the reaction of the pre-sodiumization reagent by repeatedly re-injecting the ether solvent into the injection port. After the reaction of the pre-sodiumization reagent, the oxidized component itself does not have electrochemical activity. If it is not fully washed, the energy density of the battery will be reduced, and the residue is very likely to have a negative impact on the cycle performance of the battery.

[0015] Furthermore, during washing and drying, the drying temperature is 60-100 °C and the drying time is 1-2 hours. The purpose of drying is to remove the solvent. After washing the battery cell, ether will be adsorbed on the surface of the electrode and the diaphragm will be soaked in ether. If it is not fully dried, after the ester electrolyte is injected, the ether and ester will be miscible, which will greatly affect the composition of the battery electrolyte and thus affect the battery performance.

[0016] Furthermore, in the sodium ion battery cell, the positive electrode material is a polyanion material, a Prussian blue material and / or a layered oxide material, and the negative electrode material is a hard carbon, a soft carbon and / or a combined negative electrode.

[0017] Furthermore, the polyanionic material is one or more of sodium iron pyrophosphate, sodium vanadium phosphate, sodium iron sulfate, and sodium manganese titanium phosphate.

[0018] The present invention provides a method for preparing a pre-sodiumized sodium ion battery cell, which has the following beneficial effects: First, the energy density is high. Through chemical pre-sodiumization of the battery cell, the pre-sodiumization reagent can spontaneously undergo redox reactions with the electrode material, and active sodium ions can be added to the negative electrode or positive electrode in advance to obtain sodium-rich positive electrode materials and sodium-storage negative electrode materials. The loss of active sodium caused by the formation of SEI during the charge and discharge process can be compensated, thereby improving the ICE of the battery. Through the pre-sodiumization technology, the high specific capacity of the negative electrode material can be fully utilized, and the utilization rate of the positive electrode material can be improved, thereby improving the energy density of the battery; Second, the amount of addition is precisely controlled and added by liquid injection. The injection amount of the pre-sodium reagent of the present invention is controllable, the reaction is uniform, and the depth of pre-sodiumization can be controlled according to the injection amount of the pre-sodium reagent. Third, it has strong applicability. The invention has the same requirements for the environmental atmosphere as the liquid injection process. It is applicable to various types of sodium battery cells, including soft-pack batteries, aluminum shell batteries, steel shell batteries, square batteries, cylindrical batteries, blade batteries, etc., without the need for additional standard atmosphere conditions. At the same time, the pre-sodiumized battery cells do not need to be reassembled, which can avoid the problem of pre-sodiumization failure. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the technical solution of the present invention, the product of the present invention is further described in detail below in conjunction with application examples.

[0020] The invention discloses a preparation method of a pre-sodiumized sodium ion battery cell, comprising the following steps: taking a sodium ion battery cell without liquid injection, then injecting a pre-sodiumization reagent into a liquid injection port, and performing subsequent encapsulation and formation after standing for sufficient reaction.

[0021] Further, the relationship between the amount of pre-sodium reagent added and the supplemented capacity is C 补 = C0*Vm*M x *M0*η, where C0 is the theoretical specific capacity of the pre-sodium reagent, V m is the volume of the pre-sodium reagent, M x is the molar concentration of the pre-sodium reagent, M0 is the molar mass of the pre-sodium reagent, η is the utilization rate of the pre-sodium reagent, and the theoretical specific capacity of the pre-sodium reagent C0=96485n / 3.6M0, where n is the charge transfer amount.

[0022] Furthermore, the solute of the pre-sodiumization reagent is a polycyclic aromatic hydrocarbon compound and / or an aromatic ketone compound, the polycyclic aromatic hydrocarbon compound is one or more of biphenyl, naphthalene, methylbiphenyl and their derivatives, the aromatic ketone compound is one or more of 9-fluorenone, benzophenone, methylfluorenone and their derivatives; the solvent is one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, methyltetrahydrofuran, and 1,3-dioxolane.

[0023] Further, the concentration of the pre-sodiumization reagent is 0.1 - 2 mol / L.

[0024] Furthermore, the standing time of the pre-sodiumized cells was 1-12 h at different concentrations.

[0025] Furthermore, before the sodium ion battery cell is packaged and formed, a washing and drying operation is performed: a washing solvent is added to wash the battery cell, and then the battery cell is heated and dried to remove the washing solvent adsorbed by the electrode and the diaphragm;.

[0026] Furthermore, in the washing and drying, the washing solvent is one or more of ethylene glycol dimethyl ether, tetrahydrofuran, methyltetrahydrofuran, and 1,3-dioxolane.

[0027] Furthermore, in the washing and drying, the drying temperature is 60-100° C. and the drying time is 1-2 hours.

[0028] Furthermore, in the sodium ion battery cell, the positive electrode material is a polyanion material, a Prussian blue material and / or a layered oxide material, and the negative electrode material is a hard carbon, a soft carbon and / or a combined negative electrode.

[0029] Furthermore, the polyanionic material is one or more of sodium iron pyrophosphate, sodium vanadium phosphate, sodium iron sulfate, and sodium manganese titanium phosphate.

[0030] Application Example 1 The present embodiment relates to a pre-sodiumized sodium ion battery cell, and the preparation method thereof comprises the following steps: S1: preparing a pre-sodium reagent, adding naphthalene and sodium to ethylene glycol dimethyl ether at a molar ratio of 1:1, stirring until completely dissolved, to obtain a 0.5 mol / L naphthalene sodium reagent solution; S2: Pre-sodiumization of the cell, the positive electrode sheet (sodium ferric pyrophosphate), the negative electrode sheet (hard carbon) and the separator (polyolefin separator) are combined into a cell, the capacity to be supplemented is 0.5 Ah, according to V m = C 补 / (C0*M x *M0*η) = 37.2 mL (where C 补 =0.5 Ah,M x = 0.5 mol / L, C0= 177.5 mAh / g, M0= 151.16 g / mol, η=100%), inject 37.2 mL of sodium naphthalene solution into the battery cell through the injection port, completely soak the electrode and let it stand for 4 h to compensate for the irreversible loss of 0.5 Ah of electricity; S3: washing and drying. After standing, the pre-sodium reagent and the electrode sheet react fully. The pre-sodium reagent after the reaction is poured out through the injection port, and methyltetrahydrofuran is re-injected into the battery cell from the injection port. The operation is repeated three times to clean the residue after the reaction of the pre-sodium reagent. The battery cell is then heated at 60 degrees Celsius for 2 hours to remove the washing solvent adsorbed on the diaphragm and the electrode sheet. The solvent in the washing liquid is recovered after rotary evaporation and can be used for preparing the pre-sodium reagent and washing. S4: packaging and formation, placing the battery cell in a soft-pack battery case, injecting the battery cell with liquid, packaging and forming the battery cell, and performing a cycle stability test on the battery after formation. The initial capacity of the battery is tested to be 1.95 Ah (the test results are shown in Table 1).

[0031] Application Example 2 The present embodiment relates to a pre-sodiumized sodium ion battery cell, and the preparation method thereof comprises the following steps: S1: Prepare a pre-sodium reagent, add 9-fluorenone and sodium in a molar ratio of 1:1 to ethylene glycol dimethyl ether, and stir until completely dissolved to obtain a 1 mol / L 9-fluorenone sodium solution; S2: Pre-sodiumization of the cell, the positive electrode sheet (sodium vanadium phosphate), the negative electrode sheet (hard carbon) and the separator (polyolefin separator) are combined into a cell, the capacity to be supplemented is 0.5 Ah, according to V m = C 补 / (C0*M x *M0*η) = 37.2 mL (where C 补 = 0.5 Ah, M x = 1 mol / L, C0= 120 mAh / g, M0= 180.2 g / mol, η=100%), inject 18.7 mL of 9-fluorenone sodium solution into the battery cell through the injection port, completely soak the electrode and let it stand for 8 hours to compensate for the irreversible loss of 0.5 Ah of electricity; S3: washing and drying. After standing, the pre-sodium reagent and the electrode sheet react fully. The pre-sodium reagent after the reaction is poured out through the injection port, and then ethylene glycol dimethyl ether is injected into the battery cell from the injection port again. The operation is repeated three times to clean the residue after the reaction of the pre-sodium reagent. The battery cell is then heated at 100 degrees Celsius for 1 hour to remove the washing solvent adsorbed on the diaphragm and the electrode sheet. The solvent in the washing liquid is recovered after rotary evaporation and can be used for preparing the pre-sodium reagent and washing. S4: packaging and formation, placing the battery cell in a soft-pack battery case, injecting liquid into the battery cell, packaging and forming the battery cell, and conducting a cycle stability test on the battery after formation. The initial capacity of the battery is tested to be 1.932Ah (the test results are shown in Table 1).

[0032] Application Example 3 The present embodiment relates to a pre-sodiumized sodium ion battery cell, and the preparation method thereof comprises the following steps: S1: Prepare a pre-sodium reagent, add benzophenone and sodium to ethylene glycol dimethyl ether at a molar ratio of 1:1, and stir until completely dissolved to obtain a 2 mol / L benzophenone sodium reagent solution. ; S2: Pre-sodiumization of the cell, the positive electrode sheet (sodium vanadium phosphate), the negative electrode sheet (hard carbon) and the separator (polyolefin separator) are wound to form a cell. The capacity to be supplemented is 0.5 Ah. m = C 补 / (C0*M x *M0*η) = 9.32 mL (where C 补 =0.5 Ah,M x= 1 mol / L, C0= 130.7 mAh / g, M0= 205 g / mol, η=100%), inject 9.32 mL of sodium benzophenone solution into the battery cell through the injection port, completely soak the electrode and let it stand for 8 hours to compensate for the irreversible loss of 0.5 Ah of electricity; S3: washing and drying. After standing, the pre-sodium reagent and the electrode sheet react fully. The pre-sodium reagent after the reaction is poured out through the injection port, and tetrahydrofuran is re-injected into the battery cell from the injection port. The operation is repeated three times to clean the residue after the reaction of the pre-sodium reagent. The battery cell is then heated at 100 degrees Celsius for 1 hour to remove the washing solvent adsorbed on the diaphragm and the electrode sheet. The solvent in the washing liquid is recovered after rotary evaporation and can be used for preparing the pre-sodium reagent and washing. S4: packaging and formation, placing the battery cell in a cylindrical battery case, injecting liquid into the battery cell, packaging and forming the battery cell, and performing a cycle stability test on the battery after formation. The initial capacity of the battery is tested to be 1.957Ah (the test results are shown in Table 1).

[0033] Application Example 4 The present embodiment relates to a pre-sodiumized sodium ion battery cell, and the preparation method thereof comprises the following steps: S1: Prepare a pre-sodium reagent, add biphenyl and sodium to ethylene glycol dimethyl ether at a molar ratio of 1:1, and stir until completely dissolved to obtain a 1 mol / L sodium biphenyl reagent solution. ; S2: Pre-sodiumization of the cell, the positive electrode sheet (sodium vanadium phosphate), the negative electrode sheet (nano-Sn) and the diaphragm (glass fiber diaphragm) are combined into a cell, the capacity to be supplemented is 0.6 Ah, according to V m = C 补 / (C0*M x *M0*η) = 24.05 mL (where C 补 =0.5 Ah,M x = 1 mol / L, C0= 141.2 mAh / g, M0= 177.19 g / mol, η=100%), inject 24.05 mL of sodium biphenyl reagent into the battery cell through the injection port, completely soak the electrode and let it stand for 12 h to compensate for the irreversible loss of 0.6 Ah of electricity; S3: Washing and drying. After standing, the pre-sodium reagent and the electrode sheet fully react. The pre-sodium reagent after the reaction is poured out through the injection port, and ethylene glycol dimethyl ether is re-injected into the battery cell from the injection port. The operation is repeated three times to clean the residue after the reaction of the pre-sodium reagent. The battery cell is then heated at 70 degrees Celsius for 3 hours to remove the washing solvent adsorbed on the diaphragm and the electrode. The solvent in the washing liquid is recovered after rotary evaporation and can be used for preparing the pre-sodium reagent and washing; S4: Packaging and formation, placing the battery cell in a square battery case, injecting liquid into the battery cell, packaging and forming the battery cell, and performing a cycle stability test on the battery after formation. The initial capacity of the battery is tested to be 1.943 Ah (the test results are shown in Table 1).

[0034] Comparative Example 1 Compared with Application Example 1, the main difference of this embodiment is that all the pre-sodiumization operations in Application Example 1 are cancelled, and the battery consisting of the positive electrode plate (sodium ferric pyrophosphate), the negative electrode plate (hard carbon) and the diaphragm (polyolefin diaphragm) battery cell is injected with liquid, packaged and activated, and the charge and discharge performance is tested. The capacity of the tested battery is 1.496 Ah (the test results are shown in Table 1).

[0035] Comparative Example 2 Compared with Application Example 2, the main difference of this embodiment is that all the pre-sodiumization operations in Application Example 2 are cancelled, and the battery consisting of the positive electrode plate (sodium vanadium phosphate), the negative electrode plate (hard carbon) and the diaphragm (polyolefin diaphragm) battery cell is injected with liquid, packaged and activated, and the charge and discharge performance is tested. The capacity of the tested battery is 1.499Ah (the test results are shown in Table 1).

[0036] Comparative Example 3 Compared with Application Example 3, the main difference of this embodiment is that all the pre-sodiumization operations in Application Example 2 are cancelled, and the battery consisting of the positive electrode plate (sodium vanadium phosphate), the negative electrode plate (hard carbon) and the diaphragm (polyolefin diaphragm) battery cell is injected with liquid, packaged and activated, and the charge and discharge performance is tested. The capacity of the tested battery is 1.497Ah (the test results are shown in Table 1).

[0037] Comparative Example 4 Compared with Application Example 3, the main difference of this embodiment is that all the pre-sodiumization operations in Application Example 2 are cancelled, and the battery consisting of the positive electrode plate (sodium vanadium phosphate), the negative electrode plate (nano-Sn) and the diaphragm (glass fiber diaphragm) battery cell is injected with liquid, packaged and activated, and the charge and discharge performance is tested. The capacity of the tested battery is 1.386Ah (the test results are shown in Table 1).

[0038] Table 1 Performance test results The pre-sodiumization method of the invention is simple, and the pre-sodiumization, washing, liquid injection, activation, etc. are compatible with the existing assembly process of soft-pack batteries, and no additional equipment is required. By chemically pre-sodiumizing the battery cells, the pre-sodiumized battery cells do not need to be reassembled, which can avoid the problem of pre-sodiumization failure. The invention is flexible in operation and highly controllable. The required reagents can be selected according to the electrode to be treated to achieve pre-sodiumization of the negative electrode, positive electrode or integrated battery cell.

[0039] The injection amount of the pre-sodiumization reagent of the invention is controllable, the reaction is uniform, and the depth of pre-sodiumization can be controlled according to the injection amount of the pre-sodiumization reagent. For example, for some positive electrode materials that lack sodium storage sites, a low-potential pre-sodiumization reagent can be selected. For example, in Application Example 1, a low-reduction-potential pre-sodiumization reagent sodium naphthalene is added according to the calculated capacity to achieve pre-sodiumization of the negative electrode. As in Application Example 2, the positive electrode used is sodium vanadium phosphate, and a high-potential pre-sodiumization reagent sodium 9-fluorenone is selected to achieve pre-sodiumization of the positive electrode. For Application Example 4, a low-potential pre-sodiumization reagent sodium biphenyl is selected to achieve pre-sodiumization of both the positive and negative electrodes. For Application Example 3, the universality of this method is demonstrated, and it is not only applicable to soft-pack batteries, but also to aluminum shells, steel shells, and cylindrical batteries.

[0040] In addition, according to Table 1, the pre-sodiumization method of the invention can generate a solid electrolyte layer in situ at the electrode-electrolyte interface of the positive and negative electrodes, which can not only effectively improve the energy density of the battery, but also improve the stability of the battery interface, which is beneficial to improving the cycle stability of the battery.

[0041] The above application embodiments are only specific application embodiments of the present invention, and their descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and these obvious replacement forms all belong to the protection scope of the present invention.

Claims

1. A method for preparing a pre-sodiumized sodium ion battery cell, characterized in that The method comprises the following steps: taking a sodium ion battery cell which has not been injected with liquid, injecting a pre-sodiumization reagent into the injection port, and performing subsequent encapsulation and formation after standing for sufficient reaction.

2. The method for preparing a pre-sodiumized sodium ion battery cell according to claim 1, wherein: The relationship between the amount of the pre-sodium reagent added and the supplemented capacity is C 补 = C0*Vm*M x *M0*η, where C0 is the theoretical specific capacity of the pre-sodium reagent, V m is the volume of the pre-sodium reagent, M x is the molar concentration of the pre-sodium reagent, M0 is the molar mass of the pre-sodium reagent, η is the utilization rate of the pre-sodium reagent, the theoretical specific capacity of the pre-sodium reagent C0 = 96485n / 3.6M0, and n is the charge transfer amount.

3. The method for preparing a pre-sodiumized sodium ion battery cell according to claim 2, wherein: The solute of the pre-sodiumization reagent is a polycyclic aromatic hydrocarbon compound and / or an aromatic ketone compound, the polycyclic aromatic hydrocarbon compound is one or more of biphenyl, naphthalene, methyl biphenyl and their derivatives, the aromatic ketone compound is one or more of 9-fluorenone, benzophenone, methylfluorenone and their derivatives; the solvent is one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, methyltetrahydrofuran and 1,3-dioxolane.

4. The method for preparing a pre-sodiumized sodium ion battery cell according to claim 3, wherein: The concentration of the pre-sodium reagent is 0.1 - 2 mol / L, and the utilization rate of the added pre-sodium reagent is very high.

5. The method for preparing a pre-sodiumized sodium ion battery cell according to claim 4, wherein: The standing time of the pre-sodiumized cells is 1-12 h at different concentrations.

6. The method for preparing a pre-sodiumized sodium ion battery cell according to claim 5, wherein: Before the sodium ion battery cells are packaged and formed, they are also washed and dried: a washing solvent is added to wash the battery cells, and then the battery cells are heated and dried to remove the washing solvent adsorbed by the electrodes and diaphragms.

7. The method for preparing a pre-sodiumized sodium ion battery cell according to claim 6, wherein: In the washing and drying, the washing solvent is one or more of ethylene glycol dimethyl ether, tetrahydrofuran, methyltetrahydrofuran and 1,3-dioxolane.

8. The method for preparing a pre-sodiumized sodium ion battery cell according to claim 7, wherein: In the washing and drying, the drying temperature is 60-100°C; the drying time is 1-2h.

9. The method for preparing a pre-sodiumized sodium ion battery cell according to claim 8, wherein: In the sodium ion battery cell, the positive electrode material is a polyanion material, a Prussian blue material and / or a layered oxide material, and the negative electrode material is a hard carbon, a soft carbon and / or a combined negative electrode.

10. The method for preparing a pre-sodiumized sodium ion battery cell according to claim 9, characterized in that: The polyanionic material is one or more of sodium iron pyrophosphate, sodium vanadium phosphate, sodium iron sulfate, and sodium manganese titanium phosphate.

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