Sodium supplementing method of sodium ion battery and sodium ion battery supplemented with sodium

Abstract

The invention provides a sodium supplementing method of a sodium ion battery and a sodium ion battery after sodium supplementation, the sodium supplementing method comprises the following steps: (1) coating an initial negative plate with a sodium supplementing agent slurry to obtain a coated negative plate; a sodium supplementing agent in the sodium supplementing agent slurry comprises sodium nitride; and (2) carrying out heat treatment on the coated negative plate obtained in the step (1), and then carrying out battery assembly to obtain the sodium-supplemented sodium ion battery, or carrying out bare battery assembly on the coated negative plate obtained in the step (1) to obtain a bare battery, carrying out thermal formation on the obtained bare battery, and preparing the sodium-supplemented sodium ion battery by using the thermally formed bare battery. The sodium-supplemented sodium ion battery obtained by the sodium supplementing method not only has relatively high first coulombic efficiency and cycling stability, but also has relatively high energy density.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries and relates to a method for replenishing sodium of a sodium ion battery, and in particular to a method for replenishing sodium of a sodium ion battery and a sodium ion battery after replenishing sodium. Background Art

[0002] In the initial cycle of sodium-ion batteries, some irreversible reactions such as the formation of the SEI film on the negative electrode surface will cause the loss of sodium in the system, resulting in a low first coulombic efficiency of the negative electrode material, which is one of the main obstacles affecting the energy density of sodium-ion batteries. Compared with half-cells, this consumption is particularly obvious in full cells. This is because the SEI film formed during the first charge and discharge consumes sodium ions, and this part of the consumption is irreversible. Therefore, the key to restricting its cycle stability and energy density in the full battery lies in the irreversible consumption of limited sodium ions. At present, researchers have done a lot of work in terms of material and electrolyte design to reduce the irreversible capacity loss in sodium-ion batteries, but sodium consumption is difficult to completely eliminate. Therefore, pre-sodiumization of sodium-ion batteries has become an important solution to the above problems. At present, pre-sodiumization has been widely studied in sodium-ion batteries, sodium-ion capacitors, and dual-ion batteries.

[0003] The pre-sodiumization method of positive electrode additives has the advantages of low cost, high performance, simple operation and high safety, and is currently the pre-sodiumization method with the greatest commercial potential. However, the pre-sodiumization method of positive electrode additives will inevitably be adversely affected by the "dead mass" and "dead volume" produced by the positive electrode additives or the harmful gases released, affecting the utilization rate of the positive electrode active materials, reducing the overall energy density of the battery, and causing capacity decay during the long cycle of the battery. In addition, the compatibility of the sodiumization additive with the positive electrode material must also be considered, which limits the choice of positive electrode materials.

[0004] Pre-sodiumization of the negative electrode can also effectively compensate for the sodium ions consumed by reactions such as SEI film formation, more significantly improve the first coulombic efficiency (ICE), alleviate the problem of insufficient sodium content in the positive electrode material, and provide flexibility for the development of high energy density batteries.

[0005] The physical method based on metallic sodium powder or sodium foil is the most direct pre-sodiumization method, but it has the most stringent requirements on the atmosphere; and because metallic sodium is extremely active, it will react violently when exposed to air, making this method less safe and difficult to achieve large-scale commercial application. In addition, physical methods for pre-sodiumization will also lead to the formation of sodium dendrites and thermal runaway of the battery. The electrochemical pre-sodiumization method can form a uniform SEI film and obtain a good pre-sodiumization effect, but the cumbersome process greatly increases the cost of this method. The pre-sodiumization of the negative electrode of the sodium ion battery by liquid immersion and chemical spraying shows a good ability to compensate for the loss of active sodium ions, but since anions will be formed in the electrolyte during the pre-sodiumization process, the uniformity and density of the SEI film are affected.

[0006] CN116365047A discloses a method for preparing a sodium ion battery with sodium supplementation at the negative electrode, which is suitable for sodium ion batteries and comprises the following steps: S01, under gas protection, adding sodium salt to conductive carbon black, ball milling evenly to obtain ball milled material; washing the ball milled material with water and then drying to obtain sodium supplemented carbon black; the mass ratio of the sodium salt to the conductive carbon black is (0.5-3):1; S02, adding the sodium supplemented carbon black in step S01 to the negative electrode material, stirring evenly to obtain the sodium supplemented negative electrode material; S03, preparing a sodium ion battery with sodium supplementation at the negative electrode by using the positive electrode material and the sodium supplemented negative electrode material in step S02.

[0007] CN108878780A discloses a method for replenishing sodium in the negative electrode of a sodium ion battery and a sodium ion battery, comprising: in an inert atmosphere, melting solid metallic sodium at a certain temperature to obtain liquid metallic sodium; uniformly adding the liquid metallic sodium to the surface of a negative electrode sheet so that the liquid metallic sodium penetrates into the gaps between the negative electrode materials of the negative electrode sheet; and drying the negative electrode sheet.

[0008] The sodium replenishment methods for sodium ion batteries disclosed in the prior art have certain defects, such as low stability, generation of harmful gases, poor compatibility, high requirements for the environmental atmosphere during the sodium replenishment process, low safety, complex process flow, formation of sodium dendrites and a high risk of thermal runaway, and formation of anions in the electrolyte, thereby affecting the uniformity and density of the SEI film. Therefore, it is very important to develop a new sodium replenishment method for sodium ion batteries and sodium ion batteries after sodium replenishment. Summary of the invention

[0009] In view of the deficiencies in the prior art, the object of the present invention is to provide a sodium replenishment method for a sodium ion battery and a sodium ion battery after sodium replenishment. The sodium replenishment method provided by the present invention can effectively replenish the sodium ion loss caused by the formation of an SEI film or other side reactions during the first charge. The sodium replenishment method has high stability, no harmful gas is generated during the sodium replenishment process, strong compatibility, low requirements for the environmental atmosphere during the sodium replenishment process, high safety and simple process flow, low risk of dendrite formation and low risk of thermal runaway during the sodium replenishment process, and no anions are formed in the electrolyte, thereby avoiding adverse effects on the uniformity and compactness of the SEI film; therefore, the sodium ion battery after sodium replenishment obtained by the sodium replenishment method has not only high first coulomb efficiency and cycle stability, but also high energy density.

[0010] To achieve this object, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides a method for replenishing sodium in a sodium ion battery, the method comprising:

[0012] (1) coating an initial negative electrode sheet with a sodium supplementing agent slurry to obtain a coated negative electrode sheet; the sodium supplementing agent in the sodium supplementing agent slurry comprises sodium nitride;

[0013] (2) heat treating the coated negative electrode sheet obtained in step (1), and then assembling the battery to obtain a sodium-supplemented sodium ion battery;

[0014] or

[0015] The coated negative electrode sheet obtained in step (1) is assembled into a bare cell to obtain a bare cell, and then the obtained bare cell is thermally formed, and then the sodium-supplemented sodium ion battery is prepared using the thermally formed bare cell.

[0016] The reactions carried out in the sodium supplementation method provided by the present invention are all mild reactions, and no materials with very active chemical properties are used, so the method has higher stability.

[0017] The sodium supplementation method provided by the present invention is to supplement sodium at the negative electrode, and the sodium supplementation agent used is sodium nitride (Na3N). The sodium supplementation agent undergoes thermal decomposition during heat treatment or thermal transformation in step (2), and the thermal decomposition reaction is: 2Na3N→6Na+N2, and the generated gas is nitrogen rather than harmful gas.

[0018] The sodium supplementing agent in the sodium supplementing method provided by the present invention has high compatibility with the negative electrode material, so the sodium supplementing method has strong compatibility.

[0019] In the sodium supplementation method provided by the present invention, the sodium supplementation agent includes sodium nitride, which has lower activity than metallic sodium, a milder thermal decomposition reaction, lower requirements for the environmental atmosphere, and higher safety. Dendrites are not easily formed during sodium supplementation, and the risk of thermal runaway is lower.

[0020] The sodium supplementation method provided by the present invention has fewer steps and is easy to implement, so it also has the advantage of a simple process flow.

[0021] In the sodium supplementation method provided by the present invention, the sodium supplementation agent is decomposed before the bare battery is put into the shell, and the generated gas has been discharged. After the shell is filled with liquid, no anions are formed in the electrolyte, thereby avoiding adverse effects on the uniformity and density of the SEI film.

[0022] In the sodium replenishing method provided by the present invention, the sodium replenishing agent is decomposed before the bare battery is put into the shell, and no inactive solid remains. After the shell is filled with liquid, no loss is caused to the energy density of the sodium ion battery after sodium replenishment.

[0023] The sodium replenishment method provided by the present invention can effectively replenish the sodium ion loss caused by the formation of SEI film or other side reactions during the first charge. The sodium replenishment method has high stability, no harmful gas is generated during the sodium replenishment process, strong compatibility, low requirements for the environmental atmosphere during the sodium replenishment process, high safety and simple process flow, low risk of dendrite formation and low risk of thermal runaway during the sodium replenishment process, and no anion is formed in the electrolyte, thereby avoiding adverse effects on the uniformity and compactness of the SEI film; therefore, the sodium-replenished sodium ion battery obtained by the sodium replenishment method has not only high first coulomb efficiency and cycle stability, but also high energy density.

[0024] Preferably, the mass concentration of the sodium supplementer in the sodium supplementer slurry in step (1) is 0.05-0.5wt%, for example, 0.05wt%, 0.01wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.4wt% or 0.5wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0025] Preferably, the method for preparing the sodium supplement agent slurry in step (1) comprises: mixing the sodium supplement agent with a solvent, and the mixing method comprises stirring.

[0026] Preferably, the boiling point of the solvent in the sodium supplementer slurry is lower than the decomposition temperature of the sodium supplementer, the solvent is soluble in the sodium supplementer, and the solvent does not react with the sodium supplementer.

[0027] Preferably, the solvent comprises any one or a combination of at least two of tetrahydrofuran, methyltetrahydrofuran, acetonitrile or acetone, and typical but non-limiting combinations include a combination of tetrahydrofuran and methyltetrahydrofuran, a combination of methyltetrahydrofuran and acetonitrile, a combination of acetonitrile and acetone, or a combination of tetrahydrofuran, methyltetrahydrofuran and acetonitrile.

[0028] Preferably, the coating in step (1) comprises spraying, and the spraying speed is 0.2-0.8 m / s, for example, 0.2 m / s, 0.3 m / s, 0.4 m / s, 0.5 m / s, 0.6 m / s, 0.7 m / s or 0.8 m / s, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] Preferably, the spraying surface density of the sodium supplement slurry in the spraying is 1.5-100 g / m 2 , for example, it can be 1.5g / m 2 , 3g / m 2 , 5g / m 2 , 10g / m 2 , 15g / m 2 , 20g / m 2 , 30g / m 2 , 40g / m 2 , 50g / m 2 , 60g / m 2 , 70g / m 2 , 80g / m 2 , 90g / m 2 or 100g / m 2 , but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] Preferably, step (1) further comprises drying after the coating, and the drying temperature is 80-100° C. and the drying time is 10-60 min.

[0031] The drying temperature in the present invention is 80-100°C, for example, it can be 80°C, 82°C, 85°C, 88°C, 90°C, 92°C, 95°C, 98°C or 100°C, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 80-90°C.

[0032] The drying time in the present invention is 10 to 60 minutes, for example, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes or 60 minutes, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] Although sodium nitride will decompose during drying in the present invention, the proportion of decomposed sodium nitride is small due to the short drying time.

[0034] Preferably, step (1) further includes die-cutting after the drying.

[0035] Preferably, the initial negative electrode sheet in step (1) comprises a current collector and a negative electrode active material.

[0036] Preferably, the negative electrode active material includes any one or a combination of at least two of a carbon material, a metal element, a non-metal element, an alloy or a metal compound. Typical but non-limiting combinations include a combination of a carbon material and a metal element, a combination of a metal element and a non-metal element, a combination of an alloy and a metal compound, or a combination of a carbon material, a metal element and a non-metal element.

[0037] Preferably, the carbon material comprises any one of hard carbon, soft carbon, activated carbon, expanded graphite, carbon nanotubes, carbon nanowires or graphene, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of hard carbon and soft carbon, a combination of activated carbon and expanded graphite, a combination of carbon nanotubes and carbon nanowires, and a combination of carbon nanowires and graphene.

[0038] Preferably, the metal element includes any one of Sn, Ge or Bi.

[0039] Preferably, the non-metallic element includes P or S.

[0040] Preferably, the alloy comprises any one of Sn alloy, Ge alloy or Bi alloy or a combination of at least two thereof. Typical but non-limiting combinations include a combination of Sn alloy and Ge alloy, a combination of Ge alloy and Bi alloy, or a combination of Sn alloy, Ge alloy and Bi alloy.

[0041] Preferably, the metal compound includes any one of oxide, fluoride or nitride or a combination of at least two thereof, typical but non-limiting combinations include a combination of oxide and fluoride, a combination of fluoride and nitride, or a combination of oxide, fluoride and nitride.

[0042] Preferably, the water content of the initial negative electrode sheet does not exceed 100 ppm, for example, it can be 100 ppm, 99 ppm, 95 ppm, 90 ppm, 85 ppm, 80 ppm, 75 ppm, 70 ppm, 60 ppm, 50 ppm or 20 ppm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] Preferably, the heat treatment in step (2) is performed at a temperature of 90-150° C. and for a time of 30-120 min.

[0044] The temperature of the heat treatment in step (2) of the present invention is 90-150°C, for example, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C or 150°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] The heat treatment time in step (2) of the present invention is 30 to 120 min, for example, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min or 100 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0046] Preferably, the battery assembly in step (2) comprises:

[0047] The coated negative electrode sheet obtained in step (1) after heat treatment is assembled into a bare cell with a separator and a positive electrode sheet, and then the obtained bare cell is sequentially shelled, liquid-filled and battery-formed to obtain a sodium-supplemented sodium ion battery.

[0048] In the present invention, a bare cell is first prepared using the coated negative electrode sheet obtained in step (1), and then the bare cell is thermally formed and then shelled and injected. The sodium supplementation process occurs during the thermal formation of the bare cell. After sodium supplementation, no inactive solid remains, and the energy density of the battery itself is not lost. At the same time, the original sodium ion battery preparation process is not changed. The process is simple, the operation is easy, the cost is low, and it has extremely high practical value.

[0049] Preferably, the bare cell assembly in step (2) includes:

[0050] The coated negative electrode sheet obtained in step (1) is assembled with the separator and the positive electrode sheet into a bare cell.

[0051] Preferably, the temperature of the thermal transformation in step (2) is 80-90° C. and the time is 300-600 min.

[0052] The temperature of the thermal transformation in step (2) of the present invention is 80-90°C, for example, 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C or 90°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0053] The time for thermal conversion in step (2) of the present invention is 300-600 min, for example, 300 min, 350 min, 400 min, 450 min, 500 min or 600 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0054] Preferably, the method for preparing a sodium-supplemented sodium-ion battery using a bare cell after thermal formation in step (2) comprises:

[0055] The bare cell after thermal formation is sequentially shelled, liquid-filled and battery-formed to obtain a sodium-supplemented sodium-ion battery.

[0056] Preferably, both step (1) and step (2) are carried out in an inert atmosphere with an ambient humidity of less than 3%. The ambient humidity may be, for example, 2.9%, 2.7%, 2.5%, 2.3%, 2%, 1.5%, 1%, 0.5% or 0.1%, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0057] As a preferred technical solution of the sodium supplementation method of the present invention, the sodium supplementation method comprises:

[0058] (1) In an inert atmosphere with an ambient humidity of less than 3%, a sodium supplement agent and a solvent are mixed by stirring to obtain a sodium supplement agent slurry with a mass concentration of 0.05-0.5wt%, and then the sodium supplement agent slurry is sprayed on an initial negative electrode sheet with a water content of no more than 100ppm at a speed of 0.2-0.8m / s. The spraying surface density of the sodium supplement agent slurry is 1.5-100g / m 2 , and then drying at 80-100°C for 10-60 minutes and die-cutting to obtain a coated negative electrode sheet;

[0059] The sodium supplement in the sodium supplement slurry includes sodium nitride, the boiling point of the solvent in the sodium supplement slurry is lower than the decomposition temperature of the sodium supplement, the solvent has solubility in the sodium supplement, and the solvent does not react with the sodium supplement;

[0060] (2) in an inert atmosphere with an ambient humidity of less than 3%, the coated negative electrode sheet obtained in step (1) is subjected to a heat treatment at 90-150° C. for 30-120 min, the coated negative electrode sheet after the heat treatment is assembled with a separator and a positive electrode sheet into a bare cell, and the obtained bare cell is then sequentially subjected to shelling, liquid injection and battery formation to obtain a sodium-supplemented sodium ion battery;

[0061] or

[0062] In an inert atmosphere with an ambient humidity of less than 3%, the coated negative electrode sheet obtained in step (1) is assembled with a separator and a positive electrode sheet into a bare cell, and the obtained bare cell is then thermally formed at 80-90° C. for 300-600 min. The thermally formed bare cell is then sequentially shelled, liquid-filled and battery-formed to obtain a sodium-supplemented sodium ion battery.

[0063] In a second aspect, the present invention provides a sodium-supplemented sodium ion battery, wherein the sodium-supplemented sodium ion battery is obtained by the sodium-supplementing method described in the first aspect.

[0064] Preferably, the sodium-supplemented sodium ion battery comprises a sodium-supplemented negative electrode plate, a separator, a positive electrode plate, an electrolyte and a casing.

[0065] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0066] Compared with the prior art, the present invention has the following beneficial effects:

[0067] The sodium replenishment method provided by the present invention can effectively replenish the sodium ion loss caused by the formation of SEI film or other side reactions during the first charge. The sodium replenishment method has high stability, no harmful gas is generated during the sodium replenishment process, strong compatibility, low requirements for the environmental atmosphere during the sodium replenishment process, high safety and simple process flow, low risk of dendrite formation and low risk of thermal runaway during the sodium replenishment process, and no anion is formed in the electrolyte, thereby avoiding adverse effects on the uniformity and compactness of the SEI film; therefore, the sodium-replenished sodium ion battery obtained by the sodium replenishment method has not only high first coulomb efficiency and cycle stability, but also high energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 It is the first cycle charge and discharge curve of the sodium ion battery after sodium supplementation obtained in Example 1 and the sodium ion battery obtained in Comparative Example 1.

[0069] Figure 2 These are the cycle curves of the sodium ion battery after sodium supplementation obtained in Example 1 and the sodium ion battery obtained in Comparative Example 1. DETAILED DESCRIPTION

[0070] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0071] Example 1

[0072] This embodiment provides a sodium replenishment method for a sodium ion battery, the sodium replenishment method comprising:

[0073] (1) In a nitrogen atmosphere with an ambient humidity of 2%, Na3N and tetrahydrofuran were stirred to obtain a sodium supplement slurry with a mass concentration of 0.2wt%, and then the sodium supplement slurry was sprayed on the surface of the HC initial negative electrode sheet with a water content of 80ppm at a speed of 0.5m / s. The spraying surface density of the sodium supplement slurry was 4g / m 2 , and then dried at 80°C for 30 minutes and then die-cut to obtain a coated negative electrode sheet;

[0074] The method for preparing the HC initial negative electrode sheet is:

[0075] The negative electrode active material hard carbon (HC), binder (sodium polyacrylate), conductive agent (conductive carbon black) and deionized water are evenly mixed to form a slurry. The mass ratio of hard carbon, sodium polyacrylate and conductive carbon black is 8:1:1. Then the slurry is coated on the front and back sides of the aluminum foil. After drying, the coating amount on the negative electrode single side is 7 mg / cm 2 , and then cold pressed to obtain the HC initial negative electrode sheet;

[0076] (2) In a nitrogen atmosphere with an ambient humidity of 2%, the coated negative electrode sheet obtained in step (1) is assembled with a separator and a NFPP positive electrode sheet into a bare cell, and the obtained bare cell is thermally formed at 85° C. for 400 min. The thermally formed bare cell is then shelled, liquid-filled and battery-formed in sequence to obtain a sodium-supplemented sodium ion battery;

[0077] The method for preparing the NFPP positive electrode plate is:

[0078] The positive electrode active material composite sodium iron phosphate (NFPP), binder polyvinylidene fluoride (PVDF), conductive agent conductive carbon black (SP) and solvent N-methylpyrrolidone were mixed evenly to form a slurry. The mass ratio of NFPP, PVDF and SP was 8:1:1. The obtained slurry was then coated on the front and back sides of the carbon-coated aluminum foil. After drying, the coating amount on the single side of the positive electrode was 20 mg / cm 2 The water content of the electrode is 80ppm, and then the NFPP positive electrode is obtained after cold pressing and die cutting.

[0079] Example 2

[0080] This embodiment provides a method for replenishing sodium in a sodium ion battery, the method comprising:

[0081] (1) In an inert atmosphere with an ambient humidity of 2.5%, Na3N and methyltetrahydrofuran were stirred to obtain a sodium supplement slurry with a mass concentration of 0.05wt%, and then the sodium supplement slurry was sprayed on an initial negative electrode sheet with a water content of 70ppm at a speed of 0.8m / s. The spraying surface density of the sodium supplement slurry was 16.5g / m 2 , and then dried at 85°C for 30 minutes and then die-cut to obtain a coated negative electrode sheet;

[0082] The method for preparing the HC initial negative electrode sheet is:

[0083] The negative electrode active material hard carbon (HC), binder (sodium polyacrylate), conductive agent (conductive carbon black) and deionized water are evenly mixed to form a slurry. The mass ratio of hard carbon, sodium polyacrylate and conductive carbon black is 8:1:1. Then the slurry is coated on the front and back sides of the aluminum foil. After drying, the coating amount on the negative electrode single side is 7 mg / cm 2 , and then cold pressed to obtain the HC initial negative electrode sheet;

[0084] (2) In an inert atmosphere with an ambient humidity of 2.5%, the coated negative electrode sheet obtained in step (1) is assembled with a separator and a NFPP positive electrode sheet into a bare cell, and the obtained bare cell is thermally formed at 85° C. for 300 min. The thermally formed bare cell is then sequentially shelled, liquid-filled and battery-formed to obtain a sodium-supplemented sodium ion battery;

[0085] The method for preparing the positive electrode sheet is:

[0086] The positive electrode active material composite sodium iron phosphate (NFPP), binder polyvinylidene fluoride (PVDF), conductive agent conductive carbon black (SP) and solvent N-methylpyrrolidone were mixed evenly to form a slurry. The mass ratio of NFPP, PVDF and SP was 8:1:1. The obtained slurry was then coated on the front and back sides of the carbon-coated aluminum foil. After drying, the coating amount on the single side of the positive electrode was 20 mg / cm 2 The water content of the electrode is 90ppm, and then the positive electrode is obtained after cold pressing and die cutting.

[0087] Example 3

[0088] This embodiment provides a method for replenishing sodium in a sodium ion battery, the method comprising:

[0089] (1) In an inert atmosphere with an ambient humidity of 1%, Na3N and acetone were stirred to obtain a sodium supplement slurry with a mass concentration of 0.3wt%, and then the sodium supplement slurry was sprayed on an initial negative electrode sheet with a water content of not less than 90ppm at a speed of 0.2m / s. The spraying surface density of the sodium supplement slurry was 2.8g / m 2 , and then dried at 80°C for 60 minutes and then die-cut to obtain a coated negative electrode sheet;

[0090] The method for preparing the HC initial negative electrode sheet is:

[0091] The negative electrode active material hard carbon (HC), binder (sodium polyacrylate), conductive agent (conductive carbon black) and deionized water are evenly mixed to form a slurry. The mass ratio of hard carbon, sodium polyacrylate and conductive carbon black is 8:1:1. Then the slurry is coated on the front and back sides of the aluminum foil. After drying, the coating amount on the negative electrode single side is 7 mg / cm 2 , and then cold pressed to obtain the HC initial negative electrode sheet;

[0092] (2) In an inert atmosphere with an ambient humidity of 1%, the coated negative electrode sheet obtained in step (1) is assembled with a separator and a NFPP positive electrode sheet into a bare cell, and the obtained bare cell is thermally formed at 85° C. for 400 min. The thermally formed bare cell is then sequentially shelled, liquid-filled and battery-formed to obtain a sodium-supplemented sodium ion battery;

[0093] The method for preparing the NFPP positive electrode plate is:

[0094] The positive electrode active material composite sodium iron phosphate (NFPP), binder polyvinylidene fluoride (PVDF), conductive agent conductive carbon black (SP) and solvent N-methylpyrrolidone were mixed evenly to form a slurry. The mass ratio of NFPP, PVDF and SP was 8:1:1. The obtained slurry was then coated on the front and back sides of the carbon-coated aluminum foil. After drying, the coating amount on the single side of the positive electrode was 20 mg / cm 2 The water content of the electrode is 60ppm, and then the NFPP positive electrode is obtained after cold pressing and die cutting.

[0095] Example 4

[0096] This embodiment provides a method for replenishing sodium in a sodium ion battery. Except that in step (2), the obtained bare cell is thermally formed at 80° C. for 600 min, the rest is the same as that in embodiment 1.

[0097] Example 5

[0098] This embodiment provides a method for replenishing sodium in a sodium ion battery. Except that in step (2), the obtained bare cell is thermally formed at 90° C. for 300 min, the rest is the same as that in embodiment 1.

[0099] Example 6

[0100] This embodiment provides a sodium replenishment method for sodium ion batteries, except that the NFPP positive electrode plate in step (2) is replaced with O3-NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Except for the positive electrode of O2, the rest are the same as those in Example 1;

[0101] Preparation of the O3-NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 The method of O2 positive electrode is:

[0102] The positive electrode active material O3-NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, binder polyvinylidene fluoride (PVDF), conductive agent conductive carbon black (SP) and solvent N-methylpyrrolidone are mixed evenly to form a slurry, O3-NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 The mass ratio of O2, PVDF and SP was 8:1:1. The obtained slurry was then coated on both sides of the carbon-coated aluminum foil. After drying, the coating amount on the positive electrode was 20 mg / cm 2 The water content of the electrode is ≤100ppm, and then O3-NaNi is obtained after cold pressing and die cutting. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 positive electrode.

[0103] Example 7

[0104] This embodiment provides a method for replenishing sodium in a sodium ion battery, which is the same as that in Embodiment 1 except that the NFPP positive electrode sheet in step (2) is replaced by an NVP positive electrode sheet;

[0105] The method for preparing the NVP positive electrode plate is:

[0106] The positive electrode active material sodium vanadium phosphate (NVP), the binder polyvinylidene fluoride (PVDF), the conductive agent conductive carbon black (SP) and the solvent N-methylpyrrolidone were mixed evenly to form a slurry. The mass ratio of NVP, PVDF and SP was 8:1:1. Then the obtained slurry was coated on the front and back sides of the carbon-coated aluminum foil. After drying, the coating amount on the single side of the positive electrode was 10 mg / cm 2 The water content of the electrode is ≤100ppm, and then the NVP positive electrode is obtained after cold pressing and die cutting.

[0107] Example 8

[0108] This embodiment provides a method for replenishing sodium in a sodium ion battery, which is the same as that in Embodiment 1 except that the NFPP positive electrode plate in step (2) is replaced with a Prussian white positive electrode plate;

[0109] The method for preparing the Prussian white positive electrode plate is:

[0110] The positive electrode active material Prussian white, binder polyvinylidene fluoride (PVDF), conductive agent conductive carbon black (SP) and solvent N-methylpyrrolidone were mixed evenly to form a slurry. The mass ratio of NVP, PVDF and SP was 7:1:2. The obtained slurry was then coated on the front and back sides of the carbon-coated aluminum foil. After drying, the coating amount on one side of the positive electrode was 10 mg / cm 2 The water content of the electrode is ≤100ppm, and then the Prussian white positive electrode is obtained after cold pressing and die cutting.

[0111] Example 9

[0112] This embodiment provides a method for replenishing sodium in a sodium ion battery, which is the same as that in Embodiment 1 except that the NFPP positive electrode plate in step (2) is replaced with a sodium iron sulfate positive electrode plate;

[0113] The method for preparing the sodium iron sulfate positive electrode plate is:

[0114] The positive electrode active material sodium iron sulfate, binder polyvinylidene fluoride (PVDF), conductive agent conductive carbon black (SP) and solvent N-methylpyrrolidone were mixed evenly to form a slurry. The mass ratio of NVP, PVDF and SP was 7:1:2. Then the obtained slurry was coated on the front and back sides of the carbon-coated aluminum foil. After drying, the coating amount on one side of the positive electrode was 12 mg / cm 2 The water content of the electrode is ≤100ppm, and then the sodium iron sulfate positive electrode is obtained after cold pressing and die cutting.

[0115] Example 10

[0116] This embodiment provides a method for replenishing sodium in a sodium ion battery, which is the same as that in Embodiment 1 except that the HC initial negative electrode sheet in step (1) is replaced with a pure aluminum initial negative electrode sheet;

[0117] The pure aluminum initial negative electrode sheet is prepared by drying aluminum foil in the prior art.

[0118] Embodiment 11

[0119] This embodiment provides a method for replenishing sodium in a sodium ion battery, which is the same as that in Embodiment 1 except that the HC initial negative electrode sheet in step (1) is replaced by a carbon-coated aluminum foil initial negative electrode sheet;

[0120] The carbon-coated aluminum foil initial negative electrode sheet is prepared by drying the carbon-coated aluminum foil in the prior art.

[0121] Example 12

[0122] This embodiment provides a method for replenishing sodium in a sodium ion battery, which is the same as that in Embodiment 1 except that the HC initial negative electrode sheet in step (1) is replaced by an AC initial negative electrode sheet;

[0123] The method for preparing the AC initial negative electrode sheet is:

[0124] The negative electrode active material activated carbon (AC), thickener (carboxymethyl cellulose), binder (styrene butadiene rubber) and conductive agent (conductive carbon black) were mixed evenly with deionized water to form a slurry. The mass ratio of activated carbon, carboxymethyl cellulose, styrene butadiene rubber and conductive carbon black was 8:0.2:0.8:1. The slurry was then coated on both sides of the aluminum foil. After drying, the coating amount on each side was 2 mg / cm 2 , the AC initial negative electrode sheet was obtained.

[0125] Embodiment 13

[0126] This embodiment provides a method for replenishing sodium in a sodium ion battery, which is the same as that in Embodiment 1 except that the HC initial negative electrode sheet in step (1) is replaced with a foam nickel initial negative electrode sheet;

[0127] The foamed nickel initial negative electrode sheet is prepared by drying the foamed nickel in the prior art.

[0128] Embodiment 14

[0129] This embodiment provides a method for replenishing sodium in a sodium ion battery, which is the same as that in Embodiment 1 except that the HC initial negative electrode sheet in step (1) is replaced by a Sn initial negative electrode sheet;

[0130] The method for preparing the Sn initial negative electrode sheet is:

[0131] The negative electrode active material tin powder (Sn), thickener (carboxymethyl cellulose), binder (styrene butadiene rubber), conductive agent (conductive carbon black) and deionized water are mixed evenly to form a slurry. The mass ratio of tin powder, carboxymethyl cellulose, styrene butadiene rubber and conductive carbon black is 7:0.5:1.5:1. Then the obtained slurry is coated on the front and back sides of the aluminum foil. After drying, the coating amount on each side is 2 mg / cm 2 , and the Sn electrode is obtained.

[0132] Embodiment 15

[0133] This embodiment provides a method for replenishing sodium in a sodium ion battery. Except that the mass concentration of the sodium replenisher in the sodium replenisher slurry in step (1) is 0.01 wt %, and the mass of the sodium replenisher Na3N coated on the surface of the initial negative electrode sheet is kept constant, the rest is the same as that in embodiment 1.

[0134] Example 16

[0135] This embodiment provides a method for replenishing sodium in a sodium ion battery. Except that the mass concentration of the sodium replenisher in the sodium replenisher slurry in step (1) is 0.8 wt %, and the mass of the sodium replenisher Na3N coated on the surface of the initial negative electrode sheet is kept constant, the rest is the same as that in embodiment 1.

[0136] Embodiment 17

[0137] This embodiment provides a method for replenishing sodium in a sodium ion battery. Except that the spraying speed of the sodium replenisher slurry in step (1) is 0.1 m / s, the rest is the same as that in embodiment 1.

[0138] Embodiment 18

[0139] This embodiment provides a method for replenishing sodium in a sodium ion battery. Except that the spraying speed of the sodium replenisher slurry in step (1) is 1 m / s, the rest is the same as that in embodiment 1.

[0140] Embodiment 19

[0141] This embodiment provides a method for replenishing sodium in a sodium ion battery. The method is the same as that in Embodiment 1 except that step (2) is replaced by:

[0142] In an inert atmosphere with an ambient humidity of 2.5%, the coated negative electrode sheet obtained in step (1) is heat treated at 120° C. for 70 min, and then the heat-treated coated negative electrode sheet is assembled with a separator and a positive electrode sheet into a bare cell. The obtained bare cell is then sequentially shelled, liquid-filled and battery-formed to obtain a sodium-supplemented sodium ion battery.

[0143] Embodiment 20

[0144] This embodiment provides a method for replenishing sodium in a sodium ion battery, which is the same as that in Embodiment 21 except that the temperature at which the negative electrode sheet is heat treated after coating in step (2) is 70° C.

[0145] Embodiment 21

[0146] This embodiment provides a method for replenishing sodium in a sodium ion battery, which is the same as that in Embodiment 21 except that the temperature of heat treatment of the coated negative electrode sheet in step (2) is 200°C.

[0147] Embodiment 22

[0148] This embodiment provides a method for replenishing sodium in a sodium ion battery. Except that the temperature of thermal formation of the bare cell in step (2) is 70° C., the rest is the same as that in embodiment 1.

[0149] Embodiment 23

[0150] This embodiment provides a method for replenishing sodium in a sodium ion battery. Except that the temperature at which the bare battery is thermally formed in step (2) is 100° C., the rest is the same as that in embodiment 1.

[0151] Comparative Example 1

[0152] This comparative example provides a method for preparing a sodium ion battery, which is the same as Example 1 except that step (1) is omitted, that is, the coated negative electrode sheet in step (2) is directly replaced by the HC initial negative electrode sheet.

[0153] Comparative Example 2

[0154] This comparative example provides a method for preparing a sodium ion battery, which is the same as Example 6 except that step (1) is omitted, that is, the coated negative electrode sheet in step (2) is directly replaced by the HC initial negative electrode sheet.

[0155] Comparative Example 3

[0156] This comparative example provides a method for preparing a sodium ion battery, which is the same as Example 7 except that step (1) is omitted, that is, the coated negative electrode sheet in step (2) is directly replaced by the HC initial negative electrode sheet.

[0157] Comparative Example 4

[0158] This comparative example provides a method for preparing a sodium ion battery, which is the same as Example 8 except that step (1) is omitted, that is, the coated negative electrode sheet in step (2) is directly replaced by the HC initial negative electrode sheet.

[0159] Comparative Example 5

[0160] This comparative example provides a method for preparing a sodium ion battery, which is the same as Example 9 except that step (1) is omitted, that is, the coated negative electrode sheet in step (2) is directly replaced by the HC initial negative electrode sheet.

[0161] Comparative Example 6

[0162] This comparative example provides a method for preparing a sodium ion battery, which is the same as Example 10 except that step (1) is omitted, that is, the coated negative electrode sheet in step (2) is directly replaced by a pure aluminum initial negative electrode sheet.

[0163] Comparative Example 7

[0164] This comparative example provides a method for preparing a sodium ion battery, which is the same as Example 11 except that step (1) is omitted, that is, the carbon-coated aluminum foil initial negative electrode sheet is directly used to replace the coated negative electrode sheet in step (2).

[0165] Comparative Example 8

[0166] This comparative example provides a method for preparing a sodium ion battery, which is the same as Example 12 except that step (1) is omitted, that is, the coated negative electrode sheet in step (2) is directly replaced by the AC initial negative electrode sheet.

[0167] Comparative Example 9

[0168] This comparative example provides a method for preparing a sodium ion battery, which is the same as Example 13 except that step (1) is omitted, that is, the coated negative electrode sheet in step (2) is directly replaced by the initial negative electrode sheet of nickel foam.

[0169] Comparative Example 10

[0170] This comparative example provides a method for preparing a sodium ion battery, which is the same as Example 14 except that step (1) is omitted, that is, the coated negative electrode sheet in step (2) is directly replaced by a Sn initial negative electrode sheet.

[0171] The sodium-supplemented sodium ion battery provided in the above embodiment and the sodium ion battery provided in the comparative example were subjected to an initial efficiency test, a cycle life test and an energy density test.

[0172] The method of the first efficiency test is: let the battery stand for 30 minutes in a 25°C environment; then charge it to 3.5V at a constant current of 0.1C to obtain the charging capacity (AGCO), and then charge it at a constant voltage at 3.5V until the current drops to 0.05C to obtain the constant voltage capacity (ICCO); let it stand for 30 minutes, and then discharge it to 1.5V at a constant current of 0.1C to obtain the first discharge capacity (DO); then calculate the first coulomb efficiency of the battery, the calculation formula is: first coulomb efficiency = DO / (ICCO + AGCO), and the first coulomb efficiency is shown in Table 1; wherein, the first cycle charge and discharge curves of the sodium ion battery after sodium supplementation obtained in Example 1 and the sodium ion battery obtained in Comparative Example 1 are as shown in Figure 1 shown.

[0173] The method for cycle life test is: the battery is cycled at 1C / 1C until the battery capacity is 80% of the initial capacity. At this time, the number of battery cycles is the cycle life. The obtained cycle number is shown in Table 1; wherein, the cycle curves of the sodium ion battery after sodium supplementation obtained in Example 1 and the sodium ion battery obtained in Comparative Example 1 are shown in Figure 2 shown.

[0174] The energy density test method is: energy density of sodium battery = battery discharge energy / battery weight; the discharge energy test method is: charge to 3.5V at 0.2C constant current and constant voltage, then discharge to 1.5V at 0.2C, cycle for 3 weeks, obtain the discharge energy, and calculate the energy density as shown in Table 1.

[0175] Table 1

[0176]

[0177]

[0178] From Table 1, we can get:

[0179] (1) The sodium-supplemented sodium ion battery prepared by the sodium-supplementing method provided in Examples 1 to 5 of the present invention has a large first coulombic efficiency, excellent cycle stability and high energy density.

[0180] (2) By comparing Example 1 with Examples 6 to 9, it can be seen that the positive electrode sheet in step (2) of the sodium supplementation method of the present invention will affect the performance of the sodium ion battery after sodium supplementation. The positive electrode sheet is a NFPP positive electrode sheet, O3-NaNi 1 / 3 Fe 1 / 3 Mn 1 / When the 3O2 positive electrode sheet and the NVP positive electrode sheet are used, the sodium ion battery has a longer cycle life after sodium supplementation.

[0181] (3) By comparing Example 1 with Examples 10 to 14, it can be seen that the initial negative electrode sheet used in step (1) of the sodium supplementation method of the present invention will affect the performance of the sodium ion battery after sodium supplementation. When the initial negative electrode sheet is an HC initial negative electrode, a carbon-coated aluminum foil initial negative electrode sheet, an AC initial negative electrode sheet, a foam nickel initial negative electrode sheet, and a Sn initial negative electrode sheet, the sodium ion battery after sodium supplementation exhibits a larger first coulombic efficiency and excellent cycle stability.

[0182] (4) By comparing Example 1 with Examples 15 and 16, it can be seen that the mass concentration of the sodium supplementer in the sodium supplementer slurry in step (1) of the present invention affects the performance of the sodium ion battery after sodium supplementation; when the mass concentration of the sodium supplementer is 0.05~0.5wt%, the sodium ion battery after sodium supplementation has a better cycle life. This is because a moderate concentration of the sodium supplementer is conducive to its uniform distribution in the initial negative electrode, thereby promoting uniform sodium supplementation inside the negative electrode and improving the battery cycle life.

[0183] (5) By comparing Example 1 with Examples 17 and 18, it can be seen that the spraying speed of the sodium supplement slurry in step (1) of the present invention affects the performance of the sodium ion battery after sodium supplementation; when the spraying speed of the sodium supplement is 0.2~0.8m / s, the sodium ion battery after sodium supplementation has a better cycle life. This is because when the spraying speed is too fast, the sodium supplement slurry cannot fully penetrate into the interior of the material, resulting in the inability to supplement sodium at the bottom of the initial negative electrode; when the spraying speed is too slow, the efficiency is low, which will lead to local accumulation of the sodium supplement.

[0184] (6) By comparing Example 1 with Example 19, it can be seen that in step (2) of the present invention, the technical solution of "assembling the coated negative electrode sheet obtained in step (1) into a bare cell to obtain a bare cell, then thermally forming the obtained bare cell, and then preparing a sodium-supplemented sodium ion battery with the thermally formed bare cell" is superior to the technical solution of "heat-treating the coated negative electrode sheet obtained in step (1) and then assembling the cell to obtain a sodium-supplemented sodium ion battery". This is because in the present invention, a bare cell is first prepared with the coated negative electrode sheet obtained in step (1), and the bare cell is thermally formed before shelling and liquid injection. The sodium supplementation process occurs during the thermal formation process of the bare cell. After sodium supplementation, no inactive solid residues remain, and the energy density of the battery itself will not be lost. At the same time, the original sodium ion battery preparation process is not changed, and the process is simple, easy to operate, low cost, and extremely high practical value.

[0185] (7) By comparing Example 1 with Examples 20 and 21, it can be seen that when the technical solution of step (2) is "heat-treating the coated negative electrode sheet obtained in step (1) and then assembling the battery to obtain a sodium-supplemented sodium ion battery", the heat treatment temperature will affect the performance of the sodium-supplemented sodium ion battery; when the heat treatment temperature is 90~150℃, the sodium-supplemented sodium ion battery has better coulombic efficiency and cycle life. This is because when the heat treatment temperature is too low, the sodium supplement agent is not completely decomposed, the expected sodium supplement effect cannot be achieved, and the coulombic efficiency is reduced; when the heat treatment temperature is too high, it will cause the decomposition of the binder in the initial negative electrode, resulting in the weakening of the bonding force of the electrode itself, thereby shortening the cycle life.

[0186] (8) By comparing Example 1 with Examples 22 and 23, it can be seen that when the technical solution of step (2) is "assembling the coated negative electrode sheet obtained in step (1) into a bare cell to obtain a bare cell, then thermally forming the obtained bare cell, and then preparing a sodium-supplemented sodium ion battery with the bare cell after thermal formation", the thermal formation temperature will affect the performance of the sodium-supplemented sodium ion battery; when the thermal formation temperature is 80~90℃, the sodium-supplemented sodium ion battery has better coulombic efficiency and cycle life. This is because when the thermal formation temperature is too low, the sodium supplement agent is not completely decomposed and the expected sodium supplement effect cannot be achieved; when the thermal formation temperature is too high, it will cause thermal shrinkage of the diaphragm, thereby shortening the cycle life and battery safety.

[0187] (9) By comparing Example 1, Examples 6 to 14 with Comparative Examples 1 to 10, it can be seen that the first coulombic efficiency and cycle life of the sodium-supplemented sodium ion battery containing the sodium-supplemented negative electrode are better than the first coulombic efficiency and cycle life of the corresponding comparative example; the sodium supplementation method provided by the present invention can effectively supplement the sodium ion loss caused by the formation of SEI film or other side reactions during the first charge, the sodium supplementation method has high stability, no harmful gas is generated during the sodium supplementation process, strong compatibility, low requirements for the environmental atmosphere during the sodium supplementation process, high safety and simple process flow, low risk of dendrite formation and thermal runaway during the sodium supplementation process, and no anions are formed in the electrolyte, thereby avoiding adverse effects on the uniformity and density of the SEI film; therefore, the sodium supplementation method provided by the present invention can effectively improve the first coulombic efficiency and cycle life of the sodium ion battery.

[0188] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for replenishing sodium in a sodium ion battery, characterized in that: The sodium supplementation method comprises: (1) coating an initial negative electrode sheet with a sodium supplementing agent slurry to obtain a coated negative electrode sheet; the sodium supplementing agent in the sodium supplementing agent slurry comprises sodium nitride; (2) heat treating the coated negative electrode sheet obtained in step (1) at 90-150° C. for 30-120 min, and then assembling the battery to obtain a sodium-supplemented sodium ion battery; The battery assembly comprises: The coated negative electrode sheet obtained in step (1) after heat treatment is assembled with the separator and the positive electrode sheet into a bare cell, and then the bare cell is sequentially shelled, liquid-filled and battery-formed to obtain a sodium-supplemented sodium ion battery; or Assembling the coated negative electrode sheet obtained in step (1) into a bare cell to obtain a bare cell, and then thermally forming the obtained bare cell at 80-90° C. for 300-600 min, and then preparing a sodium-supplemented sodium ion battery using the thermally formed bare cell; The method for preparing a sodium-supplemented sodium ion battery using a bare cell after thermal formation comprises: The bare cell after thermal formation is sequentially shelled, liquid-filled and battery-formed to obtain a sodium-supplemented sodium-ion battery.

2. The sodium supplementation method according to claim 1, characterized in that The mass concentration of the sodium supplementer in the sodium supplementer slurry in step (1) is 0.05-0.5wt%.

3. The sodium supplementation method according to claim 1, characterized in that The boiling point of the solvent in the sodium supplement agent slurry is lower than the decomposition temperature of the sodium supplement agent, the solvent is soluble in the sodium supplement agent, and the solvent does not react with the sodium supplement agent.

4. The sodium supplementation method according to claim 1, characterized in that The coating in step (1) includes spraying, and the spraying speed is 0.2~0.8m / s.

5. The sodium supplementation method according to claim 4, characterized in that: The spraying surface density of the sodium supplement slurry in the spraying is 1.5-100 g / m 2 .

6. The sodium supplementation method according to claim 1, characterized in that: After the coating in step (1), the coating also includes drying, and the drying temperature is 80-100° C. and the drying time is 10-60 minutes.

7. The method for supplementing sodium according to any one of claims 1 to 6, characterized in that: The sodium supplementation method comprises: (1) In an inert atmosphere with an ambient humidity of less than 3%, a sodium supplement agent and a solvent are mixed by stirring to obtain a sodium supplement agent slurry with a mass concentration of 0.05-0.5wt%, and then the sodium supplement agent slurry is sprayed on an initial negative electrode sheet with a water content of no more than 100ppm at a speed of 0.2-0.8m / s. The spraying surface density of the sodium supplement agent slurry is 1.5-100g / m 2 , and then drying at 80-100°C for 10-60 minutes and die-cutting to obtain a coated negative electrode sheet; The sodium supplement in the sodium supplement slurry includes sodium nitride, the boiling point of the solvent in the sodium supplement slurry is lower than the decomposition temperature of the sodium supplement, the solvent has solubility in the sodium supplement, and the solvent does not react with the sodium supplement; (2) in an inert atmosphere with an ambient humidity of less than 3%, the coated negative electrode sheet obtained in step (1) is subjected to a heat treatment at 90-150° C. for 30-120 min, the coated negative electrode sheet after the heat treatment is assembled with a separator and a positive electrode sheet into a bare cell, and the obtained bare cell is then sequentially subjected to shelling, liquid injection and battery formation to obtain a sodium-supplemented sodium ion battery; or In an inert atmosphere with an ambient humidity of less than 3%, the coated negative electrode sheet obtained in step (1) is assembled with a separator and a positive electrode sheet into a bare cell, and the obtained bare cell is then thermally formed at 80-90° C. for 300-600 min. The thermally formed bare cell is then sequentially shelled, liquid-filled and battery-formed to obtain a sodium-supplemented sodium ion battery.

8. A sodium-supplemented sodium ion battery, characterized in that: The sodium-supplemented sodium ion battery is obtained by the sodium-supplementing method according to any one of claims 1 to 7.

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