Sodium-ion battery current collector, preparation method thereof and negative-electrode-free sodium-ion battery

Abstract

The invention relates to the field of sodium-ion batteries, in particular to a sodium-ion battery current collector, a preparation method thereof and a negative-electrode-free sodium-ion battery. According to the preparation method, hydroxyl fibrosis H-Ti3C2 is prepared by utilizing a high-concentration alkaline solution and a relatively long alkalization time, and then abundant NaF is formed on the surface of hydroxyl fibrosis Mxene through a simple one-step reaction by utilizing the characteristic that hydroxyl fibrosis Mxene has abundant sodium-philic functional groups such as oxygen, fluorine and the like; and finally, a layer of tough and stable PVP / H-MXene / NaF composite SEI fiber membrane is constructed on the surface of the copper foil through an electrostatic spinning method, the presetting of the high-stability artificial SEI membrane can promote the uniform deposition of sodium ions, the growth of negative electrode sodium dendrites is inhibited, and the cycling stability of the battery is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sodium ion batteries, in particular to a sodium ion battery current collector and a preparation method thereof and a negative electrode-free sodium ion battery. BACKGROUND

[0002] Sodium ion batteries have great advantages in resources, cost, safety, power performance, low temperature performance, etc., and have broad application prospects. However, the current sodium ion battery has a low energy density, usually 140-160 Wh·kg -1 , which is only 50%-80% of that of commercial lithium ion batteries. In order to open up a broader application space, developing high specific energy sodium batteries is the focus of the academic and industrial circles. The mainstream hard carbon material is faced with problems such as high cost, low first coulombic efficiency and kinetic performance, and cell swelling, and the negative electrode is considered to be the bottleneck restricting the development of the sodium battery industry. Sodium metal negative electrode can construct high specific energy sodium battery, but the hardness of metal sodium is low, which is difficult to be rolled or cut into different shapes such as plates, foils and rods, and there is still no commercial sodium foil on the market. At the same time, metal sodium has extremely high chemical reactivity, which is easy to react with electrolyte, resulting in unnecessary electrolyte consumption and the formation of irreversible passivation layer, thereby affecting the coulombic efficiency (CE).

[0003] Recently, negative electrode-free sodium ion batteries (AFSBs) have received extensive attention, which directly uses a blank current collector or a modified current collector as the negative electrode, thereby improving the energy density. Compared with traditional sodium ion batteries, AFSBs can avoid the negative electrode manufacturing process including synthesis, mixing, coating and drying, eliminate the related cost of negative electrode manufacturing and integration, and increase the safety of the battery in the manufacturing process. However, AFSBs show poor cycle stability, which limits their practical application. One of the reasons for the failure of AFSBs is the low coulombic efficiency (CE), which is caused by the continuous interfacial interaction between the electrolyte and the deposited sodium metal. In order to circumvent this problem, a solid electrolyte interface (SEI) consisting of a dense film stable to sodium metal will provide high ionic conductivity and electronic insulation, which helps to reduce the negative interfacial reaction. However, the natural SEI material containing disordered and chemically heterogeneous solid by-products usually shows low ionic conductivity and poor fracture toughness, which leads to the penetration of electrolyte through the SEI grain boundaries and the continuous depletion of sodium ions on the anode surface. SUMMARY

[0004] The purpose of the present application is to overcome the deficiencies in the prior art, and to provide a sodium ion battery current collector capable of promoting sodium dendrite-free deposition, a preparation method thereof and a negative electrode-free sodium ion battery.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is:

[0006] The first aspect of this invention is to provide a method for preparing a sodium-ion battery current collector, comprising the steps of:

[0007] S1. Ti3AlC2 is added to HF solution for etching. After etching, it is centrifuged, washed and dried in sequence to obtain Ti3C2 powder.

[0008] S2. Add Ti3C2 powder to KOH solution and react in an inert gas atmosphere. After the reaction is completed, wash and dry the powder in sequence to obtain H-Ti3C2.

[0009] S3. Add PVP and H-Ti3C2 to the sodium salt solution and stir magnetically until homogeneous to obtain the precursor solution.

[0010] S4. Using copper foil as the receiving device and precursor solution as the spinning material, spinning is carried out. After spinning, drying and cooling treatments are performed in sequence to obtain a sodium-ion battery current collector with PVP / H-MXene / NaF SEI film loaded on the surface.

[0011] Preferably, in step S1, the etching temperature is 25-30℃ and the time is 24-36h.

[0012] Preferably, in step S1, the centrifugation process includes: centrifuging at 7000-8000 rpm for 10-15 min.

[0013] Preferably, in step S2, the inert gas includes nitrogen or argon.

[0014] Preferably, in step S2, the reaction temperature is 25-30℃ and the time is 100-110h.

[0015] Preferably, in step S3, the sodium salt in the sodium salt solution includes at least one of sodium nitrate, sodium sulfate, sodium chloride, and sodium carbonate.

[0016] Preferably, in step S4, spinning includes: extracting the precursor solution using a disposable syringe, fixing it on a solution injection propulsion device, setting the liquid flow rate to 0.2 mL / h, connecting the flat-mouth needle of the disposable syringe to the positive terminal of a DC power supply, connecting the copper foil of the receiving device to the negative terminal of the DC power supply, adjusting the voltage of the working high-voltage power supply to 15-50 kV, setting the distance between the flat-mouth needle and the copper foil of the receiving device to 8-20 cm, setting the collection speed to 100 rpm, and spinning under a relative temperature of 25°C.

[0017] A second aspect of the present invention is to provide a sodium-ion battery current collector prepared by the above-described preparation method.

[0018] A third aspect of the present invention is to provide a negative electrode-free sodium-ion battery, comprising a positive electrode, a current collector, and an electrolyte; wherein the current collector is a sodium-ion battery current collector prepared by the above-described preparation method.

[0019] Preferably, the positive electrode is NaxTMO2; the electrolyte is NaTFSI / EC+DEC.

[0020] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0021] This invention utilizes a high-concentration alkaline solution and a long alkali treatment time to prepare hydroxyl-fiberized H-Ti3C2. Then, taking advantage of the abundant sodium-loving functional groups such as oxygen and fluorine in hydroxyl-fiberized MXene, a rich NaF is formed on the surface of hydroxyl-fiberized MXene through a simple one-step reaction. Finally, a tough and stable PVP / H-MXene / NaF composite SEI fiber membrane is constructed on the surface of copper foil by electrospinning. The pre-placement of the highly stable artificial SEI membrane can promote the uniform deposition of sodium ions, inhibit the growth of sodium dendrites on the negative electrode, and significantly improve the cycle stability of the battery. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0024] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0025] Example

[0026] This embodiment provides a method for preparing a sodium-ion battery current collector and a negative electrode-free sodium-ion battery, the steps of which include:

[0027] 2g of Ti3AlC2 was slowly added to HF solution (40%, 60mL) over 10 minutes, and gently stirred at 30℃ for 24 hours to obtain etched Ti3C2 powder; 0.5g of Ti3C2 powder was added to KOH solution (6mol·L⁻¹) -1 60 mL), continuously shaken at 25 °C for 108 h in N2 atmosphere, washed multiple times and the product was collected, and dried in vacuum at 55 °C for 12 h to obtain H-Ti3C2.

[0028] In sodium nitrate solution (2 mg·L) -1 Add 1g of PVP powder and 4.5mg of H-Ti3C2 to 150mL of water, and stir with a magnetic stirrer for 24h until a black precursor solution is obtained. Draw the precursor solution into a disposable syringe, then fix it to the solution injection device, set the liquid flow rate to 0.2mL / h, connect the flat needle of the syringe to the positive terminal of the DC power supply, connect the copper foil of the receiving device to the negative terminal of the DC power supply, adjust the voltage of the working high voltage power supply to 15kV, set the distance between the needle and the copper foil of the receiving device to 15cm, set the collection speed to 100rpm, and spin at a relative temperature of 25℃. Place the spun copper foil sample in a vacuum drying oven at 150℃ for 10min, and then cool it to room temperature in a vacuum environment to obtain a sodium-ion battery current collector with a surface-loaded PVP / H-MXene / NaF SEI film.

[0029] Pre-deposit 1.0 mAh / cm² on a sodium-ion battery current collector loaded with a PVP / H-MXene / NaF SEI film. -2 Na then combined with Na x The TMO2 cathode is assembled into a coin cell, using NaTFSI / EC+DEC as the electrolyte, with an electrolyte-to-solvent volume ratio of EC:DEC = 1:1, and a ceramic separator is used to assemble the 2032 type coin cell.

[0030] Comparative Example 1

[0031] Pre-deposit 1.0 mAh / cm² on blank copper foil. -2 Na then combined with Na x TMO2 cathodes were assembled into coin cells. NaTFSI / EC+DEC was used as the electrolyte, with an electrolyte-to-solvent volume ratio of EC:DEC = 1:1. A ceramic separator was used to assemble the 2032-type coin cells.

[0032] Detection Examples

[0033] The cycle performance of the battery was tested at 0.5C and 1C currents, and the results are shown in Table 1.

[0034] Table 1

[0035]

[0036] The battery in Example 1 exhibited 120.2 mAh / g at 0.5C. -1 The initial capacity is greater than that of Comparative Example 1, which has a capacity of 95.9 mAh / g. -1After 30 cycles, the capacity retention rate of Example 1 was 80.7%, while that of Comparative Example 1 was only 58.0%. Furthermore, the initial capacity of the battery in Example 1 at 1.0C was 118.9 mAh / g. -1 After 30 cycles, the capacity retention rate of Example 1 was 78.9%, while that of Comparative Example 1 was only 18%. This shows that the battery of Example 1 maintains a high coulombic efficiency (≥96%) at both 0.5C and 1.0C. In Comparative Example 1, the negative electrode consists only of a current collector (copper foil). During charging, sodium ions are directly deposited on the current collector to form metallic sodium, resulting in a high sodium nucleation barrier. This requires overcoming a large nucleation overpotential, leading to non-uniform sodium deposition. This non-uniform deposition also increases the risk of sodium dendrite formation.

[0037] In summary, the sodium-ion battery current collector prepared in this invention significantly improves the utilization efficiency of the active material and optimizes the Na deposition process due to the promotion of the 3D ion-conducting composite network on the current collector surface, while also reducing the formation of "dead Na". Furthermore, H-Ti3C2 and NaF promote the formation of a stable and durable SEI layer at the electrode / electrolyte interface, inhibit the growth of dendritic Na, and extend the cycle life of the sodium-poor battery.

[0038] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. A method for preparing a sodium-ion battery current collector, characterized in that the steps include... include: S1. Ti3AlC2 is added to HF solution for etching. After etching, it is centrifuged, washed and dried in sequence to obtain Ti3C2 powder. S2. Add Ti3C2 powder to KOH solution and react in an inert gas atmosphere. After the reaction is completed, wash and dry the powder in sequence to obtain H-Ti3C2. S3. Add PVP and H-Ti3C2 to the sodium salt solution and stir magnetically until homogeneous to obtain the precursor solution. S4. Using copper foil as the receiving device and precursor solution as the spinning material, spinning is carried out. After spinning, drying and cooling treatments are performed in sequence to obtain a sodium-ion battery current collector with PVP / H-MXene / NaF SEI film loaded on the surface.

2. The preparation method according to claim 1, characterized in that, In step S1, the etching temperature is 25-30℃ and the time is 24-36h.

3. The preparation method according to claim 1, characterized in that, In step S1, the centrifugation process includes centrifuging at 7000-8000 rpm for 10-15 minutes.

4. The preparation method according to claim 1, characterized in that, In step S2, the inert gas includes nitrogen or argon.

5. The preparation method according to claim 1, characterized in that, In step S2, the reaction temperature is 25-30℃ and the time is 100-110h.

6. The preparation method according to claim 1, characterized in that, In step S3, the sodium salt in the sodium salt solution includes at least one of sodium nitrate, sodium sulfate, sodium chloride, and sodium carbonate.

7. The preparation method according to claim 1, characterized in that, In step S4, spinning includes: extracting the precursor solution using a disposable syringe, fixing it on the solution injection propulsion device, setting the liquid flow rate to 0.2 mL / h, connecting the flat-tipped needle of the disposable syringe to the positive terminal of the DC power supply, connecting the copper foil of the receiving device to the negative terminal of the DC power supply, adjusting the voltage of the working high-voltage power supply to 15-50 kV, setting the distance between the flat-tipped needle and the copper foil of the receiving device to 8-20 cm, setting the collection speed to 100 rpm, and spinning under a relative humidity of 25°C.

8. A sodium-ion battery current collector prepared by the preparation method according to any one of claims 1-7.

9. A sodium-ion battery without a negative electrode, characterized in that, It includes a positive electrode, a current collector, and an electrolyte; wherein the current collector is a sodium-ion battery current collector prepared by the preparation method according to any one of claims 1-7.

10. The negative electrode-free sodium-ion battery according to claim 9, characterized in that, The positive electrode is NaxTMO2; the electrolyte is NaTFSI / EC+DEC.

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