Negative electrode current collector coating of non-negative electrode sodium metal battery and preparation method of negative electrode current collector coating

Abstract

The invention discloses a negative-electrode-free sodium metal battery negative electrode current collector coating and a preparation method thereof, relates to a sodium battery negative electrode and a preparation method thereof, and aims to solve the technical problems of high nucleation overpotential and poor stable circularity of an existing negative-electrode-free sodium battery. The negative current collector coating of the negative-electrode-free sodium metal battery is prepared from an active substance, a conductive carbon material and an adhesive, wherein the active substance is bismuth fluoride, ferric fluoride, tin fluoride, bismuth oxide, antimony oxide, bismuth phosphate, antimony phosphate, bismuth acetate, lead acetate or antimony acetate. The active substance, the conductive carbon material and the adhesive are prepared into slurry, and the slurry is coated on the fluid and then dried. The half cell assembled by using the negative electrode current collector and sodium realizes the average coulombic efficiency of more than 99.5%, and realizes stable circulation for 300 circles in a sodium battery without a negative electrode. The method can be used in the field of sodium batteries or sodium metal batteries.

Description

Technical Field

[0001] This invention belongs to the technical field of sodium battery anode design and current collector modification preparation, specifically relating to a current collector coating for a non-anode sodium metal battery and its preparation method. Background Technology

[0002] The sustainability of lithium-ion batteries is limited by lithium resources, while sodium-ion batteries, benefiting from the wide availability and low cost of sodium resources, are expected to become an alternative to lithium-ion batteries in short-range transportation and energy storage. However, the current low energy density and high cost of hard carbon in sodium-ion batteries limit their application. Electrodeless sodium batteries hold promise for breakthroughs in energy density / cost, but their architecture introduces fundamental interface challenges. When sodium is plated onto the current collector, the high nucleation overpotential leads to small and irregular nuclei, followed by moss-like growth and porous sodium metal deposition. This irregular growth exacerbates secondary side reactions, causing continuous cracking and remodeling of the solid electrolyte interface, resulting in rapid capacity loss. Summary of the Invention

[0003] The present invention aims to solve the technical problems of high nucleation overpotential and poor stable cycle performance of existing non-anode sodium batteries, and provides a non-anode sodium metal battery anode current collector coating and its preparation method.

[0004] The negative electrode current collector coating of the sodium metal battery without negative electrode of the present invention is prepared from active material, conductive carbon material and binder; wherein the active material is metal fluoride, oxide, phosphate or acetate.

[0005] The metal fluoride is bismuth fluoride, iron fluoride, or tin fluoride;

[0006] The oxide is bismuth oxide or antimony oxide;

[0007] The phosphate is bismuth phosphate or antimony phosphate;

[0008] The acetate is bismuth acetate, lead acetate, or antimony acetate.

[0009] Furthermore, the conductive carbon material is one or more of acetylene black, conductive carbon nanotubes, conductive carbon black, Ketjen black, and single-walled carbon nanotubes.

[0010] Furthermore, the adhesive is one or more of sodium alginate, carboxymethyl cellulose, and polyvinylidene fluoride.

[0011] Furthermore, the mass ratio of the active material, conductive carbon material and binder is 1:(0.2~4):(0.1~4).

[0012] Furthermore, the mass ratio of the active material, conductive carbon material and binder is 1:(0.4~1.6):(0.2~1).

[0013] The above-mentioned method for preparing the negative electrode current collector coating of a sodium metal battery without a negative electrode is carried out according to the following steps:

[0014] 1. Weigh out the active material, conductive carbon material, and binder, and add them to the liquid to prepare a slurry;

[0015] 2. Apply the slurry evenly to the copper / aluminum foil current collector;

[0016] 3. The coated current collector is dried to remove the solution from the wet slurry, resulting in a current collector coating for a sodium metal battery without a negative electrode. The areal density of this coating, consisting of active material, conductive carbon material, and binder, is 0.1~2 mg / cm³. 2 .

[0017] Furthermore, the liquid mentioned in step one is water or N-methylpyrrolidone.

[0018] A sodium-ion battery is assembled using the coated negative electrode current collector, separator, and positive electrode sheet of this invention. During the first charge, the negative electrode current collector spontaneously completes its initial sodium plating as sodium ions in the positive electrode material are intercalated and deintercalated. This invention utilizes the spontaneous displacement reaction that occurs during the initial sodium plating of the negative electrode current collector with metal fluorides, oxides, phosphates, or acetates. The resulting elemental metal / alloy serves as a nucleation seed, and sodium salts such as sodium fluoride, sodium oxide, sodium phosphate, and sodium acetate enter the solid electrolyte interface. The sodium-loving metal nucleation seed obtained through displacement can effectively reduce the nucleation overpotential during the sodium plating process through alloying, achieving regular, large-sized initial nucleation to induce uniform and dense sodium deposition. The sodium-rich solid electrolyte interface can effectively reduce electron spillover and decrease interfacial side reactions between the electrolyte and sodium metal. Through the combination of these two factors, an average coulombic efficiency greater than 99.5% is achieved in a sodium-current-current half-cell, and stable cycling is achieved in a sodium-free negative electrode battery.

[0019] The non-negative electrode current collector coating of this invention can be used in the field of sodium batteries or sodium metal batteries. Attached Figure Description

[0020] Figure 1 These are scanning electron microscope images of the negative electrode current collector prepared in Example 1 after initial sodium plating;

[0021] Figure 2 The nucleation overpotential curves of the sodium battery prepared in Example 1 and the commercial current collector battery at different current densities are shown.

[0022] Figure 3The nucleation overpotential curves of the sodium battery prepared in Example 1 and the commercial current collector battery at different current densities are shown.

[0023] Figure 4 The sodium battery prepared in Example 1 and the commercial current collector battery are compared at 1 mA cm⁻¹. -2 Cyclic performance curves at current density;

[0024] Figure 5 These are Kelvin probe force microscopy images of the sodium battery prepared in Example 1 and a commercial current collector battery;

[0025] Figure 6 This is a cycle performance curve of a full cell assembled with the negative electrode current collector prepared in Example 1 and the sodium iron pyrophosphate positive electrode.

[0026] Figure 7 The sodium battery prepared in Example 2 and the commercial current collector battery are compared at 1 mA cm⁻¹. -2 Cyclic performance curves at current density;

[0027] Figure 8 This is a cycle performance curve of a full cell assembled with the negative electrode current collector prepared in Example 3 and the positive electrode sodium iron pyrophosphate. Detailed Implementation

[0028] The beneficial effects of the present invention will be verified using the following examples.

[0029] Example 1: The preparation method of the negative electrode current collector coating of the sodium metal battery without negative electrode in this example is carried out according to the following steps:

[0030] 1. Weigh out bismuth fluoride, conductive carbon black and polyvinylidene fluoride in a mass ratio of 0.4:0.4:0.2 and mix them evenly. Add N-methylpyrrolidone and mix evenly to obtain a slurry.

[0031] 2. Apply the slurry evenly to the copper / aluminum foil current collector;

[0032] 3. The coated current collector is dried to remove the liquid from the slurry, resulting in a current collector coating for a sodium metal battery without a negative electrode. The total areal density of the coating, consisting of bismuth fluoride, conductive carbon black, and polyvinylidene fluoride, is 0.5 mg / cm³. 2 .

[0033] The coated negative electrode current collector prepared in Example 1 was assembled with a separator and sodium metal, and 120 µL of electrolyte (1.0 M NaPF6-DEGDME) was injected to obtain a coin cell. A coin cell assembled with a commercial current collector served as a control. In the coin cell, the coated negative electrode current collector prepared in Example 1 or the commercial current collector was used as the positive electrode. Cyclic testing was conducted using a discharge-charge cycle, with capacity cutoff for discharge and voltage cutoff for charging (cutoff voltage 1.0 V).

[0034] The scanning electron microscope (SEM) image of the coated negative electrode current collector after the first discharge of the coin half-cell assembled with the coated negative electrode current collector prepared in Example 1 is shown below. Figure 1 As shown, from Figure 1 It can be seen that regular large-size initial nucleation of sodium metal occurs on the modified current collector prepared in Example 1.

[0035] The nucleation overpotential curves of a coin cell assembled with a coated negative electrode current collector prepared in Example 1 and a coin cell assembled with a commercial current collector at different current densities are shown in the figure below. Figure 2 As shown, from Figure 2 It can be seen that at 1 mA cm -2 At the current density, the nucleation overpotential of the coin cell assembled with the coated negative electrode current collector prepared in Example 1 is 2.1 mV, while the nucleation overpotential of the coin cell assembled with the commercial current collector is 34.1 mV.

[0036] The nucleation overpotential curves of a coin cell assembled with a coated negative electrode current collector prepared in Example 1 and a coin cell assembled with a commercial current collector at different current densities are shown in the figure below. Figure 3 As shown, from Figure 3 It can be seen that the coin cell assembled with the coated negative electrode current collector prepared in Example 1 exhibits a current density ranging from 1 mA cm⁻¹. -2 Increased to 3 mA cm -2 At that time, the nucleation overpotential did not increase significantly, while the nucleation overpotential of coin cells assembled with commercial current collectors increased significantly.

[0037] The coin cell assembled with the coated negative electrode current collector prepared in Example 1 and the coin cell assembled with commercial current collectors at 1 mA cm⁻¹ -2 Cyclic performance curves at current density are as follows Figure 4 As shown, from Figure 4 It can be seen that the coin half-cell assembled with the coated negative electrode current collector prepared in Example 1 exhibits a performance of 1 mA cm⁻¹. -2 Deposition of 2 mAh cm at current density -2 At that time, the average Coulomb efficiency was 99.9%.

[0038] Kelvin probe force microscopy images of a coin cell assembled with a coated negative electrode current collector prepared in Example 1 and a coin cell assembled with a commercial current collector are shown below. Figure 5 As shown, from Figure 5 It can be seen that the average potential of the solid electrolyte interface formed by the sodium battery prepared in Example 1 is 24 mV.

[0039] A coin cell full cell was assembled using sodium iron pyrophosphate positive electrode, a separator, and a coated negative electrode current collector prepared in Example 1, and 120 µL of electrolyte (1.0 M NaPF6-DEGDME) was injected. The full cell was first pre-cycled at 0.05 C for 3 cycles, followed by a long-term cycle test at 2 C, with a charge-discharge range of 3.75–1.5 V. The resulting cycle performance curves are shown below. Figure 6 As shown, from Figure 6 It can be seen that the full cell with the coated negative electrode current collector prepared in Example 1 can achieve 300 cycles with a capacity retention of 84.04%.

[0040] Example 2: The preparation method of the negative electrode current collector coating of the sodium metal battery without negative electrode in this example is carried out according to the following steps:

[0041] 1. Weigh out iron fluoride, conductive carbon black and polyvinylidene fluoride according to the mass ratio of 0.35:0.45:0.2, mix them evenly, add N-methylpyrrolidone, mix evenly to obtain slurry;

[0042] 2. Apply the slurry evenly to the aluminum foil current collector;

[0043] Third, the coated current collector is dried to remove the liquid from the wet slurry, resulting in a current collector coating for a sodium metal battery without a negative electrode. The total areal density of this coating, consisting of iron fluoride, conductive carbon black, and polyvinylidene fluoride, is 0.8 mg / cm³. 2 .

[0044] Using the same method as in Example 1, a coin cell was prepared with the coated negative electrode current collector prepared in Example 2. Cyclic tests were then conducted using a discharge-then-charge method, with capacity cutoff for discharge and voltage cutoff for charging. The cutoff voltage was 1.0 V.

[0045] A coin cell prepared using the coated negative electrode current collector of Example 2 and a coin cell prepared using a commercial current collector were compared at 1 mA cm⁻¹. -2 Cyclic performance curves at current density are as follows Figure 7 As shown, from Figure 7It can be seen that the coin half-cell prepared using the coated negative electrode current collector prepared in Example 2 achieves a performance of 1 mA cm⁻¹. -2 Deposition of 2 mAh cm at current density -2 At that time, the average Coulomb efficiency was 99.6%.

[0046] Example 3: The preparation method of the negative electrode current collector coating of the sodium metal battery without negative electrode in this example is carried out according to the following steps:

[0047] 1. Weigh out antimony oxide, conductive carbon black and polyvinylidene fluoride in a mass ratio of 0.30:0.45:0.25, mix them evenly, add N-methylpyrrolidone, mix evenly to obtain a slurry;

[0048] 2. Apply the slurry evenly to the aluminum foil current collector;

[0049] 3. The coated current collector is dried to remove the liquid from the wet slurry, resulting in a current collector coating for a sodium metal battery without a negative electrode. The surface density of this coating, consisting of antimony oxide, conductive carbon black, and polyvinylidene fluoride, is 0.8 mg / cm³. 2 .

[0050] A coin cell was assembled using sodium iron pyrophosphate cathode, separator, and coated negative electrode current collector prepared in Example 3, and 120 µL of electrolyte (1.0 M NaPF6-DEGDME) was injected. The cell was pre-cycled at 0.05 C for 3 cycles, followed by long-term cycling at 1C, with a charge-discharge range of 3.75–1.5 V. The resulting cycle performance curves are shown below. Figure 8 As shown, from Figure 8 It can be seen that the full cell with the coated negative electrode current collector prepared in Example 3 can achieve 150 cycles with a capacity retention of 80.04%.

Claims

1. A coating for a negative electrode current collector in a sodium metal battery without a negative electrode, characterized in that, The coating is made of active material, conductive carbon material and binder; wherein the active material is metal fluoride, oxide, phosphate or acetate; The metal fluoride is bismuth fluoride, iron fluoride, or tin fluoride; The oxide is bismuth oxide or antimony oxide; The phosphate is bismuth phosphate or antimony phosphate; The acetate is bismuth acetate, lead acetate, or antimony acetate.

2. The coating for a negative electrode current collector in a sodium metal battery without a negative electrode according to claim 1, characterized in that, The conductive carbon material is one or more of acetylene black, conductive carbon nanotubes, conductive carbon black, Ketjen black, and single-walled carbon nanotubes.

3. The non-negative electrode current collector coating for a sodium metal battery according to claim 1 or 2, characterized in that, The adhesive is one or more of sodium alginate, carboxymethyl cellulose, and polyvinylidene fluoride.

4. The current collector coating for a non-negative electrode sodium metal battery according to claim 1 or 2, characterized in that, The mass ratio of the active substance, conductive carbon material and binder is 1:(0.2~4):(0.1~4).

5. A current collector coating for a non-negative electrode sodium metal battery according to claim 1 or 2, characterized in that, The mass ratio of the active substance, conductive carbon material and binder is 1:(0.4~1.6):(0.2~1).

6. The method for preparing a current collector coating for a negative electrode-free sodium metal battery according to claim 1, characterized in that, This method is performed in the following steps:

1. Weigh out the active material, conductive carbon material, and binder, and add them to the liquid to prepare a slurry; 2. Apply the slurry evenly to the copper / aluminum foil current collector; 3. The coated current collector is dried to remove the solution from the wet slurry, resulting in a current collector coating for a sodium metal battery without a negative electrode. The areal density of this coating, consisting of active material, conductive carbon material, and binder, is 0.1~2 mg / cm³. 2 .

7. The method for preparing a current collector coating for a negative electrode-free sodium metal battery according to claim 6, characterized in that, The liquid mentioned in step one is water or N-methylpyrrolidone.

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