Method for resisting non-Faraday corrosion of lithium metal negative electrode

Abstract

The invention discloses a method for resisting non-Faraday corrosion of a lithium metal negative electrode. The electrolyte adopts an ether ester mixed solvent system, and solutes comprise 0.2-0.3 mol / L of lithium nitrate, 1-4 g / L of halogenated lithium salt lithium chloride, lithium bromide (the mass ratio is 1: 3) and 0.5-1 mol / L of bis (trifluoromethylsulfonyl) lithium imide. A compact and stable composite interface layer can be constructed on the surface of the lithium metal by performing a single charge-discharge cycle for 1 hour under the current density of 0.5-2mA / cm < 2 >. The interface can effectively inhibit side reaction and substance migration between the electrolyte and lithium metal, obviously improve the interface stability and delay chemical corrosion in a standing state, so that the cycle life and calendar life of the battery are prolonged, and a practical electrolyte solution is provided for development of the high-performance lithium metal battery.

Description

Technical Field

[0001] This invention belongs to the fields of materials chemistry and lithium battery technology, and specifically relates to a method for resisting non-Faraday corrosion of lithium metal anodes. Background Technology

[0002] Lithium metal is valued for its exceptional theoretical specific capacity (3860 mAh g⁻¹). - ¹) Lower electrochemical potential (-3.04 V relative to the standard hydrogen electrode) and lower density (0.534 g cm⁻¹) - Lithium (Li₂³) is considered a promising anode material for next-generation high-energy rechargeable batteries. However, despite significant progress in cycle reversibility, its calendar life remains severely limited by the persistent problem of lithium metal corrosion. The effects of lithium metal corrosion on electrochemical performance are multifaceted and far-reaching. First, the oxidation of lithium metal directly leads to the loss of active lithium, causing capacity decay during subsequent discharge. More seriously, corrosion occurring at the root of deposited lithium can electrically isolate it from the current collector, further exacerbating irreversible capacity loss. Simultaneously, corrosion byproducts unevenly accumulate on the lithium metal surface, disrupting uniform charge transport and promoting dendrite formation and growth, increasing the risk of electrical insulation during cycling.

[0003] To address the aforementioned challenges, researchers have explored methods to suppress lithium metal corrosion from various perspectives. One approach involves manufacturing metal electrodes to mitigate corrosion, primarily employing foil structures to reduce the electrolyte contact area and enhancing corrosion resistance by minimizing structural defects; and introducing optimized current collectors and electron transfer suppression materials into thin electrodes to alleviate galvanic corrosion. Another approach focuses on surface modification of the metal anode, employing alloying, artificial coatings, and crystal manipulation strategies to enhance the corrosion resistance of lithium metal anodes. While these methods have achieved some breakthroughs, they all have limitations, such as the inability to dynamically modify the solid electrolyte interphase (SEI), leading to ineffective corrosion suppression. Another approach is to construct a stable SEI with high ionic conductivity. An ideal SEI layer can not only effectively guide uniform lithium ion deposition and inhibit dendrite growth but also dynamically repair damage during cycling and effectively block the continuous corrosion of lithium metal by the electrolyte under long-term static conditions, thereby significantly inhibiting the formation of "dead lithium" and capacity decay, and improving cycle stability and calendar life. Summary of the Invention

[0004] To address the shortcomings of the existing technology, this invention provides a method for resisting non-Faraday corrosion of lithium metal anodes, which can effectively suppress corrosion of lithium metal anodes during the resting process and improve the calendar life of lithium metal batteries.

[0005] The technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: a method for resisting non-Faraday corrosion of lithium metal anodes, specifically including the following steps: 1) In an inert atmosphere-protected glove box (with water and oxygen content both below 0.1 ppm), fluoroethylene carbonate and diethylene glycol dimethyl ether are mixed at a volume ratio of 5:95 and stirred thoroughly at room temperature until a homogeneous and transparent electrolyte base solution is formed.

[0006] 2) Weigh appropriate amounts of lithium nitrate, lithium halide salt (lithium chloride and lithium bromide mixed in a 1:3 mass ratio), and lithium bis(trifluoromethanesulfonyl)imide according to a set ratio, and add them together to the fluoroethylene carbonate / diethylene glycol dimethyl ether mixed base solution prepared in step 1). Stir at room temperature until all components are fully dissolved and the system is clear and transparent to finally obtain a functional electrolyte for inhibiting non-Radar corrosion of lithium metal anode.

[0007] 3) During the assembly of the lithium symmetric battery, the functional electrolyte prepared in step 2) is injected to fully wet the battery separator.

[0008] 4) Apply a specific current density and time to the battery for charge and discharge cycles to induce the formation of a stable interface passivation layer (SEI) on the lithium anode surface.

[0009] In some embodiments, the concentration of lithium nitrate in the functional electrolyte is 0.2~0.3 mol / L, the concentration of lithium halide salt (lithium chloride and lithium bromide mixed in a 1:3 mass ratio) is 1~4 g / L, and the concentration of lithium bis(trifluoromethanesulfonyl)imide is 0.5~1 mol / L.

[0010] In some embodiments, the current density set in step 4) is 0.5 ~ 2 mA / cm². 2 The single charge / discharge time is set to 1 hour. This embodiment aims to promote the formation of a denser and more stable SEI layer on the surface of the lithium metal electrode by using a lower current density, thereby suppressing non-Radil corrosion.

[0011] In some embodiments, during the assembly of the lithium symmetric battery (CR2032 type) in step 3), the battery structure sequentially includes a positive electrode shell, a lithium metal positive electrode, a polypropylene separator, a lithium metal negative electrode, a stainless steel gasket, a spring sheet, and a negative electrode shell. During assembly, the functional electrolyte is drop-added between the separator and the lithium negative electrode to ensure that the polypropylene separator is fully wetted, thereby promoting the formation of a stable interface layer.

[0012] Compared with existing technologies, the advantages of this invention are as follows: Under specific charge-discharge cycle conditions of lithium symmetric batteries, lithium nitrate added to the electrolyte constructs a stable SEI layer rich in lithium oxide on the surface of the lithium metal anode. Simultaneously, the lithium halide salts lithium chloride and lithium bromide introduced into the electrolyte can induce moderate pitting corrosion in localized micro-regions, forming a microstructure regulation effect. The synergistic effect of the two lithium salts achieves a dynamic balance between "protective passivation" and "controlled corrosion," ultimately forming a denser and more stable SEI structure. This composite interface can significantly suppress side reactions and mass migration between lithium metal and the electrolyte, effectively improving interface stability during cycling and delaying chemical corrosion of lithium metal under long-term static conditions, thereby significantly enhancing the cycle life and calendar life of the battery, providing a feasible electrolyte solution for the design of high-performance lithium metal batteries. Attached Figure Description

[0013] Figure 1 The polarization curve of the lithium symmetric battery obtained in Example 1 of this invention in the blue battery system; Figure 2 The impedance diagram of the lithium symmetric battery obtained in Example 1 of this invention was measured on an electrochemical workstation. Figure 3 This is a microscopic image of the lithium sheet surface of the negative electrode of the lithium symmetric battery obtained in Example 1 of the present invention. Detailed Implementation

[0014] The present invention will be further described in detail below with reference to the embodiments.

[0015] Example 1 In preparing the functional electrolyte for inhibiting non-Radar corrosion of lithium metal anodes in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), 0.1 mL of fluoroethylene carbonate and 1.9 mL of diethylene glycol dimethyl ether were first mixed uniformly as the base solvent. Subsequently, 0.2 mol / L (0.02758 g) lithium nitrate, a mixed lithium halide salt with a total concentration of 1 g / L (containing 0.0005 g of lithium chloride and 0.0015 g of lithium bromide in a mass ratio of 1:3), and 1 mol / L (0.5742 g) lithium bis(trifluoromethanesulfonyl)imide were added to the above mixed solvent. The mixture was stirred vigorously at room temperature for 12 hours until a homogeneous and transparent electrolyte was formed. In a glove box filled with argon (H2O<0.1 ppm, O2<0.1 ppm), the CR2032 lithium symmetric battery was assembled in sequence: the positive electrode shell, lithium metal positive electrode, polypropylene separator, electrolyte resistant to Faraday corrosion added to fully wet the separator, lithium metal negative electrode, stainless steel gasket, spring sheet, and finally the negative electrode shell was sealed.

[0016] The assembled lithium symmetric battery was connected to the Blue Electric high-precision battery testing system at a speed of 0.5 mA cm⁻¹. - A single charge-discharge cycle was performed at a current density of ², with each charge and discharge cycle lasting 1 hour (see [reference]). Figure 1 After this cycle, the battery was allowed to stand at room temperature for 120 hours. Following this standing period, electrochemical impedance spectroscopy (EIS) was performed on the battery using an electrochemical workstation (see [link to EIS]). Figure 2 After the test, the battery was transferred to an argon atmosphere glove box for disassembly, and the surface morphology of the negative lithium electrode was observed using an optical microscope (see [link]). Figure 3 ).

[0017] Example 2 In preparing the functional electrolyte for inhibiting non-Radar corrosion of lithium metal anodes in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), 0.1 mL of fluoroethylene carbonate and 1.9 mL of diethylene glycol dimethyl ether were first mixed thoroughly as the base solvent. Then, 0.3 mol / L (0.0414 g) of lithium nitrate, a mixed lithium halide salt with a total concentration of 4 g / L (containing 0.002 g of lithium chloride and 0.006 g of lithium bromide in a mass ratio of 1:3), and 0.5 mol / L (0.2871 g) of lithium bis(trifluoromethanesulfonyl)imide were added to the above mixed solvent. The mixture was stirred vigorously at room temperature for 12 hours until a homogeneous and transparent electrolyte was formed. In a glove box filled with argon (H2O<0.1 ppm, O2<0.1 ppm), the CR2032 lithium symmetric battery was assembled in sequence: the positive electrode shell, lithium metal positive electrode, polypropylene separator, the above-mentioned anti-Faraday corrosion electrolyte was added to fully wet the separator, lithium metal negative electrode, stainless steel gasket, spring sheet, and finally the negative electrode shell was sealed.

[0018] The assembled lithium symmetric battery was connected to the Blue Electric high-precision battery testing system at 2 mA cm⁻¹. - A single charge-discharge cycle was performed at a current density of ², with each charge and discharge cycle lasting 1 hour (see [reference]). Figure 1 After this cycle, the battery was allowed to stand at room temperature for 120 hours. Following this standing period, electrochemical impedance spectroscopy (EIS) was performed on the battery using an electrochemical workstation (see [link to EIS]). Figure 2 After the test, the battery was transferred to an argon atmosphere glove box for disassembly, and the surface morphology of the negative lithium electrode was observed using an optical microscope (see [link]). Figure 3 ).

[0019] Example 3 In preparing the functional electrolyte for inhibiting non-Radar corrosion of lithium metal anodes in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), 0.1 mL of fluoroethylene carbonate and 1.9 mL of diethylene glycol dimethyl ether were first mixed thoroughly as the base solvent. Then, 0.25 mol / L (0.0345 g) lithium nitrate, a mixed lithium halide salt with a total concentration of 3 g / L (containing 0.0015 g lithium chloride and 0.0045 g lithium bromide in a mass ratio of 1:3), and 1 mol / L (0.5742 g) lithium bis(trifluoromethanesulfonyl)imide were added to the above mixed solvent. The mixture was stirred vigorously at room temperature for 12 hours until a homogeneous and transparent electrolyte was formed. In a glove box filled with argon (H2O<0.1 ppm, O2<0.1 ppm), the CR2032 lithium symmetric battery was assembled in sequence: the positive electrode shell, lithium metal positive electrode, polypropylene separator, the above-mentioned anti-Faraday corrosion electrolyte was added to fully wet the separator, lithium metal negative electrode, stainless steel gasket, spring sheet, and finally the negative electrode shell was sealed.

[0020] The assembled lithium symmetric battery was connected to the Blue Electric high-precision battery testing system at 1 mA cm⁻¹. - A single charge-discharge cycle was performed at a current density of ², with each charge and discharge cycle lasting 1 hour (see [reference]). Figure 1 After this cycle, the battery was allowed to stand at room temperature for 120 hours. Following this standing period, electrochemical impedance spectroscopy (EIS) was performed on the battery using an electrochemical workstation (see [link to EIS]). Figure 2 After the test, the battery was transferred to an argon atmosphere glove box for disassembly, and the surface morphology of the negative lithium electrode was observed using an optical microscope (see [link]). Figure 3 ).

[0021] Example 4 In preparing the functional electrolyte for inhibiting non-Radar corrosion of lithium metal anodes in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), 0.1 mL of fluoroethylene carbonate and 1.9 mL of diethylene glycol dimethyl ether were first mixed thoroughly as the base solvent. Then, 0.25 mol / L (0.0345 g) lithium nitrate, a mixed lithium halide salt with a total concentration of 2 g / L (containing 0.001 g lithium chloride and 0.003 g lithium bromide in a mass ratio of 1:3), and 0.5 mol / L (0.2871 g) lithium bis(trifluoromethanesulfonyl)imide were added to the above mixed solvent. The mixture was stirred vigorously at room temperature for 12 hours until a homogeneous and transparent electrolyte was formed. In a glove box filled with argon (H2O<0.1 ppm, O2<0.1 ppm), the CR2032 lithium symmetric battery was assembled in sequence: the positive electrode shell, lithium metal positive electrode, polypropylene separator, the above-mentioned anti-Faraday corrosion electrolyte was added to fully wet the separator, lithium metal negative electrode, stainless steel gasket, spring sheet, and finally the negative electrode shell was sealed.

[0022] The assembled lithium symmetric battery was connected to the Blue Electric high-precision battery testing system at a frequency of 1.5 mA cm⁻¹. - A single charge-discharge cycle was performed at a current density of ², with each charge and discharge cycle lasting 1 hour (see [reference]). Figure 1 After this cycle, the battery was allowed to stand at room temperature for 120 hours. Following this standing period, electrochemical impedance spectroscopy (EIS) was performed on the battery using an electrochemical workstation (see [link to EIS]). Figure 2 After the test, the battery was transferred to an argon atmosphere glove box for disassembly, and the surface morphology of the negative lithium electrode was observed using an optical microscope (see [link]). Figure 3 ).

Claims

1. A method for resisting non-Faraday corrosion on a lithium metal anode, characterized in that, The method includes the following steps: 1) In a glove box with an inert atmosphere where the water and oxygen content are both below 0.1 ppm, fluoroethylene carbonate and diethylene glycol dimethyl ether are mixed at a volume ratio of 5:95 and stirred thoroughly at room temperature until a homogeneous and transparent electrolyte base solution is formed. 2) Weigh appropriate amounts of lithium nitrate, lithium chloride and lithium bromide in a mass ratio of 1:3, and lithium bis(trifluoromethanesulfonyl)imide in a set ratio, and add them together to the fluoroethylene carbonate / diethylene glycol dimethyl ether mixed base solution prepared in step 1). Stir at room temperature until all components are fully dissolved and the system is clear and transparent to finally obtain a functional electrolyte for inhibiting the non-Radar corrosion of lithium metal anode. 3) During the assembly of the lithium symmetric battery, the functional electrolyte prepared in step 2) is injected to fully wet the battery separator; 4) Applying a specific current density and time to the lithium symmetric battery to charge and discharge cycles promotes the formation of a stable interface passivation layer SEI on the surface of the lithium anode.

2. The method for resisting non-Faraday corrosion of lithium metal anodes according to claim 1, characterized in that, The functional electrolyte contains lithium nitrate at a concentration of 0.2 to 0.3 mol / L, lithium halide salt prepared by mixing lithium chloride and lithium bromide at a mass ratio of 1:3 at a concentration of 1 to 4 g / L, and lithium bis(trifluoromethanesulfonyl)imide at a concentration of 0.5 to 1 mol / L.

3. The method for resisting non-Faraday corrosion of lithium metal anodes according to claim 1, characterized in that: The charge-discharge cycle in step 4) is performed at a current density of 0.5 ~ 2 mA / cm², and the duration of each charge or discharge is set to 1 hour.

4. The method for resisting non-Faraday corrosion of lithium metal anodes according to claim 1, characterized in that: The lithium symmetric battery used in step 3) is a CR2032 type lithium symmetric battery. Its internal components, in order from bottom to top, are: positive electrode shell, lithium metal positive electrode, polypropylene separator, lithium metal negative electrode, stainless steel gasket, spring sheet and negative electrode shell. During assembly, the functional electrolyte needs to be dropped between the polypropylene separator and the lithium metal negative electrode to fully wet the interface.

Images