Metal-ligand complexing functional electrode binder and application method thereof

Abstract

The invention discloses a functionalized electrode binder based on a metal-ligand complexing system and a preparation and application method thereof. The binder is composed of a complexing structure formed by transition metal ions and nitrogen-containing or oxygen-containing ligands, and can generate directional adsorption with lithium polysulfide in the electrochemical process and promote redox conversion of the lithium polysulfide, so that the reaction kinetics and cycle stability of the sulfur positive electrode are improved. The binder can be directly prepared from the metal-ligand complexing waste liquid generated in the battery recovery process, no extra solvent or purification step is needed, and waste liquid resource utilization and green preparation are achieved. The capacity retention ratio of the electrode material prepared by the binder exceeds 80% after 200 cycles at 1C multiplying power, and the electrode material still has excellent stability at 60 DEG C under the condition of high loading capacity. The binder provided by the invention has double functions of adsorption and catalysis, is suitable for lithium-sulfur, lithium-selenium, sodium-sulfur and other high-energy-density secondary batteries, and has good universality and industrial application prospects.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage materials, specifically to a functionalized electrode binder based on a metal-ligand complex structure and its application in lithium-sulfur batteries, high-energy-density secondary batteries, and solid-state battery systems. The binder possesses both polysulfide adsorption and catalytic functions, which can improve the cycle stability and rate performance of the cathode. Background Technology

[0002] Lithium-sulfur batteries are known for their high theoretical specific capacity (1675 mAh·g). −1 ) and high energy density (2600 Wh·kg) −1 It is considered to be the next generation of high-energy storage system. However, its commercialization is still limited by the following problems: 1) Polysulfides dissolve and migrate during cycling, resulting in loss of active materials and capacity decay; 2) Slow electrochemical reaction kinetics, resulting in poor high-rate performance; 3) Traditional binders are inert and cannot effectively participate in the regulation of interfacial reactions.

[0003] Existing functional binders typically require complex organic synthesis or chemical modification, and still necessitate the addition of large amounts of solvents during the slurry preparation process, increasing costs and environmental burden. Furthermore, during battery recycling, the complexation-leaching treatment of cathode materials generates wastewater containing metal-ligand complex structures. This wastewater is generally considered waste and not utilized for high-value purposes. Therefore, there is an urgent need to develop an electrode binder system that can directly utilize recycled wastewater, possesses both adsorption and catalytic functions, and exhibits green preparation characteristics, in order to achieve resource recycling and improved electrochemical performance. Summary of the Invention

[0004] The purpose of this invention is to provide a functionalized electrode binder based on a metal-ligand complex system and its preparation and application method. By directly utilizing the metal-ligand complex waste liquid generated during battery recycling, the invention achieves synergistic resource utilization and binder functionalization.

[0005] The binder consists of a complex structure formed by transition metal ions and nitrogen- or oxygen-containing ligands, which can coordinate adsorption with lithium polysulfides and promote redox conversion, thereby improving the reaction kinetics and cycle stability of the cathode.

[0006] This invention has the following significant advantages: 1) Waste liquid resource utilization: directly utilizing the metal-ligand complex waste liquid generated during battery recycling as a binder to achieve closed-loop recycling; 2) Green and simple preparation: no additional solvent or purification steps are required during the pulping process, simplifying the process and saving energy; 3) Adsorption-catalysis dual function: the metal-ligand complex structure simultaneously achieves directional adsorption and catalytic conversion of polysulfides; 4) Significantly improved electrochemical performance: capacity retention ≥80% after 100-1000 cycles at 1C-5C rates, and at 40-60℃ and 5-20 mg·cm⁻¹...−2 It maintains stable cycle performance even under high load; 5) It is highly versatile: it is suitable for different metal-ligand systems and various high-energy storage batteries, such as lithium-selenium and sodium-sulfur systems. Attached Figure Description

[0007] To facilitate understanding of the present invention, the structure and working principle of the present invention will be further explained in conjunction with the accompanying drawings: Figure 1 This is a schematic diagram of the binder preparation and electrode construction process of the present invention; Figure 2 This is a schematic model of a metal-ligand complex structure; Figure 3 This is a schematic diagram of the adsorption-catalytic mechanism of polysulfides by binders; Figure 4 This is a comparison chart of the electrochemical performance of the binder of this invention and a comparative example, where (a) is the cycling performance curve at high rate (1C); (b) is the cycling performance curve at high temperature (60°C); and (c) is the cycling performance curve at high loading (10 mg·cm⁻¹). −2 The cycle performance curve is shown below. Detailed Implementation

[0008] The technical solution of the present invention will be further described below with reference to the embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and are not intended to limit the scope of protection.

[0009] Example 1: Co x Preparation and application of PEI complexed waste liquid binder

[0010] Waste liquid source: Waste liquid is obtained by using waste LiCoO2 cathode material and treating it with polyethyleneimine (PEI) complexation-leaching. The main components include Co-N coordination complex structure and some unreacted PEI polymer.

[0011] Binder preparation and use: The waste liquid is moderately concentrated and used directly as an electrode binder without the need for additional solvents or purification.

[0012] Prepare the slurry: sulfur / porous carbon: conductive carbon: binder = 7:2:1 (mass ratio), and after thorough homogenization, coat it onto aluminum foil, and then dry and roll it to form an electrode sheet.

[0013] Electrochemical performance: Assembled CR2032 type batteries with lithium foil as the negative electrode and a 1 M LiTFSI / 0.2 M LiNO3 / DOL:DME = 1:1 (volume ratio) electrolyte. Capacity retention ≥80% after 100–1000 cycles at 1C–5C; at 40–60℃ and 5–20 mg·cm⁻¹... −2 Under high load conditions, the capacity retention rate is still ≥80%.

[0014] Mechanism analysis: The Co-N coordination center can form directional coordination adsorption with polysulfides, while promoting the polysulfide conversion reaction, accelerating the electron and ion migration process, and realizing adsorption-catalysis synergy.

[0015] Example 2: Applicability verification for other metal or ligand systems

[0016] Using Ni x PEI or Fe x CA (Citrate) complexation waste liquid replaces Co x PEI, repeating the procedure of Example 1. The results show that the complexed systems significantly improve cycling stability and rate performance, verifying the versatility of the present invention.

[0017] It should be noted that the metal ions can be one or more combinations of Co, Ni, Fe, Mn, Cu, etc.; the ligands can be polyethyleneimine (PEI), ethylenediamine, polycarboxylic acids, pyridyl or imidazole functionalized polymers, etc. The binder can be suitable for different high-energy-density battery systems.

[0018] This invention provides a metal-ligand complex-type functionalized electrode binder that achieves synergistic unity of waste liquid resource utilization and performance enhancement. It is characterized by being green, simple, and efficient, and has broad industrialization and environmental protection value.

[0019] For those skilled in the art, any equivalent substitution of metal type, ligand type, or electrode system without departing from the spirit and substance of this invention should be considered as falling within the protection scope of this invention.

Claims

1. Claim 1: A metal-ligand complex functionalized electrode binder, characterized in that: The binder consists of a complex structure formed by transition metal ions and nitrogen- or oxygen-containing ligands. This complex structure can coordinate adsorb lithium polysulfides and promote their redox conversion. The binder is directly prepared from the metal-ligand complex waste liquid generated during battery recycling and can be used for electrode slurry preparation without additional solvents or purification steps.

2. Claim 2: The adhesive according to claim 1, wherein the transition metal ion is selected from one or more of Co, Ni, Fe, Mn, and Cu.

3. Claim 3: The adhesive according to claim 1 or 2, wherein the ligand is an organic compound or polymer containing amino, carboxyl, pyridyl or imidazole functional groups, including polyethyleneimine (PEI), ethylenediamine, citric acid or derivatives thereof.

4. Claim 4: The binder according to any one of claims 1 to 3, which forms a directional coordination structure with polysulfides through a metal-ligand center during the electrochemical process, thereby achieving adsorption-catalysis dual function and enhancing the polysulfide conversion rate.

5. Claim 5: A method for preparing the adhesive according to any one of claims 1 to 4, characterized in that... include: 1) Complexation-leaching treatment is performed on waste lithium battery cathode materials to obtain waste liquid containing metal-ligand complex structures; 2) The waste liquid can be directly used for electrode homogenization preparation without the need for additional solvents or purification steps.

6. Claim 6: The application of the binder according to any one of claims 1 to 5 in a high-energy secondary battery, wherein the electrode retains ≥80% capacity after 100 to 1000 cycles at a 1C to 5C rate, and maintains a capacity of ≥80% at 40 to 60°C and 5 to 20 mg·cm⁻¹. −2 It maintains stable cycle performance even under high load conditions.

7. Claim 7: The application according to claim 6, wherein the binder has an adsorption-catalysis dual function, capable of simultaneously adsorbing polysulfides and promoting their redox reactions.

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