Li-S Battery Binder Copolymer for Polysulfide Retention
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Solution Overview
Problem
Conventional methods for lithium-sulfur secondary batteries face issues with adhesive force at the electrode, conductivity of the positive electrode, sublimation of sulfur-based materials, and leaching of sulfur-based materials, leading to poor capacity and lifetime characteristics.
Innovation Solution
A binder comprising a copolymer formed by polymerizing alkyl acrylate or alkyl methacrylate with functional groups and acrylic acid or methacrylic acid is used to improve adhesion and stability, featuring a specific functional group structure and solubility, allowing for efficient dispersion and low solubility in electrolytes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional binders are used in lithium-sulfur batteries, then the battery can be assembled, but the adhesive force at the electrode is insufficient leading to poor electrode stability
Solution Approach 1:
The patent changes the chemical parameters of the binder by specifying functional groups (carboxyl, hydroxyl, amino) and their content ranges (5-50 wt%). This chemical parameter modification enables strong chemical bonding between the binder and sulfur-based materials, resolving the adhesive force deficiency of conventional binders while maintaining electrode stability.
Solution Approach 2:
The patent creates a composite binder system combining organic binder materials with specific functional groups and inorganic fillers (5-50 wt%). This composite structure leverages the adhesive properties of organic polymers and the stability of inorganic materials, simultaneously improving both adhesive force and electrode stability.
2Use of energy by moving object
If sulfur-based materials are used as positive electrode active material, then high energy storage density is achieved, but sublimation of sulfur-based materials occurs during electrode preparation
Solution Approach 1:
The patent applies preliminary action by using the binder to pre-encapsulate and protect sulfur-based materials before electrode preparation processes. The binder forms a protective matrix that prevents sublimation during heating and handling, allowing high energy storage density to be achieved without significant material loss.
Solution Approach 2:
The binder acts as an intermediary substance between the sulfur-based active material and the electrode structure. It mediates the interaction by providing a stable matrix that prevents direct exposure of sulfur to conditions causing sublimation, thus preserving the active material while maintaining high energy storage density.
3Power
If lithium polysulfide is produced during discharging, then electrochemical reaction occurs, but lithium polysulfide migrates to negative electrode causing leaching
Solution Approach 1:
The patent converts the harmful migration of lithium polysulfide into a beneficial effect by using functional groups in the binder that specifically adsorb polysulfides. The same chemical functionality that provides adhesion also traps lithium polysulfide, preventing its migration to the negative electrode while maintaining electrochemical reactivity.
Solution Approach 2:
The binder serves as an intermediary that intercepts lithium polysulfide between the positive and negative electrodes. The functional groups in the binder create binding sites that capture polysulfides, preventing their harmful migration while allowing the electrochemical reaction to proceed normally.
4Loss of substance
If additive is added to positive electrode mixture to adsorb sulfur, then sulfur leaching is inhibited, but conductive deterioration occurs
Solution Approach 1:
The patent applies local quality by concentrating the sulfur-adsorbing functional groups specifically at the interface between the binder and sulfur-based materials, rather than distributing additives throughout the entire electrode. This localized approach provides effective sulfur retention while maintaining bulk electrode conductivity.
Solution Approach 2:
The patent changes the approach from adding separate additive substances to incorporating sulfur-adsorbing functional groups directly into the binder structure. This parameter change in the binder's chemical composition provides sulfur leaching inhibition through intrinsic functionality rather than extrinsic additives, preserving electrode conductivity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The binder enhances electrode adhesion, maintains electrode capacity, and improves cycle characteristics by preventing sulfur-based material loss and ensuring high stability against electrolytes, resulting in improved lithium-sulfur secondary battery performance.
Implementation Method 1
a method of adding an additive having a property of adsorbing sulfur to the positive electrode mixture
Implementation Method 2
a problem of the sublimation of the sulfur-based material in preparing the electrode
Data Source
AI summary
A binder for a lithium-sulfur secondary battery and a lithium-sulfur secondary battery including the same. The binder includes a copolymer having a first polymerization unit derived from a first monomer and a second polymerization unit derived from a second monomer. The first monomer is alkyl acrylate having at least one functional group or alkyl methacrylate having at least one functional group. The second monomer is acrylic acid or methacrylic acid. The at least one functional group in the first monomer is a functional group having a single or repeated structure of a hydroxy group substituted or unsubstituted with alkyl having 1 to 4 carbon atoms, a thiol group substituted or unsubstituted with alkyl having 1 to 4 carbon atoms, or an amino group substituted or unsubstituted with alkyl having 1 to 4 carbon atoms. The second polymerization unit may have a lithiated form.