Acrylic Cathode Binder for Lithium-Sulfur Polysulfide Retention
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Solution Overview
Problem
Lithium-sulfur secondary batteries face challenges such as high solubility of lithium polysulfide, low lifetime and output characteristics, low electrical conductivity of sulfur, and poor stability due to the use of lithium metal, particularly the undesired dissolution of lithium polysulfide during charge-discharge cycles.
Innovation Solution
A composition for forming a cathode active layer in lithium-sulfur secondary batteries is developed, utilizing an acrylic binder with polymerized units of a polymerizable monomer containing a polar functional group. This binder interacts with the cathode active material, effectively preventing the dissolution of lithium polysulfide into the electrolyte and enhancing the dispersion of conductive materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If sulfur is used as cathode active material to achieve high energy density, then energy storage capacity is improved, but lithium polysulfide dissolves in electrolyte causing poor cycle characteristics
Solution Approach 1:
A binder comprising polymer particles is introduced as an intermediary substance between sulfur and electrolyte. The binder adsorbs lithium polysulfide through polar functional groups (carboxyl, hydroxyl, or amine groups), preventing its dissolution in electrolyte while maintaining sulfur's high energy density benefits
Solution Approach 2:
The cathode active layer is designed as a composite material system combining sulfur, conductive carbon, and the specialized binder in specific ratios. This composite structure maintains high energy density from sulfur while the binder component prevents polysulfide dissolution, resolving the cycle characteristic problem
2Stability of the object's composition
If conventional binders are used to hold cathode materials, then electrode structure is maintained, but lithium polysulfide dissolution is not effectively prevented
Solution Approach 1:
The binder's chemical parameters are specifically modified by incorporating polymer particles with polar functional groups (carboxyl, hydroxyl, or amine) in controlled amounts (1-20 parts by weight per 100 parts binder). This parameter change enables the binder to adsorb lithium polysulfide effectively while maintaining electrode structural stability
Solution Approach 2:
The binder is designed with localized polar functional groups concentrated in specific regions of the cathode active layer. These functional groups are positioned to interact with lithium polysulfide at the sulfur-electrolyte interface, providing localized polysulfide retention while maintaining overall electrode structure
3Use of energy by moving object
If sulfur content is increased to improve energy density, then theoretical energy storage increases, but electrical conductivity decreases
Solution Approach 1:
The cathode active layer is formulated as a composite with optimized ratios of sulfur (80-95 parts), conductive carbon (3-15 parts), and binder (1-5 parts). This composite structure maintains high sulfur content for energy density while conductive carbon provides electrical conductivity pathways
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 use of the acrylic binder in the cathode active layer significantly improves the cycle characteristics and electrochemical performance of lithium-sulfur secondary batteries by inhibiting the dissolution of lithium polysulfide and ensuring excellent dispersion and retention of conductive materials.
Implementation Method 1
the binder comprises polymer particles obtained by polymerization of: (a) 1-80 parts by weight of a (meth)acrylic acid ester monomer; (b) 1-20 parts by weight of an unsaturated carboxylic acid monomer
Implementation Method 2
the binder comprises polymer particles obtained by polymerization of: (a) 1-80 parts by weight of a (meth)acrylic acid ester monomer
Data Source
AI summary
The present invention relates to a binder for a lithium-sulfur secondary battery cathode, and a composition containing the same. The binder of the present application enables a cathode active material electrolyte to have excellent resistance.