Negative Electrode Binder Composition for Silicon Crack Suppression
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in enhancing both capacity and cycle-life characteristics, particularly with the addition of silicon as a negative active material, which improves capacity but deteriorates cycle-life when used in excess.
Innovation Solution
A binder for lithium batteries comprising a copolymer with a polymer electrolyte, conductive polymer, and polydentate chelating agent is used in conjunction with a cellulose-based compound and second binder to create a negative electrode that exhibits improved self-healing properties and adhesion, thereby enhancing cycle-life and high-rate charge/discharge characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is added at a large amount (5 wt % or more) to improve capacity of crystalline carbonaceous active material, then capacity increases, but cycle-life deteriorates
Solution Approach 1:
A binder comprising a copolymer of a polymer electrolyte, a conductive polymer, and a polydentate chelating agent is introduced as an intermediary substance between silicon particles and the crystalline carbonaceous active material. This binder forms a protective matrix that accommodates silicon's volume expansion while maintaining structural integrity, thereby enabling high capacity utilization without cycle-life deterioration
Solution Approach 2:
The invention creates a composite negative active material layer combining silicon, crystalline carbonaceous active material, and a specially designed binder system. The binder itself is a composite of multiple functional components (polymer electrolyte, conductive polymer, polydentate chelating agent) that work synergistically to provide both high capacity and long cycle-life
2Reliability
If a binder system is designed to improve adhesion and self-healing properties, then cycle-life is enhanced, but device complexity increases
Solution Approach 1:
Multiple functional requirements (adhesion, conductivity, self-healing, electrolyte retention) are merged into a single copolymer binder system. The binder integrates a polymer electrolyte component, a conductive polymer component, and a polydentate chelating agent component into one unified material that performs all necessary functions simultaneously, avoiding the need for separate additive systems
Solution Approach 2:
The copolymer binder is designed with multi-functionality, where each component serves multiple purposes: the polymer electrolyte provides both adhesion and electrolyte retention, the conductive polymer ensures electrical conductivity while contributing to structural integrity, and the polydentate chelating agent enables self-healing while enhancing binding. This universal binder system replaces what would traditionally require multiple separate additives
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 proposed binder system effectively inhibits volume expansion-induced cracks in the negative electrode, improving the battery's processability, adhesion, and cycle-life while maintaining high capacity, as demonstrated by experimental results showing enhanced self-healing and capacity retention.
Implementation Method 1
a copolymer including a polymer electrolyte, a conductive polymer, and a polydentate chelating agent
Data Source
AI summary
Disclosed are a binder for a rechargeable lithium battery, a negative electrode including the binder, and a rechargeable lithium battery including the negative electrode. The binder may include a copolymer of a polymer electrolyte, a conductive polymer, and a polydentate chelating agent.