Silicon Anode Coating for Swelling-Resistant Cycle Life
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Solution Overview
Problem
Si-based negative electrode active materials in lithium secondary batteries experience volumetric swelling during lithium intercalation and storage, leading to cracking and degradation of charge/discharge cycle life due to structural changes and mis-contact with the current collector.
Innovation Solution
A negative electrode with a silicon-based active material and a conductive material, coated with a polymer mixture of polyacrylic acid and polyvinyl alcohol, forming chemical bonds with the silicon-based active material to inhibit swelling and reduce resistance, thereby improving the battery's life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si-based active material is used to increase capacity, then battery capacity is improved, but volumetric swelling occurs during lithium intercalation causing structural degradation and reduced cycle life
Solution Approach 1:
A coating layer comprising a polymer mixture (polyacrylic acid and polyvinyl alcohol) is formed on the surface of the Si-based active material particles. This thin film coating accommodates the volumetric swelling during lithium intercalation while maintaining structural integrity, preventing particle cracking and contact loss with the current collector, thus preserving cycle life while retaining high capacity
Solution Approach 2:
The patent uses a composite coating layer formed by a mixture of polyacrylic acid and polyvinyl alcohol polymers. This composite material combines the benefits of both polymers: polyacrylic acid provides chemical bonding with Si and swelling accommodation, while polyvinyl alcohol enhances adhesion and structural stability. The composite coating effectively manages volumetric changes during cycling
2Quantity of substance
If Si-based active material is used to increase capacity, then battery capacity is improved, but cracking and mis-contact with current collector occur reducing reliability
Solution Approach 1:
The polymer coating layer acts as a flexible protective shell that accommodates volumetric expansion during lithium intercalation. This prevents particle cracking and maintains continuous electrical contact between the Si-based active material and the current collector throughout charge/discharge cycling, ensuring stable performance
Solution Approach 2:
The coating layer is applied beforehand to the Si-based active material particles to provide a protective cushion against volumetric swelling stresses. This pre-applied coating prevents structural degradation and contact loss before they can occur during battery operation
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 a polyacrylic acid-polyvinyl alcohol coating layer significantly enhances the cycle characteristics and capacity retention of lithium secondary batteries by preventing volumetric swelling and resistance increases, thus improving the battery's durability and life.
Implementation Method 1
containing a coating layer polymer which forms chemical bonds with silicon (Si) of the silicon-based active material
Implementation Method 2
the coating layer polymer is a mixture of polyacrylic acid with polyvinyl alcohol... significantly enhances the cycle characteristics and capacity retention... by preventing volumetric swelling and resistance increases
Data Source
AI summary
Disclosed is a negative electrode including: a current collector; a negative electrode active material layer disposed on at least one surface of the current collector, including a silicon-based active material and a conductive material, and containing no binder polymer; and a coating layer disposed on the surface of the negative electrode active material layer and in at least a part of the inside of the pores of the negative electrode active material layer, and containing a coating layer polymer forming a chemical bond with silicon (Si) of the silicon-based active material, wherein the content of the coating layer polymer is 0.3-2 parts by weight based on 100 parts by weight of the negative electrode active material layer, and the coating layer polymer is a mixture of polyacrylic acid with polyvinyl alcohol.