Silicon Anode Binder Coating for Volume Change Control
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Solution Overview
Problem
Silicon-based anodes in lithium secondary batteries experience degradation due to large volume changes during charging and discharging, leading to reduced cycle life and efficiency, as the binder's decreased elasticity causes voids and increased resistance.
Innovation Solution
An anode with a second nonaqueous binder coating layer is applied over a first coating layer containing an anode active material and conducting material, enhancing binding between the active material and current collector, thereby reducing volume changes and maintaining efficient lithium ion intercalation and deintercalation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the content of silicon-based anode active material is increased to provide higher energy density, then the capacity and energy density of the battery are improved, but the cycle characteristics are degraded due to severe volume change and anode degradation
Solution Approach 1:
A binder layer is coated on the surface of the silicon-based anode active material particles before assembling the battery. This binder layer acts as a cushioning layer that accommodates the volume expansion and contraction of silicon during charging and discharging cycles, preventing particle disintegration and maintaining electrical contact, thus resolving the contradiction between high capacity and cycle stability
Solution Approach 2:
The anode is constructed as a composite structure combining silicon-based active material particles with a binder material. The binder material provides mechanical strength and flexibility to accommodate silicon's volume changes, while the silicon particles provide high capacity. This composite approach allows the battery to achieve high energy density while maintaining good cycle characteristics
2Strength
If the amount of binder is increased to improve adhesion of anode active material, then the binding strength is improved, but the relative content of conducting material or anode active material is decreased, leading to decreased electrical conductivity and capacity
Solution Approach 1:
The binder is applied locally as a coating layer on the surface of the silicon-based anode active material particles rather than mixing it throughout the entire anode structure. This localized application ensures adequate adhesion at the particle surface while minimizing the overall binder content, thereby maintaining high electrical conductivity and capacity of the anode active material
Solution Approach 2:
A thin binder layer is formed on the surface of the anode active material particles. This thin film provides sufficient binding strength to hold particles together during volume changes while being thin enough to allow efficient electron and ion transport, thus maintaining electrical conductivity and capacity
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 additional coating layer improves the cycle life and charge-discharge characteristics of lithium secondary batteries by maintaining adequate binding and reducing resistance, preventing electrical isolation of the active material from the current collector.
Implementation Method 1
enhancing binding between the active material and current collector
Implementation Method 2
reversible intercalation and deintercalation of lithium ions
Data Source
AI summary
The present disclosure provides an anode for a secondary battery, including: an electrode current collector; a first coating layer formed on the electrode current collector and including an anode active material, a first nonaqueous binder and a conducting material; and a second coating layer formed on the first coating layer and including a second nonaqueous binder. Since the anode of the present disclosure can reduce volume change of the anode active material, a lithium secondary battery including same may have improved cycle characteristics.