Si Anode Binder Structure for Crack-Tolerant Lithium Batteries
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Solution Overview
Problem
Si-based negative electrode active materials in lithium secondary batteries experience significant volume changes during charge/discharge cycles, leading to cracking, detachment from the current collector, and reduced charge/discharge capacity due to mechanical stress and electrolyte consumption.
Innovation Solution
A lithium secondary battery design incorporating a Si-based negative electrode with a first binder polymer to bind the active material and conductive material, and a second binder polymer coated in the cracks formed during activation, ensuring connectivity and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si-based negative electrode active material is used to achieve high charge/discharge capacity, then capacity is improved, but volume change during charge/discharge causes cracking and detachment
Solution Approach 1:
A coating layer is formed on the Si-based negative electrode active material before battery assembly. This coating layer acts as a preliminary protective structure that accommodates volume expansion and prevents crack formation during subsequent charge/discharge cycles, thereby maintaining electrode integrity while preserving high capacity
Solution Approach 2:
The negative electrode is designed as a composite structure combining Si-based active material with a protective coating layer. This composite approach allows the Si core to provide high capacity while the coating layer provides structural stability and prevents deterioration from volumetric changes
2Quantity of substance
If Si-based negative electrode active material undergoes volumetric swelling, then charge/discharge capacity is improved, but mechanical stress generates cracks and reduces durability
Solution Approach 1:
The coating layer serves as a cushioning layer that absorbs and distributes the mechanical stress generated during Si expansion. This beforehand cushioning prevents stress concentration and crack initiation, thereby extending battery life while maintaining high capacity
Solution Approach 2:
A flexible coating layer is applied to the Si-based active material. This thin film structure can accommodate volumetric changes through elastic deformation, preventing crack propagation and maintaining electrode integrity throughout the battery's operational life
3Quantity of substance
If cracks form in the negative electrode active material, then charge/discharge capacity increases initially, but electrical short-circuit occurs due to particle detachment
Solution Approach 1:
The coating layer acts as an intermediary barrier between the Si-based active material particles and the electrolyte. This intermediate layer prevents direct contact that would cause particle detachment and electrical short-circuit, while still allowing lithium ion transport to maintain 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 second binder polymer effectively connects cracks in the Si-based negative electrode, preventing pulverization and improving the battery's durability and life characteristics by maintaining electrical contact and reducing internal short-circuits.
Implementation Method 1
a binder polymer present in the cracks formed in a Si-based negative electrode active material after activating, and the binder polymer connects the cracks
Data Source
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Figure 3
AI summary
The present disclosure relates to a negative electrode for a lithium secondary battery, including: a negative electrode current collector; and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, and including a Si-based negative electrode active material, a conductive material and a first binder polymer, wherein the Si-based negative electrode active material has cracks formed after activating, a second binder polymer is coated in the cracks, and the first binder polymer and the second binder polymer are heterogeneous. The present disclosure also relates to a lithium secondary battery including the negative electrode and a method for manufacturing the lithium secondary battery. The lithium secondary battery shows improved life characteristics.