Silicon Anode Layer Gradient for Capacity and Resistance Balance
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Solution Overview
Problem
Existing silicon-based anodes for lithium secondary batteries face challenges with high electrical resistance and limited capacity, particularly when using multi-layered structures, which do not adequately address the expansion and contraction during charging and discharging, leading to reduced electrode stability and battery life-span.
Innovation Solution
A multi-layered anode active material layer structure is implemented, with a first and second anode active material layer containing silicon-based materials, where the second layer has a higher silicon content and includes a specific binder to manage expansion and contraction, enhancing capacity and reducing resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based anode active material is used to increase capacity, then the battery capacity is improved, but the electrical resistance increases
Solution Approach 1:
The anode active material layer is divided into multiple layers with different silicon-based material contents. The first layer has a lower silicon-based material content while subsequent layers have progressively higher contents, creating a gradient structure that balances capacity and electrical resistance throughout the electrode thickness
Solution Approach 2:
Different regions of the anode active material layer have different silicon-based material contents optimized for their specific functions. The deeper layers (higher silicon content) contribute more to capacity while the shallower layers (lower silicon content) maintain better electrical conductivity, with each layer's composition tailored to its position and role in the electrode
2Reliability
If multi-layered anode structure is implemented to balance capacity and resistance, then electrical property is improved, but the expansion and contraction during charging and discharging is not adequately addressed, reducing electrode stability
Solution Approach 1:
A buffer layer is introduced between the anode active material layer and the current collector to preemptively accommodate and cushion the expansion and contraction of the silicon-based material during charging and discharging cycles. This buffer layer prevents mechanical stress from directly affecting the current collector and maintains electrode structural integrity
Solution Approach 2:
The anode is constructed as a composite structure combining multiple materials with different properties: silicon-based active materials for capacity, conductive materials for electrical conductivity, binders for structural cohesion, and a buffer layer for mechanical stress management. This composite approach addresses multiple requirements simultaneously
Data Source
Figure 1~2
Figure 3
AI summary
An anode for a lithium secondary battery includes an anode current collector, and an anode active material layer including a first anode active material layer and a second anode active material layer sequentially disposed on a surface of the anode current collector. Each of the first anode active material layer and the second anode active material layer includes a silicon-based active material. A ratio of a content of the silicon-based active material in the second anode active material layer relative to a content of the silicon-based active material in the first anode active material layer among a total content of the silicon-based active material included in the anode active material layer is 1.25 or more, and less than 5.