Silicon-Carbon Anode Layering for Fast Charge and Expansion Buffering
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Solution Overview
Problem
Silicon-based active materials in anodes for secondary batteries have low lithium-ion diffusion rates and high-volume expansion rates, limiting their ability to achieve excellent quick charge characteristics and lifespan, despite their high discharge capacity.
Innovation Solution
A multilayer anode structure is implemented, with a first carbon-based active material having a high orientation index in the lower layer for high energy density and a low-orientation carbon-based active material in the upper layer for improved lithium-ion intercalation, along with varying silicon-based active material content and conductive material distribution to enhance quick charge and capacity characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active materials are applied to increase discharge capacity, then energy density is improved, but lithium-ion diffusion rate decreases and quick charge characteristics worsen
Solution Approach 1:
The anode is divided into multiple layers with different compositions and functions. The lower layer contains silicon-based active material for high capacity, while the upper layer contains carbon-based active material for fast lithium-ion diffusion. This segmentation allows each layer to specialize in one function, resolving the contradiction between capacity and diffusion rate.
Solution Approach 2:
Different regions of the anode are assigned different material compositions tailored to local requirements. The lower layer near the current collector uses silicon-based material optimized for capacity, while the upper layer uses carbon-based material optimized for quick charge. This local quality differentiation enables simultaneous optimization of both capacity and diffusion characteristics.
2Quantity of substance
If silicon-based active materials are applied to increase discharge capacity, then energy density is improved, but volume expansion rate increases and lifespan characteristics worsen
Solution Approach 1:
The anode is segmented into layers where the lower layer contains silicon-based material for high capacity while the upper carbon-based layer acts as a protective buffer. This segmentation isolates the volume expansion issue to the lower layer while the upper layer maintains structural stability, resolving the contradiction between capacity and compositional stability.
Solution Approach 2:
The carbon-based upper layer serves as a protective cushion that accommodates the volume expansion of the silicon-based lower layer during charging cycles. This beforehand cushioning prevents structural degradation and maintains lifespan characteristics while allowing the silicon-based material to deliver high capacity.
3Quantity of substance
If carbon-based active materials with high orientation index are used, then energy density is improved, but lithium-ion intercalation characteristics worsen
Solution Approach 1:
The anode uses local quality differentiation by placing high orientation index carbon-based material in the upper layer for fast lithium-ion intercalation, while the lower layer uses silicon-based material for high capacity. Each layer's material properties are optimized for its specific function, resolving the contradiction between intercalation rate and energy density.
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 multilayer anode structure achieves excellent quick charge, capacity, and resistance characteristics, enabling high energy density and prolonged lifespan while maintaining economic feasibility.
Implementation Method 1
a low-orientation carbon-based active material in the upper layer for improved lithium-ion intercalation
Data Source
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AI summary
An anode for a secondary battery is disclosed. In some implementations, the anode includes a current collector, a first anode mixture layer formed on at least one surface of the current collector, and a second anode mixture layer formed on the first anode mixture layer. The first anode mixture layer and the second anode mixture layer include a silicon-based active material, respectively. The first anode mixture layer includes a first carbon-based active material. The second anode mixture layer includes a second carbon-based active material. The first carbon-based active material has an OI value according to Equation 1, greater than or equal to an OI value of the second carbon-based active material. OI=I004/I110 In Equation 1, OI represents an orientation index according to an XRD measurement, I004 represents a peak intensity of (004) plane when the XRD measurement is performed on a carbon-based active material, and I110 represents a peak intensity of (110) plane when the XRD measurement is performed on the carbon-based active material.