Layered Silicon Anode Structure for Fast Charging and Cycle Life
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Solution Overview
Problem
Lithium secondary batteries face challenges in improving energy density and rapid charging performance due to the low energy density of graphite anodes and the limitations of silicon materials, which experience volume expansion during charging and discharging, and the high cost and non-uniform distribution of single-walled carbon nanotubes.
Innovation Solution
An anode structure featuring a carbon-based first active material layer and a second active material layer with a silicon-based material and single-walled carbon nanotubes, where the silicon-based material and single-walled carbon nanotubes are concentrated on the surface, forming a weight ratio of 30:1 to 150:1, enhancing energy density and cycle life characteristics while reducing the amount of single-walled carbon nanotubes used.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon-based material is used to improve energy density, then energy density increases, but cycle life characteristics deteriorate due to volume expansion
Solution Approach 1:
The patent uses a composite structure combining silicon-based material with single-walled carbon nanotubes and conductive polymer. The silicon-based material (e.g., SiOx where 0≤x<2) provides high energy density, while the single-walled carbon nanotubes form a conductive network that maintains electrical connectivity despite silicon's volume expansion during charging-discharging cycles. The conductive polymer matrix binds these components together and provides additional conductivity, creating a composite anode that achieves both high energy density and stable cycle life.
2Reliability
If single-walled carbon nanotubes are added to improve cycle life, then cycle life improves, but manufacturing cost increases
Solution Approach 1:
The patent optimizes the weight ratio of single-walled carbon nanotubes to silicon-based material to be between 0.1:1 and 10:1, with a preferred range of 0.5:1 to 5:1. This parameter optimization ensures sufficient conductive network formation for maintaining cycle life while minimizing the amount of expensive single-walled carbon nanotubes required, thus balancing performance with manufacturing cost.
Solution Approach 2:
The conductive polymer acts as an intermediary material that binds the silicon-based material particles and single-walled carbon nanotubes together. This polymer matrix provides a continuous conductive pathway alternative to relying solely on the nanotube network, reducing the required amount of expensive single-walled carbon nanotubes while maintaining electrical conductivity and cycle life characteristics.
3Reliability
If single-walled carbon nanotubes are mixed with silicon material, then cycle life improves, but rapid charging performance is limited due to non-uniform distribution
Solution Approach 1:
The patent creates a heterogeneous structure where single-walled carbon nanotubes are concentrated at the interfaces and boundaries between silicon-based material particles, forming a percolating conductive network. The conductive polymer fills the internal spaces and provides conductivity throughout the bulk. This local quality differentiation ensures that the nanotubes are strategically positioned where they are most needed (at particle interfaces) rather than uniformly distributed, improving both cycle life and rapid charging performance.
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
This configuration improves energy density, cycle life, and rapid charging performance by alleviating volume expansion issues and reducing costs, maintaining conductive paths, and increasing lithium-ion reaction sites, thus enhancing the overall performance and manufacturing economics of lithium secondary batteries.
Implementation Method 1
maintaining conductive paths
Implementation Method 2
active materials into which lithium ions may be inserted and extracted
Data Source
AI summary
The present disclosure provides an anode including an anode current collector, a first anode active material layer formed on at least one side of the anode current collector and comprising a carbon-based material, and a second anode active material layer formed on the first anode active material layer and comprising a silicon-based material and single-walled carbon nanotubes, wherein a weight ratio of the silicon-based material and the single-walled carbon nanotubes is 30:1 to 150:1, and a secondary battery including the same.