Silicon Anode Composition Using SWCNT Networks for Cycle Stability
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Solution Overview
Problem
Silicon-based negative electrode active materials in lithium secondary batteries face challenges due to volumetric expansion and contraction during charging and discharging, leading to electrical disconnection and rapid degradation, limiting their lifetime and energy density.
Innovation Solution
A negative electrode comprising a silicon-based active material, a carbon-based active material, and a specific amount of single-walled carbon nanotube aggregates, which form a stable conductive network to maintain electrical connection despite volume changes, improving the battery's lifetime characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active materials are used to achieve high capacity and high energy density, then the battery capacity increases significantly, but volumetric expansion occurs during charging and discharging causing electrical disconnection and rapid degradation of lifetime characteristics
Solution Approach 1:
Single-walled carbon nanotube aggregates serve as an intermediary conductive network between silicon-based active material particles. The nanotubes maintain electrical connection during volumetric expansion and contraction, preventing electrical disconnection while preserving the high capacity benefits of silicon-based materials.
Solution Approach 2:
The negative electrode uses a composite structure combining silicon-based active materials with single-walled carbon nanotube aggregates. This composite approach leverages the high capacity of silicon while the carbon nanotubes provide structural stability and continuous electrical conductivity throughout charge-discharge cycles.
2Ease of manufacture
If conventional conductive materials are used in the negative electrode, then the electrode structure is simple and easy to manufacture, but electrical connection is lost when active material particles expand and contract
Solution Approach 1:
Single-walled carbon nanotube aggregates act as an intermediary conductive phase that bridges active material particles. Unlike conventional conductive materials that fail during volume changes, the nanotube aggregates maintain electrical pathways through their flexible, high-aspect-ratio structure, ensuring stable conductivity without complicating manufacturing.
3Reliability
If the amount of single-walled carbon nanotube aggregates is increased to improve electrical connection, then conductivity may improve, but manufacturing cost and electrode complexity increase
Solution Approach 1:
The invention optimizes the content parameter of single-walled carbon nanotube aggregates to a specific range (0.01-0.1 parts by weight per 100 parts by weight of silicon-based active material). This parameter optimization achieves sufficient electrical connection stability while minimizing electrode complexity and manufacturing cost, avoiding both deficiency and excess.
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 use of single-walled carbon nanotube aggregates in the negative electrode active material layer enhances the electrical connection and cycle stability, significantly improving the lifetime and capacity retention of the battery while preventing efficiency degradation.
Implementation Method 1
single-walled carbon nanotube aggregates, which form a stable conductive network to maintain electrical connection despite volume changes
Data Source
AI summary
The present invention provides a negative electrode which comprises: a negative electrode current collector; and a negative electrode active material layer formed on the negative electrode current collector and comprising a negative electrode active material containing a silicon-based active material and a carbon-based active material, a binder, and single-walled carbon nanotube aggregates. The single-walled carbon nanotube aggregates are comprised at 0.05 parts by weight to 0.37 parts by weight based on 100 parts by weight of the silicon-based active material in the negative electrode active material layer.