Dual-Layer Silicon Oxide Anode for Volume-Stable Cycling
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Solution Overview
Problem
Existing negative electrode materials for secondary batteries, particularly those based on silicon, face challenges in maintaining charge/discharge efficiency and structural integrity due to high volume changes during cycling, limiting the energy density and cycle life of the battery.
Innovation Solution
A negative electrode with a two-layer structure comprising a first mixture layer of silicon oxide and needle-type carbon-based conductive material, and a second mixture layer of carbon material and sphere-type carbon-based conductive material, optimized in weight ratios and thickness, to enhance conductivity and adhesion, thereby stabilizing the electrode during charge/discharge cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as negative electrode active material to increase capacity, then theoretical capacity increases to 10 times more than carbon-based material, but charge/discharge efficiency decreases to about 80% and volume change rate increases to 300% or more causing conductive path disconnection
Solution Approach 1:
The invention uses a composite material consisting of silicon oxide particles coated with a carbon layer. The carbon coating maintains the high capacity of silicon oxide while preventing volume expansion and maintaining conductive paths. The composite structure combines the high capacity advantage of silicon with the structural stability of carbon.
Solution Approach 2:
The carbon layer acts as a flexible shell around the silicon oxide particles. This shell accommodates volume changes during charge/discharge cycles while maintaining the structural integrity and conductive pathways. The thin film structure allows lithium ion diffusion while preventing particle disintegration.
2Use of energy by moving object
If silicon-based material is used to achieve high capacity, then energy density increases, but volume change rate becomes 300% or more leading to conductive path disconnection during continuous charge/discharge
Solution Approach 1:
The carbon-coated silicon oxide composite maintains high energy density from the silicon oxide core while the carbon shell provides structural stability. The composite structure prevents the volume expansion issues that would otherwise lead to conductive path disconnection.
Solution Approach 2:
The carbon layer serves as an intermediary between the silicon oxide particles and the conductive network. It mediates the volume changes by providing a buffer zone that accommodates expansion and contraction while maintaining continuous conductive pathways to the current collector.
3Reliability
If carbon-based material is used as negative electrode material, then charge/discharge efficiency is about 92%, but theoretical capacity is limited to 372 mAh/g making it difficult to increase energy density
Solution Approach 1:
The invention creates a composite where silicon oxide provides high capacity (overcoming the 372 mAh/g limit of pure carbon) while the carbon coating maintains good charge/discharge efficiency. The composite achieves both high capacity and acceptable efficiency by combining materials with complementary properties.
Data Source
AI summary
The technology relates to a negative electrode for a secondary battery, and a secondary battery including same. The negative electrode comprises a composite material layer having a double-layer structure, but includes silicon oxide and carbon nanotubes in only one layer, such that it is possible to increase the capacity of a battery while preventing structural deterioration of the negative electrode due to changes in electrode volume during charging and discharging.