Silicon-Silicon Oxide-Lithium Composite for Stable Battery Electrodes
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Solution Overview
Problem
Existing negative electrode materials for lithium ion secondary cells, particularly those based on silicon and silicon oxide, suffer from low initial efficiency and inadequate cycle performance due to volume changes during lithium occlusion and release, leading to reduced conductivity and capacity degradation.
Innovation Solution
A silicon-silicon oxide-lithium composite is developed by doping silicon oxide with lithium and coating the composite with carbon, where silicon grains are dispersed in silicon oxide, enhancing initial efficiency and cycle performance by stabilizing conductivity and preventing volume changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon oxide is used as negative electrode material to increase charge/discharge capacity, then capacity is improved, but initial efficiency remains low and cycle performance deteriorates
Solution Approach 1:
The patent uses a composite material consisting of silicon oxide particles coated with a carbon-containing layer. This composite structure combines the high capacity advantage of silicon oxide with the conductivity and structural stability of carbon, resolving the contradiction between capacity and cycle performance
Solution Approach 2:
The patent changes the chemical composition and structural parameters of the coating layer by controlling the carbonization process. By adjusting carbon content, coating thickness, and structural density, the material achieves both high initial efficiency and improved cycle performance while maintaining high capacity
2Reliability
If carbon coating is applied to silicon oxide particles to improve conductivity, then conductivity is improved, but uniform coating is difficult to achieve and cycle performance remains insufficient
Solution Approach 1:
The patent uses a carbon-containing compound as an intermediary material that uniformly coats the silicon oxide particles. This intermediary layer serves as a precursor that distributes evenly and then converts to a conductive carbon coating, achieving both uniform coverage and improved conductivity
Solution Approach 2:
The patent employs phase transition during carbonization, where the carbon-containing precursor transforms into a solid carbon coating layer. This phase change process enables uniform deposition and formation of a stable, conductive layer on the silicon oxide particles
3Quantity of substance
If silicon-based negative electrode material is used to increase energy density, then energy density is improved, but volume expansion and contraction occur during lithium ion adsorption and desorption, leading to loss of cycle performance
Solution Approach 1:
The patent uses a carbon-containing coating layer as a flexible shell around the silicon oxide particles. This shell accommodates volume changes during lithium ion adsorption and desorption, preventing structural degradation while maintaining the high energy density of the silicon-based core
Solution Approach 2:
The carbon-containing layer acts as a pre-formed protective cushion that absorbs and mitigates the mechanical stress of volume expansion and contraction. This beforehand cushioning prevents direct contact between the silicon oxide and electrolyte, maintaining structural integrity over multiple cycles
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 silicon-silicon oxide-lithium composite achieves high initial efficiency and improved cycle performance by maintaining stable conductivity and preventing capacity drops, outperforming previous materials in lithium ion secondary cells.
Implementation Method 1
doping silicon oxide with lithium
Implementation Method 2
coating of silicon oxide particles with a carbon layer by chemical vapor deposition
Implementation Method 3
CVD treatment of silicon oxide powder to provide a carbon coat
Data Source
AI summary
A silicon-silicon oxide-lithium composite comprises a silicon-silicon oxide composite having such a structure that silicon grains having a size of 0.5-50 nm are dispersed in silicon oxide, the silicon-silicon oxide composite being doped with lithium. Using the silicon-silicon oxide-lithium composite as a negative electrode material, a lithium ion secondary cell having a high initial efficiency and improved cycle performance can be constructed.