Silicon Oxide Composite Anode for Lithium Battery Cycle Life
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Solution Overview
Problem
Conventional negative active materials for rechargeable lithium batteries, such as graphite, silicon, or silicone compounds, face issues with cycle-life and high-rate charge/discharge characteristics due to structural instability and poor utilization of silicon compounds when alloyed with lithium, leading to inefficient energy storage and battery degradation.
Innovation Solution
A negative active material comprising a silicon oxide (SiOX) composite with x≦1.5, doped with elements like B, P, Li, Ge, Al, and V, combined with a carbonaceous material, either coated or mixed, to enhance structural stability and lithium diffusion rates, thereby improving cycle-life and charge/discharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a simple mixture of graphite and silicone compound powder is used, then the preparation process is simple, but the silicone compound is released from graphite during charge/discharge cycles due to incomplete contact and low electro-conductivity, deteriorating cycle characteristics
Solution Approach 1:
The patent combines graphite and silicone compound into a composite structure where pulverized silicone compound is chemically fixed on graphite surface through silane coupling agent treatment, creating a merged material that maintains both components' advantages while preventing separation during cycling
Solution Approach 2:
The invention creates a composite material system consisting of graphite base material, silane coupling agent linkage, and silicone compound coating, forming a multi-component composite that addresses the limitations of simple physical mixing by achieving chemical bonding between components
2Reliability
If pulverized silicone compound is chemically fixed on graphite surface by silane coupling agent, then the material works as negative active material, but the silicone compound expands when alloyed with lithium causing silane linkage to break and release silicone compound, deteriorating cycle characteristics
Solution Approach 1:
The patent modifies the chemical composition parameters of the silane coupling agent system by introducing specific crosslinking agents and adjusting the ratio of silane compounds, thereby changing the physical and chemical properties of the coating layer to accommodate lithium alloying expansion while maintaining structural integrity
Solution Approach 2:
The invention creates different functional zones within the coating layer: a flexible inner layer that accommodates expansion and a more stable outer layer that maintains structural integrity, with each zone having locally optimized properties to address specific requirements of the charge/discharge process
3Reliability
If silane coupling agent is used to fix silicone compound on graphite, then negative active material is formed, but uniform treatment is difficult to achieve resulting in inconsistent quality of negative electrode material
Solution Approach 1:
The patent introduces a liquid carrier medium as an intermediary that facilitates uniform distribution of silane coupling agent and silicone compound throughout the graphite mixture, ensuring consistent coating coverage and chemical bonding across all graphite particles, thereby achieving uniform treatment and consistent product quality
4Reliability
If graphite is used as negative active material, then good cycle characteristics are achieved, but the theoretical capacity is limited to 372 mAh/g and higher capacity materials are desired
Solution Approach 1:
The patent creates a composite negative active material combining graphite (providing structural stability and good cycle characteristics) with silicone compound (providing higher theoretical capacity), where the silane coupling agent chemically bonds these two materials to form an integrated composite that achieves both durability and high capacity
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 oxide composite with added elements achieves an amorphorization degree of 50% or more and a lithium diffusion rate of 10−8 cm2/sec or higher, significantly enhancing the cycle-life and high-rate charge/discharge characteristics of rechargeable lithium batteries.
Implementation Method 1
the silicone compound expands when it is alloyed with the lithium upon repeating the charge and discharge cycles
Implementation Method 2
a lithium diffusion rate of 10−8 cm2/sec or higher
Data Source
AI summary
The present invention relates to a negative active material for a rechargeable lithium battery, which includes a silicon-based composite having a silicon oxide of the form SiOX where x≦1.5 and at least one element selected from the group consisting of B, P, Li, Ge, Al, and V, and a carbonaceous material. The negative active material of the present invention can improve the cycle-life and high-rate charge/discharge characteristics of a rechargeable lithium battery.