Silicon-Silicon Oxide Composite Negative Electrode for Li-Ion Batteries
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Solution Overview
Problem
Current lithium ion secondary batteries, particularly their negative electrode materials, face challenges with low first efficiency and cycle durability, which are critical for high-capacity and long-lasting electric vehicle applications.
Innovation Solution
A silicon-silicon oxide composite with a carbon coating, doped with lithium, where the ratio of SiC to Si peak intensities is controlled to ensure minimal SiC formation at the interface, enhancing electronic conductivity and cycle durability, and using lithium hydride or lithium aluminum hydride as dopants to stabilize lithium within the composite.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon oxide is used as negative electrode material to increase theoretical capacity, then capacity is improved, but first efficiency deteriorates due to low first efficiency
Solution Approach 1:
Lithium compounds are generated in advance by reacting silicon oxide with lithium metal or lithium compounds before the first charge, so that the harmful side reaction occurs beforehand and does not reduce the first efficiency of the actual battery operation
Solution Approach 2:
The compositional ratio of silicon oxide is optimized with silicon content of 20-80 mass% to balance capacity and first efficiency, and lithium compound content is controlled at 1-50 mass% to achieve desired performance
2Quantity of substance
If silicon oxide is used as negative electrode material to increase theoretical capacity, then capacity is improved, but cycle durability deteriorates due to low electronic conductivity
Solution Approach 1:
Silicon oxide is combined with conductive materials such as carbon, graphite, or metal particles to form a composite structure that provides both high capacity and sufficient electronic conductivity for good cycle durability
Solution Approach 2:
Silicon content is optimized at 20-80 mass% to ensure adequate electronic conductivity while maintaining high capacity, balancing both cycle durability and performance
3Reliability
If lithium compounds are generated in advance to improve first efficiency, then first efficiency is improved, but SiC formation increases at the interface
Solution Approach 1:
Heating temperature is precisely controlled at 400-800°C to promote lithium compound formation while suppressing SiC generation, and heating time is optimized at 1-24 hours to achieve complete reaction without excessive SiC formation
Solution Approach 2:
The reaction is conducted in an inert atmosphere such as nitrogen or argon to prevent unwanted oxidation and control the reaction environment to favor lithium compound formation over SiC formation
4Reliability
If heating temperature is increased to promote lithium compound formation, then first efficiency is improved, but SiC generation increases
Solution Approach 1:
Heating temperature is optimized at 400-800°C to achieve the optimal balance between promoting lithium compound formation (improving first efficiency) and suppressing SiC generation (reducing harmful effects)
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 approach results in improved first efficiency and cycle durability, enabling higher capacity and longer battery life, suitable for electric vehicle applications, while maintaining high productivity and safety.
Implementation Method 1
using lithium hydride or lithium aluminum hydride as dopants to stabilize lithium within the composite
Implementation Method 2
A silicon-silicon oxide composite with a carbon coating, doped with lithium, where the ratio of SiC to Si peak intensities is controlled to ensure minimal SiC formation at the interface, enhancing electronic conductivity
Data Source
AI summary
The present invention is a negative electrode material for a secondary battery with a non-aqueous electrolyte comprising at least a silicon-silicon oxide composite and a carbon coating formed on a surface of the silicon-silicon oxide composite, wherein at least the silicon-silicon oxide composite is doped with lithium, and a ratio I(SiC)/I(Si) of a peak intensity I(SiC) attributable to SiC of 2θ=35.8±0.2° to a peak intensity I(Si) attributable to Si of 2θ=28.4±0.2° satisfies a relation of I(SiC)/I(Si)≤0.03, when x-ray diffraction using Cu-Kα ray. As a result, there is provided a negative electrode material for a secondary battery with a non-aqueous electrolyte that is superior in first efficiency and cycle durability to a conventional negative electrode material.