Carbon-Coated Silicon Oxide Anode for Stable Volume Change
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Solution Overview
Problem
Conventional negative electrode active materials for non-aqueous electrolyte secondary batteries face issues with large volume expansion and contraction during lithium intercalation, leading to deteriorated lifetime characteristics and capacity retention, particularly in silicon-based materials like Si, Sn, and Al, which also suffer from poor conductivity and irreversible reactions with lithium.
Innovation Solution
A silicon oxide composite is formed by reacting silicon, silicon dioxide, and magnesium through a gas phase reaction, with a carbon coating applied to the surface, creating a stable structure that minimizes volume change and enhances conductivity, using a specific ratio of magnesium silicate to silicon oxide to improve cycle characteristics and initial efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based materials are used as negative electrode active material to achieve high capacity, then discharge capacity is improved, but volume expansion reaches about 400% causing deterioration of lifetime characteristics
Solution Approach 1:
The patent applies the nesting principle by placing silicon microcrystals inside a silicon dioxide matrix, creating a core-shell structure where the inner silicon provides high capacity while the outer silicon dioxide matrix constrains volume expansion. This nested configuration allows the high-capacity silicon to be protected by the stable silicon dioxide shell, resolving the contradiction between achieving high discharge capacity and maintaining lifetime characteristics.
Solution Approach 2:
The patent creates a composite material system combining silicon microcrystals with silicon dioxide matrix, forming a new material structure that integrates the advantages of both components. The silicon provides high capacity while the silicon dioxide provides structural stability and controls volume expansion, together achieving both high discharge capacity and improved lifetime characteristics through material composition rather than using pure silicon.
2Reliability
If silicon oxide is used to improve volumetric expansion ratio and lifetime characteristics, then capacity retention rate is improved, but lithium oxides are produced by irreversible reaction with lithium during initial charging
Solution Approach 1:
The patent applies local quality by creating a specific ratio range of silicon to silicon dioxide (0.1 to 0.5 by weight), where the local composition is optimized to balance irreversible reaction and capacity retention. The silicon-rich local regions provide capacity while the silicon dioxide-rich local regions control volume expansion and reduce irreversible reactions, achieving both improved capacity retention and acceptable initial charging efficiency through spatial composition control.
Solution Approach 2:
The patent changes the compositional parameter by controlling the silicon to silicon dioxide weight ratio within a specific range (0.1 to 0.5), and controlling silicon crystal size within 2 to 100 nm. By optimizing these parameters, the patent reduces the extent of irreversible reactions while maintaining capacity retention, transforming the initial charging efficiency problem through parameter optimization.
3Ease of manufacture
If conventional heating method is used to prepare silicon-silicon oxide composite, then manufacturing is simplified, but silicon crystal size is rapidly grown and magnesium is nonuniformly distributed
Solution Approach 1:
The patent replaces the conventional thermal field-based heating method with a chemical vapor deposition process using silane gas and magnesium vapor. This substitution of the physical field (thermal) with a chemical field (vapor phase reaction) enables more uniform magnesium distribution and controlled silicon crystal size while maintaining manufacturing feasibility through a single-step process that combines mixing, reaction, and coating.
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 solution results in improved charging and discharging capacities, increased cycle stability, and enhanced conductivity, maintaining high capacity retention rates and efficiency by stabilizing the electrode against volume changes during lithium intercalation and deintercalation.
Implementation Method 1
reacting silicon, silicon dioxide, and magnesium through a gas phase reaction
Implementation Method 2
reacting silicon, silicon dioxide, and magnesium through a gas phase reaction to prepare a silicon oxide composite
Implementation Method 3
coating carbon on the surface of the silicon oxide composite
Implementation Method 4
coating carbon on the surface of the silicon oxide composite
Implementation Method 5
intercalation or deintercalation of lithium
Implementation Method 6
large volume expansion or contraction in the process of performing an alloying or non-alloying reaction with Li
Data Source
AI summary
The present disclosure relates to a negative electrode active material for non-aqueous electrolyte secondary battery and a manufacturing method thereof and, more specifically to, a negative electrode active material for non-aqueous electrolyte secondary battery, the negative electrode active material which not only improves conductivity by reacting, silicon, silicon dioxide and magnesium through a gas phase reaction to produce a reaction product and coating carbon on the surface of the reaction product so as to give conductivity to the reaction product, but also exhibits an effect of greatly improving lifetime characteristics and capacity characteristics by showing a structure that is stable in a volume change caused by intercalation or deintercalation of lithium, and a manufacturing method thereof.