SiOC Anode Material Balancing Capacity and Cycle Retention
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Solution Overview
Problem
Existing silicon-containing active materials for secondary batteries face challenges in maintaining capacity retention and battery lifetime, with a tendency for decreased retention ratio with increasing silicon content, and insufficient suppression of large volume changes during charging and discharging.
Innovation Solution
A secondary battery material composed of silicon (Si), oxygen (O), and carbon (C), with specific content ratios of O to Si (0.1≤x≤2) and C to Si (0.3≤y≤11), and a negative electrode active material with a carbon coat and a Si nanoparticle, where the carbon coat has a specific porosity and the Si nanoparticle is dispersed in a matrix of silicon oxycarbide and carbonaceous phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon content is increased to improve charge and discharge capacity, then capacity is improved, but capacity retention rate deteriorates
Solution Approach 1:
The invention uses a composite material consisting of silicon oxycarbide (SiOC) formed by reacting silicon oxide with carbon. This composite structure combines the high capacity benefits of silicon with the stability of carbon and silicon oxide, achieving both high charge/discharge capacity and excellent capacity retention rate. The SiOC compound creates a stable matrix that prevents silicon particle aggregation and maintains structural integrity during cycling.
Solution Approach 2:
The invention changes the chemical composition parameters by controlling the carbon content in the silicon oxide matrix. By adjusting the carbon addition amount and reaction conditions, the SiOC compound achieves optimal properties where carbon acts as a buffer to accommodate volume expansion while maintaining electrical conductivity and structural stability, thus improving both capacity and retention.
2Quantity of substance
If silicon content is increased to improve charge and discharge capacity, then capacity is improved, but battery lifetime deteriorates
Solution Approach 1:
The silicon oxycarbide composite material provides a stable chemical structure that resists degradation during long-term cycling. The carbon-containing matrix protects the silicon from oxidation and other chemical reactions that would otherwise reduce battery lifetime, while maintaining the high capacity characteristics of silicon.
Solution Approach 2:
The invention uses readily available silicon oxide as a starting material that can be easily converted to SiOC. This approach replaces expensive and complex silicon structures with a simpler, more stable SiOC compound that naturally provides long-term stability without requiring additional protective coatings or complex electrode designs.
3Reliability
If carbon coat is applied to improve electrical conductivity, then electrical conductivity is improved, but volume expansion suppression becomes insufficient
Solution Approach 1:
The invention merges multiple functions into a single SiOC matrix structure. The carbon in the SiOC compound simultaneously provides electrical conductivity like a carbon coating and volume expansion buffering like a protective matrix. This unified structure eliminates the need for separate carbon coatings and effectively manages volume changes during lithium insertion/extraction.
Solution Approach 2:
The SiOC composite material inherently combines the conductive properties of carbon with the structural stability of silicon oxide. This integrated composite provides both excellent electrical conductivity and effective volume expansion suppression without requiring additional carbon coating layers, solving both requirements simultaneously.
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 proposed solution achieves high charge and discharge capacity, initial efficiency, and capacity retention rate, providing an excellent balance of these characteristics in secondary batteries.
Implementation Method 1
disruption of the negative electrode material due to a large volume change of a silicon compound through charging and discharging is suppressed by providing a void between the silicon compound and the carbon coat
Implementation Method 2
The negative electrode active material particle described in PTL 6 contains a silicon compound and is said to have excellent electrical conductivity by coating at least a part of the surface of the silicon compound with a carbon coat
Implementation Method 3
the impregnating ability of the electrolytic solution of the battery is improved by adjusting the specific surface area of the carbon coat
Data Source
AI summary
[Object] To provide a secondary battery material that is used in a lithium ion battery, a negative electrode active material including the secondary battery material, and a secondary battery including the negative electrode active material. The secondary battery material gives a secondary battery having high charge and discharge capacity, initial efficiency, and capacity retention rate as a whole and having an excellent balance of these characteristics.[Solution]A secondary battery material contains Si (silicon), O (oxygen), and C (carbon), and the content ratio x of O to Si satisfies 0.1≤x≤2, and the content ratio y of C to Si satisfies 0.3≤y≤11.