Silicon-Carbon Anode Material with Silicate Layer for Swelling Control
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Solution Overview
Problem
Silicon-based anode materials in lithium-ion batteries suffer from severe volume expansion during cycling, leading to material pulverization, breakage, and rapid capacity decay due to continuous SEI film breakdown and lithium ion consumption.
Innovation Solution
An anode material comprising a carbon matrix and a silicon-based active substance, with specific ratios of alkali and alkaline earth metal elements and oxygen, forms a silicate layer that enhances mechanical strength, reduces volume expansion, and minimizes gas production, thereby improving cycling stability and specific capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based anode materials are used to increase specific capacity, then energy density is improved, but volume expansion occurs during cycling leading to material pulverization and rapid capacity decay
Solution Approach 1:
The patent uses a composite material system consisting of silicon-based active substance, carbon matrix, and alkali metal/alkaline earth metal elements. The carbon matrix provides structural support while the silicon-based substance delivers high capacity. The alkali metal and alkaline earth metal elements form silicates that act as binders and structural stabilizers, preventing pulverization during volume expansion cycles.
Solution Approach 2:
The patent optimizes specific parameters including the mass content ratio of alkali metal to alkaline earth metal elements (A/B ratio) and the oxygen content (E), controlling them within specific ranges (1×10^-5 ≤ (B/A)×E ≤ 5×10^2). These parameter optimizations ensure the formation of appropriate silicate structures that accommodate volume changes while maintaining structural integrity and cycling stability.
2Quantity of substance
If silicon-based anode materials are used to achieve high capacity, then energy density is improved, but severe volume expansion leads to material breakage
Solution Approach 1:
The patent creates a composite structure where silicon-based active substance is embedded in a carbon matrix containing alkali metal and alkaline earth metal elements. The carbon matrix provides mechanical strength while the metal elements form silicates that act as binding agents, maintaining particle integrity during volume expansion and preventing material breakage.
Solution Approach 2:
The patent incorporates alkali metal and alkaline earth metal elements beforehand that form silicate structures during battery assembly. These silicates act as pre-formed cushioning structures that accommodate and buffer the volume expansion of silicon during lithium insertion, preventing mechanical stress concentration and material breakage before it occurs.
3Quantity of substance
If silicon-based anode materials are used to increase capacity, then energy density is improved, but continuous SEI film breakdown consumes lithium ions leading to rapid capacity decay
Solution Approach 1:
The patent controls the oxygen content (E) and the ratio of alkaline earth metal to alkali metal ((B/A)×E) within specific ranges to optimize the formation of silicon oxide and silicate structures. These optimized structures create more stable SEI films that reduce continuous breakdown and lithium ion consumption, thereby reducing substance loss while maintaining high capacity.
Solution Approach 2:
The patent uses a small amount of alkali metal and alkaline earth metal elements (in ppm ranges) that form sacrificial silicate structures. These silicates preferentially react to form stable SEI films, protecting the main silicon-based active substance from continuous SEI formation and lithium ion consumption, effectively sacrificing a small portion to preserve the bulk material.
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 anode material effectively alleviates volume expansion, reduces gas production, and enhances cycling stability while increasing specific capacity by balancing the content of alkali metal silicate, alkaline earth metal silicate, and silicon oxide, resulting in improved mechanical strength and structural stability.
Implementation Method 1
A silicate containing an alkaline earth metal element can enhance the mechanical strength of the silicon-based active substance
Implementation Method 2
A silicate containing an alkaline earth metal element can enhance the mechanical strength of the silicon-based active substance, and has good thermal and structural stability, which can effectively alleviate the volume expansion of the silicon-based active substance
Implementation Method 3
A suitable amount of silicon oxide on the surface of the silicon-based active substance can reduce the direct contact between the silicon-based active substance and an electrolyte, reduce the occurrence of side reactions, and reduce gas production
Data Source
AI summary
Provided are anode material, negative electrode plate and battery. The anode material includes a carbon matrix and a silicon-based active substance; the anode material contains an alkali metal element, an alkaline earth metal element, and an oxygen element, the alkali metal element includes Na and/or K, and the alkaline earth metal element includes Mg and/or Ca; a mass content of the alkali metal element is A ppm, a mass content of the alkaline earth metal element is B ppm, and a mass content of the oxygen element is E %; and the anode material satisfies the following relationship: 1×10−5≤(B/A)×E≤5×102. The anode material provided in the present application can enhance the cycling stability of the anode material while increasing the specific capacity of the anode material.