Silicon Anode Coating for Volume-Stable High-ICE Capacity
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Solution Overview
Problem
Silicon anode materials for secondary batteries face challenges due to severe volume expansion leading to material degradation and low initial Coulombic efficiency, which limits their application in high-energy density applications.
Innovation Solution
A silicon-based anode material with a nano silicon core and a lithium-containing silicon oxide core coated with a polymer layer featuring —Si—O—Si— bonds, which inhibits gas production and enhances processing performance by forming a stable aqueous slurry and improving initial Coulombic efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon anode materials are used to achieve high capacity per gram, then the theoretical capacity increases to 4200 mAh/g, but severe volume expansion (>300%) occurs during charging and discharging
Solution Approach 1:
The silicon-based core is divided into nano silicon particles (grain size ≤20 nm) dispersed within a lithium-containing silicon oxide matrix. This segmentation prevents severe volume expansion by distributing the expansion stress across many small particles rather than a bulk silicon structure, while maintaining high capacity through the large surface area of nano particles.
Solution Approach 2:
The invention uses a composite structure combining nano silicon with lithium-containing silicon oxide (Li2SiO3 or Li2Si2O5). The silicon oxide matrix provides structural stability and accommodates volume changes, while the nano silicon provides high capacity. This composite approach resolves the contradiction between high capacity and volume stability.
2Quantity of substance
If silicon-based core with nano silicon is used to achieve high reversible capacity, then capacity increases, but gas production occurs during homogenization process
Solution Approach 1:
A polymer layer containing —Si—O—Si— bonds is introduced as an intermediary coating on the silicon-based core. This coating layer acts as a barrier that prevents direct contact between nano silicon and water during homogenization, thereby inhibiting gas production while allowing lithium ion transport. The polymer layer serves as a mediator that protects the reactive silicon surface.
3Quantity of substance
If conventional silicon anode materials are used, then high capacity is achieved, but initial Coulombic efficiency is low due to continuous SEI layer rupture and regeneration
Solution Approach 1:
The silicon-based core is pre-lithiated by incorporating lithium-containing silicon oxide before battery assembly. This preliminary lithium incorporation ensures that the SEI layer forms with adequate lithium reserves, preventing continuous rupture and regeneration during initial cycles. The pre-lithiation action addresses the Coulombic efficiency problem before the battery enters service.
Solution Approach 2:
A thin polymer coating layer with —Si—O—Si— bonds is applied to the silicon-based core. This flexible thin film accommodates volume changes during cycling while maintaining a stable interface, preventing SEI layer rupture. The coating acts as a protective shell that maintains structural integrity during expansion and contraction.
4Ease of manufacture
If polymer coating is applied to inhibit gas production, then processing performance improves, but coating complexity increases
Solution Approach 1:
The polymer coating is formed by controlling the pH of the aqueous slurry to be alkaline (pH 9-11), which promotes the formation of —Si—O—Si— bonds in the polymer layer. This parameter control (pH adjustment) enables simple one-step coating process that forms the protective layer during normal slurry preparation, avoiding complex multi-step coating procedures.
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-based anode material achieves high reversible capacity and improved initial Coulombic efficiency while maintaining stability during homogenization, effectively preventing material degradation and enhancing processing performance.
Implementation Method 1
the coating layer at least including a polymer layer with —Si—O—Si— bonds, which is insoluble in water, thereby preventing the reaction of nano silicon in the silicon-based core with water to produce gas
Implementation Method 2
the polymer is formed by condensing a silane-modified polymer
Data Source
AI summary
A silicon-based anode material and a preparation method thereof are provided. The silicon-based anode material includes a silicon-based core and a coating layer, the silicon-based core includes nano silicon and a lithium-containing silicon oxide, and the coating layer at least includes a polymer layer with —Si—O—Si— bonds. The preparation method of a silicon-based anode material includes (I) preparing a silicon-based core; and (II) coating a polymer layer. The silicon-based anode material includes high initial Coulombic efficiency and initial lithium intercalation capacity. The polymer layer with —Si—O—Si— bonds in the coating layer is insoluble in water, which avoid problems such as slurry sedimentation and poor coating performance, making the silicon-based anode material have good processing performance.