Silicon Composite Anode Double Coating for Volume Expansion Control
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Solution Overview
Problem
Silicon-based anode materials face severe volume expansion and contraction during lithium intercalation and deintercalation, leading to structural damage, electrolyte consumption, and poor cycle performance due to high surface area and side reactions.
Innovation Solution
A silicon-based composite anode material with a double-layer coating structure, comprising a quinone-aldehyde covalent organic framework material and an ion conductor layer, which absorbs mechanical stress and maintains structural stability, reducing volume expansion and preventing electrolyte contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as anode material to achieve high theoretical capacity (4200 mAh/g), then energy density is improved, but severe volume expansion (0-300%) and structure pulverization occur during lithium intercalation and deintercalation
Solution Approach 1:
The patent applies a flexible polymer coating layer on the silicon-based anode material surface. This polymer layer acts as a flexible shell that can accommodate the volume expansion and contraction of silicon during lithium intercalation and deintercalation, preventing structure pulverization while maintaining integrity throughout charge-discharge cycles.
Solution Approach 2:
The patent creates a composite anode material by combining silicon-based material with a polymer coating layer. This composite structure integrates the high capacity advantage of silicon with the structural stability and flexibility of the polymer material, resolving the contradiction between capacity and stability.
2Stability of the object's composition
If nanocrystallization is used to alleviate silicon volume expansion effect, then volume expansion is reduced, but surface area increases causing high probability of conglomeration, low dispersion, large contact area with electrolyte, fast electrolyte consumption
Solution Approach 1:
The polymer coating layer serves as a flexible shell that covers the nanocrystalline silicon surface, effectively reducing the active surface area exposed to the electrolyte while accommodating volume changes. This prevents direct contact between the high-surface-area nanocrystalline silicon and the electrolyte, reducing side reactions and electrolyte consumption.
3Strength
If soft coating (such as carbon coating) is applied on nano-silicon anode material surface, then toughness is improved, but pores of the soft coating cannot actually alleviate side reaction between silicon and electrolyte
Solution Approach 1:
The patent uses a polymer-based flexible coating layer that provides both mechanical toughness and effective barrier properties. Unlike porous soft coatings, this polymer film forms a dense, continuous layer that physically isolates the silicon from the electrolyte, preventing side reactions while maintaining flexibility to accommodate volume changes.
4Stability of the object's composition
If hard coating is applied on nano-silicon anode material surface, then structural stability is improved, but hard coating is brittle and likely to break and fall off during expansion and contraction
Solution Approach 1:
The patent employs a flexible polymer coating layer that maintains structural stability through its elastic properties rather than brittleness. This flexible shell can dynamically adapt to the expansion and contraction of the underlying silicon, maintaining coating integrity and preventing breakage or delamination that would occur with rigid hard coatings.
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 composite anode material enhances electrical and ionic conductivity, improves electron and ion conduction, and extends cycle life by stabilizing the structure and reducing side reactions, resulting in higher energy density and improved cycle performance.
Implementation Method 1
With superb toughness and ordered pore structure, the quinone-aldehyde covalent organic framework material of the first coating layer can effectively absorb mechanical stress generated by expansion of the silicon-based material core
Implementation Method 2
The conducting ionic material layer can further effectively prevent the electrolyte from in contact with the silicon-based material core to cause side reactions
Implementation Method 3
the coating layer includes a first coating layer and a second coating layer coating the first coating layer... have high electrical conductivity and ionic conductivity, thereby effectively improving electron conduction and ion conduction effects of the coating layer
Data Source
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Figure 3
AI summary
Embodiments of the present invention provide a silicon-based composite anode material, including a silicon-based material core and a coating layer coated on a surface of the silicon-based material core, where the coating layer includes a first coating layer disposed on the surface of the silicon-based material core and a second coating layer disposed on a surface of the first coating layer, the first coating layer includes a two-dimensional quinone-aldehyde covalent organic framework material, and the second coating layer includes a fast ion conductor material. With super toughness and an ordered pore structure, the first coating layer can effectively absorb mechanical stress generated by expansion of the silicon-based material core and ensure integrity of the coating layer, and has high electrical conductivity and ionic conductivity, thereby effectively enhancing effects of electron conduction and ion conduction of the coating layer. The second coating layer is relatively rigid, can maintain structural stability of the entire material during silicon expansion and contraction, and effectively alleviates volume expansion. The embodiments of the present invention further provide a method for preparing the silicon-based composite anode material and an energy storage device that includes the silicon-based composite anode material.