Multilayer Silicon Anode Structure for Volume Expansion Control
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Solution Overview
Problem
Lithium ion batteries face challenges with silicon anode materials due to large volume changes during lithiation/de-lithiation, leading to fragmentation, pulverization, and increased Solid Electrolyte Interface (SEI) film growth, which reduces battery capacity and cycle life, and existing silicon-based anode materials are costly and inefficient in large-scale applications.
Innovation Solution
A silicon-based anode material with a multilayer structure comprising a low-density first silicon material layer, a high-density second silicon material layer, a buffer layer, and a coating layer, sequentially arranged to manage volume expansion, stabilize the electrolyte interface, and improve conductivity and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon material is used as anode material to increase theoretical capacity, then energy density is improved, but volume expansion during lithiation/de-lithiation causes fragmentation and pulverization
Solution Approach 1:
The silicon-based anode material is divided into multiple layers with different densities (first silicon material layer with lower density, second silicon material layer with higher density). This segmentation allows each layer to handle volume expansion differently, with the lower density layer providing expansion space and the higher density layer maintaining structural integrity, thereby resolving the contradiction between high capacity and cycle stability
Solution Approach 2:
The invention uses a composite structure combining silicon-based materials with different densities in a layered configuration. This composite approach leverages the advantages of both low-density silicon (high capacity) and high-density silicon (structural stability), achieving both high energy density and long cycle life simultaneously
2Reliability
If silicon nanomaterial is used to reduce particle size and maintain stability during lithiation, then volume expansion effect is relieved, but preparation cost increases and manufacturing becomes cumbersome
Solution Approach 1:
Instead of using nanoscale silicon particles which are difficult to manufacture, the invention changes the parameter of silicon particle size to microscale while compensating for stability issues through the layered density structure. The lower density first layer provides expansion buffer that maintains stability without requiring nanoscale dimensions, thus simplifying manufacturing while achieving structural stability
3Quantity of substance
If silicon nanomaterial is used to decrease specific surface area, then electrolyte solution consumption is reduced, but first coulombic efficiency decreases leading to irreversible capacity loss
Solution Approach 1:
The invention applies local quality by creating regions with different silicon densities in specific layers. The first silicon material layer with lower density is positioned to interact with the electrolyte, providing high coulombic efficiency, while the second layer with higher density reduces overall specific surface area and electrolyte consumption. This spatial differentiation of material properties resolves the contradiction between electrolyte usage and capacity retention
Data Source
AI summary
The present disclosure provides an anode material and a preparation method therefor, and a battery. The anode material includes a first silicon material layer, and a buffer layer, a second silicon material layer, and a coating layer, which are sequentially arranged on a surface of the first silicon material layer. The density of the first silicon material layer is less than the density of the second silicon material layer. The anode material of the present disclosure has controllable volume expansion, a stable electrolyte solution interface, and high reversible capacity.