Silicon-Based Anode Material Microstructure for Cycle Life and ICE
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Solution Overview
Problem
Silicon-based negative electrode active materials in secondary batteries face challenges in achieving improved initial Coulombic efficiency and cycle performance due to rapid volume expansion during cycling.
Innovation Solution
A silicon-based negative electrode active material comprising Si and MSiO3, where M is one or more alkaline earth metal elements, with specific XRD diffraction peak ratios and grain size distributions, and optionally coated with a carbon or alkali metal ion conductor material, is prepared through controlled vapor deposition and pulverization processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon-based negative electrode active material is used to increase capacity, then energy density is improved, but volume expansion during cycling occurs leading to poor cycle performance
Solution Approach 1:
The silicon-based negative electrode active material is divided into multiple crystal grains with different orientations. The <100> crystal orientation segments are arranged in a specific pattern to accommodate volume expansion during lithium insertion/extraction cycles, reducing mechanical stress and preventing particle disintegration, thereby improving cycle performance while maintaining high energy density
Solution Approach 2:
The invention uses composite silicon-based materials combining different crystal orientations (<100> and other orientations) in specific ratios. This composite structure leverages the advantages of different crystal planes: <100> orientation provides stable cycle performance by accommodating volume expansion, while other orientations contribute to high capacity, achieving both improved energy density and reliability
2Use of energy by moving object
If silicon-based negative electrode active material is used to increase capacity, then energy density is improved, but initial Coulombic efficiency remains low
Solution Approach 1:
The invention changes the crystallographic orientation parameter of silicon particles, specifically increasing the proportion of <100> oriented crystal grains. This parameter change modifies the electrochemical behavior, enabling more efficient lithium insertion/extraction reactions in the initial cycles, thereby improving initial Coulombic efficiency while maintaining the high capacity advantage of silicon-based materials
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 material exhibits enhanced initial Coulombic efficiency and cycle life, with improved grain size and distribution leading to better electrochemical performance and reduced volume expansion.
Implementation Method 1
heating the raw material to a first temperature to form a vapor by using a vapor deposition technique, and then cooling the vapor to a second temperature to form a deposit
Data Source
AI summary
A silicon-based negative electrode active material comprises Si and MSiO3, where M comprises one or more alkaline earth metal elements. An XRD diffraction pattern of the silicon-based negative electrode active material has a first diffraction peak at a diffraction angle 2θ between 26° and 26.8° with a half peak width of βA, and a second diffraction peak at a diffraction angle 2θ between 31° and 32° with a half peak width of βB. The silicon-based negative electrode active material satisfies 1.5≤βA/βB≤ 5.0.