Silicon Oxide Particle Gradient for Lithium Battery Capacity
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Solution Overview
Problem
Rechargeable lithium batteries face limitations in achieving high-capacity and long cycle-life characteristics due to the use of conventional negative active materials, which often result in reduced reactivity and increased resistance at the negative electrode.
Innovation Solution
The development of silicon oxide particles with a specific concentration gradient of Si and O phases, where the Si phase concentration decreases from the surface to the center and the O phase concentration increases, is used as the negative active material. These particles are prepared through heat treatment and etching processes to create a porous structure with enhanced reactivity with lithium, improving electrochemical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional carbon-based materials are used as negative active material, then the battery structure is simple and easy to manufacture, but the capacity and cycle-life characteristics are limited
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of Si phase within the silicon oxide particles, where the Si phase concentration decreases from the surface to the center. This non-uniform distribution optimizes both capacity (higher Si content at surface for Li reaction) and structural stability (O phase at center provides framework), resolving the contradiction between simple structure and high performance.
2Reliability
If silicon oxide particles with high Si phase concentration are used, then the reactivity with lithium is improved, but the resistance increases
Solution Approach 1:
The patent resolves this contradiction by implementing local quality through spatial variation of Si phase concentration. The surface region has high Si phase concentration (up to 70-80 atom%) for high reactivity with lithium, while the center region has lower Si phase concentration (20-30 atom%) that provides structural stability and reduces resistance. This gradient distribution allows simultaneous optimization of both reactivity and resistance.
Solution Approach 2:
The patent applies dimensionality change by transitioning from a uniform composition to a radially varying composition profile. The concentration of Si phase is expressed as a function of radial distance from the particle center, creating a three-dimensional concentration gradient that simultaneously satisfies conflicting requirements at different spatial locations within the same particle.
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 oxide particles with concentration gradients enhance the capacity and cycle-life of rechargeable lithium batteries by improving reactivity and reducing resistance, leading to better electrochemical performance.
Implementation Method 1
heat treating a silicon oxide material in an inert atmosphere to prepare silicon oxide particles comprising a crystalline Si phase and a silicon oxide phase
Implementation Method 2
adding an etchant to the mixed solution
Data Source
AI summary
According to an embodiment of the present invention, a negative active material for a rechargeable lithium battery includes silicon oxide particles represented by SiOx (where 0<x<2) in which an atom % of a silicon phase decreases in a concentration gradient according to a depth from the surface of each particle to the center of the particle, and has an atom % of an O phase that increases in a concentration gradient. In the atom % concentration graph of the silicon (Si) phase according to the depth, the integral value of the atom % concentration of the silicon (Si) phase from the surface (where the depth is 0) to a depth where the concentration of the silicon (Si) phase is 55 atom % is about 5000 to about 40000 nm·atom %.