Gradient-Doped SiOx Anode Material for Volume Expansion Relief
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Solution Overview
Problem
The industrialization of Silicon-based negative electrode materials for lithium-ion batteries is hindered by poor cycling performance due to significant volume expansion during lithium intercalation and deintercalation, leading to inefficient first-cycle charge and discharge and reduced cycle life.
Innovation Solution
A negative electrode material with a metal element gradient-doped in a concentration-gradient manner, where the metal element content decreases from the surface to the core, providing a space for volume expansion and alleviating stress accumulation, thereby improving cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If SiOx is used as negative electrode material to reduce volume expansion compared to silicon, then volume expansion is reduced, but first-cycle efficiency drops below 75% due to irreversible lithium oxide formation
Solution Approach 1:
The patent applies gradient doping where the metal element concentration varies spatially from surface to core, creating different local compositions: higher metal content at surface to prevent lithium oxide formation and improve first efficiency, lower metal content at core to maintain capacity. This local quality variation resolves the contradiction between first-cycle efficiency and volume expansion control.
Solution Approach 2:
The patent creates a composite material system combining SiOx with gradient-doped metal elements (such as Al, Mg, Li, Mn, Fe, Co, Ni, Cu, or Zn). This composite structure leverages the beneficial properties of both SiOx (lower volume expansion than silicon) and the doped metal elements (improved first efficiency and cycling performance), resolving the technical contradiction.
2Reliability
If uniform doping is used to improve first efficiency, then first efficiency improves, but volume expansion stress accumulates rapidly reducing cycling performance
Solution Approach 1:
The gradient doping profile creates local quality differences: surface regions with higher metal content to improve first efficiency, and core regions with lower metal content to accommodate volume expansion. This spatial variation in doping concentration allows the material to simultaneously achieve good first efficiency and maintain structural integrity during cycling, resolving the contradiction between first efficiency and cycling performance.
Solution Approach 2:
The patent changes the doping concentration parameter from uniform to gradient distribution. By varying the metal element concentration as a function of position (higher at surface, lower at core), the material properties are optimized to balance first efficiency improvement with volume expansion management, thereby improving cycling performance while maintaining high first efficiency.
3Reliability
If high metal element doping is used to improve first efficiency, then first efficiency improves, but volume expansion increases due to metal element expansion
Solution Approach 1:
The gradient doping strategy places higher metal element concentrations at the surface where they improve first efficiency by preventing lithium oxide formation, while maintaining lower metal concentrations in the core to minimize volume expansion. This local quality differentiation resolves the contradiction between improving first efficiency through doping and controlling overall volume expansion.
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 gradient doping method effectively slows down volume expansion and enhances cycling performance by allowing slow pressure release, resulting in improved first-cycle efficiency and extended cycle life compared to uniformly doped materials.
Implementation Method 1
the process of lithium deintercalation is accompanied by about 300% volume expansion
Implementation Method 2
provides a space for the expansion of SiOx particles, so as to realize slow pressure release, thus slowing down the accumulation of stress
Implementation Method 3
slowing down the accumulation of stress, and helping to alleviate the negative impact of volume expansion and improve the cycling performance of materials
Data Source
AI summary
A negative electrode material on which a metal element is gradient-doped and an application thereof. The negative electrode material comprises a granular silica/M composite material on which a metal element M is gradient-doped. The general formula of the silica is SiOx, wherein 0<x<2. The metal element M comprises one or more among Na, Mg, Al, Li, Mn, Fe, Co, Ni, Cu, or Zn. In the negative electrode material, the content of the metal element M gradually decreases from the surface to the core, presenting a doping distribution having a continuous concentration gradient. The general chemical formula of the silica/M composite material is SiMyOz, wherein 0<y<10 and 0<z<10.