Silicon Oxide Anode Material With Mg-Li Gradient for Low-Swelling Batteries
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Solution Overview
Problem
Lithium secondary batteries face challenges in improving swelling and service life characteristics due to limitations in negative electrode active materials, particularly with silicon-based particles, which experience decreased discharge capacity and increased viscosity in slurries.
Innovation Solution
The use of silicon-containing oxide particles with specific distributions of Mg and Li, where Mg is uniformly distributed throughout and Li is present in higher amounts on the surface, satisfying certain concentration ratios, enhances the efficiency and minimizes the decrease in discharge capacity and viscosity, thereby improving swelling and service life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon-based particles are used as negative electrode active material to achieve high discharge capacity, then the energy density is improved, but the swelling characteristics and service life deteriorate
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of Mg and Li elements within the silicon-based oxide particles. Specifically, Mg is concentrated in the inner core region while Li is distributed in the outer shell region, with each element serving its function locally. This spatial differentiation allows the particle to simultaneously achieve high discharge capacity (from Si in the core) while suppressing swelling (from Mg in the core and Li in the shell), thereby resolving the contradiction between energy density and reliability.
Solution Approach 2:
The patent employs composite materials by combining multiple elements (Si, Mg, Li, and oxygen) into a composite oxide structure with empirical formula SiOxMg(1-a)Lia. This composite structure integrates the advantages of each element: Si provides high capacity, Mg suppresses swelling, and Li enhances conductivity and stabilizes the structure. The composite material approach enables the negative electrode to achieve both high energy density and improved swelling characteristics/service life simultaneously.
2Productivity
If Mg is added to silicon-based oxide particles to improve initial efficiency, then the initial efficiency is improved, but discharge capacity decreases
Solution Approach 1:
The patent resolves this contradiction by localizing Mg to the inner core region of the particle (within 0-50% radius from center) while concentrating Li in the outer shell region (within 50%-100% radius from center). This spatial separation ensures that Mg's volume-expansion buffering effect protects the Si core and improves initial efficiency, while the Li-rich outer shell maintains high discharge capacity by providing additional Li ions and ensuring electrical conductivity. The graded distribution prevents Mg from overwhelming the particle structure.
Solution Approach 2:
The patent applies parameter changes by precisely controlling the concentration ratios of Mg and Li at different radial positions within the particle. The key parameters are the ratios S(Mg)/C(Mg) and S(Li)/C(Li), where S represents the amount within the outer shell region and C represents the amount within the inner core region. By maintaining these ratios within specific ranges (0.8≤S(Mg)/C(Mg)≤1.2 and 1.0≤S(Li)/C(Li)≤2.0), the patent optimizes both initial efficiency and discharge capacity, resolving the contradiction through quantitative parameter control.
3Ease of operation
If Li is added to silicon-based oxide particles to reduce slurry viscosity, then the slurry viscosity is reduced, but discharge capacity decreases
Solution Approach 1:
The patent resolves this contradiction by localizing Li to the outer shell region of the particle (within 50%-100% radius from center) while concentrating Mg in the inner core region. This spatial arrangement ensures that Li is positioned where it can effectively reduce slurry viscosity by interacting with the slurry medium at the particle surface, while the Mg-rich core maintains structural integrity and discharge capacity. The outer shell Li distribution facilitates slurry processability without compromising the inner core's electrochemical performance.
Solution Approach 2:
The patent applies parameter changes by precisely controlling the concentration ratio S(Li)/C(Li) within the range of 1.0 to 2.0, ensuring that Li is enriched in the outer shell region relative to the core. This quantitative control optimizes Li's ability to reduce slurry viscosity while preventing excessive Li content from causing discharge capacity loss. The parameter optimization allows the system to achieve both improved ease of operation (reduced viscosity) and maintained discharge capacity.
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 specific distribution of Mg and Li in silicon-containing oxide particles improves the initial efficiency and extends the service life of lithium secondary batteries by maintaining discharge capacity and reducing slurry viscosity, leading to enhanced battery performance.
Implementation Method 1
when an amount of Mg and an amount of Li within 50% of the radius in the surface direction from the particle center of the silicon-containing oxide particles are defined as C (Mg) and C (Li), respectively, and an amount of Mg and an amount of Li within 50% of the radius in the center direction from the particle surface of the silicon-containing oxide particles are defined as S (Mg) and S (Li), respectively, the amounts satisfy the following Equation (1) and the following Equation (2): 0.8≤S(Mg)/C(Mg)≤1.2 and 1.0≤S(Li)/C(Li)≤2.0
Data Source
AI summary
A negative electrode active material including silicon-containing oxide particles, in which at least a portion of the silicon-containing oxide particles include Mg and Li, and when an amount of Mg and an amount of Li within 50% of the radius in the surface direction from the particle center of the silicon-containing oxide particles are defined as C (Mg) and C (Li), respectively, and an amount of Mg and an amount of Li within 50% of the radius in the center direction from the particle surface of the silicon-containing oxide particles are defined as S (Mg) and S (Li), respectively.