Lithium-Doped Silicon Oxide Protrusions for Battery Anodes
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries using lithium-containing silicon oxide particles as negative electrode active material face significant capacity degradation due to volume fluctuations during charge and discharge cycles, leading to reduced cycle characteristics and energy density.
Innovation Solution
Fabrication of lithium-containing silicon oxide particles with a surface structure comprising protrusions formed through heating and subsequent lithium doping and dedoping, which absorbs volume changes and prevents particle fracture during cycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium-containing silicon oxide particles are used as negative electrode active material, then energy density is improved, but capacity degradation occurs due to volume fluctuations during charge and discharge cycles
Solution Approach 1:
The particle surface is segmented into multiple protrusions, dividing the surface into distinct regions. This segmentation allows different parts of the particle to handle volume changes independently, preventing catastrophic failure while maintaining high surface area for lithium ion adsorption.
Solution Approach 2:
The protrusions create local variations in surface geometry and properties. The protruded regions can expand and contract more freely during charge-discharge cycles, while the base particle structure remains stable. This local quality differentiation allows the particle to accommodate volume fluctuations without compromising overall structural integrity or energy density.
2Area of stationary object
If surface area of negative electrode active material is increased, then lithium ion adsorption amount is improved, but particle fracture occurs due to stress strain from volume fluctuation
Solution Approach 1:
The protrusions on the particle surface create curved geometries that are more tolerant of volume changes. The curved surfaces can expand and contract more effectively than flat surfaces, distributing stress more evenly and preventing crack initiation. This curvature-based design maintains high surface area while improving structural strength.
Solution Approach 2:
The protrusion structure acts as a pre-designed cushioning mechanism that anticipates volume fluctuations during charge-discharge cycles. The protruded regions can deform and absorb stress before it propagates to the bulk particle structure, preventing fracture while maintaining the high surface area needed for lithium ion adsorption.
3Reliability
If silicon thin film with columnar structures is formed, then volume change is absorbed preventing deformation, but energy density is reduced due to lower surface area
Solution Approach 1:
Instead of forming columnar structures that extend in the vertical dimension (as in thin films), the invention creates protrusions that extend outward from the particle surface in radial directions. This dimensional change allows the structure to absorb volume changes while maintaining a compact particle form factor with high surface area, avoiding the energy density penalty of thin film designs.
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 surface protrusions on the particles effectively mitigate volume changes, maintaining high energy density and minimizing capacity loss even after repeated charge and discharge cycles.
Implementation Method 1
heating treatment
Implementation Method 2
performing doping and dedoping of lithium by electrochemical means
Implementation Method 3
the change in the volume of the negative electrode active material accompanying the charge and discharge is absorbed by the structure comprising a plurality of protrusions
Data Source
AI summary
There is provided a negative electrode for a nonaqueous electrolyte secondary battery in which when a battery is formed, the energy density is high, and moreover, the decrease in charge and discharge capacity is small even if charge and discharge are repeated. By using silicon oxide particles having a particle diameter in a particular range as a starting raw material, and heating these particles in the range of 850° C. to 1050° C., Si microcrystals are deposited on the surfaces of the particles. Then, by performing doping of Li, a structure comprising a plurality of protrusions having height and cross-sectional area in a particular range is formed on the surfaces. The average value of the height of the above protrusions is 2% to 19% of the average particle diameter of the above lithium-containing silicon oxide particles. By using the lithium-containing silicon oxide particles obtained by the above means as a negative electrode active material, a negative electrode for a nonaqueous electrolyte secondary battery is fabricated.