Crystalline Metal Negative Electrode Active Material for Lithium Ion Battery
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Solution Overview
Problem
Conventional negative electrode active materials using crystalline metals like silicon suffer from short cycle lifetime due to pulverization caused by volume change during lithium occlusion, leading to deterioration of current collection properties.
Innovation Solution
A negative electrode active material with crystalline metal having a size perpendicular to the crystal slip plane of 500 nm or less, which suppresses micronization and fracture, thereby enhancing cycle lifetime by controlling the thickness in the orientation of the slip plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If crystalline metal like silicon is used as negative electrode active material to increase capacity, then the battery capacity is improved, but pulverization occurs due to volume change during lithium occlusion causing short cycle lifetime
Solution Approach 1:
The patent changes the critical parameter of crystal particle size, specifically controlling the size in the perpendicular direction to the slip plane to be 500 nm or less. This parameter change prevents pulverization while maintaining high capacity, resolving the contradiction between battery capacity and cycle lifetime.
Solution Approach 2:
The patent applies different quality requirements to different directions of the crystal particles. By specifically controlling the dimension perpendicular to the slip plane while allowing other dimensions to be larger, the material maintains high capacity locally while preventing pulverization in the critical direction, thus extending cycle lifetime.
2Reliability
If crystalline metal particles are reduced in size to prevent pulverization, then cycle lifetime is improved, but the amount of electricity stored per unit mass decreases
Solution Approach 1:
The patent applies different size characteristics to different spatial directions of the crystal particles. The dimension perpendicular to the slip plane is controlled to be 500 nm or less to prevent pulverization and extend cycle lifetime, while other dimensions can be larger to maintain high electricity storage capacity per unit mass.
Solution Approach 2:
The patent transitions from controlling particle size isotropically (all directions equally) to anisotropically (different directions differently). By specifically controlling only the dimension perpendicular to the slip plane, the patent achieves pulverization prevention without sacrificing overall particle volume and capacity.
3Ease of manufacture
If conventional crystalline silicon with isotropic particle size is used, then manufacturing is simplified, but pulverization occurs due to volume change causing deterioration of current collection property
Solution Approach 1:
The patent introduces a specific parameter control (size perpendicular to slip plane ≤ 500 nm) that prevents pulverization and maintains current collection property. While this adds a dimensional constraint, the patent provides methods to achieve this control during crystal growth, balancing manufacturing feasibility with performance requirements.
Data Source
AI summary
A negative electrode active material for an electric device according to the present invention includes crystalline metal having a structure in which a size in a perpendicular direction to a crystal slip plane is 500 nm or less. More preferably, the size in the perpendicular direction to the crystal slip plane is controlled to become 100 nm or less. As described above, a thickness in an orientation of the slip plane is controlled to become sufficiently small, and accordingly, micronization of the crystalline metal is suppressed even if breakage occurs from the slip plane taken as a starting point. Hence, a deterioration of a cycle lifetime can be prevented by applying the negative electrode active material for an electric device, which is as described above, or a negative electrode using the same, to an electric device, for example, such as a lithium ion secondary battery.