Electrode Ceramic Particle Gradient for Battery Safety
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Solution Overview
Problem
Conventional electrodes in lithium secondary batteries are prone to overheating during overcharging due to the closure of voids in the active material-containing layer, leading to dendrite formation and heat generation, while simply mixing ceramic particles to maintain voids reduces capacity.
Innovation Solution
An electrode structure with a higher concentration of ceramic particles in the surface part to prevent void closure, balanced with a lower concentration in the lower part to maintain capacity, where the surface part thickness is between 30% to 60% of the total thickness, and ceramic particles are interposed among active material particles to suppress void closure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the active material-containing layer is pressed to enhance volume energy density, then the volume energy density is improved, but the void in the surface part is closed leading to dendrite formation and heat generation during overcharging
Solution Approach 1:
The patent applies local quality by creating a surface part with different properties from the lower part. The surface part contains ceramic particles resistant to crush and has higher porosity to prevent void closure during pressing, while the lower part can be densely pressed for high energy density. This local differentiation allows the surface to maintain safety during overcharging while the bulk provides high volume energy density.
Solution Approach 2:
The patent uses composite materials by combining active material particles with ceramic particles in the surface part. The ceramic particles (such as alumina, silica, or zirconia) are resistant to crush and maintain void structure under pressure, while the active material particles provide electrochemical functionality. This composite structure prevents dendrite formation during overcharging while maintaining high energy density through optimized pressing.
2Reliability
If ceramic particles are mixed into the active material layer to maintain void, then the void is maintained preventing dendrite formation, but the capacity is reduced due to wasteful ceramic particle distribution
Solution Approach 1:
The patent concentrates ceramic particles in the surface part where they are most needed for preventing void closure and dendrite formation. The lower part contains minimal or no ceramic particles, allowing maximum active material density and capacity. This localized distribution of ceramic particles achieves dendrite prevention without unnecessarily reducing overall capacity.
Solution Approach 2:
The patent segments the active material-containing layer into a surface part and a lower part with different compositions. The surface part contains ceramic particles for structural stability and dendrite prevention, while the lower part is optimized for high active material content and capacity. This segmentation allows each region to be optimized for its specific function, preventing capacity loss from unnecessary ceramic particle distribution throughout the entire layer.
Data Source
AI summary
An electrode has a current collector, and an active material-containing layer provided on the current collector and containing active material particles and ceramic particles, and a weight concentration of the ceramic particles to the active material particles in a surface part in the active material-containing layer on the opposite side to the current collector is higher than a weight concentration of the ceramic particles to the active material particles in a lower part in the active material-containing layer on the current collector side. Furthermore, the thickness of the surface part is not less than 30% nor more than 60% of the total thickness of the surface part and the lower part.