Electrode Double-Layer Structure for Battery Rate Performance
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in achieving high rate performances and energy density simultaneously, as increasing lithium ion conductivity through solid electrolyte particles in the active material-containing layer can lead to decreased energy density if the ratio of solid electrolyte particles is elevated.
Innovation Solution
The electrode design incorporates a double-layer structure with a first active material portion on the current collector side and a second active material portion on the surface side, where the second active material portion contains a higher concentration of solid electrolyte particles, optimizing lithium ion conductivity while maintaining a lower ratio in the first active material portion to enhance charge and discharge reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the ratio of solid electrolyte particles in the active material-containing layer is increased to enhance lithium ion conductivity, then rate performance is improved, but energy density is decreased
Solution Approach 1:
The patent applies local quality by creating a double-layer structure where the surface-side active material portion has a higher solid electrolyte particle content (0.1-10 wt%) compared to the current collector-side portion. This local differentiation allows the surface layer to have enhanced lithium ion conductivity for improved rate performance, while the bulk interior maintains higher active material content for energy density, thus resolving the contradiction between the two parameters.
2Productivity
If film thickness of the active material-containing layer is reduced to improve lithium ion conductivity, then rate performance is enhanced, but energy density is decreased
Solution Approach 1:
The patent resolves this contradiction by transitioning from a single-layer to a double-layer structure (adding a new dimension of complexity). The surface-side layer with higher solid electrolyte content handles rapid ion transport for rate performance, while the current collector-side layer with higher active material content provides energy storage capacity, allowing both rate performance and energy density to be optimized simultaneously.
3Productivity
If density of the active material-containing layer is reduced to improve lithium ion conductivity, then rate performance is improved, but energy density is decreased
Solution Approach 1:
The patent applies local quality by creating spatial variation in composition within the active material-containing layer. The surface-side portion has lower density with higher solid electrolyte content to facilitate rapid lithium ion transport, while the current collector-side portion has higher density with more active material for energy storage, thus achieving both high rate performance and high energy density.
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
This design enables both high rate performances and energy density by promoting lithium ion movement and reducing localized concentration at the interface, thereby maintaining sufficient charge/discharge capacity and energy efficiency.
Implementation Method 1
the second active material portion further contains solid electrolyte particles... promoting lithium ion movement
Data Source
AI summary
According to one embodiment, an electrode is provided. A length of a first active material portion along a first direction is within a range of 0.7T or more and 0.95T or less with respect to a thickness T of an active material-containing layer. The first direction is parallel to a thickness direction. A second active material portion further contains solid electrolyte particles. A ratio E1/E2 is 0 or more and 0.01 or less. The ratio E1/E2 represents a ratio of a content E1 of the solid electrolyte particles per unit area in the first active material portion (including 0) to a content E2 of the solid electrolyte particles per unit area in the second active material portion.