Layered Si Anode Structure for Solid-State Battery Cycle Retention
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Solution Overview
Problem
Conventional batteries using solid electrolytes face a trade-off between capacity retention rate and energy density, with increasing solid electrolyte content leading to decreased energy density.
Innovation Solution
A battery design with a multi-layer negative electrode structure, where the first layer near the electrolyte has a higher ion conductivity and lower solid electrolyte content than the second layer, minimizing negative electrode active material reduction and inhibiting expansion at the electrolyte interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the content of solid electrolyte in the electrode is increased to improve capacity retention rate, then capacity retention rate is improved, but energy density decreases
Solution Approach 1:
The negative electrode layer is divided into two distinct layers: a first layer adjacent to the electrolyte layer and a second layer adjacent to the current collector. This segmentation allows each layer to have different solid electrolyte contents and ion conductivities, optimizing both capacity retention and energy density through localized functional differentiation.
Solution Approach 2:
The first layer is designed with higher ion conductivity (lower solid electrolyte content ≤47.5 vol %) to facilitate efficient ion transport at the electrolyte interface, while the second layer has lower ion conductivity (higher solid electrolyte content) to provide structural stability and suppress expansion. This local quality differentiation resolves the contradiction by assigning different material properties to different spatial locations within the electrode.
2Stability of the object's composition
If the ion conductivity of the negative electrode layer is increased to improve charging uniformity, then charging uniformity is improved, but solid electrolyte content must be reduced which decreases capacity retention
Solution Approach 1:
The negative electrode is segmented into two layers with different ion conductivity characteristics. The first layer has higher ion conductivity for uniform charging, while the second layer has lower ion conductivity but higher solid electrolyte content for capacity retention, eliminating the need to compromise either property throughout the entire electrode.
Solution Approach 2:
Different regions of the negative electrode are assigned different material compositions: the first layer near the electrolyte interface has optimized ion conductivity for charging uniformity, while the second layer has optimized solid electrolyte content for capacity retention. This local quality approach allows both properties to be maximized in their respective locations.
3Duration of action of stationary object
If the solid electrolyte content is optimized to improve cycle characteristics, then cycle characteristics are improved, but energy density is reduced
Solution Approach 1:
The negative electrode layer is segmented into two layers with different solid electrolyte contents. The second layer has higher solid electrolyte content to ensure excellent cycle characteristics and structural stability, while the first layer has lower solid electrolyte content to maintain higher energy density, achieving both goals simultaneously through spatial differentiation.
Solution Approach 2:
The second layer is designed with higher solid electrolyte content specifically to provide structural stability and improve cycle characteristics, while the first layer maintains lower solid electrolyte content to preserve energy density. This local quality optimization allows the battery to achieve both long cycle life 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
Improves energy density and capacity retention rate by uniformly charging the negative electrode layer, enhancing cycle characteristics and reducing resistance.
Implementation Method 1
an electrolyte layer, a negative electrode layer
Implementation Method 2
the first layer and the second layer each contain a Si-based active material and a solid electrolyte as a negative electrode active material
Data Source
AI summary
A battery including a positive electrode current collector, a positive electrode layer, an electrolyte layer, a negative electrode layer, and a negative electrode current collector in that order, wherein the negative electrode layer includes a first layer disposed on the side of the electrolyte layer in a thickness direction and a second layer disposed on the side of the negative electrode current collector in the thickness direction relative to the first layer, wherein the first layer and the second layer each contain a Si-based active material and a solid electrolyte as a negative electrode active material, wherein the value obtained by subtracting the ion conductivity of the second layer from the ion conductivity of the first layer is 0.08 mS/cm or more, and wherein the percentage of the solid electrolyte in the first layer is 47.5 vol % or less.