Positive Electrode Layer Composition for Faster-Charging Solid-State Batteries
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Solution Overview
Problem
Existing secondary batteries, particularly all-solid-state lithium secondary batteries, do not achieve sufficient rapid charging characteristics when using the positive electrode active material layer configuration described in WO 2020/241691 A.
Innovation Solution
Control the amount of solid electrolyte in the positive electrode active material layer to specific values: 1% by mass or more in the first layer and 0% to less than 1% by mass in the second layer, with respect to the total solid content in each layer, to improve rapid charging characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a positive electrode active material layer containing solid electrolyte and binder is used, then ion conductivity is improved, but rapid charging characteristics deteriorate
Solution Approach 1:
The positive electrode active material layer is divided into a first layer containing solid electrolyte and binder for ion conductivity, and a second layer without solid electrolyte for rapid charging performance. This segmentation allows each layer to fulfill its specific function independently, resolving the contradiction between ion conductivity and rapid charging characteristics.
Solution Approach 2:
The first layer near the solid electrolyte layer is designed with high solid electrolyte content (1% or more) to ensure ion conductivity, while the second layer near the current collector is designed with low or zero solid electrolyte content to enable rapid charging. This local differentiation of composition optimizes both contradictory requirements in their respective zones.
2Reliability
If solid electrolyte content is increased in the positive electrode active material layer, then ion conductivity is improved, but internal resistance increases
Solution Approach 1:
The layer is segmented into two zones with different solid electrolyte concentrations. The first layer has sufficient solid electrolyte (1% or more) for ion conductivity, while the second layer has minimal solid electrolyte (0% to less than 1%) to reduce internal resistance, thereby resolving the contradiction between these two opposing effects.
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 configuration enhances the rapid charging capabilities of the secondary battery by optimizing the electrolyte distribution, leading to improved ion conductivity and reduced internal resistance.
Implementation Method 1
a solid electrolyte for improving lithium ion conductivity in the positive electrode active material layer
Data Source
AI summary
A secondary battery has a power generating element including a positive electrode having a positive electrode active material layer disposed on a positive electrode current collector. The positive electrode active material layer comprises a first layer in contact with a solid electrolyte layer and containing a positive electrode active material, a solid electrolyte and a binder, and a second layer in contact with the positive electrode current collector and containing a positive electrode active material and a binder. The solid electrolyte in the first layer is 1% by mass or more with respect to 100% by mass of a total solid content contained in the first layer, and the solid electrolyte in the second layer is 0% by mass, or is more than 0% by mass or less than 1% by mass with respect to 100% by mass of a total solid content contained in the second layer.