All-Solid Battery Cathode Structure to Prevent End Short Circuits
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Solution Overview
Problem
All-solid batteries face challenges with short circuits due to expansion and contraction of cathode active materials at the ends of the battery, leading to energy density deterioration and increased electric resistance, which existing solutions like shifting end faces do not adequately address.
Innovation Solution
The battery design includes a cathode layer with a region where the distance between cathode active material particles is twice the average particle size, and a production method involving dry-coating, preliminary pressurization, and controlled pressure application to form a configuration that suppresses short circuits and enhances energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the cathode active materials are densely packed to increase energy density, then the battery capacity increases, but short circuits occur due to contact between cathode particles at the battery ends
Solution Approach 1:
The cathode layer is divided into a central dense region and end regions with different particle spacing. The end regions are segmented to have larger distances between cathode active material particles (at least 2 times the average particle size), preventing contact and short circuits while maintaining high capacity in the central region
Solution Approach 2:
Different regions of the cathode layer are given different local properties: the central region has high density for maximum energy density, while the end regions have reduced density with increased particle spacing to prevent short circuits. This local differentiation resolves the contradiction between overall density and end-region safety
2Quantity of substance
If the cathode layer is uniformly dense throughout to maximize energy density, then battery capacity increases, but electric resistance increases and charging/discharging efficiency decreases
Solution Approach 1:
The cathode layer exhibits local quality variation with dense central regions for high capacity and less dense end regions for lower resistance. This gradient structure allows the battery to achieve high overall capacity while maintaining efficient charge/discharge performance through the lower-resistance end pathways
3Reliability
If the cathode and anode layers are stacked with shifted end positions to prevent short circuits, then short circuit risk reduces, but the volume occupied by non-active material increases, reducing energy density
Solution Approach 1:
Instead of shifting the anode layer relative to the cathode layer (conventional approach), this invention keeps the layers aligned but modifies the cathode layer's internal structure at the ends. The inversion is in the approach: rather than misaligning layers, it creates a structured gradient within the cathode layer itself, eliminating the need for wasteful shifts while preventing short circuits
Data Source
AI summary
An all-solid battery has a structure in which a cathode current collector, a cathode layer that contains cathode active materials constituted by a plurality of particles and solid electrolytes constituted by a plurality of particles, a solid-electrolyte layer that contains solid electrolytes, an anode layer that contains anode active materials and solid electrolytes, and an anode current collector are stacked in this order. The cathode layer includes a region where the plurality of particles constituting the solid electrolytes are filled or continuously densely packed in a sliced surface in a case where an end of the cathode layer is sliced, and a distance between two adjacent particles having a positional relationship across the region among the plurality of particles constituting the cathode active material is 2 times or more than an average particle size of the cathode active materials.