Positive Electrode Coating Layer to Inhibit Solid Electrolyte Oxidation
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Solution Overview
Problem
Batteries using solid electrolytes face safety issues due to oxidation of the electrolyte by oxygen from the positive electrode active material, leading to temperature increase and potential malfunction or casing damage.
Innovation Solution
A positive electrode material is developed with a coating layer containing a first solid electrolyte composed of Li, M, and X, where M is a metalloid or metal element and X is F, Cl, Br, or I, and a second solid electrolyte in indirect contact, with a volume ratio of the first solid electrolyte to the total volume of both electrolytes between 4% and 60%, enhancing safety and charge-discharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a second solid electrolyte is used in contact with the positive electrode active material, then charge-discharge efficiency is improved, but oxidation of the electrolyte occurs leading to safety issues
Solution Approach 1:
A coating layer containing a first solid electrolyte (Li-M-X compound where M is metalloid or metal and X is halogen) is formed on the surface of the positive electrode active material. This coating layer acts as an intermediary between the active material and the second solid electrolyte, preventing direct contact and oxidation reactions while maintaining ionic conductivity for efficient charge-discharge operation.
Solution Approach 2:
The patent employs a composite structure combining two different solid electrolytes: a halide-based first solid electrolyte (Li-M-X) with high oxidation resistance and a second solid electrolyte with good ionic conductivity. This composite approach leverages the complementary properties of both materials to achieve both safety and performance.
2Reliability
If the coating layer thickness is increased to improve protection, then oxidation resistance improves, but battery internal resistance increases
Solution Approach 1:
The patent optimizes the thickness of the coating layer containing the first solid electrolyte to a specific range that provides sufficient oxidation protection while maintaining adequate ionic conductivity. By carefully controlling this parameter, the coating becomes thin enough to minimize resistance but thick enough to prevent oxidation of the second solid electrolyte.
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
The solution improves the safety and thermal stability of batteries by inhibiting oxidation of the second solid electrolyte, thereby preventing heat generation and ensuring reliable battery operation.
Implementation Method 1
improving the safety of a battery by inhibiting oxidation of the second solid electrolyte
Data Source
AI summary
A positive electrode material includes a positive electrode active material, a coating layer, and a second solid electrolyte. The coating layer contains a first solid electrolyte and coats at least a portion of a surface of the positive electrode active material. The first solid electrolyte contains Li, M, and X, where M is at least one selected from the group consisting of metalloid elements and metal elements other than Li, and X is at least one selected from the group consisting of F, Cl, Br, and I. The second solid electrolyte is in indirect contact with the positive electrode active material with the coating layer disposed therebetween. A ratio of a volume of the first solid electrolyte to a total volume of the first solid electrolyte and the second solid electrolyte is greater than or equal to 4% and less than or equal to 60%.