Positive Electrode Material Using Dual Solid Electrolytes Against Oxidation
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Solution Overview
Problem
Batteries using solid electrolytes face safety issues due to oxidation of the electrolyte by oxygen released from the positive electrode active material, leading to temperature increase and potential malfunction or casing damage.
Innovation Solution
A positive electrode material comprising a positive electrode active material, a first solid electrolyte containing Li, Zr, M, and X, and a second solid electrolyte with a different composition, where the volume ratio of the first solid electrolyte to the total volume of both electrolytes is between 3% and 60%, inhibiting oxidation reactions and improving safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid electrolyte is used in a battery, then the battery safety is improved, but the solid electrolyte can be oxidized by oxygen released from the positive electrode active material, leading to temperature increase and potential malfunction
Solution Approach 1:
An oxide coating layer is introduced as an intermediary between the positive electrode active material and the solid electrolyte. This coating layer acts as a protective barrier that prevents direct contact and oxidation reactions between the solid electrolyte and oxygen released from the active material, while still allowing lithium ion transport. The coating layer mediates the interaction between the two components, eliminating the harmful oxidation effect.
Solution Approach 2:
The positive electrode structure is designed as a composite material system consisting of the positive electrode active material, the oxide coating layer, and the solid electrolyte. The oxide coating layer serves as a protective interface that combines the benefits of both components while eliminating their incompatibility. This composite structure maintains the high capacity of the active material and the safety of the solid electrolyte simultaneously.
2Object-affected harmful factors
If the oxide coating layer is made thicker to better protect against oxidation, then the protection effect is improved, but the lithium ion transport resistance increases
Solution Approach 1:
The thickness of the oxide coating layer is optimized to a specific range (5 nm to 50 nm) to balance protection and ion transport. By controlling the thickness parameter within this optimal range, the coating provides sufficient oxidation protection while maintaining low resistance to lithium ion diffusion. This parameter optimization resolves the contradiction between protective function and ionic conductivity.
Solution Approach 2:
The oxide coating layer is designed with specific local properties - it is thin enough to allow efficient lithium ion transport but thick enough to provide oxidation protection. The coating's composition and structure are locally optimized at the interface between the active material and solid electrolyte to achieve both protection and conductivity, rather than making the entire battery structure thick or thin.
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 proposed solution effectively inhibits oxidation reactions, enhancing the safety and thermal stability of batteries by maintaining a suitable volume ratio of the first solid electrolyte, thereby preventing excessive heat generation and ensuring battery integrity.
Implementation Method 1
oxidation of the electrolyte by oxygen released from the positive electrode active material
Data Source
AI summary
A positive electrode material includes a positive electrode active material, a first solid electrolyte, and a second solid electrolyte. The first solid electrolyte contains Li, Zr, M, and X. M is at least one selected from the group consisting of metalloid elements and metal elements other than Li. X is at least one selected from the group consisting of F, Cl, Br, and I. The second solid electrolyte has a different composition than the first solid electrolyte. 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 3% and less than or equal to 60%.