Lithium Fluoride-Coated Cathode Material With Moisture Control
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Solution Overview
Problem
Batteries using positive electrode materials with halide solid electrolytes face issues with oxidative decomposition, leading to increased internal resistance during charge, and moisture in the active material can react with the coating layer, causing resistance layers and further increasing battery resistance.
Innovation Solution
A coated active material with a lithium-containing fluoride coating layer on the positive electrode active material, where the moisture content is controlled between 0-250 ppm, reducing the formation of resistance layers and enhancing ionic conductivity, thereby lowering output resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a halide solid electrolyte is used as a coating material, then the battery can maintain stable performance, but moisture in the active material reacts with the coating layer to form resistance layers, increasing battery resistance
Solution Approach 1:
The patent applies preliminary action by drying the positive electrode active material before coating to reduce moisture content to 250 ppm or less. This pre-treatment prevents moisture from reacting with the halide solid electrolyte coating layer during subsequent battery operation, thereby preventing resistance layer formation while maintaining the coating's protective functions.
Solution Approach 2:
The patent changes the moisture content parameter of the positive electrode active material from its initial state to a controlled state of 250 ppm or less. This parameter change is achieved through drying treatment and is critical for preventing harmful reactions between moisture and the halide solid electrolyte coating, thus resolving the contradiction between maintaining coating stability and preventing resistance layer formation.
2Quantity of substance
If the positive electrode active material is dried at high temperature, then moisture content is reduced, but the coating layer may deteriorate due to excessive heat
Solution Approach 1:
The patent optimizes the drying temperature parameter within the range of 50°C to 200°C to achieve the desired moisture content reduction without causing coating layer deterioration. This controlled parameter change allows effective moisture removal while preserving the integrity and functionality of the halide solid electrolyte coating layer.
Solution Approach 2:
The patent implements a continuous drying process that maintains the temperature within the optimal range (50°C to 200°C) to continuously remove moisture from the positive electrode active material without interrupting the coating layer's protective function. This continuous controlled action ensures both moisture reduction and coating preservation.
3Ease of manufacture
If the moisture content is not controlled, then the coating process is simpler, but resistance layers form at the interface, increasing output resistance
Solution Approach 1:
The patent applies preliminary action by implementing a drying step before coating to reduce moisture content to 250 ppm or less. This pre-treatment, while adding a process step, prevents resistance layer formation during battery operation, thereby improving reliability and output resistance performance.
Solution Approach 2:
The patent changes the moisture content parameter to 250 ppm or less through controlled drying, which prevents harmful reactions between moisture and the halide solid electrolyte coating. This parameter control ensures low output resistance and high battery reliability while maintaining manufacturing feasibility.
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 coated active material effectively suppresses the generation of resistance layers, reducing battery output resistance and enhancing ionic conductivity, leading to improved battery performance.
Implementation Method 1
when a moisture content of the positive electrode active material from 25° C. to 300° C. is measured by a Karl Fischer method, the moisture content is more than 0 ppm and less than 250 ppm per unit mass of the positive electrode active material
Implementation Method 2
enhancing ionic conductivity, thereby lowering output resistance
Data Source
AI summary
A coated active material includes a positive electrode active material and a coating layer coating a surface of the positive electrode active material. The coating layer includes a lithium-containing fluoride. When moisture content of the positive electrode active material from 25° C. to 300° C. measured by a Karl Fischer method, the moisture content is more than 0 ppm and less than 250 ppm per unit mass of the positive electrode active material. A method for producing the coated active material includes: drying the positive electrode active material so that when moisture content of the positive electrode active material from 25° C. to 300° C. measured by the Karl Fischer method, the moisture content is more than 0 ppm and less than 250 ppm per unit mass of the positive electrode active material; and, after the drying, coating the surface of the positive electrode active material with a coating material including a lithium-containing fluoride.