Fluoride-Coated Cathode Material for Low-Resistance Solid-State Batteries
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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, due to elements like chlorine and iodine in the electrolyte, and high output resistance during discharge due to reactions between lithium-containing alkaline components and fluoride coatings.
Innovation Solution
A coated active material with a lithium-containing fluoride coating layer on the positive electrode active material, where the lithium content is controlled between 0.26% and 0.55% of the material's mass, reducing the formation of resistance layers and enhancing ionic conductivity, thereby reducing output resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a halide solid electrolyte is used in the positive electrode material, then ionic conductivity is improved, but internal resistance increases during charge due to oxidative decomposition
Solution Approach 1:
A protective coating layer comprising lithium fluoride and/or lithium aluminate is applied to the surface of the positive electrode active material particles. This coating layer acts as an intermediary barrier between the halide solid electrolyte and the positive electrode active material, preventing direct contact and thus preventing oxidative decomposition of the halide solid electrolyte during charge, while still allowing ionic conductivity to pass through.
2Reliability
If a fluoride coating is applied to the positive electrode active material, then surface protection is improved, but output resistance increases during discharge due to reactions with lithium-containing alkaline components
Solution Approach 1:
The composition parameters of the coating layer are precisely controlled to comprise lithium fluoride and/or lithium aluminate in specific proportions. By adjusting the chemical composition and stoichiometry of the coating layer, the patent optimizes the balance between surface protection and ionic conductivity, preventing harmful reactions while maintaining low output resistance during discharge.
3Ease of manufacture
If the positive electrode active material surface is left untreated, then manufacturing simplicity is maintained, but both internal and output resistance increase due to unwanted reactions
Solution Approach 1:
The protective coating layer is applied in advance to the surface of the positive electrode active material particles before assembling the battery. This preliminary action of coating prevents unwanted reactions between the halide solid electrolyte and the positive electrode active material during subsequent charge-discharge cycles, addressing both internal resistance during charge and output resistance during discharge, while maintaining manufacturing simplicity through a straightforward coating process.
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 increase in internal resistance during charge and discharge, improving battery performance by controlling lithium content and enhancing ionic conductivity within the specified range.
Implementation Method 1
Batteries using positive electrode materials with halide solid electrolytes face issues with oxidative decomposition, leading to increased internal resistance during charge
Implementation Method 2
where the lithium content is controlled between 0.26% and 0.55% of the material's mass, reducing the formation of resistance layers and enhancing ionic conductivity
Data Source
AI summary
A coated active material includes a positive electrode active material and a coating layer, including lithium-containing fluoride, coating the positive electrode active material. When a mass of lithium derived from a lithium-containing alkaline component on the positive electrode active material is measured by neutralization titration, a proportion of the mass of the lithium in a mass of the positive electrode active material is more than 0.26% and 0.55% or less. A method for producing the coated active material includes: cleaning the positive electrode active material with a water-soluble organic solvent so that when the mass of the lithium is measured by neutralization titration, the proportion of the mass of the lithium in the mass of the positive electrode active material is more than 0.26% and 0.55% or less; drying the positive electrode active material; and coating the positive electrode active material with a coating material including a lithium-containing fluoride.