Composite active material
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Moisture in positive electrode active materials leads to increased output resistance due to the formation of resistive layers at the interface, which deteriorates the performance of solid-state batteries.
Innovation Solution
A composite active material is developed with a first coat layer containing a fluoride-containing solid electrolyte and a second coat layer comprising a sulfide-containing solid electrolyte and solvent, allowing for a water content of up to 823 ppm, which suppresses moisture adsorption and deterioration by preferentially containing moisture in the second coat layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the positive electrode active material is coated with a lithium-containing fluoride material, then the moisture resistance is improved, but the output resistance increases due to resistive layer formation at the interface
Solution Approach 1:
The coating is divided into two distinct layers: a first coat layer containing lithium-containing fluoride that provides moisture resistance, and a second coat layer containing conductive material that reduces output resistance. This segmentation allows each layer to perform its specific function without the adverse effects of the other, resolving the contradiction between moisture resistance and low output resistance
Solution Approach 2:
Different regions of the coating have different properties: the first coat layer (inner layer) has high moisture resistance but higher resistance, while the second coat layer (outer layer) has high conductivity but lower moisture resistance. By assigning different local qualities to different layers, the system achieves both moisture resistance and low output resistance simultaneously
2Quantity of substance
If the water content of the positive electrode active material is increased, then the permissible water content of the composite is increased, but the moisture adsorption generates resistive layers that increase output resistance
Solution Approach 1:
The dual-layer coating acts as an intermediary system between the active material and the external environment. The first coat layer mediates moisture protection while the second coat layer mediates conductivity, allowing the system to tolerate higher water content without generating harmful resistive layers at the active material interface
3Reliability
If a single coat layer of lithium-containing fluoride is used, then the moisture resistance is improved, but the device complexity increases due to the need for strict moisture control
Solution Approach 1:
The invention changes the parameters of the coating system by introducing a second coat layer with different composition and properties. This parameter change allows the system to achieve moisture resistance while simultaneously maintaining low output resistance and reducing the complexity of moisture control requirements through the complementary functions of the two layers
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 composite active material enhances moisture tolerance, reducing output resistance and maintaining battery performance even with a higher water content, as moisture is contained in the second coat layer and can be removed during electrode film formation.
Implementation Method 1
a high water content of the second coat layer can lead to reduced moisture adsorption on the active material
Implementation Method 2
The composite active material according to the present disclosure includes two different types of coat layers on the surface of the active material, thereby being capable of suppressing deterioration of the active material caused by moisture
Data Source
AI summary
Provided is a composite active material that is capable of more suppressing deterioration of an active material caused by the moisture of the composite active material than a conventional composite active material by increasing a permissible water content of a layer of the composite active material. The composite active material that is used for solid-state batteries includes: an active material; a first coat layer that contains a fluoride-containing first solid electrolyte, the first coat layer coating at least part of a surface of the active material; and a second coat layer that contains a sulfide-containing second solid electrolyte, and a solvent, the second coat layer coating at least part of the first coat layer, wherein a water content of the composite active material at 200° C. measures at most 823 ppm on a Karl Fischer titrator.