Composite Electrode Material With Fluoride-Sulfide Electrolyte Layers
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Solution Overview
Problem
Sulfide solid electrolytes in all-solid-state batteries degrade when in direct contact with active materials, leading to impaired ion-conductive properties and increased resistance over time.
Innovation Solution
A composite electrode material is developed with a core particle coated by a fluoride solid electrolyte layer and a sulfide solid electrolyte layer, where the fluoride layer is interposed between the core and sulfide layers to reduce reaction resistance and prevent chip formation that can inhibit conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sulfide SE is used to cover active material to form composite particles, then initial resistance is decreased, but post-endurance resistance increment increases due to degradation of sulfide SE
Solution Approach 1:
The covering layer is divided into two distinct layers: a inner oxide SE layer and an outer sulfide SE layer. This segmentation allows each layer to perform its specific function - the oxide layer protects the sulfide layer from direct contact with active material, while the sulfide layer provides low initial resistance. The segmentation resolves the contradiction by spatially separating the protective function from the conductive function.
Solution Approach 2:
The oxide SE layer acts as an intermediary between the active material and the sulfide SE layer. It mediates the interaction by preventing direct contact between sulfide SE and active material, thereby protecting the sulfide SE from degradation while still allowing for effective ion conduction. This intermediary layer resolves the contradiction by buffering the harmful interaction.
2Reliability
If oxide SE is used between active material and sulfide SE to prevent degradation, then sulfide SE stability is improved, but reaction resistance increases during endurance
Solution Approach 1:
The invention changes the material parameter from pure oxide SE to a composite structure with controlled thickness ratios. By optimizing the thickness of the oxide layer relative to the sulfide layer (specifically making the oxide layer thinner), the reaction resistance is reduced while still maintaining the protective function. This parameter optimization resolves the contradiction between stability and resistance.
Solution Approach 2:
The covering layer is designed as a composite structure combining oxide SE and sulfide SE in specific proportions. This composite material approach allows the system to exhibit both the protective properties of oxide SE and the low-resistance properties of sulfide SE. The composite structure resolves the contradiction by integrating the advantages of both materials while mitigating their individual disadvantages.
3Duration of action of stationary object
If fluoride SE is used between active material and sulfide SE to reduce reaction resistance, then resistance increment during endurance is decreased, but manufacturing complexity increases due to additional layer formation
Solution Approach 1:
The covering layer is segmented into an inner fluoride SE layer and an outer sulfide SE layer. This segmentation enables the fluoride layer to specifically address the resistance increment issue by preventing sulfide SE degradation, while the sulfide layer maintains low initial resistance. The segmented structure resolves the contradiction by assigning specific functions to each layer.
Solution Approach 2:
The invention uses a composite material structure with fluoride SE and sulfide SE in a specific configuration. This composite approach allows the system to achieve low resistance increment during endurance while maintaining acceptable initial resistance. The composite material strategy resolves the contradiction by combining materials with complementary properties.
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
This configuration decreases the increment in resistance over time, enhancing both electronic and ionic conduction in the battery by minimizing the degradation of sulfide solid electrolytes and trapping potential chips within the sulfide layer.
Implementation Method 1
When sulfide SE comes into direct contact with active material inside the electrode, degradation of sulfide SE may be facilitated. The first layer includes a first solid electrolyte (fluoride) which prevents direct contact between sulfide SE and active material
Implementation Method 2
Sulfide SE has high ion-conductive properties and excellent formability
Implementation Method 3
trapping potential chips within the sulfide layer
Data Source
AI summary
An electrode material comprises a composite particle. The composite particle includes a core particle and a covering layer. The covering layer covers at least part of a surface of the core particle. The core particle includes an active material. The covering layer includes a first layer and a second layer. At least part of the first layer is interposed between the core particle and the second layer. The first layer includes a first solid electrolyte. The second layer includes a second solid electrolyte. The first solid electrolyte is a fluoride. The second solid electrolyte is a sulfide.