Composite Electrode Layers to Protect Sulfide Solid Electrolytes
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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
Incorporating a composite particle structure with a fluoride solid electrolyte layer between the active material and sulfide solid electrolyte, and using an imidazoline-based compound as a dispersant to minimize direct contact and enhance dispersibility, thereby reducing resistance increments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sulfide SE is used as solid electrolyte in all-solid-state batteries, then ion-conductive properties are improved, but degradation occurs when in direct contact with active material
Solution Approach 1:
The patent introduces fluoride SE as an intermediary layer between the active material and sulfide SE. This mediator prevents direct contact between sulfide SE and active material, thereby preventing degradation of sulfide SE while maintaining its high ion-conductive properties. The fluoride SE layer acts as a protective barrier that eliminates the harmful interaction.
Solution Approach 2:
The patent creates a composite structure consisting of active material, fluoride SE, and sulfide SE in a layered configuration. This composite particle structure combines the advantages of different materials: active material for electrochemical reaction, fluoride SE for protection and ion conduction, and sulfide SE for high ion conductivity. The composite structure resolves the contradiction by integrating multiple materials with complementary functions.
2Quantity of substance
If active material forms aggregates in the active material layer, then local volume change occurs, but ion conduction path and electron conduction path cannot follow the volume change, leading to resistance increase
Solution Approach 1:
The patent applies local quality by providing each composite particle with a specific layered structure (active material core with fluoride SE and sulfide SE layers). This localized structural design ensures that each particle maintains its integrity during volume changes, and the ion conduction paths can follow the volume changes at the particle level, preventing resistance increase.
Solution Approach 2:
The patent performs preliminary action by pre-forming the composite particle structure with appropriate layers before assembling the active material layer. The fluoride SE and sulfide SE layers are deposited on the active material surface in advance, creating a stable structure that can accommodate subsequent volume changes during battery operation without compromising conduction paths.
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 decreases resistance increments during endurance by maintaining ion and electron conduction paths, even with significant volume changes in the active material layer.
Implementation Method 1
the imidazoline-based compound may act as a dispersant for constituent materials of the active material layer. According to a novel finding of the present disclosure, the imidazoline-based compound may give good dispersibility especially to sulfide SE
Implementation Method 2
The first solid electrolyte is a fluoride. The second solid electrolyte is a sulfide. At least part of the first layer is interposed between the core particle and the second layer
Implementation Method 3
Sulfide SE has high ion-conductive properties and excellent formability. Sulfide SE is suitable for bulk-type all-solid-state batteries
Implementation Method 4
As charge and discharge proceed, active material expands and shrinks. In an active material layer, around the active material, an ion conduction path and an electron conduction path are formed
Data Source
AI summary
An electrode includes an active material layer. The active material layer includes a composite particle and an imidazoline-based compound. 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.