Sulfide Solid-State Cell Blocking Layer for Interface Stability
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Solution Overview
Problem
Sulfide solid-state cells using LiCoPO4 and LiFePO4 as cathode active materials are not rechargeable due to side reactions between the sulfide-based solid electrolyte and these materials, leading to increased resistance at the interface.
Innovation Solution
Incorporating a blocking layer with a NASICON structure, such as LixAlyTiz(PO4)3 or LixAlyGez(PO4)3, between the cathode active material and the sulfide-based solid electrolyte to prevent contact and inhibit sulfur diffusion and unwanted reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If LiCoPO4 or LiFePO4 is used as cathode active material in sulfide solid-state cell, then high voltage and high capacity are achieved, but the cell becomes non-rechargeable due to side reactions at the interface
Solution Approach 1:
A blocking layer made of phosphoric acid compound with NASICON structure (such as Li1.5Al0.5Ti1.5(PO4)3 or Li1.5Al0.5Ge1.5(PO4)3) is introduced as an intermediary between the cathode active material layer and the sulfide-based solid electrolyte layer. This blocking layer prevents direct contact between LiCoPO4/LiFePO4 and the sulfide electrolyte, thereby preventing side reactions that would otherwise render the cell non-rechargeable, while still allowing the cell to achieve high voltage and capacity through the underlying cathode active materials.
2Device complexity
If cathode active material layer directly contacts sulfide-based solid electrolyte layer, then simple structure is maintained, but interface resistance increases due to side reactions
Solution Approach 1:
The blocking layer serves as a mediator that prevents harmful side reactions at the interface between the cathode active material and the sulfide-based solid electrolyte. By introducing this intermediate layer, the patent resolves the contradiction between structural simplicity and interface stability, as the blocking layer can be applied as a thin coating without significantly complicating the overall cell structure while effectively preventing resistive layer formation.
3Reliability
If blocking layer is introduced to prevent contact between cathode active material and sulfide electrolyte, then rechargeability is enabled, but device complexity increases
Solution Approach 1:
The blocking layer is implemented as a thin film coating on the cathode active material particles or substrate. This thin film approach enables the blocking function to be achieved with minimal additional thickness and mass, thereby enabling rechargeability while keeping the increase in device complexity and size to a minimum. The thin film structure allows the blocking layer to be integrated into the existing cell architecture with minimal structural modification.
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
Enables the rechargeability of sulfide solid-state cells by reducing interface resistance and preventing the formation of resistive layers, thereby enhancing energy density and charge/discharge capabilities.
Implementation Method 1
a blocking layer containing at least one kind of phosphoric acid compound with a NASICON structure, covering at least a part of the surface of the cathode active material and/or the surface of the sulfide-based solid electrolyte, being disposed between the cathode active material layer and the sulfide-based solid electrolyte layer, and being configured to prevent the cathode active material layer from contact with the sulfide-based solid electrolyte layer
Data Source
AI summary
A rechargeable sulfide solid-state cell. The sulfide solid-state cell may include: a cathode active material layer containing at least one kind of cathode active material selected from LiCoPO4 and LiFePO4; an anode active material layer; a sulfide-based solid electrolyte layer containing a sulfide-based solid electrolyte and being disposed between the cathode active material layer and the anode active material layer; and a blocking layer containing at least one kind of phosphoric acid compound with a NASICON structure, covering at least a part of the surface of the cathode active material and/or the surface of the sulfide-based solid electrolyte, being disposed between the cathode active material layer and the sulfide-based solid electrolyte layer, and being configured to prevent the cathode active material layer from contact with the sulfide-based solid electrolyte layer, the phosphoric acid compound being selected from LATP and LAGP.