Fibrous Sulfide Electrolyte Cathodes for Stable Solid-State Batteries
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Solution Overview
Problem
Conventional solid electrolytes in lithium batteries have low ionic conductivity and are prone to disconnection of ion conduction paths due to volume changes in the cathode active material during charging and discharging, leading to increased internal resistance and poor high-rate and output characteristics.
Innovation Solution
Incorporating a fibrous sulfide-based solid electrolyte in the cathode active material layer with a core/shell structure to extend ion conduction paths and accommodate volume changes, reducing interfacial resistance and improving ionic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional solid electrolyte particles with an aspect ratio of less than 2 are used, then the battery structure is simple to manufacture, but the ion conduction paths are prone to disconnection during charging and discharging
Solution Approach 1:
The patent applies asymmetry by using fibrous solid electrolyte particles with an aspect ratio of 2 or more, creating an elongated structure that is asymmetric in shape. This asymmetric fibrous structure enables the formation of continuous ion conduction paths through the cathode active material layer, preventing path disconnection during volume changes that occur during charging and discharging cycles.
Solution Approach 2:
The patent changes the key parameter of particle aspect ratio from less than 2 (conventional) to 2 or more (invention). This parameter change transforms the electrolyte morphology from equiaxed or slightly elongated particles to distinctly fibrous structures, which fundamentally improves ion conduction path stability while accommodating cathode material volume changes.
2Object-affected harmful factors
If solid electrolytes are used to improve safety, then the risk of overheating and fire is reduced, but the ionic conductivity and high-rate characteristics deteriorate
Solution Approach 1:
The patent employs composite materials by combining fibrous solid electrolyte particles with cathode active material particles to form a composite cathode layer. This composite structure leverages the safety advantages of solid electrolytes while the unique fibrous morphology enhances ionic conductivity, effectively resolving the contradiction between safety improvement and ionic conductivity maintenance.
Solution Approach 2:
The fibrous solid electrolyte creates a porous network structure within the cathode layer that facilitates ion transport. The interconnected fibrous morphology provides multiple pathways for ion conduction, maintaining high ionic conductivity despite the use of solid electrolyte material that inherently has lower conductivity compared to liquid electrolytes.
3Ease of manufacture
If conventional solid electrolyte particles are used, then the manufacturing process is simple, but the interfacial resistance increases and high-rate characteristics deteriorate
Solution Approach 1:
The asymmetric fibrous shape of the solid electrolyte particles creates larger surface area and extended contact interfaces with cathode active material particles. This asymmetric morphology reduces interfacial resistance by providing more contact points for ion exchange, improving high-rate characteristics while maintaining manufacturing simplicity through particle-based processing.
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
Enhances cycle characteristics, high-rate characteristics, and output characteristics by maintaining ion conduction paths despite volume changes in the cathode active material, thereby improving the overall performance of the all-solid-state secondary battery.
Implementation Method 1
a solid electrolyte may be used to improve the ionic conductivity of the cathode active material layer
Implementation Method 2
the sulfide-based cathode active material may undergo a significant volume change during charging and discharging
Data Source
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AI summary
An all-solid-state secondary battery includes: a cathode layer; an anode layer; and a solid electrolyte layer between the cathode layer and the anode layer, wherein the cathode layer includes a cathode current collector and a cathode active material layer on at least one surface of the cathode current collector, at least one of the cathode active material layer and the solid electrolyte layer includes a first fibrous sulfide-based solid electrolyte, the anode layer includes an anode current collector and a first anode active material layer on one surface of the anode current collector, and an initial charge capacity (B) of the first anode active material layer is less than about 50% of an initial charge capacity (A) of the cathode active material layer.