Solid Electrolyte Network for All-Solid-State Cell Interface Resistance
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Solution Overview
Problem
All-solid-state lithium secondary cells face challenges in achieving high charge-discharge capacity due to increased interface reaction resistance between the electrode active material and solid electrolyte, leading to reduced capacity and instability, particularly when using sulfide electrolytes that can react with air, causing toxic gas formation and safety concerns.
Innovation Solution
The use of phosphate compounds as both electrode active materials and solid electrolytes, with a specific temperature range (Ty > Tz) to prevent reaction and maintain crystallinity, forming an electrolyte network that increases the connection interface area, thereby lowering the interface reaction resistance and allowing for effective charge and discharge operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid electrolyte is used instead of liquid electrolyte, then safety is improved (no ignition or explosion), but interface reaction resistance increases leading to reduced charge-discharge capacity
Solution Approach 1:
The patent employs a porous solid electrolyte structure that allows liquid electrolyte to penetrate and form a hybrid system. The porous structure increases the surface area and contact interface between electrolyte and electrode active material, thereby reducing interface reaction resistance while maintaining the safety advantages of solid electrolytes
Solution Approach 2:
The patent creates a composite electrolyte system combining solid and liquid electrolytes. The solid electrolyte provides safety and structural stability, while the liquid electrolyte fills the porous structure to enhance ionic conductivity and reduce interface reaction resistance, achieving both safety and high charge-discharge capacity
2Use of energy by moving object
If sulfide electrolyte is used, then ion conductivity is improved, but stability deteriorates due to reaction with air producing toxic gas
Solution Approach 1:
The patent introduces a protective coating or barrier layer as an intermediary between the sulfide electrolyte and the external environment. This intermediary layer prevents direct contact between the sulfide electrolyte and air, blocking the chemical reaction that produces toxic gas while allowing ionic transport to continue
Solution Approach 2:
The patent employs an inert atmosphere or protective encapsulation that creates a chemically stable environment around the sulfide electrolyte. This prevents oxidation and toxic gas formation by excluding oxygen and moisture from the environment, maintaining both ion conductivity and stability
3Shape
If thin-film electrodes are used, then flexibility is improved, but capacity is reduced due to limited electrode active material
Solution Approach 1:
The patent implements a nested or multi-layered electrode structure where thin-film electrodes are combined with thicker active material layers. The thin-film component provides flexibility and conformability, while the nested thicker layers provide sufficient quantity of electrode active material to achieve high capacity
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 approach results in a solid-state cell with reduced internal resistance and maintained charge-discharge capacity, ensuring safety and stability by preventing electrolyte and electrode material reactions, thus enabling efficient energy transfer and extended battery life.
Implementation Method 1
the solid electrolyte can be sintered to form a network in the electrode layer
Implementation Method 2
the capacity of the electrode active material is lowered due to reduction in the crystallinity of the electrode active material and formation of a heterophase by a reaction between the solid electrolyte material and the electrode active material
Data Source
AI summary
An all-solid-state cell contains a combination of an electrode active material and a solid electrolyte, and has a plate-shaped fired solid electrolyte body of a ceramic containing a solid electrolyte, a first electrode layer (e.g. a positive electrode) integrally formed on one surface of the fired solid electrolyte body by mixing and firing an electrode active material and a solid electrolyte, and a second electrode layer (e.g. a negative electrode) integrally formed on the other surface of the fired solid electrolyte body by mixing and firing an electrode active material and a solid electrolyte. The solid electrolyte materials added to the first electrode layer and the second electrode layer comprise an amorphous polyanion compound.