Composite Solid Electrolyte for All-Solid Battery Sintering
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Solution Overview
Problem
The development of all-solid batteries faces challenges with the high sintering temperature required for LiTa2PO8, which can react with electrode active materials, and the lower ionic conductivity of NASICON-type solid electrolytes, making it difficult to achieve high performance and stability.
Innovation Solution
A composite solid electrolyte layer is created using a combination of LiTa2PO8 phosphate salt and NASICON-type solid electrolyte, with a specific area ratio, alternately stacked with internal electrodes, and a manufacturing method involving a multilayer structure of phosphate salt and NASICON-type amorphous solid electrolyte powders, allowing for low-temperature firing and suppressing mutual diffusion reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiTa2PO8 is used as solid electrolyte to achieve high ionic conductivity, then ionic conductivity is improved, but sintering temperature increases causing mutual diffusion reaction with electrode active material
Solution Approach 1:
The patent uses a composite solid electrolyte layer containing both LiTa2PO8 particles and NASICON-type solid electrolyte particles. The LiTa2PO8 provides high ionic conductivity while the NASICON-type electrolyte enables low-temperature sintering (below 900°C), preventing mutual diffusion reactions with electrode active materials. This composite approach resolves the contradiction by combining materials with complementary properties.
2Temperature
If NASICON type solid electrolyte is used to achieve low sintering temperature, then sintering temperature is reduced, but ionic conductivity decreases
Solution Approach 1:
The composite solid electrolyte layer combines NASICON-type solid electrolyte particles (enabling low-temperature sintering) with LiTa2PO8 particles (providing high ionic conductivity). The synergistic effect allows the battery to be manufactured at low temperatures while maintaining high ionic conductivity, resolving the contradiction between sintering temperature and ionic conductivity.
3Reliability
If high sintering temperature is applied to sinter LiTa2PO8 grains, then ionic conductivity is improved, but mutual diffusion reaction with electrode active material occurs
Solution Approach 1:
The composite structure allows sintering at low temperatures (below 900°C) using the NASICON-type electrolyte, which prevents mutual diffusion reactions with electrode active materials while still achieving sufficient ionic conductivity through the combined effect of both electrolyte materials.
Solution Approach 2:
The NASICON-type solid electrolyte acts as an intermediary that enables low-temperature processing, preventing direct harmful interactions between LiTa2PO8 and electrode active materials during sintering, while still allowing the LiTa2PO8 to contribute its high ionic conductivity 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 approach achieves high ionic conductivity and stability in all-solid batteries, enabling favorable cell characteristics and reduced sintering temperatures while preventing material diffusion, thus enhancing battery performance and usability.
Implementation Method 1
LiTa2PO8 has high ionic conductivity such as 2.5×10−4 S/cm at a room temperature
Implementation Method 2
grains of the oxide-based solid electrolyte are sintered during firing at a high temperature and an interface resistance is reduced
Data Source
AI summary
Solid electrolyte includes a first solid electrolyte that is a phosphate salt including Li and Ta, and a second solid electrolyte that is NASICON type solid electrolyte. In a cross section of the solid electrolyte, an area ratio of the first solid electrolyte is more than 10% and an area ratio of the second solid electrolyte is more than 10%.