Garnet Solid Electrolyte Sintering via Lithium Borate
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Solution Overview
Problem
Current garnet-type ion conducting oxides require high sintering temperatures for integration with active material layers, leading to inefficiencies in lithium secondary battery production.
Innovation Solution
Incorporating lithium borate and aluminum oxide into the garnet-type ion conducting oxide composition allows for lower-temperature sintering, enabling the integration of solid electrolyte and active material layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If garnet-type ion conducting oxide is sintered at high temperature (1200°C), then lithium ion conductivity is enhanced, but manufacturing cost and energy consumption increase
Solution Approach 1:
The invention changes the chemical composition parameters of the garnet-type oxide by introducing dual substitution: replacing Zr4+ with Nb5+ at the Zr site and replacing La3+ with alkaline-earth metals (Ca2+, Sr2+, or Ba2+) at the La site. This compositional parameter change enables sintering at lower temperatures (900-1100°C) while maintaining high lithium ion conductivity, thus reducing sintering energy consumption without sacrificing reliability
Solution Approach 2:
The invention creates a composite substituted garnet structure Li7+X−Y(La3−x,Ax)(Zr2−Y,NbY)O12 where multiple elements are combined in specific ratios. The synergistic effect of Nb substitution (enhancing conductivity) and alkaline-earth metal substitution (reducing sintering temperature) allows the material to achieve both high lithium ion conductivity and low sintering energy consumption, resolving the contradiction between these two parameters
2Reliability
If garnet-type ion conducting oxide is sintered at high temperature (1200°C), then lithium ion conductivity is enhanced, but manufacturing complexity increases
Solution Approach 1:
By optimizing the substitution parameters (x, y, X) in the composition Li7+X−Y(La3−x,Ax)(Zr2−Y,NbY)O12, the invention achieves a sweet spot where adequate lithium ion conductivity is obtained at lower sintering temperatures (900-1100°C). This parameter optimization simplifies the sintering process, reduces equipment requirements, and decreases manufacturing complexity while maintaining reliable conductivity performance
3Reliability
If Al is added to Li7La3Zr2O12-based solid electrolyte, then density and conductivity are improved, but sintering temperature remains high (1125°C to 1250°C)
Solution Approach 1:
The invention extends the Al-substituted garnet approach by introducing a second substitution mechanism using Nb at the Zr site. This dual-substitution composite structure (Al at La site + Nb at Zr site) creates synergistic effects: Al substitution provides baseline conductivity improvement, while Nb substitution further enhances conductivity and crucially reduces the sintering temperature to 900-1100°C, resolving the contradiction between achieving high conductivity and maintaining low sintering temperature
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 reduces the sintering temperature to 700-800°C, enhancing lithium ion conductivity and achieving integral sintering of the solid electrolyte and active material layers, thus improving battery production efficiency.
Implementation Method 1
addition of lithium borate and aluminum oxide to a garnet-type ion conducting oxide... allows for lower-temperature sintering
Implementation Method 2
chemical reaction between the additive materials and chemical reactions between the additive materials and the base material occur at about 700° C. and lead to mutual diffusion
Data Source
AI summary
An all-solid lithium secondary battery 20 includes a solid electrolyte layer 10 composed of a garnet-type oxide, a positive electrode 12 formed on one surface of the solid electrolyte layer 10 and a negative electrode 14 formed on the other surface of the solid electrolyte layer 10. This all-solid lithium secondary battery 20 includes an integrally sintered complex of the solid electrolyte layer 10 and the positive electrode active material layer 12a. This complex is obtained by integrally sintering a stacked structure of an active material layer and a solid electrolyte layer. The solid electrolyte layer includes: abase material mainly including a fundamental composition of Li7+X−Y(La3−x,Ax) (Zr2−Y,TY)O12, wherein A is one or more of Sr and Ca, T is one or more of Nb and Ta, and 0≦X≦1.0 and 0≦Y<0.75 are satisfied, as a main component; and an additive component including lithium borate and aluminum oxide.