NASICON Lithium-Ion Conductive Material for Low-Temperature Sintering
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Solution Overview
Problem
Current solid electrolytes for lithium-ion secondary batteries face challenges in achieving high lithium ion conductivity at lower sintering temperatures, leading to increased grain boundary resistance and reduced conductivity, which affects battery performance and safety due to high sintering temperatures.
Innovation Solution
A lithium ion conductive material with specific compositions, including P2O5, TiO2, Al2O3, Li2O, and optionally SiO2, is mixed and sintered at 800°C or less, incorporating a rhombohedral NASICON structure to enhance lithium ion conductivity while reducing sintering temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a glass-ceramic electrolyte with composition Li1+xAlxTi2-xP3O12 plus AlPO4 is used, then lithium ion conductivity reaches 1×10−3 S/cm at 25°C, but sintering temperature must be 1000°C or higher
Solution Approach 1:
The patent modifies the chemical composition parameters of the solid electrolyte by controlling the ratio of Al2O3 and P2O5 components to be 0.3 to 3.0% and 0.2 to 2.0% by mole smaller than calculated by the stoichiometric formula, respectively. This parameter deviation from exact stoichiometry enables formation of a glass-ceramic structure with sufficient lithium ion conductivity (≥1×10−4 S/cm) at reduced sintering temperatures of 900°C or lower
Solution Approach 2:
The patent creates a composite glass-ceramic electrolyte system combining crystalline phases (Li1+xAlxTi2-xP3O12) with amorphous glassy phases. This composite structure allows the material to achieve adequate lithium ion conductivity through the crystalline pathways while the glassy matrix accommodates the compositional deviations and enables lower sintering temperatures
2Ease of manufacture
If the material is re-sintered at 900°C or higher, then processing is feasible, but grain boundary resistance increases and lithium ion conductivity reduces to about 1×10−4 S/cm
Solution Approach 1:
The patent optimizes the sintering temperature parameter to be 900°C or lower, and specifically controls the Al2O3 and P2O5 content deviations (0.3 to 3.0% and 0.2 to 2.0% by mole smaller than stoichiometric values). This dual parameter control prevents excessive grain boundary resistance formation while maintaining sufficient lithium ion conductivity, resolving the contradiction between manufacturability and performance
3Reliability
If high temperature sintering (1000°C or higher) is used, then solid electrolyte can be formed, but decomposition of electrode active material occurs and discharge capacity decreases
Solution Approach 1:
The patent reduces the sintering temperature parameter to 900°C or lower by controlling the Al2O3 and P2O5 compositional deviations. This temperature reduction prevents thermal decomposition of electrode active materials while still enabling formation of a functional solid electrolyte with adequate lithium ion conductivity, thereby eliminating the harmful effect of electrode material degradation
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
The approach allows for the formation of a solid electrolyte with high lithium ion conductivity at lower temperatures, improving battery performance and safety by reducing grain boundary resistance and maintaining conductivity levels comparable to or exceeding those achieved at higher sintering temperatures.
Implementation Method 1
a solid electrolyte having high lithium ion conductivity can be formed by mixing and sintering, at 800° C. or less
Implementation Method 2
grain boundary resistance in solid electrolyte (resistance to ion conduction occurring at the contact interface between particles)
Data Source
AI summary
The lithium ion conductive material includes, in mole percent on an oxide basis, 36.6 to 37.3% of a P2O5 component, 43.0 to 48.1% of a TiO2 component, 0.6 to 3.2% of an Al2O3 component and 13.9 to 17.5% of a Li2O component, wherein a mole percent of the Al2O3 component is 0.3 to 3.0% by mole smaller than a mole percent of an Al2O3 component calculated by the composition formula Li1+xAlxTi2-xP3O12 (x=0.05 to 0.4) derived from the composition of Ti and Li, and a mole percent of the P2O5 component is 0.2 to 2.0% by mole smaller than a mole percent of a P2O5 component calculated by the above composition formula, and wherein the lithium ion conductive material further includes a crystal phase with a rhombohedral NASICON structure or a Li1+xAlxTi2-xP3O12 (x≥0) crystal phase.