Zr-Doped LiTi2(PS4)3 Solid Electrolyte Conductivity

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Solution Overview

Problem

The existing methods for preparing lithium titanium thiophosphate LiTi2(PS4)3 do not optimize ionic conductivity, which is crucial for high-energy density all-solid-state battery systems.

Innovation Solution

A Zr-doped compound Li(Ti1-xZrx)2(PS4)3 is synthesized through a method involving mechanical milling or melt-quenching followed by heat treatment at 350°C to 500°C, optimizing the crystal structure for enhanced ionic conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the conventional synthesis method (heating under vacuum at high temperature) is used, then the material can be prepared, but the ionic conductivity is not optimized

Engineering Contradiction:

Improveionic conductivityVSAvoidsynthesis method optimization

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention changes the synthesis parameters by introducing Zr doping at controlled concentrations (x=0.01 to 0.25) and using a two-step process (mechanical milling followed by heat treatment at 350-500°C). This parameter modification optimizes the ionic conductivity from the conventional method's insufficient level to the improved range of 10^-5 to 10^-4 S/cm at room temperature.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a doped composite material Li(Ti1-xZrx)2(PS4)3 by incorporating Zr elements into the LiTi2(PS4)3 crystal structure. This composite approach combines the base material with dopant elements to achieve enhanced ionic conductivity while maintaining the overall structural integrity of the solid electrolyte.

Inventive Principle:

Principle #40Composite materials

2Reliability

If Zr doping is applied to expand conduction channels, then ionic conductivity increases, but crystal structure stability may be compromised

Engineering Contradiction:

Improveionic conductivityVSAvoidcrystal structure stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The invention applies local quality modification by introducing Zr dopants at specific lattice positions within the LiTi2(PS4)3 structure. The dopants are distributed at controlled concentrations (x=0.01 to 0.25) to locally expand conduction channels and enhance ionic conductivity while maintaining overall crystal structure stability through controlled doping levels.

Inventive Principle:

Principle #3Local quality

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 Zr-doped lithium titanium thiophosphate exhibits high ionic conductivity within specific composition ranges, particularly 0.01≤x≤0.25, expanding the conduction channels and minimizing impurities, thereby improving battery performance.

Implementation Method 1

subjecting the mixture prepared in step (a) to a preliminary reaction step through mechanical milling or melt-quenching to produce an intermediate amorphous sulfide mixture

Methodology Applied

Scientific EffectMelt-quenching:

Implementation Method 2

subjecting the mixture prepared in (b) to a heat treatment step at a maximum plateau temperature of at least 350° C. and less than 500° C.

Methodology Applied

Scientific EffectHeat treatment: Heat Treatment

Data Source

PatentUS11063293B2Increasing ionic conductivity of LiTi2(PS4)3 by Zr doping

Publication Date: 2021.07.13 TOYOTA JIDOSHA KK

AI summary

A compound represented by the general formula Li(Ti1-xZrx)2(PS4)3, wherein 0.01≤x≤0.25, and found to have high ionic conductivity; a use of the compound as a solid electrolyte, in particular in an all solid-state lithium battery.