LiBH4-P2S5 Ionic Conductor Composition for Reduction Resistance

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Solution Overview

Problem

The LiBH4—P2S5 system ionic conductor exhibits good ionic conductivity but has low resistance to reduction, limiting its application in all-solid state batteries.

Innovation Solution

An ionic conductor comprising Li, P, S, and I with a crystalline phase having specific XRD peaks at 2θ=29.1°±0.5° and 30.4°±0.5°, and a composition of (100−α){(1−β)LiBH4-βP2S5}-αLiI, where α and β are within specific ranges, is developed, enhancing resistance to reduction by incorporating LiI and suppressing the collapse of the crystalline phase.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If LiBH4-P2S5 system ionic conductor is used, then ionic conductivity is improved, but resistance to reduction deteriorates

Engineering Contradiction:

Improveionic conductivityVSAvoidresistance to reduction

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent creates a composite ionic conductor by incorporating LiI into the LiBH4-P2S5 system. The composite material combines the high ionic conductivity of LiBH4-P2S5 with the reduction resistance of LiI, achieving both improved ionic conductivity and enhanced resistance to reduction simultaneously. The specific composition (100-α){(1-β)LiBH4-βP2S5}-αLiI with α=5-30 mol% and β=5-20 mol% optimizes this composite structure.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent modifies the chemical composition parameters of the ionic conductor by introducing iodine-containing LiI and adjusting the molar ratios of LiBH4, P2S5, and LiI within specific ranges. This parameter change transforms the material properties to achieve both high ionic conductivity and improved resistance to reduction, as evidenced by the specific XRD peak intensity ratio IB/IA≥35% that confirms the crystalline phase structure.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If LiI is added to improve resistance to reduction, then resistance to reduction is improved, but crystalline phase stability may deteriorate

Engineering Contradiction:

Improveresistance to reductionVSAvoidcrystalline phase stability

Core Design Contradiction:

Object-affected harmful factorsVSStability of the object's composition

Solution Approach 1:

The patent precisely controls the molar ratio parameters α and β where α (LiI content) is 5-30 mol% and β (P2S5 content) is 5-20 mol%. These parameter ranges are optimized to maintain crystalline phase stability while incorporating enough LiI to provide reduction resistance. The resulting crystalline phase with specific XRD peaks at 2θ=29.1°±0.5° and 30.4°±0.5° with intensity ratio IB/IA≥35% confirms the stable crystal structure is preserved.

Inventive Principle:

Principle #35Parameter changes

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 resulting ionic conductor demonstrates improved resistance to reduction, making it suitable for use in the negative electrode layer of all-solid state batteries with higher ionic conductivity and reduced reductive decomposition.

Implementation Method 1

has peaks at a position of 2θ=29.1°±0.5° and 30.4°±0.5° in XRD measurement using a CuKα ray

Methodology Applied

Scientific EffectX-ray diffraction: Bragg Diffraction

Data Source

PatentUS20230402611A1Ionic conductor, all-solid state battery, and method of producing ionic conductor

Publication Date: 2023.12.14 TOYOTA JIDOSHA KK

AI summary

The present disclosure provides an ionic conductor containing Li, P, S, BH4, and I, and includes a crystalline phase X having peaks at a position of 2θ=29.1°±0.5° and 30.4°±0.5° in XRD measurement using a CuKα ray.