Li7-xPS6-xXx-z(BH4)z Solid Electrolyte Conductivity

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Solution Overview

Problem

Rechargeable lithium-ion electrochemical cells with organic liquid electrolytes pose safety risks due to thermal runaway, and existing inorganic solid electrolytes face limitations in ionic conductivity and interface resistance, which affect the performance and safety of lithium-ion electrochemical cells.

Innovation Solution

A compound of formula Li7-xPS6-xXx-z(BH4)z is introduced, where X is a halide ion partially substituted by the borohydride ion, enhancing ionic conductivity and reducing internal resistance, and a process involving grinding a mixture of Li2S, P2S5, LiBH4, and LiX is used to incorporate borohydride ions into the electrolyte structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If inorganic solid electrolytes are used to replace organic liquid electrolytes, then safety is improved by suppressing thermal runaway, but ionic conductivity is reduced

Engineering Contradiction:

ImprovesafetyVSAvoidionic conductivity

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent employs composite materials by combining multiple inorganic compounds (Li2S, P2S5, LiX where X is halogen, and LiBH4) to create a composite solid electrolyte with enhanced ionic conductivity while maintaining safety benefits. The composite structure allows synergistic effects among components to overcome the conductivity limitations of individual inorganic electrolytes.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent changes compositional parameters by varying the ratios of Li2S, P2S5, LiX, and LiBH4, and by controlling the substitution of halide ions (X-) with borohydride ions (BH4-). This parameter optimization achieves a balance between safety and ionic conductivity, with the substituted compounds showing significantly improved conductivity compared to conventional inorganic electrolytes.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If inorganic solid electrolytes are used, then thermal runaway is suppressed, but interface resistance at electrode interfaces increases

Engineering Contradiction:

ImprovesafetyVSAvoidinterface resistance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent optimizes interface resistance by adjusting compositional parameters of the solid electrolyte, specifically controlling the content of LiBH4 and the substitution degree of halide ions. The optimized composition reduces interface resistance while preserving the safety advantages of inorganic solid electrolytes.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If halide ions are substituted by borohydride ions in Li7-xPS6-xXx, then ionic conductivity increases up to seven times, but structural stability may be compromised

Engineering Contradiction:

Improveionic conductivityVSAvoidstructural stability

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The patent carefully controls the substitution parameter z in Li7-xPS6-xXx-z(BH4)z to optimize ionic conductivity while maintaining structural stability. The controlled partial substitution of halide ions with borohydride ions achieves high conductivity without compromising the fundamental crystal structure stability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The substitution of halide ions by borohydride ions is applied locally rather than uniformly throughout the structure. This localized substitution at specific sites within the crystal lattice enhances ionic conductivity pathways while preserving the overall structural framework and its stability.

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 compound significantly increases ionic conductivity by up to seven times, reducing internal resistance and enabling higher discharge voltage in lithium-ion electrochemical cells, while maintaining an amorphous state to enhance isotropic conductivity and ease of fabrication.

Implementation Method 1

One of the main advantages of inorganic solid electrolytes is that they are generally conductors of only one type of ions, here the Li+ cation

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Implementation Method 2

Work on highly conductive amorphous (glass) solid electrolytes based on lithium sulfide Li2S, SiS2, P2S5 and B2S3 was reported as early as the early 1980s

Methodology Applied

Scientific EffectAmorphous structure: Vitrification

Data Source

PatentUS11670798B2Solid electrolyte for a lithium-ion electrochemical cell

Publication Date: 2023.06.06 SAFT GRP SA

AI summary

The invention relates to a compound of the formula Li7-xPS6-xXx-z(BH4)z, in which x is selected from the group comprising Cl, Br, I, F and CN, 0≤x≤2, 0≤z≤0.50. This compound can be used as a solid electrolyte of a lithium-ion electrochemical element.