Semi-Solid Battery Electrolyte With Stable SEI for Side-Reaction Control

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Solution Overview

Problem

Sulfide-based solid electrolytes in rechargeable batteries face issues such as interface resistance, side reactions, low ionic conductivity, and instability of the Solid Electrolyte Interphase (SEI) layer due to interactions with liquid electrolytes, leading to safety concerns and reduced cycle-life characteristics.

Innovation Solution

A semi-solid rechargeable battery design incorporating a composite electrolyte comprising a sulfide-based solid electrolyte and a liquid electrolyte, with an SEI layer containing LiF, Li3N, and organic components, which stabilizes the negative electrode and enhances ionic conductivity, mechanical properties, and adhesion energy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a liquid electrolyte is added to sulfide-based solid electrolyte to prepare a solid-liquid composite electrolyte, then ionic conductivity is improved, but chemical side reactions occur on the interface

Engineering Contradiction:

Improveionic conductivityVSAvoidchemical side reaction

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent introduces an intermediary protective coating layer on the sulfide-based solid electrolyte particles that acts as a barrier between the liquid electrolyte and sulfide electrolyte, preventing direct chemical contact while allowing ionic transport. This intermediary layer resolves the contradiction by enabling high ionic conductivity through the liquid electrolyte while blocking harmful chemical side reactions at the interface.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent creates a composite electrolyte system consisting of sulfide-based solid electrolyte particles coated with protective material, suspended in liquid electrolyte. This composite structure combines the advantages of both solid and liquid electrolytes while mitigating their disadvantages, achieving high ionic conductivity without chemical side reactions through proper material selection and interface engineering.

Inventive Principle:

Principle #40Composite materials

2Reliability

If a liquid electrolyte is introduced into sulfide-based solid electrolyte, then flame retardant is lost, but ionic conductivity is enhanced

Engineering Contradiction:

Improveionic conductivityVSAvoidflame retardant loss

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The protective coating layer serves as an intermediary that allows the system to benefit from liquid electrolyte's high ionic conductivity while maintaining flame retardancy. The coating acts as a flame barrier and the solid electrolyte matrix provides inherent flame resistance, resolving the contradiction between conductivity enhancement and safety.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent applies local quality by providing flame retardant properties specifically at the particle level through the protective coating on sulfide electrolyte particles, while the bulk liquid electrolyte provides ionic conductivity. This localized approach allows different regions of the electrolyte system to fulfill different functions.

Inventive Principle:

Principle #3Local quality

3Reliability

If conventional composite electrolytes are used, then oxidation stability deteriorates, but ionic conductivity is improved

Engineering Contradiction:

Improveionic conductivityVSAvoidoxidation stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The protective coating layer acts as an intermediary barrier that prevents oxidation of the sulfide-based solid electrolyte by isolating it from oxygen and other oxidizing species in the liquid electrolyte. This allows the system to achieve high ionic conductivity while maintaining oxidation stability through physical separation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs a composite material structure where the protective coating provides oxidation resistance while the sulfide-based solid electrolyte core provides ionic conductivity. This composite approach allows the system to simultaneously achieve both high conductivity and oxidation stability by combining materials with complementary properties.

Inventive Principle:

Principle #40Composite materials

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 proposed design forms a stable SEI layer, improving cycle-life stability and safety by facilitating lithium ion movement, preventing dendrite growth, and maintaining high ionic conductivity while ensuring high mechanical flexibility and adhesion.

Implementation Method 1

a solid-liquid composite electrolyte which includes a sulfide-based solid electrolyte and a liquid electrolyte

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Implementation Method 2

a SEI layer which includes LiF, Li3N, and organic components on a surface of the negative electrode

Methodology Applied

Scientific EffectSolid Electrolyte Interphase formation:

Data Source

PatentUS20250316751A1Semi-solid-state Rechargeable Batteries

Publication Date: 2025.10.09 UIF (UNIV IND FNDTN) YONSEI UNIVERSITY

AI summary

A semi-solid rechargeable battery, comprising a positive electrode, a negative electrode, a composite electrolyte film comprising a solid-liquid composite electrolyte between the positive electrode and the negative electrode, and a SEI layer comprising LiF, Li3N and organic components on the surface of the negative electrode, wherein the solid-liquid composite electrolyte comprises a sulfide-based solid electrolyte and a liquid electrolyte including a salt and an organic solvent.