Metal Sulfide Electrolyte Additives for Stable Silicon Anodes

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Solution Overview

Problem

Conventional lithium-ion battery technologies face challenges with silicon-based anodes due to large volumetric expansion, unstable solid electrolyte interphase (SEI) layers, and oxidative instability of electrolytes, leading to reduced cycling life and capacity retention, especially when paired with high-voltage cathodes like Ni-rich NCM or LCO.

Innovation Solution

Incorporating metal sulfide compounds as electrolyte additives to form a stable, electronically insulating but ionically conducting SEI layer on silicon anodes and a protective cathode electrolyte interphase (CEI) on high-voltage cathodes, enhancing electrochemical stability and thermal safety.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon-based anode materials are used to increase energy density, then capacity is improved, but volumetric expansion occurs leading to reduced cycling life

Engineering Contradiction:

ImprovecapacityVSAvoidcycling life

Core Design Contradiction:

Quantity of substanceVSDuration of action of stationary object

Solution Approach 1:

The patent changes the chemical composition parameters of the electrolyte by introducing metal sulfide compounds (Li2S, Na2S, KS, Rb2S, Cs2S) at specific concentrations (0.1-10 wt%). This parameter change modifies the SEI layer properties to accommodate silicon's volumetric expansion while maintaining stability, thus resolving the contradiction between high capacity and cycling life.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Metal sulfide compounds act as intermediary substances that mediate between the silicon anode and the electrolyte. They form a stable SEI layer that serves as a protective interface, allowing the silicon to expand and contract during cycling without direct contact with the unstable electrolyte, thereby preserving both capacity and cycling life.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Quantity of substance

If conventional electrolytes are used with silicon anodes, then initial capacity is achieved, but oxidative instability occurs reducing battery lifetime

Engineering Contradiction:

ImprovecapacityVSAvoidbattery lifetime

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The electrolyte composition is modified by adding metal sulfide compounds that change the electrochemical stability window and reduce oxidative instability. This parameter change enables the electrolyte to remain stable at high voltages while maintaining good ionic conductivity for capacity delivery.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the potential harm of electrolyte oxidation into a benefit by using metal sulfide compounds that preferentially react to form a stable SEI layer. This layer prevents further oxidation reactions, transforming the initially unstable interaction into a protective mechanism that extends battery lifetime.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Quantity of substance

If high-voltage cathodes like Ni-rich NCM or LCO are used to increase energy density, then capacity is improved, but electrolyte decomposition occurs reducing safety

Engineering Contradiction:

ImprovecapacityVSAvoidelectrolyte decomposition

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

Metal sulfide compounds serve as intermediary substances that form a protective CEI layer on the high-voltage cathode surface. This intermediary layer prevents direct contact between the electrolyte and the high-voltage cathode materials (Ni-rich NCM or LCO), thereby preventing electrolyte decomposition while allowing capacity delivery.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The addition of metal sulfide compounds changes the interfacial electrochemical parameters at the cathode-electrolyte interface. This creates a more stable interface that can withstand high voltages without decomposition, enabling the use of high-voltage cathodes for increased capacity while maintaining safety.

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 use of metal sulfide compounds improves cycle life, energy density, safety, and thermal stability of lithium-ion batteries by reducing electrolyte consumption and gassing, while maintaining electrochemical performance and preventing electrolyte decomposition.

Implementation Method 1

Incorporating metal sulfide compounds as electrolyte additives to form a stable, electronically insulating but ionically conducting SEI layer on silicon anodes

Methodology Applied

Scientific EffectSolid electrolyte interphase formation:

Implementation Method 2

Methodology Applied

Scientific EffectCathode electrolyte interphase formation:

Data Source

PatentUS11876180B2Silicon-based energy storage devices with metal sulfide containing electrolyte additives

Publication Date: 2024.01.16 ENEVATE CORP

AI summary

Electrolytes and electrolyte additives for energy storage devices comprising metal sulfide compounds are disclosed. The energy storage device comprises a first electrode and a second electrode, wherein at least one of the first electrode and the second electrode is a Si-based electrode, a separator between the first electrode and the second electrode, an electrolyte, and at least one electrolyte additive selected from a metal sulfide compound.