Crown Ether Additives for Stable CEI and SEI in Silicon Li-Ion Cells

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Solution Overview

Problem

Conventional lithium-ion battery technologies face challenges with silicon-based anodes due to large volume changes, unstable solid electrolyte interphase (SEI) formation, and electrolyte decomposition, leading to reduced cycle life and capacity retention, especially when paired with high-voltage cathodes like Ni-rich NCM or LCO.

Innovation Solution

The use of crown ether compounds as additives in lithium-ion batteries to modify the cathode surface and form a stable cathode electrolyte interphase (CEI) and solid-electrolyte interphase (SEI), which helps alleviate transition metal ion dissolution, reduce surface resistance, and enhance the structural stability of silicon anodes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon-based anodes are used to increase capacity, then energy density is improved, but volume expansion and SEI instability occur reducing cycle life

Engineering Contradiction:

Improvebattery capacityVSAvoidcycle life

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

Crown ether compounds serve as intermediary substances that mediate between the silicon anode and electrolyte. These compounds form stable coordination complexes with lithium ions and facilitate the formation of a stable SEI layer, preventing direct harmful interactions between silicon and electrolyte while maintaining high capacity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the chemical composition parameters of the electrolyte by introducing crown ether compounds with specific molecular structures (18-crown-6, 21-crown-7, 24-crown-8). These parameter changes in electrolyte composition lead to fundamental changes in SEI formation mechanisms, transforming the unstable SEI into a stable protective layer

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If high-voltage cathodes (Ni-rich NCM or LCO) are used to increase energy density, then battery performance is improved, but electrolyte decomposition and CEI instability occur

Engineering Contradiction:

Improveenergy densityVSAvoidelectrolyte decomposition

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

Crown ether compounds act as intermediary protective agents between high-voltage cathodes and electrolyte. They preferentially coordinate with lithium ions near the cathode surface and form a stable CEI layer that prevents direct contact between electrolyte and cathode, eliminating electrolyte decomposition pathways

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The crown ether compounds perform preliminary protective action by forming stable CEI layers on cathode surfaces before electrolyte decomposition can occur. This preliminary formation of protective interfaces prevents subsequent harmful reactions during battery operation

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If conventional electrolyte formulations are used with silicon anodes, then manufacturing simplicity is maintained, but capacity retention deteriorates due to SEI instability

Engineering Contradiction:

Improveelectrolyte formulation simplicityVSAvoidcapacity retention

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The invention modifies electrolyte composition parameters by adding small concentrations (0.1-5 wt%) of crown ether compounds to conventional electrolyte formulations. This parameter change transforms the electrolyte's interaction with silicon anodes, enabling stable SEI formation while maintaining manufacturing simplicity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The electrolyte system becomes a composite formulation combining conventional carbonate solvents with crown ether additives. This composite electrolyte exhibits synergistic properties where the crown ether component specifically addresses SEI stability issues while the conventional components maintain overall electrolyte functionality

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

This approach improves the cycle life, energy density, safety, and thermal stability of lithium-ion batteries by stabilizing the SEI and CEI layers, reducing electrolyte decomposition, and maintaining high performance at higher voltages.

Implementation Method 1

form a stable cathode electrolyte interphase (CEI)

Methodology Applied

Scientific EffectSurface film formation:

Implementation Method 2

form a stable cathode electrolyte interphase (CEI) and solid-electrolyte interphase (SEI)

Methodology Applied

Scientific EffectSurface film formation:

Implementation Method 3

crown ether compounds as additives in lithium-ion batteries to modify the cathode surface

Methodology Applied

Scientific EffectCrown ether-Li ion complexation:

Data Source

PatentUS11923545B2Crown ethers as additives for silicon-based Li-ion batteries

Publication Date: 2024.03.05 ENEVATE CORP

AI summary

Additives for energy storage devices comprising crown ethers are disclosed. The energy storage device comprises a first electrode and a second electrode, where 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, and an electrolyte composition. Crown ether compounds may serve as additives to the first electrode and/or the second electrode, as well as the separator.