Aqueous Solid Polymer Electrolyte for Stable High-Voltage Li-Ion Cells

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Solution Overview

Problem

Existing rechargeable batteries with high cell voltages (>3.0 V) face challenges due to the instability of non-aqueous electrolytes, which are prone to flammability, toxicity, and require special handling and processing. Additionally, aqueous electrolytes have a narrow electrochemical stability window, making them unsuitable for most Li-ion battery chemistries.

Innovation Solution

The development of a new class of aqueous solid polymer electrolytes comprising a lithium salt, an ionic liquid, and a polymer, which provides enhanced stability and compatibility with Li-ion battery chemistries, allowing for operation at cell voltages greater than 3 V.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If non-aqueous electrolytes are used to achieve high cell voltages (>3.0 V), then electrochemical stability is improved, but safety hazards and flammability increase

Engineering Contradiction:

Improveelectrochemical stabilityVSAvoidflammability and toxicity

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent uses ionic liquids as intermediary substances between the aqueous polymer electrolyte and the high-voltage electrodes. These ionic liquids form protective interfacial layers that mediate the interaction, providing electrochemical stability at high voltages while preventing direct contact between the flammable non-aqueous components and electrode surfaces, thereby reducing safety hazards

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention creates a composite electrolyte system combining aqueous polymer electrolytes with ionic liquids. This composite structure integrates the benefits of both components: the aqueous polymer provides non-flammability and safety, while the ionic liquid component enables high-voltage operation and electrochemical stability, thus resolving the contradiction between safety and electrochemical stability

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If aqueous electrolytes are used to improve safety, then flammability is reduced, but electrochemical stability window becomes too narrow

Engineering Contradiction:

ImproveflammabilityVSAvoidelectrochemical stability window

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent changes the physical and chemical parameters of the aqueous electrolyte by incorporating ionic liquids and optimizing the polymer matrix composition. This parameter modification expands the electrochemical stability window of the aqueous system, allowing it to operate at high voltages (>3.0 V) while maintaining the inherent safety benefits of aqueous-based electrolytes

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates different local environments within the electrolyte system: the bulk aqueous polymer phase provides safety and non-flammability, while the ionic liquid-rich interfacial regions provide enhanced electrochemical stability and high-voltage tolerance. This local differentiation allows the system to simultaneously achieve both safety and electrochemical stability

Inventive Principle:

Principle #3Local quality

3Reliability

If solid electrolytes are used to improve stability and reduce leakage, then safety is enhanced, but ionic conductivity decreases

Engineering Contradiction:

ImprovestabilityVSAvoidionic conductivity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent develops a composite solid polymer electrolyte combining ionic liquids with polymer matrices. This composite structure provides both the structural stability and leakage prevention of solid electrolytes while the ionic liquid components maintain high ionic conductivity through their inherent ion transport capabilities, thus resolving the contradiction between stability and conductivity

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 electrolyte system achieves high ionic conductivity (1 mS/cm to 7 mS/cm at 25°C) and electrochemical stability, enabling the use of high concentrations of lithium salts and supporting the operation of Li-ion batteries with improved safety and reduced costs.

Implementation Method 1

achieves high ionic conductivity (1 mS/cm to 7 mS/cm at 25°C)

Methodology Applied

Scientific EffectIonic conductivity: Conduction (electrical)

Implementation Method 2

comprising a lithium salt in water

Methodology Applied

Scientific EffectDissolution: Solvation

Data Source

PatentUS20250030047A1High performance air stable solid polymer electrolyte

Publication Date: 2025.01.23 UNIV OF MARYLAND

AI summary

The present invention is directed to aqueous solid polymer electrolytes that comprise a lithium salt and an ionic liquid, and battery cells comprising the same. The present invention is also directed to methods of making the electrolytes and methods of using the electrolytes in batteries and other electrochemical technologies.