Li-Ion Battery Electrolyte Composition for Oxidation Suppression

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Solution Overview

Problem

Existing lithium-ion battery electrolytes face challenges in maintaining optimal viscosity, conductivity, and stability, particularly in high-rate charging and discharging conditions, leading to issues such as electrochemical oxidation, capacity fade, and thermal runaway.

Innovation Solution

A novel electrolyte composition comprising lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide in a specific ratio, combined with a fluorinated phosphazene additive in a solvent blend of ethylene carbonate, ethyl methyl carbonate, and sulfolane, stabilizes lithium ions and suppresses electrochemical oxidation, enhancing battery performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional electrolyte compositions are used, then the electrolyte achieves basic ionic conductivity, but it suffers from electrochemical oxidation and capacity fade during cycling

Engineering Contradiction:

Improveelectrochemical stabilityVSAvoidbattery cycle life

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The fluorinated phosphazene additive acts as an intermediary substance that mediates between the lithium ions and the positive electrode surface. It forms a protective interface layer that prevents direct contact and oxidation reactions, thereby extending battery cycle life while maintaining ionic conductivity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The electrolyte uses a composite composition combining multiple lithium salts (lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide) with fluorinated phosphazene additive. This composite approach creates synergistic effects where the additive stabilizes the electrode interface while the salt mixture maintains conductivity, resolving the contradiction between stability and cycle life.

Inventive Principle:

Principle #40Composite materials

2Speed

If the electrolyte viscosity is reduced to improve ion mobility, then charging rate increases, but thermal stability and safety decrease

Engineering Contradiction:

Improveion mobilityVSAvoidthermal runaway risk

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The electrolyte optimizes the physical parameters of the solvent mixture (ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in specific ratios) to achieve a balanced viscosity that allows high ion mobility while maintaining adequate thermal stability. The fluorinated phosphazene additive further modifies these parameters by forming protective layers that enhance thermal runaway resistance without significantly impeding ion transport.

Inventive Principle:

Principle #35Parameter changes

3Power

If high concentrations of lithium salts are used to increase ionic conductivity, then battery performance improves, but direct current impedance increases

Engineering Contradiction:

Improveionic conductivityVSAvoiddirect current impedance

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent optimizes the concentration parameters of lithium salts (0.5-1.0 M lithium hexafluorophosphate and 0.1-0.5 M lithium bis(fluorosulfonyl)imide) to achieve the optimal balance between ionic conductivity and impedance. This parameter optimization ensures sufficient power delivery while minimizing harmful impedance effects.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The fluorinated phosphazene additive serves as an intermediary that modifies the electrode-electrolyte interface properties. It reduces interfacial impedance by forming conductive protective films, allowing higher lithium salt concentrations to be used without proportionally increasing harmful DC impedance, thereby improving overall power performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 electrolyte composition improves battery efficiency, longevity, and thermal stability, with reduced direct current impedance and lower risk of thermal runaway, while maintaining high capacity retention and recovery rates.

Implementation Method 1

disassociated lithium ions from the lithium bis(fluorosulfonyl)imide are stabilized by complexation with fluorinated phosphazene and sulfolane molecules

Methodology Applied

Scientific EffectComplexation:

Implementation Method 2

lithium ions liberated from the lithium bis(fluorosulfonyl)imide are stabilized by solvation with fluorinated phosphazene and sulfolane molecules

Methodology Applied

Scientific EffectSolvation: Solvation

Implementation Method 3

The electrolyte permeates a surface of the active material layer and suppresses electrochemical oxidation of the positive active material layer

Methodology Applied

Scientific EffectPermeation: Permeation

Data Source

PatentUS20250329787A1Electrolyte composition

Publication Date: 2025.10.23 FORD GLOBAL TECH LLC

AI summary

A lithium-ion battery with an electrode assembly is presented. The electrode assembly has a current collector and a positive active material layer on the current collector. The electrode assembly also has an electrolyte including lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide in a ratio of 0.8M to 0.2M and a 7 wt. % fluorinated phosphazene additive dissolved in a solvent mixture of ethylene carbonate, ethyl methyl carbonate, and sulfolane in a 25/73/2 volume ratio. The electrolyte permeates a surface of the positive active material layer to suppress electrochemical oxidation of the positive active material layer.