Water-Containing Battery Electrolyte for Safer High-Voltage Cells

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Solution Overview

Problem

Nonaqueous lithium secondary batteries face safety concerns due to the flammability of organic solvents used in their electrolyte solutions, and their production requires a dry environment, increasing costs. Additionally, the electrolyte solutions have low electrical conductivity, leading to higher internal resistance.

Innovation Solution

A secondary battery design that incorporates an electrolyte containing water, a lithium salt, and a phosphate ester, with water content between 150 ppm and 30,000 ppm, and lithium salts such as lithium bis(trifluoromethanesulfonyl) imide. This configuration suppresses reductive decomposition and enhances charge/discharge efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If an organic solvent electrolyte solution is used to achieve high electromotive force, then the battery can operate at 2V to 4.5V, but the safety deteriorates due to flammability

Engineering Contradiction:

Improveelectromotive forceVSAvoidsafety

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent changes the chemical composition parameters of the electrolyte by introducing water at controlled concentrations (150-30,000 ppm) and using phosphate esters instead of traditional organic solvents. This parameter change maintains the high electromotive force while fundamentally altering the safety profile by eliminating flammability through the use of non-flammable aqueous-based electrolyte composition.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If a dry environment is used during production to prevent moisture contamination, then the battery performance is maintained, but the production cost increases

Engineering Contradiction:

Improvebattery performanceVSAvoidproduction cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent inverts the conventional approach by designing an electrolyte system that is tolerant to moisture rather than requiring strict moisture exclusion. The aqueous-compatible electrolyte composition with phosphate esters and specific lithium salts is formulated to function optimally with controlled water content, eliminating the need for expensive dry room production facilities while maintaining battery performance.

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If the concentration of lithium salt is increased to suppress reductive decomposition, then water content is diminished, but the suppression effect is insufficient

Engineering Contradiction:

Improvesuppression of reductive decompositionVSAvoidwater content

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent employs a composite electrolyte system combining phosphate esters, water, and specific lithium salts (such as lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, or lithium bisoxalate borate). This composite material approach creates synergistic effects where the phosphate ester provides structural stability and the specific lithium salt combination delivers superior reductive decomposition suppression that cannot be achieved by increasing lithium salt concentration alone in traditional systems.

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 battery design achieves high charge/discharge efficiency by suppressing electrolysis at the negative electrode and forming a protective covering film, thereby improving safety and reducing production costs.

Implementation Method 1

reductive decomposition at the negative electrode is apt to occur, and thus, gas generation and cycle deterioration is apt occur

Methodology Applied

Scientific EffectReductive decomposition: Reduction

Implementation Method 2

forming a protective covering film

Methodology Applied

Scientific EffectFilm formation: Deposition (physical)

Implementation Method 3

electrolysis of the solvent hardly occurs

Methodology Applied

Scientific EffectElectrolysis: Electrolysis

Data Source

PatentUS20250030052A1Secondary battery, battery pack, vehicle, stationary power supply, and method of producing secondary battery

Publication Date: 2025.01.23 KK TOSHIBA

AI summary

According to one embodiment, a secondary battery including a negative electrode, a positive electrode, and an electrolyte is provided. The electrolyte contains water, a lithium salt, and a phosphate ester. The electrolyte contains the water in an amount of 150 ppm or more and 30,000 ppm or less in terms of mass. The lithium salt includes at least one selected from a group consisting of lithium bis (trifluoromethanesulfonyl) imide, lithium bis (fluorosulfonyl) imide, lithium difluorooxalate borate, lithium bisoxalate borate, and lithium triflate.