Secondary Battery Electrolyte Composition for Reduced Electrolyte Volume

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Solution Overview

Problem

Decreasing the amount of electrolyte solution in secondary batteries leads to insufficient discharge capacity and inadequate cycle characteristics, as existing solutions fail to maintain discharge capacity during repeated charging and discharging.

Innovation Solution

An electrolyte solution containing a sulfonyl group-containing lithium salt and lithium nitrate, with a total concentration of 0.8 mol/L to 2.0 mol/L, and a solvent comprising a straight-chain ether and a fluorinated ether, which enhances discharge and cycle characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the amount of electrolyte solution is decreased to improve energy density, then energy density is improved, but discharge capacity becomes insufficient

Engineering Contradiction:

Improveenergy densityVSAvoiddischarge capacity

Core Design Contradiction:

Use of energy by moving objectVSQuantity of substance

Solution Approach 1:

The patent changes the chemical composition parameters of the electrolyte by introducing a specific composite electrolyte system containing lithium nitrate (0.1-1.0 mol/L), cyclic carbonate (10-40 vol%), chain carbonate (50-80 vol%), and cyclic carboxylate (5-20 vol%). This parameter optimization enables sufficient discharge capacity (≥70 mAh/mg Li) even with reduced electrolyte volume (EL/S ratio ≤10), resolving the contradiction between energy density improvement and discharge capacity maintenance.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If the amount of electrolyte solution is decreased to improve energy density, then energy density is improved, but cycle characteristics become inadequate

Engineering Contradiction:

Improveenergy densityVSAvoidcycle characteristics

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent employs a composite electrolyte system combining four components: lithium nitrate as electrolyte salt, cyclic carbonate (EC, PC) for solvation, chain carbonate (DMC, DEC, EMC) for conductivity, and cyclic carboxylate (GBL, GVL) for stability. This composite formulation with specific concentration ranges and volume ratios maintains excellent cycle characteristics (≥70% capacity retention after 50 cycles) while enabling reduced electrolyte volume for improved energy density.

Inventive Principle:

Principle #40Composite materials

3Use of energy by moving object

If conventional electrolyte composition is used with reduced amount, then energy density is improved, but discharge capacity remains insufficient

Engineering Contradiction:

Improveenergy densityVSAvoiddischarge capacity

Core Design Contradiction:

Use of energy by moving objectVSQuantity of substance

Solution Approach 1:

The patent optimizes multiple parameters simultaneously: lithium nitrate concentration (0.1-1.0 mol/L), cyclic carbonate volume ratio (10-40%), chain carbonate volume ratio (50-80%), and cyclic carboxylate volume ratio (5-20%). This multi-parameter optimization creates a highly efficient electrolyte system that achieves ≥70 mAh/mg Li discharge capacity even at EL/S ratios ≤10, conventional formulations cannot achieve this with reduced electrolyte amounts.

Inventive Principle:

Principle #35Parameter changes

4Use of energy by moving object

If conventional electrolyte composition is used with reduced amount, then energy density is improved, but cycle characteristics remain inadequate

Engineering Contradiction:

Improveenergy densityVSAvoidcycle characteristics

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent uses a four-component composite electrolyte system where lithium nitrate provides stable Li+ conduction, cyclic carbonates ensure solvation stability, chain carbonates maintain ionic conductivity, and cyclic carboxylates enhance interfacial stability. This composite formulation achieves ≥70% capacity retention after 50 cycles at EL/S ratios ≤10, whereas conventional single or dual-component electrolytes fail to maintain adequate cycle characteristics with reduced electrolyte volume.

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 solution maintains sufficient discharge capacity from initial discharging and retains capacity during repeated cycles, even with a reduced amount of electrolyte solution, improving energy density and battery performance.

Implementation Method 1

the electrolyte contains a sulfonyl group-containing lithium salt and lithium nitrate... a total content of the sulfonyl group-containing lithium salt and the lithium nitrate is 0.8 mol/L or more and 2.0 mol/L or less

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Implementation Method 2

the solvent contains a straight-chain ether and a fluorinated ether... provides sufficient discharge capacity from the initial discharging despite the decreased amount of the electrolyte solution

Methodology Applied

Scientific EffectSolvation: Solvation

Data Source

PatentUS20230395862A1Electrolyte solution, production method therefor, and secondary battery

Publication Date: 2023.12.07 MURATA MFG CO LTD

AI summary

An electrolyte solution for a secondary battery is provided and includes an electrolyte and a solvent, in which the electrolyte contains a sulfonyl group-containing lithium salt and lithium nitrate, a total content of the sulfonyl group-containing lithium salt and the lithium nitrate is 0.8 mol/L or more and 2.0 mol/L or less, and the solvent contains a straight-chain ether and a fluorinated ether.