Siloxane-Modified Electrolyte for Low-Temperature Battery Discharge

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Solution Overview

Problem

Lithium ion secondary batteries face challenges in discharge characteristics at low temperatures and high output levels, with existing electrolytic solutions posing safety risks due to low-flash-point solvents and thermal runaway issues.

Innovation Solution

A non-aqueous electrolytic solution comprising a siloxane-modified polyoxyalkylene compound with (poly)organosiloxane structures at both ends, which enhances lithium ion migration and compatibility with electrolyte salts, improving temperature and high-output characteristics while ensuring safety.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If low-flash-point solvents like dimethyl carbonate and diethyl carbonate are used in electrolytic solutions, then the battery achieves good discharge characteristics, but safety deteriorates due to thermal runaway and ignition risks

Engineering Contradiction:

Improvedischarge characteristicsVSAvoidsafety

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent uses a composite electrolytic solution comprising multiple components: cyclic carbonate solvents (EC, PC), chain carbonate solvents (DMC, DEC), and a siloxane-modified polyoxyalkylene compound. This composite formulation combines the beneficial electrical conductivity and discharge characteristics of carbonate solvents with the thermal stability and safety improvements provided by the siloxane compound, resolving the contradiction between performance and safety

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent modifies the chemical structure parameters of the electrolyte by introducing a siloxane-modified polyoxyalkylene compound with specific molecular weight (500-5000) and composition ratios. This parameter change increases the flash point and thermal stability of the electrolytic solution while maintaining its ionic conductivity, thereby improving safety without sacrificing discharge characteristics

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If conventional electrolytic solutions are used, then the battery structure is simple, but discharge characteristics at low temperatures and high outputs deteriorate

Engineering Contradiction:

Improveelectrolytic solution compositionVSAvoiddischarge characteristics at low temperature and high output

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent optimizes specific parameters of the electrolytic solution including the molecular weight of the siloxane-modified polyoxyalkylene compound (500-5000), the ratio of cyclic to chain carbonate solvents, and the concentration of electrolyte salt. These parameter optimizations improve low-temperature fluidity and high-output ionic conductivity, enhancing discharge characteristics without excessive complexity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a composite electrolytic solution system that integrates cyclic carbonate solvents for high dielectric constant and ionic conductivity, chain carbonate solvents for low viscosity and good wetting properties, and siloxane-modified polyoxyalkylene compound for thermal stability and low-temperature performance. This composite approach achieves superior discharge characteristics across various temperature and output conditions

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 solution significantly improves discharge characteristics at low temperatures and high outputs, enhancing safety by facilitating smoother lithium ion migration and reducing the risk of thermal runaway.

Implementation Method 1

lithium ion secondary battery capable of charge/discharge operation by migration of lithium ions between positive and negative electrodes

Methodology Applied

Scientific EffectIon migration: Ion Repulsion/Attraction

Implementation Method 2

An improvement in safety is desired... the battery is improved in discharge characteristics both at low temperatures and at high outputs and in safety

Methodology Applied

Scientific EffectThermal stability: Thermal Insulation

Data Source

PatentUS7211353B2Non-aqueous electrolytic solution and secondary battery

Publication Date: 2007.05.01 SHIN ETSU CHEMICAL CO LTD

AI summary

A non-aqueous electrolytic solution is provided comprising a non-aqueous solvent, an electrolyte salt, and a siloxane-modified polyoxyalkylene compound having (poly)organosiloxane structures at both ends of polyoxyalkylene. A secondary battery using the same has improved temperature characteristics and high-output characteristics.