Lithium Battery Electrolyte Solvent Mixture for High Output

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Solution Overview

Problem

Existing lithium secondary batteries face challenges with low ionic conductivity due to high viscosity in carbonate solvents and poor cycle characteristics in lithium manganese oxides, making them unsuitable for high-output applications like hybrid electric vehicles.

Innovation Solution

An electrolyte comprising a non-aqueous solvent mixture of glyme and ether-based solvents, with a specific ratio of 20:80 to 60:40, and the inclusion of lithium metal phosphate as a cathode active material and amorphous carbon as an anode active material, enhancing lithium ion migration and dissociation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If carbonate based solvents are used as non-aqueous electrolyte, then the electrolyte can maintain stability in battery operation voltage range, but the ionic conductivity decreases due to increased viscosity

Engineering Contradiction:

Improvestability in battery operation voltage rangeVSAvoidionic conductivity

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent changes the chemical composition parameters of the non-aqueous solvent by replacing carbonate-based solvents with a mixture of ether-based solvent (20-60 vol%) and glyme-based solvent (40-80 vol%). This parameter change reduces viscosity while maintaining voltage stability, thereby improving ionic conductivity without sacrificing reliability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite solvent system by combining ether-based solvent and glyme-based solvent in specific ratios. This composite approach leverages the complementary properties of both solvents: ether-based solvents provide low viscosity and high ionic conductivity, while glyme-based solvents contribute to voltage stability and electrochemical window maintenance.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If LiCoO2 is used as cathode active material, then energy density and high-temperature characteristics are improved, but output characteristics deteriorate making it unsuitable for high output applications

Engineering Contradiction:

Improveenergy densityVSAvoidoutput characteristics

Core Design Contradiction:

Use of energy by moving objectVSPower

Solution Approach 1:

The patent changes the cathode active material from LiCoO2 to lithium transition metal phosphate (such as LiFePO4, LiMnPO4, LiCoPO4). This material parameter change fundamentally alters the electrochemical properties, providing both high energy density and superior output characteristics suitable for hybrid electric vehicles requiring high power delivery.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If lithium manganese oxides are used as cathode active material, then cost and availability are improved, but cycle characteristics deteriorate

Engineering Contradiction:

Improvecost and availabilityVSAvoidcycle characteristics

Core Design Contradiction:

Ease of manufactureVSDuration of action of stationary object

Solution Approach 1:

The patent uses lithium transition metal phosphate which can be viewed as a composite material system where transition metals (Fe, Mn, Co, Ni) are incorporated into the phosphate structure. This composite approach maintains cost-effectiveness (especially with Fe and Mn options) while the phosphate structure provides superior cycle stability compared to traditional lithium manganese oxides.

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 improves room- and low-temperature output characteristics, reduces internal resistance, and extends battery lifespan, making the battery suitable for high-performance applications such as hybrid electric vehicles.

Implementation Method 1

a non-aqueous electrolyte containing a lithium salt such as LiPF6 and the like thereinto. Lithium ions of a cathode active material are released and inserted into a carbon layer of an anode during charging, whereas lithium ions of the carbon layer are released and inserted into a cathode active material during discharging. In this regard, a non-aqueous electrolyte between an anode and a cathode functions as a medium in which lithium ions migrate.

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Implementation Method 2

As the non-aqueous electrolyte, existing carbonate based solvents were used. However, carbonate based solvents have problems such as decreased ionic conductivity due to increased viscosity. Therefore, there is an urgent need for technology to resolve the problems.

Methodology Applied

Scientific EffectViscosity reduction:

Data Source

PatentUS9666897B2Electrolyte for lithium secondary batteries and lithium secondary battery including the same

Publication Date: 2017.05.30 LG ENERGY SOLUTION LTD

AI summary

Disclosed are an electrolyte for lithium secondary batteries including a lithium salt and a non-aqueous solvent, in which the non-aqueous solvent includes an ether based solvent and a glyme based solvent and a ratio of the ether based solvent to the glyme based solvent is 20:80 to 60:40 based on the total volume of the non-aqueous solvent, and a secondary battery including the same.