Low-Melting Electrolyte Additive for Lithium Battery Low-Temperature Conductivity

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Solution Overview

Problem

Rechargeable lithium batteries face challenges with discharge characteristics at low temperatures, safety, reliability, and cycle-life due to high viscosity and low temperature performance issues with conventional organic solvents, leading to frozen electrolytes and decreased capacity.

Innovation Solution

A non-aqueous electrolyte comprising a lithium salt, a solvent with a low melting point (≤ -50°C) and high ionic conductivity (≥ 6mS/cm), and tris(trialkylsilyl) borate as an additive, which improves ionic conductivity and forms a stable layer on active materials, preventing freezing and enhancing discharge capacity at low temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If conventional organic solvents (PC, EC, DMC) are used in electrolyte, then high dielectric constant and lithium salt dissolution capability are achieved, but high viscosity and poor low temperature performance occur

Engineering Contradiction:

Improvelithium salt dissolution capabilityVSAvoidlow temperature performance

Core Design Contradiction:

Quantity of substanceVSTemperature

Solution Approach 1:

The patent changes the physical and chemical parameters of the electrolyte by introducing solvents with low melting points (≤-50°C) and high ionic conductivity (≥6mS/cm at 25°C), replacing conventional high-viscosity solvents. This parameter change enables the electrolyte to maintain liquid state and high conductivity at low temperatures while still dissolving lithium salts effectively

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite electrolyte system by combining solvents with low melting points and high ionic conductivity with lithium salts and additives. This composite approach integrates the advantages of low-temperature fluidity with high lithium salt dissolution capability, resolving the contradiction between temperature performance and dissolution capability

Inventive Principle:

Principle #40Composite materials

2Temperature

If solvents with low viscosity are used to improve low temperature performance, then low temperature characteristic is enhanced, but dielectric constant decreases and lithium salt dissolution capability is reduced

Engineering Contradiction:

Improvelow temperature characteristicVSAvoidlithium salt dissolution capability

Core Design Contradiction:

TemperatureVSQuantity of substance

Solution Approach 1:

The patent identifies and utilizes solvents with the specific parameter combination of low melting point (≤-50°C) and high ionic conductivity (≥6mS/cm at 25°C). This precise parameter selection enables the solvent to simultaneously provide low-temperature fluidity and high lithium salt dissolution capability, breaking the traditional trade-off between viscosity and dielectric constant

Inventive Principle:

Principle #35Parameter changes

3Reliability

If electrolyte solution is reduced to form protective layer on carbon surface, then battery safety is improved, but irreversible capacity increases and discharge capacity decreases

Engineering Contradiction:

Improvebattery safetyVSAvoiddischarge capacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent changes the chemical composition parameters of the electrolyte by introducing solvents with specific low melting points and high ionic conductivity. These parameter changes modify the reduction behavior of the electrolyte on carbon surfaces, enabling the formation of protective layers with optimized properties that balance safety and capacity retention

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses additives that replicate or enhance the protective function on carbon surfaces while maintaining higher discharge capacity. The additives create model protective layers that prevent excessive electrolyte reduction while preserving battery safety, effectively copying the protective function with improved capacity characteristics

Inventive Principle:

Principle #26Copying

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 enhances discharge characteristics, safety, reliability, and cycle-life of rechargeable lithium batteries by maintaining conductivity and capacity at low temperatures, preventing freezing and internal resistance, and improving long-term performance.

Implementation Method 1

a solvent having a low melting point of less than or equal to (about) -50°C... preventing freezing

Methodology Applied

Scientific EffectFreezing point depression: Freezing

Implementation Method 2

ionic conductivity of greater than or equal to (about) 6mS/cm at 25°C... maintaining conductivity at low temperatures

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Implementation Method 3

tris(trialkylsilyl) borate as an additive... forms a stable layer on active materials, preventing freezing and enhancing discharge capacity

Methodology Applied

Scientific EffectSurface film formation: Deposition (physical)

Data Source

PatentEP2704244B1Electrolyte for rechargeable lithium battery and rechargeable lithium battery including the same

Publication Date: 2018.05.16 SAMSUNG SDI CO LTD

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AI summary

Disclosed are a non-aqueous electrolyte for a rechargeable lithium battery and a rechargeable lithium battery including the non-aqueous electrolyte. The non-aqueous electrolyte for a rechargeable lithium battery includes a lithium salt; a non-aqueous organic solvent; and trialkylsilyl borate as an additive, wherein the non-aqueous organic solvent includes a solvent having a low melting point of less than or equal to about -50°C and a ionic conductivity of greater than or equal to about 6S/cm at 25°C.