Ionic Liquid Electrolyte Rate Capability via Salt Concentration and Heating

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Solution Overview

Problem

Ionic liquid electrolytes in lithium-ion batteries suffer from poor performance at high charge and discharge rates due to their higher viscosity and lower ionic conductivity compared to organic electrolytes, leading to poor rate capability.

Innovation Solution

Increasing the concentration of lithium salt in the ionic liquid electrolyte and using ambient heating during cycling to improve the kinetic capabilities and overall cycling performance of ionic liquid electrolytes in lithium-ion batteries.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ionic liquid electrolytes are used in lithium-ion batteries, then safety is improved (non-flammable and non-volatile), but rate capability deteriorates (poor performance at high charge/discharge rates due to higher viscosity and lower ionic conductivity)

Engineering Contradiction:

ImprovesafetyVSAvoidrate capability

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent applies parameter changes by modifying the concentration of lithium salt in the ionic liquid electrolyte. Specifically, it uses high concentrations of lithium salt (e.g., 3.0 M LiFSI in PYR13FSI) to increase ionic conductivity and improve rate capability while maintaining the safety advantages of ionic liquids. This directly addresses the contradiction by changing a key parameter (lithium salt concentration) to enhance productivity without sacrificing reliability

Inventive Principle:

Principle #35Parameter changes

2Reliability

If high concentrations of lithium salt are used in ionic liquid electrolyte, then ionic conductivity is improved, but viscosity increases

Engineering Contradiction:

Improveionic conductivityVSAvoidviscosity

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent applies parameter changes by optimizing the lithium salt concentration to achieve high ionic conductivity (e.g., 3.0 M LiFSI provides sufficient conductivity) while managing viscosity effects. The patent demonstrates that with proper parameter selection, high conductivity can be achieved without viscosity becoming prohibitive for battery operation

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite materials by combining ionic liquid (PYR13FSI) with high concentration lithium salt (LiFSI) to create an electrolyte system that achieves both high ionic conductivity and acceptable viscosity. The composite nature of this electrolyte system allows it to overcome the limitations of pure ionic liquids

Inventive Principle:

Principle #40Composite materials

3Productivity

If ambient heating is applied during cycling, then kinetic capabilities are improved, but long-term stability may be affected

Engineering Contradiction:

Improvekinetic capabilitiesVSAvoidlong-term stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies preliminary action by implementing ambient heating during cycling to pre-condition the ionic liquid electrolyte and improve kinetic capabilities from the outset. This preliminary thermal treatment enhances ion transport and electrode kinetics, leading to improved rate capability and overall battery performance without compromising long-term stability

Inventive Principle:

Principle #10Preliminary action

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

Significantly enhances the rate cycling and long-term stability of lithium-ion batteries, particularly at high charge/discharge rates, while also mitigating dendrite growth in lithium-metal anodes, thus improving the performance of both anode and cathode materials.

Implementation Method 1

ionic liquid electrolytes form favorable passivation layers on many high-energy electrode materials, effectively protecting those materials from cycling-induced degradation

Methodology Applied

Scientific EffectPassivation:

Implementation Method 2

positioned adjacent to the ionic liquid electrolyte, the heating element is configured to heat the ionic liquid electrolyte to a temperature above room temperature

Methodology Applied

Scientific EffectThermal heating: Heating

Implementation Method 3

heating the ionic liquid electrolyte to a temperature above room temperature improves the kinetics of the battery

Methodology Applied

Scientific EffectThermal reduction of viscosity:

Data Source

PatentUS20220006124A1Methods of improving performance of ionic liquid electrolytes in lithium-ion batteries

Publication Date: 2022.01.06 THE REGENTS OF THE UNIVERSITY OF COLORADO

AI summary

Methods of improving the performance of an energy storage device are described. The method can include providing an energy storage device, which may be a lithium ion battery. The provided energy storage device may include an electrode and a room temperature ionic liquid electrolyte. The room temperature ionic liquid electrolyte may include a lithium salt, wherein the concentration of the lithium salt in the room temperature ionic liquid is greater than 1.2M, such as from 2.4M to 3.0M. The method may further include charging and discharging the provided energy storage device. Other methods described include providing an energy storage device comprising an electrode and a room temperature ionic liquid electrolyte, heating the energy storage device to a temperature above ambient temperature (e.g., 45° C.) and charging and discharging the energy storage device. Still other methods include both the use of the high lithium salt concentration room temperature ionic liquid electrolyte and heating the energy storage device.