Li-Ion Electrolyte Additive for Stable SEI at High Voltage
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Solution Overview
Problem
Li-ion batteries face capacity loss and instability at high voltages and elevated temperatures due to breakdown of the Solid Electrolyte Interface (SEI) layer, particularly when operated with high-voltage cathodes, necessitating improved electrolyte additives for stable and safe operation.
Innovation Solution
Incorporation of quaternary hexahydrotriazine ionic liquid compounds as additives in lithium-ion battery electrolytes, which form a stable SEI layer and enhance cycle life characteristics by combining with an aprotic organic solvent system and metal salts, along with additional additives to create a robust film on electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional carbonate-based electrolytes are used, then lithium ion transport is enabled, but SEI layer stability deteriorates at high voltages and elevated temperatures
Solution Approach 1:
The patent introduces quaternary hexahydrotriazine ionic liquid compounds with specific molecular structures containing triazine rings and ionic liquid moieties. These compounds fundamentally change the chemical composition and properties of the electrolyte additive, enabling formation of stable SEI layers at high voltages (above 4.35 V) and elevated temperatures where traditional carbonate-based electrolytes fail.
Solution Approach 2:
The electrolyte composition combines quaternary hexahydrotriazine ionic liquid compounds with traditional carbonate solvents and lithium salts, creating a composite electrolyte system. This composite approach leverages the benefits of both traditional electrolytes (ion transport capability) and ionic liquid additives (high voltage stability, thermal stability), resolving the contradiction between SEI stability and operating temperature range.
2Use of energy by moving object
If high-voltage cathodes are used, then energy density increases, but capacity loss increases due to SEI breakdown
Solution Approach 1:
The quaternary hexahydrotriazine ionic liquid compounds act as intermediary substances between the high-voltage cathode and the electrolyte. These compounds preferentially react with trace water and acids to form stable protective layers on the cathode surface, mediating the interaction between high-voltage cathodes and the electrolyte, thereby preventing direct harmful reactions that would cause capacity loss while maintaining high energy density.
Solution Approach 2:
The patent changes the chemical parameters of the electrolyte by introducing ionic liquid compounds with specific functional groups (triazine rings, quaternary ammonium/carbonium cations). These parameter changes enable the electrolyte to withstand higher voltages (above 4.35 V) without decomposing the SEI layer, thus maintaining cycle life stability while utilizing high-voltage cathodes for increased energy density.
3Reliability
If conventional electrolyte additives are used, then anode passivation is achieved, but high-temperature performance deteriorates
Solution Approach 1:
The patent creates a composite additive system using quaternary hexahydrotriazine ionic liquid compounds that combine multiple functional properties: anode SEI-forming capability, high-temperature stability, and high-voltage protection. This composite molecular structure maintains effective anode passivation while remaining stable at elevated temperatures, unlike conventional single-function additives that deteriorate under thermal stress.
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 quaternary hexahydrotriazine ionic liquid compounds improve high-voltage stability and cycle life of Li-ion batteries across a wide temperature range, reducing capacity fade and maintaining performance at elevated temperatures.
Implementation Method 1
the SEI (Solid Electrolyte Interface) layer formed on the anode is gradually broken down... the quaternary hexahydrotriazine ionic liquid compound additive... form a stable SEI layer
Implementation Method 2
triazine compounds have been added to electrolytes to remove acids and water from nonaqueous electrolytes
Implementation Method 3
The shuttling of positive and negative ions between the battery electrodes is the main function of the electrolyte
Implementation Method 4
to inhibit the oxidation reaction between electrolytes and cathode materials
Data Source
AI summary
A quaternary hexahydrotriazine ionic liquid compound additive useful for reducing battery resistance and improving cycle life stability and high-temperature performance; an electrolyte containing the quaternary hexahydrotriazine ionic liquid compound additive suitable for use in electrochemical energy storage devices; and an electrochemical energy storage device incorporating the electrolyte including the quaternary hexahydrotriazine ionic liquid compound additive are described.