Asymmetric BF3 Complex Electrolyte for High Voltage Lithium Batteries
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Solution Overview
Problem
Conventional liquid electrolytes for lithium secondary batteries, particularly those using BF3 complexes, suffer from poor oxidation resistance and limited potential windows, which hinder the performance and longevity of these batteries.
Innovation Solution
An asymmetric type BF3 complex with an organic molecule that coordinates to boron, disrupting symmetry and preventing crystal formation, is used as a solvent, resulting in a liquid electrolyte with improved oxidation resistance and a wider potential window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbonate-based solvents are used as non-aqueous solvents in liquid electrolytes, then the electrolyte can be formed, but the oxidation resistance is poor
Solution Approach 1:
The patent changes the chemical composition parameters of the solvent system by introducing BF3 complex at specific concentrations (1-30 wt%) to alter the electrochemical stability and oxidation resistance of the liquid electrolyte
Solution Approach 2:
The patent creates a composite solvent system combining carbonate-based solvents with BF3 complex, where the BF3 complex acts as an additive that enhances oxidation resistance while maintaining the electrolyte's fundamental properties
2Temperature
If symmetric type BF3 complex is used, then the complex can be formed, but the melting point is high and crystal structure forms
Solution Approach 1:
The patent employs asymmetric organic molecules (such as esters with different alkyl groups) to coordinate with BF3, creating asymmetric complexes that disrupt crystal lattice formation and lower the melting point, enabling liquid state at operating temperatures
Solution Approach 2:
The patent modifies the molecular structure parameters of the coordinating organic molecule to achieve asymmetric geometry, which fundamentally changes the packing efficiency and intermolecular forces, resulting in lower melting points
3Reliability
If BF3 complex is used as an additive in small amounts, then capacity reduction is suppressed, but the potential window is not widened
Solution Approach 1:
The patent optimizes the concentration parameter of BF3 complex to a specific range (1-30 wt%) to simultaneously achieve capacity retention and potential window widening, moving beyond the traditional trace additive approach
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 asymmetric BF3 complex lowers the melting point and heat of fusion, enabling it to be used singularly or with minimal organic solvents, enhancing electrochemical stability and allowing lithium secondary batteries to operate at higher voltages with improved oxidation and reduction resistance.
Implementation Method 1
an organic molecule (ester) which coordinates to an unoccupied orbital of boron of BF3 has an asymmetric structure to a B—O binding
Data Source
AI summary
A main object is to provide an asymmetric type BF3 complex which is useful as a solvent for a liquid electrolyte for electrochemical device, in which the liquid electrolyte has a wide potential window and is particularly excellent in oxidation resistance. To attain the object, an asymmetric type BF3 complex is represented by the following general formula (1):(in the general formula (1), each of R1 and R2 is an alkyl group having 1 to 6 carbon atoms and may be the same or different, and R1 and R2 may be branched or may form a ring).