Lithium Salt Structure for Electrolyte Ionic Transference
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Solution Overview
Problem
Conventional lithium salts used in electrolyte solutions for lithium secondary batteries have low lithium ionic transference numbers due to limited Li ions in their molecular structures, and lithium phosphate salts with multiple Li ions suffer from low solubility, hindering the improvement of ionic transference numbers.
Innovation Solution
A lithium salt with a chemical structure represented by general formulas (1) and (2), containing three or two Li ions respectively, is synthesized using specific fluoroalkyl, alkyl, or phenyl groups, which can be used as a supporting salt in electrolyte solutions or solid electrolytes, enhancing ionic transference numbers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium phosphate salts with multiple Li ions (e.g., Li3PO4) are used to improve Li ionic transference number, then the Li ionic transference number can be improved, but the solubility to solvent becomes low
Solution Approach 1:
The patent changes the chemical structure parameters of lithium phosphate salts by introducing fluorinated alkyl groups (CF3) and adjusting the molecular composition to Li3-xPO4, which modifies the solubility characteristics while maintaining multiple Li ions per molecule, thereby resolving the contradiction between improving ionic transference number and maintaining solubility
Solution Approach 2:
The patent creates composite lithium salt structures combining phosphate groups with fluorinated alkyl chains (e.g., Li(CnF2n+1PO3CF3)2), which integrates the high Li ion content advantage with improved solubility through the fluorinated hydrocarbon chains, thus resolving the solubility-ionic transference number contradiction
2Quantity of substance
If conventional lithium salts (e.g., LiPF6, LiBF4) are used, then the solubility to solvent is high, but the Li ionic transference number becomes low
Solution Approach 1:
The patent merges the advantages of conventional lithium salts (good solubility) with lithium phosphate salts (high Li ion content) by creating hybrid structures where fluorinated alkyl groups provide solubility similar to conventional salts while the phosphate core provides multiple Li ions, thus simultaneously achieving high solubility and high ionic transference number
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 synthesized lithium salts improve the lithium ionic transference number in electrolyte solutions and solid electrolytes, overcoming the solubility issues of conventional lithium phosphate salts, enabling their use in various electrochemical devices.
Implementation Method 1
electrolyte solutions in which lithium salts are dissolved in nonaqueous solvents have been used as electrolyte solutions for lithium secondary batteries
Data Source
AI summary
A main object of the present invention is to provide a lithium salt which can improve its lithium transference number when used as a supporting salt of an electrolyte solution or the like. To attain the object, the present invention provides a lithium salt comprising a chemical structure represented by the following general formula (1):in which R1 to R3 may be same or different from each other and denote a fluoroalkyl group, an alkyl group or a phenyl group.