Lithium Imidazolate Electrolyte for HF-Free Battery Safety
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Solution Overview
Problem
Existing lithium-ion battery electrolytes, such as lithium hexafluorophosphate, degrade into hydrofluoric acid gas, posing safety risks, and previous pentacyclic anion salts like lithium 1-trifluoromethyl-4,5-dicarbonitrileimidazolate and lithium 1-pentafluoroethyl-4,5-dicarbonitrileimidazolate have unidentifiable organic and inorganic impurities that can be detrimental to battery performance.
Innovation Solution
A composition of lithium salt of an imidazole compound with specific fluorinated alkyl groups and additional cations and anions, optimized to minimize impurities and ensure optimal electrolytic performance, including a production process involving treatment with activated carbon and recrystallization to achieve high purity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium hexafluorophosphate is used as electrolyte salt, then good conductivity and dissociation are achieved, but hydrofluoric acid gas is generated causing safety problems
Solution Approach 1:
The patent changes the chemical composition parameters by replacing LiPF6 with LiTDI (lithium 1-trifluoromethyl-4,5-dicarbonitrileimidazolate), which has different molecular structure and bonding characteristics. This substitution eliminates the phosphorus-fluorine bonds that decompose to form hydrofluoric acid, while maintaining strong carbon-fluorine bonds for stability and good ionic conductivity.
Solution Approach 2:
The patent extracts and removes the harmful phosphorus-fluorine bonding component from the electrolyte system by selecting an alternative lithium salt based on imidazolate anion with carbon-fluorine bonding, thereby eliminating the source of hydrofluoric acid generation while preserving the essential electrolyte functions.
2Reliability
If conventional purification methods are used for pentacyclic anion salts, then production is simplified, but organic and inorganic impurities remain that are detrimental to battery performance
Solution Approach 1:
The patent introduces preliminary purification actions before the final product is obtained. The synthesis process includes pre-treatment steps that prevent impurity formation or facilitate their removal, such as controlled reaction conditions and intermediate purification stages, ensuring high purity of the pentacyclic anion salt before battery assembly.
Solution Approach 2:
The patent employs intermediary substances or processes during purification, such as using specific solvents or adsorbents that selectively bind to impurities, allowing their removal while preserving the main product. This intermediary approach enables effective separation of organic and inorganic impurities from the lithium pentacyclic anion salt.
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 composition provides excellent Solid Electrode Interface (SEI) formation and retains battery capacity during charge-discharge cycles, with minimal impurities and improved safety characteristics.
Implementation Method 1
A first subject of the present invention is a pentacyclic anion salt composition which does not have the abovementioned drawbacks
Implementation Method 2
The electrolyte consists of a lithium salt dissolved in a solvent which is generally a mixture of organic carbonates
Implementation Method 3
these salts have very good conductivities of about 6 mS/cm, and a very good dissociation between the imidazolate anion and the lithium cation
Data Source
AI summary
A composition including: (i) a lithium salt of imidazole compound of formula (I): wherein Rf is a fluorinated alkyl group having 1 to 5 carbon atoms, or a fluorine atom; and (ii) at least one cation selected from the group A including sodium, potassium, calcium, iron, magnesium, manganese, strontium, vanadium, ammonium, silver, aluminium, arsenic, barium, silicon, cadmium, cobalt, chromium, copper, nickel, lead, antimony, selenium, tin, strontium and titanium; and (iii) at least one anion chosen from the group B including fluoride, chloride, nitrate, sulphate, phosphate, trifluoroacetate, pentafluoroacetate and the anion of formula (II), with all the cation(s) and anion(s) being more than 0 wt % and at most 1 wt % of the composition. Also, the preparation of the composition as well as to the use of the composition as a battery electrolyte.