Original Computational Design of Ionic Liquid Electrolytes for Lithium-Ion Batteries Optimised for Tropical Climate Operation in Nigeria

The widespread adoption of lithium-ion batteries for electric mobility and off-grid energy storage in Nigeria demands electrolyte systems that perform reliably across tropical temperature ranges spanning 25 to 50 degrees Celsius, which expose conventional carbonate-based electrolytes to accelerated degradation, flammability risks, and reduced electrochemical stability. Ionic liquids, possessing negligible vapour pressure, high thermal stability, and tunable electrochemical windows, represent a promising electrolyte alternative, but the rational design of ionic liquid electrolytes optimised for tropical climate battery performance has not been undertaken through a systematic computational approach. This study developed an original computational framework for the design of ionic liquid electrolytes specifically optimised for lithium-ion battery operation under Nigerian tropical conditions. The framework integrated quantum chemical calculations, classical molecular dynamics simulations, and machine learning-assisted property prediction to screen a virtual library of 2,400 ionic liquid structures for combinations of target properties including electrochemical stability window, ion transport number, lithium solvation energy, viscosity, thermal decomposition temperature, and miscibility with lithium salts. Quantum chemical calculations at the MP2/aug-cc-pVDZ level computed fundamental electronic structure properties. Force fields were parameterised using RESP charges for molecular dynamics simulations spanning microsecond timescales. A gradient-boosted machine learning model was trained on the computed property dataset to enable rapid screening. Twelve optimal ionic liquid candidates were identified with predicted electrochemical stability windows above 4.5 V, lithium transference numbers above 0.4, and viscosities below 60 mPa.s at 40 degrees Celsius. Three prioritised candidates were synthesised using commercially available precursors and experimentally validated. This original computational design framework represents a contribution to battery materials chemistry applicable to the specific performance requirements of energy storage systems in the Nigerian tropical context.

Keywords: ionic liquid electrolytes, lithium-ion batteries, molecular dynamics simulation, tropical climate, computational design