Better Solid State Lithium Ion Batteries

Deakin materials scientists have proven that liquid solvent-free solid state batteries can easily be made which will enable safer batteries with higher energy density.

Joule – Poly(Ionic Liquid)s-in-Salt Electrolytes with Co-coordination-Assisted Lithium-Ion Transport for Safe Batteries

Highlights
• A solvent-free poly(ionic liquid)s-in-salt electrolyte is demonstrated
• A co-coordination-assisted Li + transport is proposed for enhanced transference number
• Lithium-metal batteries with high cathode loadings are demonstrated at 80°C

Summary
Polymer electrolytes are seen as key components for safe, high-energy-density all-solid-state lithium (Li) batteries, given their appropriate mechanical properties along with the absence of volatile and flammable solvents. Here, we report a class of solvent-free polymer electrolytes by using poly(diallyldimethylammonium) bis(fluorosulfonyl)imide (PDADMA FSI) and a high content of Li bis(fluorosulfonyl)imide (LiFSI) salt. A homogeneous mixture, with a Li + ion transference number of 0.56, is found at a 1:1.5 mole ratio of PDADMA FSI:LiFSI, whereas crystalline phases are observed at higher LiFSI contents. Molecular dynamics (MD) simulations indicate a co-coordination of the FSI anion with both the Li + and the polymer backbone, and this co-coordination is maximized at 1:1.5 mole ratio, which facilitates Li + transport. The optimized electrolyte has been demonstrated to support long-term stable Li-metal symmetrical cycling as well as Li-metal battery cycling (Li | LiFePO 4 and Li | Li 1/3Ni 1/3Mn 1/3CoO 2) at elevated temperature, with areal capacity higher than 1.1 mAh cm −2.