Metal-nitrogen-hydrogen materials for solid state electrolytes

Currently, more energy is being consumed than ever before, so new energy storage devices must be developed to keep up with this demand. Most recently, there has been a push on making safer lithium ion batteries (LIBs), by using a solid state electrolyte (SSEs). The replacement of liquid electrolytes with SSEs removes safety risks, as liquid electrolytes are flammable, volatile and suffer from thermal runaway.

All of these issues, combined with incorrect charging or a damaged battery, can lead to an explosion, which has the potential to be catastrophic. Another issue liquid electrolytes face is the development of lithium dendrites when a lithium anode is used, which means anodes with less gravimetric and volumetric capacities are required to be used, as the dendrite would short circuit the system, stopping the battery from functioning.

SSEs are preferable for applications such as electric vehicles (EVs), as a higher standard of safety is required, so their non-flammable and dendrite-resistant properties are key.

In addition, high entropy materials (HEMs) have been investigated as new LIB materials, especially cathode and SSEs. For example, high-entropy oxides (HEOs) are being used as new cathode materials, because the structural cation disorder increases the stability and conductivity, similar to DRXs. But there has been a limited amount of HEMs with a majority (or only) anion disorder that have been reported, despite HEMs showing good promise in many applications.

A good candidate for an anion-doped HEM is lithium imide (Li2NH). It has shown promise as a hydrogen storage material and shows high ionic conductivity so has gained interest as a SSE. Li2NH has already shown that it can form an imide-amide solid solution and has also recently shown it can be doped with bromide and chloride anions (simultaneously and separately).

This project will explore doping of lithium imide with a range of anions including multi-anion mixtures, with the aim to develop more stable and higher conductivity electrolytes.