Tuneable and Earth Abundant Solid-State Electrolytes for Li-ion Batteries

Rechargeable Li-ion batteries are becoming increasingly necessary in modern society, present in portable electronics, electric vehicles, in addition to paving the way for a fully renewable energy grid. A typical Li-ion battery consists of positive (cathode) and negative (anode) electrodes separated by a liquid electrolyte allowing Li-ions (charged lithium atoms) to shuttle between them. The liquid electrolyte is, however, typically very flammable and also limits the use of a high capacity anode such as pure Li-metal resulting in a reduced battery capacity (i.e. your phone charge doesn't last as long). An obvious solution is to use a solid electrolyte which would solve a lot of these problems, however, "obvious" is not so easy...a tradeoff exists between the ionic mobility/conductivity and stability of such a material. As one may imagine, trying to push a snooker ball through a brick wall is harder than through water, the same exists for atoms. Typically, solid electrolytes with highly mobile Li-ions struggle to be stable making fabrication and long term cycling difficult, whilst stable materials usually have low ionic mobility. "Tuneable and Earth-Abundant Solid-State Electrolytes for Li-ion Batteries ", TEASE, aims to solve this by predicting new materials that are both stable, have high Li-ion conductivity, and use sustainable Earth abundant elements. A way in which we can achieve this is through using tuneable materials. There are many ways in which we can make tuneable materials, for example: a) by changing the crystal structure (the way atoms arrange in 3D), b) inducing atom disorder (making new pathways for Li-ions), c) doping (adding small quantities of other elements), d) solid solutions (combining two similar materials with different properties). Developing these strategies is crucial to overcoming the current limitations of this technology and thus the TEASE project will help accelerate the realisation of all-solid state batteries.

Li-ion batteries are ubiquitous in modern society due to the advent of portable electronic devices, with ever-increasing demand powered by the transition to electric transportation and a renewable energy grid. The current technology is, however, approaching limitations regarding capacity, high voltages, long-term cyclability as well as concerns surrounding safety. Replacing the liquid electrolyte component in a Li-ion battery with a solid-state electrolyte has the potential to solve these issues. Despite this, high-synthesis costs, poor interfacial contacts, as well as trade-offs between stability and ionic conductivity exist in current solid-electrolyte materials. In this proposal we offer a new generation of Earth-abundant solid electrolytes based on silicon oxynitrates to tackle these problems to realise all solid-state batteries. In addition, tuneability strategies based on defect chemistry and dopability, order/disorder, solid solutions as well as crystalline vs amorphous behaviour will be explored from a fundamental level using state-of-the-art materials simulations. In tuning each aspect of the composition and structure of these materials, the trade-offs and limitations we have come to expect will be mitigated. Experimental verification of promising candidates will be performed alongside the computational work by the project partner: Prof. Daniel Rettenwander at NTNU who has over 11 years of experience working with the synthesis and characterization of solid electrolytes for Li-ion batteries.