Grand challenges and opportunities in next-generation batteries and technologies

The development of advanced Li-ion batteries and technologies generally addresses one of four objectives: 1) create a higher volumetric energy density and/or specific energy/ power, 2) impart intrinsically safer chemistry, 3) produce speedier charging, and 4) utilize less expensive batteries but with competitive/near-competitive performances. Certainly, other factors can play a role as well, dependent on the type of market targeted and the availability of global supplies; however, for widespread adoption, the above points/criteria remain salient. Li-ion is commercially well entrenched in industry for communication and transportation (EV) applications. Nowadays, slight iterations, mostly electrolytedefined, are incrementally improving safety, cost, and cycle or calendar life. The last point, calendar life, is one that is often overlooked for very high-energy dense Li-ion batteries, because of their reactivity at higher charge (OCV conditions) and elevated temperatures. While cycle life is debated with respect to capacity/energy performance decline, attempts to re-purpose the battery itself or recycle the internal chemical constituents at end of life have considerably grown in the field. Hopefully, energy-neutral processes are also considered in the recycling loop. Nevertheless, the energy storage arena is quite large, and this pursuit hinges on pushing the field in one of many directions, toward loftier objectives. The pursuit of next-generation batteries and technologies must thus delve deeper into new and novel chemistry and electrochemistry to create a world with a neutral, carbon-free environment, and one that is solely sufficient on energy-producing renewables such as the Sun and wind-derived means. The application of electricity and chemistry within our world is thus a 21st century opus. The introduction of sodium-ion batteries (SIB) onto the battery playing field has taught us the value of foreknowledge of non-aqueous (electro)chemistry spawned from Li-ion, which can speed up research directions and shorten development times. The growth in publications on SIBs has been great over the last 10 years, and this indeed represents a “Beyond-Li-ion” battery system approach; however, one of perhaps lower intrinsic energy density. Energy densities of SIB that approach 250Wh/kg, or equivalent to the best Li-ion batteries of today’s marketplace are not yet proven/discovered. However, modeling of battery packs does suggest lower costs of production and raw materials extraction as well as lower energy expended for material processing compared with Li-ion (in terms of cost/kWh). It will be interesting and certainly competitive if SIB can achieve costs below that of graphite/LFP (LiFePO4), yet possess equal energy density, life, performance, and safety. On paper this is easy to state, but the challenge is to show this comparison in the field. We look forward to continued development of new SIB cathode and anode materials’ phase space, new electrolytes, salts, and other SIB technologies and features that will draw interest in this quickly developing field. OPEN ACCESS