Innovative battery materials: it’s all about chemistry!

Abstract

Batteries are ubiquitous in our society and can be used in many applications, such as electric vehicles and stationary energy storage. Further progress in the development of batteries relies on the synergy between concepts from chemistry, physics and engineering. Creative chemical synthesis processes for the electrodes and electrolyte are a key factor in improving the functionality of battery technologies and pave the way toward a more sustainable future. This presentation will showcase a number of selected examples, where chemical approaches were used to improve the electrochemical performance and/or sustainability of current and upcoming battery chemistries. Although commonly used in lithium-ion batteries (LIBs), the mining, refining, and processing of cobalt causes a range of detrimental societal and environmental impacts. Therefore, extensive research was performed within the Horizon 2020 COBRA project to produce a positive electrode material for LIBs that does not contain any cobalt but still reaches a high energy/power density and cycle life at a competitive cost. In a different research path, core particles of positive electrode materials were coated with a shell of a material with high conductivity, thereby enhancing their energy and power density. The synthesis of core-shell particles can also enable an improved battery cycle life.1,2 Creative chemical approaches were also used to synthesize durable negative electrode materials for sodium-ion batteries (SIBs), making use of a carbothermal reduction reaction to form a phase which can otherwise only be formed in a cumbersome synthesis method.3 The electrolyte component of batteries should have a high conductivity for ions. Conventional electrolytes are highly flammable, limiting the safety of battery operation. To improve the safety, a nonflammable class of liquid electrolyte was developed for SIBs. The combination of experimental and computational studies allowed the optimization of the coordination structure of deep eutectic solvents (DESs) as viable electrolyte alternatives. They can offer a more durable electrochemical performance compared to conventional electrolytes.4 The development of solid electrolytes for battery applications may enable the safe use of metallic anodes, thereby offering the possibility to drastically improve the energy density. Therefore, DESs were incorporated into inorganic and polymeric backbone structures, compatible with high-energy density electrode materials. This new class of solid electrolyte for battery applications was termed eutectogel and consists of inexpensive and mechanically optimized electrolytes for next-generation solid-state batteries.5,6 This work was supported by Horizon 2020 LCBAT-5 COBRA project 875568 and by Research Foundation Flanders in several projects and mandates. Furthermore, the work received the support of the European Union, the European Regional Development Fund ERDF, Flanders Innovation & Entrepreneurship and the Province of Limburg (project 936). (1) Ulu Okudur, F. et al. Ti surface doping of LiNi0.5Mn1.5O4-δ positive electrodes for lithium ion batteries. RSC Adv. 8, p7287–7300 (2018). (2) Mylavarapu, S. K. et al. Effect of TiOx Surface Modification on the Electrochemical Performances of Ni-Rich (NMC-622) Cathode Material for Lithium-Ion Batteries. ACS Appl. Energy Mater. 4, p10493–10504 (2021). (3) De Sloovere, D. et al. Reduced Na2+xTi4O9/C Composite: A Durable Anode for Sodium-Ion Batteries. Chem. Mater. 30, p8521–8527 (2018). (4) De Sloovere, D. et al. Deep Eutectic Solvents as Nonflammable Electrolytes for Durable Sodium‐Ion Batteries. Adv. Energy Sustain. Res. 3, p2100159 (2022). (5) Joos, B. et al. Eutectogels: A New Class of Solid Composite Electrolytes for Li/Li-Ion Batteries. Chem. Mater. 30, p655–662 (2018). (6) Joos, B. et al. Polymeric Backbone Eutectogels as a New Generation of Hybrid Solid-State Electrolytes. Chem. Mater. 32, p3783–3793 (2020).