Fast-charging sodium batteries can be made possible through the co-intercalation method.
In a groundbreaking discovery, an international research team, led by Professor Philipp Adelhelm, has identified a new mechanism to boost sodium-ion diffusion in cathodes, addressing the sluggish kinetics and volume-change issues that often limit fast charging in traditional sodium-ion batteries. The team's findings, published in Nature Materials, offer a promising solution for the design of high-efficiency, fast-charging sodium batteries.
The key to this breakthrough lies in a process called co-intercalation, where sodium ions and solvent molecules are simultaneously inserted into cathode materials. This simultaneous insertion reduces energy barriers for ion movement, enabling faster charging.
Initially, co-intercalation was thought to cause detrimental volume expansion, or "breathing", that could shorten battery lifespan due to electrode swelling. However, certain cathode materials have been found to manage this volume change in a reversible and stable manner. By carefully selecting and designing cathode materials that accommodate co-intercalation without rapid degradation, batteries can achieve improved cycle life alongside fast charging capabilities.
The advantages of co-intercalation are significant. By enabling reversible and rapid storage and release of both sodium ions and solvent molecules simultaneously, this joint storage process allows for faster ion transport and charging/discharging kinetics, overcoming traditional limitations related to slow sodium-ion mobility.
The study, which incorporates detailed investigations from the last three years, was carried out by a team that explored a range of layered transition metal sulfides and identified co-intercalation processes in cathode materials. The results show that certain cathode materials offer a huge advantage: the kinetics are super-fast, almost like a supercapacitor.
Professor Adelhelm states that the process of co-intercalation could be used for developing very efficient and faster-charging batteries. The true beauty of co-intercalation reactions lies in their ability to offer a vast chemical landscape for designing novel layered materials for diverse applications.
The findings are the result of a collaborative effort from many talented people, including Dr. Yanan Sun, who carried out volume change measurements, structural analyses with synchrotron radiation, and electrochemical property investigations for a variety of combinations of electrodes and solvents.
The opportunities provided by the joint research group on operando battery analysis financed by Helmholtz-Zentrum Berlin and Humboldt-University were crucial in this research. The recently announced Berlin Battery Lab between HZB, HU and BAM will provide even more opportunities for joint research projects in Berlin.
The performance of batteries depends on how ions are stored in electrode materials and whether they can be released again. Co-intercalation is a process in which both ions and solvent molecules are stored simultaneously in cathode materials. Sodium ions migrate together with molecules from the organic electrolyte, a process known as co-intercalation.
This breakthrough in sodium battery technology marks a significant advance, potentially matching or surpassing lithium-ion battery performance benchmarks. Important parameters were identified that help predict co-intercalation reactions in the future, through the collaboration with Dr. Gustav Åvall. The results of the study on co-intercalation in cathode materials are published in Nature Materials.
Science and technology have been instrumental in the advancement of the new sodium-ion battery technology, as the breakthrough in co-intercalation processes has allowed for the identification of materials capable of fast charging and improved cycle life. By enabling simultaneous storage of sodium ions and solvent molecules in cathode materials, this innovative process offers a promising solution for designing high-efficiency batteries, potentially matching or surpassing lithium-ion battery performance benchmarks.
