Talk2D - ‘Layered’ transition metal oxides as cathode materials for Na-ion batteries

11 June 2024 - presented by the ARC Research Hub for Advanced Manufacturing with 2D Materials (AM2D).

Talk by Amartya Mukhopadhyay
Advanced Batteries and Ceramics Laboratory, Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai, India

‘Layered’ transition metal (TM) oxides are a fascinating class of materials, whose properties can be suitably tuned in a variety of ways; such as, by selecting TM-ions/dopants having preferred electronic configurations, engineering the crystallographic site occupancy by dopants, controlling/modifying the degree of covalence of TM-O bonds, modifying lattice spacing(s), tuning phase assemblage etc.

Such modifications done from the fundamental perspectives influence the performances of TM-oxides for a variety of applications, including their widespread usage as cathode-active materials in alkali metal-ion batteries. In the context of the upcoming Na-ion battery system, O3-structured ‘layered’ Na-TM-oxides are promising as cathode-active materials due to their inherently high initial Na-content (as compared to the P2 counterparts); but suffer from instabilities caused due to multiple phase transformations during Na-removal/insertion and sensitivity to air/moisture.

Against this backdrop, by tuning the overall covalency of the cation-oxygen bonds in the TM-layer (which, in turn, influences the Na-O bond) and also with the help of a dopant having d0 electronic configuration (viz., no OSPE), we have been able to tune the composition and structural features to suppress the phase transitions upon Na-removal/insertion and improve the air/water-stability in significant terms; so much so that long-term cyclic stability has been achieved with health/environment-friendly ‘aqueous processed’ electrodes (sans, usage of toxic/expensive chemicals like NMP and PVDF) [J. Mater. Chem. A 8 (2020) 18064, Adv. Energy Mater. 13[19] (2023) 2204407]. The changes in structural features, which have led to such outstanding water-stability, include differential contraction/dilation of the Na-‘inter-slab’/TM-‘slab’ spacing and partial occupancy of the dopant at tetrahedral sites of the structure. The former aspect has also been invoked to enhance the Na-transport kinetics and, hence, the rate-capability of the, otherwise, inherently sluggish O3-structured NaTMO2-based cathode material [ChemComm 59 (2023) 4332]. Furthermore, in the context of the more ‘rate-capable’ P2-structured ‘layered’ Na-TM-oxide based cathode materials, but lacking in terms of having a lower starting Na-content (typically, 0.67-0.7 Na-ions p.f.u.), a universal strategy towards designing and developing high Na-containing P2-structured ‘layered’ Na- transition metal oxides has been evolved. This is based on increasing the average ‘charge:size’ ratio of the cation-combination in the TM-layer and concomitant TM-O bond covalency, resulting in lower effective negative charge on O-ions; and, in turn, rendering the prismatic coordination of O-ions around Na-ions more favourable even at higher Na-content.

Accordingly, by careful selection of the combination of non-TM-/TM-ions in the TM-layer, a high Na-containing (viz., ~0.84 p.f.u.) P2-type Na-TM-oxide has been developed, which, as a cathode material for Na-ion batteries, exhibits a high desodiation capacity of ~178 mAh/g (@ C/5; within 2-4 V vs. Na/Na+), exceptional cyclic stability pertaining to ~98% capacity retention after 500 galvanostatic desodiation/sodiation cycles @ 2.5C and also stability upon exposure to air/water [Chem. Mater. 34 (2022) 10470].


Biography:
Presently, Professor at the Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay (IITB), Amartya Mukhopadhyay completed his Doctoral in Materials Research from the University of Oxford, UK, in 2009. He did his post-doctoral Research at Brown University, USA, for a couple of years. He is a Young Associate of the Indian National Academy of Engineering (INAE) and served as the Honorary Secretary of Mumbai Chapter of the Indian Institute of Metals (IIM).

His research interests include materials, electrochemistry and cell fabrication for electrochemical energy storage; focusing on alkali metal-ion and metal-based batteries, such as Li-ion, Na-ion, solid-state batteries and beyond.

Among his major accomplishments, he has been awarded with the ‘SwarnaJayanti Fellowship 2020-21’, recognized by the Royal Society of Chemistry (UK) journals as one of the ‘2019 Emerging Investigators’, awarded with the 'IIT Bombay Research Dissemination Award 2018', 'INAE Young Engineer Award 2016', 'ASM-IIM North America Visiting Lectureship 2016', 'IIT Bombay Young Investigator Award 2014' and 'Dr. R. L. Thakur Memorial Award' by the 'Indian Ceramic Society' in 2013.

More details: https://sites.google.com/site/amartya..., https://www.iitb.ac.in/mems/en/prof-a..., http://htemlabiitb.wixsite.com/htem.