As an integral part of its technological agenda, Russia is developing its own production of lithium-ion batteries. Despite the vast lithium reserves, battery production volumes fall short of the demand. Of special relevance is the development of high-energy-density batteries for electric cars. This challenge is addressed by both industry and science. In their new paper, researchers from Skoltech, in collaboration with colleagues from France, China, and other countries, are the first to reveal the roles of cobalt and nickel in the electrochemical properties of cathode materials. The research is available in the Nature Materials journal.
Today’s lithium-ion batteries use layered oxides of lithium, nickel, manganese, and cobalt as the active materials of the positive electrode (cathode). As nickel, manganese, and cobalt belong to the same category of 3d transition metals, their electronic structure and chemical properties are similar. They are homogeneously distributed within the crystal structure of layered oxides, which makes it very difficult to distinguish between their roles in the electrochemical properties of the cathode material.
To distinguish between the roles of nickel and cobalt, the researchers obtained two model compounds — a lithium-nickel-manganese oxide and a lithium-cobalt-manganese oxide — and closely examined their structure, composition, and electrochemical properties. A comprehensive investigation of these systems using various kinds of spectroscopy, electrochemical tests, and high-resolution transmission electron microscopy has enabled the team to compare the two layered oxides in terms of their local atomic structure, its evolution over the course of battery operation, and the interplay between the observable characteristics and mechanical stress, lithium intercalation and deintercalation, redox kinetics, etc.
“We conducted the study using the unique equipment of Skoltech’s Advanced Imaging Core Facility. It enabled us to examine the atomic structure of the materials for lithium-ion batteries. The goal was to collect data on how the local crystal structure of the materials evolves during battery operation. Such an investigation requires ultimate precision and rigor in preparing the sample, operating the equipment, and interpreting the data,” said Anatolii Morozov, a co-author of the study and a junior research scientist at the Skoltech Center for Energy Science and Technology.