Research

Battery recycling

Today lithium-ion batteries (LIB) are widely used. According to various estimates, the annual amount of LIB waste is ca. 200-500 million tons. Due to expected even more rapid growth of LIB production the battery recycling and “second life” became hot topics driven by both economic and environmental factors. However, recycling costs are high and a number of components cannot be recovered from a used battery. It is known that there are many reasons for the loss of battery capacity and power during its discharge/recharge cycling. We are developing the approaches to reuse part of the components from a degraded battery, and thus to minimize the cost of the rebuild lithium-ion cells.

In situ tools for electrochemical interfaces

The operation of all electrochemical energy-related systems depends largely on the processes occurring at electrochemical interfaces, where charge separation and chemical reactions proceed. The evolution of the structure and composition at the interface between electrodes and electrolytes affects all the device functional parameters. The analytical techniques capable of exploring the interfaces are still very limited, that leads to the loss of the important pieces of the puzzle and hinders the development of novel technologies, as the intermediates and electrochemical reaction products often can’t be “quenched” for post process analysis. The techniques capable of probing the electrochemical interfaces by photons and neutrons in operando have become the extensively growing field of research. We are aimed at development of new approaches and adaptation of photoelectron spectroscopy, x-ray absorption, vibrational spectroscopy, nuclear magnetic resonance, x-ray and neutron reflectometry for the electrochemical studies.

Metal-ion batteries with water-based electrolytes

Using aqueous electrolyte solutions in metal-ion batteries can greatly simplify the production and reduce the cost of such systems, as well as make them much more environmentally friendly. The general problem of aqueous electrolytes is oxygen and hydrogen evolution reactions on electrodes even in saturated solutions, which significantly limits the electrochemical window of such electrolytes, and thus lower the device specific energy. Example of lithium salts have already shown that varying the electrolyte composition (using combinations of various salts at high concentration, organic additives and creating “artificial SEI” on the electrodes) can significantly increase the electrochemical window of aqueous electrolytes. We are developing the electrolytes and electrode materials for aqueous sodium- and potassium-ion batteries using extremely cheap salts for electrolyte preparation.

Metallic lithium anodes

Electrochemical energy storage systems with a metallic lithium negative electrode are very attractive due to high specific capacity and the most negative electrode potential of lithium. Metal lithium electrode is widely used in primary (non-rechargeable) batteries, however, there are a number of problems that prevent its use in rechargeable systems. During electrodeposition of lithium it does not form planar and compact layers, but forms needle-like and spongy structures. Being deposited in this way, lithium may lose electric contact with the electrode during further dissolution, which would lead to irreversible loss of capacity. In addition, lithium “dendrites” can reach the opposite electrode, causing a short circuit and fire. We investigate lithium plating/stripping in various electrolyte systems paying attention to analysis of surface morphology and composition of solid-electrolyte interphase films.

Oxygen redox reactions

Electrochemical oxygen reduction and evolution reactions (ORR and OER) attract a great interest for decades. This mainly arises from the advantages of using oxygen-based redox couples for energy storage and conversion. The low molecular weight and high oxidative ability of oxygen provide potentially significant improvements to the key characteristics of batteries and fuel cells, namely specific capacity and working voltage. The Li-O₂ battery with aprotic electrolyte is one of the most promising electrochemical power sources in terms of specific energy that can theoretically reach up to 1 kWh/kg at cell level. Unlike fuel cell cathodes that contain ORR catalysts (mainly noble metals) providing direct 4-electron oxygen reduction to water, in Li-O₂ batteries 2-electron reduction to Li₂O₂ readily occurs on plain carbon electrodes. However, low discharge current densities and poor cycleability limits Li-O₂ battery development. The reason primarily lies in slow ORR/OER kinetics, complex multistep reaction pathways and numerous side reactions of discharge products and intermediates with cell components – electrodes, electrolytes and others. We actively study ORR/OER pathways, as well as electrode and electrolyte reactivity in order to suggest the ways for seeking of sustainable materials for metal-oxygen systems.

Solid state electrolytes and batteries

Today, a rising tide of interest in solid-state lithium ion conductors is induced by active development in two fields. First is all-solid-state lithium ion batteries associated with better safety in comparison with ones comprising liquid electrolytes. Another one is connected with research on lithium-sulfur and lithium-air batteries, which use metallic lithium as a negative electrode that should be protected from undesirable interactions with components diffusing through electrolyte, e.g. polysulphides in Li-S or oxygen in Li-air chemistries. One of the ways suggested for guarding lithium is utilization of solid Li⁺ conductive membranes which separate cathode and anode.
Variety of lithium conductive electrolytes has been reported during last two decades. We work with NASICON-type phosphates and garnet-type solid electrolytes for advanced lithium batteries. We work on preparation of thin ion-conducting membranes, measuring their electrochemical properties and testing them in all-solid, Li-S and Li-O₂ cells.