Optimization of the cathode porosity via mechanochemical synthesis with carbon black
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ORIGINAL PAPER
Optimization of the cathode porosity via mechanochemical synthesis with carbon black Nina V. Kosova 1 & Olga A. Podgornova 1 & Yury M. Volfkovich 2 & Valentin E. Sosenkin 2 Received: 24 August 2020 / Revised: 18 November 2020 / Accepted: 20 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Nanostructured carbon–coated composite cathode materials LiFe 0.5 Mn 0.5 PO 4 /C (LFMP/C) are prepared by the mechanochemically assisted solid-state synthesis using different reagent mixtures and carbon as reducing and covering agent. The effect of the precursors, gas release during the solid-state reaction, and of the intensity of high-energy ball milling on the porous structure and electrochemistry of LFMP/C is studied using DSC/TG/MS, XRD, SEM, TEM, standard contact porosimetry (MSCP), EIS, CV, and GVC. It is shown that the particle size and porosity of LFMP/C strongly depend on the chosen precursors and intensity of mechanical impact. The higher the intensity, the more effective incorporation of carbon black in the pores formed in LFMP, which leads to improved electronic conductivity and better access of the electrolyte to the surface of the electrode, while smaller particles provide improved Li diffusion in the bulk of LFMP. As a result, the cyclability and high-rate performance of the LFMP/C composites are improved. Keywords LiFe0.5Mn0.5PO4/C . Mechanical activation . Porous structure . Electrochemical cycling
Introduction Numerous applications are now putting increased demands on lithium-ion batteries (LIBs), calling for higher specific capacities and faster rate performance. Rate capabilities of LIBs can be improved by structuring the electrodes appropriately. The conventional approach to optimizing the power (rate) of an electrode is to reduce the particle size to a few nanometers, either using conductive carbon coating and doping. The application of porous electrodes, which offer important benefits, is currently being considered as another alternative route [1–5]. It is known that porosity significantly affects the mechanical, physical, and chemical properties of materials [5]. When applied to LIBs, the porosity increases the specific capacity of electrode materials and improves their high-rate capability due
* Nina V. Kosova [email protected] 1
Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch of the Russian Academy of Sciences, 18 Kutateladze, 630128 Novosibirsk, Russia
2
A.N. Frumkin Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences, 31-4 Leninsky Prospect, 119071 Moscow, Russia
to better charge transfer across the electrode/electrolyte interface [1–4]. It is considered that for organic electrolytes, mesoporosity is preferable than microporosity since electrolyte molecules cannot effectively move through too small pores. In addition, the diffusion rate of lithium in the porous electrode depends not only on the pore size and pore size distribution, but also on pore volume, specific surface area, etc.
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