Investigation of β/γ-MnO2 in composite electrodes with carbon nanotubes in a redox reaction with lithium in a model accumulator

Abstract

Balastless thin-layer MnO2/Al electrodes without an electroconducting carbon additive in combination with multiwalled carbon nanotubes (MWCNT) MnO2/Al-MWCNT, as well as bulk-modified paste electrodes MnO2 (MWCNT) F4/18H12X9T stainless steel electrodes, have been studied in the redox reaction with lithium in a model accumulator on the basis of propylene carbonate (PC), dimetoxiethane (DME), and 1MLiClO4 and ethyl carbonate (EC), dimethylcarbonate (DMC), and 1M LiClO4 electrolytes. The window of the electrochemical stability of the anode oxidation on MnO2-Al/electrodes in the work range of the potentials for the electrolytes under study is 2.0–4.1 and 2.0–4.2 V, respectively. Because of the high contact resistance between the particles of the thin-layer β/γ-MnO2/Al electrode, its discharge capacity cannot exceed 110–120 mA h/g; however, it is stable through 180 cycles. The discharge capacity volume paste MnO2, F4/18H12X9T electrodes during the first cycle reaches 265–280 mA h/g and that of the reversible capacity ranges up to 185–250 mA h/g during the first 50 cycles. The role of the aluminum collector in the electrochemical transformation of MnO2 has been discussed in thin-layer MnO2/Al electrodes obtained by the mechanical rubbing of the active component into the aluminum matrix. The lithium chemical diffusion coefficient DLi established in the redox reaction of MnO2 with lithium has been estimated in thin-layer composite MnO2 MWCNT/Al electrodes at the current peak values (around 10−12 cm2/s) by slow cyclic voltammetry.