Cathode material for MnO<sub>2</sub>-based chemical voltage sources with addition of lithium fluoride
Cathode material is the key factor determining the capacity, power, and price of lithium-ion batteries. Particle sizes and surface area of the cathode material determine the solid-phase diffusion resistance and the charge transfer reaction of the positive electrode in a lithium-ion battery. Thus, to create a battery capable of operating at high currents, the active material crystal sizes should be reduced. Our studies were aimed at improving the electrochemical characteristics of the LIB (Li/MnO2) by modifying the MnO2 electrode with lanthanum, which contributes to forming additional vacancies for moving the lithium ions within the cathode material structure and ensures an increase in the discharge current density and in the discharge duration, as well as improving the electrode cyclability. We have studied how the concentration of a lanthanium salicilate solution in DMF with lithium fluoride added affects the kinetics of introducing lanthanium and fluoride into the MnO2 electrode structure. Current-free chronopotentiometry results obtained on a LayMn1-yO2-δFδ electrode have shown that the highest value of currentless potential is reached at the LiF-salt concentration of 14 g/l. Results of potential dynamic sweeps have shown that, as the reaction products get accumulated, the value of ∆Е/∆I increases; however, after cycle 80, the process stabilizes and changes to the steady-state mode. Using the scanning microscopy methods, we have identified the compositions of the MnO2, LayMnO2, and LayMn1-yO2-δFδ electrodes and proven the vacancy-based mechanism of the introducing process. Within the range of 1-100 cycles, the capacity characteristics practically discontinue their changing and increase in the series of LiхMnO2хLayMn1-yO2хLayMn1-yO2-σFσ.