Abstract
Carbon-free LiFe0.5Mn0.5PO4 and carbon-coated LiFe0.5Mn0.5PO4/C cathode materials were prepared by the mechanochemically assisted solid-state synthesis. The influence of the carbon coating on the porous structure, morphology, conductivity, and electrochemical characteristics of the cathode materials was analyzed using scanning electron microscopy (SEM), standard contact porosimetry (MSCP), electrochemical impedance spectroscopy (EIS), galvanostatic cycling, and galvanostatic intermittent titration technique (GITT). It has been shown that the specific surface area of LiFe0.5Mn0.5PO4/C is twice as high as that of LiFe0.5Mn0.5PO4 despite the very low content of carbon (3%). This was explained by a non-additive contribution of carbon and the active cathode material to the total specific surface area of the composite due to an introduction of carbon in the pores of the cathode material. Among the two key characteristics of a porous structure—specific surface area and volumetric porosity—specific surface area has the greatest impact on electrochemistry of LiFe0.5Mn0.5PO4/C. Mathematical modeling of the discharge profiles of LiFe0.5Mn0.5PO4/C was carried out and compared with the experiment. The cathode heating at high currents was evidenced. The temperatures and coefficients of solid-state diffusion were estimated at different currents. The calculated diffusion coefficient corresponds to the experimental one obtained by GITT at room temperature.
Highlights
Special attention is paid to the improvement of the capacity and power characteristics of lithium-ion batteries
The particles of the LiFe0.5 Mn0.5 PO4 (LFMP) sample acquire a rod-like morphology, while they are noticeably smaller and have an irregular shape for the carbon composite LFMP/C indicating that the carbon additive acts as a surfactant during MA and inhibits the sintering of particles upon the subsequent heat treatment
It was shown that the porous structure influences their electrochemical properties
Summary
Special attention is paid to the improvement of the capacity and power characteristics of lithium-ion batteries. It has been shown that porosity can have a significant impact on the specific capacity of electrode materials and their cyclability, especially at high rates, due to better access of the electrolyte to the electrode surface and facilitating charge transfer across the electrode/electrolyte interface. It is believed that they can improve electrochemical characteristics, as they combine the advantages of both nano- and micron-sized materials and provide high-rate intercalation/deintercalation of lithium ions. Important parameters that determine the electrochemical properties of porous electrode materials are pore size distribution, uniformity of distribution, pore architecture, wall thickness, specific surface area, etc. The synthesis of a cathode material with a porous structure does not always guarantee the improvement of its electrochemical properties.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
