A theoretical study of different carbon coatings effect on the depolarization effect and electrochemical performance of LiFePO4 cathode

In this work, three categories of advanced carbon materials coated on current collector are investigated. The results indicate that carbon coating has a positive influence on the depolarization effect and electrochemical performance of LiFePO4 cathode, different carbon coatings have drastically different influences, high rates in particular. The depolarization effect and rate performance show the following order: Graphene nanosheets (GNs) > Carbon nanotubes (CNTs) > Activated carbons (ACs), and the differences of rate capacities among them become more and more obvious with increasing rates. Especially for 5C, the discharge capacities values are 122 mAh g− 1, 114.8 mAh g− 1, 106.8 mAh g− 1 and 49.2 mAh g− 1 for LFP-GNs-Al, LFP-CNTs-Al, LFP-ACs-Al and LFP-Al, respectively. The enhancement is attributed to the carbon coating acting as a transport system of electron between cathode materials and current collector, resulting in reducing the contact impedance within the electrodes, thus providing a favorable balance between fast ion diffusion and increased electron transport.