The Effect of Particle Size on the Processes of Charging and Discharging of the LiFe0.97Ni0.03PO4/C/Ag Cathode Material

Abstract

Olivine-structured LiFe_0.97Ni_0.03PO₄/C/Ag nanomaterials of varying dispersibility are prepared by using sol–gel synthesis with subsequent milling. The materials are certified using X-ray diffraction analysis, scanning electron microscopy, low-temperature nitrogen adsorption, and electrochemical testing under the lithium-ion battery operating conditions. The LiFe_0.97Ni_0.03PO₄/C/Ag cathode material primary particles’ size was shown to decrease, under the intensifying of ball-milling, from 42 to 31 nm, while the material’s specific surface area increased from 48 to 65 m²/g. The discharge capacity, under slow charging–discharging (C/8), approached a theoretical one for all materials under study. It was found that under fast charging–discharging (6 C and 30 C) the discharge capacity is inversely proportional to the particles’ mean size. The discharge capacity under the 6 С current came to 75, 94, 97, and 106 mA h/g for the initial material and that milled at a rotation velocity of 300, 500, and 700 rpm, respectively. An increase in the lithium diffusion coefficient upon the samples’ intense milling is noted.