Impact of pore size on the transport properties of nanoporous LiNi₂O₄ spinel

Abstract

Nanostructuring of lithium-ion battery cathode materials is one of the most effective techniques for optimizing their electrochemical performance for large-scale applications such as electric vehicles. The partial substitution of Mn 3+ with Ni 2+/3+ in LiMn 2 O 4 spinel has shown improved rate-performance attributed to the increased Li + diffusion pathway due to the shortened M-O (M = Mn, Ni) average bond length, which sparked interest in the exploration of LiNi2O4 as a prospective cathode material for lithium-ion batteries (LIBs). In this study, the role of pore size on the transport properties of Li + in LiNi 2 O 4 is explored since the practical capacity and rate performance of lithium ion battery cathode materials are affected by transport properties such as diffusion and conductivity. The diffusion coefficients of lithium ions in LiNi 2 O 4 nanoporous structures with pore diameters of 1.1, 2.1, and 3.0 nm were found to be 7.99 x 10 -13 , 3.03 x 10 -12 , and 1.77 x 10 -9 cm 2 /s, respectively. Moreover, the ionic conductivity of lithium ions was also determined and found to be 1.25 x 10 -8 , 4.28 x 10 -8 , and 1.92 x 10 -5 S/cm. Therefore, ionic conductivity and diffusion increase with increasing pore size. Furthermore, a large surface area was observed for the nanomaterial with a larger pore size. A larger surface area offers high contact between the electrolyte and the cathode material, which yields high practical capacities. As such, high-rate capabilities and improved cycle performance can be achieved by increasing the pore size to determine optimal pore diameters of nanoporous cathode materials.