High Voltage LiNi 0.5 Mn 1.5 O 4 Cathodes for Li-ion Batteries Obtained by Sol-Gel Combustion Method -Effects of Fuel and Silver Doping

Abstract

High-voltage LiNi 0.5 Mn 1.5 O 4 (LNMO) cathode materials are highly needed for next generation lithium-ion batteries (LIBs). In this study, citric acid, glycine, and sucrose fuels were used to optimize the structural and electrochemical properties of LNMO materials obtained by the sol-gel combustion synthesis (SCS). The experimental results showed that the type of fuel used in the SCS influenced the enthalpy of combustion, crystallite size, morphology, cationic disorder and electrochemical property of the LNMO materials. The XRD results indicate that all the LNMO materials have a phase-pure spinel structure with Fd3m space group. The glycine fuel composition produced LNMO material (LNMO-G) with the least crystallite size, less cationic disorder and highest crystallinity compared to the citric acid fuel (LNMO-C) and sucrose fuel (LNMO-S) compositions. As a result, the LNMO-G cell gave the highest first discharge capacity of 115.83 mAh g -1 and retained 80.06% of the capacity after 200 cycles at a current density of 1 C. Also, the LNMO-G cell had the best rate capability compared to LNMO-C and LNMO-S cells, showing a discharge capacity of 60 mAh g -1 at a rate of 2 C between 3.50 -5.30 V. Furthermore, Ag-doping (LNMAO) improved the rate capability and Li ion kinetics of the LNMO-G cathode material. LNMAO cathode gave a reversible discharge capacity of 100 mAh g -1 at a rate of 2 C between 3.50 -5.30 V. These findings show that LNMO cathode material could be optimized for ultrahigh voltage (> 5.0 V) performance in LIBs for advanced applications.