LiNi0.5Mn1.5O4 Spinel and Its Derivatives as Cathodes for Li-Ion Batteries

Abstract

IntroductionIt is well known that lithium-ion batteries are common in consumer electronics.It is one of the most popular types of rechargeable battery for portable electronics, with the best energy densities, no memory effect, and a slow loss of charge when not in use [1,2].Beyond consumer electronics, LIBs are also growing in popularity for military, electric vehicle, and aerospace applications.Its excellent properties originate from its materials including cathode, anode and electrolyte and so on.For cathode materials, there are mainly three kinds of materials which have been widely studied and applied commercially, including layered oxide LiCoO 2 , spinel LiMn 2 O 4 and olivine LiFePO 4 .Among the cathode materials, LiCoO 2 has been used since the invention of LIB [3], while LiMn 2 O 4 and LiFPO 4 are considered as promising ones due to less toxicity, low cost, more safety and good electrochemical properties [4,5].In term of redox energy level, these materials can be charged and discharged at around 4 V, which limits their energy density.The spinel LiNi 0.5 Mn 1.5 O 4 is becoming a research focus recently.The most remarkable property of spinel LiNi 0.5 Mn 1.5 O 4 is its discharge voltage plateau at around 4.7 V.In some cases, using LiNi 0.5 Mn 1.5 O 4 will lead fewer cells at the battery pack level.For example, hundreds of ordinary lithium ion batteries are needed to meet the requirement of electric vehicle (EV) in the state of start-up, accelerate and climb-up [6] because more energy is needed in this case.If the high voltage cells are utilized, the amount of batteries used for EV can decrease greatly.This chapter gives a detailed introduction on LiNi 0.5 Mn 1.5 O 4 spinel and the latest research advances in this area. Structures of LiNi 0.5 Mn 1.5 O 4There are two kinds of crystal structure for spinel LiNi 0.5 Mn 1.5 O 4 , i.e. face-centered spinel (Fd3m) and primitive simple cubic crystal (P4 3 32).For LiNi 0.5 Mn 1.5 O 4 with a face-centered structure (Fd3m), the lithium ions are located in the 8a sites of the structure, the manganese and nickel ions are randomly distributed in the 16d sites.The oxygen ions which are cubicclose-packed (ccp) occupy the 32e positions.For LiNi 0.5 Mn 1.5 O 4 (P4 3 32) with a primitive simple cubic structure, the manganese ions are distributed in 12d sites, and nickel ions in 4a sites.The oxygen ions occupy the 24e and 8c positions, while the lithium ions are located in the 8c sites.In this case, the Ni and Mn ions are ordered regularly [7][8][9].Whether LiNi 0.5 Mn 1.5 O 4 has a structure of face-centered spinel (Fd3m) or primitive simple cubic www.intechopen.com How to referenceIn order to correctly reference this scholarly work, feel