Fast and Scalable Synthesis of LiNi_0.5Mn_1.5O₄ Cathode by Sol–Gel‐Assisted Microwave Sintering

Abstract

High‐voltage spinel LiNi0.5Mn1.5O4 (LNMO) is a promising cathode material for high‐energy‐density and high‐power‐density lithium‐ion batteries (LIBs). The high cost of the currently available LIBs needs to be addressed urgently for wide application in the transport sector (electric vehicles, buses) and large‐scale energy storage systems (ESS). Of significance, herein, novel fast and scalable microwave‐assisted synthesis of LNMO is reported, which leads to a production cost cut. X‐ray diffraction (XRD) analysis confirms the formation of the desired phase with high crystallinity. Field emission scanning (FE‐SEM) and transmission electron microscopy (TEM) analyses indicate that the synthesized phase is of nanometric size (50–150 nm) due to an extremely short sintering time (20 min). The material synthesized at 750 °C shows a higher initial discharge capacity (130 mA h g−1) than that synthesized at 650 °C (115 mA h g−1). The materials heat treated at higher temperatures show better electrochemical performance in terms of initial capacity, rate capability, and improved cycling. The improved electrochemical performance of LNMO at 750 °C is attributed to the formation of a stable crystal structure, low charge transfer resistance at the electrode/electrolyte interface, high electrical conductivity due to the presence of a disorder structure, and improved ionic diffusivity.

Optimized Morphology and Tuning the Mn3+ Content of LiNi0.5Mn1.5O4 Cathode Material for Li-Ion Batteries

“…The XRD patterns revealed distinct well-matched peaks of the cubic spinel LiNi 0.5 Mn 1.5 O 4 phase (LNMO, ICDD/PDF4#01-080-2984) with the Fd-3m space group in addition to a trace amount of an impurity of the rock-salt Li 0.5 Ni 0.5 O phase (LNO, ICDD/PDF4#04-007-6739), which is typically present in LNMO [27]. The spinel and rock salt phases, which are commonly denoted as AB 2 O 4 and AB 2 O 3 , can be reversibly transformed by the following equations regarding the oxygen loss during synthesis [31]. Furthermore, studies have also demonstrated that the existence of this phase was due to the reduction in a part of the Mn in the LNMO from Mn 4+ to Mn 3+ during high-temperature calcination to maintain the charge balance, while the disordered phase is formed due to the loss of Li [32].…”

Scope and significance of transition metal oxide nanomaterials for next-generation Li-ion batteries

“…Instead of conventional calcination, microwave-based quick calcination was adapted for a fast and scalable synthesis approach. 123 Due to rapid calcination, the material is free from bulk agglomeration, with particle size distribution ranging from 50 to 150 nm. The D-700 material, as shown in Fig.…”

Surface Modification of High Voltage Spinel LiNi0.5Mn1.5O4 Cathode Material Manufactured via Co-precipitation

“…To improve the performance of LNMO, synthesis methods such as solid phase, sol-gel, molten salt, co-precipitation, and microwave synthesis have been developed. [10][11][12][13][14] Among these synthesis methods, co-precipitation is effective in preparing pure LNMO with high electrochemical performance because it allows the mixing of Ni and Mn sources at the atomic level. 15 Additionally, the spherical hierarchical particle morphology of LNMO provides an isotropic diffusion path between the particle bulk and the surface, which can reduce resistance.…”