Microwave-assisted optimization of the manganese redox states for enhanced capacity and capacity retention of LiAl_xMn_2−xO₄ (x = 0 and 0.3) spinel materials

Abstract

Microwave irradiation at the pre-and post-annealing steps of the synthesis of LiAl x Mn 2Àx O 4 (x ¼ 0 and 0.3) spinel cathode materials for rechargeable lithium ion batteries is a useful strategy to optimize the average manganese valence number (n Mn ) for enhanced capacity and capacity retention. The strategy impacts on the lattice parameter, average manganese valence, particle size and morphology, reversibility of the deintercalation/intercalation processes, and capacity retention upon continuous cycling. Microwave irradiation is able to shrink the particles for improved crystallinity. The XPS data clearly suggest that microwave irradiation can be used to tune the manganese valence (n Mn ), and that the LiAl x Mn 2Àx O 4 with n Mn z 3.5+ gives the best electrochemical performance. These new findings promise to revolutionize how we use microwave irradiation in the preparation of energy materials and various other materials for energy storage and conversion materials for enhanced performance.

Solution-combustion synthesized aluminium-doped spinel (LiAl x Mn2−x O4) as a high-performance lithium-ion battery cathode material

“…Using the SEM images, the estimated particle size range for the compositions x = 0, x = 0.125, x = 0.25, x = 0.375, and x = 0.5, respectively, is 475 nm-2.2 lm, 200-525 nm, 200-800 nm, 300-800 nm, and 200-700 nm. The aluminium-doped samples are small in size compared with pristine LiMn 2 O 4 , in agreement with the literature report [14]. the Li movement by occupying the Li site resulting in unacceptable low capacity.…”

“…Some of the causes for the capacity fade of spinel cathode materials when used as battery materials include two-phase unstable reaction [5], dissolution of spinel into the electrolyte, and decomposition of the electrolyte in the 4 V region [6] and Jahn-Teller distortion in the 3 V region [7]. One of the strategies to retain capacity is by substitution of small amount of Mn ions by dopant ions such as Al, Ni [3,[7][8][9], and microwave irradiation [14]. It is believed that the dopant ions occupy the octahedral 16d sites of Mn ions in the spinel lattice and stabilize the spinel structure from lattice distortion.…”

“…Up to now, several solution synthesis methods have been used to synthesize pristine LiMn 2 O 4 spinel structure cathode material for rechargeable lithium-ion batteries, such as solgel method [10], emulsion-drying method [11], and combustion method [12,13]. However, there are few reports where Al-doped LiMn 2 O 4 is obtained using the solution combustion method [14]. The solution combustion method (SCM) allows for rapid synthesis of highly substituted oxides in a one-step process.…”

High-Voltage LiNi0.5Mn1.5O4-δSpinel Material Synthesized by Microwave-Assisted Thermo-Polymerization: Some Insights into the Microwave-Enhancing Physico-Chemistry

“…This result confirms microwave treatment reduces the particle size of the powders which is in consistence with previously reported results. 11,25 The HR-TEM images in Figs. 3e and 3f confirm both the samples are crystalline powders.…”

Insights into the Synergistic Roles of Microwave and Fluorination Treatments towards Enhancing the Cycling Stability of P2-Type Na0.67[Mg0.28Mn0.72]O2Cathode Material for Sodium-Ion Batteries

“…Our group has shown that microwave irradiation has the ability to improve the morphology and tune the concentration of the Mn 3+ that causes Jahn-Teller distortion and capacity fade in manganese oxide-based lithium-ion batteries. [30][31][32] Fluorination, on the other hand, has been found to improve the stability of electrode materials. [33][34][35][36] This work interrogates and clearly confirms the synergistic effect of the redox property-enhancing features of microwave irradiation and fluorination toward P2-type NaMgMnO material.…”