Synthesis of Single Crystalline Spinel LiMn₂O₄ Nanowires for a Lithium Ion Battery with High Power Density

Abstract

How to improve the specific power density of the rechargeable lithium ion battery has recently become one of the most attractive topics of both scientific and industrial interests. The spinel LiMn2O4 is the most promising candidate as a cathode material because of its low cost and nontoxicity compared with commercial LiCoO2. Moreover, nanostructured electrodes have been widely investigated to satisfy such industrial needs. However, the high-temperature sintering process, which is necessary for high-performance cathode materials based on high-quality crystals, leads the large grain size and aggregation of the nanoparticles which gives poor lithium ion battery performance. So there is still a challenge to synthesize a high-quality single-crystal nanostructured electrode. Among all of the nanostructures, a single crystalline nanowire is the most attractive morphology because the nonwoven fabric morphology constructed by the single crystalline nanowire suppresses the aggregation and grain growth at high temperature, and the potential barrier among the nanosize grains can be ignored. However, the reported single crystalline nanowire is almost the metal oxide with an anisotropic crystal structure because the cubic crystal structure such as LiMn2O4 cannot easily grow in the one-dimentional direction. Here we synthesized high-quality single crystalline cubic spinel LiMn2O4 nanowires based on a novel reaction method using Na0.44MnO2 nanowires as a self-template. These single crystalline spinel LiMn2O4 nanowires show high thermal stability because the nanowire structure is maintained after heating to 800 degrees C for 12 h and excellent performance at high rate charge-discharge, such as 20 A/g, with both a relative flat charge-discharge plateau and excellent cycle stability.

Evaluating the performance of nanostructured materials as lithium-ion battery electrodes

“…20), synthesised by treating solvothermally prepared α-MnO2 nanowires with LiOH at reduced pressure, were single-crystalline in nature while their small diameter enabled accommodation of the large lattice parameter changes brought about by the cubic to tetragonal phase transitions. Larger diameter LiMn2O4 nanowires also showed good structural stability, maintaining their single-crystalline nature (as confirmed by selected area electron diffraction (SAED) analysis), even after 100 charge-discharge cycles [265]. Such results suggest that LiMn2O4 nanowires could represent the basis of potential high-power, high-rate Li-ion batteries.…”

“…Coupled with relatively low production costs and appreciable electrochemical performance at high discharge rates and elevated temperatures, LiMn2O4 is touted as a potential driver of future EV/HEV battery packs, notably against favourable LiFePO4 candidates [264]. Recent nanostructured morphologies of note include nanowires [265][266][267], nanorods [268][269][270][271][272], nanotubes [273], nanoparticles [269,[274][275][276] and ordered meso/porous electrodes [277,278]. Okubo et al [275] have demonstrated an important size-effect occurring in LiMn2O4 particles, confirming that bulk particle sizes are unable to achieve complete lithiation (up to Li2Mn2O4), due to their lower surface area.…”

“…Such size-effects could therefore account for the enhanced rate capability displayed by small diameter LiMn2O4 nanorods [270][271][272], and nanowires [265][266][267], which possess both high power and enhanced cycling ability. In particular, high-aspect ratio nanowires with mean diameters <10 nm and lengths of several µm, displayed large capacities at rates up to 75 C, and even to as much as 150 C [267].…”

Development of nanostructure control process in the solution for application to energy and environmental fields

“…6 was fabricated by heating process after flux reaction of Na 0.44 MnO 2 nanowire as the template. 32) Generally, the fabrication of cubic crystal nanowire is difficult because the crystal structure is not anisotropy but isotropy. By using the self-template method, interesting materials were fabricated.…”

Nanostructured Networks for Energy Storage: Vertically Aligned Carbon Nanotubes (VACNT) as Current Collectors for High-Power Li4Ti5O12(LTO)//LiMn2O4(LMO) Lithium-Ion Batteries

“…However, today's conventional LIBs still suffer from rather slow charging/discharging performance using conventional electrode materials such as, for instance, graphite as a typical anode material [3]. Therefore, in recent years, huge efforts were made to increase the rate capabilities of LIB by introducing new electroactive material classes e.g., spinel-structured materials such as Li 4 Ti 5 O 12 (LTO) and LiMn 2 O 4 (LMO) in a wide range of accessible nanostructures such as nanoparticles [4][5][6], nanotubes [7][8][9], nanowires [10,11], nanosheets [12][13][14], mesoporous materials [15][16][17] and many more. Although increasing rate capabilities were successfully achieved, it is well known that the electrochemical properties of the electrode materials do not play the only key role, the electrode and current collector interface architecture [18,19] are key as well.…”