A Mechanochemical Route to Synthesize LiMn₂O₄ as a Cathode Material for Lithium Batteries

Abstract

Lithium manganate, LiMn 2 0 4 , applicable as a cathode material for lithium batteries has been synthesized by a redox mechanochemistry route. Gamma-Mn0 2 shows an excellent reaction ability with LiOH under grinding and the amorphous ground product can be crystallized to LiMn 2 0 4 at 400°C despite the requisition of the partial reduction of Mn0 2 to MnruMnrv0 5 • Contrary, Mn 2 0 3 shows a poor reactivity. The dissociation of the edge-sharing chains of Mn0 6-octahedra in yand ~-Mn0 2 and the increased reactivity of LiOH fused or activated under grinding is the proposed reaction mechanism. The ground products are slightly agglomerated by the moisture evolved from the hydroxide. However, the particle size can be controlled to be 300-500nm after the calcination at 800°C, when the grinding stress is limited not to be high. Unnecessarily high grinding stress induces the strong agglomeration to increase not only the size of agglomerates but the primary particle size. The synthesized LiMn 2 0 4 with the particle size of 3 70nm and the crystallite of 48nm provides the good cyclic charge-discharge characteristics, while the rechargeablity of LiMn 2 0 4 with 500nm and 68nm degrades within 3 cycles.

Mechanochemical reduction of manganese dioxide by grinding in organic vapors

“…The powders obtained from PH were smaller than PC; 153, 214 and 399 nm at the same temperatures. As described in a separate paper, 12) the fine powders prepared by the mechanochemical method indicate the excellent cycle performances for the rechargeability.…”

“…Mechanochemical process based on the enhanced chemical reactivity of finely ground and activated particles under grinding is expected as one of the candidate synthesis routes of inorganic powders. 1)-3) This process can be successfully applied to the synthesis of titanates, 4)-6) ferrites, 7)-11) manganates, 12) cobaltates, 13) and others. In these applications, the chemical valence (oxidation number) of the available starting materials is sometimes different from that of the desired products.…”

Mechanochemical/Solvothermal Synthesis of LiMn₂O₄ as a Cathode Material for Rechargeable Batteries

“…The MC treatment was conducted at the revolution frequency of 6 s −1 for 3h. For the solvothermal (ST) treatment, 20cm 3 of the mill-treated slurry was charged into the Teflon-lined stain-less steel container (50cm 3 ) and heated at 150 o C for 16h. The products were washed with acetone and dried at 85 o C under vacuum for precursors AHG00 (MC) and AHG15 (MC/ST).…”

“…The other is the reduction of particles size, expecting the high surface energy to stabilize surface defects [1]. Mechanochemical process is applicable to the reduction of particle size by promoting the nucleation [2,3]. The authors have been demonstrated the mechanochemical synthesis of LiMn2O4 from LiOH and MnO2, where the amorphous ground products are crystallized above 400 o C and the LiMn2O4 powder with the size of 380 nm shows a certain improvement of the cycle performance.…”