The Effects of Acid Treatment on the Electrochemical Properties of 0.5 Li[sub 2]MnO[sub 3]⋅0.5 LiNi[sub 0.44]Co[sub 0.25]Mn[sub 0.31]O[sub 2] Electrodes in Lithium Cells

Abstract

The electrochemical properties of 0.5 Li 2 MnO 3 •0.5 LiNi 0.44 Co 0.25 Mn 0.31 O 2 electrodes, when preconditioned and activated with acid for 2-24 h, have been studied in lithium cells. Powder X-ray diffraction data and electrochemical measurements provide supporting evidence for an intergrown, composite electrode structure from which Li 2 O can be leached from the Li 2 MnO 3 ͑Li 2 O•MnO 2 ͒ component with acid, thereby mimicking the electrochemical charge process at high potentials ͑Ͼ4.5 V͒. The MnO 2 -rich domains generated by acid treatment are reduced during electrochemical discharge at a lower potential than electrochemically generated MnO 2 -rich domains. With prolonged cycling between 4.6 and 2.0 V, dQ/dV plots of untreated and acidtreated electrodes develop similar, but not identical, character, suggesting a coalescence and redox interaction of the manganese ions in MnO 2 -rich and Ni 0.44 Co 0.25 Mn 0.31 O 2 regions of the structure. Acid treatment eliminates the first-cycle capacity loss of the electrodes, consistent with earlier reports for related systems, but it damages their cycling stability and rate capability.

The Role of AlF3 Coatings in Improving Electrochemical Cycling of Li‐Enriched Nickel‐Manganese Oxide Electrodes for Li‐Ion Batteries

“…The reduction peak at 3.2 V is not generally observed in the first discharge [3,4,21,24] and is believed to be mainly responsible for the high capacity in Li-enrich cathodes, which also appeared in the AlF 3 ). [17][18][19][20][21]24] We believe that the 3.2 V peak at the first discharge originated from the reduction of Mn 4+ ions led by facile activation of the AlF 3 -coated electrodes. The 10 wt% AlF 3 -coated electrode exhibited an oxidation peak at 4.18 V, which is normally observed in a spinel structure, instead of the peak at 4.05 V resulting from oxidation for Ni and Co ions.…”

“…voltage plateau around 4.5 V, which is related to the concomitant extraction of lithium and oxygen from the Li 2 MnO 3 host structure during the initial charging. [17][18][19][20][21] However, the plateau width decreased with increasing AlF 3 coating amount, and the 10 wt% AlF 3 -coated electrode had a very small charge plateau of only 47 mAh g −1…”

Li-rich layered cathode microparticle 0.4Li₂MnO₃·0.6Li(Mn_0.43Ni_0.36Co_0.21)O₂ decorated with nanosized grains

“…Small satellite peaks located at 22°( 2ª) are indicative of the formation of the Li 2 MnO 3 phase. 7), 28) In addition, the microparticles calcined at temperatures above 700°C exhibit diffraction peaks. However, the peaks of the microparticles calcined at 700°C appear to be highly disordered, given that some peaks are broadened.…”

Effects of the Fluorine-Substitution and Acid Treatment on the Electrochemical Performances of 0.3Li 2 MnO 3 ·0.7LiMn 0.60 Ni 0.25 Co 0.15 O 2 Cathode Material for Li-Ion Battery

“…In spite of this advantage, the flourine substitution affects to decrease the discharge capacity and to show large irreversible capacity. For improving the problem of large irreversible capacity on first cycle, it can be removed by chemical activation method [17]. The chemical preconditioning of Li 2 MnO 3 -LiMO 2 composites can leach the Li-ions from Li 2 MnO 3 component and eliminate the initial capacity loss resulting in higher discharge capacity.…”