Synthesizing nanocrystalline LiMn2O4 by a combustion route

Li ion kinetic studies on spinel cathodes, Li(M1/6Mn11/6)O4 (M = Mn, Co, CoAl) by GITT and EIS

“…17 The fact that the unsubstituted LiMn 2 O 4 shows structural change on cycling at ambient temperature 1,7,9,18,20 but was not seen in the M-substituted spinels at 50 uC 16 is in accordance with the proposed structural stability of the material with doping. [5][6][7][8][9][10][11][12][13][14][15][16][17] Our recent studies 5 and those of Wakihara and co-workers 11,12 have shown improved cathodic performance of the doped spinels Li(M 1/6 Mn 11/6 )O 4 ; M~Co, (Co,Al), (Co,Cr) and (Cr,Al) at ambient temperature (27 uC) as well as at 50 uC (or 55 uC 11,12 ) and this was ascribed to their structural stability. In the present study, galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS) studies on the substituted spinels Li(M 1/6 Mn 11/6 )O 4 ; M~Mn, Co and (Co,Al) were carried out to determine the Li ion kinetics and hence to understand the factors which lead to their improved performance.…”

“…[1][2][3][4][5][6] To improve its cycling performance, especially at elevated temperature (¢50 uC), several approaches such as doping at the Mn site, surface modification, and various preparatory conditions have been shown to be successful. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] The partial substitution of Mn as Li(M,Mn) 2 O 4 , (M~Li, Co, Cr, Al, (Co,Al), (Co,Cr), Ni, Mg) at the 16d site is known to increase the average Mn-oxidation state, enabling the compound to be more tolerant to JahnTeller distortion, and an improved cathodic performance is observed. [5][6][7][8][9][10][11][12][13][14][15][16][17] The latter is also ascribed to the stronger M-O (M~Co, Cr, Al) bond strength compared to that of the Mn-O bond in the spinel structure.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] The partial substitution of Mn as Li(M,Mn) 2 O 4 , (M~Li, Co, Cr, Al, (Co,Al), (Co,Cr), Ni, Mg) at the 16d site is known to increase the average Mn-oxidation state, enabling the compound to be more tolerant to JahnTeller distortion, and an improved cathodic performance is observed. [5][6][7][8][9][10][11][12][13][14][15][16][17] The latter is also ascribed to the stronger M-O (M~Co, Cr, Al) bond strength compared to that of the Mn-O bond in the spinel structure. 5,[10][11][12][13][14] The observed reduction in the initial charge-discharge capacity proportional to the amount of the substituent M leads to the conclusion that the Mn 31 ions in the lattice are replaced and the M ion is electrochemically inactive in the voltage range of operation, 3.5-4.3 V vs. Li.…”

“…The fabrication of the positive electrodes by doctor-blade technique is described elsewhere, 5,25,26 using the active material, super P Carbon Black as conducting additive, Kynar 2801 as binder (wt.%, 80 : 8 : 12) and N-methylpyrrolidinone (NMP) as the solvent. Coin cells (size 2016) were assembled in the Ar-filled glove box (MBraun, Germany) with Li metal (Kyokuto Metal Co., Japan) as anode and 1 M LiPF 6 in ethylene carbonate (EC) 1 diethyl carbonate (DEC) (1 : 1 volume, Merck, Selectipur LP40) as the electrolyte. Chargedischarge cycling and CV tests were carried out with a potentiostat/galvanostat system (Mac-pile II, Bio-logic, France) and a Bitrode multiple battery tester (Bitrode, USA).…”

New nanocrystalline manganese oxides as cathode materials for lithium batteries: Electron microscopy, electrochemical and X-ray absorption studies

“…The decrease of particle size led to sub-micrometric powders ; in manganese oxide systems, several studies of such products as cathode materials were reported [13][14][15][16].…”