Solution Synthesis and Characterization of Lithium Manganese Oxide Cathode Materials

Abstract

A nonaqueous coprecipitation process has been developed to prepare controlled stoichiometry lithium manganese oxalate precipitates. The process involved mixing a methanolic Li-Mn nitrate solution with a methanolic solution containing tetramethylammonium oxalate as the precipitating agent. The resulting oxalates were readily converted to a variety of phase pure lithium manganese oxides at moderate temperatures (1600°C), where the phase formed was determined by the initial L i m n ratio in the starting solution. Metal cation dopants have been incorporated into the oxalate precipitate by dissolving the appropriate metal nitrate in the Li-Mn precursor solution The various starting solutions, oxalate precipitates, and calcined oxides have been extensively characterized using a variety of techniques, including 7Li NMR, TGAIDTA, SEM, and XRD. Results indicate that a strong interaction occurs between Li and Mn in the nitrate solution which carries over into the oxalate phase during precipitation. The morphology and the crystallite size of the oxide powders were shown to be controlled by the morphology of the oxalate precursor and the oxalate calcination temperature, respectively, The results of initial cathode performance tests with respect to dopant type (Al, Ni, Co) and concentration for LiMn204 are also reported.

Supertransferred Hyperfine Fields at7Li: Variable Temperature7Li NMR Studies of LiMn2O4-Based Spinels

“…Substitution of Mn by cations such as Ni, Li, Cr, and Al is believed to enhance the cycling stability of the electrode material. [4][5][6] Nickel-substituted LiMn 2-y Ni y O 4 has exhibited stable capacities on cycling, although nickel substitution results in a lower initial capacity due to the reduction in Mn 3+ content, 5,7,8 A recent powder X-ray diffraction study shows formation of a tetragonal Li 2 Mn 2 O 4 spinel upon Li + insertion into LiMn 2 O 4 , whereas on insertion of Li + into LiMn 1.5 Ni 0.5 O 4 to form Li 2 Mn 1.5 Ni 0.5 O 4 the spinel remains cubic. 8 The electronic structure of spinel oxides is also a sensitive probe of Jahn-Teller effects.…”

“…The search for materials that exhibit superior cycling performance to LiMn 2 O 4 has led to the study of transition-metal- and cation-substituted materials isostructural to LiMn 2 O 4 . Substitution of Mn by cations such as Ni, Li, Cr, and Al is believed to enhance the cycling stability of the electrode material. − Nickel-substituted LiMn 2 - y Ni y O 4 has exhibited stable capacities on cycling, although nickel substitution results in a lower initial capacity due to the reduction in Mn 3+ content, ,, A recent powder X-ray diffraction study shows formation of a tetragonal Li 2 Mn 2 O 4 spinel upon Li + insertion into LiMn 2 O 4 , whereas on insertion of Li + into LiMn 1.5 Ni 0.5 O 4 to form Li 2 Mn 1.5 Ni 0.5 O 4 the spinel remains cubic …”

Solvothermal Synthesis of Superfine Li1−xMn2O4−σ Powders

“…So, it is necessary to obtain submicron particles of uniform morphology with narrow size distribution and homogeneity. In order to improve the cycling performance, several low-temperature routes were developed such as sol}gel (6), coprecipitation (7), and the Pechini process (8). These methods show some improvement of the electrochemical properties of lithium manganese oxides, but some problems remain to be solved.…”

An Alternative Lithium Cathode Material: Synthesis, Characterization, and Electrochemical Analysis of Li8 ( Ni5Co2Mn ) O 16

“…A significant amount of this research has focused on the synthesis, 2-19 processing, 20-28 and/or electrochemical identification 23-25,29-37 of potential cathode (positive electrode) materials for use in these batteries. [38][39][40] Currently, several oxides are being considered for use as 4 V cathode materials for Li batteries: the spinel LiMn 2 O 4 and the layered oxide LiMO 2 (M ϭ Co and/or Ni). 1,41-49 Each of these cathode materials have advantageous and detrimental characteristics that have an impact on their further development for lithium-ion batteries.…”

“…[38][39][40] Due to the flexibility of this synthetic process, a wide range of cations were found to be easily and homogeneously incorporated into the precursor solution. Previously, we have reported the synthesis of LiMn 2 O 4 with capacity of ϳ80 mAh/g 38,40 and LiCoO 2 with a reversible capacity of ϳ133 mAh/g. 39 In this paper, we report on the synthesis and characterization of the four-cation oxide Li 8 (Ni 5 Co 2 Mn 1 )O 16 , synthesized using a modification of the existing solution-route process.…”