No abstract

A new synthetic method has been developed and demonstrated for the utilization of commercially cheap MnO 2 for the production of nanoparticles of LiMn 2 O 4 spinel as a cathode material for Li-ion batteries. The process involves the insertion of lithium into electrolytic manganese dioxide (EMD) in an aqueous medium with glucose as a mild reductant in open air. The material resulting from calcination is pure, spinel-structured Li 0.96 Mn 2 O 4 particles of sub-micrometric and nanometric size that exhibit promising electrochemical behavior in nonaqueous Li-salt solutions. Further development of this process may be interesting for the commercial production of LiMn 2 O 4 for Li-ion batteries.

Highly dispersed and non-agglomerated alpha-MnO(2) nano-needles of dimensions 20-30 nm have been synthesized by the application of ultrasound radiation on the aqueous solution consisting of manganese(3)acetate close to neutral pH followed by mild drying. With a similar reaction system, hot hydrolysis (non-sonochemical process) produced beta-MnO(2) nano-rods of length 100-200 nm but with high degree agglomeration. Sonochemical cavitation phenomenon is suggested to have a pronounced effect for the formation of special phase and morphology. The effect is proved by the difference in the intermediate products which has difference in crystalinity and phase-purity. The intermediate phases are identified to be single-phase gamma-MnOOH for the non-sonochemical reaction and mixture of gamma-MnOOH, alpha-MnO(2) and beta-MnO(2) for the sonochemical products.

A variety of manganese salts ranging from completely soluble and ionized to insoluble compounds have been subjected to ultrasonic radiation in aqueous medium at pH approximately 8.3. All of the manganese salts yielded a product identified as nanoparticles of Mn(3)O(4), expect for MnCO(3), which yields of mixture of phases. The characteristics of the products obtained are compared with those obtained under vigorous stirring conditions. The shapes of nanocrystals varied from sharp-edged crystals to smooth particles.