Transition metal alloy-modulated lithium manganese oxide nanosystem for energy storage in lithium-ion battery cathodes

Autor: Natasha West, Kenneth I. Ozoemena, Priscilla G. L. Baker, Chinwe O. Ikpo, Emmanuel I. Iwuoha
Rok vydání: 2013
Předmět:
Zdroj: Electrochimica Acta. 101:86-92
ISSN: 0013-4686
DOI: 10.1016/j.electacta.2012.11.085
Popis: This paper explores the synergistic and catalytic properties of a newly developed lithium ion battery (LIB) composite cathode of LiMn 2 O 4 modified with bimetallic (Au–Fe) nanoparticle. Spinel phase LiMn 2 O 4 was doped with bimetallic nanoparticles, LiM x Mn 2− x O 4 (M = FeAu), with concomitant oxidation of the Mn 3+ ions (responsible for LIB capacity loss) to Mn 4+ . This nano-composite architecture accommodates the structural transformation that occurs during Li + ion charge and discharge. Ultra-low scan rate (0.01 mV s −1 ) cyclic voltammetry of the pure LiMn 2 O 4 cathode material in 1 M LiPF 6 /electrolyte solution, showed two sets of redox peaks with a third observed at lower potentials for LiM x Mn 2− x O 4 . The FeAu incorporation increased the reaction rate upon reduction of LiMn 2 O 4 as indicated by the enhanced reduction peak seen by cyclic voltammetry. Nyquist plots of the electrochemical impedance spectroscopy (EIS) results showed LiFeAu x Mn 2− x O 4 having increased conductivity with lower resistance of charge. X-ray diffraction studies showed the LiM x Mn 2− x O 4 material retained well-developed octahedral structures bounded by (111) planes. The material crystallite size was ∼10 nm with clear lattice fringes having a separation value of 0.48 nm which concurrently improved the diffusion rate of Li + . Solid-state NMR results showed the progressive increase in average nominal manganese oxidation state from +3.5 to +4 resulted in an increase in the super-transferred hyperfine field at the 7 Li nucleus of the FeAu doped cathode material. The LiFeAu x Mn 2− x O 4 material also showed improved cycleability, especially at high C rate. This improvement was due to the enhanced physical stability of LiMn 2 O 4 and its improved electrical conductivity ascribed to the incorporated FeAu nanoparticles.
Databáze: OpenAIRE
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