Improvement of electrochemical performance of LiMn2O4 composite cathode by ox-MWCNT addition for Li-ion battery

Abstract

Nanotubos de carbono de multi-paredes oxidados (ox-MWCNT) foram utilizados como condutores adicionais para preparar uma nova rede de cátodos para bateria de íons de lítio. A morfologia foi analisada pelo microscópio de varredura eletrônico, e partículas ativas de LiMn 2 O 4 foram ligados ao ox-MWCNT com a formação da rede tridimensional de fiação. O transporte de elétrons e a atividade eletroquímica foram melhorados de forma eficaz. Testes galvanostáticos de carga-descarga do cátodo LiMn 2 O 4 /ox-MWCNT mostrou que a capacidade de descarga inicial são 119,4, 110,6, 105,5 e 91,4 mAh g -1 à taxa de 0,1, 0,5, 1 e 2 C, respectivamente, os quais são muito superiores aos de LiMn 2 O 4 /acetileno (AB), de mesmo conteúdo. A espectroscopia da impedância eletroquímica AC mostrou que a resistência da transferência de carga (R ct ) do eletrodo composto reduziu de 34,32 Ω para LiMn 2 O 4 /ox-MWCNT, em comparação ao valor de 53,2 Ω para LiMn 2 O 4 /AB. De um modo geral, se verificou que uma rede condutora para facilitar a transferência de elétrons e fazer uma boa conexão das partícula ativas com o material da rede desempenham um papel importante para avaliar a capacidade e eficiência do ciclo.Oxidized multi-walled carbon nanotubes (ox-MWCNT) were used as conducting addition to prepare a novel network composite cathode for lithium ion battery. The morphology was analyzed by scanning electron microscope, LiMn 2 O 4 active particles were connected by ox-MWCNT with the formation of three-dimensional networking wiring. Electron transport and electrochemical activity were improved effectively. Galvanostatic charge-discharge tests of LiMn 2 O 4 /ox-MWCNT cathode showed that the initial discharge capacities are 119.4, 110.6, 105.5 and 91.4 mAh g -1 at the rate of 0.1, 0.5, 1 and 2 C, respectively, which were much higher than LiMn 2 O 4 /acetylene black (AB) at the same content. The electrochemical AC impedance spectroscopy showed that the charge transfer resistance (R ct ) of the composite electrode reduced obviously contrasting to 34.32 Ω for LiMn 2 O 4 /ox-MWCNT and 53.2 Ω for LiMn 2 O 4 /AB. Overall, it is found that a conductive network to facilitate electron transfer and good connection of the active-material particle to the network were playing an important role to rate capability and cycle efficiency.

Template Synthesis, Structure, Morphology and Electrochemical Properties of Mesoporous Titania

“…The presence of the only one kinetic process during discharge was determined. Diffusion coefficients, calculated accordingly to [6], decline exponentially with the increasing of intercalation degree in a range of 110 8 -210 11 cm 2 /s.…”

Rutile Nanorods: Synthesis, Structure and Electrochemical Properties

“…Diffusion coefficients of Li + ions (Fig. 5) were calculated as described in (Liu et al, 2008). The presence of two kinetic processes with different time constants at the first stage of discharge was fixed.…”

Effects of Surface-Film Formation on the Electrochemical Characteristics of LiMn[sub 2]O[sub 4] Cathodes of Lithium Ion Batteries

“…Due to these reasons, it is customary in EIS studies of Li ion battery electrodes to use the geometric surface area of the electrode ͑without accounting for the roughness factor͒ for a simple order of magnitude estimation of . 22,50,[59][60][61][62][63][64][65][66][67][68] This latter approach was adapted in the present work, and Fig. 11 shows the results for obtained by using the geometric surface area of the LMO cathode in the CNLS analysis of the experimental Nyquist plots.…”

“…The expansion/contraction of the host lattice during intercalation/deintercalation can also introduce E-dependent uncertainties in the estimation of the electrode area. 26 Therefore, while using the apparent electrode area in the calculations, it would be preferable to treat the resulting value of D ˜as an apparent chemical diffusion coefficient, 64 and the observed x ͑or E͒ dependence of D ˜in such cases would only be appropriate within the framework of the specific experimental conditions used. We take this latter approach here to discuss the results for D ˜because, as mentioned in the context of Fig.…”