Electrochemical Properties of Cu Doped Lithium Manganese Silicate/PANI Composite As Cathode Material for Lithium-Ion Batteries

Development of cathode materials for lithium battery application like electric vehicle (EV) and plug-in hybrid electric vehicle (PHEV) requires high capacity materials[1]. At the same time, cost, environmental concerns and safety issues cannot be excluded. Recently, lithium transition-metal silicates such as Li₂MSiO₄ (M=Fe, Mn and Co) have been extensively studied as cathode materials for lithium ion batteries, due to high theoretical capacity and better thermal stability than lithium transition metal oxides such as LiCoO₂. Among them, Li₂MnSiO₄ cathode could be a better choice as a high capacity( ~330 mAh/g) cathode for lithium ion batteries than Li₂FeSiO₄ cathode material. Due to Mn²⁺/Mn³⁺ and Mn^3+/Mn⁴⁺ redox couples, extraction of two lithium ions can be achieved from Li₂MnSiO₄. However, due to defects such as structure change after the first charge and low electronic conductivity(~ < 10^-14S/cm), this material has poor cycle performance and lower capacity than the theoretical prediction [2-3].

In this regard, the current work is aimed on the improvement of capacity and cycle stability of Li₂MnSiO₄ cathode active material by applying Cu doping and poly-aniline composites. The Li₂Mn_0.95Cu_0.05SiO₄were prepared using the sol-gel synthesis. PANI was synthesized by oxidative polymerization.

XRD patterns as shown in Figure 1 exhibit that the Cu doping and PANI composite does not contribute to structure change of Li₂MnSiO₄. From the cycle performances as shown in Figure 2, the Li₂Mn_0.95Cu_0.05SiO₄/PANI cell shows a high discharge capacity, as well as improved cycle retention compared with pristine Li₂MnSiO₄ material. Synthesis methodology of Li₂Mn_0.95Cu_0.05SiO₄/PANI materials along with their physical, morphological and electrochemical characteristics will be discussed in detail. 

References:

[1]      R.J. Gummow, N.Sharma, V.K.Peterson, Y.He, J. solid state chem., 188 (2012) 32–37.

[2]      R. Dominko, M. Bele, A. Kokalj, M. Gaberscek, J. Jamnik , J.  Power Sources., 174 (2007) 457–461.

[3]      D. M. Kempaiah, D. Rangappa, I. Honma, Chem. Commun., 48 (2012)  2698–2700.