[1] Natl Univ Singapore, Dept Phys, Adv Batteries Lab, Singapore 117542, Singapore
[2] CSIR, Energy Mat Mat Sci & Mfg, ZA-0001 Pretoria, South Africa
[3] Natl Univ Singapore, Dept Mat Sci & Engn, Singapore 117576, Singapore
[4] Univ Witwatersrand, Sch Chem, ZA-2050 Johannesburg, South Africa
[5] Jain Univ, Ctr Nano & Mat Sci, Kanakapura 562112, Bangalore Rural, India