Electrochemical characteristics of xLi₂MnO₃-(1-x) Li(Mn_0.375Ni_0.375Co_0.25)O₂ (0.0 ≤ x ≤ 1.0) composite cathodes: Effect of particle and Li₂MnO ₃ domain size

We have investigated the electrochemical characteristics of a series of high capacity xLi₂MnO₃-(1-x)Li(Mn_0.375Ni _0.375Co_0.25)O₂ (0.0 ≤ x ≤ 1.0) integrated cathodes. Among several interrelated factors (viz. nominal molar content of Li₂MnO₃ and Li(Mn_0.375Ni_0.375Co _0.25)O₂ constituents, activation of Li₂MnO ₃ component, crystallinity of the particles etc) an optimum particle size is argued to be most critical to yield better electrochemical performance of the synthesized cathodes. Through X-ray diffraction in conjunction with micro-Raman spectroscopy and high resolution transmission microscopy analyses we have demonstrated that with the increase of nominal Li₂MnO ₃ contents, the size of the ordered nano-domains (inside the active matrix) and the average size of the composite cathode particles increase systematically. The size of the ordered nano-domains, cathode particles, and electrochemically triggered layer to spinel phase transformation influence the electrochemical characteristics of these cathodes. The average particle size of 0.5Li₂MnO₃- 0.5Li(Mn_0.375Ni _0.375Co_0.25)O₂ particles have been systematically varied by tuning the calcination time temperature combination. The optimized cathode yields a discharge capacity ∼ 300 mAhg^-1 with capacity retention about 96% after 50 charge-discharge cycles at 10 mAg^-1 rate. The cathode with optimal particle size also exhibits a decent rate capability with room temperature discharge capacity ∼ 200 mAhg^-1 at 300 mAg^-1 rate.