Hierarchical functional layers on high-capacity lithium-excess cathodes for superior lithium ion batteries.

Abstract: Li-excess layered Li[Li0.2Mn0.54Ni0.13Co0.13]O2 (LMNCO) nanoparticles are facilely synthesized using a surfactant-assisted dispersion method. Ultrathin and conformal oxide coatings are deposited on the surface of individual LMNCO nanoparticle via atomic layer deposition (ALD). The effect of oxide ALD coatings on improving electrochemical performance of LMNCO electrodes is evaluated and optimized via tuning the coating thickness and composition. In addition, we synthesize a novel core–shell structure cathode consisting of Li-excess LMNCO as core and Li-stoichiometric material as shell, and its electrochemical property is optimized by tailoring weight content and composition of shell materials. Finally, electrochemical performance of Li-excess cathode material can be maximized by surface modification with hierarch functional layers composed of 10 wt.% LiCoO2 shell (∼10 nm thick) and 6ZrO2 ALD layers (∼1 nm thick), which delivers very high initial discharge capacities of 296.4, 259.8, 156.6 and 104.2 mAh g−1 at 0.1C, 1C, 5C and 10C, and can retain 184.0 mAh g−1 at 1C after 100 electrochemical cycles. Such remarkably improved cycleabilitiy and rate capability of nanoarchitected Li-excess layered cathode material can be attributed to the synergic effect from hierarchical functional coatings to reduce electrochemical polarization, structural degradation and side reactions during electrochemical cycling. [Copyright &y& Elsevier]