Novel dry deposition of LiNbO3 or Li2ZrO3 on LiNi0.6Co0.2Mn0.2O2 for high performance all-solid-state lithium batteries

LiNbO3 (50-100 nm) and Li2ZrO3 (30-60 nm) nanoparticles are a suitable electrode-coating agent because they can suppress direct contact with the sulfide-based solid electrolyte, decrease contact loss, and eliminate the space-charge layer. The LiNbO3 and Li2ZrO3 nanoparticles were coated on LiNi0.6Co0.2Mn0.2O2 (NCM) cathode material by a ResonantAcoustic (R) Mixer (LabRAM II) for all-solid-state lithium batteries (ASSLBs) and their improved electrochemical properties were assessed. ASSLBs using LiNbO3 and Li2ZrO3-coated NCM material showed higher capacity than did bare NCM cathode material. X-ray diffraction patterns showed no deviation on diffraction patterns and lattice parameters on cathode materials after the coating. Field-emission scanning electron microscopy and transmission electron microscopy images obtained with electron dispersive spectroscopy mapping confirmed homogeneous coating with a uniformly thick LiNbO3 or Li2ZrO3 layer of around 50-200 nm. X-ray photoelectron spectroscopy showed that the surface of NCM had two different O1s peaks and an Nb-O peak, and displayed the Ni, Co, Mn 2p, and Nb 3d peaks. Electrochemical studies on bare NCM and LiNbO3 and Li2ZrO3-coated NCM materials using electrochemical impedance spectroscopy elucidated the galvanostatic cycle performances by assembling an all-solid-state cells with c-rate performances. Notably, the 3 wt % LiNbO3-coated NCM exhibited capacity retention of 84% at a current density of 15 mA/g during 20 cycles, whereas the bare NCM exhibited a capacity retention of only 16.1%. In addition, we used X-ray photoelectron spectroscopy and TEM-electron energy-loss spectroscopy to measure the cathode composites after 20 cycles. The 3 wt% LiNbO3 and Li2ZrO3-coated NCM composite showed an improved interface and lowered side reaction.