Ni3(PO4)2-coated Li[Ni0.8Co0.15Al0.05]O2 lithium battery electrode with improved cycling performance at 55 °C

To improve the cycling performance of LiNi0.8Co0.15Al0.05O2 at 55 °C, a thin Ni3(PO4) layer was homogeneously coated onto the cathode particle via simple ball milling. The morphology of the Ni3(PO4)2-coated LiNi0.8Co0.15Al0.05O2 particle was characterized using SEM and TEM analysis, and the coating thickness was found to be approximately 10–20 nm. The Ni3(PO4)2-coated LiNi0.8Co0.15Al0.05O2 cell showed improved lithium intercalation stability and rate capability especially at high C rates. This improved cycling performance was ascribed to the presence of Ni3(PO4)2 on the LiNi0.8Co0.15Al0.05O2 particle, which protected the cathode from chemical attack by HF and thus suppressed an increase in charge transfer resistance. Transmission electron microscopy of extensively cycled particles confirmed that the particle surface of the Ni3(PO4)2-coated LiNi0.8Co0.15Al0.05O2 remained almost undamaged, whereas pristine particles were severely serrated. The stabilization of the host structure by Ni3(PO4)2 coating was also verified using X-ray diffraction.