A cost-effective approach is disclosed in this invention to converting recycled LiNixMnyCozO2 (referred to as NMC hereafter, x+y+z=1), regardless of the stoichiometry of Ni,Mn,Co and morphologies of different NMC used in various batteries, into high performance single crystal Ni-rich NMC such as LiNi0.8Mn0.1Co0.1O2 with simple heating process with Li2O (background IP: Cost effective synthesis of oxide materials for lithium ion batteries, US20220112094A1). The reported approach significantly simplifies the synthesis process of NMC by using recycled cathode materials which not only reduces manufacturing cost but supports a stable domestic supply chain. In addition, the different NMC cathodes recycled from various batteries are directly converted into single crystal Ni-rich NMC which is critical for large-scale deployment of Ni-rich NMC for current and future Li-based battery technologies. This invention is well aligned with the recent DOE FOA (DE-FOA-0002680) which focuses on battery recycling. Expedient filing of this invention will enable PNNL engagement with industry.