Reducing Intrinsic Drawbacks of Ni-rich Layered Oxide Cathode Materials with a Dry Coating Concept of Quasi-solid Nanomaterials towards High-performance Cylindrical Li-ion Batteries

Abstract

Although Ni-rich layered oxide cathode materials of Li-ion batteries can provide high energy density, their performance degradation over long cycling and safety hazard due to their intrinsic property issues limit their practical long-term applications. Herein, we introduce a concept based on Ni-rich NMC811 core@quasi-solid shell structure. The Li-rich quasi-solid shell material was prepared by infusing 2 M LiTFSI in [EMIM][TFSI] into a whole pore of Al2O3 nanoparticles delivering a high ionic conductivity (2.8 × 10−4 S cm−1) at room temperature (25 °C). Then the shell material with a thickness of ca. 200 nm below a “Play Dough-like” state was coated on NMC811 using a green and scalable mechanofusion process. The 18650 cylindrical Li-ion battery cells using the core-shell cathode and the graphite anode at a pilot-plant manufacturing scale exhibit considerable high-rate capability compared to the pristine NMC811, especially at a high C-rate. The post-mortem analysis demonstrated that with the thick semi-solid shell there is no transition metal dissolution. Also, the battery cells retained a high discharge capacity after long-term cycling without any safety hazards. We believe that the semi-solid encapsulation in this work may be useful for next-generation high-energy Ni-rich Li-ion batteries.