Peng He,Maolin Zhang,Saijing Wang,Limin Yuwen,Yuan Wang,Yangxi Yan,Dongyan Zhang,Xiaofei Sun
Co-free and Ni-rich LiNi 0.95 Mn 0.05 O 2 (NM95) cathodes are expected to be widely employed in power batteries due to their high capacity and low cost. However, the loss of Co and increase in Ni compromise cyclic stability and high-rate performance. Herein, PPy coating layer with excellent flexibility and conductivity is introduced on NM95 surface to enhance the structural stability and charge transfer properties. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry are utilized to elaborate on positive influence of PPy on electrochemical performance. PPy coating alleviates volumetric changes of cathode caused by charge/discharge process, suppressing mechanical fragmentation. Moreover, PPy provides protective layer to suppress side reactions and isolate the corrosion of electrolytes. Besides, PPy is widely recognized excellent electronic conductor that can promote electronic conduction. It is revealed that PPy-coated NM95 cathode exhibits excellent capacity retention of 90.1 % (4.3 V) and 84.4 % (4.5 V) after 100 charge/discharge cycles at 1 C. Moreover, capacity retention is 91.1 % after 100 cycles and initial capacity is as high as 153.4 mAh/g at 5 C. These results indicate that flexible and electronically conductive coating is effective strategy to enhance cyclic stability of NM95 cathodes.
Steven Hu,Xinghui Liang,Huimin Yuan,Zhenning Xu,Jun Wang,Hai Liu,Kaihua Xu,Xing Ou
The development of Co-free ultrahigh-Ni (Ni > 0.9) layered oxide cathode materials holds immense promise for addressing electric vehicle range limitations and cost efficiency, though substantial obstacles persist in structural durability, thermal stability, and safety. To concurrently enhance the structural integrity and interfacial stability of LiNi 0.95 Mn 0.05 O 2 , a dual-functional co-regulation strategy integrating Zr/Al bulk doping with Li 6 Zr 2 O 7 surface coating is implemented. Controlled Zr 4+ /Al 3+ co-incorporation expands interlayer spacing, strengthens transition metal–oxygen bonding, and stabilizes the oxygen framework, thereby improving Li + diffusion kinetics while suppressing cation disorder. Concurrently, the epitaxially Li 6 Zr 2 O 7 coating effectively passivates the surface by eliminating residual lithium species, inhibiting grain coarsening, and suppressing interfacial side reactions. These coupled bulk-surface modifications synergistically inhibit mechanical stress-induced crack propagation and deleterious phase transformations. Therefore, the optimized cathode achieves 96.9% capacity retention after 100 cycles at 1 C, while maintaining stable operation under extreme electrochemical conditions (4.5 V cutoff voltage) and thermal extremes (−10 °C/60 °C). This work demonstrates a synergistic modification paradigm for designing robust ultrahigh-Ni cathodes, thereby propelling the advancement of next-generation high-energy density lithium-ion batteries.
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