Yuzhen Duan,Junming Guo,Mingwu Xiang,Jinyu Zhu,Changwei Su,Hongli Bai,Xiaofang Liu,Wei Bai,Rui Wang
A series of single crystalline spinel LiNi x Mn 2- x O 4 (0 ≤ x ≤ 0.10) cathode materials were synthesized in virtue of a facile solution-combustion approach. The morphology and the structure of all as-prepared samples were synthetically investigated with the X-ray diffraction (XRD), the scanning electron microscopy (SEM), the high-resolution transmission electron microscopy (HRTEM), and the X-ray photoelectron spectrometer (XPS). According to these investigation results, Ni-doping content has a significant impact on the control of morphology and crystalline structure, hence the as-prepared LiNi x Mn 2- x O 4 samples exhibit polyhedral morphology with high crystallinity and average size of 100–200 nm. This unique polyhedral crystal structure has numerous surfaces fitting the (111) crystalline orientation which exhibit the smallest Mn dissolution in electrolytes, whilst stabilizing the spinel framework. Owing to the merits of both single crystalline polyhedral structure and appropriate Ni-doping, the as-obtained LiNi x Mn 2- x O 4 cathodes reveal enhanced rate capability coupled with long cycling performance. In especial, the LiNi 0.08 Mn 1.92 O 4 presents a initial discharge capacity of 101.3 mAh/g and ultralong cycle stability up to 2000 cycles at 1C, whilst showing enhanced cycle performance when temperature increases to 55 °C. Excellent capacity retention of 72% and 63% is also obtained after 1000 cycles even at high current rate of 5C and 10C. This study may contribute to an effective candidate approach for the obvious improvement on lithium ion batteries in term of electrochemical activity.
Interfacial modification is one of the most important technologies to improve the overall electrochemical properties of Ni-rich cathodes. Herein, a novel strategy of in situ planting of an electrolyte film-forming additive on a single crystal NCM811 surface is proposed by consuming the residual lithium to develop a functional Al(Li)BOB nano-layer. Different from traditional physical coating, this approach cleverly consumed the undesirable residual lithium on the NCM811 surface. The in situ grown 30–50 nm Al(Li)BOB layer on the single crystal NCM811 cathode surface contributes to its much enhanced electrochemical performances. At a high operating voltage (charge voltage limit of 4.5 V vs. Li/Li+), the capacity retention is greatly increased from 57.0% to 83.5% after 295 cycles. Meanwhile, the incorporation of aluminum is effective in improving the thermal stability of the Ni-rich cathode. The novel interfacial strategy by in situ implanting of an electrolyte additive is of important significance for solving the critical interfacial issue for Ni-rich cathode materials.
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