ABSTRACT
The SnSb and TiO2 nanoparticles uniformly embedded into continuous and conductive carbon nanofibers (CNFs) are successfully fabricated through facile electrospinning combined with calcination treatments. The characterization results of the targeted composite nanofibers (Sb-SnSb/TiO2@CNFs-2) confirm that the presence of TiO2 is of significant importance to construct the elaborately designed and intact fiber structure, in which the optimal dosage of the TiO2 precursor is precisely controlled at 2 mmol. Moreover, high theoretical specific capacity of SnSb, available inhibitory effect of TiO2, and great electronic conductivity of CNFs are cooperatively integrated into the Sb-SnSb/TiO2@CNFs-2 composite nanofibers, guaranteeing the enhanced lithium storage capacity and cycling performance when being employed as the anode electrodes. Specifically, the Sb-SnSb/TiO2@CNFs-2 electrode can not only deliver initial discharge specific capacity of 1146.6 mAh/g at 100 mA/g and reversible discharge specific capacity of 580.4 mAh/g after 100 cycles, but also retain discharge specific capacity of 561.3 mAh/g after rate cycles along with recovering the current density to 100 mA/g. Importantly, the Sb-SnSb/TiO2@CNFs-2 electrode is also endowed with prominent advantages in the pseudocapacitive contribution of 66.89 % at 0.8 mV/s. Those investigations and findings of the Sb-SnSb/TiO2@CNFs-2 composite electrodes with facile fabrication process and excellent electrochemical performance can contribute to the practical application of the alloy anodes in the field of the energy storage.
ABSTRACT
Li3PO4 coating Li0.98Mg0.01Ni0.83Co0.11Mn0.06O2 (NCM83-MP) composite powders are successfully synthesized by first doping Mg2+ into LiNi0.83Co0.11Mn0.06O2 by co-calcination processes and followed by H3PO4 modifying the obtained Li0.98Mg0.01Ni0.83Co0.11Mn0.06O2 composite powders by sol-gel methods. Related physicochemical characterization results demonstrate that Mg2+ doping can significantly enlarge the lattice space along the c-axis to 14.1431â¯Å and lower the Li/Ni mixing degree to 1.58 %, and H3PO4 modifying can effectively reduce the residual lithium content and generate a homogeneous Li3PO4 covering with a thickness of about 11.7â¯nm on the surface of the composite particles. Furthermore, the battery performance tests indicate that the coin cells assembled with NCM83-MP can exhibit excellent cycling performance, in which the distinguished discharge specific capacity of 157.4 mAh g-1 at 2.0 C at 25⯰C after 200 cycles and 154.6 mAh g-1 at 2.0 C at 60⯰C after 100cycles are amazingly retained, respectively. Additionally, the electrode can present a smaller gap of redox peaks of 0.10â¯V and a lower resistance value of 193.8â¯Ω compared to the ones of 0.49â¯V and 451.8â¯Ω of NCM83-0 after cycles. Those enhanced electrochemical properties are mainly ascribed to the synergetic effect of Mg2+ doping and H3PO4 modifying, which can not only stabilize the lattice structure but also provide fast transfer channels to facilitate Li ions migrating. Therefore, the proposed strategy may excavate new ideas to the further investigation of high-performance Ni-rich cathode materials for lithium ion battery.
ABSTRACT
To optimize the electrochemical performance of Ni-rich cathode materials, the 0.005 mol of Mg2+ and 0.005 mol of Ti4+co-doping LiNi0.83Co0.11Mn0.06O2 composite powders, labeled as NCM-11, are successfully prepared by being calcinated at 750 °C for 15 h following by an appropriate post-treatment, which are confirmed by XRD, EDS and XPS. The results suggest that NCM-11 presents a well-ordered layered structure with a low Li+/Ni2+ mixing degree of 1.46% and Mg2+ and Ti4+ ions are uniformly distributed across the lattice. The cell assembled with NCM-11 can deliver an initial discharge specific capacity of 194.2 mAh g-1 and retain a discharge specific capacity of 163.0 mAh g-1 after 100cycles at 2.0C at 25 °C. Furthermore, it still maintains a discharge specific capacity of 166.7 mAh g-1 after 100cycles at 2.0C at 60 °C. More importantly, it also exhibits a higher discharge specific capacity of about 150.7 mAh g-1 even at 5.0C. Those superior electrochemical performance can be mainly ascribed to the synergistic effect of Mg2+ and Ti4+co-doping, in which Mg2+ ions can occupy the Li+ layer to act as pillar ions and Ti4+ ions can occupy the transition metal ions layer to enlarge the interplane spacing. Thus, the heterovalent cations co-doping strategy can be considered as a simple and practical method to improve the electrochemical performance of Ni-rich layered cathode materials for lithium-ion batteries.
