Spinel LiNi0.5Mn1.5O4 cathode material is a promising candidate for next-generation rechargeable lithium-ion batteries. In this work, BiFeO3-coated LiNi0.5Mn1.5O4 materials were prepared via a wet chemical method and the structure, morphology, and electrochemical performance of the materials were studied. The coating of BiFeO3 has no significant impact on the crystal structure of LiNi0.5Mn1.5O4. All BiFeO3-coated LiNi0.5Mn1.5O4 materials exhibit cubic spinel structure with space group of Fd3m. Thin BiFeO3 layers were successfully coated on the surface of LiNi0.5Mn1.5O4 particles. The coating of 1.0 wt% BiFeO3 on the surface of LiNi0.5Mn1.5O4 exhibits a considerable enhancement in specific capacity, cyclic stability, and rate performance. The initial discharge capacity of 118.5 mAh g?1 is obtained for 1.0 wt% BiFeO3-coated LiNi0.5Mn1.5O4 with very high capacity retention of 89.11% at 0.1 C after 100 cycles. Meanwhile, 1.0 wt% BiFeO3-coated LiNi0.5Mn1.5O4 electrode shows excellent rate performance with discharge capacities of 117.5, 110.2, 85.8, and 74.8 mAh g?1 at 1, 2, 5, and 10 C, respectively, which is higher than that of LiNi0.5Mn1.5O4 (97.3, 90, 77.5, and 60.9 mAh g?1, respectively). The surface coating of BiFeO3 effectively decreases charge transfer resistance and inhibits side reactions between active materials and electrolyte and thus induces the improved electrochemical performance of LiNi0.5Mn1.5O4 materials. 相似文献
The effect of different membranes and aluminum current collectors on the initial coulombic efficiency of LiNi0.5Mn1.5O4/Li was investigated, and the cycling performance at different rates and temperatures and the storage performance at 60 °C for a week are discussed for LiNi0.5Mn1.5O4/Li. The results show that the lower initial coulombic efficiency is associated with the lower decomposition voltage of the commercial membrane and electrolyte, and the instability of aluminum current collector under the higher voltage. In addition, both versions of LiNi0.5Mn1.5O4 can deliver about 115 mA?h g?1 of initial discharge capacity at 1 C at 25 °C and 60 °C; however, it retains only 61.57 % of its initial capacity after the 130th cycles at 60 °C, which is much lower than the 94.46 % rate observed for LiNi0.5Mn1.5O4 at 25 °C, and the cycling performance of the material at 1 C is better than that at 0.5 C. Meanwhile, the initial discharge capacity at 0.1 C after storing at 60 °C is 119.3 mA?h g?1, which is only a little lower than 121.5 mA?h g?1 recorded before storing; moreover, the spinel structure and surface state of LiNi0.5Mn1.5O4 after storing at 60 °C has not been changed basically. These results indicate that the electrochemical stability of electrolyte is also related to the temperature. The serious capacity fading of LiNi0.5Mn1.5O4 at 60 °C is attributed to the severe oxidation decomposition and the thermal decomposition in the range of cut-off voltage of the materials, and then the decomposition products interact with active materials to form a solid interface phase, leading to the larger electrode polarization and irreversible capacity loss. Meanwhile, the worse cycling performance at 0.5 C than that at 1 C is attributed to the longer interaction time between the electrolyte and the active materials. However, the storage performance of LiNi0.5Mn1.5O4 corresponds to the thermal stability of electrolyte to a certain extent. 相似文献
In this paper, the LiNi0.5Mn1.5O4 cathode materials of lithium-ion batteries are synthesized by a co-precipitation spray-drying and calcining process. The use of a spray-drying process to form particles, followed by a calcination treatment at the optimized temperature of 750 °C to produce spherical LiNi0.5Mn1.5O4 particles with a cubic crystal structure, a specific surface area of 60.1 m2 g?1, a tap density of 1.15 g mL?1, and a specific capacity of 132.9 mAh g?1 at 0.1 C. The carbon nanofragment (CNF) additives, introduced into the spheres during the co-precipitation spray-drying period, greatly enhance the rate performance and cycling stability of LiNi0.5Mn1.5O4. The sample with 1.0 wt.% CNF calcined at 750 °C exhibits a maximum capacity of 131.7 mAh g?1 at 0.5 C and a capacity retention of 98.9% after 100 cycles. In addition, compared to the LiNi0.5Mn1.5O4 material without CNF, the LiNi0.5Mn1.5O4 with CNF demonstrates a high-rate capacity retention that increases from 69.1% to 95.2% after 100 cycles at 10 C, indicating an excellent rate capability. The usage of CNF and the synthetic method provide a promising choice for the synthesis of a stabilized LiNi0.5Mn1.5O4 cathode material.
Graphical Abstract Micro/nanostructured LiNi0.5Mn0.5O4 cathode materials with enhanced electrochemical performances for high voltage lithium-ion batteries are synthesized by a co-precipitation spray-drying and calcining routine and using carbon nanofragments (CNFs) as additive.
