A further electrochemical investigation on solutions to high energetical power sources: isomerous compound 0.75Li1.2Ni0.2Mn0.6O2·0.25LiNi0.5Mn1.5O4Electronic supplementary information (ESI) available. See DOI: 10.1039/c5ra03289j

• Main Authors: Zheng, Zhuo, Wu, Zhen-Guo, Zhong, Yan-Jun, Shen, Chong-Heng, Hua, Wei-Bo, Xu, Bin-Bin, Yu, Chong, Zhong, Ben-He, Guo, Xiao-Dong
• Format: Article
• Language: English
• ISSN: 2046-2069
• DOI: 10.1039/c5ra03289j

An isomerous layered/spinel 0.75Li 1.2 Ni 0.2 Mn 0.6 O 2 ·0.25LiNi 0.5 Mn 1.5 O 4 cathode material with outstanding electrochemical properties has been synthesized by a reasonable design of introducing high-power spinel LiNi 0.5 Mn 1.5 O 4 material to fill up the surface gaps of pristine lithium-rich layered Li 1.2 Ni 0.2 Mn 0.6 O 2 material with a molar ratio of 25 : 75. Morphological characterization reveals that the octahedral spinel LiNi 0.5 Mn 1.5 O 4 particles are successfully coated into the surface gaps of the Li 1.2 Ni 0.2 Mn 0.6 O 2 secondary particle, forming a special alternant structure with spherical and octahedral particles on the surface. Interestingly, some hollow sections are also observed in 0.75Li 1.2 Ni 0.2 Mn 0.6 O 2 ·0.25LiNi 0.5 Mn 1.5 O 4 material, confirmed from the TEM images. The structural characterization demonstrates that this isomerous compound is more well-defined α-NaFeO 2 configured, more enlarged in Li layer spacing and lower in cation disordered degree. The exquisite morphology and ideal structure endow this nanocrystal-assembled composite significantly enhanced electrochemical performance with high capacity, good rate capability and excellent cycling stability, compared with the pristine Li 1.2 Ni 0.2 Mn 0.6 O 2 . It delivers a discharge capacity of 135 mA h g −1 even at an ultrahigh current density of 2000 mA g −1 (10 C). Moreover, the superior cycling stability is also observed with high discharge capacities of 254 mA h g −1 and 222 mA h g −1 at 0.5 C and 1 C after 100 cycles with capacity retention of 98% and 94%, respectively. Moreover, the fast-charging test results are indicative of the fact that this layered/spinel cathode could be used in practical application. Its discharge capacity is 176 mA h g −1 at 1 C after 50 cycles with the charge rate of 10 C. Furthermore, the composite can endure high current charging and discharging even at a high cut-off potential (5.0 V), whereas the pristine Li 1.2 Ni 0.2 Mn 0.6 O 2 material cannot. Therefore, we absolutely believe that this isomerous layered/spinel 0.75Li 1.2 Ni 0.2 Mn 0.6 O 2 ·0.25LiNi 0.5 Mn 1.5 O 4 cathode is a promising candidate for the commercial development of advanced LIBs. A 0.75Li 1.2 Ni 0.2 Mn 0.6 O 2 ·0.25LiNi 0.5 Mn 1.5 O 4 cathode material with outstanding electrochemical properties has been synthesized by introducing spinel LiNi 0.5 Mn 1.5 O 4 material to fill the surface gaps in pristine lithium-rich layered Li 1.2 Ni 0.2 Mn 0.6 O 2 in a molar rat