Effects of the Inherent Tubular Structure and Graphene Coating on the Lithium Ion Storage Performances of Electrospun NiO/Co₃O₄ Nanotubes

Abstract

As anode materials for lithium-ion batteries, transition metal oxides show usually high theoretic specific lithium ion storage capacities, but their electrical conductivity remains to be improved and their structural pulverizations during lithiation/delithiation need to be suppressed, which affect severely their lithiation/delithiation rate capability and also the cycling stability. Herein, NiO/Co 3 O 4 nanotubes encapsulated with graphene sheets are designed and assembled. It is demonstrated that as anode for lithium-ion batteries, the as-obtained NiO/Co 3 O 4 nanotubes encapsulated with graphene show excellent electrochemical performance, including large lithium ion storage capability (∼1206 mA h g −1 at 0.1 A g −1 after 100 cycles), high rate capability, and cycling stability. The electrochemical kinetics analyses reveal that the tubular structure not only facilitates lithium ion transportation, but also provides even more spaces for lithium ion storage. The external encapsulated graphene sheets can improve the electrical conductivity of NiO/Co 3 O 4 nanotubes, and afford also certain lithium ion storage capacity. Those structural and component factors synergistically account for their improved electrochemical performances.

Eutectic‐derived bimodal porous Ni@ NiO nanowire networks for high‐performance Li‐ion battery anodes

“…X‐ray photoelectron spectroscopy (XPS) measurements were performed to elucidate the chemical states of the surface constituent elements of the three samples. The Ni 2p spectrum of the samples are shown in Figure 3C, in which the peaks at 852.3 and 872.9 eV belong to Ni 3+ , whereas the peaks at 855.7 and 873.8 eV relate to Ni 2+ 61‐63 . The existence of Ni 3+ is considered as the result of the further oxidation of exposed Ni sites in the air 62,64 .…”

“…The Ni 2p spectrum of the samples are shown in Figure 3C, in which the peaks at 852.3 and 872.9 eV belong to Ni 3+ , whereas the peaks at 855.7 and 873.8 eV relate to Ni 2+ . [61][62][63] The existence of Ni 3+ is considered as the result of the further oxidation of exposed Ni sites in the air. 62,64 With the increase in solidification rate, the intensity of Ni 3+ peaks increase.…”

“…[61][62][63] The existence of Ni 3+ is considered as the result of the further oxidation of exposed Ni sites in the air. 62,64 With the increase in solidification rate, the intensity of Ni 3+ peaks increase. This indicates that more active sites are exposed in the air, which is related to the increase of SSA of the material.…”

Recent Advances in Electrospun Metal Chalcogenide Anodes for Lithium-Ion and Sodium-Ion Batteries

“…The mixed oxides can be easily prepared by a mixture at least two metal oxides with a random ratio, which are decided by the structure design demand of energy storage. TiO 2 , SnO 2 , and NiO are the primary ingredients of the mixed oxides, such as TiO 2 /NiO, SnO 2 /Fe 2 O 3 , and NiO/Co 3 O 4 . The mixed oxides can enhance the conductivity, shorten the ion transport path, and release the volume variation.…”

Tailoring Porous Transition Metal Oxide for High-Performance Lithium Storage

“…Numerous efforts have been investigated to improve the cyclic stability of TMOs; reducing the particle size to nanoscale has been revealed to be a feasible approach to tackle the existed problems in TMO anodes. − The active particles at nanoscale can not only buffer the stress accumulation from volume change but also shorten the diffusion pathway of lithium ions. − Besides, the large exposed area of TMO nanoparticles provides abundant active sites for surface/near-surface reactions compared with bulk state. − However, highly unstable thermodynamics of nanoparticles, such as huge surface energy, ineluctably induce the irreversible agglomeration of TMO nanoparticles and further result in an obvious loss of accessible active sites and subsequent degeneration in capacity retention. − Confining TMO nanoparticles into a 3D interconnected framework offers a feasible approach to overcome the mentioned challenge, where the fabricated 3D architecture can efficiently inhibit the intrinsic agglomeration of nanocrystallization to maintain the exposed active centers well. − Nevertheless, severe volume variation inevitably damages the formed SEI film under repeat dissolution and formation, which leads to a low Coulombic efficiency and poor cycle life. − The cracking of nanoparticles can be conceptually suppressed by the presence of interior space, which served as buffer for volume change and stabilization of SEI film. , However, constructing this type of gradient structure is rarely reported possibly due to the complex and rigorous reaction conditions.…”