Xiaoli Ge

Metal–Organic Frameworks Derived Porous Core/Shell Structured ZnO/ZnCo2O4/C Hybrids as Anodes for High-Performance Lithium-Ion Battery

Metal-organic frameworks (MOFs) derived porous core/shell ZnO/ZnCo2O4/C hybrids with ZnO as a core and ZnCo2O4 as a shell are for the first time fabricated by using core/shell ZnCo-MOF precursors as reactant templates. The unique MOFs-derived core/shell structured ZnO/ZnCo2O4/C hybrids are assembled from nanoparticles of ZnO and ZnCo2O4, with homogeneous carbon layers coated on the surface of the ZnCo2O4 shell. When acting as anode materials for lithium-ion batteries (LIBs), the MOFs-derived porous ZnO/ZnCo2O4/C anodes exhibit outstanding cycling stability, high Coulombic efficiency, and remarkable rate capability. The excellent electrochemical performance of the ZnO/ZnCo2O4/C LIB anodes can be attributed to the synergistic effect of the porous structure of the MOFs-derived core/shell ZnO/ZnCo2O4/C and homogeneous carbon layer coating on the surface of the ZnCo2O4 shells. The hierarchically porous core/shell structure offers abundant active sites, enhances the electrode/electrolyte contact area, provides abundant channels for electrolyte penetration, and also alleviates the structure decomposition induced by Li(+) insertion/extraction. The carbon layers effectively improve the conductivity of the hybrids and thus enhance the electron transfer rate, efficiently prevent ZnCo2O4 from aggregation and disintegration, and partially buffer the stress induced by the volume change during cycles. This strategy may shed light on designing new MOF-based hybrid electrodes for energy storage and conversion devices.

ZnS-Sb2S3@C Core-Double Shell Polyhedron Structure Derived from Metal–Organic Framework as Anodes for High Performance Sodium Ion Batteries

Taking advantage of zeolitic imidazolate framework (ZIF-8), ZnS-Sb2S3@C core-double shell polyhedron structure is synthesized through a sulfurization reaction between Zn2+ dissociated from ZIF-8 and S2- from thioacetamide (TAA), and subsequently a metal cation exchange process between Zn2+ and Sb3+, in which carbon layer is introduced from polymeric resorcinol-formaldehyde to prevent the collapse of the polyhedron. The polyhedron composite with a ZnS inner-core and Sb2S3/C double-shell as anode for sodium ion batteries (SIBs) shows us a significantly improved electrochemical performance with stable cycle stability, high Coulombic efficiency and specific capacity. Peculiarly, introducing a carbon shell not only acts as an important protective layer to form a rigid construction and accommodate the volume changes, but also improves the electronic conductivity to optimize the stable cycle performance and the excellent rate property. The architecture composed of ZnS inner core and a complex Sb2S3/C shell not only facilitates the facile electrolyte infiltration to reduce the Na-ion diffusion length to improve the electrochemical reaction kinetics, but also prevents the structure pulverization caused by Na-ion insertion/extraction. This approach to prepare metal sulfides based on MOFs can be further extended to design other nanostructured systems for high performance energy storage devices.

Ni2P@Carbon Core–Shell Nanoparticle‐Arched 3D Interconnected Graphene Aerogel Architectures as Anodes for High‐Performance Sodium‐Ion Batteries

To alleviate large volume change and improve poor electrochemical reaction kinetics of metal phosphide anode for sodium-ion batteries, for the first time, an unique Ni2 P@carbon/graphene aerogel (GA) 3D interconnected porous architecture is synthesized through a solvothermal reaction and in situ phosphorization process, where core-shell Ni2 P@C nanoparticles are homogenously embedded in GA nanosheets. The synergistic effect between components endows Ni2 P@C/GA electrode with high structural stability and electrochemical activity, leading to excellent electrochemical performance, retaining a specific capacity of 124.5 mA h g-1 at a current density of 1 A g-1 over 2000 cycles. The robust 3D GA matrix with abundant open pores and large surface area can provide unblocked channels for electrolyte storage and Na+ transfer and make fully close contact between the electrode and electrolyte. The carbon layers and 3D GA together build a 3D conductive matrix, which not only tolerates the volume expansion as well as prevents the aggregation and pulverization of Ni2 P nanoparticles during Na+ insertion/extraction processes, but also provides a 3D conductive highway for rapid charge transfer processes. The present strategy for phosphides via in situ phosphization route and coupling phosphides with 3D GA can be extended to other novel electrodes for high-performance energy storage devices.

Heteroatomic interface engineering in MOF-derived carbon heterostructures with built-in electric-field effects for high performance Al-ion batteries

Confronted with challenges in promoting fast AlxCly− anion diffusion and intercalation for aluminum ion batteries (AIBs), it is of vital importance to rationally design gradient hetero-interfaces with an ideal built-in interfacial electric potential to enhance charge diffusion and transfer kinetics. Herein, we demonstrate an effective strategy to realize accurate tuning gradient heteroatom N and P doping in MOF-derived porous carbon in C@N-C@N,P-C graded heterostructures. Importantly, gradient N and P doping could modify the electronic structure of MOF-derived carbon as certified by DFT calculations, and lead to charge redistribution to induce graded energy levels and a built-in electric field in the C@N-C@N,P-C graded heteroatomic interface, thus boosting interfacial charge transfer and accelerating reaction kinetics. Furthermore, the large surface area and high porosity of C@N-C@N,P-C graded heterostructures could efficiently absorb electrolyte and enhance anion transport kinetics. As expected, the designed gradiently N,P-doped C@N-C@N,P-C heterostructure with a built-in interfacial electric field could facilitate electron and AlCl4− anion transfer spontaneously between N,P-C, N-C and C gradient components, exhibiting a superior capacity of 98 mA h g−1 at a high current density of 5 A g−1 after 2500 cycles. This strategy reveals new insights about the gradient energy band for designing high-performance electrochemical energy storage devices.