Construction of rGO‐Encapsulated Co₃O₄‐CoFe₂O₄ Composites with a Double‐Buffer Structure for High‐Performance Lithium Storage

Abstract

electric vehicle industry puts forward higher requirements on the energy density and power density of commercial LIBs. [1,2] Current commercial LIBs commonly use graphite-based anodes, which suffer from a low theoretical capacity (372 mAh g −1 ) and relatively slow lithium-ion insertion-desertion kinetics, and thus cannot meet future market requirement for high energy density and power performance. [3,4] Therefore, it is of considerable significance to develop highperformance anode materials to replace the currently widely used graphite-based materials. Among multifarious potential anode materials, transition metal oxides (TMOs) such as Fe 2 O 3 , [5,6] Co 3 O 4 , [7,8] NiO, [9] Ni x Zn y Co 3−x−y , [10] MnO [11,12] as well as their composites, [13][14][15] which take place in conversion reaction with Li + , have many advantages in terms of high theoretical capacity, low acquisition cost, and safety. [16,17] However, there are still some problems to be solved before TMOs can be used as practical LIBs anodes, including huge volume expansion during the lithiation process, low electronic and ionic conductivity, and severe electrolyte decomposition during cycling. [18,19] As we know, poor conductivity of the material will lead to lower capacity release, vast volume expansion will cause rapid capacity decay, and continuous electrolyte decomposition will bring about an abnormal capacity variation. [20,21] It has been found that the nanoengineering and structural engineering design, such as constructing nanoporous [22,23] and hollow [24,25] structures, can shorten the diffusion length of Li + and offer buffer space for volume expansion, and thus improve the capacity release and cycling stability of TMOs anodes. Nevertheless, the highly porous design with a large specific surface area may aggravate side reaction of electrolyte and ultimately result in a significant initial irreversible capacity, [7,8] and hollow structure with low packing density can cause low volumetric energy density. To make better utilization of the inner hollow cavity, core-shell or multi-shell structures are highly desired. [26][27][28] However, construction of core-shell or multi-shell structures is usually a complex and tedious process. On the other hand, the introduction of graphene by in situ or ex situ methods has been proved to be highly effective in improving the conductivity and cyclic life of the TMOs-based Transition metal oxides (TMOs) are promising anode materials for next-generation lithium-ion batteries (LIBs). Nevertheless, their poor electronic and ionic conductivity as well as huge volume change leads to low capacity release and rapid capacity decay. Herein, a reduced graphene oxide (rGO)-encapsulated TMOs strategy is developed to address the above problems. The Co 3 O 4 -CoFe 2 O 4 @rGO composites with rGO sheets-encapsulated Co 3 O 4 -CoFe 2 O 4 microcubes are successfully constructed through a simple metal-organic frameworks precursor route, in which Co[Fe(CN) 5 NO] microcubes are in situ coated by graphene oxide sheets, followe...

In Situ Construction of Zn2Mo3O8/ZnO Hierarchical Nanosheets on Graphene as Advanced Anode Materials for Lithium-Ion Batteries

“…It can be speculated that the relatively low rGO content in Zn 2 Mo 3 O 8 /ZnO/rGO-25 is not sufficient to promote electron conduction and accelerate the structural reconstruction of the electrode, which could result in a continuous capacity fading until the 20th cycle, thereby showing the lowest reversible capacity. On the contrary, excessive rGO in Zn 2 Mo 3 O 8 /ZnO/rGO-45 reduces the proportion of electroactive oxide materials, resulting in a decline in the reversible capacity …”

“…To understand the effect of the rGO content on the lithium storage property, Zn 2 Mo 30 The EIS measurement was conducted to study the electronic conductivity of the as-synthesized materials, further revealing its effect on the lithium storage properties. The Nyquist plots (Figures 4h and S8a) of all as-synthesized Zn 2 Mo 3 O 8 /ZnO/ rGO electrodes before cycling comprise a semicircle in a highmedium-frequency zone, which corresponds to charge transfer resistance (R ct ), and an inclined line in the low-frequency zone related to Warburg impedance (Z w ) caused by Li + diffusion in the solid phase.…”

“…For instance, MoO 3 –CoMoO 4 microspheres and ZnO/ZnMnO 3 microspheres as LIB anodes manifest good structural integrity and improved electrochemical behavior due to the synergistic effects between two different oxides. Moreover, the electrochemical performance of metal oxide-based anodes can be boosted by hybridizing with conductive carbon materials (e.g., carbon nanotubes, carbon nanofibers, and graphene sheets). , Especially, the introduction of 2D graphene sheets as a conductive buffering matrix can greatly improve electronic conductivity, alleviate stress variations, and reduce interparticle agglomeration . Therefore, it is an attractive idea to construct Mo-cluster compound-based hierarchical architectures incorporating other metal oxides and simultaneously hybridizing with the conductive graphene matrix, to achieve advanced Mo-based anodes with high capacity and prolonged cycling stability.…”

Zero-strain strategy incorporating TaC with Ta2O5 to enhance its rate capacity for long-term lithium storage

“…Furthermore, the formation of irreversible Li dendrites in the graphite anode can result in safety issues at a low operating potential (∼0.1 V vs. Li/Li + ) and high current density. [9][10][11][12] Therefore, graphite anodes fail to satisfy the high requirements for next-generation LIBs. As such, an alternative anode is desired for LIBs that can meet the demands for long-term cycling, fast charging, and good safety.…”

Single‐Atom Tailored Hierarchical Transition Metal Oxide Nanocages for Efficient Lithium Storage

“…Apart from the structural stability, the sluggish ionic/electronic conductivity of conversion-type anodes significantly limits the maximum energy/power density. [8] Over the past decade, the conductive composites formation by nucleating and growing of the active materials on carbonaceous matrix was generally regarded as a useful strategy to address the electrical insulation issues of active materials. However, the mass of inactive part will inevitably reduce the energy density of the entire batteries.…”