Chemically Bonding NiFe-LDH Nanosheets on rGO for Superior Lithium-Ion Capacitors

Abstract

Layered double hydroxides (LDHs) have attracted tremendous interest for applications in energy harvest and storage. However, the aggregation of nanosheets compromises the accessible active sites and limits their electrochemical performance, especially at high rates. The present study reports the synthesis of highly dispersed NiFe-LDH nanosheets anchored on reduced graphene oxide (NiFe-LDH/rGO) composites chemically bonded via a facile one-step hydrothermal method. Defect-riched rGO provides abundant active sites for heterogeneous nucleation of NiFe-LDH nanosheets, achieving the much efficient charge transfer between rGO and NiFe-LDH as compared to physically mixed NiFe-LDH + rGO. The crystallite size can effectively reduce to 5.5 nm smaller than 15.1 nm of NiFe-LDH without rGO, beneficial to expose more active surface for fast ion diffusion and redox reactions. NiFe-LDH/rGO as an anode material in lithium-ion batteries shows superior lithium storage capacity with 1202 mAh g −1 after 100 cycles at 100 mA g −1 and high-rate performance with 543 mAh g −1 even at 2000 mA g −1 . The corresponding lithium-ion capacitor with NiFe-LDH/rGO anode and mesoporous carbon microsphere cathode exhibits high energy density and power density simultaneously, with 133 Wh kg −1 at 25 W kg −1 and 4016 W kg −1 at 58 Wh kg −1 , showing the great potential for highperformance hybrid energy storage systems.

Recent Advances and Challenges of Two‐Dimensional Materials for High‐Energy and High‐Power Lithium‐Ion Capacitors

“…Compared with bulk battery materials, 2D nanosheets (e. g., TiO 2 , V 2 O 5 , MoS 2 ) with ultrathin thickness and high surface-to-volume ratio usually exhibit boosted pseudocapacitive behavior resulting from the more exposed active sites, decreased diffusion barrier and distance of electrolyte ion, and alleviated volumetric strain. Since the application of 2D materials for LICs is still in the early stage, other newly developed 2D materials (e. g., phosphorene, [95] graphdiyne, [96] metal thiophosphate, [97] and layered double hydroxide nanosheets [98] ) also deserve to be investigated, and new 2D materials should be incessantly exploited to achieve high-performance LICs. Also, assembling 2D nanosheets into 3D porous architectures can improve the contact/interaction with electrolyte and facilitate the surface-driven pseudocapacitive charge storage.…”

“…Introducing pseudocapacitance by heteroatom doping and surface functionalization with redox species is also acknowledged as a reliable strategy to boost the capacity of graphene cathode. Since the application of 2D materials for LICs is still in the early stage, other newly developed 2D materials (e. g., phosphorene, [95] graphdiyne, [96] metal thiophosphate, [97] and layered double hydroxide nanosheets [98] ) also deserve to be investigated, and new 2D materials should be incessantly exploited to achieve high-performance LICs.…”

Advances in preparation methods and mechanism analysis of layered double hydroxide for lithium-ion batteries and lithium-sulfur batteries

“…To improve aggregation of LDHs, low rate for diffusion, less reactive sites and volume expansion, Tian et al [100] developed the extremely dispersed NiFe LDH nanosheets which were chemically anchored on rGO as presented in Fig. 7(b).…”

Functionalized layered double hydroxides for innovative applications

“…29 This is because the conductive materials, e.g., graphene, can significantly enhance the electrical conductivity and accelerate the electron transfer, resulting in excellent charge and discharge capability. [41][42][43][44][45] Many other reasons for the enhanced or newly created functions of LDHs produced by various functionalization strategies are summarized in Section 2.…”