Ever‐Increasing Pseudocapacitance in RGO–MnO–RGO Sandwich Nanostructures for Ultrahigh‐Rate Lithium Storage

Abstract

Lithium ion batteries have attained great success in commercialization owing to their high energy density. However, the relatively delaying discharge/ charge severely hinders their high power applications due to intrinsically diffusion-controlled lithium storage of the electrode. This study demonstrates an ever-increasing surface redox capacitive lithium storage originating from an unique microstructure evolution during cycling in a novel RGO-MnO-RGO sandwich nanostructure. Such surface pseudocapacitance is dynamically in equilibrium with diffusion-controlled lithium storage, thereby achieving an unprecedented rate capability (331.9 mAh g −1 at 40 A g −1 , 379 mAh g −1 after 4000 cycles at 15 A g −1 ) with outstanding cycle stability. The dynamic combination of surface and diffusion lithium storage of electrodes might open up possibilities for designing high-power lithium ion batteries. and high-rate lithium storage capability by tuning the surface pseudocapacitance.Herein, we successfully demonstrate ultrahigh-rate lithium storage in a novel RGO (reduced graphene oxide)-MnO-RGO sandwich nanostructure, in which dynamic equilibrium between surface pseudocapacitance and diffusion-controlled lithium storage is achieved after a novel cycle-induced microstructure evolution ( Figure 1 ). The top and bottom RGO layers provide fast pathway for charge transfer, constrain the aggregation of active materials, and suppress the stress across the whole electrode during lithiation/delithiation. More interestingly, the pulverized manganese oxide nanocrystals generated over cycling are confi ned and trapped on these RGO layers, forming hierarchical RGO-supported manganese oxide nanoclusters. Meanwhile, further oxidation of MnO to Mn 3 O 4 along with cycling, which contributes signifi cantly to the pseudocapacitance, is clearly demonstrated. All the cycle-induced features result in the steadily increased lithium pseudocapacitance with high-rate capability in the RGO-MnO-RGO sandwich nanostructure.

Pseudocapacitive Lithium Storage in Three‐Dimensional Cobalt‐Doped MnO/Nitrogen‐Doped Reduced Graphene Oxide Aerogels as High‐Rate Anode Material

“…According to the discharge and charge capacities, the initial Coulombic efficiency of 3D Co−MnO/NG‐G is about 72.1 %. The irreversible loss of about 27.9 % in the initial cycle is mainly attributed to the formation of SEI film during the initial cycle ,. However, from the second cycle onwards, the Coulombic efficiency enhances gradually and is close to 100 % after six cycles, exhibiting excellent reversibility of lithium conversion reaction.…”

“…The capacity retention from the second cycle to the last cycle is as high as 116.5 % with Coulombic efficiency close to 100 %. The escalation in capacity could be attributed to the synergistic lithium storage effect, which involves the reversible formation/dissolution of SEI film deriving from electrolyte degradation,, and the surface insertion of lithium ions leading to the pseudocapacitive lithium storage . The 3D MnO/NG‐G exhibits the capacity of only 720.8 mAh g −1 at the second cycle and 746.6 mAh g −1 after 100 cycles, for comparison, corresponding to a capacity retention of 103.6 %.…”

“…The outstanding rate capability and excellent long‐term cycle stability of 3D Co−MnO/NG‐G especially in high rate are attributed to the novel 3D Co−MnO/NG‐G. The 3D porous structure supplies 3D channels for electron/ion transport, contributing to much more surface pseudocapacitive lithium storage . Doping MnO with Co could enhance the migration rate of carrier and offer abundant cationic conversion reactions for lithium storage, leading to improved reaction kinetics and reversible capacity ,.…”

Bioinspired Architectures and Heteroatom Doping To Construct Metal‐Oxide‐Based Anode for High‐Performance Lithium‐Ion Batteries

“…The capacity of MnO/N−C is much higher than the theoretical value of 756 mAh g −1 for MnO, which should benefit from the lithium‐storage capability within the spaces of the nanostructures. The fine (dis‐)charge curves of MnO/N−C are presented in Figure b, in which the increased capacity may result from the activation of MnO during the cycling for the repeated (de‐)lithiiation . One interesting phenomenon we have found is that the bare MnO has no increment trend in capacity compared to that of MnO/N−C.…”

Magnetic tubular carbon nanofibers as anode electrodes for high‐performance lithium‐ion batteries

“…[57][58][59] When the b value is close to 1, it represents the surface control process. When the b value approaches 0.5, it means the diffusion control process.…”