Cobalt-doped mesoporous carbon nanofibres as free-standing cathodes for lithium–oxygen batteries

Abstract

of Co nanoparticles enhances the degree of graphitization of the CNFs, which is beneficial to CNF conductivity. Measured BET surface areas of Co-doped CNFs are in the range of 40-300 m 2 g − 1 , depending on Co content. Results show that the Li-O 2 cell comprising the Co-doped CNF free-standing cathodes can deliver specific capacities of 3700 mA h g − 1 based on the total mass of the electrodes and good cycling performance is achieved at the curtailed capacity of 100 mA h g − 1 . The good performance of the Co-doped CNFs may be attributed to the mesoporous structure of CNFs which could facilitate the deposition of solid products during discharge and decrease the mass transport resistance. Different morphologies of the Li 2 O 2 crystals obtained during discharge with Co-doped CNF cathodes support the hypothesis that the presence of Co may induce alterations by forming easily decomposable Li 2 O 2 .Abstract Herein, we present binder-free O 2 electrodes of mesoporous carbon nanofibres and Co nanoparticles (Codoped CNF). Such electrodes are synthesized using electrospinning techniques coupled with subsequent thermal treatments. The fibre-based mats behave as free-standing electrodes due to the presence of 3D cross-linked web structures, and thus additional metal mesh or gas diffusion layer supports are not required. The absence of polymeric binders in the cathode avoids side reactions due to binder instability during cell cycling. The Co-doped CNFs are characterized by field emission scanning electron microscopy, inductively coupled plasma atomic emission spectroscopy, X-ray diffraction and Raman analysis. CNFs are decorated by homogeneously distributed Co (0) nanoparticles, with sizes in the range of 10-50 nm and Co content lower than 10 wt%. N 2 adsorption-desorption measurements show that the specific surface area of the CNFs is greatly affected by incorporation of the metal nanoparticles. The introduction

Electrospinning as a route to advanced carbon fibre materials for selected low-temperature electrochemical devices: A review

“…Co and CoO particles in the Co-CoO/N-CNR material acted as nucleation sites for Li2O2, delaying the onset of complete surface coverage during discharge. This result has been replicated in other work investigating Co doped carbon fibers as air cathode materials, and is significant as the ability to continuously form and decompose Li2O2 improves rate capability and cycle stability [222]. Li2O2 has a higher energy of adsorption onto Co and CoO than carbon, limiting the formation of Li2CO3 in the doped fibres, which serves to improve cycling performance and limit parasitic side reactions.…”

Mesoporous Carbon Materials for Electrochemical Energy Storage and Conversion

“…Crespiera et al. fabricated a mesoporous carbon nanofiber with cobalt nanoparticles as free‐standing cathodes in lithium‐oxygen batteries [192] . After a complete discharge process is finished, it can be found that the presence of Co nanoparticles affected the morphology of discharge products (Figure 9a).…”

“…a) Co nanoparticles affected the morphology of discharge products on mesoporous carbon nanofibers. Reproduced with permission [192] . Copyright 2017, Springer.…”

Strategies toward High‐Performance Cathode Materials for Lithium–Oxygen Batteries

“…N‐doped vertically aligned CNTs and graphene show improved electrocatalytic activity and stability for the ORR reactions in alkaline media. Therefore, heteroatom doping has been adopted to manipulate the local electronic structures of cathode catalysts, such as graphene, carbon nanotubes, mesoporous carbon, perovskites, and metal oxides for Li–O 2 batteries.…”