Highly Reversible Lithium Storage of Nitrogen‐Doped Carbon@MnO Hierarchical Hollow Spheres as Advanced Anode Materials

Abstract

The practical implementation of MnO‐based anode materials is still obstructed because of their short cyclic life and unsatisfactory rate performance, attributable to low conductivity, large volume variation and self‐aggregation of MnO during intense cycles. To overcome these obstacles, we successfully fabricated nitrogen‐doped carbon@MnO hierarchical hollow spheres through a novel approach. As anode nanomaterials for Li‐ion batteries, the nanocomposite possesses a highly reversible capacity of 1302 mAh g−1 after the 200th cycle at 0.1 Ag−1 and 964 mAh g−1 after the 500th cycle at 0.5 Ag−1, respectively. The prominent electrochemical performances of the nanocomposite may result from synthetic effects of nitrogen‐doped carbon hollow structures, nanosized MnO and the gradual generation of high‐oxide‐state manganese oxide on nitrogen‐doped carbon hollow spheres during intensive cycles. The aforementioned results also demonstrate that MnO nanocrystals can be well utilized by attaching to nitrogen‐doped carbon hollow spheres, which is a valid way to achieve excellent lithium storage properties for transition metal oxides.

Interfacial Superassembly of Grape-Like MnO–Ni@C Frameworks for Superior Lithium Storage

“…The Mn 2+ state is unstable and can easily be oxidized to a higher valence state, which leads to the unstable specific capacities during charge and discharge processes. Therefore, a significant increase of specific capacity can be found from the results of the reported MnO/C composites with excellent electrochemical performance. ,,,− Notably, in our previous work, the specific capacities of MnO/C composite were one time higher than the theoretical capacity of MnO after 200 cycles . Furthermore, this phenomenon can be observed from other transition-metal oxides anodes, such as Co 3 O 4 , MoO 2 , and so forth. − If the anode materials are employed with unstable electrochemical performance, it is difficult to seek any appropriate cathode materials to match them for commercial applications.…”

“…Transition-metal oxides allow reversible intercalation/deintercalation of Li ions or react with Li ions by conversion reactions, which are believed to be the potential anode candidates to overcome the challenges for high-performance LIBs. Apart from Co 3 O 4 , SnO 2 , Mn 3 O 4 , MoO 2 , MnO-based electrodes are becoming attractive anode materials as a result of their merits including high theoretical capacity, low potential plateau, high density, weak polarization during cycling, environmental benignity, high abundance, and low cost. − However, the most mentioned problems associated with MnO-based anodes for LIBs include large volumetric change during the cycling processes and low electrical conductivity . The large volumetric change varies because of the conversion reactions during Li storage, leading to severe pulverization of the particles and the electrical contact loss, while the low electrical conductivity could result in poor rate capability due to the kinetic limitations. , Accordingly, tremendous research efforts have been carried out to obtain high-performance MnO-based anode materials.…”

“…8−11 However, the most mentioned problems associated with MnO-based anodes for LIBs include large volumetric change during the cycling processes and low electrical conductivity. 12 The large volumetric change varies because of the conversion reactions during Li storage, leading to severe pulverization of the particles and the electrical contact loss, while the low electrical conductivity could result in poor rate capability due to the kinetic limitations. 13,14 Accordingly, tremendous research efforts have been carried out to obtain high-performance MnO-based anode materials.…”

Thermodynamic Perspective: Insights into the Capacity Increase Phenomenon and Regulation of the Capacity Tendency of MnO for Lithium-Ion Battery Anodes

“…However, the capacity increase mechanism of MnO has its own unique characteristics, which has been reported in many previous literature studies. − The lithiation and delithiation behaviors indicate that the further oxidation of Mn 2+ ions to Mn 3+ or Mn 4+ is a key factor in specific capacity increase during the battery operation process. , There is one question that cannot be avoided: is it beneficial or harmful for a specific capacity increase during the discharge/charge process? Generally, to obtain high energy density, our expectation for the anode is always as high as possible capacity and low potential.…”