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Extrinsic Pseudocapacitive Features of Molecular-Level Controlled 2D Oxidized Black Phosphorus
( Puritut Nakhanivej ),박재민,박호석 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1
Bulk and two-dimensional black phosphorus (BPs) are considered as the candidates for energy storage materials, but their performance are suffered by the low rate and cycling capabilities due to intrinsic (de-)alloying mechanism. In this work, we demonstrate the reversible extrinsic pseudocapacitive features on 2D oxidized BP (oBP) that are strongly hybridized with graphene. oBP-based electrodes show capacitance of 478 F g<sup>-1</sup> with rate capability of 72% and retention of 91% over 50,000 cycles. The surface redox reaction at oxidized P sites was investigated by In-situ spectroelectrochemical and theoretical calculations.
Nakhanivej, Puritut,Park, Sul Ki,Shin, Kang Ho,Yun, Sol,Park, Ho Seok Elsevier 2019 Journal of Power Sources Vol.436 No.-
<P><B>Abstract</B></P> <P>Vanadium pentoxide is considered as a candidate of cathode material for lithium-ion batteries owing to its high specific capacity, large potential window, and short diffusion pathway. However, vanadium pentoxide has its own limitations such as insufficient electronic conductivity, sluggish ion diffusion, and volume expansion. In order to resolve these problems, we demonstrate spray frozen assembly into hierarchically structured open-porous vanadium pentoxide/reduced graphene oxide composite microballs for high performance lithium-ion battery cathodes. The uniform distribution of vanadium pentoxide particles immobilized onto the open-porous surface of reduced graphene oxide microballs is associated with the short ion diffusion pathway, the percolated electronic conduction, and the buffering space. Accordingly, vanadium pentoxide/reduced graphene oxide composite microballs achieve the initial discharge capacity of 273 mAh g<SUP>−1</SUP> at 100 mA g<SUP>−1</SUP> which is higher than those of reduced graphene oxide (78 mAh g<SUP>−1</SUP>) and vanadium pentoxide (214 mAh g<SUP>−1</SUP>). When the current density increases from 100 to 1000 mA g<SUP>−1</SUP>, the capacity retention of vanadium pentoxide/reduced graphene oxide composite microballs is 51.3%, much greater than 36.4% of vanadium pentoxide particles. The capacity retention of 80.4% with the Coulombic efficiency of 97.1% over 200 cycles is twice greater than that of V<SUB>2</SUB>O<SUB>5</SUB> particles, indicating improved cyclic stability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> V<SUB>2</SUB>O<SUB>5</SUB>/rGO composite microballs are synthesized by spray frozen assembly. </LI> <LI> V<SUB>2</SUB>O<SUB>5</SUB> particles are uniformly distributed onto the graphene microballs. </LI> <LI> Open porous structure provides fast Li ion diffusion pathway. </LI> <LI> Rate and cyclic capabilities of V<SUB>2</SUB>O<SUB>5</SUB> are improved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
( Puritut Nakhanivej ),박호석 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0
Vanadium Oxide (V2O5)/reduced graphene oxide (rGO) composite was synthesized by spray freeze-drying method combined with heat treat-ment process. The aim of this work is to increase the electrochemical performance in term of capacity, rate capability and cyclic stability. We have investigated the physical properties and morphologies by using characterizations. The results indicated that V2O5 nanoparticles were maintained their crystal structure and well-trapped by rGO. For the lithium ion battery (LIB) application, V2O5/rGO composite exhibited superior electrochemical performance compared to pristine V2O5 and rGO due to high electrical conductivity, large surface area of hierar-chical structure, fast ion diffusion and structural stability provided by conductive rGO. The initial discharge capacity up to 375 mAh g<sup>-1</sup> could be obtained as well as good rate capability. Our work may open up new route and material design for the improvement of LIB cathodes.
Revealing molecular-level surface redox sites of controllably oxidized black phosphorus nanosheets
Nakhanivej, Puritut,Yu, Xu,Park, Sul Ki,Kim, Soo,Hong, Jin-Yong,Kim, Hae Jin,Lee, Wonki,Hwang, Jun Yeon,Yang, Ji Eun,Wolverton, Chris,Kong, Jing,Chhowalla, Manish,Park, Ho Seok Springer Science and Business Media LLC 2019 Nature materials Vol.18 No.2
Multivalent Cation Storage for Hybrid Supercapacitor
( Puritut Nakhanivej ),박호석 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
The requirements for high energy density and power density have become important for smart grid and electronic vehicle applications. The storage using multi-electron or multivalent cations has opened up the new avenue for ground breaking of the barriers that exist in traditional energy storage research and applications. The discovering of active materials for multivalent cations storage is necessary and urgent for further in-depth understanding the mechanism and developing the system. Here, we demonstrate the hybrid supercapacitor using the multivalent cation of magnesium as active ions. Specifically, we apply Mxene as negative electrode and partially oxidized black phosphorus hybrids as positive electrode which display reasonable performance. It is noted that the challenges with much effort still remain in the development of this chemistry approach to meet the energy parameter requirements.
( Puritut Nakhanivej ),박호석 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
Black Phosphorus (BP) has become a candidate for energy applications since it provides high theoretical capacities of 2,600 mAh g<sup>-1</sup>. Nonetheless, their rate and cycling capabilities are suffered from intrinsic (de-)alloying mechanism. Herein, we reveal unique molecular-level surface redox sites on oxygen functionalized BP nanosheets, hybridizing with graphene through strong interlayer covalent bonding. Our in-situ spectroelectrochemical and theoretical analyses suggest that the active oxidized P redox sites display truly reversible pseudocapacitive behavior, providing superior electrochemical performance. Our chemical approach proposes the effective way to develop the supercapacitor electrodes with novel mechanism, high capacitance, excellent rate capability, and prolonged cycle life.
( Puritut Nakhanivej ),박슬기,신강호,박호석 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1
Hierarchically structured composite of Vanadium Oxide (V2O5)/reduced graphene oxide (rGO) was synthesis by facile mixing combined with ice-templating method and used as cathode material for lithium-ion battery. The physical properties and morphologies were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The results suggested that V2O5 nanoparticles were maintained their crystal structure and chemical composition after composed with rGO. Hierarchically structured V2O5/rGO composite displays greater electrochemical performance compared to pristine V2O5 due to superior electrical conductivity, high surface area, fast ion diffusion and structural stability provided by conductive rGO matrix. The initial discharge capacity up to 375 mAh g<sup>-1</sup> could be obtained as well as good rate capability. Our work may open up new method and material design for the improvement of lithium-ion battery cathodes.