Investigation of Layer Structured NbSe₂ as an Intercalation Anode Material for Sodium-Ion Hybrid Capacitors

Subramanian, Yuvaraj,Veerasubramani, Ganesh Kumar,Park, Myung-Soo,Kim, Dong-Won The Electrochemical Society 2019 Journal of the Electrochemical Society Vol.166 No.4

<P>We synthesized a layer structured NbSe<SUB>2</SUB> material through gas-phase solid state reaction, and its electrochemical performance was examined as an intercalation anode for sodium-ion hybrid capacitor. The NbSe<SUB>2</SUB> electrode showed a reversible capacity of 142.5 mAh g<SUP>−1</SUP> at 200 mA g<SUP>−1</SUP> over 100 cycles with good capacity retention of 94.0%, and it delivered a high discharge capacity of 100.7 mAh at 1000 mA g<SUP>−1</SUP>. The surface capacitive process mainly contributed to the charge storage in the NbSe<SUB>2</SUB> electrode. Its superior electrochemical performance arose from the layered structure of NbSe<SUB>2</SUB> that offered the easy pathway for sodium ion diffusion and accommodated the volume strain during sodiation/de-sodiation processes. The sodium-ion hybrid capacitor assembled with NbSe<SUB>2</SUB> anode and activated carbon cathode exhibited a high power density of 599.6 W kg<SUP>−1</SUP> at energy density of 17.3 Wh kg<SUP>−1</SUP> with good capacity retention of 93.2% at 300 mA g<SUP>−1</SUP> after 3000 cycles. Our results demonstrate that the NbSe<SUB>2</SUB> can be a promising anode material for sodium-ion hybrid capacitor.</P>

Recent Progress on Sodium Vanadium Fluorophosphates for High Voltage Sodium-Ion Battery Application

Yuvaraj, Subramanian,Oh, Woong,Yoon, Won-Sub The Korean Electrochemical Society 2019 Journal of electrochemical science and technology Vol.10 No.1

Na-ion batteries are being considered as promising cost-effective energy storage devices for the future compared to Li-ion batteries owing to the crustal abundance of Na-ion. However, the large radius of the Na ion result in sluggish electrode kinetics that leads to poor electrochemical performance, which prohibits the use of these batteries in real time application. Therefore, identification and optimization of the anode, cathode, and electrolyte are essential for achieving high-performance Na-ion batteries. In this context, the current review discusses the suitable high-voltage cathode materials for Na-ion batteries. According to a recent research survey, sodium vanadium fluorophosphate (NVPF) compounds have been emphasized for use as a high-voltage Na-ion cathode material. Among the fluorophosphate groups, $Na_3V_2(PO_4)_2F_3$ exhibited the high theoretical capacity ($128mAh\;g^{-1}$) and working voltage (~3.9 V vs. $Na/Na^+$) compared to the other fluorophosphates and $Na_3V_2(PO_4)_3$. Here, we have also highlighted the classification of Fluorophosphates, NVPF composite with carbonaceous materials, the appropriate synthesis methods and how these methods can enhance the electrochemical performance. Finally, the recent developments in NVPF for the application in energy storage devices and its outlook are summarized.

Synthesis and electrochemical performance of carbon-coated Fe₂GeO₄ as an anode material for sodium-ion batteries

Subramanian, Yuvaraj,Park, Myung-Soo,Veerasubramani, Ganesh Kumar,Lee, Yun-Sung,Kim, Dong-Won Elsevier 2019 Materials chemistry and physics Vol.224 No.-

<P><B>Abstract</B></P> <P>The development of anode materials with high capacity and good cycling stability is one of the state-of-the-art objectives in the field of rechargeable sodium-ion batteries. In this work, we synthesized high-capacity spinel Fe<SUB>2</SUB>GeO<SUB>4</SUB> using a facile hydrothermal method followed by calcination and investigated its electrochemical performance as an anode material for sodium-ion batteries. The Fe<SUB>2</SUB>GeO<SUB>4</SUB> material delivered a high initial discharge capacity of 448.1 mAh g<SUP>−1</SUP>, but it showed gradual capacity fading with a capacity retention of 67.4% after 50 cycles. Its high initial capacity originated from the high electrochemical activity of Fe caused by its multiple oxidation reactions. To enhance the cycling stability of the Fe<SUB>2</SUB>GeO<SUB>4</SUB>, carbon was coated onto the surface of Fe<SUB>2</SUB>GeO<SUB>4</SUB> particles. The carbon-coated Fe<SUB>2</SUB>GeO<SUB>4</SUB> (Fe<SUB>2</SUB>GeO<SUB>4</SUB>@C) exhibited an initial discharge capacity of 423.0 mAh g<SUP>−1</SUP> with good capacity retention. The sodium-ion full cell was assembled with an Fe<SUB>2</SUB>GeO<SUB>4</SUB>@C anode and a NaCo<SUB>0.5</SUB>Fe<SUB>0.5</SUB>O<SUB>2</SUB> cathode, and the results showed superior cycling performance, demonstrating that the Fe<SUB>2</SUB>GeO<SUB>4</SUB>@C can be used as a promising anode material for sodium-ion batteries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> High-capacity spinel Fe<SUB>2</SUB>GeO<SUB>4</SUB> is synthesized by hydrothermal reaction and calcination. </LI> <LI> Fe<SUB>2</SUB>GeO<SUB>4</SUB> particle is coated with amorphous carbon to improve its cycling stability. </LI> <LI> The Fe<SUB>2</SUB>GeO<SUB>4</SUB>@C exhibits a high discharge capacity with good capacity retention. </LI> <LI> The Fe<SUB>2</SUB>GeO<SUB>4</SUB>@C can be used as a promising anode material for sodium-ion battery. </LI> </UL> </P>

Electrochemical Performance of M₂GeO₄ (M = Co, Fe and Ni) as Anode Materials with High Capacity for Lithium-Ion Batteries

Yuvaraj, Subramanian,Park, Myung-Soo,Kumar, Veerasubramani Ganesh,Lee, Yun Sung,Kim, Dong-Won The Korean Electrochemical Society 2017 Journal of electrochemical science and technology Vol.8 No.4

$M_2GeO_4$ (M = Co, Fe and Ni) was synthesized as an anode material for lithium-ion batteries and its electrochemical characteristics were investigated. The $Fe_2GeO_4$ electrode exhibited an initial discharge capacity of $1127.8mAh\;g^{-1}$ and better capacity retention than $Co_2GeO_4$ and $Ni_2GeO_4$. A diffusion coefficient of lithium ion in the $Fe_2GeO_4$ electrode was measured to be $12.7{\times}10^{-8}cm^2s^{-1}$, which was higher than those of the other two electrodes. The electrochemical performance of the $Fe_2GeO_4$ electrode was improved by coating carbon onto the surface of $Fe_2GeO_4$ particles. The carbon-coated $Fe_2GeO_4$ electrode delivered a high initial discharge capacity of $1144.9mAh\;g^{-1}$ with good capacity retention. The enhanced cycling performance was mainly attributed to the carbon-coated layer that accommodates the volume change of the active materials and improves the electronic conductivity. Our results demonstrate that the carbon-coated $Fe_2GeO_4$ can be a promising anode material for achieving high energy density lithium-ion batteries.

Towards achieving a high ionic conducing halide solid electrolyte through low cost metal (Zr and Fe) and F substitution and their admirable performance in all-solid-state batteries

( Subramanian Yuvaraj ),류광선 한국공업화학회 2023 한국공업화학회 연구논문 초록집 Vol.2023 No.0

Enhanced storage ability by using a porous pyrrhotite@N-doped carbon yolk-shell structure as an advanced anode material for sodium-ion batteries

Veerasubramani, Ganesh Kumar,Subramanian, Yuvaraj,Park, Myung-Soo,Nagaraju, Goli,Senthilkumar, Baskar,Lee, Yun-Sung,Kim, Dong-Won The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.41

<P>Sodium-ion batteries (SIBs) are undoubtedly the most promising alternatives to lithium-ion batteries considering the natural abundance, distribution and cost of sodium resources. Still, SIBs face challenges in the development of suitable anode materials due to the large volume change during sodiation/de-sodiation, which results in inferior cycling stability. Herein, we synthesized a yolk-shell structured pyrrhotite (Fe1−xS)@N-doped carbon (FS@NC) through a solution-based method and investigated its electrochemical properties for use in SIBs as an anode material. The optimized yolk-shell structured FS@NC with distinctive voids and a core exhibited a high reversible capacity of 594 mA h g<SUP>−1</SUP> over 100 cycles at 100 mA g<SUP>−1</SUP>, excellent rate capability and superior cycling performance compared to core-shell and pristine Fe1−xS materials. During the charge and discharge cycles, the synergistic effect of the porous core (Fe1−xS) with empty voids and a defective carbon shell configuration provided a large electrode/electrolyte contact area and shortened the diffusion path for electrons and sodium ions. It also mitigated the structural degradation by accommodating the volume change during continuous cycles, which was confirmed by <I>ex situ</I> SEM and TEM analyses. To demonstrate a practical application, we assembled a sodium-ion full cell with an O3-type NaCo0.5Fe0.5O2 cathode and a yolk-shell structured FS@NC anode, and the results showed superior energy storage performance.</P>

Enhanced sodium-ion storage capability of P2/O3 biphase by Li-ion substitution into P2-type Na_0.5Fe_0.5Mn_0.5O₂ layered cathode

Veerasubramani, Ganesh Kumar,Subramanian, Yuvaraj,Park, Myung-Soo,Senthilkumar, Baskar,Eftekhari, Ali,Kim, Sang Jae,Kim, Dong-Won Elsevier 2019 ELECTROCHIMICA ACTA Vol.296 No.-

<P><B>Abstract</B></P> <P>Integration of P2 and O3 phases in Na<SUB>0.5</SUB>Fe<SUB>0.5</SUB>Mn<SUB>0.5</SUB>O<SUB>2</SUB> cathode via Li-ion substitution is proposed to enhance its electrochemical performance for sodium-ion battery applications. The formation of P2 and the combination of P2/O3 intergrowth were confirmed by X-ray diffraction refinement, high resolution transmission electron microscopy and X-ray photoelectron microscopy analyses. Various content of lithium was used to find optimum P2+O3 combinations. The optimized Li-ion substituted Na<SUB>0.5</SUB>(Li<SUB>0.10</SUB>Fe<SUB>0.45</SUB>Mn<SUB>0.45</SUB>)O<SUB>2</SUB> showed a high initial discharge capacity of 146.2 mAh g<SUP>−1</SUP> with improved cycling stability, whereas the pristine Na<SUB>0.5</SUB>Fe<SUB>0.5</SUB>Mn<SUB>0.5</SUB>O<SUB>2</SUB> initially delivered a discharge capacity of 127.0 mAh g<SUP>−1</SUP>. In addition, the combination of P2+O3 increased its average voltage, which is important for achieving high energy density sodium-ion batteries. Overall, the prepared Na<SUB>0.5</SUB>(Li<SUB>0.10</SUB>Fe<SUB>0.45</SUB>Mn<SUB>0.45</SUB>)O<SUB>2</SUB> electrode exhibited the improved cycling performance in terms of reversible capacity and rate capability compared to pristine Na<SUB>0.5</SUB>Fe<SUB>0.5</SUB>Mn<SUB>0.5</SUB>O<SUB>2</SUB> electrode material.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Facile sol-gel route is used to synthesis of layered cathode via Li-ion substitution. </LI> <LI> Combination of P2 and O3 phases is confirmed using XRD refinement results. </LI> <LI> P2+O3 Na<SUB>0.5</SUB>[Li<SUB>0.10</SUB>Fe<SUB>0.45</SUB>Mn<SUB>0.45</SUB>]O<SUB>2</SUB> biphasic cathode exhibits good cycling performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>