- Nano Express
- Open Access
Carbon- and Binder-Free NiCo2O4 Nanoneedle Array Electrode for Sodium-Ion Batteries: Electrochemical Performance and Insight into Sodium Storage Reaction
© Lee et al. 2016
- Received: 7 December 2015
- Accepted: 9 January 2016
- Published: 1 February 2016
Sodium (Na)-ion batteries (NIBs) have attracted significant interest as an alternative chemistry to lithium (Li)-ion batteries for large-scale stationary energy storage systems. Discovering high-performance anode materials is a great challenge for the commercial success of NIB technology. Transition metal oxides with tailored nanoarchitectures have been considered as promising anodes for NIBs due to their high capacity. Here, we demonstrate the fabrication of a nanostructured oxide-only electrode, i.e., carbon- and binder-free NiCo2O4 nanoneedle array (NCO-NNA), and its feasibility as an anode for NIBs. Furthermore, we provide an in-depth experimental study of the Na storage reaction (sodiation and desodiation) in NCO-NNA. The NCO-NNA electrode is fabricated on a conducting substrate by a hydrothermal method with subsequent heat treatment. When tested in an electrochemical Na half-cell, the NCO-NNA electrode exhibits excellent Na storage capability: a charge capacity as high as 400 mAh g−1 is achieved at a current density of 50 mA g−1. It also shows a greatly improved cycle life (~215 mAh g−1 after 50 cycles) in comparison to a conventional powder-type electrode (~30 mAh g−1). However, the Na storage performance is still inferior to that of Li, which is mainly due to sluggish kinetics of sodiation–desodiation accompanied by severe volume change.
- Sodium-ion battery
- Nickel-cobalt oxide
- Nanoneedle array
- Sodium storage
- Conversion reaction
Recently, sodium (Na)-ion batteries (NIBs) have received considerable attention as a promising alternative to current lithium (Li)-ion batteries (LIBs), mainly due to the abundance of the element Na and its cost-effectiveness [1–4]. In particular, replacing LIBs with NIBs is a potential strategy to fulfill the cost requirements for large-scale stationary energy storage systems. In comparison to Li, however, Na has a larger ionic radius and a higher redox potential, which make electrochemical performance of NIBs inferior to that of LIBs. One of the main challenges for the successful development of NIB technology is thus to find suitable electrode materials that offer excellent Na storage capability [5–9]. Although much research focus has been on designing and synthesizing cathode (positive electrode) materials with high specific capacities, high operating voltages, and long cycle life, little attention has been given to anode (negative electrode) materials for NIBs.
To date, transition metal oxides have been extensively studied as anode materials for use in LIBs due to their high specific capacities delivered via the conversion reaction of oxides with Li [10–22]. The complete reduction of transition metal ions during the lithiation process leads to much higher capacities compared with conventional intercalation materials (e.g., graphite). However, the large volume changes of transition metal oxides during the conversion reaction combined with their low electronic conductivity severely hinder their application in practical LIB systems [5, 10, 14, 21]. A nanostructured electrode designed by tailoring the morphologies and surface structures at a nanoscale has been proposed to alleviate the problems mentioned above by effectively accommodating the strain induced by volume change and providing a short path for charge conduction [12–22]. For instance, several experimental works have demonstrated that Co3O4 spinels with properly tailored nanostructures deliver high Li storage capacities (ca. 800–1200 mAh g−1), and at the same time, they exhibit stable cyclability [12, 13, 16, 20, 21].
A mixed transition metal oxide, NiCo2O4, is also of significant interest because it exhibits higher electrical conductivity and electrochemical activities toward the conversion reaction with Li in comparison to Co3O4 [23–27]. As an example, Li et al. reported that the mesoporous NiCo2O4 anode exhibits a high specific capacity of ~1200 mAh g−1 as well as stable cycling performance for ~500 cycles . On the other hand, there are only a few reports on the electrochemical Na storage behavior of NiCo2O4 for NIBs [28–30]. Alcántara et al. were the first to demonstrate that NiCo2O4 has the ability to store Na through the conversion reaction similar to that of Li . In their report, however, the NiCo2O4 powder prepared by precipitation of oxalate precursors delivered only a reversible capacity of 200 mAh g−1 in a Na half-cell and displayed a significant capacity decay within 5 cycles. A recent study reported an interesting result showing that NiCo2O4 nanowires grown on a carbon cloth exhibit enhanced Na storage capability with stable cyclability . This indicates that, as shown previously in the studies on LIBs, the controlled nanostructural engineering of NiCo2O4 could be an effective approach to improving Na storage performance.
Here, we report a nanostructured NiCo2O4 anode for NIBs, i.e., a carbon-, binder-free (oxide-only) NiCo2O4 nanoneedle array (NCO-NNA) deposited on a conducting substrate. In addition to the feasibility study of NCO-NNA as an anode for NIBs, we provide an in-depth structural and electrochemical analysis on the Na storage reaction (sodiation and desodiation) in the nanostructured oxide-only electrode. The spinel-type NCO-NNA electrode was directly grown on a conducting Ni substrate by a hydrothermal method without using any conducting carbon or binders. The electrochemical Na storage behavior of NCO-NNA was examined and compared with that of Li. Particularly, the conversion reaction of NCO-NNA with Na was investigated using ex situ structural and chemical analyses during the sodiation–desodiation processes, and then, the performance difference of NCO-NNA in Na and Li half-cells was discussed based on the reaction pathways involved in Na and Li storage.
A spinel-type NCO-NNA was directly deposited on a conducting substrate using a hydrothermal method combined with post-heat treatment. The requisite metal precursors (Co(NO3)2 · 6H2O and Ni(NO3)2 · 6H2O) and urea (CO(NH2)2) were dissolved in deionized water, and then, the resulting solution was transferred to a Teflon-lined stainless steel autoclave. A nickel foam substrate was placed in the solution, and the autoclave was kept at 120 °C for 9 h. During the hydrothermal process, a mixed metal hydroxide was formed on the Ni substrate. The hydroxide-deposited substrate was thoroughly washed with ethanol and water, then dried under vacuum at 80 °C, and finally heat-treated in air at 350 °C for 3 h to convert the metal hydroxide to NiCo2O4. The weight of NiCo2O4 on the Ni substrate was 2.8 mg cm−2. For comparison, NiCo2O4 powder (NCO-P) was also obtained under the same hydrothermal and heat treatment conditions in the absence of the Ni foam substrate.
Phase and crystal structure analysis was conducted with an automated HPC-2500 X-ray diffractometer (Gogaku) using Cu K α radiation (λ = 1.5405 Å). The morphology, microstructure, and composition of the synthesized samples were examined by scanning electron microscopy (SEM, Hitachi S4700) and transmission electron microscopy (TEM, TECNAI G2 F30S-Twin) in conjunction with energy-dispersive X-ray spectroscopy (EDS). X-ray photoelectron spectroscopy (XPS) was performed using a Thermo MultiLab 2000 system with a monochromatic Al K α X-ray source. Brunauer–Emmett–Teller (BET) surface area was determined from N2 sorption isotherms by using a BEL-SORP mini system.
Electrochemical experiments were conducted using a coin-type cell (CR2032). The NCO-NNA on the Ni substrate was directly used as the working electrode for both Na and Li half-cells. For a Na half-cell, a Na metal (Aldrich) and 1 M NaClO4 in propylene carbonate (PC) with 5 wt.% fluoroethylene carbonate (FEC) were employed as the counter electrode and electrolyte, respectively. On the other hand, the Li half-cell was made of a Li metal and 1 M LiPF6 in ethylene carbonate (EC)/diethyl carbonate (DEC) (1:1 in volume). The separator was a glass fiber sheet. All of the cells were assembled in a glove box filled with purified Ar gas. The galvanostatic charge–discharge experiments were performed with a Maccor Series 4000 at various current densities in a voltage range of 0.01–3.0 V vs. Na/Na+ or Li/Li+. Electrochemical impedance spectra were obtained by using a Zahner IM6 with an ac amplitude of 5 mVrms on an open-circuit voltage during a frequency sweep from 105 Hz down to 10−2 Hz.
Morphological and Physicochemical Characteristics of NiCo2O4 Nanoneedle Array (NCO-NNA)
In this work, a spinel-type NCO-NNA was directly grown on a Ni substrate without using any conducting carbon or binders. When used as an electrode for NIBs, this oxide-only nanostructured design would offer the following advantages over conventional composite electrodes made of large particle agglomerates: (i) the nanoneedle architectures synthesized here provide an increased number of active sites for the electrochemical reaction, resulting in improved Na storage capability; and (ii) one can avoid any complications arising from inactive materials (conducting carbon and binders) and thus probe exclusively the physicochemical changes of the electrode induced by electrochemical sodiation and desodiation.
Comparative Electrochemical Study on Li and Na Storage Performance of NCO-NNA
As a next step, a Na half-cell was constructed using NaClO4 in PC with FEC as the electrolyte and tested with the NCO-NNA working electrode, and the discharge (sodiation) and charge (desodiation) curves obtained for the first 10 cycles are presented in Fig. 4b. According to the previous studies [31, 32], FEC plays a beneficial role in improving the structural integrity of anodes in Na half-cells by inducing the formation of stable SEI layers in carbonate-based electrolytes. The electrode was discharged to a cutoff voltage of 0.01 V vs. Na/Na+ and then recharged to 3.0 V vs. Na/Na+. The NCO-NNA electrode delivered 621 and 400 mAh g−1 (Coulombic efficiency ~64 %) during the first discharge and charge processes, respectively. It is seen that, while a single plateau appeared for lithiation, two distinct plateau regions were observed for the sodiation reaction of NCO-NNA: (i) a potential plateau (denoted by A 1) at ~0.6 V vs. Na/Na+; and (ii) a potential plateau (denoted by A 2) at ~0.1 V vs. Na/Na+ (~310 mAh g−1). During subsequent discharge–charge cycles, the NCO-NNA electrode showed improved reversibility with discharge–charge capacities of ~400 mAh g−1 and Coulombic efficiency of ~91 %.
Remarks on the Lithiation and Sodiation Reactions of NCO-NNA
first discharge (lithiation)
first charge (delithiation) and subsequent cycles
first discharge (sodiation)
first charge (desodiation) and subsequent cycles
In summary, we developed a carbon- and binder-free NiCo2O4 nanoneedle array for use as an NIB anode, which was fabricated on a conducting substrate by the hydrothermal method with subsequent heat treatment. When tested in the Na half-cell, the NCO-NNA electrode exhibits a considerably improved cycle performance over the conventional composite electrode. The enhanced performance of NCO-NNA is mainly due to the unique electrode nanoarchitecture, which provides an increased number of active sites for the Na storage while facilitating mass transport through the porous 1D structure and reducing the contact resistance with current collector. However, the comparative electrochemical study on Li and Na storage revealed that the Na storage performance of NCO-NNA is inferior to that of Li in terms of capacity, cycling stability, and rate capability, which could be explained by the reduced kinetics and reversibility of the conversion reaction with Na involving Na2O formation and decomposition.
This work was supported by the R&D Convergence Program (National Research Council of Science & Technology, Project No. CAP-14-2-KITECH).
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- Palomares V, Serras P, Villaluenga I, Hueso KB, Carretero-González J, Rojo T (2012) Na-ion batteries, recent advances and present challenges to become low cost energy storage systems. Energy Environ Sci 5:5884–901View ArticleGoogle Scholar
- Kim SW, Seo DH, Ma X, Ceder G, Kang K (2012) Electrode materials for rechargeable sodium-ion batteries: potential alternatives to current lithium-ion batteries. Adv Energy Mater 2:710–21View ArticleGoogle Scholar
- Slater MD, Kim D, Lee E, Johnson CS (2013) Sodium-ion batteries. Adv Funct Mater 23:947–58View ArticleGoogle Scholar
- Pan H, Hu YS, Chen L (2013) Room-temperature stationary sodium-ion batteries for large-scale electric energy storage. Energy Environ Sci 6:2338–60View ArticleGoogle Scholar
- Klein F, Jache B, Bhide A, Adelhelm P (2013) Conversion reactions for sodium-ion batteries. Phys Chem Chem Phys 15:15876–87View ArticleGoogle Scholar
- Dahbi M, Yabuuchi N, Kubota K, Tokiwa K, Komaba S (2014) Negative electrodes for Na-ion batteries. Phys Chem Chem Phys 16:15007–28View ArticleGoogle Scholar
- Han MH, Gonzalo E, Singh G, Rojo T (2015) A comprehensive review of sodium layered oxides: powerful cathodes for Na-ion batteries. Energy Environ Sci 8:81–102View ArticleGoogle Scholar
- Clément RJ, Bruce PG, Grey CP (2015) Review-manganese-based P2-type transition metal oxides as sodium-ion battery cathode materials. J Electrochem Soc 162:A2589–604View ArticleGoogle Scholar
- Kang H, Liu Y, Cao K, Zhao Y, Jiao L, Wang Y et al (2015) Update on anode materials for Na-ion batteries. J Mater Chem A 3:17899–913View ArticleGoogle Scholar
- Poizot P, Laruelle S, Grugeon S, Dupont L, Tarascon JM (2000) Nano-sized transition-metal oxides as negative-electrode materials for lithium-ion batteries. Nature 407:496–9View ArticleGoogle Scholar
- Hu J, Li H, Huang X, Chen L (2006) Improve the electrochemical performances of Cr2O3 anode for lithium ion batteries. Solid State Ionics 177:2791–9View ArticleGoogle Scholar
- Li Y, Tan B, Wu Y (2008) Mesoporous Co3O4 nanowire arrays for lithium ion batteries with high capacity and rate capability. Nano Lett 8:265–70View ArticleGoogle Scholar
- Yao W, Jang J, Wang J, Nuli Y (2008) Multilayered cobalt oxide platelets for negative electrode material of a lithium-ion battery. J Electrochem Soc 155:A903–8View ArticleGoogle Scholar
- Cabana J, Monconduit L, Larcher D, Palacin MR (2010) Beyond intercalation-based Li-ion batteries: the state of the art and challenges of electrode materials reacting through conversion reactions. Adv Mater 22:E170–92View ArticleGoogle Scholar
- Kim SW, Lee HW, Muralidharan P, Seo DH, Yoon WS, Kim DK et al (2011) Electrochemical performance and ex situ analysis of ZnMn2O4 nanowires as anode materials for lithium rechargeable batteries. Nano Res 4:505–10View ArticleGoogle Scholar
- Xue XY, Yuan S, Xing LL, Chen ZH, He B, Chen YJ (2011) Porous Co3O4 nanoneedle arrays growing directly on copper foils and their ultrafast charging/discharging as lithium-ion battery anodes. Chem Commun 47:4718–20View ArticleGoogle Scholar
- Yu L, Zhang L, Wu HB, Zhang G, Lou XW (2013) Controlled synthesis of hierarchical CoxMn3-xO4 array micro-/nanostructures with tunable morphology and composition as integrated electrodes for lithium-ion batteries. Energy Environ Sci 6:2664–71View ArticleGoogle Scholar
- Hariharan S, Saravanan K, Ramar V, Balaya P (2013) A rationally designed dual role anode material for lithium-ion and sodium-ion batteries: case study of eco-friendly Fe3O4. Phys Chem Chem Phys 15:2945–53View ArticleGoogle Scholar
- Huang B, Tai K, Zhang M, Xiao Y, Dillon SJ (2014) Comparative study of Li and Na electrochemical reactions with iron oxide nanowires. Electrochim Acta 118:143–9View ArticleGoogle Scholar
- Wen JW, Zhang DW, Zang Y, Sun X, Cheng B, Ding CX et al (2014) Li and Na storage behavior of bowl-like hollow Co3O4 microspheres as an anode material for lithium-ion and sodium-ion batteries. Electrochim Acta 132:193–9View ArticleGoogle Scholar
- Qiu HJ, Liu L, Mu YP, Zhang HJ, Wang Y (2015) Designed synthesis of cobalt-oxide-based nanomaterials for superior electrochemical energy storage devices. Nano Res 8:321–39View ArticleGoogle Scholar
- Hwang SM, Kim SY, Kim JG, Kim KJ, Lee JW, Park MS et al (2015) Electrospun manganese–cobalt oxide hollow nanofibres synthesized via combustion reactions and their lithium storage performance. Nanoscale 7:8351–5View ArticleGoogle Scholar
- Li J, Xiong S, Liu Y, Ju Z, Qian Y (2013) High electrochemical performance of monodisperse NiCo2O4 mesoporous microspheres as an anode material for Li-ion batteries. ACS Appl Mater Interfaces 5:981–8View ArticleGoogle Scholar
- Liu J, Liu C, Wan Y, Liu W, Ma Z, Ji S et al (2013) Facile synthesis of NiCo2O4 nanorod arrays on Cu conductive substrates as superior anode materials for high-rate Li-ion batteries. CrystEngComm 15:1578–85View ArticleGoogle Scholar
- Li L, Cheah Y, Ko Y, Teh P, Wee G, Wong C et al (2013) The facile synthesis of hierarchical porous flower-like NiCo2O4 with superior lithium storage properties. J Mater Chem A 1:10935–41View ArticleGoogle Scholar
- Zhang D, Yan H, Lu Y, Qiu K, Wang C, Zhang Y et al (2014) NiCo2O4 nanostructure materials: morphology control and electrochemical energy storage. Dalton Trans 43:15887–97View ArticleGoogle Scholar
- Zhou X, Chen G, Tang J, Ren Y, Yang J (2015) One-dimensional NiCo2O4 nanowire arrays grown on nickel foam for high-performance lithium-ion batteries. J Power Sources 299:97–103View ArticleGoogle Scholar
- Alcántara R, Jaraba M, Lavela P, Tirado JL (2002) NiCo2O4 spinel: first report on a transition metal oxide for the negative electrode of sodium-ion batteries. Chem Mater 14:2847–8View ArticleGoogle Scholar
- Mo Y, Ru Q, Chen J, Song X, Guo L, Hu S et al (2015) Three-dimensional NiCo2O4 nanowire arrays: preparation and storage behavior for flexible lithium-ion and sodium-ion batteries with improved electrochemical performance. J Mater Chem A 3:19765–73View ArticleGoogle Scholar
- Zhou K, Hong Z, Xie C, Dai H, Huang Z (2015) Mesoporous NiCo2O4 nanosheets with enhance sodium ion storage properties. J Alloy Compd 651:24–8View ArticleGoogle Scholar
- Li W, Chou SL, Wang JZ, Kim JH, Liu HK, Dou SX (2014) Sn4+xP3@amorphous Sn-P composites as anodes for sodium-ion batteries with low cost, high capacity, long life, and superior rate capability. Adv Mater 26:4037–42View ArticleGoogle Scholar
- Jang JY, Lee Y, Kim Y, Lee J, Lee SM, Lee KT et al (2015) Interfacial architectures based on a binary additive combination for high-performance Sn4P3 anodes in sodium-ion batteries. J Mater Chem A 3:8332–8View ArticleGoogle Scholar