C Each Other With An

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Black Phosphorus Stabilizing Na2Ti3O7/C Each Other With An Improved Electrochemical Property for Sodium Ion Storage Tianbing Song, Hai Chen, Qunjie Xu, Haimei Liu, Yong-Gang Wang, and Yong-Yao Xia ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b14971 • Publication Date (Web): 10 Oct 2018 Downloaded from http://pubs.acs.org on October 11, 2018

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ACS Applied Materials & Interfaces

Black Phosphorus Stabilizing Na2Ti3O7/C Each Other With An Improved Electrochemical Property for Sodium Ion Storage

Tianbing Song†, Hai Chen†, Qunjie Xu†, Haimei Liu†,* Yong-Gang Wang‡,* Yongyao Xia‡

†Shanghai

Key Laboratory of Materials Protection and Advanced Materials in Electric

Power, College of Environmental and Chemical Engineering, Shanghai University of Electric Power, Shanghai 200090, China ‡Department

of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and

Innovative Materials, Institute of New Energy, Fudan University, Shanghai 200433, China. * The authors to whom correspondence should be addressed, E-mail: [email protected] (H. Liu), [email protected] (Y. Wang)

KEYWORDS: Sodium-ion batteries, Na2Ti3O7, black phosphorus, P-O-Ti bonds, P-C bonds.

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ABSTRACT: Sodium-ion batteries have increasingly been considered as an attractive alternative to lithium ion batteries for large-scale applications. High specific capacity and suitable working potential anode materials are one of the keys to search for future developments. Here, a novel and stable sodium titanate/carbon-black phosphorus (NTO/C-BP) hybrids are firstly fabricated as promising anode material for advanced sodium-ion batteries. Under the protection of argon (Ar) atmosphere, the direct high energy mechanical milling of black phosphorus (BP) nanoparticle and sodium titanate/carbon (NTO/C) result in the formation of NTO/C-BP hybrids. In other words, BP nanoparticle can be interconnected with bare NTO by P-O-Ti bonds and/or form stable P-C bonds with the carbon coating layer on the surface of NTO. The NTO/C-BP hybrids are not only beneficial for enhancing specific capacity but also have a great protective effect on the exposure of black phosphorus to air by the synergistic effect between BP and NTO/C. The results show that the NTO/C-BP hybrids can deliver very high specific capacity (∼225 mA h g-1 after 55 cycles at 20 mA g-1, ∼183 mA h g-1 after 100 cycles at 100 mA g-1). We are expected this scientific findings that forming stable P-C bonds and P-O-Ti bonds in this work can serve as a guidance to other Ti-based and P-based electrode materials for practical large-scale application of sodium-ion batteries.

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1. INTRODUCTION Sodium ion batteries (SIBs) are receiving remarkable attention and possess high expectations as one of the most promising alternatives to lithium ion batteries (LIBs) for large-scale energy storage because of the natural abundance, low cost and very suitable redox potential.1-3 There are many physical and chemical property similarities between the two types of batteries. Therefore, numerous efforts have been undertaken to replace lithium with sodium on the basis of the already developed cathode and anode materials of LIBs. Among multitudinous materials, such as layered NaxMO2 (M = Ni, Fe, Co , etc.), NASICON and olivine,4, 5 have shown that they exhibit similar electrochemical behavior comparing with LIBs cathodes, As a consequence, looking for affordable and available anode materials is very urgent to further realize the practical application and commercialization of SIBs. Actually, numerous efforts have been devoted to searching practical available anode materials for SIBs, such as carbon-based materials,6,

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metal oxide materials,8,

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intermetallic alloys,10,

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titanium-based materials12, 13 and nonmetallic substance.14, 15 However, all of these anode materials are still far from practical applications, therefore, to development of high-performance anode materials and their relevant composites of SIBs is still a much-needed and highly desired task. Among all above-mentioned anode materials for SIBs, Na2Ti3O7 (NTO) is regarded as a very promising anode material because of its competitive theoretical capacity (∼177 mA h g-1) with a reasonable working potential (∼0.3 V vs Na+/Na).16, 17

However, the structural instability and poor electronic conductivity remain to be a 3



major obstacle for its practical application. In order to solve these drawbacks, the design of NTO nanostructures had been extensively studied in previous report, including nanoparticles, nanorods, nanotubes, microspheres, the formation of nanocomposites with carbon and carbon nanotubes.18-22 In our previous work, a novel ultra-long Na2Ti3O7 nanowires@carbon cloth (L-NTO NW) were successfully synthesized through one-pot hydrothermal method.23 This L-NTO NW exhibits excellent cyclability which the capacity retention is over 96% after 200 cycles at 2C, and the subsequent cycling at 3C, a discharge capacity of 100.6 mA h g-1 can be still maintained after 300 cycles. In fact, there are a large variety of nano-structured Na2Ti3O7 materials having been studied, and their electrochemical performance are better than powder materials. Nevertheless, compared with nano-structure materials, powder materials are more conducive to large-scale production. Unfortunately, using the powder NTO as anode materials for SIBs has significant drawbacks, including low specific capacity and fast capacity fading. Consequently, a considerable efforts had been made to increasing the specific capacity of NTO. In most recent, black phosphorus (BP) becomes another focus of studying as an attractive anode material for SIBs, which can electrochemically react with Na atoms to form Na3P and give a high theoretical capacity of 2595 mA h g-1,24 much higher than that of carbonaceous materials,25 metal oxide materials,26 alloy-type anode materials,27 and sulfides anode materials.28,

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It also has a low voltage platform

(∼0.3V vs Na+/ Na) which is quite close to that of NTO. Moreover, The structure of BP is similar to graphite with larger interlayer spacing and can be mechanically 4


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exfoliated few layer or monolayer black phosphorus from bulk black phosphorus.30 Consequently, BP has been attracting increasing attention in various fields which include secondary batteries,31 field-effect transistors,32 photocatalysis,33 and photodetectors.34 Xu et al. reported an black phosphorus/Ketjenblack-multiwalled carbon nanotubes (BPC) composite by high energy ball milling for sodium-ion batteries, which can deliver a very high capacity (~1700 mA h g-1 in 100 cycles at 1.3 A g-1).31 However, the BPC composite must be insulated from air and water during the whole preparation process, which makes it much difficult to be mass production. Sun and co-workers had successfully fabricated stable phosphorus-carbon bonds to enhance performance in a chemical-mechanical reaction process.35 The strategy of designing P-C bonds can stabilize the volume expansion (around 300%) of black phosphorus during lithium insertion/extraction. Therefore, taking the black phosphorus into practical application must solve more serious problem. In this work, we have successfully fabricated high performance NTO/C-BP hybrids anode for the first time by an easily scaled high energy ball milling NTO/C and BP nanoparticle. On the one hand, the capacity of NTO is compensated by the sodium storage behavior of BP so as to improve the specific capacity of electrode materials. On the other hand, BP can form strong P-O-Ti bonds with bare NTO, and meanwhile form stable P-C bonds with the carbon coating layer on the surface of NTO, which can conversely stabilize black phosphorus and reduce the volume expansion caused by Na+ insertion/extraction. These NTO/C-BP hybrids electrode

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materials demonstrate improved electrochemical performance owing to the strong synergistic interaction between the NTO/C and BP nanoparticle. 2. EXPERIMENTAL SECTION 2.1 Materials preparation Synthesis of sodium titanate (NTO): The preparation procedure of NTO was synthesized via a simple sol-gel process in our previous work.12 First, 0.03mol of sodium acetate anhydrous (C2H3O2Na) as a sodium source and 0.036mol of critic acid as a carbon source were dissolved in 200ml anhydrous ethanol until they were completely dissolved. Then, 0.03mol of tetrabutyl titanate (C16H36O4Ti) and 10ml acetic acid were added in the above solution until they dissolve uniformly. Then, the solution is subjected to heating while it is being stirred at 100°C for 2h. After placing the precursors in vacuum oven overnight to get a white powder, the resulting obtained powder were calcined to form the NTO/C material. Synthesis of BP nanoparticle: BP crystal was synthesized by mechanically grinding red phosphorus (RP) (99.999%, Aladdin) with planetary ball-mill instrument.35 Red phosphorus (9 g) and stainless steel balls (7, 25 mm in diameter; 15, 10 mm in diameter; 40, 4 mm in diameter) were put into a stainless steel vessel having a capacity of 100 ml which was filled with argon (Ar). After that, the rotation speed of the ball-milling process was set to 500 rpm for 24 h. This procedure is applied to transform RP into BP. The obtained BP needs to be protected under argon-filled glove box. Synthesis of NTO/C-BP hybrids: The NTO/C-BP hybrids were assembled by the 6


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high energy mechanical milling technique the mixtures of NTO/C and BP nanoparticle with a rotation speed of 700 rpm for 12 h under argon (Ar) atmosphere. The mixed powder (1 g) with various NTO/BP molar ratio from 3/1 to 5/1 which the optimal sample is 4/1, as well as stainless steel balls (4, 5 mm in diameter; 20, 2 mm in diameter; 30, 1 mm in diameter), were put into a stainless steel vessel having a capacity of 50 ml. The corresponding NTO/C-BP hybrids can be obtained. 2.2 Materials characterization. Power X-Ray diffraction (XRD) was collected on a Bruker D8 advanced. The SEM images and TEM images were obtained using by field emission scanning electron microscopy (SEM, Zeiss Supra 55) and high-resolution transmission electron microscopy (HRTEM, JEM 2100F). Raman experiments were carried out using a labRAM ARAMIS laser Raman spectroscopy. The specific surface area was tested using an ASAP-2010 surface area analyzer by the BET measurements. The carbon content of NTO/C was determined by TGA. Fourier transform infrared spectrometry (FTIR, Dao Jin 8400S) was performed on a Bruker Vertex V70 spectrometer. X-ray photoelectron spectroscopy (XPS) measurements were carried out on a PHI Quantera SXM scanning X-ray microprobe. 2.3 Electrochemical measurement. Electrochemical performance of all electrode materials was examined using coin-type (type CR2016) cells with sodium foil as counter. The all electrode materials were prepared by mixing of polyvinylidene difluoride, Super P and active material (1:2:7) onto a copper foil current collector which the average mass load was approximately 1.5-2 mg without no gas protection. 1 M NaPF6 in ethylene carbonate-diethyl carbonate (EC-DEC, 1:1 volume ratio) with 7



5 vol% fluoroethylene carbonate (FEC) was used as the electrolyte and a glass fiber film (Whatman GF/C) was used as the separator. The electrochemical data was collected using LAND CT2001A test system (Wuhan, China) at various current densities. Electrochemical impedance spectroscopy (EIS) and Cyclic voltammetry (CV) measurements were performed using a CHI650D (Chenhua, Shanghai) electrochemical workstation. 3. RESULTS AND DISCUSSION

The fabrication procedure of the sodium titanate/carbon-black phosphorus (NTO/C-BP) hybrids are schematically shown in Figure 1. First of all, the preparation procedure of NTO/C was obtain through a simple sol-gel method. Meanwhile BP nanoparticle was synthesized by mechanically grinding red phosphorus (RP) with planetary ball-mill instrument. Then the NTO/C and BP nanoparticle were fabricated by high energy ball-milling to obtain NTO/C-BP hybrids. In previous studies, BP nanoflakes can interconnect by TiO2 with strong P-O-Ti.36 In addition, BP and various carbon sources can be fabricated with stable P-C bonds.35, 37 Hence we are looking forward to preparation of a NTO/C-BP hybrids electrode through NTO/C and BP by their stabilizing effects each other. The BP can form strong P-O-Ti bonds with bare NTO, and/or meanwhile form stable P-C bonds with the carbon coating layer on the surface of NTO, the high capacity contribution from BP makes it possible that a stable and high capacity anode of NTO/C-BP is expectative.

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The microstructures of the BP nanoparticle, NTO/C and NTO/C-BP hybrids were observed by SEM. The BP nanoparticle was synthesized by direct mechanically grinding RP with planetary ball-mill instrument. In Figure 2a, the bulk BP particles are about several hundreds of nanometers, which show a very apparent reunion. In Figure 2b, irregular several layer BP nanosheets could be observed on the edge of magnification. NTO/C sample was synthesized by one-step sol-gel way. Hence, the structure of NTO/C particles is very irregular which mainly contains powder, flake and nanorods morphology (Figure 2c, d). Moreover, the SEM elemental mapping of the NTO/C sample presents Na, O, Ti and C elements (Figure S1). After high energy ball-milling, these large BP particles and NTO/C rods cannot be observed in Figure 2e, f. They are fabricated to form a homogeneously nanostructure possessing more uniform contacts with the electrolyte. The NTO/C-BP hybrids with a particle size of about 200nm can be observed. Besides, the SEM elemental mapping in Figure 2h-l demonstrates uniform presence of C, Na, Ti, O, and P elements in the NTO-BP hybrids.

The BET specific surface area of the all samples was carried out by nitrogen adsorption-desorption isotherms. As shown in Figure 3a, the BET surface area of the primal BP and NTO/C are 14.07 and 111.71 m2 g-1, respectively. However, the BET surface area of NTO/C-BP hybrids exhibits 28.1 m2 g-1 after the high energy ball-milling. In addition, the mesoporous structural feature in Figure S2 (predominant 9



pore size: 10-40 nm) of the NTO/C-BP increased after the combination of NTO/C and BP, because the NTO/C is dispersed into the black phosphorus during the process of high energy ball-milling. The XRD analyses were measured to explore the crystal structures of the different products. Figure 3b shows the XRD patterns of BP and NTO/C-BP hybrids. The major characteristic diffraction peaks of pure BP are indexed (JCPDS card no. 74-1878). The peak centers at 16.874°, 26.48°, 35°, 50.691° and 55.476° are clearly observed, corresponding to (002), (012), (111), (121), and (200) crystal faces. In addition, all the diffraction peaks of NTO/C-BP hybrids are indexed to BP and NTO/C (JCPDS card no. 31-1329). Obviously, it exhibits a peak at 35° which corresponds to typical (111) reflections of the BP. At the same time, the phase structures of commercial red phosphorus were also characterized by XRD. Figure S3a shows the color photo image and XRD pattern. The peak centers at 16.614°and 31.542°are clearly observed, corresponding to (102) and (026) crystal faces. This more strongly confirms the conversion of red phosphorus to black phosphorus through the color photo image comparison (inset Figure S3a). Figure S3b shows XRD pattern of NTO/C before the ball milling. The peak centers at 10.523 ° , 15.841°,19.846°, 25.696°, 43.915°, and 47.807° are clearly observed, corresponding to (001), (101), (200 ), (011), (401), and (020) crystal faces. NTO/C-BP hybrids still have the characteristic peaks of NTO/C after high energy mechanical milling which proves that the structure of NTO is very stable.

The structural of the BP, NTO/C and NTO/C-BP hybrids have been investigated by Raman. In Figure 3c, three prominent peaks at 362, 435, and 466 cm-1 can be 10


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observed in Raman spectroscopy of BP, are ascribed to one out-of-plane phonon mode (A1g), and two in-plan modes (B2g and A2g), respectively.38 The characteristic peaks of carbon materials can be attributed to the sp3-typed D and sp2-typed G bands in the Raman spectra of NTO/C and NTO/C-BP hybrids. Compared to NTO/C sample with ID/IG = 1.09, the NTO/C-BP samples shows a lager peak intensity ration of the D to G bands (ID/IG = 1.19), indicating the defective degree becomes larger after addition of black phosphorus, and is beneficial to Na+ insertion/extraction. Meanwhile, several minor peaks match well with the typical characteristic peaks of BP in NTO/C-BP hybrids.39 A broad peak centered at ∼750 cm-1 of NTO/C-BP hybrids (inset in Figure 3c) appears which falls right in this range (650-770 cm-1) for P-C bond in the previous literature report.40-42 In addition, compared to the G band of the NTO/C at about 1610 cm-1, the G band of the NTO/C-BP hybrids slightly shifts to a lower wavenumber (∼1580 cm-1) because of the π-p* conjugation, which further suggests the formation of P-C bonds. The interaction between NTO/C, BP nanoparticles and NTO/C-BP hybrids were further investigated by FT-IR in Figure 3d. Typically, there covers a thin layer of phosphorus-based oxides on the surface of BP due to the oxidative effects of exposure to air in the measurement. Therefore, the FT-IR spectra of BP appears P=O (~1620 cm-1) and P-O (~1000 cm-1) characteristic peaks.43, 44 The peaks located at 455, 542, 715, 850 and 941 cm-1 are assigned to the bending and stretching vibrations of Ti-O bonds in TiO6 octahedra for Na2Ti3O7 of NTO/C and NTO/C-BP hybrids.45 It is worth noting that the peaks of NTO/C-BP hybrids located at 1050 cm-1 may be appearance of P-O-Ti bonds. This result will be proved by TEM and XPS later. 11



The specific morphology and microstructure of the BP, NTO/C and NTO/C-BP hybrids were further performed by TEM and HRTEM. The TEM image (Figure 4a) of the BP nanoparticles also substantiates that the particle size is about 300~400nm. Meanwhile irregular layer BP nanosheets are also observed. In the Figure 4b HRTEM image is the BP nanoparticles. The lattice spacing of 0.336nm and 0.26nm corresponds to the (012) and (004) face. The orthorhombic phase of BP is confirmed by selected area electron diffraction (SAED) patterns as shown in the inset of Figure 3a. (002), (012), (111), (121), (200) and (115) planes were identified (JCPDS card no. 74-1878), which is in accordance with the HRTEM and XRD results. Figure 4c and 4d show the TEM images and HRTEM images of the NTO/C, which explicitly show the uneven particle size of NTO and the surface decoration of NTO by carbon coating layer. In addition, Figure 4d obviously proves the lattice spacing of NTO crystal is 0.314 nm, corresponding to the (111) planes. Moreover, we can observe a very thin carbon coated layer appearing on the NTO. For confirming the contents of NTO and carbon, TGA was explored in Figure S4, the content of the carbon is about 10.6 %. In Figure 4e, the TEM image of the NTO/C-BP hybrids further confirms that the particle size of the NTO/C-BP particles is about 200nm. The homogeneous particle is favorable for contacting with the electrolyte. The HRTEM image of the NTO/C-BP hybrids are shown in Figure 4f, which clearly identifies that NTO nanoparticles with crystal lattices which are labeled by dotted line circles and BP assemblies are well connected in the NTO/C-BP hybrids. In addition, the lattice spacing were also measured to be 0.336nm and 0.256nm from the HRTEM image, corresponding to the 12


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(012) and (111) plane of BP. This result supplies evident evidence that NTO/C interconnects with BP nanoparticle via P-O-Ti bonds and P-C bonds. In addition, an appropriate carbon coating layer on the surface not only can increase the electronic conductivity but also provide a protection barrier against possible electrolyte degradation on the surface of electrode materials. Besides, the most important thing is that carbon layer can produce P-C bonds with BP nanoparticle in our study, which limits the volume expansion during sodium insertion/extraction, and protects black phosphorus from oxidation.

X-ray photoelectron spectroscopy (XPS) was employed to investigate the chemical state of the interactions among NTO/C and BP. The full survey of the all samples were shown in Figure 5a. The survey spectrum of the BP appears O element and this is further confirmed BP inevitably absorbs oxygen and moisture exposure to air on the BP surface. In contrast to the characteristic peaks of NTO/C, NTO/C-BP not only reveals the peaks of Na 1s, C 1s, O 1s and Ti 2p but also appears two new peaks which belong to P 2s and P 2p. As shown in the P 2p XPS spectrum (Figure 5b) of BP, the spectrum has been fitted to the 2 p3/2 and 2 p1/2 doublet, corresponding to a binding energy value 129.9 and 130.5 eV, respectively.35 The peak at 134.67 eV was due to the most common phosphorous oxides (PxOy) on the surfaces of the BP nanoparticles.46 After the reaction of BP with NTO/C, the high-resolution P 2p XPS spectrum of the NTO/C-BP (Figure 5c) shows that the characteristic peaks of 2p3/2 P-P (129.9 eV), 2p1/2 P-P (130.5 eV), 2p3/2 P-C (130.5 eV), 2p1/2 P-C (132.1 eV) ,P-O-C (132.9 eV) P-O-P (133.8 eV) and O-P-C=O (135 eV) are existed.37 It's 13



worth noting that there are two new peaks at 130.5 eV and 132.1 eV corresponding to P-C peaks, which demonstrates the chemical bonds formation between carbon layer and BP nanoparticles.

High-resolution C 1s XPS spectrum of NTO/C and NTO/C-BP are compared, exhibiting similar feature with one intense peak at 284.8 eV along and a broad peak in the region of 288-291 eV in Figure 6a. Despite of the similarity on the overall feature of the C 1s peaks of both NTO/C (Figure 6b) and NTO/C-BP (Figure 6c), they can be similarly deconvoluted into five peaks at 282.9 eV (C-O-Ti), 284.5 eV (C=C), 285 eV (C-O), 287.8 eV (C=O) and 288.9 eV (O-C=O). Whereas, discernible changes on the relative intensities of the P-C bond at 283.8 eV. The O1s XPS spectrum analysis was depicted in Figure 6d-f. Figure 6d shows visible difference between NTO/C and NTO/C-BP. There appears a broad peak at 535~538 eV for NTO/C-BP. In addition, five peaks at 529.4 eV, 530.5 eV, 531.1 eV, 531.8 eV and 532.9 eV, corresponding to O-Ti-O, O-Ti, C-O-Ti, OH-, H2O, respectively, the were viewed in O1s the XPS spectrum for the NTO/C sample in Figure 6e. Besides those signals, two additional peaks at 530.2 eV and 536.6 eV are observed for NTO/C-BP, which are allocated to P=O and P-O-P bond.46, 47 Importantly, the peak at around 531.3 eV can be ascribed to Ti-O-P bond, which demonstrates the bridging oxygen bonds formation between the BP nanoparticles and NTO/C. This result is similar to the P-O-Ti functionalized TiO2-BP, 34 implying that the BP is combined with ultrathin TiO2 nanosheets. In short, BP nanoparticle is interconnected by NTO with P-O-Ti bonds and can form stable P-C bonds with the carbon coating on the surface of NTO, which is beneficial for 14


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enhancing specific capacity but also has a great protective effect on the exposure of black phosphorus to air. In addition, Ti 2p of the NTO and NTO-BP sample are shown in Figure S5a and b, the peaks at around 463.8 and 458.1 eV are corresponded to the Ti 2p doublets (Ti2 p1/2 and Ti 2p3/2). In order to explore the electrochemical intercalation behavior of Na+, CV was performed with a scan rate of 0.1 mV s-1 in a voltage window of 0.01-2.5V (vs. Na+/ Na) in Figure 7a. The CV curve for NTO/C samples appears a pair of sharp redox peaks located at 0.1 and 0.35 V which could be due to the redox of the Ti4+/Ti3+ couple. However, when the CV was further analyzed for NTO/C-BP samples. The major reduction peak III with an evident similar shoulder shows between 0.3 and 0.1 V, which corresponds to reduction of Ti4+ and formation of NaxP. On the one hand, peaks I and II are viewing at 0.53 and 0.76, corresponding to a stepwise Na+ extraction from Na3P phase to form Na2P, and NaP intermediates, respectively.48-50 On the other hand, due to the addition of BP, the conductivity of NTO/C-BP is decreased, so the polarization of NTO/C-BP samples is larger than NTO/C, which makes oxidation potential of Ti positive shift and causes the oxidation peak of Ti3+ to overlap with the peak I during the extraction/insertion of sodium ions. On the contrary, the conductivity of NTO/C-BP is higher than that of pure BP nanoparticles as electrode material which can also be proved from the impedance later. In addition, the CV of NTO/C-BP electrode with various scan rates 0.1, 0.2 and 0.3 mV s-1 is displayed in Figure S6a. All the CV curves display the similar shapes, it can be seen that the potential polarization does not increase obviously with the increase of scan 15



rates. EIS tests of BP, NTO/C and NTO/C-BP samples were performed to explore the relationship between kinetics behaviors and electrochemical properties. The tests are measured in the frequency range of 1MHz to 10 mHz. The inset of Fig. S6b is the equivalent circuit model which can be used to fit the impedance data. The Rs, Rct, Wo and CPE represent the electrolyte resistance, charge-transfer resistance at the interface between the electrolyte and electrode, the diffusion behavior at low frequency, capacity of the surface layer and double layer capacitance, respectively. The Nyquist plots are composed of a single depressed semicircle in the high-medium frequency region and a sloping line at the low frequency, which respectively express the charge transfer and diffusion of sodium ions during the electrochemical process. In order to further analyze of impedance spectra, the inset of Fig. S6b is the equivalent circuit model which can be used to fit the impedance data. The specific EIS parameters are shown in Table S1. Based on the fitting results with equivalent circuit, the value of Rs is 2-4.5 Ω for three samples. The Rct value of the BP electrode (675.1 Ω) is much higher than that of the NTO/C-BP (326.7 Ω), which means that the NTO/C-BP electrode has a faster charge transfer process than the BP electrode. The electrochemical properties of all electrode materials were tested in the Na half-cells in sodium-ion batteries. Figure 7b and Figure S7a show the charging and discharging curves and cycling performance of BP. The rapid decrease of capacity may be caused by volume expansion. And black phosphorus is readily oxidized when exposed to air, therefore pure black phosphorus is not suitable for electrode materials. Figures 7c shows the charging and discharging curves of NTO/C, it clearly contains a 16


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visible discharge plateau at around 0.1V. This corresponds to a sharp redox peaks in CV of NTO/C (Figures 7a) .The initial discharge and charge capacities are about 417.5 and 170.1mA h g-1 at 20 mA g-1, respectively. It also maintains a capacity of 117.1mAh g-1 after 55 cycles. Obviously this capacity is not up to demand. Figures 7d shows the charging and discharging curves of NTO/C-BP. The charge/discharge process of NTO/C-BP may mainly involve (i) the two-phase insertion reaction between Na2Ti3O7 and Na4Ti3O7, (ii) Na+ extraction/insertion from black phosphorus The general sodiation curves consist of an oblique plateau from 0.5-0.10 V. which may correspond to a broad redox peaks in CV of NTO/C-BP (Figures 7a). Moreover, the cycling property of the NTO/C and NTO/C-BP hybrids are compared in Figure 8. Figure 8a demonstrates the cyclic property of the NTO/C-BP hybrids. The first discharge and charge capacity of the NTO/C-BP anode was tested to be 732.5 and 310.1mA h g-1 at 20 mA g-1. Then the NTO/C-BP electrode further exhibits its excellent cycling property after the 55th cycles. Its capacity was stable at 225.5 mA h g-1, and coulombic efficiency is up to 99.5%. Meanwhile, in order to explore the effect of the ratio of NTO to BP on performance of NTO/C-BP. Figure S7b researches the cycling performance of NTO/C-BP with various ratios from 3:1, 4:1 to 5:1 composite electrodes at 20 mA g-1. The NTO/C-BP 3:1 electrode has a high initial capacity but experiences significant decline in capacity after 65th cycles, with just a small amount of capacity (approximately 85 mA h g-1). On the contrary, the NTO/C-BP 4:1 electrode is almost no decay (190 mA h g-1 after 65th cycles). Besides, The NTO/C-BP 5:1 electrode has a lower capacity because less black phosphorus is 17



added. Therefore, we come to the conclusion that the NTO/C-BP 4:1 is more suitable for electrode materials. Then the NTO/C-BP 4:1 electrode was then tested at high current density, the discharge capacity of 94.3 and 183.6 mA h g-1 can be remained after 100 cycles for the NTO/C and NTO/C-BP at 100 mA g-1 (Figure 8b), respectively, suggesting higher specific capacity of NTO/C-BP than theoretical capacity of NTO (177 mA h g-1). Finally, the long cycling performance at 200 mA g-1 was tested (Figure 8c). Surprisingly, a reversible capacity of up to 143.3 mA h g-1 remains after 400 cycles. In contrast, the performance of the NTO/C is evidently inferior. Moreover, the capacity of this novel NTO/C-BP material is much superior to previous reported NTO/C nano-structured samples for SIBs (Table S2). However, we have to note that although the NTO/C-BP material is not up to its theoretical capacity (~17780%+259520%=660 mA h g-1), more and optimal work should be done in future, and herein we expect to provide an idea to increase the capacity of NTO and stabilize BP at the same time. 4. CONCLUSIONS In summary, for the first time, a stable NTO/C-BP hybrids anode material for SIBs can be successfully fabricated by a simple high energy ball-milling NTO/C and BP nanoparticle under argon protection. During the procedure, the NTO with carbon coating materials were crushed into small chipped NTO/C and interconnected with BP nanoparticle by the formation of bonds stable P-C bonds and strong P-O-Ti. Thanks to unique hybrids with NTO/C and BP, the as-prepared NTO/C-BP anode material can deliver very high specific capacity (∼225 mA h g-1 after 55 cycles at 20 mA g-1) as 18


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well as long cycling performance (∼143.3 mA h g-1 after 400 cycles at 200 mA g-1) and high coulombic efficiency (99.3%). The present results firstly show one of the competitive property of NTO/C-BP hybrids as a hopeful anode material for SIBs. Additionally, the findings of strong P-O-Ti bonds and stable P-C bonds provide an effective strategy to solve practical application problems of black phosphorus such as the commercialization and mass production. ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge. Elemental mapping, TG, XPS, XRD, of the NTO/C, BJH and color photo image of BP, XRD patterns and color photo image of RP, BJH and XPS of NTO/C-BP, CV of NTO/C-BP electrode at various sweep rates, impedance spectra of BP, NTO/C and NTO/C-BP, cycling performance of BP and various NTO/C-BP electrode materials at 20 mA g-1, table of EIS parameters and electrochemical performance of various Na2Ti3O7 materials. Notes The authors declare no competing financial interest. ACKNOWLEDGMENTS This work was financially supported by the National Nature Science Foundation of China (No. 21336003, 21371021), the National Key Research Program of China (No. 2016YFB0901500) and Science and Technology Commission of Shanghai Municipality (No: 14DZ2261000). 19



REFERENCES (1)

Slater, M. D.; Kim, D.; Lee, E.; C. Johnson S. Sodium-Ion Batteries. Adv. Funct. Mater., 2013, 23, 947-958.

(2)

Palomares, V.; Serras, P.; Villaluenga, I.; Hueso, K. B.; Carreterogonzález, J.; Rojo, T. Na-ion batteries, recent advances and present challenges to become low cost energy storage systems. Energy Environ. Sci., 2012, 5, 5884-5901.

(3)

Yabuuchi, N.; Kubota, K.; Dahbi, M.; Komaba, S. Research development on sodium-ion batteries. Chem. Rev., 2014, 114, 11636-11682.

(4)

Xiang, X.; Zhang, K.; Chen, J. ChemInform Abstract: Recent Advances and Prospects of Cathode Materials for Sodium-Ion Batteries. Adv. Mater., 2015, 27, 5343-5364.

(5)

Shen, W.; Li, Zh. H.; Wang ,C.; Li, Z.; Xu, Q.; Liu H. M.; Wang, Y. G. Improved electrochemical performance of Na3V2(PO4)3 cathode by B-doping of carbon coating layer for sodium-ion batteries. J. Mater. Chem. A, 2015, 3, 15190-15201.

(6)

Wang, G.; Wu, Z.; Meng, L.; Ma, L.; Huang, L.; Wang, L.; Zhang, X. Nitrogen-Doped Porous Carbon Nanosheets as Low-Cost, High-Performance Anode Material for Sodium-Ion Batteries. Chemsuschem, 2013, 6, 56-60.

(7)

Mondal, A. K.; Su, D.; Chen, S.; Xie, X.; Wang, G. Highly porous NiCo2O4 Nanoflakes and nanobelts as anode materials for lithium-ion batteries with excellent rate capability. Acs Appl. Mater. Inter., 2014, 6, 14827.

(8)

Dou Sh.; Tao, L. ; Wang, R. L.; Hankari, S. E.; Chen, R.; Wang, Sh. Y. Plasma-Assisted Synthesis and Surface Modification of Electrode Materials for Renewable Energy. Adv. Mater. 2018, 30, 1705850.

(9)

Xiong, H.; Slater, M. D.; Balasubramanian, M.; Johnson, C. S.; Rajh, T. Amorphous TiO2 Nanotube Anode for Rechargeable Sodium Ion Batteries. J. Phy. Chem. Lett., 2011, 2, 2560–2565.

(10)

Xu, Y.; Zhu, Y.; Liu, Y.; Wang, C. Electrochemical Performance of Porous 20


Page 20 of 34

Page 21 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Carbon/Tin Composite Anodes for Sodium-Ion and Lithium-Ion Batteries. Adv. Energy Mater., 2013, 3, 128-133. (11)

Wang, X.; Fan, L.; Gong, D.; Zhu, J.; Zhang, Q.; Lu, B. Core-Shell Ge@Graphene@TiO2 Nanofibers as a High-Capacity and Cycle-Stable Anode for Lithium and Sodium Ion Battery. Adv. Funct. Mater., 2016, 26, 1104-1111.

(12)

Song T. B.; Ye, Sh. Ch.; Liu, H. M.; Wang, Y. G. Self-doping of Ti3+ into Na2Ti3O7 increases both ion and electron conductivity as a high-performance anode material for sodium-ion batteries. J. Alloys Compd., 2018, 767, 820-828.

(13)

Ye, Sh. Ch.; Li, Zh. H.; Song T. B.; Cheng, D. H.; Xu, Q. J.; H. M.; Wang, Y. G. Self-generated Hollow NaTi2(PO4)3 Nanocubes Decorated with Graphene as a Large Capacity and Long Lifetime Anode for Sodium-ion Batteries. Rsc Adv., 2017, 7, 56743-56751.

(14)

Sun, J.; H. Lee, W.; Pasta, M.; Yuan, H.; Zheng, G.; Sun, Y.; Li, Y.; Cui, Y. A phosphorene-graphene hybrid material as a high-capacity anode for sodium-ion batteries. Nat. Nanotechnol., 2015, 10, 980-985.

(15)

Yue, C.; Yu, Y.; Sun, S.; He, X.; Chen, B.; Lin, W.; Xu, B.; Zheng, M.; Wu, S.; Li, J. Batteries: High Performance 3D Si/Ge Nanorods Array Anode Buffered by TiN/Ti Interlayer for Sodium-Ion Batteries. Adv. Funct. Mater., 2015, 25, 1385-1385.

(16)

Pan, H.; Lu, X.; Yu, X.; Hu, Y.; Li, H.; Yang, X.; Chen, L. Sodium Storage and Transport Properties in Layered Na2Ti3O7 for Room-Temperature Sodium-Ion Batteries. Adv. Energy Mater., 2014, 3, 1186-1194.

(17)

Rudola, A.; Saravanan, K.; Mason, C.; Balaya, P. Na2Ti3O7: an intercalation based anode for sodium-ion battery applications. J. Mater. Chem. A, 2013, 1, 2653-2662.

(18)

Wang, Q.; Zhao, C.; Lu, Y.; Li, Y.; Zheng, Y.; Qi, Y.; Rong, X.; Jiang, L.; Qi, X.; Shao, Y. Advanced Nanostructured Anode Materials for Sodium-Ion Batteries. Small, 2017, 13, 1701835.

(19)

Yan, Z.; Liu, L.; Shu, H.; Yang, X.; Wang, H.; Tan, J.; Zhou, Q.; Huang, Z.; 21



Page 22 of 34

Wang, X. A tightly integrated sodium titanate-carbon composite as an anode material for rechargeable sodium ion batteries. J. Power Sources, 2015, 274, 8-14. (20)

Zou, W.; Fan, C.; Li, J. Sodium Titanate/Carbon (Na2Ti3O7/C) Nanofibers via Electrospinning Technique as the Anode of Sodium-ion Batteries. Chin. J. Chem., 2017, 35, 79-85.

(21)

Wang, W.;Yu, C.; Liu, Y.; Hou, J.; Zhu, H.; Jiao, S. Single crystalline Na2Ti3O7 rods as an anode material for sodium-ion batteries. Rsc Adv., 2012, 3, 1041-1044.

(22)

Li, H.; Peng, L.; Zhu, Y.; Chen, D.; Zhang, X.; Yu, G. An Advanced High-Energy

Sodium

Ion

Full

Battery

Based

on

Nanostructured

Na2Ti3O7/VOPO4 Layered Materials. Energy Environ. Sci., 2016, 9, 3399-3405. (23)

Li, Z.; Shen, W.; Wang, C.; Xu, Q.; Liu, H.; Wang, Y.; Xia, Y. Ultra-long Na2Ti3O7 Nanowires@carbon Cloth as Binder-free Flexible Electrodes with a Large Capacity and Long Lifetime for Sodium-ion batteries. J. Mater. Chem. A, 2016, 4, 17111-17120.

(24)

Liu, H.; Hu, K.; Yan, D.; Chen, R.; Zou, Y.; Liu, H.; Wang, S. Recent Advances on Black Phosphorus for Energy Storage, Catalysis, and Sensor Applications. Adv. Mater., 2018, 30, 1800295.

(25)

Fan, L.; Lu, B. Carbonaceous electrode material for secondary battery. Small, 2016, 12 ,2783-2791.

(26)

Ding, J.; Li, Z.; Wang, H.; Cui, K.; Kohandehghan, A.; Tan, X.; Karpuzov, D.; Mitlin, D. Sodiation lithiation phase transformations in a high rate-high stability SnO in carbon nanocomposite. J. Mater. Chem. A, 2015, 3, 7100-7111.

(27)

Lao, M.; Zhang, Y.; Luo, W.; Yan, Q.; Sun, W.; Dou, S. X. Alloy-Based Anode Materials toward Advanced Sodium-Ion Batteries. Adv. Mater., 2017, 29. 1700622.

(28)

Park, J. S.; Kang, Y. C. Multicomponent (Mo, Ni) metal sulfide and selenide 22


Page 23 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


microspheres with empty nanovoids as anode materials for Na-ion batteries. J. Mater. Chem. A, 2017, 5, 8616-8623. (29)

Sun, W.; Rui, X.; Zhang, D.; Jiang, Y.; Sun, Z.; Liu, H.; Dou, S. Bismuth sulfide: A high-capacity anode for sodium-ion batteries. J. Power Sources, 2016, 309, 135-140.

(30)

Reich, E. S. Phosphorene excites materials scientists. Nature, 2014, 506, 19.

(31)

Xu, G.; Chen, Z.; Zhong, G.; Liu, Y.; Yang, Y.; Ma, T.; Ren, Y.; Zuo, X.; Wu, X.; Zhang, X.; Nanostructured Black Phosphorus/Ketjenblack-Multiwalled Carbon Nanotubes Composite as High Performance Anode Material for Sodium-Ion Batteries. Nano Lett., 2016, 16, 3955-3965.

(32)

Li, L.; Yu, Y.; Ye, G.; Ge, Q.; Ou, X.; Wu, H.; Feng, D.; Chen, X. H.; Zhang, Y. Black phosphorus field-effect transistors. Nat. Nanotechnol., 2014, 9, 372-377.

(33)

Zhu, M.; Cai, X.; Fujitsuka, M.; Zhang, J.; Majima, T. Au/La2Ti2O7 Nanostructures Sensitized with Black Phosphorus for Plasmon-Enhanced Photocatalytic Hydrogen Production in Visible and Near-Infrared Light. Angew. Chem., 2017, 56, 2064-2068.

(34)

Zhu, X.; Zhang, T.; Sun, Z.; Chen, H.; Guan, J.;

Chen, X.; Ji, H.; Du, P.;

Yang, S. Black Phosphorus Revisited: A Missing Metal-Free Elemental Photocatalyst for Visible Light Hydrogen Evolution. Adv. Mater., 2017, 29, 1605776. (35)

Sun, J.; Zheng, G.; Lee, H. W.; Liu, N.; Wang, H.; Yao, H.; Yang, W.; Cui, Y. Formation of stable phosphorus-carbon bond for enhanced performance in black phosphorus nanoparticle-graphite composite battery anodes. Nano Lett., 2012, 14, 4573-4580.

(36)

Wu, T.; Fan, J.; Li, Q.; Shi, P.; Xu, Q.; Min, Y. Min. Palladium Nanoparticles Anchored on Anatase Titanium Dioxide-Black Phosphorus Hybrids with Heterointerfaces: Highly Electroactive and Durable Catalysts for Ethanol Electrooxidation. Adv. Energy Mater., 2017, 8, 1701799.

(37)

Zhang, C.; Wang, X.; Liang, Q.; Liu, X.; Weng, Q.; Liu, J.; Yang ,Y.; Dai, Z.; 23



Page 24 of 34

Ding, K.; Bando, Y. Amorphous Phosphorus/Nitrogen-Doped Graphene Paper for Ultrastable Sodium-Ion Batteries. Nano Lett., 2016, 16, 2054. (38)

Lv, W. M.; Yang, B.; Wang, B.; Wan, W. H. Ge, Y.; Yang, R.; Hao, C.; Xiang, J.; Zhang, B.; Zeng, Z.; Liu, Z. Sulfur-doped black phosphorus field-effect transistors with enhanced stability. Acs Appl. Mater. Inter., 2018, 10, 9663-9668.

(39)

Li, W.; Hu, S.; Luo, X.; Li, Z.; Sun, X.; Li, M.; Liu, F.; Yu, Y. Confined Amorphous Red Phosphorus in MOF-Derived N-Doped Microporous Carbon as a Superior Anode for Sodium-Ion Battery. Adv. Mater., 2017, 29, 1605820.

(40)

Fuge, G. M.; May, P. W.; Rosser, K. N.; Pearce, S. R. J.; Ashfold, M. N. R. Laser Raman and X-ray photoelectron spectroscopy of phosphorus containing diamond-like carbon films grown by pulsed laser ablation methods. Diam. Relat. Mater., 2004, 13, 1442-1448.

(41)

Claeyssens, F.; Fuge, G. M.; Allan, N. L.; May, P. W.; Ashfold, M. N. Phosphorus carbides: theory and experiment. Dalton T., 2004, 19, 3085.

(42)

Liu, H.; Zou, Y.; Tao, L.; Ma, Z.; Liu, D.; Zhou, P.; Liu, H.; Wang ,S. Sandwiched

Thin-Film

Anode

of

Chemically

Bonded

Black

Phosphorus/Graphene Hybrid for Lithium-Ion Battery. Small, 2017, 13, 1700758. (43)

Song, J.; Yu, Z.; Gordin, M. L.; Hu, S.; Yi, R.; Tang, D.; Walter, T.; Regula, M.; Choi, D.; Li, X. Chemically bonded phosphorus/graphene hybrid as a high performance anode for sodium-ion batteries. Nano Lett., 2014, 14, 6329-6335.

(44)

Sun, C.; Wen, L.; Zeng, J.; Wang, Y.; Sun, Q.; Deng, L.; Zhao, C.; Li, Z. One-pot solventless preparation of PEGylated black phosphorus nanoparticles for photoacoustic imaging and photothermal therapy of cancer. Biomaterials, 2016, 91, 81-89.

(45)

Ni, J.; Fu,S.; Wu, C.; Zhao, Y.; Maier, J.; Yu, Y.; Li, L. Self-Supported Nanotube Arrays of Sulfur-Doped TiO2 Enabling Ultrastable and Robust Sodium Storage. Adv. Mater., 2016, 6, 2259-2265.

(46)

Liu, H.; Tao, L.; Zhang, Y.; Xie, C.; Zhou, P.; Liu, H.; Chen, R.; Wang, S. 24


Page 25 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Bridging Covalently Functionalized Black Phosphorus on Graphene for High Performance Sodium-ion Battery. Acs Appl. Mater. Inter., 2017, 9, 36849-36856. (47)

Zhu, X.; Zhang, T.; Sun, Z.; Chen, H.; Jian, G.; Xiang, C.; Ji, H.; Du, P.; Yang, S. Black Phosphorus Revisited: A Missing Metal-Free Elemental Photocatalyst for Visible Light Hydrogen Evolution. Adv. Mater., 2017, 29, 1605776.

(48)

Kim, Y.; Park, Y.; Choi, A.; Choi, N. S.; Kim, J.; Lee, J.; Ryu, J. H.; Oh, S. M.; Lee, K. T. An amorphous red phosphorus/carbon composite as a promising anode material for sodium ion batteries. Adv. Mater., 2013, 25, 3045-3049.

(49)

Qian, J.; Wu, X.; Cao, Y.; Ai, X.; Yang, H. High capacity and rate capability of amorphous phosphorus for sodium ion batteries. Angew. Chem., 2013, 52, 4633-4636.

(50)

Li, W.; Yang, Z.; Li, M.; Jiang, Y.; Wei, X.; Zhong, X.; Gu, L.; Yu, Y. Amorphous Red Phosphorus Embedded in Highly Ordered Mesoporous Carbon with Superior Lithium and Sodium Storage Capacity. Nano Lett., 2016, 16, 1546-1553.

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Figure 1. Schematic illustration of the fabrication of the NTO/C-BP hybrids.

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Figure 2. SEM images of (a, b) BP nanoparticle, (c, d) NTO/C samples, (e-g) NTO/C-BP hybrids and h-l) corresponding elemental mapping of the NTO/C-BP hybrids showing the Na (blue), Ti (purple), O (green), C (red) and P (yellow) elements uniformly distribute in nanoparticles.

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Figure 3. (a) N2 absorption–desorption isotherms of BP, NTO/C and NTO/C-BP; (b) XRD patterns of BP and NTO/C-BP; (c) Raman and (d) FT-IR spectrum of BP, NTO/C and NTO-BP; Inset of (c) enlarge the picture of P-C bond.

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Figure 4. TEM and HRTEM images of (a, b) BP samples, (c, d) NTO/C samples and (e-f) NTO/C-BP samples; Inset of (a): shows the corresponding SAED pattern of BP.

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Figure 5. (a) Survey XPS spectra of BP, NTO/C and NTO/C-BP; high-resolution P 2p spectrum of (b) BP and (c) NTO-BP.

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Figure 6. High-resolution (a-c) C 1s and (d-f) O1s XPS spectra of NTO/C and NTO/C-BP.

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Figure 7. Eletrochemical measurements of BP, NTO/C and NTO/C-BP. (a) cyclic voltammograms at a scan rate of 0.1mV s-1; the peaks of Ⅰ , Ⅱ and Ⅲ corresponding to the Na+ exaction/insertion from the NTO/C-BP, (b-d) Charge-discharge curves at different cycles at 20 mA g-1.

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Figure 8. Eletrochemical measurements of NTO/C and NTO/C-BP; (a-c) Cycling performance at 20 mA g-1,100 mA g-1 and 200 mA g-1.

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Table of Content


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