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) + + a, at [ 32 ] 32 [ [ 19 ] 19 [ 1 [ 1–4 ] 1–4 [

1401963 F, ion 4 + and How- , Na + [ 22 ] 22 [ , 3 ) [ 27,28 ] 27,28 [ (LTO), 4 Scheme 12 /Na and has LiVPO + (1 of 10) O (PO 5 [ 18 ] 18 [ 2 , 3 Ti Ti ) 4 have been proved 4 www.advenergymat.de ion to diffuse faster + Li (PO NaTi [ 23–25 ] 23–25 [ 2 [ 5 ] 5 [ ,

V 8 3 /C O [ 20,21 ] 20,21 [ As illustrated in in illustrated As 3 , 3 3 [ 9–13 ] 9–13 [ Li V Besides, NVP shows a fl Up to now, many phos- ) 3.4 V versus Na F (NVP) 2 3 ≈ ) ) 4 1.08 ion with respect to that of Na 4 4 In this regard, numerous 2D [ 23–25 ] 23–25 [ + [ 16,17 ] 16,17 [ , [ 14,15 ] 14,15 [ [ 26–28 ] 26–28 [ Achieving breakthroughs in elec- 4 (PO (PO 2 2 , Dongling Ma , , Ma Dongling , [ 29–31 ] 29–31 [ [ 5–8 ] 5–8 [ V V 3 3 Compared with lithium metal oxides, (PO wileyonlinelibrary.com 2 electric vehicles and hybrid electric vehi- cles. Na superionic conductor (NASICON)-related compound, exhibits high ion (Li However, However, their energy density, and cycling life density, urgently need to power be further improved for applications in mobility due to its open framework with trode materials is the key to improve the rate performance, and cycling sta- capacity, bility of LIBs. 1. Introduction 1. Playing an increasingly important role of (LIBs) batteries ion lithium storage, energy are widely used in portable electronics. phosphate cathodes able electrochemical display and bility, which remark- thermal is in sta- stability. favor of the phate cycling cathode LiFePO materials, such as to be promising active materials. Among these materials, NVP, a typical Na Na V 3 ), 1 − DMC || Decreasing the characteristic dimensions of the electrode + , respectively. , respectively. the smaller ionic radius of Li voltage curve with a plateau at ion (0.76 vs 1.06 Å) in principle allows Li nanomaterials including Na large ion transport tunnels. been investigated as one of major prospective cathode materials (SIBs). batteries ion sodium for important factors which need to be further improved before its widespread applications. In addition, the ion insertion/extrac- tion mechanism of NVP in hybrid LIBs also requires more sys- tematic investigations. material is an effective way to improve the rate capability cycling and stability of LIBs. ever, rate capability ever, and cycling performance, considered as two in the NVP, which makes NVP more likely to acquire a higher rate performance in LIBs than in cathode material for SIBs. hybrid LIBs has Recently, been reported. NVP as a 1 − /EC 6 LiPF owers are synthesized M /EC (ethylene carbonate) 6 || 1 12 LiPF O M 5 Ti 4 ion superionic conductor framework, ion superionic conductor 2015 GmbH WILEY-VCH & Verlag KGaA, Co. Weinheim + © , 1401963 2015 owers: Superior Li Storage Performance and . ake-Assembled Hierarchical Na (NVP) has excellent electrochemical stability and fast ion dif- electrochemical stability and fast ion (NVP) has excellent ake-assembled hierarchical NVP/C microfl to the 3D Na cient due 3 ) 4

(PO 2

V 3 DMC (dimethyl carbonate) || NVP and Li DMC (dimethyl carbonate) || NVP and Adv. Energy Mater Adv. www.MaterialsViews.com Varennes , Quebec , J3X 1S2 , Canada Canada , J3X 1S2 , Quebec 1650 Boulevard Lionel-Boulet , Varennes Houston , TX 77204 , USA USA , 77204 TX , Houston [email protected] E-mail: Prof. D. Ma (INRS) que Scientifi Recherche la de National Institut Dr. Q. An, Dr. Y. Yao Yao Y. Q. An, Dr. Dr. of Engineering Cullen College Engineering Department of Electrical and Computer University of Houston Materials Synthesis and Processing WUT-Harvard Joint Nano Key Laboratory P.R. China , University of Technology Wuhan 430070 Wuhan [email protected] E-mail: Dr. Q. An, F. Xiong, Q. Wei, J. Sheng, Dr. L. He, J. Sheng, Dr. Q. An, F. Xiong, Q. Wei, Dr. Prof. L. Mai for State Key Laboratory of Advanced Technology increasing electrode–electrolyte contact area, and shortening the diffusion increasing electrode–electrolyte contact a high capacity (230 mAh g distance. The as-synthesized material exhibits Here, nanofl as-synthesized materials enhances using a facile method. The structure of the electron conductivity, the electrochemical performance by improving which make it an attractive cathode material for lithium ion batteries (LIBs). which make it an attractive cathode material the electrochemical performance of NVP needs to be further However, and hybrid electric vehicles. improved for applications in electric vehicles Microfl Insertion/Extraction Mechanism + the design of hybrid LIBs, and the insertion/extraction mechanism investiga- the design of hybrid LIBs, and the insertion/extraction developing safe and stable, high- tion will have profound implications for and high-power LIBs. energy, The insertion/extraction mechanism of NVP is systematically investigated, The insertion/extraction mechanism of electrochemical performance, based on in situ X-ray diffraction. The superior fusion coeffi Na Yan Yao ,* and Liqiang Mai* Mai* Liqiang and ,* Yao Yan Qinyou An , Fangyu Xiong , Qiulong Wei , Jinzhi Sheng , Liang He Liang , Sheng Jinzhi , Wei Qiulong , Xiong Fangyu , An Qinyou Nanofl cycles), and remarkable rate performance (91 C) in hybrid LIBs. Meanwhile, cycles), and remarkable rate performance || 1 the hybrid LIBs with the structure of NVP excellent cycling stability (83.6% of the initial capacity is retained after 5000 excellent cycling stability (83.6% of the NVP are assembled and display capacities of 79 and 73 mAh g NVP are assembled and display capacities DOI: 10.1002/aenm.201401963 FULL PAPER 1401963 www.advenergymat.de o etan glmrto, hc i fvrbe o ccig sta- cycling for bility. favorable is which agglomeration, restrain ability to better have to believed are nanostructures hierarchical irrhcl V/ microfl NVP/C hierarchical energy. surface caused and area nanomaterials surface high 2D very of their by agglomeration easy the to due challenge big a remains still stability cycling excellent with rial mate- electrode an obtain However,to distance. diffusion ened short- and area contact electrode–electrolyte increased their to due LIBs of performance electrochemical improving for terized 1. Scheme V ion in the crystal structure. b) Schematic illustration of electron/ion transport pathways in the nanofl the in pathways transport electron/ion of illustration Schematic b) structure. crystal the in ion chemical performance of hybrid LIBs. hybrid of performance chemical microfl nanofl that analysis above (Scheme performance rate from 1 high concluded be a can it Therefore, get b). to favorable is which network, transport tronic nanofl on the layer coating uniform thin The problem. this overcome to approach effective an is carbon conductive with NVP Coating conductivity,stability. cycling and electronic performance rate poor the restricts their which is considered be to needs that problem key another electrodes, of phosphate the releasing For strain. the facilitates space inter their and distance sion NVP/C microfl NVP/C 2 O H ri, e fi we Herein, 5 , [ 34–36 ] [ 33 ] (2 of10) owers hold high promise to greatly improve the electro- the improve greatly to promise high hold owers TiO and a with NVP of structure crystal The a) aeasmld microfl ake-assembled A ilsrtd n cee Scheme 1 nanofl in b, illustrated As ower electrode material synthesized via a facile a via synthesized material electrode ower rt eot nanofl a report rst 2 [ 7 ] have recently been synthesized and charac- and synthesized been recently have wileyonlinelibrary.com aeasmld irrhcl NVP/C hierarchical ake-assembled oes oss sot Li short possess owers oes osiue a D elec- 3D a constitutes owers aeasmld hierarchical ake-assembled R3c space group and the schematic illustration of the comparison for diffusion of Li of diffusion for comparison the of illustration schematic the and group space ake-assembled © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimCo.KGaA, Verlag& WILEY-VCH GmbH 2015 + ion diffu- u f f i d n o i [ 30,34,35 ] [ 37–39 ] 3D

structures which are composed of nanofl of composed are which structures fl hierarchical TEM conspicuous The show NVP-750 them. of images between existing spaces open obvious with nanofl neighboring addition, (Figure sample 1 the In in b,c). breakage or collapse structural 750 at annealing fl nanofl stituent of size a with nanofl of composed is in shown As (TEM). microscopy tron elec- transmission and (FESEM) microscopy electron scanning fi by investigated was samples of morphology The 2.1. Analysis FormationMechanism and Morphology 2. Discussion and Results by in situ X-ray diffraction (XRD). X-raydiffraction situ in by investigated systematically was mechanism insertion/extraction ion lithium their Furthermore,stability. cycling and formance, nanofl microfl NVP/C LIBs, hybrid the As for process. electrode annealing by followed method precipitation ower-likestructure is maintained even after high-temperature akes is 20–40 nm. Remarkably, the hierarchical the Remarkably, nm. 20–40 is akes ≈ oes xii hg cpct, xeln rt per- rate excellent capacity, high exhibit owers 1–2 µm in diameter and the thickness of con- of thickness the and diameter in µm 1–2 ° (V-5) n tee s o discernible no is there and (NVP-750) C ake-assembled hierarchical NVP/C microfl NVP/C hierarchical ake-assembled aeasmld fl ake-assembled ae ae osl interconnected loosely are akes aeasmld hierarchical ake-assembled Adv. Energy Mater. Figure oe-ie microsphere ower-like www.MaterialsViews.com akes (Figures (Figures akes 1 and d

1 precursor the a, eld emission eld + Na and ion

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R3c 1401963 owers (3 of 10) -propanol as anti- rming the phase. www.advenergymat.de n No other phases ake-assembled hierarchical [ 37,42,43 ] 37,42,43 [ ake-assembled microfl 10 min. The possible formation rms the high phase purity of ≈ a). All the diffraction peaks can be 2

-propanol decreases the polarity of sol- n wileyonlinelibrary.com Figure -propanol and then gradually grows to form n (the water as solvent and the [ 40,41 ] 40,41 [ The b) Raman displays spectrum of 2 NVP-750 (Figure [ 37 ] 37 [ ower-like ower-like microparticles at the addition of fl mechanism is that the vent and the solubility of solutes, so called antisolvent crystal- lization space group (rhombohedral unit cell), corresponding the well to previously reported literatures. imum (FWHM) of the several main XRD is larger peaks than that of of NVP-750 NVP-650 (Table S1, Supporting Informa- tion). These results indicate that the crystallinity is of lower than NVP-650 that of NVP-750. Some obvious peaks rity of are observed impu- in the XRD pattern of NVP-850 (Figure S5c, Supporting Information) due to overhigh annealing tempera- ture. can be detected, which NVP-750. confi Moreover, the result of inductively coupled (ICP) plasma analysis shows that the molar ratio 1.53:1.00:1.48 of in Na, the V, and NVP-750, P further is confi The intensity of NVP-650 is lower than NVP-750 (Figure S5b, Supporting Information). Besides, the full width at half max- two characteristic bands of carbonaceous materials located solvent), leading to the nucleation. The morphology evolution from irregular particles to nanofl may be due to the Ostwald ripening process, although the exact mechanism is currently under further investigation. Structure Characterization 2.2. The phase purity and crystallinity of the NVP-750 were acterized char- by XRD ( readily indexed to the NASICON structured NVP with a ake- ower ower- ake-assembled owers is shown in 2015 GmbH WILEY-VCH & Verlag KGaA, Co. Weinheim © akes in the NVP-750 sample C. ° C) display a similar morphology, ° somewhat form to fused were akes , 1401963 2015 . owers annealed at 750 . The as-synthesized material was obtained through 2

a) FESEM image of b,c) precursor. FESEM images, d,e) TEM images, and f) EDS elemental mapping of nanofl owers, a series of time dependent experiments were car- C (NVP-850), the nanofl the (NVP-850), C ° The schematic illustration of the fabrication of nanofl -spacing of the (012) planes of rhombohedral NVP, indicating Adv. Energy Mater Adv. www.MaterialsViews.com microfl ried out. The FESEM images (Figure S4, Supporting Informa- tion) reveal that a solid structure is formed immediately after Scheme water bath and annealing treatment, morphology while was generated the during microfl the to water investigate bath. the In formation order process of nanofl homogeneously distributed in NVP-750 (Figure 1 f). 1 homogeneously distributed in NVP-750 (Figure assembled NVP/C hierarchical microfl the crystalline nature of the nanofl e). The carbon 1 layer with a (Figure thickness of 5–10 nm can also be observed. In addition, energy dispersive (EDS) spectrometry element mappings display that Na, V, P, O, and C are The high resolution TEM (HRTEM) image clearly lattice shows fringes the with the space of 6.19 Å, d corresponding to the glucose is in favor of the morphology S1d, maintenance (Figure Supporting Information). This can be attributed to the carbon layer forming from the carbonization preheating, of which glucose is during effective the to restrain the agglomeration. morphology during the forming of precursor can be the However, morphology ignored. of the precursor without glucose has been destroyed after annealing, implying that the existence of a bulk structure (Figures S1 and S3, Supporting Information). The FESEM image of precursor without glucose (Figure Supporting S1c, Information) shows similar like morphology, hierarchical indicating that fl the effect of glucose on the NVP-650 (annealed at 650 but with the annealing temperature being further increased to 850 Figure 1. NVP/C microfl S2, Supporting Information). The FESEM and TEM images of FULL PAPER 1401963 www.advenergymat.de t 39 cm 1339 at 2. Scheme similar result, which may be attributed to the carbonization of carbonization the to attributed be may which result, similar 750 at annealed and glucose any adding without sample the of trum graphitized. partially is carbon deposited 53 cm 1593 pore size distribution (inset), and d) XPS pattern. XPS d) and (inset), distribution size pore Figure 2. (4 of10) Structural characterization of NVP-750: a) XRD pattern, b) Raman spectrum, c) nitrogen adsorption–desorption isotherm and co ° (iue 6 Spotn Ifrain dsly the displays Information) Supporting S6, (Figure C − nanofl of fabrication the of illustration Schematic 1 (rpie -ad, epciey idctn ta the that indicating respectively, G-band), (graphite − 1 (-ad dsre-nue poo md) and mode) phonon disorder-induced (D-band, wileyonlinelibrary.com [ 43,44 ] spec- Raman The © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimCo.KGaA, Verlag& WILEY-VCH GmbH 2015 ake-assembled NVP/C hierarchical microfl hierarchical NVP/C ake-assembled C h sml snhss o cro caig Te oe structure pore The coating. carbon for synthesis sample during the glucose of importance the H, suggests C, strongly It of N. analysis and elemental the on based respectively, 0.1%, 750 at annealing glucose adding without sample the and NVP-850, NVP-750, NVP-650, of tents 2 O 4 2 − ain drn anaig I adto, h cro con- carbon the addition, In annealing. during anions owers. ° C are 5.2%, 4.8%, 2.9%, and 2.9%, 4.8%, 5.2%, are C Adv. Energy Mater. www.MaterialsViews.com

2015 rresponding , 1401963 FULL PAPER 1401963 A f t e r , w h i c h 1 − rate perfor- ) a n d N V P - [ 5,50,51 ] 5,50,51 [ 1 ce of NVP-650, − (5 of 10) i o n i n s e r t i o n + , c o r r e s p o n d i n g 1 − www.advenergymat.de ciency of NVP-750 is close to is close of NVP-750 ciency wileyonlinelibrary.com /Li): a) CV curves of NVP-750 at a scan rate of rst 15 cycles, while capacity of NVP-650 of NVP-650 capacity while rst 15 cycles, + ), respectively. Note that the cycling stability 1 − ) charge/discharge cycles (Figure 3 b) show that the 1 − cient by enhancing the crystallization, but the overhigh tem- overhigh the but crystallization, the enhancing by cient performance performance of NVP The annealed results of at low different 110 mA current g temperatures. density (0.91 C, 1 C refers to initial discharge capacity of NVP-750 is 230 mAh is g close to the capacity corresponding to 4 Li 50 cycles, the discharge and NVP-850 capacities are 105, of 209, and NVP-650, 25 mAh NVP-750, g 850 (121 mAh g that the charge transfer resistance (Rct) of NVP-750 is lower than those much of NVP-650 and NVP-850. This is on account of that the increased annealing temperature can increase the electronic conductivity of carbon and the ionic diffusion coef- fi perature annealing leads to agglomeration which is adverse for the electronic conduction and ion diffusion. Besides, the exist- ence of impurity in NVP-850 is another reason for the poor to 47.1%, 90.9%, and 20.7% of their initial capacities, respec- indicating that NVP-750 exhibits tively, better long-term perfor- mance. And the Coulombic effi 100%. Moreover, two voltage plateaus of NVP-750 are clearly observed from the charge/discharge curves, which are longer than those of other two the samples c). Nyquist plot 3 (Figure Furthermore, (Figure S8, Supporting Information) shows and higher than those of NVP-650 (223 mAh g and reversible capacity of similar NVP-650 during the and fi NVP-750 are drop after very 20 cycles. This is attributed to the low of NVP-650, crystallinity which leads to poor stability of crystal, especially during a great quantity of ions (four ions per formula) tion/extraction inser- resulting in a large expansion.

i n o u r s a m p l e , + [ 44–47 ] 44–47 [ 2 / L i t o o b t a i n h i g h / V + + 3 Cyclic voltammetry (CV) 2015 GmbH WILEY-VCH & Verlag KGaA, Co. Weinheim © a n d V [ 48 ] 48 [ + 3 , was observed. / V + Halenda Halenda pore-size distribution + 3 4 − Joyner − , 1401963 , which is much larger than that of NVP-850 1 a) show two pairs of oxidation and reduction − 3

Galvanostatic discharge/charge measurements 2015 g . 2 ) (Figure S7, Supporting Information). This result [ 49 ] 49 [ 1 − ; b) cycling performance and c) charge/discharge curves of NVP-650, NVP-750, and NVP-850 at the current density of 0.91 C; d) g 1 Figure The electrochemical performance of NVP in the potential range from 1.0 to 4.3 V (vs Li 2 − Adv. Energy Mater Adv. www.MaterialsViews.com Figure 3. mance of NVP-650, NVP-750, and NVP-850, and e) corresponding charge/discharge curves of NVP-750; f) high-rate cycling performan NVP-750, and NVP-850. 0.1 mV s peaks, at about 3.90/3.60 and 1.83/1.66 V, which are close the equilibrium voltages to of V were carried out in order to compare the electrochemical window between 1.0 and 4.3 V versus Li In orderNVP, the coin cells with metallic lithium as anode were assem- bled. First, NVP electrodes to were measured in a wide voltage investigate the electrochemical performance of 2.3. Electrochemical Performance 2.3. respectively. respectively. (12.8 m 750 are mainly below photoelectron 20 spectrum nm. The X-ray d) was (XPS) 2 utilized (Figure to probe the oxidation state of vanadium in NVP-750. A peak located at the binding energy of corresponding to V 517.01 eV, agglomeration occurs, which results in the surface. decrease of The BET Barret c) curve displays (inset that 2 of the Figure pore sizes in NVP- indicates that when annealing temperature is too high, sample curves ( Emmerr–Teller Emmerr–Teller (BET) surface area of to be NVP-750 30.7 m is estimated and surface area of NVP-750 were investigated by nitrogen iso- c). The isotherm can be 2 thermal–adsorption technique (Figure described as type II with a H3 hysteresis loop. The Brurauer– naceous materials is below 1.0 V. capacity. capacity. The reversible capacity of carbon in the composite is negligible due to the fact that the discharge voltage of carbo- FULL PAPER 1401963 www.advenergymat.de lent rate performance. A high discharge capacity (143 mAh g mAh (143 capacity discharge high A performance. rate lent excel- displays also NVP-750 performance. electrochemical the improving for necessary is coating carbon suitable that cating respectively,indi- distance, electronic diffusion ion long and poor conductivity in results which agglomeration, the and tent con- carbon low the to attributed be can glucose with sample 0 yls t h lw urn dniy f .1 (iue 4 (Figure b). C 0.91 of density current low the at cycles 50 retained at 150 and 138 mAh g mAh 138 and 150 at are retained capacities their Remarkably, respectively. C, 45 and 27 of low with g cycles mAh 50 (88 capacity after initial performance of (22.6%) retention low a shows result The Information). Supporting S9, (Figure condi- investigated also was same glucose of lack the with NVP-750 as tions the under prepared electrochemical sample the the of performance Further, performance. electrochemical h iiil aaiis f V-5 (3 A g mAh (43 NVP-650 of capacities initial The 1.0–4.3 V. NVP-750 electrode delivers the initial capacity capacity initial the g delivers mAh 103 electrode of NVP-750 at V. measured curves 1.0–4.3 CV the in observed those cor- to essentially V,responding 3.85/3.66 about potential at appear peaks NVP-750 of curves CV voltage The ( V. a 4.3 at and 2.5 investigated between been window has cathode potential high a samples. three the among NVP-750 of performance ical confi analyses electrochemical above g mAh (32 spe- initial Figure cifi 3 The in f. shown is density at current NVP-750 high of stability cycling the addition, g (Figure 3 In mAh d). (64 NVP-650 than higher of is that which C, 36 at even retained was NVP-750 of b) cycling performance, and c) charge/discharge curves at the current density of 0.91 C; d) rate performance and e) high-rate c high-rate e) and performance rate d) C; 0.91 of density current the at curves charge/discharge c) and performance, cycling b) Figure 4. Figure Figure cdischarge capacities are 164 and 130 mAh g Furthermore, the electrochemical performance of NVP as as NVP of performance electrochemical the Furthermore, (6 of10)

The electrochemical performance of NVP-750 in the potential range from 2.5 to 4.3 V (vs Li (vs V 4.3 to 2.5 from range potential the in NVP-750 of performance electrochemical The 4 a) show that one couple of oxidation and reduction reduction and oxidation of couple one that show a) − 1 ) at 27 C are lower than that of NVP-750. These e s e h T . 0 5 7 - P V N f o t a h t n a h t r e w o l e r a C 7 2 t a ) − 1 and exhibits no evident capacity loss after after loss capacity evident no exhibits and wileyonlinelibrary.com − 1 ). The low initial capacity of the e h t f o y t i c a p a c l a i t i n i w o l e h T . ) − 1 − ) and NVP-850 (23 mAh g g h A m 3 2 ( 0 5 8 - P V N d n a ) 1 after 200 cycles, respectively. . y l e v i t c e p s e r , s e l c y c 0 0 2 r e t f a rm the rmbest electrochem- − 1 ) and NVP-850 0 5 8 - P V N d n a ) − © 1 at the rates s e t a r e h t t a 2015 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimCo.KGaA, Verlag& WILEY-VCH GmbH 2015 − − 1 1 ) ) charge curves (Figure 4 c). NVP-750 displays excellent rate rate g mAh excellent 43 of capacity discharge a displays and performance NVP-750 4 (Figure c). curves charge confi be also can voltage stable The and reduction peaks (1.83/1.73 V) of V of V) (1.83/1.73 peaks reduction and measure- by investigated voltagewindowaV. between2.5mentsinand been 1.0 oxidation The also has LIBs hybrid for anode nanofl between space the by vided pro- cycles discharge and charge during insertion/extraction low current of 0.91 C, its initial capacity is 99 mAh g mAh 99 is capacity initial its C, 0.91 of current low ( curves CV their from observed clearly at 9.1 C. The initial capacity of 86 mAh g mAh 86 of capacity initial The C. 9.1 at stability excellent exhibits also NVP-750 layer. carbon of work nanofl of diffusion distance ionic short the to ascribed be can excellent performance The rate Information). Supporting S10, (Figure potential plateau high the only or plateaus two using whether mance perfor- rate better the exhibits NVP-750 results, reported the (Figure C to 4 91 of Compared rate d). high a at even retained rhcl tutr ad h bfeig o te tes f Li of stress the for buffering the and structure archical f 7 A g mAh 77 of capacity initial (FigureThe 5 C. C NVP- 9.1 at 91 stability excellentd). exhibits also of 750 rate high a at even obtained be can 7000 cycles (Figure cycles 7000 5 e). reported (capacity retention is 97.4% over the following following the over 97.4% is been cycles). 97 retention has one best (capacity the than reported better much is stability (Figure 4 cycles cycling The 5000 e). after retained is it of 83.6% and et ae efrac wt a icag cpct o 7 mh g mAh 72 of capacity discharge a with performance rate lent excel- displays electrode (Figure 5 NVP-750 100% b). to closing sponding to capacity retention of 99.0% with Coulombic effi aaiy f 8 A g mAh 98 of capacity as NVP-750 of performance electrochemical the Meanwhile, [ 27 ] This can be attributed to the stability of 3D hier- r e i h D 3 f o y t i l i b a t s e h t o t d e t u b i r t t a e b n a c s i h T − 1 hs en band n 9.% s eand after retained is 97.5% and obtained been has ae ad h fs electronic fast the and akes transport net- − + 1 /Li): a) CV curve at a scan rate of 0.1 mV s mV 0.1 of rate scan a at curve CV a) /Li): can be retained after 50 cycles, corre- e r r o c , s e l c y c 0 5 r e t f a d e n i a t e r e b n a c akes. akes. re i te charge/dis- the in rmed 3 Adv. Energy Mater. + Figure /V V / www.MaterialsViews.com − 2 + 1 ycling performance. ycling beNVP-750 canin has been obtained obtained been has

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2015 − − 1 1 still was the and , 1401963 ciency + ion − − 1 1 ;

FULL PAPER ; - 1 − 1401963 NVP ʈ ic hybrid DMC + (7 of 10) ion are benefi /EC + 6 cling performance of www.advenergymat.de L i P F M akes provides a buffer a buffer provides akes 1 ʈ ion insertion/extraction during + /Li): a) CV curve at a scan rate of 0.1 mV s + wileyonlinelibrary.com in the voltage range of 1–3 V. akes. akes. 1 − The excellent electrochemical performance of NVP/C micro- owers can be ascribed to the advantages of their ionic proper- fl channels insertion large The (a) structure. favorable the and ties of NASICON structure and the small size of Li charge and discharge. (c) The electronic established conduction by carbon network layer ensures the fast electron transport between NVP nanofl cial to the ionic transport. (b) The nanostructure possesses the large electrode–electrolyte contact area and short ion diffusion distance, and the space between nanofl for the stress associated with Li

− LTO) measured at 100 mA LTO) g − with a 1 − NVP (NVP ʈ NVP (NVP ʈ DMC (dimethyl NVP and NVP + − DMC + DMC + /EC /EC 6 2015 GmbH WILEY-VCH & Verlag KGaA, Co. Weinheim 6 © LiPF LiPF M M 1 ʈ 1

ʈ NVP) was assembled. The scheme a. In addition, an asymmetric hybrid 12 − 6

O 5 Ti 4 /EC (ethylene carbonate) 6 , 1401963 Figure can be obtained from NVP 1 2015 − . LiPF NVP (NVP M ʈ 1 ʈ a) Schematic Illustration of the structure and mechanism of the symmetric hybrid LIBs with a structure of NVP of structure a with LIBs hybrid symmetric the of mechanism and structure the of Illustration Schematic a) The electrochemical performance of NVP-750 in the potential range from 1.0 to 2.5 V (vs Li NVP) and b) the cycling performance and the corresponding potential-times curves (inset) of symmetric hybrid LIBs and asymmetr − Taking advantage of the large voltage difference between the LTO) was assembled. When measure at 100 mA g Adv. Energy Mater Adv. www.MaterialsViews.com Figure 6. Figure (NVP LIBs with structure as Li LTO, respectively (Figure 6 b). 6 respectively (Figure LTO, of the structure and the mechanism of the symmetric LIB are shown hybrid in − two plateaus of NVP, a symmetric hybrid LIB with a structure of NVP Figure 5. potential range of 1.0–3.0 the V, initial discharge capacity of 79 and 73 mAh g carbonate) LIB with structure as LTO b) cycling performance and c) charge/discharge curves at the current density of 0.91 C; d) rate performance and e) high-rate cy NVP-750. FULL PAPER 1401963 www.advenergymat.de Li identifi be can peaks the all V, 2.5 to discharging Upon Li of peaks with Li from transition phase the is 7 (Figure b) plateau at tion con- reac- the be that indicating phases, can two of coexistence process as sidered This weaken. NVP from arising peaks be can peaks the all identifi process, charging the of during beginning LIBs the hybrid for electrode fi as the NVP of changes tural o . V te hs o Li of phase the V, 1.0 to of plateau the coexistence at occur not the does phases two indicating process, peaks or this appear during peaks disappear new no However, insertion. ions the the that indicating angles, smaller shift to (211) and (024), (113), (104), (012), as such peaks main NaV 1 and NVP the between place takes ion-exchange h cpct (3 mh g mAh (230 capacity the s lcrd fr yrd Is ( LIBs hybrid NVP for the electrode of as mechanism insertion/extraction the investigate to utilized been has technique XRD situ in the Furthermore, 2.4. Mechanism Insertion/Extraction vious reported literature. reported vious peaks new some NaV charging, of continuous With observed. edly h itniis f ata pas rm NaV from peaks partial of intensities the erature previously reported, except for the peaks from binder binder (poly(tetrafl from peaks the for except reported, previously erature can be indexed to NaV to indexed be can Li of phase where the Information), Supporting S11, (Figure h 12 for trolyte 1 in soaked NVP-750 of pattern XRD analysis. confi ICP be can of reaction ion-exchange result the Moreover, the by supported also was which cell, EC recorded from 13 from recorded shift back to their original positions suggesting the reversible the suggesting positions original their to back shift V,2.5 to back recharging after addition, In insertion. peaksthe Li to back curves. 7. Figure 2 NaV V a N + 2 rt yl bten . ad . V t lw urn. At current. low a at V 4.3 and 1.0 between cycle rst DMC electrolyte during the standing of the assembled assembled the of standing the during electrolyte DMC (PO O P ( (8 of10) e a Li as ed 2 a) In situ XRD patterns of NVP-750/Li cell during the charge/discharge in a voltage range of 1.0–4.3 V and b) corresponding b) and V 1.0–4.3 of range voltage a in charge/discharge the during cell NVP-750/Li of patterns XRD situ In a) 2 (PO O P ( (PO O P ( 4 ) ) 3 uoroethylene) (PTFE)). . At the end of charging (4.3 V), the XRD pattern pattern XRD the V), (4.3 charging of end the At . 2 4 4 NaV V a N ) ) ) ) 3 3 , confi n o c , appear and gradually strengthen while the the while strengthen gradually and appear a 2 2 2 NaV V a N NaV V a N of the corresponding potential-time curves curves potential-time corresponding the of (PO O P ( ° 2 NaV V a N to 35 rming the phase completely transforms transforms completely phase the rming 2 2 4 (PO O P ( (PO O P ( ) ) 2 2 3 wileyonlinelibrary.com (PO O P ( (PO O P ( . With further discharging, several several discharging, further With . ° [ 42 ] 4 , a range that can well refl well can that range a , − NaV V a N 4 4 1 ) ) ) ) At the beginning of the discharge, discharge, the of beginning the At ) which corresponds to 4 Li i L 4 o t s d n o p s e r r o c h c i h w ) 4 3 3 4 ) ) , corresponding well to the lit- t i l e h t o t l l e w g n i d n o p s e r r o c , , instead of NVP, was undoubt- t b u o d n u s a w , P V N f o d a e t s n i , ) ) 3 3 appearing and strengthening. strengthening. and appearing , corresponding well to the pre- e r p e h t o t l l e w g n i d n o p s e r r o c , 2 (PO O P ( Figure [ 26 ] 4 ) ) 3 This result indicates that that indicates result This M can be concluded from from concluded be can d

-space increases during during increases -space LiPF F P i L 7 2 e h T . ) a b . After discharging discharging After . 6 /EC C E / 2 (PO O P ( 2 NaV V a N © rmed by the the by rmed + 4 2015 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimCo.KGaA, Verlag& WILEY-VCH GmbH 2015 ) ) DMC elec- θ 3 2 ectstruc- decrease decrease ( (PO O P ( M ° LiPF F P i L ) were were ) ed as as ed 4 + ) ) ion 3 to to 6 /

anism of NVP as electrode for hybrid LIBs can be described described be can follows: LIBs as hybrid for electrode as NVP of anism NaH hs tasomto bc t Li to back transformation phase 4. Section Experimental for properties remarkable cycling stability. A high capacity of 230 mAh g promising exhibits and performance, capacity,rate high excellent with LIBs hybrid NVP-750 The fl o method. n a n microfl e h T 3. Conclusions materials. electrode of properties electrochemical and physical the mize provides opti- to which barrier kinetic XRD, the tailoring situ for information in invaluable by investigated been has LIBs microfl NVP/C hierarchical bled nanofl of mechanism insertion/extraction the more, Further-LIBs. high-power and high-energy stable, and safe for microfl NVP/C nanofl stability.Hence, cycling term long- the and density power for high with LIBs attractive hybrid of development is which C, 9.1 at cycles 5000 after retained above analysis, the possible Li possible the analysis, above

e hre/icagd t ih ae o 9 C ih capacity a g with mAh C 43 91 of of rates high can at it charged/discharged i.e., be outstanding: are high properties the LIBs, charge/discharge hybrid rate for cathode potential high the As sity. signifi is V,4.3 to 1.0 from range voltage a in C 0.91 at obtained be which Paeub iNV(O)2i2 iNV(O) (PO NaV Li 2e 2e 2Li 2Li 2Na ) (PO ) ) NaV (PO (PO NaV NaV Li b) Li (Plateau ) (PO NaV 2Li Li a) (Plateau ) (PO V Na (Standing) ytei ad hscceia Characterization: Physicochemical and Synthesis 2 PO oes ae en successfully been have facile owers synthesized a by 4 cant for the applications in LIBs with high energy den- ·2H 2 aeasmld irrhcl V/ (NVP-750) NVP/C hierarchical ake-assembled O ad lcs, f nltcl rd, ee l purchased all were grade, analytical of glucose, and O, 232432243 234243 2243 − 24 43 2 2 43 32 1 oe wud e promising a cathode material would be ower . Besides, 83.6% of the initial capacity can be e b n a c y t i c a p a c l a i t i n i e h t f o % 6 . 3 8 , s e d i s e B . + +→ ↔++ ++↔ ++ + +− ion insertion/extraction mech- h c e m n o i t c a r t x e / n o i t r e s n i n o i oes s electrode owers as hybrid in 2 NaV V a N ake-assembledhierarchical Adv. Energy Mater. 2 (PO O P ( www.MaterialsViews.com V 4 ) ) +− 2 3 O . Based on the the on Based . 5 H , potential-time ake-assem-

2 2015

C 2 O

, 1401963 4 ·2H − 1 can n a c 2 (1) (3) (2) O,

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, , , , , , , 6 7 22 , , Adv. Adv. Adv. Adv. 162 414 344 Nat. Nat. , 1401963 2006 Shen , Shen , , Chem.

, 2013 2011

2012 2001

Nano Lett. Adv. Adv. Funct. 2014

2001

Science

, 3575 . . 3575 , Energy Environ. Energy Environ. (9 of 10) J. Power Sources 23 , Nat. Nanotechnol. Science J. Electrochem. Soc. ACS Nano , 68 . . 68 , 9 www.advenergymat.de 2011 ,

, 1596 . . 1596 , , 20857 . . 20857 , J. Mater. Chem. 13 2010 , 1 . . 1 , Nat. Nanotechnol.

, , 939 . . 939 , 22 , 15 , Nature (London) J. Solid State Chem. 195 2013 , , 14357 . . 14357 ,

Adv. Mater. Adv. 2012

2013 15

, 4842 . . 4842 , , 5794 . . 5794 , , 2010 , A536 . . A536 ,

Nat. Mater. 22 26 , , 2949 . . 2949 , , 157 2013

, 11 Nano Lett. , , 929 . . 929 , 2010 2014 , 444 . . 444 ,

3 wileyonlinelibrary.com 23 2010

, , 2011

J. Mater. Chem. J. Mater. Solid State Sci. , 1223 . . 1223 , , 4265 . . 4265 , , 19 . . 19 , , 366 . . 366 , 2013 2013

4 11 24 24 J. Power Sources

, , , , , 6173 . . 6173 , . 2854 , 5 4 Adv. Mater. Adv. Adv. Mater. Adv. , 284 . . 284 , , A1067 . . A1067 , , , , 1042 . . 1042 , , 309 . . 309 , 2005 2012 2012 2014 Nano Lett.

158 7 223 14 , , , , 2012 2011 , 977 . . 977 ,

H. Li , W. Chen , D. F. Chen , Y. C. Ikuhara , L. Q. Chen , Chen L. Q. , Ikuhara Y. C. , Chen D. F. , Chen Energy Mater. W. , Li H. Mater. 277 . . 277 Mater. A. K. Rai , J. Kim , Kim 2011 J. , Rai A. K. H. J. Fan , Fan H. J. 311 Sci. , Viswanathan Sci. V. V. , Xia G. , , Schwenzer Xiao B. J. , , Shao Wang Y. C. Y. M. , , 2012 Li Hu X. J. L. , Z. , Sprenkle Li V. L. Y. , Baskaran S. Mater. Funct. , Cui Y. 2013 Phys. Chem. Chem. Phys. 176 . . 176 4459 . . 4459 , Ajayan J. Electrochem. Soc. P. M. , Vajtai R. , Grey C. , P. Chupas P. , J. Chapman K. W. . 1252817 , Zhang , Q. Z. , Sun Minhas-Khan K. Y. A. , Xu L. , Hercule K. M. 2014 , Kang K. , Lee S. , Mater. Gwon H. , Kim S.-W. . 20535 359 . . 359 , Tarascon Mater. J. M. , Armand M. , Cui Y. , Hu L. B. , Yang Y. , Jackson A. , Lee S. W. [1] J. M. Tarascon , M. Armand , , J. Armand M. Tarascon M. [1] [4] K. Kang , Y. S. Meng , J. Bréger , C. P. Grey , G. Ceder , Ceder , G. , Tang Grey A. D. C. P. , , Wang Bréger J. J. W. , , , Chen Meng Ren C. H. Y. S. , , Y. Feng , Kang Liu K. X. Y. , S. Q. [4] Sun , Wang Y. , H. Y. Li , , [5] Müllen S. R. Graff , K. G. L. Wang , , S. Feng Q. Imhoff X. L. [6] C. , , Lemmon Yang J. S. P. B. , [7] Yang Z. G. , Zhang J. G. , Liu J. [9] [2] P. G. Bruce , S. A. Freunberger , L. J. Hardwick , J. M. Tarascon , Tarascon J. M. , Hardwick , L. J. Walker , W. Freunberger , S. Delacourt A. , C. , Bruce Dupont P. G. L. , [2] Chotard J. , N. Recham N. [3] , McDowell M. , T. Yao Y. , Ryu I. , Choi J. , W. Chan G. , Wu H. [8] [11] J. W. Fergus , Fergus J. W. [11] [12] D. Chao , X. Xia , J. Liu , Z. Fan , C. F. Ng , J. Lin , H. Zhang , Z. X. Z. X. , Zhang H. , Lin J. , Ng C. F. , Fan Z. , Liu J. , Xia X. , Chao D. [12] [10] Y. Yao , M. T. McDowell , I. Ryu , H. Wu , N. Liu , L. B. Hu , W. D. Nix , Nix D. W. , Hu L. B. , Liu N. , Wu H. , Ryu I. , McDowell M. T. , Yao Y. [10] [13] C. He , S. Wu , N. Zhao , C. Shi , E. Liu , J. Li , Li J. , Liu E. , Shi , C. , Yamakia Zhao J. N. , , , Okada Wu Ma S. S. L. , L. , , Noguchi He Hashim D. Y. C. P. , , Zhan Kobayashi [13] L. E. , , Liu Plashnitsa , Z. L. S. , Scrosati [14] Gong B. Y. J. , , Amine Yang S. K. B , , [15] K. , , Wiaderek Oh O. , M. Borkiewicz Zhao K. F. , H. J. Strobridge Y. , L. C. Liu , H. Oh Chen S. M. [16] S. , Y. , Myung Mai L. S. T. Q. , , Chen Oh D. D. , S. W. An [17] Q. Y. , , Wei Croguennec L. Q. , [18] Suard E. , Masquelier C. , AtebaMba J. M. [19] , Liu S. , Song W. [21] [24] K. Saravanan , C. W. Mason , A. Rudola , K. H. Wong , P. Balaya , , Balaya Hu P. S. Y. , , Wong Xi K. X. H. K. , , Gu Rudola L. A. , , Lu Mason X. C. W. , , Han Saravanan W. Z. K. , Yuan [24] C. C. , Jian Z. L. [25] [30] S. Arico , P. Bruce , B. Scrosati , J. M. Tarascon , W. Schalkwijk , Schalkwijk W. , Tarascon J. M. , Scrosati B. , Bruce P. , Arico S. [30] [23] J. Kang , S. Baek , V. Mathew , J. Gim , J. Song , H. Park , E. Chae , Chae E. , Park H. , Song J. , Gim J. , Mathew V. , Baek S. , Kang J. [23] [22] S. I. Park , I. Gocheva , S. Okada , J.-i. Yamaki , Yamaki J.-i. , Okada S. , Gocheva I. , Park S. I. [22] [27] K. Du , H. W. Guo , G. R. Hu , Z. D. Peng , Y. B. Cao , Cao B. Y. , , Banks Peng C. E. Z. D. , , Chen Hu Q. Y. G. R. , , Zhu Guo R. Y. H. W. , , Pan Du C. C. , K. Ji [27] X. B. , Song , Braun X. W. P. V. , [28] Yu X. D. , Zhang H. G. [29] [20] R. A. Shakoor , D.-H. Seo , H. Kim , Y.-U. Park , J. Kim , , , Kim J. , Park Y.-U. , Kim H. R. , Seo D.-H. Shakoor A. [20] [26] B. L. Cushing , J. B. Goodenough , Goodenough J. B. , Cushing B. L. [26] C ° ake- O (0.94 g) and 2 O (0.76 g) were 2 Published online: Published online: ·2H 4 ·2H 4 X-ray source. FESEM owers were obtained PO O α C for 4 h followed by 2 2 ° C 2 Revised: December 21, 2014 Revised: Received: November 4, 2014 Received:

2015 GmbH WILEY-VCH & Verlag KGaA, Co. Weinheim owers, 30% acetylene black © ower-like precursor. In the end, The electrochemical properties dissolved in EC/DMC with a volume 6 -propanol (50 mL) was added into the n L i P F (0.36 g) and H M 5 solution. Then NaH O 4 2 O 2 ake-assembled fl , 1401963 C for 8 h in argon atmosphere with a heating rate of ° 2015 . . A series of experiments with different annealing temperatures annealing different with experiments of series A . 1 − C to get nanofl ° ake-assembled hierarchical NVP/C microfl Electrochemical Characterization: C min C /Li with a multichannel battery testing system (LAND CT2001A). + ° Adv. Energy Mater Adv. www.MaterialsViews.com nanofl from the precursor by preheating annealing at 750 it at 400 5 Li ratio of 1:1. Cathode electrodes assembled were obtained hierarchical with 60% NVP/C and nanofl 10% microfl PTFE. Galvanostatic charge/discharge investigated cycling in behavior a was potential range of 1.0–4.3/2.5–4.3/1.0–2.5 V versus from the Sinopharm Chemical Reagent For a typical Co., synthesis, V Ltd. (Shanghai, China). were characterized by assembling 2016 coin cells in with a glove lled pure box fi argon gas, electrolyte is composed of 1 which used lithium pellet as the anode. The measurement was performed using a VG Multi EL cube The carbon content analyses were performed by Elementar Vario Lab 2000 instrument. elemental analyzer. ICP test were 4300DV performed spectrometer. by PerkinElmer Optima images were collected with a JEOL-7100F microscope at an acceleration voltage of 10 kV. TEM and HRTEM images JEM-2100F were STEM/EDS recorded microscope. by BET using surface a areas were II measured using 3020 a instrument Tristar by adsorption of nitrogen at 77 K. XPS dissolved into deionized water (20 mL) and vigorously stirred at 70 for 1 h to obtain a VOC Prof. C. M. Lieber of Harvard Prof. University, Dongyuan Zhao of Fudan University, and Dr. Jun c Liu Northwest of National Pacifi Laboratory for strong support and stimulating discussion. Key Laboratory of Advanced Technology (2013-KF-9, 2014-KF-4 Processing University and (Wuhan of Technology) for Materials Synthesis and 2013-ZD-7), and the Students Innovation and Entrepreneurship Training Programs (20141049701006 and 20141049701027). The authors thank the International Cooperation Program Science of and China Technology (2013DFA50840), the Hubei Central the for Science Funds Research Fundamental the (2014CFA035), Scholars Fund for Distinguished Universities Young (WUT:2014-YB-001 and WUT:2014-CL-B1-12), the State competing fi nancial competing interest. fi This work was supported by the National Basic Research Program of China (2013CB934103 and 2012CB933003), the National Natural Science National Foundation Science Fund of for China Distinguished Young (51272197), Scholars (51425204), the Acknowledgements Q.A. and F.X. contributed equally to this work. the All authors results discussed and commented on the paper. The authors declare no from the author. from the author. Supporting Information Supporting Information is available from the Wiley Online Library or CV and AC-impedance spectra were acquired 302 with and CHI workstation 760D). (Autolab PGSTAT an electrochemical glucose (0.2 g) were added into the solution, which was further stirred for stirring 5 min. After that, solution stirring was continued for more than 10 min, followed by drying at 70 and without glucose were carried out in synthesis order recipe. to XRD and identify in the situ optimal XRD measurements were performed to investigate the crystallographic structure using a D8 diffractometer Advance with a X-ray nonmonochromated Cu K FULL PAPER 1401963 www.advenergymat.de 3] [35] Q. A. [34] Pan , Y. G. B. H. Guo Wu , , S. J. L. Hu Yu [33] , J. L. , Y.Q. T. Wan An , Zhu , , L. Q. [32] W.X. Wei S. , Lou Chen Q. L. , , Mai Y. L. , Y.J. Xin , Fei Y. Y. , X. Zhou Xu , Y., R. Y. L. Ma Zhao , , H. H. Y.M. Zhou Yan, M. L. Qi , 4] [40] D. Duffy , [39] M. W.Barrett C. , Duan B. , Glennon Q. [38] Z. , Zhu K. , Saravanan H. , W. C. Li [37] , Mason B. C. Z. , Zhu A. Hu , , P. Rudola K. [36] K. , Song H. K. H. Zhang , A. P. Wong , Liu Y. Aken F. , , P. , Y. Cheng J. Balaya , Wang Maier , J. , , Chen H. Y. , Li Yu , , W. Yang , H. Zhou , 4] [41] H. Qin , X. M. Zha , Y. Z. Ma , Q. F. Zhao , Y. S. Xu , X. H. Xu , [31] G. P. Bruce , B. Scrosati , M. J. Tarascon , lants Explos. Pyrotech. Explos. lants faces 16828 . F. P. Zhang Z. , S. Huang , Sci. Environ. 47 J. Mater.A J. Chem. Mater.Energy 14 3273 . (10 of10) , 2175 . , 2930 .

2012 , 4

, 3874 . 2014

2013

, 2014 7 , , 1924 . 3

, 444 . 2014 wileyonlinelibrary.com , 2 , 8668 . , 39 Adv.Mater. hs Ce. hm Phys. Chem. Chem. Phys. , 694 . Cryst. Growth Des. Cryst.Growth Angew. Chem. Int. Ed. Int. Angew.Chem.

2008 ChemPhysChem ACS Appl. Mater.Appl. ACS Inter- , 20 , 2878 . Nano Lett. Nano

2013 © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimCo.KGaA, Verlag& WILEY-VCH GmbH 2015

,

2013 13 2010 , 3321 . Propel- Energy

2008 2014 , , , Adv. 15 11 , , , , , 5] [50] Y.H. Wang , [49] L. K. L. Z. Huang , Jian Y. , L. [48] Ren Zhao , M. , B. X. Endo L. H. , Huang C. Pan , , Kim Q. S. Y.S. , K. Liu Hu Nishimura , , , W. J. T.H. WangFujino Li , , , K. W. Miyashita , Chen , Q. L. Chen , 4] [47] M. M. Ren , Z. [46] V.Zhou M. , Reddy Y. Z. , V.S. G. [45] Li , Rao C. J. P. X. , Zheng V.R. B. , Gao H. X. Chowdari , [44] , Li J. Z. , Y. X. YanZ. Li , Wang, Z. , [43] Zhou J. H. , L. P. Guo X. X. Gao , Wu Y. Q. , , Y.J. L. Hu Yan Jiang , , , W.J. F. F. [42] Peng Cao L. , , Z. Jian G. Y. , Z. Guo W. Han , J. L. , X. Wan Lu , X. , H. Yang , S. Y. Hu , Jing Zhou , 5] [51] Y. H. Wang , J. W. Wang , Y. Ren , L. K. Huang , Q. S. Liu , Sources Sources Power J. Commun. Electrochem. 2000 162 195 Sources Power J. 633 . 2009 Mater. B. Z. Zhou , Q. J. Li , W. Chen , F. D. Chen , Q. L. Chen , , 1357 . , 5768 . , , 38 21

2013

2012 , 2710 . , 183 . , , 3 199 , 156 .

2011 2009 , 263 . , , 196 189

2012 , 9786 . , 476 . , 14 , 86 . . oe Sources Power J. Adv. Energy Mater. www.MaterialsViews.com J. Power Sources Power J. J. Power Sources Power J.

2015

d. Mater. Adv. Adv. Energy Adv. 2006 , 1401963 . Power J. Carbon

, 2006 2010 160 , , ,

Copyright WILEY‐VCH Verlag GmbH & Co. KGaA, 69469 Weinheim, Germany, 2015.

Supporting Information

for Adv. Energy Mater., DOI: 10.1002/aenm.201401963

Nanoflake-Assembled Hierarchical Na3V2(PO4)3/C Microflowers: Superior Li Storage Performance and Insertion/Extraction Mechanism

Qinyou An, Fangyu Xiong, Qiulong Wei, Jinzhi Sheng, Liang He, Dongling Ma, Yan Yao,* and Liqiang Mai*

Supporting Information

Nanoflake-assembled Hierarchical Na3V2(PO4)3/C Microflowers: Superior Li Storage Performance and Insertion/Extraction Mechanism

Qinyou An‡, Fangyu Xiong‡, Qiulong Wei, Jinzhi Sheng, Liang He, Dongling Ma, Yan Yao* and Liqiang Mai*

Figure S1. The FESEM images of (a) NVP-650, (b) NVP-850, (c) precursor without glucose and (d) sample without glucose after annealing at 750 oC.

1

Figure S2. The TEM image of NVP-750.

Figure S3. The TEM images of NVP-650 (a, b) and NVP-850 (c, d).

2

Figure S4. The FESEM images of precursors with different reaction time: (a) 1 min; (b) 5 min (c) 10 min and (d) 20 min.

Figure S5. XRD patterns of (a) precursor; (b) NVP-650 and NVP-750; (c) NVP-850 and (d) the sample without adding any glucose annealed at 750 oC.

3

Table S1. The FWHM of several main XRD peaks of NVP-650 and NVP-750.

Peaks (012) (104) (113) (024) (211) (300) FWHM (NVP-650) 0.345 0.499 0.557 0.541 0.901 0.293 FWHM (NVP-750) 0.284 0.450 0.499 0.495 0.805 0.282

Figure S6. The Raman spectrum of the sample without adding any glucose and annealed at 750 oC.

Figure S7. The Nitrogen adsorption-desorption isotherms and corresponding pore size distribution (inset) of (a) NVP-650 and (b) NVP-850.

4

Figure S8. AC-impedance spectra of NVP-650, NVP-750 and NVP-850.

Figure S9. The cycling performance of the sample (without adding any glucose; annealed at 750 oC) measured at 0.91 C in the voltage range of 1- 4.3 V.

Figure S10. The rate performance of NVP-750 in different voltage windows in comparison of the report work (Ref 1, Ref 2, Ref 3 and Ref 4).

5

Reference

[1] W. X. Song, X. B. Ji, C. C. Pan, Y. R. Zhu, Q. Y. Chen, C. E. Banks, Phys. Chem. Chem. Phys. 2013, 15, 14357. [2] W. X. Song, X. B. Ji, Y. B. Yao, H. J. Zhu, Q. Y. Chen, Q. Q. Sun, C. E. Banks, Phys. Chem. Chem. Phys. 2014, 16, 3055. [3] K. Du, H. W. Guo, G. R. Hu, Z. D. Peng, Y. B. Cao, J. Power Sources 2013, 223, 284. [4] Z. L. Jian, W. Z. Han, Y. L. Liang, Y. C. Lan, Z. Fang, Y.-S. Hu, Y. Yao, J. Mater. Chem. A, DOI: 10.1039/C4TA04630G.

Figure S11. The XRD pattern of the NVP-750 after soaking in 1 M LiPF6/EC+DMC electrolyte for 12 h.

6