均匀负载氧化镍纳米颗粒多孔硬碳球的制备及其高性能锂离子电池负极材料应用

张远航　王志远　师春生　刘恩佐　何春年　赵乃勤（天津大学材料科学与工程学院，天津市材料复合与功能化重点实验室，天津30007；天津化学化工协同创新中心，天津30007）

均匀负载氧化镍纳米颗粒多孔硬碳球的制备及其高性能锂离子电池负极材料应用

张远航1王志远1师春生1，*刘恩佐1何春年1赵乃勤1，2
（1天津大学材料科学与工程学院，天津市材料复合与功能化重点实验室，天津300072；2天津化学化工协同创新中心，天津300072）

利用水热法制备了粒径为90-130 nm的多孔硬碳球，并通过浸渍与煅烧的方法制备了硬碳球均匀负载纳米氧化镍颗粒（～10 nm）复合材料.硬碳球的表面官能团和内部的微孔保证了氧化镍颗粒在硬碳上的均匀分布.在100 mA·g-1的电流密度下，复合材料电极首次充电比容量高达764 mAh·g-1；在100 mA·g-1的电流密度下循环100个周期后电极充电比容量保持在777 mAh·g-1，容量保持率为101%；800 mA·g-1电流密度下电极的充电比容量达380 mAh·g-1，显示复合材料电极具有优异的循环性能和倍率性能.硬碳的表面官能团和内部微孔为氧化镍提供了优先形核位点，保证了二者的牢固结合，使复合材料获得了“协同效应”，从而使复合电极具备更短的锂离子扩散路径、更高的电导率和更多的锂离子脱嵌位点.这种方法还可用于制备硬碳/其他金属氧化物复合材料.

微孔；水热法；浸渍；表面官能团；循环性能；倍率性能

www.whxb.pku.edu.cnAbstract：Uniform nickel oxide nanoparticles（～10 nm）embedded in porous hard carbon（HC）spheres（90-130 nm）for high performance lithium ion battery anode materials were synthesized via a hydrothermal method followed by impregnation and calcination.The HC spheres，which had abundant micropores and plentiful surface functional groups，allowed firm embedding and uniform dispersion of the NiO nanoparticles.The as-prepared HC/NiO composite anode exhibited excellent electrochemical performance，including high reversible capacity （764 mAh·g-1），good cycling stability（a high specific capacity of 777 mAh·g-1after the 100th cycle at a current density of 100 mA·g-1，a capacity retention rate of 101%），and high rate capability（380 mAh·g-1even at 800 mA·g-1）.These excellent electrochemical properties were attributed to the unique structure of NiO nanoparticles tightly embedded in a hard carbon matrix.Anode materials with such a structure have the advantages of improved electronic conductivity，more accessible active sites for lithium ion insertion，and short diffusion pathsfor lithium ions and electrons.The observed“synergistic effects”between the hard carbon and NiO represent an advance in the electrochemical performance of such composites.The present method is an attractive route for preparing other hard carbon/metal oxide composite anodes for lithium ion batteries.

1　lntroduction

Despite the proliferation of various new anode materials，carbonaceous materials are still the most widely used for Li ion batteries owing to their low cost，abundant raw materials，simple preparation methods，and excellent cycling performance.However，fast insertion of Li ions into graphite leads to the formation of lithium dendrites on the anode surface，which causes poor rate performance，capacity fading，and safety problems.1Ungraphitized carbon，also called hard carbon（HC），has attracted great attention since it was first reported by Mabuchi2and Sonobe3et al.，owing to the following advantages：（i）different from graphite，the charge-discharge curves of HC have slopes instead of plateaus，making it easy to calculate battery capacity according to its potential and is beneficial for battery management；（ii）the preparation temperature of HC（lower than 800°C）is much lower than that of graphite（higher than 2000°C）；（iii）no potential security risk caused by lithium dendrites；（iv）it is much easier for hard carbon to form composites with other anode active materials than for graphite.Recent works have successfully prepared hard carbon by pyrolysis of polymers such as phenolic resin4，5and coal tar pitch，6autogenic reactions using waste plastic，7carbonization of biomass such as potato starch，8mangrove charcoal9and rice husk，10and hydrothermal reaction of saccharides.11However，almost all the hard carbons prepared by the above methods are micron-sized and irregular or heterogeneous in morphology.5-11In fact，the preparation of uniform nanoscale hard carbon spheres is essential for high performance HC anodes.

Various metal oxides have been extensively investigated as anode materials for Li-ion batteries.Among them，Nickel oxide （NiO）has attracted a large amount of attention owing to its high theoretical capacity of 718 mAh·g-1.12However，like other metal oxides，the cycling performance and rate capability of NiO are unsatisfactory.This can be ascribed to the following reasons：first，the conductivity of NiO is poor，and the lithium oxide（Li2O）generated in the electrochemical reaction further reduces its conductivity.Second，the volume of NiO expands greatly after lithium insertion，resulting in the loss of electrical contact between the active material and the current collector.Volume expansion is also to blame for the bonding of atoms between adjacent particles，which results in the electrochemical aggregation of active material，causing loss of its electrochemical activity.Combining the metal oxide with carbonaceous material is an effective method of overcoming these issues.Carbonaceous materials such as porous carbon，13，14amorphous carbon，15graphene，16-18or carbon nanotubes19can serve as not only a mechanical substrate to accommodate the volume change of metal oxide，but also as a conductive matrix to suppress the pulverization of the metal oxide during cycling.Thus，such composites can achieve excellent electrochemical performance arising from the“interfacial lithium storage”.This phenomenon can be attributed to a“synergistic effect”，which induces better performance than the simple sum of the two components.20-24

In this paper，we combined a hard carbon anode material with nickel oxide via impregnation and calcination methods to obtain a new type of HC/NiO composite.The electrochemical performance of the HC/NiO composite was investigated and compared with those of pristine NiO and HC.Our results indicate that the HC/NiO composite is expected to display superior performance for lithium ion storage.

2　Experimental

2.1Preparation of hard carbon spheres

Nano-sized hard carbon spherical particles were synthesized by a hydrothermal method followed by calcination at high temperature.In a typical process，1.5 mol·L-1aqueous glucose solution was placed into a 100 mL Teflon-lined stainless steel autoclave and heated at 160°C for 10 h.The dehydration and polycondensation of the glucose during the hydrothermal process resulted in the formation of a nano-sized perfectly spherical precursor with many surface functional groups.After rinsing and freeze-drying，this hydrothermal product was then carbonized at 800°C for 8 h in Ar atmosphere to form a carbonaceous material（denoted as HC）with a unique porous and amorphous structure.

2.2Preparation of hard carbon-NiO composite

NiO was introduced into the HC by immersion and low temperature calcination.The as-obtained HC（0.3 g）was impregnated with a solution prepared by dissolving 0.35 g nickel（II）nitrate hexahydrate（Ni（NO3）2·6H2O，99.97%purity）in 300 mL absolute ethyl alcohol（99.7%purity）.The suspension was stirred vigorously at 65°C until all the solvent was evaporated.To avoid burning the HC during the heating process，and to ensure the purity of the NiO，the precursor was first heated under H2atmosphere at 450°C for 1 h to obtain HC-Ni，and then calcined at 250°C for 6 h in air to obtain the final HC-NiO composite.The resulting nano-sized NiO particles were firmly and uniformly embedded in the HC.For comparison purposes，pure NiO was prepared under the same conditions without the presence of HC.

2.3Material characterization

The crystal phases of the samples were identified by X-ray diffraction（XRD）analysis（Bruker，Germany）using a Rigaku D/max diffractometer with Cu Kαradiation at a wavelength of 0.15406 nm，and a step size of 0.02°.The morphologies of the samples were observed with an S-4800 scanning electron microscope（SEM；Hitachi，Japan）and a FEI Tecnai G2 F20 transmission electron microscope（TEM；FEI，the Netherlands）.The samples for TEM imaging were ultrasonically dispersed in absolute ethyl alcohol，and one drop of suspension was deposited on a copper grid，while SEM samples were collected directly from the product powders.Energy-dispersive X-ray spectroscopy （EDS）analyses were carried out using a spatially resolved EDS spectroscope attached to the SEM.Nitrogen adsorption isotherms were measured at 77 K using an autosorb iQ instrument （Quantachrome，U.S.）.The total surface area was calculated using the Brunauer-Emmett-Teller（BET）method and the pore size distribution data were calculated using density functional theory （DFT）based on the adsorption and desorption data.Fourier transform infrared（FTIR）spectra were obtained using a Bruker TENSOR 27 spectrometer（Bruker，Germany）.The FTIR samples were prepared using the KBr pellet method，and the obtained spectra were normalized using OPUS 6.5 software.Thermal gravimetric analysis（TGA）was carried out in air using a Perkin-Elmer thermal analyzer（TAInstruments，U.S.）at a heating rate of 5°C·min-1up to 800°C.

2.4Electrochemical measurements

Coin cells（2032）were assembled in an argon-filled glove-box using lithium foil as the counter and reference electrode.The working electrode was composed of the active material，conductive agent（carbon black），and binder（polyvinylidene fluoride）in a mass ratio of 80：10：10 on a copper foil.The electrolyte was LiPF6（1 mol·L-1）in ethylene carbonate（EC）/dimethyl carbonate （DMC）/diethyl carbonate（DEC）（1：1：1（volume fraction））.The cells were galvanostatically discharged and charged at various current densities between 0 and 3 V at room temperature on a LAND CT2001Abattery-testing system（Wuhan LAND Electronics Co.，Ltd.）.Electrochemical impedance spectroscopy（EIS）measurements were performed using a CHI660D electrochemical workstation（Shanghai Chen Hua Instrument Co.，Ltd.）with an AC voltage of 5 mV amplitude at 0.1-100 kHz.

Fig.1　SEM images of（a）HC，（b）HC-NiO，and（c）NiO；EDS characterization of HC-NiO structure of（d）carbon，（e）nickel，and（f）oxygen mappings of the region shown in（b）

3　Results and discussion

3.1Morphology and structure

The morphologies of HC，HC-NiO，and NiO observed by SEM are shown in Fig.1.Fig.1（a）shows that the HC had perfect spherical morphology with a smooth surface and a narrow diameter distribution of 90-130 nm.The spherical morphology of HC was maintained in the HC-NiO composite，but the surface of the HC spheres became rough after the NiO nanoparticles were embedded，as shown in Fig.1（b）.All the NiO nanoparticles were uniformly anchored in the HC spheres and very few individual NiO particles were found in the sample.Although the NiO nanoparticles are just a few nanometers in size，there was no agglomeration of these tiny particles.Conversely，the obtained NiO without carbon matrix was heavily agglomerated，as shown in Fig.1（c）.This is strong evidence that the NiO nanoparticles were strongly embedded in the HC spheres instead of just physically adhered to them.EDS mapping was employed to further confirm the unique HC-NiO structure，as shown in Fig.1（d-f）.C，Ni，and O elements were distributed homogeneously，indicating that the NiO nanoparticles were dispersed uniformly on the HC spherical particles.Nanostructured electrode materials have many potential advantages including：（i）better rate performance owing to short path lengths for electron and Li+transportation；（ii）higher specific capacity owing to a larger electrode/electrolyte contact area and（iii）better accommodation of the strain of active material caused by lithium insertion/removal.Therefore，we speculate that the unique nanostructure of the present composite will provide superior electrochemical performance.

The structure of HC was analyzed by a series of characteriza-tion methods.Fig.2（a，b）shows the adsorption/desorption isotherms and pore size distribution of HC，which reveal that the obtained HC was porous with a high surface area of 655 m2·g-1and a total pore volume of 0.461 cm3·g-1calculated by DFT.The numerous micropores inside HC were able to encapsulate the tiny metal oxide particles.Fig.2（c）shows the FTIR spectrum of HC in the 3200-600 cm-1region.The spectrum reveals that a large number of surface functional groups were present on HC.The bands at 2924，2857，and 1450 cm-1can be assigned to the vibrations of―CH，while the bands at 1625 and 1385 cm-1can be assigned to the vibrations of―COOH and―NO2，respectively. The bands at 1258 and 1120 cm-1can be assigned to vibrations of C―O―C.

Fig.2　（a）Nitrogen adsorption/desorption isotherms of HC，（b）pore size distribution of HC，（c）FTIR spectrum of HC，and（d）TGAcurve of the HC-NiO composite

Fig.2（d）shows the TGAcurve of the obtained composite during heating in air.The weight loss between 436 and 600°C is ascribed to the oxidation of carbon.Because the NiO component remained stable during the heating process，the mass fraction of NiO in the composite could be determined to be 26.4%（w）from the TGA curve.

The XRD patterns of HC，HC-NiO，and NiO are shown in Fig.3.The typical disordered structure of the as-prepared carbon spheres is evidenced by the broad X-ray diffraction peaks centered at approximately 26°and 44°（2θ），which correspond to the（002）and（100）reflections，respectively.12A broad（002）diffraction peak was still visible after the embedding of NiO particles while the broad（100）peak was covered by the characteristic（200）peak of NiO，as shown in Fig.3（b）.Additionally，a few other characteristic（（111）and（220））peaks of NiO were also observed for the HC-NiO composite.The peak positions of the NiO in the composite agreed well with those of the obtained pure NiO.

Fig.3　XRD patterns of（a）HC，（b）HC-NiO，and（c）NiO

TEM and high resolution（HR）TEM images of HC and HCNiO are shown in Fig.4.It is clear from Fig.4（b）that the obtained carbon spheres had an amorphous structure composed of many short buckled graphitic sheets and micropores，which is consistent with the XRD and BET results.It should be noted that the NiO nanoparticles were still strongly anchored to the HC spheres even after ultrasonic dispersion during TEM sample preparation，as shown in Fig.4（c，d），indicating a strong bonding between them. Besides，it can be seen that the NiO nano-particles remaineduniformly dispersed on the HC spheres.Fig.4（e）shows a HRTEM image of uniformly dispersed NiO particles with diameter of about 10 nm on the amorphous carbon structure.It is speculated that a portion of the NiO particles were encapsulated inside the micropores of the HC spheres，while the rest nucleated on the surface，with possible C―O―Ni bond formation.25These factors enabled the strong pinning and good dispersion of NiO on the HC spheres.The observed lattice fringes with an interplanar spacing of 0.14 nm correspond to the（200）lattice planes of cubic NiO，revealing that the embedded NiO particles were crystalline.

Fig.5（a，b）shows the adsorption/desorption isotherms and pore size distribution of the composite.Both the BET surface area and pore volume of the composite were decreased compared with those of HC shown in Fig.2（a，b）.We speculate that this decrease in surface area and pore volume was caused by the embedment of a portion of the NiO particles into the micropores of the HC spheres.

Based on the above characterization results，we propose a possible mechanism for the formation of the HC-NiO composite，as illustrated in Scheme 1.First，amorphous carbon spheres were formed during the hydrothermal and calcination processes.During the hydrothermal process，the glucose molecules were dehydrated to an amphiphilic species with a hydrophobic end and a hydrophilic end.These compounds formed spherical micelles with hydrophobic ends in the core and hydrophilic ends on the surface.26The spherical micelles grew via the incorporation of adjacent hydrophilic ends，thus forming the spherical morphology of HC with many surface functional groups.During the calcination process，the precursors degassed further，forming abundant micropores within the spheres.The relatively low calcination temperature used meant that the obtained carbon spheres were amorphous.

Fig.4TEM images of HC（a）and HC-NiO（c，d）；HRTEM images of HC（b）and HC-NiO（e，f）

Fig.5　Nitrogen adsorption/desorption isotherms（a）and pore size distribution（b）of HC-NiO

During the impregnation step，Ni2+was introduced to HC.A portion of the Ni2+diffused into the carbon spheres through nanochannels formed by the abundant micropores and were effectively encapsulated in the micropores.Meanwhile，the surfacefunctional groups of HC provided favorable nucleation sites for the Ni2+attached to the surface of the carbon spheres.27These nickel ions were reduced to metallic nickel during the calcination step in hydrogen.Because amorphous carbon is also a reducing agent，a small quantity of nickel ions may also have been reduced by the carbon.However，little carbon matrix was consumed in the H2atmosphere.When calcined at 250°C in air，the nickel metal transformed into nickel oxide.Strong C―O―Ni bonding may have formed between the carbon matrix and NiO during this process.In other words，an“oxygen bridge”formed at the interface between HC and NiO.25Because the temperature was too low for the oxidization of carbon according to the TGA results，only metallic Ni was converted from Ni2+→Ni0→NiO during the calcination process，and eventually a NiO particle-embedded HC composite was obtained.

Scheme 1　Schematic illustration for the synthesis of HC-NiO

Fig.6　Galvanostatic charge-discharge profiles of HC，NiO，HC-NiO for the first cycle

3.2Electrochemical properties

Aseries of electrochemical tests were carried out to investigate the electrochemical properties of the composite structure.Fig.6 shows the initial charge-discharge profiles of HC，NiO，and HCNiO at a constant current density of 100 mA·g-1.Along potential plateau is visible around 0.7 V in the first discharge curve for NiO，which is attributed to the formation of a solid electrolyte interphase（SEI）film and the reduction of Ni2+to Ni0according to the electrochemical reaction：2Li+NiO→Li2O+Ni.12There are two plateaus located at about 1.25 and 2.25 V in the charge curve，corresponding to the decomposition of the SEI film and the reverse reaction for the transformation of Ni2+from Ni0，respectively.12For HC，slopes instead of obvious plateaus were observed in the charge-discharge curves，which is typical for amorphous carbon anode materials.This phenomenon is beneficial when it comes to battery management，especially in power batteries，for calculating battery capacity according to the potential in the charge-discharge curve.The charge-discharge curve of HC-NiO also shows slopes without obvious plateaus.The first charge specific capacity of HC-NiO is 764 mAh·g-1，which is much higher than the simple sum of the first charge specific capacities of HC and NiO（526×74.6%+725×26.4%=583.8 mAh·g-1）.

Fig.7（a）shows the cycling performance of HC，NiO，and HCNiO tested at 100 mA·g-1within the voltage window 0-3 V.The capacity retention of HC was excellent，evidenced by the superb electrochemical stability of the amorphous carbon material anode. This also indicated that the HC obtained in this work is an appropriate matrix for the loading of other anode active materials. However，the NiO decayed very quickly，although it showed high first chargeanddischargespecificcapacities of 1573and728mAh· g-1，respectively，higher than its theoretical specific capacity of 718 mAh·g-1.The capacity faded quickly to 134 mAh·g-1within 50 cycles，then became very stable.This indicated that a large portion of NiO lost its electrochemical activity during Li+insertion-extraction and that the use of the active material was rather low.In the case of HC-NiO，the capacity faded at the beginning and then increased gradually until the 23rd cycle.After the activation process，the coulombic efficiencies of the subsequent cycles were higher than 97%.The charge specific capacity of the composite at 100th cycle was 777 mAh·g-1，slightly higher than the charge specific capacity of the first cycle after the activation process and cycling，illustrating the excellent cycling performance of the HC-NiO composite.

The cycling performance of HC-NiO and the theoretical performance derived from the simple sum of the cycling performance of the two components are shown in Fig.7（b）.The specific capacity of the curve at the bottom was calculated according to the following formula，

where，Ctheoretical HC-NiOis theoretical specific capacity，CHCor CNiOis tested specific capacity，wHCor wNiOis mass fraction.Comparisonof the curves shows that the specific capacity of the composite was higher than the simple sum of those of the two components. We attribute this phenomenon to a“synergistic effect”，which means that the composite achieved better performance than each individual component and the simple sum of the individual effects.26-28The growth of the NiO nanoparticles was effectively limited by the amorphous carbon matrix，as shown in Figs.1 and 4，which indicates that the composite possessed more defect sites，nanoclusters and hollow cores.The above factors would greatly enhance the capacity and result in the observed“synergistic effect”.22Besides，the abundant oxygen-containing functional groups on the surface of carbon matrix，as shown in Fig.2（c），also contributed to the extra capacity owing to the formation of an oxygen bridge between carbon and NiO.25

The morphology of the HC-NiO composite electrode after charge/discharge cycling was studied by TEM.Fig.8 shows TEM images of the HC-NiO hybrid anode after 23 cycles.Fig.8（a）reveals that the active material was surrounded by a polymer/gellike film，which may be attributed to the observed gradually increasing capacity.29-31Additionally，compared with the pristine product，more NiO nanoparticles were seen in the carbon matrix after the intercalation and deintercalation of Li+，as shown in Fig.8 （b）.Considering the abundant nanopores in the composite and its typical porous structure，we speculate that the gradual increase in capacity may have occurred partly because the nanopores gradually opened，causing more reactive sites of composite to become electrochemically active.26，27Moreover，Fig.8（b，c）shows that the NiO nanoparticles had not aggregated at all after 23 chargedischarge cycles and were still uniformly and firmly anchored to the HC matrix，with a morphology similar to that of the pristine product.This is strong evidence for the powerful bonding between the two components being the cause of the excellent cycling performance.

Fig.7　Cyclic performance of（a）HC，NiO，HC-NiO tested at 100 mA·g-1in the potential range of 0-3 V；（b）comparison of HC and simple sum of tested specific capacity of HC and NiO

Fig.8　Typical TEM images of HC-NiO hybrid electrode after 23 electrochemical cycles of（a）gel-like film on HC particle and （b）tiny NiO nanoparticles on HC；（c）high resolution image of（b）

Fig.9（a）shows the rate capabilities of HC-NiO and HC.For comparison，rate capabilities were also measured after the active process.The cell was tested for 15 cycles at current densities of 100，200，400，and 800 mA·g-1，and then tested at 100 mA·g-1again.The specific capacities of HC-NiO at these current densities were 760，580，460，and 380 mAh·g-1，respectively.When the current density was changed back to 100 mA·g-1，the cell still delivered the same specific capacity as that obtained earlier at the same current density.This means that the structure remained stable during the whole process，and was not destroyed when Li+was fast intercalated and deintercalated even when the cell was charged and discharged at high current density.

Similar to the HC-NiO composite，HC also maintained its specific capacity after testing at various current densities，confirming the structural stability of the carbon matrix and proving that the obtained HC is a good matrix for loading other anode active materials.The rate performance of pure NiO is shown in Fig.9（b）.The charge specific capacity of NiO dropped below 20 mAh·g-1when tested at a current density of 200 mA·g-1，andreached 10 mAh·g-1at 400 and 800 mA·g-1.Thus，the pure NiO totally lost its electrochemical activity when tested at higher current densities.These results indicated that the NiO nanoparticles could be fully used only when loaded onto the HC matrix.

Fig.9　Rate capabilities of（a）HC-NiO and HC and（b）NiO

Fig.10 shows the electrochemical impedance spectra（EIS）of HC-NiO and NiO electrodes.The equivalent circuit shown in the inset of Fig.10 included four elements：（i）the electrolyte resistance（Re）；（ii）the solid electrolyte interface and charge transfer resistance（R（sei+ct））；（iii）the capacitance of the solid electrolyte interface and charge transfer（CPE（sei+ct））；（iv）the lithium ion diffusion impedance（Zw）.32，33The values of R（sei+ct）for HC-NiO and NiO were 107.5 and 122.4 Ω，respectively.The lower R（sei+ct）value of HC-NiO means that the composite electrode had a more stable SEI film，higher electrical conductivity，and faster charge-transfer process than the pure NiO.The HC conductive network improved the electrical conductivity of the HC-NiO composite compared with that of pure NiO，allowing a much better rate performance to be achieved.

Fig.10　Electrochemical impedance spectra of HC-NiO and NiO electrodes and the Nyquist plots（inset）Re：electrolyte resistance；R（sei+ct）：solid electrolyte interface and charge transferresistance；CPE（sei+ct）：capacitance of solid electrolyte interface and charge transfer；Zw：lithium ion diffusion impedance

4　Conclusions

We successfully prepared uniformly dispersed NiO nanoparticles embedded in HC spheres via a hydrothermal method followed by impregnation and calcination.Numerous micropores inside the HC spheres as well as surface functional groups ensured strong bonding between the carbon matrix and NiO nanoparticles. The unique structure obtained effectively restrained the volume expansion/contraction of NiO associated with lithium insertion/ extraction，and help maintain the structural integrity of the electrode.The nanosized NiO facilitated the fast diffusion of lithium ions，and the conductive network of the carbon matrix improved the electrical conductivity of the composite material.As a result，the composite demonstrated a high reversible capacity（764 mAh· g-1），good cycling performance（a high specific capacity of 777 mAh·g-1after the 100th cycle at a current density of 100 mA·g-1，with a capacity retention of 101%），and high rate capability（380 mAh·g-1even at 800 mA·g-1）.The electrochemical performance of the composite was superior to the simple sum of those of each individual material，evidencing that a“synergistic effect”was achieved in the HC/NiO composite anode.Furthermore，the approach reported in this work is also applicable to the preparation of other transition metal oxide nanocrystals embedded in HC spheres with significantly enhanced electrochemical performance for various applications.

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Synthesis of Uniform Nickel Oxide Nanoparticles Embedded in Porous Hard Carbon Spheres and Their Application in High Performance Li-lon Battery Anode Materials

ZHANG Yuan-Hang1WANG Zhi-Yuan1SHI Chun-Sheng1，*LIU En-Zuo1HE Chun-Nian1ZHAO Nai-Qin1，2
（1Tianjin Key Laboratory of Composites and Functional Materials，School of Materials Science and Engineering，Tianjin University，Tianjin 300072，P.R.China；2Synergetic Innovation Center of Chemical Science and Engineering，Tianjin 300072，P.R.China）

September 3，2014；Revised：November 26，2014；Published on Web：November 26，2014.

Micropore；Hydrothermal method；Impregnation；Surface functional group；Cycling performance；Rate capability

O646

10.3866/PKU.WHXB201411261

The project was supported by the China-EU Science and Technology Cooperation Project（1206）and Key Technologies R&D Program of Tianjin，China（12ZCZDGX00800）.

科技部对欧盟科技合作专项经费项目（1206）及天津市科技支撑计划重点项目（12ZCZDGX00800）资助

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