Mechanical Pressing Route for Scalable Preparation of

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A mechanical pressing route for scalable preparation of micro/ nanostrutured Si/graphite composite for lithium ion battery anodes Zheng Yi, Weiwei Wang, Yong Qian, Xianyu Liu, Ning Lin, and Yitai Qian ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b02880 • Publication Date (Web): 13 Sep 2018 Downloaded from http://pubs.acs.org on September 17, 2018

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ACS Sustainable Chemistry & Engineering

A mechanical pressing route for scalable preparation of micro/nanostrutured Si/graphite composite for lithium ion battery anodes Zheng Yi, Weiwei Wang, Yong Qian, Xianyu Liu, Ning Lin,* and Yitai Qian

Department of Applied Chemistry, University of Science and Technology of China, No. 96, Jinzhai Road, Hefei, Anhui 230026, P. R. China.

E-mail: [email protected].

KEYWORDS: Lithium-ion batteries; anode; Si; graphite; mechanical pressing route

ABSTRACT:

Si/graphite composite has been regarded as one of the promising anode material for next-generation lithium ion batteries (LIBs). Herein, we reported a mechanical pressing route to large-scalely fabricate Si-embedded/graphite composite with increased tap density and decreased BET specific surface area. By mechanical pressing of well-dispersed Si and graphite particles, the Si nanoparticles are embedded into the graphite sheets, and forming ingot-shaped tablet. After secondary grinding, the aggregated Si/graphite (Si/G) microparticles are obtained with close integration of Si and graphite at nanoscale. Finally, a layer of amorphous carbon was deposited on the above composite (Si/G/C microparticles) via 1 ACS Paragon Plus Environment

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decomposing acetylene to further maintain the structure stability of the Si/G/C microparticles. As a result, the as-obtained Si/G/C microparticles deliver a discharge capacity of 520.7 mA h g−1 at 0.2 C after 100 cycles and 370 mA h g−1 at 1 C after 800 cycles, associated with improved coulombic efficiency. The full cell assembled with the Si/G/C microparticles as anode and commercial LiCoO2 as cathode can maintain capacity retention of about 80% at 0.5 C after 50 cycles with a working potential beyond than 3.1 V. The improved performance could be attributed to the enhanced structural stability and good integration of Si and graphite at nanoscale after mechanical pressing.

Introduction

Silicon (Si) has been considered as an attractive anode material for rechargeable lithium ion batteries (LIBs) for its high theoretical capacity of 3600 mA h g−1 with the formation of Li3.75Si phase and low potential plateau below 0.5 V (vs. Li+/Li).1-3 However, the complications also arise in the formation of huge volume expansions greater than 300% upon full lithiation, which practically makes pulverization and structural disintegration of the electrode. As a result, unstable and thicker solid electrolyte interface (SEI) layers are derived, and thus the capacity decays rapidly during cycling.4-5

To suppress the above problems of the Si anode, numerous strategies have been developed. First of all, reducing the grain size to be nanostructured is a good approach.6-9 Our group has fabricated the nano-silicon by metallothermic reduction of SiCl4 in the molten salt 2 ACS Paragon Plus Environment

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of AlCl3 at 200 oC. The obtained nano-silicon delivered a reversible capacity of 3083 mA h g−1 at 1.2 A g−1 after 50 cycles.10 Moreover, another well-accepted approach is to introduce the carbon additive into/onto Si anode. The carbon additive such as graphene, carbon nanotube, and amorphous carbon were reported typically.11-16 As a representative case, Si-embedded porous carbon microspheres with an exceptional conductive framework exhibited a high capacity of 1325 mAh g−1 at 0.2 A g−1 after 60 cycles.15 However, due to the high specific surface area, these nanostructured Si and Si-based composites are difficult to practically apply.17

Recently, the combination of Si nanoparticle with commercial graphite was considered as a promising anode material for high-capacity LIBs, due to the combined superiority of Si nanoparticle with high theoretical capacity and graphite with stable mechanical structure.19-20 For preparation of the Si/graphite composite, various routes such as high-energy mechanical ball-milling, spray-drying, and chemical vapor deposition have been developed.20-24 For example, spherical Si/carbon/graphite composite with 12 wt.% of Si content fabricated by heating the Si/pitch/graphite at 1000 °C and maintained 80% of its initial capacity after 100 cycles.25 Si-nanolayer-embedded graphite composite has been fabricated by Cui et al. via a chemical vapor deposition route, which showed a specific capacity of 476.6 mAh g−1 over 100 cycles with a capacity retention of 96%.20 Although great developments have made in this field, there are still some limitations. For instance, the high-energy mechanical ball-milling method could only mix the Si and graphite loosely; the products obtained by spray-drying have lower tap density; and the chemical vapor deposition using SiH4 as Si source is expensive and dangerous. Hence, a more inexpensive and scalable route is also 3 ACS Paragon Plus Environment


needed to develop Si-embedded/graphite composite for high-capacity LIBs with better compatibility in industrial production.

In this work, a mechanical pressing route is developed to large-scalely fabricate the Si-embedded/graphite composite for application in LIBs. In the first step, the Si nanoparticle and graphite are well mixed by mechanical ball-milling technique. The mixture (Si/G composite) is then mechanically pressed at a tunable pressure in a closed cavity. After secondary grinding by hand in a mortar, the microsized Si/G composite is obtained. Here, to further enhance the structural stability, the microsized Si/G composite is coated with an amorphous carbon layer (the obtained composite is denoted as the Si/G/C composite) by a chemical vapor deposition method. Because of the enhanced structural stability and good integration of Si and graphite at nanoscale, the microsized Si/G/C composite exhibits decreased specific surface area and improved lithium storage performances in comparison with the Si nanoparticle and milled Si/G composite.

EXPERIMENTAL METHODS

Synthesis of Si-embedded/graphite/carbon (Si/G/C) microparticles. The original graphite was firstly ball milled in a planetary ball mill machine (MSK-SFM-1, purchased from Hefei Ke Jing Materials Technology CO., LTD.). Then, 1.8 g of ball-milled graphite and 0.2 g of Si nanoparticles was further ball milled at 500 r min-1 for 12 h to obtain the Si/G composite. As shown in Fig.1a, the obtained Si/G composite was then mechanically pressed at 6, 12 and 18 t (i.e. 10, 20 and 30 MPa) for 10 min under a FW4 Tablet Press Machine, respectively. The 4 ACS Paragon Plus Environment

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obtained disc (Fig.1b) was hand-grinded to produce the microsized Si-embedded/graphite microparticle, which was then heated at 700 oC for 1 h under the controlled C2H2 (C2H2: 10% and Ar: 90%) flow speed of 8 ml min-1. When the furnace was cooled naturally, the final microsized Si-embedded/graphite/carbon (Si/G/C composite) composites were obtained. The Characterization and Electrochemical measurements sections were detailed in the Supporting Information.

Results and discussion

Fig.1a

schematically

illustrates

the

fabrication

process

of

the

Si-embedded/graphite/carbon (Si/G/C) microparticles. To begin with, uniformly dispersed Si and graphite mixture is obtained by a mechanical ball milling technique. Subsequently, the Si/G mixture is mechanically pressed at a tunable pressure to produce the ingot-shaped tablet (Fig.1c) with close-knit Si nanoparticle and the graphite sheets. It is worth noting that the compaction density of the pressed Si/G sample can be calculated to be 1.638 g cm-3 at 6 t and 1.837 g cm-3 at 18 t by measuring the diameter and thickness of the pressed tablet. During the pressing process, the Si nanoparticles and the graphite sheets undergo repacking and rearrangement under the positive pressure as well as the wall pressure, as schematically interpretation in Fig.1b. Because of the internal force of friction between the Si nanoparticles and the graphite powders, the partial displacement and deformation of the powders endow the hybrid with uniformly distribution of Si nanoparticles into the graphite sheets. Therefore, after hand-grinding, the obtained Si/G microparticles with enhanced tap density (Fig.1d) also 5 ACS Paragon Plus Environment


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have good integration of Si and graphite at nanoscale. Finally, an amorphous carbon layer is coated onto the Si/G microparticle by a chemical vapor deposition method to further enhance the structural stability.

Fig. 2 shows the morphology changes of the Si nanoparticle, ball-milled graphite, Si/G composite and Si/G/C microparticle. As presented in Fig. 2a and i, the Si nanoparticle has a particle size between 50 and 300 nm and an average size of 150 nm. The milled graphite (Fig.2b) exhibits decreased particle size after ball-milling treatment compared with the original sample (Fig.S1, Supporting information). As shown in Fig. 2j, the particle size of the milled graphite is varied from 1 to 6.5 µm. By employing the mechanical ball milling technique, the obtained Si/G mixture presents uniformly distributional Si nanoparticle into/onto graphite sheets, as displayed in Fig. 2c. However, before mechanically pressed, the mixture of Si nanoparticles and graphite sheets stacks loosely (Fig. 2d). It changes to be compacted after mechanically pressed, as shown in Fig. 2f. The size of the secondary particle is changed up to be micrometer scale (Fig. 2e). After mechanically pressed and coated with amorphous carbon layer, the particle size of the obtained Si/G/C composite is ranging from 4 to 22µm (Fig. 2g and k). To further reveal the architectural feature of the Si/G/C microparticle, the high-resolution SEM and TEM image is carried out. As shown in Fig. S2 (Supporting information), the Si nanoparticle is well encapsulated into the graphite sheets or amorphous carbon layer, which is further confirmed by the TEM image in Fig. 2h. This architectural feature may be in favor of improving the lithium storage performance, such as enhancing the buffer effect, maintaining the structural stability.

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Fig. 2l shows the N2 adsorption/desorption isotherms of the Si nanoparticle, ball-milled graphite, Si/G mixture and Si/G/C microparticles. The BET surface area of Si/G/C microparticle is about 28.5 m2 g-1, which is lower than that of the milled Si/G mixture without treating by mechanical pressure (42.8 m2 g-1). Meanwhile, the tap density of the Si/G/C microparticle could be significantly enhanced in comparison with the counterpart of ball-milled Si/G mixture, as demonstrated in Fig. 1d.

XRD patterns, Raman spectra and TG curves are employed to characterize the structural and componential features of the obtained products. Fig. 3a exhibits the XRD patterns of the Si nanoparticle, ball-milled graphite, Si/G composite and Si/G/C microparticles. The sharp diffraction peaks of the Si nanoparticle and ball-milled graphite indicate the high purity and good crystallinity. As for the Si/G composite and Si/G/C microparticle, the composite both contains of two phases of Si and graphite. The characteristic peak of graphite is more apparent, suggesting that the graphite is the main phase in the composite. The diffraction peaks at 28.4, 47.3 and 56.1 degree are relatively weak, which are assigned to the cubic Si phase (JCPDS 27-1402). There is no obviously difference between the Si/G and Si/G/C powder samples. The Raman spectra in Fig. 3b are used to further characterize the structural properties of these composites. The sharp peak at 517 cm-1 is ascribed to the optic phonons of Si–Si stretching mode in crystalline Si, while the peak at 1353 cm−1 and 1582 cm−1 are the D (disordered) and G (graphite) band of the graphite as well as the amorphous carbon. As for the graphite, the D band is very lower. However, due to the insertion of Si nanoparticles into the flakes of graphite and the unordered nature of the deposited amorphous carbon, the Si/G/C microparticle shows the highest D band compared to other samples. The peak 7 ACS Paragon Plus Environment


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intensity of Si in Si/G/C microparticle is lower than that in the Si/G composite, suggesting the well coating amorphous carbon layer is obtained. According to the TG curves (Fig. S3, Supporting information), the Si content in Si/G composite is 10 wt.%, in agreement with the original ratio of the Si nanoparticle and milled graphite in preparation process. In addition, from the TG curve, the content of Si and the amorphous carbon is calculated to be 7.6 wt.% and 2.4 wt.%, respectively.

In consideration of the combined superiority of Si nanoparticle with high theoretical capacity and graphite with stable mechanical structure, the obtained Si/G/C microparticles are evaluated as anode materials for LIBs. Fig. 4a compares the initial charge/discharge profiles of the ball-milled graphite sheets, Si/G composite and Si/G/C microparticles at 0.2 C. The discharge capacities at first cycle of the graphite, Si/G composite and Si/G/C microparticles are 410.5, 848.3 and 763.4 mAh g-1, respectively. The decreased capacity of the Si/G/C microparticles compared with the Si/G composite could be attributed to the decreased Si content. The initial coulombic efficiency of Si/G composite and Si/G/C microparticles are 66% and 71%, respectively. The improved initial coulombic efficiency could be attributed to the decreased BET surface area and well coating with an amorphous carbon layer, which could prevent the electrolyte from infiltrating the inner of the composite and thus forming less SEI film.26 However, due to the irreversible formation of the SEI films in the first lithiation process, the initial coulombic efficiency is not met and should be further enhanced for industrial application. Generally, a prelithiation process is usually employed to enhance the initial coulombic efficiency. 27-28


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The CV curves of the Si/G/C microparticle at 0.1 mV s-1 for the first three cycles are shown in Fig. 4b. The peaks at 0.18 V in cathodic sweep and 0.49 V in anodic scan are assigned to the lithiation and delithiation process of the Si nanoparticles, respectively. The peaks at 0.01 V in cathodic sweep is attributed to the reversible lithium ion insertion into the graphite and alloying with Si, while the peak located at 0.19 V in anodic scan is assigned to the lithium ion extraction from the graphite.24, 29 All the peaks are reversible after first cycles. The CV results are also in agreement with the voltage platform in the Fig. 4a. The potential plateaus of the graphite and Si components are ranged from 0.25 to 0.01 V in discharge process. In the charge process, the voltage plateau of graphite is below 0.2 V, while the plateau of Si is located at round 0.45 V.

Fig. 4c and Fig. S4 (Supporting information) contrastively exhibit the cycling properties of the Si nanoparticle, ball-milled graphite, Si/G mixture and Si/G/C microparticles at a current density of 0.2 C. As shown in Fig. S4 (Supporting information), the pure Si nanoparticles present high discharge capacity of 3339 mA h g-1 at first discharge process. However, the capacity steeply decreases to 887 mA h g-1 after 70 cycles, with a capacity retention ratio of only 26%. The ball-milled graphite shows stable cycling capacity after first cycle, but delivers lower discharge capacity of 338.2 mA h g-1 after 100 cycles. The Si/G mixture exhibits enhanced discharge capacity of 848.3 mA h g-1 in the first cycle. However, the discharge capacity is also faded along with cycles. After mechanically pressed and coated with an amorphous carbon layer, the Si/G/C microparticles show more stable cycling performance in compared with the Si/G mixture. After 100 cycles, the discharge capacity maintains to 520.7 mA h g-1. The effect of different mechanical pressure on the cycling 9 ACS Paragon Plus Environment


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performance of the Si/G mixture is also studied. As displayed in Fig. S5 (Supporting information), as the pressure increased, the cycling performance shows relative enhancement.

Fig. 4d shows the rate charge/discharge performance of the Si/G/C microparticles at the gradient-enhanced current densities from 0.2 to 5 C. Average discharge capacities of 510.9, 446.1, and 390.7 mAh g-1 at current densities of 0.5, 1 and 2 C are delivered, respectively. Moreover, high capacity of 339.7 mAh g-1 at 5 C is also obtained. As the current density is reset to 0.2 C after 50 cycles, the discharge capacity can return to 546.5 mAh g-1, suggesting excellent capacity recovery ability. To further investigate the cycling behavior of the Si/G/C microparticles, the half-cell is cycled at 1 C for 800 cycles, as shown in Fig. 4e. It can be seen that the Si/G/C microparticles could maintain a capacity of about 370 mAh g-1, suggesting good cycling stability.

Furthermore, the full-cell performance of the Si/G/C microparticles is also evaluated. With Si/G/C microparticles as anode and commercial LiCoO2 as cathode, the full cell is cycled between 2.5 and 4.1 V based on the loading of cathode mass. After 50 cycles, the full cell can maintain a capacity of about 96.1 mAh g−1 at 0.5 C, with capacity retention of about 80% (Fig. 5a). The cycled full cell could also be able to light up a group of LEDs (Fig. 5b). Fig. 5c shows the charge/discharge curves of the full cell at current densities of 0.2, 0.4, 0.7 and 1 C, which exhibits that the practical working voltage range is larger than 3.1 V. As exhibited in Fig. 5d, the discharge capacities of 118.4, 110.3, 102.7 and 98.2 mAh g−1 can be maintained at 0.2 C after 6 cycles, 0.4 C after 11 cycles, 0.7 C after 16 cycles, and 1 C after 21 cycles, respectively. 10 ACS Paragon Plus Environment

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The EIS is employed to investigate the charge transport kinetics of the Si nanoparticle, graphite, Si/G composite and Si/G/C microparticles electrodes. The Nyquist plots before cycling (Fig. 6a, and Fig. S6, Supporting information) shows a semicircle in high frequency which represents the charge transfer resistance (Rct) on the electrode-electrolyte interface.30-32 As displayed in Fig. 6a and Table S1 (Supporting information), the Si nanoparticle electrode has the highest Rct impedance of 230 Ω. This value of Rct could be effectively decreased by mixing the Si nanoparticle into graphite due to the graphite electrode with lower Rct impedance of 68 Ω (Fig. S6, Supporting information). After mechanically pressed and coated with an amorphous carbon layer, the Si/G/C microparticles show decreased Rct impedance in compared with the Si/G mixture, suggesting that the amorphous carbon

layer

may

significantly

reduce

the

charge

transfer

resistance

on

the

electrode-electrolyte interface. As reported, the sloping line in the low-frequency region represents the lithium diffusion behavior into the electrode. As shown in Fig. 6b, the lower slope of the Si/G/C microparticles suggests the facile lithium diffusion kinetics within the electrode in comparison with the corresponding Si/G mixture as well as the pure Si nanoparticle.33-34

To further evaluate whether stable SEI film is formed or not, the Nyquist plots after 5 cycles at charge stage are given. The first semicircular in high-frequency region reflects the ohmic resistance of the SEI layer (Rf). As presented in Fig. 6c, the pure Si nanoparticle after 5 cycles exhibits an Rf value of 60 Ω, much higher than those of the Si/G mixture, which suggests the continuous formation of thick SEI film on the pure Si anode during cycling. In addition, the Si/G/C microparticles show almost overlapping plots after 10 cycles (Fig. 6d), 11 ACS Paragon Plus Environment


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indicating the formation of stable SEI layer on the outer surface of the microparticle, which is favor of good cycling performance and structural stability for the Si/G/C microparticle. This result is also confirmed by the SEM image of the cycled electrode as below.

To investigate the structural stability and volume change, the ex-situ SEM images of Si nanoparticle, graphite, Si/G composite and Si/G/C microparticles samples after 20 cycles are given. As for the Si nanoparticle and Si/G composite, the SEM images (Fig. 7a, b, e and f) show that the Si particles in the electrode are naked without any protection, which could result in cracks and aggregation caused by huge volume change in the discharge/charge process. Fig.7c and d exhibit the SEM images of the graphite electrode after 20 cycles. It can be seen that the surface maintains smooth and flat due to formation of stable SEI membrane. As for the Si/G/C microparticles, the low-resolution SEM image (Fig. 7g) exhibits that the microparticles are well maintained, further confirm that the good structure stability of the Si/G/C microparticles during cycling. In addition, the high-resolution SEM image (Fig. 7h) also presents smooth surface without crack, suggesting formation of stable SEI layer onto the surface of the Si/G/C microparticles, which implies that the Si nanoparticles are protected well into the graphite sheets and amorphous carbon layer.

Overall, the enhanced cycling performance of the Si/G/C microparticles in comparison with the corresponding Si/G mixture as well as the pure Si nanoparticles may be attributed to the good structural stability. After mechanically pressed, the Si nanoparticles are well embedded into the graphite sheets with stable framework, which is in favor of buffering the volume change of Si and keeping electrode integrity. Moreover, after coated with an 12 ACS Paragon Plus Environment

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amorphous carbon layer, the embedded Si nanoparticles are further protected with enhanced interfacial and structural structure, facilitating the improvement of coulombic efficiency and cycling properties. Finally, the graphite sheets and amorphous carbon layer are helpful for ionic and electronic transport during fast discharge/charge cycling.

Conclusions

In summary, we have developed a new approach to fabricate the Si/graphite composite for application in LIBs. By mechanical pressing, the Si nanoparticles are well embedded into the graphite sheets to produce the micro-scaled Si/G/C particles with high tap density. In addition, the amorphous carbon layer is also employed to further maintain the structure stability of the Si/G/C microparticles. As an anode material in LIBs, the obtained Si/G/C microparticles exhibit good rate capability with high capacity retention rate. The enhanced performance could be attributed to uniformly dispersive Si nanoparticles into graphite matrix, which give homogeneous lithiation/delithiation process. Furthermore, the coating of amorphous carbon layer could also stabilize the SEI film and maintain the integrity of the electrodes.

This

work

mainly

points

out

a

large-scale

solution

to

fabricate

Si-embedded/graphite composite for application in future LIBs.

ASSOCIATED CONTENT

Supporting Information. The supporting information is available free of charge via the Internet at http://pubs.acs.org.” Additional Experimental section, SEM images, TG curves, 13 ACS Paragon Plus Environment


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Electrochemical cycling performances of pure Si nanoparticle and Si/G mixture after different pressure, the Nyquist plots of the graphite and the fitted values of the EIS curves.

AUTHOR INFORMATION Corresponding Author * E-mail address: [email protected] (N. Lin).

ORCID Zheng Yi: 0000-0002-2197-9030 Ning Lin: 0000-0002-8029-5595

Notes Any additional relevant notes should be placed here.

ACKNOWLEDGMENT This work is financial supported by Anhui Provincial Natural Science Foundation (1608085MB22), China Postdoctoral Science Foundation funded project (Grant No. 2016M600484), the Fundamental Research Funds for the Central Universities (Grant No. WK2060190078), and the National Natural Science Fund of China (Grant No. 21701163).

REFERENCES 14 ACS Paragon Plus Environment

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1. Son, I. H.; Park, J. H.; Kwon, S.; Park, S.; Rummeli, M. H.; Bachmatiuk, A.; Song, H. J.; Ku, J.; Choi, J. W.; Choi, J. M.; Doo, S. G.; Chang, H., Silicon carbide-free graphene growth on silicon for lithium-ion battery with high volumetric energy density. Nat. Commun. 2015, 6. 7393, DOI 10.1038/ncomms8393. 2. Chang, J. B.; Huang, X. K.; Zhou, G. H.; Cui, S. M.; Hallac, P. B.; Jiang, J. W.; Hurley, P. T.; Chen, J. H., Multilayered Si Nanoparticle/Reduced Graphene Oxide Hybrid as a High-Performance Lithium-Ion Battery Anode. Adv. Mater. 2014, 26 (5), 758-764, DOI 10.1002/adma.201302757. 3. Jeong, M. G.; Du, H. L.; Islam, M.; Lee, J. K.; Sun, Y. K.; Jung, H. G., Self-Rearrangement of Silicon Nanoparticles Embedded in Micro Carbon Sphere Framework for High-Energy and Long-Life Lithium Ion Batteries. Nano Lett. 2017, 17 (9), 5600-5606, DOI 10.1021/acs.nanolett.7b02433. 4. Ling, L.; Ma, Y. T.; Xie, Q. S.; Wang, L. S.; Zhang, Q. F.; Peng, D. L., Copper-Nanoparticle-Induced Porous Si/Cu Composite Films as an Anode for Lithium Ion Batteries. Acs Nano 2017, 11 (7), 6893-6903, DOI 10.1021/acsnano.7b02030. 5. Liu, J. Y.; Li, N.; Goodman, M. D.; Zhang, H. G.; Epstein, E. S.; Huang, B.; Pan, Z.; Kim, J.; Choi, J. H.; Huang, X. J.; Liu, J. H.; Hsia, K. J.; Dillon, S. J.; Braun, P. V., Mechanically and Chemically Robust Sandwich-Structured C@Si@C Nanotube Array Li-Ion Battery Anodes. Acs Nano 2015, 9 (2), 1985-1994, DOI 10.1021/nn507003z. 6. Gao, H.; Xiao, L. S.; Plume, I.; Xu, G. L.; Ren, Y.; Zuo, X. B.; Liu, Y. Z.; Schulz, C.; Wiggers, H.; Amine, K.; Chen, Z. H., Parasitic Reactions in Nanosized Silicon Anodes for Lithium-Ion Batteries. Nano Lett. 2017, 17 (3), 1512-1519, DOI 10.1021/acs.nanolett.6b04551. 7. Lin, N.; Han, Y.; Zhou, J.; Zhang, K. L.; Xu, T. J.; Zhu, Y. C.; Qian, Y. T., A low temperature molten salt process for aluminothermic reduction of silicon oxides to crystalline Si for Li-ion batteries. Energ. Environ. Sci. 2015, 8 (11), 3187-3191, DOI 10.1039/C5EE02487K. 8. Yu, W. J.; Liu, C.; Hou, P. X.; Zhang, L.; Shan, X. Y.; Li, F.; Cheng, H. M., Lithiation of Silicon Nanoparticles Confined in Carbon Nanotubes. Acs Nano 2015, 9 (5), 5063-5071, DOI 10.1021/acsnano.5b00157. 9. Yao, Y.; McDowell, M. T.; Ryu, I.; Wu, H.; Liu, N. A.; Hu, L. B.; Nix, W. D.; Cui, Y., Interconnected Silicon Hollow Nanospheres for Lithium-Ion Battery Anodes with Long Cycle Life. Nano Lett. 2011, 11 (7), 2949-2954, DOI 10.1021/nl201470j. 10. Lin, N.; Han, Y.; Wang, L. B.; Zhou, J. B.; Zhou, J.; Zhu, Y. C.; Qian, Y. T., Preparation of Nanocrystalline Silicon from SiCl4 at 200 degrees C in Molten Salt for High-Performance Anodes for Lithium Ion Batteries. Angew. Chem., Int. Edit. 2015, 54 (12), 3822-3825, DOI 10.1002/ange.201411830. 11. Chen, Y. N.; Li, Y. J.; Wang, Y. B.; Fu, K.; Danner, V. A.; Dai, J. Q.; Lacey, S. D.; Yao, Y. G.; Hu, L. B., Rapid, in Situ Synthesis of High Capacity Battery Anodes through High Temperature Radiation-Based Thermal Shock. Nano Lett. 2016, 16 (9), 5553-5558, DOI 10.1021/acs.nanolett.6b02096. 12. Fei, H. L.; Peng, Z. W.; Li, L.; Yang, Y.; Lu, W.; Samuel, E. L. G.; Fan, X. J.; Tour, J. M., Preparation of carbon-coated iron oxide nanoparticles dispersed on graphene sheets and 15 ACS Paragon Plus Environment


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applications as advanced anode materials for lithium-ion batteries. Nano Res. 2014, 7(4), 502-510, DOI 10.1007/s12274-014-0416-0. 13. Zhou, X. S.; Cao, A. M.; Wan, L. J.; Guo, Y. G., Spin-Coated Silicon Nanoparticle/Graphene Electrode as a Binder-Free Anode for High-Performance Lithium-Ion Batteries. Nano Res. 2012, 5(12): 845-853, DOI 10.1007/s12274-012-0268-4. 14. Luo, J. Y.; Zhao, X.; Wu, J. S.; Jang, H. D.; Kung, H. H.; Huang, J. X., Crumpled Graphene-Encapsulated Si Nanoparticles for Lithium Ion Battery Anodes. J. Phys. Chem. Lett. 2012, 3 (13), 1824-1829, DOI 10.1021/jz3006892. 15. Su, J. M.; Zhao, J. Y.; Li, L. Y.; Zhang, C. C.; Chen, C. G.; Huang, T.; Yu, A. S., Three-Dimensional Porous Si and SiO2 with In Situ Decorated Carbon Nanotubes As Anode Materials for Li-ion Batteries. Acs Appl. Mater. Inter. 2017, 9 (21), 17807-17813, DOI 10.1021/acsami.6b16644. 16. Agyeman, D. A.; Song, K.; Lee, G. H.; Park, M.; Kang, Y. M., Carbon-Coated Si Nanoparticles Anchored between Reduced Graphene Oxides as an Extremely Reversible Anode Material for High Energy-Density Li-Ion Battery. Adv. Energy Mater. 2016, 6 (20) 1600904, DOI 10.1002/aenm.201600904. 17. Liang, G. M.; Qin, X. Y.; Zou, J. S.; Luo, L. Y.; Wang, Y. Z.; Wu, M. Y.; Zhu, H.; Chen, G. H.; Kang, F. Y.; Li, B. H., Electrosprayed silicon-embedded porous carbon microspheres as lithium-ion battery anodes with exceptional rate capacities. Carbon 2018, 127, 424-431, DOI 10.1016/j.carbon.2017.11.013. 18. Han, Y.; Zou, J.; Li, Z.; Wang, W.; Jie, Y.; Ma, J.; Tang, B.; Zhang, Q.; Cao, X.; Xu, S., Si@ void@ C Nanofibers Fabricated Using a Self-Powered Electrospinning System for Lithium-Ion Batteries. Acs Nano 2018,12(5), 4835-4843, DOI 10.1021/acsnano.8b01558. 19. Lin, N.; Xu, T. J.; Li, T. Q.; Han, Y.; Qian, Y. T., Controllable Self-Assembly of Micro-Nanostructured Si-Embedded Graphite/Graphene Composite Anode for High-Performance Li-Ion Batteries. Acs Appl. Mater. Inter. 2017, 9 (45), 39318-39325, DOI 10.1021/acsami.7b10639. 20. Ko, M.; Chae, S.; Ma, J.; Kim, N.; Lee, H. W.; Cui, Y.; Cho, J., Scalable synthesis of silicon-nanolayer-embedded graphite for high-energy lithium-ion batteries. Nat. Energy 2016, 1, 16113, DOI 10.1038/nenergy.2016.113. 21. Chae, S.; Kim, N.; Ma, J.; Cho, J.; Ko, M., One-to-One Comparison of Graphite-Blended Negative Electrodes Using Silicon Nanolayer-Embedded Graphite versus Commercial Benchmarking Materials for High-Energy Lithium-Ion Batteries. Adv. Energy Mater. 2017, 7 (15) 1700071, DOI 10.1002/aenm.201700071. 22. Xu, Q.; Li, J. Y.; Sun, J. K.; Yin, Y. X.; Wan, L. J.; Guo, Y. G., Watermelon-Inspired Si/C Microspheres with Hierarchical Buffer Structures for Densely Compacted Lithium-Ion Battery Anodes. Adv. Energy Mater. 2017, 7 (3) 1601481, DOI 10.1002/aenm.201601481. 23. Jo, Y. N.; Kim, Y.; Kim, J. S.; Song, J. H.; Kim, K. J.; Kwag, C. Y.; Lee, D. J.; Park, C. W.; Kim, Y. J., Si-graphite composites as anode materials for lithium secondary batteries. J. Power Sources 2010, 195 (18), 6031-6036, DOI 10.1016/j.jpowsour.2010.03.008. 24. Wang, Z. L.; Mao, Z. M.; Lai, L. F.; Okubo, M.; Song, Y. H.; Zhou, Y. J.; Liu, X.; Huang, W., Sub-micron silicon/pyrolyzed carbon@natural graphite self-assembly composite anode material for lithium-ion batteries. Chem. Eng. J. 2017, 313, 187-196, DOI 10.1016/j.cej.2016.12.072. 16 ACS Paragon Plus Environment

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25. Kim, S. Y.; Lee, J.; Kim, B. H.; Kim, Y. J.; Yang, K. S.; Park, M. S., Facile Synthesis of Carbon-Coated Silicon/Graphite Spherical Composites for High-Performance Lithium-Ion Batteries. Acs Appl. Mater. Inter. 2016, 8 (19), 12109-12117, DOI 10.1021/acsami.5b11628. 26. Luo, W.; Wang, Y. X.; Wang, L. J.; Jiang, W.; Chou, S. L.; Dou, S. X.; Liu, H. K.; Yang, J. P., Silicon/Mesoporous Carbon/Crystalline TiO2 Nanoparticles for Highly Stable Lithium Storage. Acs Nano 2016, 10 (11), 10524-10532, DOI 10.1021/acsnano.6b06517. 27. Yi, Z.; Lin, N.; Zhao, Y. Y.; Wang, W. W.; Qian, Y.; Zhu, Y. C.; Qian, Y. T., A flexible micro/nanostructured Si microsphere cross-linked by highly-elastic carbon nanotubes toward enhanced lithium ion battery anodes. Energy Storage Mater. 2018, DOI 10.1016/j.ensm.2018.07.025. 28. Li, X. L.; Gu, M.; Hu, S. Y.; Kennard, R.; Yan, P. F.; Chen, X. L.; Wang, C. M.; Sailor, M. J.; Zhang, J. G.; Liu, J., Mesoporous silicon sponge as an anti-pulverization structure for high-performance lithium-ion battery anodes. Nat. Commun. 2014, 5, 4105, DOI 10.1038/ncomms5105. 29. Li, M.; Hou, X. H.; Sha, Y. J.; Wang, J.; Hu, S. J.; Liu, X.; Shao, Z. P., Facile spray-drying/pyrolysis synthesis of core-shell structure graphite/silicon-porous carbon composite as a superior anode for Li-ion batteries. J. Power Sources 2014, 248, 721-728, DOI 10.1016/j.jpowsour.2013.10.012. 30. Ren, W. N.; Zhang, H. F.; Guan, C.; Cheng, C. W., Ultrathin MoS2 Nanosheets@Metal Organic Framework-Derived N-Doped Carbon Nanowall Arrays as Sodium Ion Battery Anode with Superior Cycling Life and Rate Capability. Adv. Funct. Mater. 2017, 27 (32) 1702116, DOI 10.1002/adfm.201702116. 31. Yi, Z.; Tian, X.; Han, Q.; Cheng, Y.; Lian, J. S.; Wu, Y. M.; Wang, L. M., One-step synthesis of Ni3Sn2@reduced graphene oxide composite with enhanced electrochemical lithium storage properties. Electrochim. Acta 2016, 192, 188-195, DOI 10.1016/j.electacta.2016.01.204. 32. Shi, L.; Wang, W. K.; Wang, A. B.; Yuan, K. G.; Jin, Z. Q.; Yang, Y. S., Si nanoparticles adhering to a nitrogen-rich porous carbon framework and its application as a lithium-ion battery anode material. J. Mater. Chem. A 2015, 3 (35), 18190-18197, DOI 10.1039/C5TA03974F. 33. Yi, Z.; Lin, N.; Xu, T. J.; Qian, Y. T., TiO2 Coated Si/C interconnected Microsphere with Stable Framework and Interface for High-Rate Lithium Storage. Chem. Eng. J. 2018, 347, 214-222, DOI 10.1016/j.cej.2018.04.101. 34. Wang, B. B.; Cai, S. B.; Wang, G.; Liu, X. J.; Wang, H.; Bai, J. T., Hierarchical NiCo2O4 nanosheets grown on hollow carbon microspheres composites for advanced lithium-ion half and full batteries. J. Colloid Interf. Sci. 2018, 513, 797-808, DOI 10.1016/j.jcis.2017.11.067.



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For Table of Contents Use Only

A mechanical pressing route is developed to large-scalely fabricate Si-embedded/graphite composite with increased tap density for using in lithium ion battery anodes.


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Fig. 1. (a) Schematically illustration of the fabrication process of the Si/G/C microparticles, (b) the schematically interpretation of the powder deformation in the pressing process, (c) the optical photograph of the milled Si/G mixture and the corresponding discs after mechanically pressed at 6 t, 12 t and 18 t, respectively, and (d) the optical photographs of the milled Si/G mixture and its pressed products at different pressures with equal weight in selfsame tubes for simple comparison of the loose bulk density, where the h0, h6, h12 and h18 are the height of the Si/G mixture and its pressed products at 6 t, 12 t and 18 t, respectively.



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Fig. 2. (a) The TEM image of Si nanoparticle, and the SEM images of the (b) ball-milled graphite, (c-d) Si/G mixture, (e-f) Si/G mixture after 18 t of pressure, and (g) Si/G/C microparticles, (h) the TEM image of the Si/G/C microparticles, the histogram of the particle size distribution of (i) Si nanoparticle, (j) ball-milled graphite, and (k) Si/G/C microparticles, and (l) the N2 adsorption/desorption isotherms of the Si nanoparticle, ball-milled graphite, Si/G mixture and Si/G/C microparticles.

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Fig. 3. (a) The XRD patterns and (b) Raman spectra of the Si nanoparticle, ball-milled graphite, Si/G mixture and Si/G/C microparticles.


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Fig. 4. Electrochemical performances of the ball-milled graphite, Si/G composite and Si/G/C microparticles for half-cell LIBs, (a) the first charge/discharge curves of the graphite, Si/G composite and Si/G/C microparticles at a current density of 0.2 C, (b) CV curves of Si/G/C microparticle at a scanning rate of 0.1 mV s−1, (c) charge/discharge cycling performances of graphite, Si/G composite and Si/G/C microparticles, (d) rate capacities of the Si/G/C microparticles at current density from 0.2 to 5 C, (e) galvanostatic charge/discharge capacity of the Si/G/C microparticles at current densities of 1 C for 800 cycles.


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Fig. 5. The electrochemical performance of the full cell with the Si/G/C microparticles as the anode and the LiCoO2 as the cathode. (a) The cycling performance at 0.5 C for 50 cycles, (b) the photograph of the full-cell lighting up a group of LEDs after cycled for 50 cycles, (c) discharge/charge profiles at 0.2, 0.4, 0.7 and 1.0 C, respectively, and (d) rate performances from 0.2 to 1.0 C.


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Fig. 6. (a) The Nyquist plots and the equivalent circuit model used for fitting of the Si nanoparticle, Si/G composite and Si/G/C microparticles in fresh state, (b) the corresponding liner fits (relationship between Z' and ω-1/2) in low-frequency region derived from Fig.6a, (c) the Nyquist plots of the Si nanoparticle, Si/G composite and Si/G/C microparticles after 5 cycles, and (d) the Nyquist plots of the Si/G/C microparticles after 5, 10, 15 and 20 cycles.


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Fig. 7. SEM image of (a-b) Si nanoparticle, (c-d) ball-milled graphite, (e-f) Si/G composite, and (g-h) Si/G/C microparticles after 20 cycles.


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Mechanical Pressing Route for Scalable Preparation of

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