DSpace https://erepo.uef.fi
Rinnakkaistallenteet Luonnontieteiden ja metsätieteiden tiedekunta
2020
Cascading use of barley husk ash to produce silicon for composite anodes of Li-ion batteries
Kalidas, N
Elsevier BV
Tieteelliset aikakauslehtiartikkelit
© Elsevier B.V.
CC BY-NC-ND https://creativecommons.org/licenses/by-nc-nd/4.0/
http://dx.doi.org/10.1016/j.matchemphys.2020.122736
https://erepo.uef.fi/handle/123456789/8082
Downloaded from University of Eastern Finland's eRepository
Journal Pre-proof
Cascading use of barley husk ash to produce silicon for composite anodes of Li-ion batteries
Nathiya Kalidas, Joakim Riikonen, Wujun Xu, Katja Lahtinen, Tanja Kallio, Vesa Pekka Lehto
PII: S0254-0584(20)30115-2
DOI: https://doi.org/10.1016/j.matchemphys.2020.122736 Reference: MAC 122736
To appear in: Materials Chemistry and Physics Received Date: 9 October 2019
Revised Date: 20 December 2019 Accepted Date: 28 January 2020
Please cite this article as: N. Kalidas, J. Riikonen, W. Xu, K. Lahtinen, T. Kallio, V.P. Lehto, Cascading use of barley husk ash to produce silicon for composite anodes of Li-ion batteries, Materials Chemistry and Physics (2020), doi: https://doi.org/10.1016/j.matchemphys.2020.122736.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2020 Published by Elsevier B.V.
Cascading use of barley husk ash to produce silicon for composite anodes of Li-ion batteries
Nathiya Kalidasa, Joakim Riikonena, Wujun Xua, Katja Lahtinenb, Tanja Kalliob, Vesa Pekka Lehtoa*
aDepartment of Applied Physics, University of Eastern Finland, Kuopio, Finland
bDepartment of Chemistry and Materials Science, Aalto University, Espoo, Finland
*Corresponding author: vesa-pekka.lehto@uef.fi
Abstract
Silicon is a promising alternative anode material for LIBs because it has ten times higher capacity than the currently used graphite giving the possibility to even double to capacity of the total battery cell. The high specific capacity is essential in the electric vehicles and portable electronic devices. However, silicon anodes are unstable during the charge/discharge cycles due to the large volume change of silicon leading to cracking of the silicon particles, which results in poor conductivity between the particles and unstable solid electrolyte interface layer. Mesoporous silicon structures can solve the stability issue and provide stable high capacity anodes for LIBs. In the present study, porous silicon anode material was prepared from barley husk ash, an agricultural residue. The production of the silicon material was carried out through a simple magnesiothermic reduction process, which is a cost- effective method compared with the conventional production method. To improve the performance of the biogenic silicon as the anode material, carbon nanotubes were conjugated on the particles to connect the particles to each other. The developed porous silicon composite delivered the average discharge capacity of 2049 mAh g-1 and 472 mAh g-1 at the rate of 0.1 C and 1 C, respectively.
1. Introduction
The demand of storing energy for electric vehicles and portable electronics is expected to grow quickly in the near future. To answer the demand, advanced lithium ion batteries (LIBs) with high energy and power density have been being intensively studied [1]. It is well known that battery performance is mainly depending on the type of the electrode materials used.
Graphite is commonly used as LIB anodes, but it is not optimal material for advanced LIBs because of its low capacity. To achieve higher energy and power density, higher capacity anodes are needed. Silicon is especially attractive anode materials for LIBs because it has the highest known theoretical capacity (3579 mAh g-1), 10 times higher than the capacity of graphite (372 mAh g-1) currently used as the anode [2]. Despite their high theoretical capacity, Si-based anodes suffer from rapid loss of capacity due to large volume changes (300%) of the material during charging and discharging of the battery. The strains generated during such expansion and contraction leads to pulverization of the electrode and to the loss of electrical contact in the anode. New solid electrolyte interface (SEI) formation occurs when the electrolyte reacts with fresh silicon and the unstable SEI layer on the electrode leads to rapid capacity fading. Thus, it is a challenge to achieve both excellent stability and enhanced capacity with the Si-based anode materials [3]. These issues have been addressed nowadays by various approaches and strategies. Nanocomposites [4], Si nanoparticles [5], nanowires [6], nanotubes [7], thin films [8], nanosheets [9], and porous Si [10] have been reported to accommodate the volume change without fracturing. Particularly, porous nanostructured Si has been recognized as an effective way to address the issue [11].
Several methods have been developed for synthesis of the porous silicon to be used in LIBs, but their feasibility is restricted by high raw materials cost, complicated production procedure and low production yield of the material. For example, nanostructured silicon is
produced by pyrolysis using high toxic and expensive silane precursors [12]. Hydrolysis of tetraethyl orthosilicate (TEOS) is used to produce SiO2 precursor, which, in turn, is reduced to silicon [13]. Mesoporous silicon (PSi) is conventionally produced through electrochemical etching of single crystal silicon wafers. However, because of the high price of silicon wafers, the porous material is expensive, and the process is slow and difficult to scale up. Therefore, it is imperative to develop a low-cost and simple process for the production of porous silicon using abundant and cheap sources. It has been recently reported that PSi for LIB silicon anodes can also be produced from beach sand [14], waste glass bottles [15] and from plant- based materials such as rice husks [16].
In the present study, barley husk ash was chosen as the raw material for PSi due to its low price, availability and sustainability. Barley husks is rich of phytoliths that are amorphous nanostructures of porous silica. Barley husk ash has a high content of nanostructured SiO2 (40 w-%). Phytoliths were reduced to silicon through magnesiothermic reduction after the purification step. Magnesiothermic reduction was carried out with different weight ratios of silica and magnesium while the heating rate and the reduction time was varied to optimize the material parameters. In order to enhance the electrical conductivity of PSi anode, carbon nanotubes (CNTs) were conjugated to the thermally carbonized surface of PSi (TCPSi) microparticles. The electrochemical performance of the different PSi grades and the TCPSi/CNT composite was studied.
2. Experimental method 2.1 Synthesis of porous silicon
Barley husk ash was obtained from Koskenkorva distillery (Altia Oyj), Finland. Ash is a residue from the power plant where barley husk is burned to produce energy. The ash has high content of nanostructured SiO2 (40 w-%) with inorganic impurities. For purification, barley husk ash (BHA) was added to 12 % HCl (Merck) at 100 oC in oil bath with
continuous stirring for 2 h. The mixture was filtered using vacuum filtration, washed with water and dried at 120 oC for 2 h. The dried sample was calcined in air at 600 oC for 16 h to obtain white silica powder. The calcined silica was mixed with magnesium (Sigma Aldrich, 99% purity) and NaCl (Fisher Scientific, analytical reagent grade) by milling the mixture with planetary ball mill with 400 rpm for 4 min. The ball milled sample was transferred into a quartz tube and kept in oven at 300 oC under N2 atmosphere for different heating rates and times (Table 1). The milled powder was slowly added to 200 ml of HCl (37%) at 70 °C for 1 h in oil bath with stirring and continues air flow. The mixture was filtered with vacuum filtration and washed with water to remove the NaCl. Sample was dried in an oven for 2 h at 65 oC. The dried sample was immersed into 5% HF solution for 10 min to dissolute the unreacted silica from the sample. The schematic representation of the synthesis protocol is shown in Fig. 1.
2.2 Preparation of thermally carbonized PSi (TCPSi)
Among the synthesized materials, the PSi-600-2 (Table 1) gave the best electrochemical performance based on the rate capability test. Therefore, the synthesized PSi-600-2 microparticles was taken for further modification, i.e., thermal carbonization. The surface of the silicon is reactive and will oxidize slowly in the presence of oxygen and moisture of the air. The oxidation will slowly change the properties of the material and thus the surface was stabilized with thermal carbonization to produce thin surface layer of Si-C. The outermost layer of Si-C consists of disordered graphitic carbon [11] that is beneficial for conductivity.
The BET surface area of thermally carbonized PSi was slightly increased but the porosity remained the same (Table 2). The PSi particles was dipped in hydrofluoric acid for 10 min to remove the surface oxides and dried in oven at 65 oC. To start the thermal hydrocarbonization, the particles were flushed with N2 for 30 min at room temperature and acetylene gas was purged for 15 min. The quart tube was transferred into a tube oven at 500
oC under nitrogen/acetylene (1/1 ratio) flow for 14.5 min. Acetylene gas flow was stopped
leaving the nitrogen to flow for 30 sec. The particles were cooled down to the room temperature. In the next step, thermal carbonization was started with nitrogen/acetylene gas flow for 9 min 40 sec at room temperature. Acetylene gas was closed, and flushing was continued with nitrogen for 20 sec. The quartz tube with particles was transferred into tube oven at 820 oC for 10 min. As the final step the quartz tube was taken out and cooled down to room temperature [11].
2.3 Functionalization of TCPSi-COOH and CNT-NH2
TCPSi-600-2 particles were immersed in undecylinic acid (UDA) at 120 oC for overnight. The sample was then washed with chloroform, NaOH, ethanol, water, 1 M HCl and ethanol one by one, and dried at 65 oC for 1 h. The obtained powder was denoted as TCPSi-COOH.
The carbon nanotubes (Timesnano) with the length and diameter of 5-30 µm and 0.14 nm, respectively, were used in the present study. The chemical oxidation of CNT was made in NH3-H2O/H2O2/H2O with 1/1/5 ratio at 85 oC for 20 min and then in HCl/H2O2/H2O with 1/1/6 ratio for 5 min. Amine group functionalization was carried out with iso-propyl alcohol (IPA) and 3-aminopropyl-triethoxysilane (APTES, Sigma Aldrich) for 20 min at room temperature under N2 atmosphere. Then, the particles were stirred for 4 h at 65 oC and the mixture was centrifuged and washed three times with ethanol and dried at 65 oC for 1 h. The obtained powder was denoted as CNT-CH2.
2.4 TCPSi-CNT conjugation
CNT-NH2 (0.02 g) was dispersed in 200 ml of ethanol and sonicated for 1 h using tip sonicator (Hielscher UPS400S). In the next step, 0.44 g of N-hydroxysuccimide was dissolved in ethanol and added in the sonicated dispersion. In the third step, 34.64 mg of EDAC (1-ethyl-3-dimethylaminopropyl carboimide) was mixed with ethanol and added in the CNT-NH2 dispersion. Again, the dispersion was sonicated for 1 h. In the final step, 0.48g of TCPSi-COOH (PSi-600-2) was added and sonicated for 2 min. The TCPSi-CNT
dispersion was then centrifuged, washed with ethanol and dried. The conjugated TCPSi- CNT-600-2 sample was collected for further characterization.
2.5 Material characterization
The crystalline phase of the synthesized PSi samples was investigated with X-ray powder diffraction (Bruker D8) using CuKα radiation (λ =1.54 nm). The diffractrograms were measured with Bragg-Brentano geometry from 20 to 90 o (2θ). The specific surface area and pore sizes were measured with N2 sorption at 77 K (Micromeritics Tristar II 3020). The surface area was calculated using the Brunauer-Emmet-Teller (BET) theory and the pore size distribution was defined with the Barrett-Joyner-Halenda (BJH) theory from the desorption branch. The surface morphology and porous structure was observed with scanning electron microscopy (SEM Zeiss Sigma HD VP) and transmission electron microscope (TEM; JEOL, JEM-2100F). The elemental analysis was done with X-ray energy-dispersive spectroscopy (EDS) integrated with SEM. The acceleration voltage of 20 kV was used to study the elemental composition of the materials. Raman spectroscopy (Thermo DXR2xi) study was performed using 532 nm laser. FTIR spectroscopy (ATR-diamond technique) with transmission mode (Thermo Nicolet iS50). X-ray photoelectron spectroscopy (XPS Kratos Axis Ultra system, with a monochromatic Al Kα X-ray source of 1486.6 eV, 40 eV energy) were used to characterize the surface oxide content of porous silicon. High-resolution spectra of Si 2p peaks were calibrated with reference of O1s. The surface was measured after 2 min sputtering with 5 keV Ar+ ions. All the XPS measurements were performed with 200 µm analysis area.
2.6 Electrode preparation and electrochemical studies
The electrodes were prepared through slurry casting with a mixture of 60 wt.% active material (synthesized PSi or the composite TCPSi/CNT material), 10 wt.% of carboxymethyl
cellulose (CMC, Sigma Aldrich) and 10 wt.% of polyacrylic acid (PAA, Sigma Aldrich) binders, and 20 wt.% of Super carbon black (C65, Timcal). CMC is a water-soluble binder and it has a linear polymeric derivative of natural cellulose. PAA binder forms the cross‐
linked structure through the condensation reaction with CMC, which results in a three- dimensional interconnected network. It gives better adherence to silicon particles and accommodates the volume changes. Therefore, the combination of 10 wt% sodium carboxymethyl cellulose (Na-CMC) and 10 wt% PAA was used as a binder in this study. The binders were dissolved in deionized water which after carbon black and the active material were added and mixed until homogenous slurry was obtained. The slurry was coated onto a copper foil using a slurry coating machine (T-Max) and the electrode was dried under vacuum at 150 oC for 2 hrs. The electrode disks (14 mm in diameter) were punched out and dried in a vacuum oven at 110 oC overnight. The punched electrodes were moved to the glove box for the construction of the half-cells. The cells were assembled in the argon filled glove box (Tacomex) with the O2 and H2O level less than 1 ppm. Lithium metal foil (Sigma- Aldrich) was used as the reference and the counter electrode. A glass fiber membrane (Whatman GF/A, 260 µ m thick) was used as the separator. 1 M LiPF6 dissolved in (1:1 v/v) EC:DMC solvent (Merck) was used as the electrolyte.
Electrochemical characterization was performed using split type and 2016 coin cells. The mass loading of the electrodes varied between 1 - 1.4 mg cm-2. The rate tests were carried out galvanostatically at different current rates from 0.01 – 2.0 V (vs Li/Li+) in Neware battery system. Cyclic voltammetry (CV) was performed on Biologic BCS-805 battery cycler with the split type Swagelok cells in the potential window 0.01 - 2 V at the scan rate of 0.1 mV.
The electrochemical impedance spectroscopy (EIS) of constructed cells were performed with Biologic SP-150 potentiostat in the frequency range of 500 kHz to 100 MHz with the amplitude of 10 mV.
3. Results and Discussion 3.1. Structural characterization
The phase purity and crystal structure were analyzed with X-ray powder diffraction (Fig.
2a). The diffractogram of the barley husk ash shows the presence of several inorganic compounds. The calcined silica shows a broad peak, which confirms the amorphous structure of SiO2. All identified peaks of the synthesized PSi samples are perfectly matching with the cubic structure of silicon (JCPDS file No-00-27-1402). The minor impurity peaks of Na2SiF6
were observed in the samples of PSi-600-2 and PSi-50-2. The impurity was due to the reaction taking place between NaCl and H2SiF6 during the dissolution of SiO2 in HF [17].
The average crystallite sizes were calculated using Scherrer’s formula (Table 2) [18].
The porous structure of PSi material was characterized with N2 sorption studies. The BET surface area (A) was calculated based on the monolayer adsorption of N2 at low pressure (P/P0 < 0.3). All synthesized PSi materials exhibited typical IV type nitrogen isotherms with H2 hysteresis loops in the range of 0.5–1.0 P/P0, which is characteristic for mesoporous materials (Fig. 2b) [19]. The pore size distribution curves of the synthesized porous silicon samples in the range of 2 - 50 nm are shown in Fig. S1. The pore volume (Vp) was calculated from a single point at P/P0 = 0.98, and the average pore size (Dp) was calculated from the equation Dp = 4Vp/A. The pores size distribution The BET surface area, pore volume, average pore size and porosity of the synthesized PSi samples are given in Table 2.
Surface morphology and porous structure of the silica and PSi samples were evaluated with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The calcined SiO2 powder displays a highly irregular-shape morphology with porous structure (Fig. 3,). After the magnesiothermic reduction process, the PSi samples showed agglomerated Si particles that contained porous structure (Fig. S2). Based on EDS, the silica calcined from barley husk ash was about 93 wt.% of SiO2 with 7 wt.% of impurities like Ca, K, Na and Al.
The final product of silicon contains only small amounts of F, Na and Mg as impurities
(Table 3) that are originating mainly from the chemicals used in the synthesis. The similar impurities were present in the silicon material reported previously [14]. The metallic impurities like Na and Mg can increase the conductivity of silicon.
Raman spectra confirmed the elemental silicon and surface oxides in the PSi samples (Fig. 4a). The samples showed peaks at 517 cm−1 related to Si-Si stretching mode of crystalline Si. The peak slightly shifted to 517 cm−1 compared with bulk silicon wafer (520 cm-1) due to size of PSi particles [20]. The broad peaks at 300 cm-1 confirmed the presence of amorphous silicon oxides on silicon surface (Fig. S3) [21].
The X-ray photoelectron spectra (XPS) showed peaks appearing around 99.8 and 103.5 eV, which are assigned primarily to Si-Si and Si-O bonds, respectively (Fig. 4b). The XPS spectra of the high-resolution Si2p region shows two peaks where the lower binding energy (99.8 eV) is associated with Si0 and the higher binding energy (103.5 eV) is associated with silicon dioxide (Si4+) [22]. PSi contains the Si phase with a trace of the SiO2 phase origination from the native oxidation of the silicon surface. XPS is very surface sensitive method the analyzing depth being 1 – 10 nm [23]. The silicon dioxide peak of the samples PSi-300-6 and PSi-50-2 showed higher intensity compared with the Si0 peak, which confirms the presence of dense surface oxide layer. The amorphous SiO2 layer was formed on the silicon surface in the presence of air and humidity at room temperature even though the synthesized PSi samples were stored in a desiccator in dry air before the measurements. The deconvolution of the Si2p core level peak shows three curves having the peak positions at 103.5 (Si4+), 100.5 (Si1+) and 99.8 eV (Si0). The atomic concentration (at.%) of elemental silicon and silicon oxides are summarized in Table 4. The XPS result indicates that elemental Si content of PSi-600-2 (43 at. %) is higher than that of the other PSi samples, which is beneficial for improving the electrochemical performance. The variations in the Si2p3/2 peak position (ca. 99 eV) were due to the binding energy calibration as the XPS spectra were calibrated with the reference of the O1s peak at 532.9 eV.
3.2 Electrochemical characterization
Cyclic voltammetry curves of PSi electrodes were conducted in the voltage range of 0.01 - 2.0 V (vs. Li+/Li) at the scan rate of 0.1 mVs-1 (Fig. 5a). During the first lithiation cycle, peaks were observed at 0.95 and 0.90 V for PSi-600-2 and PSi-300-2, respectively, which were attributed to the formation of SEI layer due to electrolyte decomposition (Fig. 5a, insert) [24]. The SEI peaks were not observed in PSi-600-2 and PSi-50-2, which indicates that the surface oxide layer covers the active surface of silicon. The amorphous SiO2 surface on PSi particles reacts with lithium forming Li4SiO4 at the end of the first lithiation, but the product is chemically stable and electrochemically inactive. The stability of Li4SiO4 can enhance the diffusion of lithium ions into the active silicon [25]. The increase in the peak intensity is attributed to the active crystalline PSi particles that gradually reacts with lithium during the repeated lithiation/delithiation cycles. Therefore, the increasing peak intensity was attributed to the progress of the activation process. The obtained CV behavior is in good agreement with the results reported previously [26]. Lithiation/de-lithiation peaks intensity of PSi-600-2 was gradually increased from 1st cycle to 10th cycles due to the activation of PSi. Lithiation peak at 0.18 V corresponds to conversion of crystalline Si to LixSi alloy (Fig. 5b). During delithiation, the two peaks observed at 0.36 and 0.53 V were related to conversion of LixSi to silicon [24]. The peak intensity increased from 2nd to 10th cycle indicating the progress of Si activation. The lithiated and delithiated peaks position are maintained at the end of the 10 CV cycles, PSi-600-2 electrode was completely activated exhibiting excellent cycling reversibility and structural stability of the electrodes.
The electrochemical performance of the PSi anodes was evaluated with the rate capability tests performed at controlled room temperature of 22 oC with the C-rates of 0.03, 0.1, 0.2, 0.5, 1 C and again with 0.1 C to demonstrate the capacity retention behavior (Fig. 6).
The first 3 formation cycles were done at very low current rate of 0.02, 0.03 and 0.05 C. The PSi-600-2 delivered 712, 588, 384 and 216 mAh g-1 at 0.1, 0.2, 0.5 and 1 C, respectively. The
average capacity value of 216 mAh g-1 at 1C rate was significantly higher than for the other PSi samples (Table S1). Therefore, the native surface oxides in the PSi samples played a significant role in the rate performance. PSi-600-2 showed lower oxide content than other PSi samples, which was evidenced with the XPS results. The surface oxide layer in PSi-600-2 was acting as a passivation layer for the electrode and it was beneficial for enhanced reversible capacity. If the surface oxide layer is too thick layer, then it will be act as insulating layer, which hinders the Li transfer into core silicon. Therefore, the rate test results indicated that the surface oxide layer have a negative effect and it limits the capacity of PSi anodes [27]. The rate test with PSi-600-2 was better than with the other PSi samples, because of the thin but dense oxide layer and the high silicon content. The oxide layer converted to more stable silicate forms (Li4SiO4) during cycling, which results in the improved electrochemical performance.
To improve the electrochemical behavior of the PSi-600-2 sample, it was conjugated with carbon nanotubes to form TCPSi/CNT composite. The Raman peaks at 517, 1354 and 1584 cm-1 were observed corresponding to Si and to the D and G band of carbon, respectively. This confirms the presence of CNT in TCPSi/CNT composite (Fig. 7a) [28].
FTIR-ATR spectrum indicated an amide bond in the form of C=O stretch at 1690 cm-1, which confirms the conjugation of TCPSi with CNT (Fig. 7b). The BET surface area, pore volume, and average pore size are given in Table 2, calculated from N2 sorption isotherm (Fig. 7c).
The material showed higher BET surface area than bare PSi (95 m2 g−1), which is due to the presence of CNT. The carbon nanotubes are identified in SEM images (Fig. 7d). In the magnified SEM image, it can be seen that CNTs are well attached to the surface of TCPSi particles (Fig. 7e). The cycling performance of the PSi 600-2 and TCPSi-CNT 600-2 samples at 0.2 C rate for 50 cycles are shown in Fig. S4. To activate the silicon materials sufficiently, a relatively low rate of 0.1 C was used to conduct the first three cycles. The initial specific capacities of PSi 600-2 and TCPSi-CNT 600-2 were 839 and 1213 mAh g-1, respectively, and
the final capacities were 333 and 770 mAh g-1 after 50 cycles. The TCPSi/CNT composite anode delivered the reversible average capacities of 2049, 1698, 1054 and 472 mAh g-1 with 0.1, 0.2, 0.5 and 1 C (Table S1), respectively, indicating that the addition of CNT significantly improves the rate performance of the PSi-600-2 (Fig. 8a). When the current rate was reduced back to 0.1C, the average capacity recovered up to 1848 mAh g-1. Thus, the TCPSi/CNT composite enhanced the conductivity and alleviated the adverse effects of the expansion/contraction of silicon particles during the charge/discharge process.
Electrochemical impedance spectra (EIS) results of the PSi-600-2 and TCPSi/CNT-600-2 electrodes are shown in Fig. 8b. The EIS spectra showed one semicircle followed by a line with steep positive slope. The equivalent circuit consists of the ohmic resistance R1, charge transfer resistance R2, one constant phase element of Q2, Warburg impedance W [29]. The R1 and R2 for TCPSi/CNT (2.4 Ω, 35 Ω) was smaller than for the electrode without CNTs (3.7 Ω, 85 Ω). The R2 value differences in the materials are related to the electrical conductivity of the materials. As a result, CNTs decreases the impedance and provides better path for Li-ion diffusion.
4. Conclusions
Mesoporous silicon with different material characteristics were successfully prepared from barley husk ash with magnesiothermic reduction. Using bio-based ash as the raw material for the high-tech nanomaterial follows ideally the cascading principle and pushes the material manufacturing process towards sustainability. The porosities of the synthesized materials were around 48% which value has been considered optimal for mesoporous silicon in LIB anodes. The best electrochemical performance was obtained with the sample showing a dense but thin surface oxide layer which acts as a protective layer yet allowing the intercalation of lithium. On the other hand, the thick oxide layer acted as an insulating layer on mesoporous silicon samples, which decreased the reversible capacity. The conjugation of
mesoporous silicon with CNTs improved the performance and provided excellent rate capability results. CNTs increased the electrical conductivity and lithium ion diffusion in electrodes. As a result, the composite of mesoporous silicon and CNTs offered a high average discharge capacity of 2049 mAh g-1 at the rate of 0.1C and delivered a good rate performance with the capacity of 472 mAh g-1 at 1C. The barley husk ash is a good option to prepare porous silicon materials for LIB anodes.
5. Acknowledgments
The authors acknowledge Academy of Finland (projects #325495 and #292601) and EDUFI fellowship for the financial support. The authors are thankful to Altia Oy for providing barley husk ash for the studies. The authors are thankful to Jouko Lahtinen for the XPS measurement, Aalto University.
References
[1] N. Nitta, F. Wu, J.T. Lee, G. Yushin, Li-ion battery materials: present and future, Mater.
Today 18 (2015) 252-264.
[2] F. Luo, B. Liu, J. Zheng, G. Chu, K. Zhong, H. Li, X. Huang, Review—Nano- Silicon/Carbon Composite Anode Materials Towards Practical Application for Next Generation Li-Ion Batteries, J. Electrochem. Soc. 162 (2015) A2509-A2528.
[3] X. Zuo, J. Zhu, P.M. Buschbaum, Y.J. Cheng, Silicon based lithium-ion battery anodes: a chronicle perspective review, Nano Energy 31 (2017) 113-143.
[4] R. Zhang, Y. Du, D. Li, D. Shen, J. Yang, Z. Guo, H.K. Liu, A.A. Elzatahry, D. Zhao, Highly Reversible and Large Lithium Storage in Mesoporous Si/C Nanocomposite Anodes with Silicon Nanoparticles Embedded in a Carbon Framework, Adv. Mater. 26 (2014) 6749-6755.
[5] L. Sun, T.T. Su, L. Xu, H.B. Du, Preparation of uniform Si nanoparticles for high- performance Li-ion battery anodes, Phys. Chem. Chem. Phys. 18 (2016) 1521-1525.
[6] Y.F. Dong, T .Slade, M.J. Stolt, L.S. Li, S.N. Girard, L.Q. Mai, S. Jin, Low temperature molten salt production of silicon nanowires by electrochemical reduction of CaSiO3, Angew. Chem. Int. Ed. 56 (2017) 14453-14457.
[7] T.T. Alexander, G-R. Roberto, L.C. Jeffery, D. Thierry, Self-Supported Silicon Nanotube Arrays as an Anode Electrode for Li-Ion Batteries, ECS Trans. 77(11) (2017) 349-350.
[8] S. Mohammed, M. Peter, H .Colin, F. Candice, K. Robert, F. Manrico, Pure silicon thin- film anodes for lithium-ion batteries: A review, J. Power Sources 414 (2019) 48-67.
[9] J. Ryu, D. Hong, S. Choi, S. Park, Synthesis of ultrathin Si nanosheets from natural clays for lithium-ion battery anodes, ACS Nano 10 (2016) 2843-2851.
[10] X. Liu, H. Li, T. Zhai, H. Zhou, Hierarchical micro/nano porous silicon Li-ion battery anodes, Chem. Commun. 48 (2012) 5079-5081.
[11] T. Ikonen, T. Nissinen, E. Pohjalainen, O. Sorsa, T. Kallio, V.P. Lehto, Electrochemically anodized porous silicon: Towards simple and affordable anode material for Li-ion batteries, Sci. Rep. 7 (2017) (7880) 1-8.
[12] J. Sisi, H. Bin, S. Ritu, Z. Linghong, L. Haihua, Z. Lu, L. Wenquan, Z. Bin, Z.
Zhengcheng, Surface Functionalized Silicon Nanoparticles as Anode Material for Lithium-Ion Battery, ACS Appl. Mater. Interfaces 1051 (2018) 44924-44931.
[13] E. Dingsoyr, A. Christy, Effect of reaction variables on the formation of silica particles by hydrolysis of tetraethyl orthosilicate using sodium hydroxide as a basic catalyst, Surf.
Colloid Sci. 116 (2001) 67-73.
[14] Z. Favors, W. Wang, H. Hosseini Bay, Z. Mutlu, K. Ahmed, C. Liu, M. Ozkan, C.S.
Ozkan, Scalable synthesis of nano-silicon from beach sand for long cycle life Li-ion batteries, Sci. Rep. 4 (2014) 5623 1-7.
[15] C. Li, C. Liu, W. Wang, Z. Mutlu, J. Bell, R. Ahmed, M. Ozkan, C.S. Ozkan, Silicon Derived from glass bottles as anode materials for lithium ion full cell batteries, Sci. Rep.
7 (2017) 917 1-8.
[16] N. Liu, K. Huo, M.T. McDowell, J. Zhao, Y. Cui, Rice husks as a sustainable source of nanostructured silicon for high performance Li-ion battery anodes, Sci. Rep. 3 (2013) (1919) 1-7.
[17] H. Park‐ J.H. Cho, J.H. Jung, P.P.D.A Huy, T. Le, J. Yi, A Review of Wet Chemical Etching of Glasses in Hydrofluoric Acid based Solution for Thin Film Silicon Solar Cell Application Current Photovoltaic Research 5(3) (2017) 75-82.
[18] A. Monshi, M.R. Foroughi, M R. Monsh, Modified Scherrer Equation to Estimate More Accurately Nano-Crystallite Size Using XRD, World J. Nano Sci. and Engg. 2 (2012) 154-160.
[19] L. Shi, W. Wang, A. Wang, K. Yuan, Y. Yang, Understanding the impact mechanism of the thermal effect on the porous silicon anode material preparation via magnesiothermic reduction, J. Alloys Compd. 661 (2016) 27-37.
[20] R. Wang, G. Zhou, Y. Liu, S. Pan, H. Zhang, D. Yu, Z. Zhang, Raman spectral study of silicon nanowires: high-order scattering and phonon confinement effects, Phys. Rev. B 61 (2000) 16827-16832.
[21] D. Fang, Z. Jiantao, Y. Ran, G. Mikhail, S. Hiesang, C. Shuru, W. Donghai, Bottom-up synthesis of high surface area mesoporous crystalline silicon and evaluation of its hydrogen evolution performance, Nature Comm. 5 (2014) 3605 1-11.
[22] B. Jiang, S. Zeng, H. Wang, D. Liu, J. Qian, Y. Cao, H. Yang, X. Ai, Dual Core−Shell structured si@siox@c nanocomposite synthesized via a one-step pyrolysis method as a
highly stable anode material for lithium-ion batteries, ACS Appl. Mater. Interfaces 8 (2016) 31611-31616.
[23] Y. Yang, H.Z. Li, J. Liu, Z.Q. Sun, S.S. Tang, M. Lei, Dual yolk-shell structure of carbon and silica-coated silicon for high performance lithium-ion batteries, Sci. Rep. 5 (2015) 10908 1-9.
[24] J.C. Vickerman, I.S. Gilmore, Surface Analysis, The Principal Techniques, second edition, 2009.
[25] M.A. Al-Maghrabi, J. Suzuki, R.J. Sanderson, V.L. Chevrier, R.A. Dunlap, J.R. Dahn, Combinatorial Studies of Si1−xOx as a Potential Negative Electrode Material for Li-Ion Battery Applications, J. Electrochem. Soc. 160 (9) (2013) A1587-A1593.
[26] Z. Favors, H.H. Bay, Z. Mutlu, K. Ahmed, R. Ionescu, R. Ye, M. Ozkan, C.S. Ozkan, Towards Scalable Binderless Electrodes: Carbon Coated Silicon Nanofiber Paper via Mg Reduction of Electrospun SiO2 Nanofibers, Sci. Rep. 5 (2015) (8246) 1-7.
[27] S. Xun, X. Song, L. Wang, M.E. Grass, Z. Liu, V.S. Battaglia, G. Liu, The Effects of Native Oxide Surface Layer on the Electrochemical Performance of Si Nanoparticle- Based Electrodes, J. Electrochem. Soc. 158 (12) (2011) A1260-A1266.
[28] T. Mu, P. Zuo, S. Lou, Q. Pan, H. Zhang, C. Du, Y. Gao, X. Cheng, Y. Ma, H. Huo, G.
Yin, A three-dimensional silicon/nitrogen-doped graphitized carbon composite as high- performance anode material for lithium ion batteries,J. Alloys Compd. 777 (2019) 190- 197.
[29] J.K. Feng, Z. Zhang, L.J. Ci, W. Zhai, Q. Ai, S.L. Xiong, Chemical Dealloying Synthesis of Porous Silicon Anchored by in Situ Generated Graphene Sheets as Anode Material for Lithium-Ion Batteries, J. Power Sources 287 (2015) 177-183.
Figures
Fig. 1. Schematic representation of the synthesis of porous silicon and the TCPSi/CNT composite with magnesiothermic reduction from barley husk ash.
a)
b)
Fig. 2. a) XRPD diffractrograms and b) Nitrogen sorption isotherm of the synthesized porous silicon materials from barley husk ash.
Fig. 3. SEM images of the purified silica and the synthesized PSi samples from barley husk ash.
Calcined silica
Calcined silica
Fig. 4. a) Raman spectra and b) high-resolution XPS spectra of Si2p of the porous silicon samples produced from barley husk ash.
surface oxide
517 cm-1
520 cm-1
a)
b)
Fig. 5. Cyclic Voltammogram of a) comparison of 1st and 10th CV cycles of PSi anodes b) PSi-600-2 anodes (10 CV cycles) at scan rate 0.1 mV/sec in the voltage range 0.02-2.0 V.
b)
a)
Fig. 6. Rate test of porous silicon anodes performed at different current rate.
Fig. 7. a) Raman spectra b) ATR c) N2 sorption isotherm d) SEM image and e) magnified SEM image of TCPSi/CNT composite.
a) b) c)
d) e)
Fig. 8. a) Rate test performed with different current rates and b) Nyquist plots for the cells of PSi-600-2 and TCPSi/CNT-600-2 anodes. Inset: Equivalent circuit for the
Nyquist plots.
0.1 C
0.2 C
0.5 C
1 C
0.1 C
a)
b)
Tables
Table. 1 Synthesis parameters for magnesiothermic reduction to optimize the material parameters.
Sample code
Total mass SiO2 (g)
Mass ratio (SiO2:Mg:NaCl)
Rate of heating (oC/h)
Reduction time (h)
PSi-300-2 4 1:0.8:10 300 2
PSi-300-6 4 1:0.8:10 300 6
PSi-50-2 1 1:0.8:20 50 2
PSi-600-2 10 1:0.8:10 600 2
Table 2. Pore size, pore volume and surface area of PSi samples with N2 sorption studies.
Sample code Average crystallite
size (nm)
BET Specifica surface area
(m2/g)
Specific porea volume (cm3/g)
Average porea diameter
(nm)
Porosity* (%)
PSi-300-2 33 152 ± 7 0.46 ± 0.10 12 ± 3 52
PSi-300-6 33 154 ± 8 0.41 ± 0.05 11 ± 4 49
PSi-50-2 31 114 ± 4 0.35 ± 0.08 11 ± 6 45
PSi-600-2 32 95 ± 5 0.39 ± 0.03 15 ± 2 48
TCPSi-600-2 97 ± 2 0.39 ± 0.04 12 ± 2 48
TCPSi/CNT
-600-2 102 ± 1 0.40 ± 0.01 11 ± 1 48
aValues are averages ± standard deviation, n=3
*Porosity (%) calculated from formula [(VP/VT) *100]
VP is pore volume, VT is total pore volume (VT = Vp +1/ρSi) where ρSi is density of Si (2.33 g cm-3).
Table 3. Elemental composition of the PSi samples based on the EDS analysis.
(wt.%) - weight percentage are averages ± standard deviation, n=3 Element PSi-300-2
(wt.%)
PSi-300-6 (wt.%)
PSi-50-2 (wt.%)
PSi-600-2 (wt.%) Si 87.2 ± 0.5 88.0 ± 1.4 88.0 ± 1.4 88.3 ± 0.6 Mg 0.9 ± 0.2 0.5 ± 0.0 1.1± 0.2 1.0 ± 0.1
Na 1.2 ± 0.5 0.5 ± 0.2 1.2± 0.3 0.9 ± 0.2 O 8.2 ± 0.5 9.8 ± 1.0 6.9 ± 0.2 7.2 ± 0.4 F 2.5 ± 0.3 1.2 ± 0.2 2.8± 0.2 2.6 ± 0.2
Table 4. Atomic concentrations of silicon and silicon oxides obtained from the XPS analysis.
Element PSi-300-2 (at.%)
PSi-300-6 (at.%)
PSi-50-2 (at.%)
PSi-600-2 (at.%)
Si 31 18 16 43
SiOx (+1) 10 8 7 11
SiO2 59 74 77 46
Barley husk ash served as new raw material for porous silicon LIB anodes Magnesiothermic reduction method was used to synthesize mesoporous silicon
CNTs were conjugated with mesoporous silicon to improve the electrical conductivity The composite anode enhanced essentially the rate capability performance
☒The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
