The Preparation And Electrochemical Performance Analysis of Different Porous Silicon Composites

doi:10.21203/rs.3.rs-872343/v1

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The Preparation And Electrochemical Performance Analysis of Different Porous Silicon Composites

https://doi.org/10.21203/rs.3.rs-872343/v1

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In this work, LiAlH₄ is used to reduce SiO₂ to porous silicon, and then nano-silver (AgNPs) and Li₂CO₃are attached to porous silicon substrate to form different porous silicon composites. X-ray diffraction (XRD) and scanning electron microscopy (SEM) are applied to characterize the morphology of porous silicon composites, and porous silicon composites are tested via electrochemical techniques. The experimental results present that porous silicon composites loaded with AgNPs (Si-Ag) show higher specific capacity (476.0195 mA·h·g^-1) and lower interfacial impedance compared with composites loaded with Li₂CO₃ (Si-Li₂CO₃). Si-Ag composites are suitable to be used as anode materials for lithium-ion batteries.

Electronic Materials and Devices

Porous silicon

Porous silicon composites

AgNPs

Lithium-ion battery

Lithium-ion batteries have the advantages of high temperature, high capacity and low voltage of traditional batteries, and also possess the merits of long service life and excellent performance, which endow lithium-ion batteries wide applications such as mobile electronic equipment, new energy vehicles, space technology and defense industry [1–2]. Recently, lots of novel lithium-ion batteries are being developed with the in-depth study of battery composite materials. Anode materials still occupies a large market proportion in main material of the lithium-ion battery. At present, graphite is the most widely used anode material in lithium-ion battery, but the theoretical specific capacity (372 mAh/g) of it is low, which will limit energy storage and fail to meet the increasing demand for high energy of products [3–4]. Therefore, it is necessary to develop a novel anode material.

Silicon-based materials have become the research focus of anode materials for lithium-ion batteries due to the advantages of high theoretical specific capacity (4200mAh/g), low charging and discharging platform, easy modification of nanostructures and the ability to form metal silicide with many metal elements [5–8]. Silicon-based composite material shows a superior performance and application prospect, especially the alloying of cathode material in lithium-ion battery which not only endows lithium-ion battery the high conductivity, also overcomes the problem of silicon volume expansion in the process of charging and discharging. The electrochemical properties of lithium-ion battery are greatly improved via silicon-based anode materials [9–11].

Inspired by previous studies, the generation of porous silicon was based on the reduction of LiAlH₄ which served as a substrate of nano-silver (AgNPs) and Li₂CO₃ to prepare the porous silicon composites (Si-Ag, Si- Li₂CO₃ and Si-Ag-Li₂CO₃) in this paper. The morphology of porous silicon composite materials was characterized by SEM and XRD, and the electrochemical performance was also tested which provided experimental basis for the development of lithium-ion battery based on silicon anode materials.

2.1 The preparation and testing of battery

First, the mixture of different porous silicon composites, acetylene black and teflon (m₁:m₂:m₃ = 80:15:5) were prepared with ethanol, and it was sonicated for 30 min. Subsequently, the mixture was heated at 80 ℃ until it became sticky. The mixture was smeared to battery pole piece, and then the porous silicon composites-modified pole piece was kept at 80 ℃ for 10 h following by tableting. The prepared battery pole piece was immersed into 6 M KOH for 18 h in order to test the electrochemical property in 6 M KOH.

The details of materials and reagents and apparatus was in Supporting Information, and the preparation process of porous silicon, AgNPs and silicon composites was also in Supporting Information.

3.1 The principle of preparation of porous silicon

The structure of porous silicon is the prerequisite for performance of porous silicon composites. In this work, LiAlH₄ was used to reduce white carbon black at high temperature according to Eq. (1):

LiAlH₄+ SiO₂ → LiAlO₂+Si+2H₂ (1)

Absolute dry conditions are necessary during the reaction due to the nature of water explosion of LiAlH₄.

3.2 The characterization of porous silicon composites

XRD was employed to verify the composition and crystal structure of different porous silicon composites. In the XRD spectrum of Si-Ag composites (Fig. 1A), the main diffraction peaks of Si-Ag composites were observed at 38.083°, 44.527°, 64.291° and 77.426° which corresponded to the standard Si (JCPDS no. 35-1158) and Ag (JCPDS no. 04-0783). The diffraction intensity became more stronger compared with peaks of silicon, indicating that the crystallinity of Si-Ag composites was high. This result also showed the successful attachment of AgNPs to porous silicon [12–13]. Figure 1B showed XRD spectrum of Si-Li₂CO₃ composite. The diffraction peaks which were observed from Fig. 1B corresponded to standard Li₂CO₃ diffraction peak (JCPDS no. 22-1141) and Si diffraction peak (JCPDS no. 35-1158). However, the diffraction peak of Si was weak, which might be due to the structure of porous silicon. It was noted that a diffraction peak at 15.618° was observed which was assigned to SiO₂ (JCPDS no. 27–0605), showing that SiO₂ was not completely removed in the preparation of porous silicon. As shown in Fig. 1C, the diffraction peaks corresponded to standard Ag (JCPDS no. 04-0783) and standard Li₂CO₃ (JCPDS no. 22-1141). All of those results suggested the successful preparation of porous silicon composites.

SEM was applied to characterize the morphology of porous silicon composites. As shown in Fig. 2A, some pores were presented in porous silicon with a pore size of about 10–15 µm with the magnification of 500×, and the pores were destroyed and incomplete. It might be due to the high calcination temperature which was harmful to the formation of internal porous structure. When the magnification of SEM reached 2000×, some attachments were observed which was possibly carbon residue (Fig. 2B). The pore structure in Si-Ag porous silicon was very obvious at a magnification of SEM of 500× (Fig. 2C), and some attachments were seen which might be AgNPs and carbon residue at a magnification of SEM of 10000× (Fig. 2D). Likewise, Fig. 2E showed that the pore structure was seriously damaged at a magnification of 500×; and Li₂CO₃ and carbon residue were unevenly distributed on the surface of porous silicon at the magnification of 10000× (Fig. 2F). As could be seen from Fig. 2G, only a few porous structures of porous silicon were be destroyed at a magnification of 500×; and solid particles of different shapes were observed at the magnification of 2000× (Fig. 2H), which might be carbon residue, Li₂CO₃ and AgNPs.

3.3 The electrochemistry testing of porous silicon composites

CV was applied to investigate the electrochemical behavior of these porous silicon composites in 6 M KOH at a scan rate of 0.1V·s^− 1, and the potential was from − 1 V to 1 V. As shown in the cyclic voltammogram of Si-Ag (Fig. 3A), a weakly oxidation peak was observed at the potential of ~ 0.2 V while an oxidation peak also was seen at the potential of ~ 0.5 V, which was ascribed as the oxidation process of AgNPs to Ag₂O and Ag₂O to AgO. Two obvious reduction peaks were seen at the potential of ~ 0.3 V and ~-0.1 V, which was due to the reduction of AgO to Ag₂O and Ag₂O to AgNPs. In the cyclic voltammogram of Si-Li₂CO₃ (Fig. 3B), the oxidation current appeared and the curve began to rise at the potential of 0.25 V, indicating the extraction of Li⁺ from porous silicon composites. An obvious reduction peak appeared at the potential of ~ 0.3V which corresponded to the alloying process of Li⁺, indicating the activation of electrode active substance. An indistinct oxidation peak was seen at the potential of ~-0.2V, which was due to the formation of solid electrolyte interface (SEI) film between electrolyte and electrode active substance [14]. In the cyclic voltammogram of Si-Ag- Li₂CO₃ (Fig. 3C), at about 0.25 V and the current began to rise, indicating that ions of Ag⁺ and Li⁺ had begun to extract; and a very obvious reduction peak appeared at ~-0.16V, which might be due to the insertion of Ag⁺ which leaded to alloying of silicon.

The specific capacitance (C) of these porous silicon composites was estimated according to Eq. (2):

C=S/2(v×s×m) (2)

where S is the integral area of the cyclic voltammogram, v is the potential and m is the mass of material. The specific capacitance of these porous silicon composites was calculated in Table 1.

Table 1

Specific capacitance of the three materials
Name	S/(A·V)	m/mg	C/(mA·h·g^− 1)
Si-Ag	0.1862	7.04	476.0195
Si-Li₂CO₃	0.07456	10.72	125.1943
Si-Ag-Li₂CO₃	0.1469	6.08	435.0168

EIS was used to further explore the electrochemical characteristics of porous silicon composites. The open circuit voltage was maintained at about 1.3 V. The test frequency of EIS was 0.01 ~ 100kHz, and the amplitude was 0.005 V. In Nyquist plot, the diameter of semicircle represented the charge transfer resistance (R_ct) between solution and electrode surface. As shown in Fig. 4, The R_ct of Si-Ag, Si-Li₂CO₃ and Si-Ag-Li₂CO₃ porous silicon composites was respectively ~ 0.78 Ω, ~ 0.8 Ω and ~ 1.4 Ω. Si-Ag porous silicon composites showed the smallest R_ct.

In a word, the structure of porous silicon was destroyed to some extent, and it still showed good electrochemical performance. Porous silicon with fragment structure presented the best electrochemical. Si-Ag composites have higher specific capacity and lower interface impedance, followed by Si-Ag-Li₂CO₃ composites, and Si-Li₂CO₃ composites was the worst.

Research involving Human Participants and/or Animals

Not applicable

Disclosure of potential conflicts of interest

Not applicable

Consent for publication

All of co-authors have agreed to publish this manuscript.

Consent to participate

All of co-authors have consented to participate this work.

Availability of data and materials

All data during this study are included in this manuscript.

Competing interests

There is no conflict of interest.

Authors' contributions

Xuchun Wang: Resources, Methodology, Writing - Review & Editing, Supervision.

Qianrui Liu: Writing-Original Draft.

Jiaohong Shu: Software, Investigation.

Dongdong Ouyang: Software, Investigation.

Xuemei Zhang: Software, Investigation.

Junming Chen: Formal analysis, Visualization.

Huaguang Zhou: Writing - Review & Editing.

Yuyang Zhang: Writing - Review & Editing.

Jinming Kong: Resources.

Funding

Anhui Province University Collaborative Innovation Fund (Grant No. GXXT2019023).

National Natural Science Foundation of China (Grant No. 21974068).

Acknowledgments

Thanks for the supporting of Anhui Province University Collaborative Innovation Fund (Grant No. GXXT2019023), and National Natural Science Foundation of China (Grant No. 21974068).

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Editorial decision: Major revisions
04 Oct, 2021
Reviews received at journal
11 Sep, 2021
Reviewers invited by journal
11 Sep, 2021
Editor assigned by journal
05 Sep, 2021
First submitted to journal
03 Sep, 2021

You are reading this latest preprint version

The Preparation And Electrochemical Performance Analysis of Different Porous Silicon Composites

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Version 1

Abstract

Figures

Introduction

Experimental

2.1 The preparation and testing of battery

Results And Discussion

3.1 The principle of preparation of porous silicon

3.2 The characterization of porous silicon composites

3.3 The electrochemistry testing of porous silicon composites

Conclusion

Declarations

References

Supplementary Files

Status:

Version 1