BET and BJH analysis of (a) nano-silicon (ref), and (d) nano-silicon (syn). b) Cycling performance of nano-silicon/Li cells. XRD patterns of (a) silicon chip and (b) Si/C composite. b) Cycling performance of Si/C composite/Li cell. Nowadays, Li-ion batteries (LIB) are used in many areas such as mobile electronics, electric vehicles and large-scale smart grids.
Since the first commercialized Li-ion batteries developed by SONY in 1991, LIBs have made great progress and been successfully used in many areas. In Chapter 1, we introduce a basic description of Li-ion battery system (LIBs), anode materials for LIBs and challenges in silicon anode. In Chapter 2 we introduce a scalable method for the selective extraction of high-quality nano-silicon from industrial slag.
Here, we use a mixture of metal (eg aluminum) and metal halide (eg aluminum chloride), we can extrude nano-silicon at low temperature. Interestingly, the extracted nano-silicon has high purity, regular size (200~300 nm) and regular structure, thus showing improved cyclability.
Introduction of Li-ion batteries
Introduction
- Basic decription of Li-ion batteries
- Anode materials choice for Li-ion batteries
- Challenges in Silicon andoe
LIB anode materials can be classified into three main categories in terms of reaction mechanism; (i) (de)intercalation (ii) (de)alloying and (iii) conversion7,24. Due to its structural stability, (de)intercalation materials show excellent cyclability in Li-ion batteries15-17. However, conversion anode materials have a fatal drawback such as large voltage hysteresis that causes poor energy efficiency25-26.
Tin and silicon are representative materials for anode (de)alloy materials for Li-ion batteries27-28. These (de)alloy materials have several advantages such as high abundance, low price and high theoretical capacity29-31. For the aforementioned reasons, much research has focused on (de)alloy materials as anode materials for Li-ion batteries29-31.
This drawback prevents the commercialization of (de)alloyed materials as anode materials for Li-ion batteries. In addition, many researches have been carried out nowadays on various materials such as organic materials and Li-metals as anode materials for Li-ion batteries33-35. After SONY commercialized the lithium-ion battery (LIB) in 1991, it began to be used in all aspects of society5-6.
Silicon is considered one of the most promising anode materials for the next generation of LIBs, because silicon has many advantages: first, it has the highest theoretical capacity (4200 mAh/g), which is more than 10 times higher than that of commercial graphite anode36- 37.
A study of highly oriented pyrolytic graphite as a model for the graphite anode in Li-ion batteries. L.; Inorganic materials for the negative electrode of lithium-ion materials: state-of-the-art and future prospects Mater. Beyond Intercalation-Based Li-Ion Batteries: State of the Art and Challenges in Electrode Material Reaction Through Conversion Reactions.
Recent findings and prospects in the field of pure metals as negative electrodes for Li-ion batteries. 25th Anniversary Article: Understanding Lithiation of Silicon and Other Alloy Anodes for Lithium-Ion Batteries. High-capacity anode materials for lithium-ion batteries: Selection of elements and structures for active particles.
Luo, F.; Liu, B.; Zheng, J.; Chu, G.; Zhong, K.; Lee, H.; Huang, X.; Chen, L; Review-Nano- Silicon/Carbon Composite Anode Materials Towards Practical Application for Next Generation Li-Ion Batteries.
Scalable method of selective extraction of high-quality nano-Si from industrial slag
- Introduction
- Nano-silicon
- Thermochmical reduction of SiO 2
- Experimental Section
- Extraction of Nano-silicon from industrial slag
- Material characterization
- Electrochemical test
- Results and Discussion
- Conclusion
- References
Here, we have made high-quality nano-silicon using a metallothermic reduction using metal halide (AlCl3). Battery performance was measured by galvanostatic cycling (WonATech WBCS 3000 battery measurement system) of a coin-type half-cell (CR2016) with extruded nano-silicon as the working electrode and lithium foil as the reference/counter electrode. Due to the lower surface area of the extracted nano-silicon, it has lower possibility of side reaction between the nano-silicon surface and the electrolyte.
This is a natural result of the lower surface area, which can reduce the irreversible side reaction with the electrolyte of the extracted nano-silicon. First, our extracted nano-silica particles have excellent dispersibility compared to reference nano-silica particles. Due to the excellent dispersibility, our nano-silicon particle was uniformly well dispersed in the electrode.
We have demonstrated a cost-effective and simple method for the synthesis of nanosilicon from industrial slag. Based on theories, we reduce the activation energy of metallothermal reduction for the synthesis of nano-silicon. Here, we synthesized a unique Si/C composite material structure for LIB anode using polyacrylonitrile polymer and silicon chip.
Battery performance was measured by galvanostatic cycling (WonATech WBCS 3000 battery measurement system) of coin-type half-cells (CR2032) with the synthesized Si/C composite as the working electrode and lithium foil as the reference/counter electrode. Here we use activation super P to increase conductivity in Si/C composite and use HNO3 to activate super P. If Si/C composite makes SiC, then (1 1 1) plane top of SiC would appear at the two theta is 36o.
Due to the large amount of vacancies in the Si/C composite, the ICE value in the Si/C composite decreased. First, by using oxidized silicon chip as silicon, we can easily make York shell structure in Si/C composite. Second, by using the solvent exchange method, we can easily make a large amount of pores in the Si/C composite.
A facile synthesis of uniqued structure Si/C composite
Introduction
- Si-based composite material
Silicon has the highest capacity of 4200 mAh/g, which is more than 10 times higher than commercialized graphite anode (372 mAh/g)1-2. Due to the highest capacity, silicon is considered as one of the most promising anode materials for next-generation LIBs. However, due to large volume changes during charging and discharging and low electrical conductivity, it is difficult to use in practical LIBs3.
Such Si-based composite material structure is the physical mixture of support materials and silicon particles or silicon particles occupied in the framework of the support materials6-8. Si-based composite materials synthesized by various methods such as hydrothermal reaction, electrospraying and emulsion reaction9-11. Due to the structural characteristics of Si-based composite materials and the properties of support materials, Si-based composite materials have several advantages compared to silicon such as structure stability, high tapping density and fast Li-ion transfer and electrons4-8.
ExperimentalSection
- Oxidation of silicon chip
- Synthesis of Si/C composite
- Material characterization
- Electrochemical test
The electrolyte included 1.3 M LiPF6 in ethylene carbonate/diethyl carbonate, volume ratio 3/7 with 10 wt% fluorinated ethylene carbonate additives.
Results and Discussion
Conclusion
