Scalable Synthesis of Interconnected Porous Silicon/Carbon Composites by the Rochow Reaction as High‐Performance Anodes of Lithium Ion Batteries

Rajagopalan

Guo

et al. 2015

Adv Funct Materials

204

109

A yolk-shell-structured carbon@void@silicon (CVS) anode material in which a void space is created between the inside silicon nanoparticle and the outer carbon shell is considered as a promising candidate for Li-ion cells. Untill now, all the previous yolk-shell composites were fabricated through a templating method, wherein the SiO2 layer acts as a sacrificial layer and creates a void by a selective etching method using toxic hydrofluoric acid. However, this method is complex and toxic. Here, a green and facile synthesis of granadillalike outer carbon coating encapsulated silicon/carbon microspheres which are composed of interconnected carbon framework supported CVS nanobeads is reported. The silicon granadillas are prepared via a modified templating method in which calcium carbonate was selected as a sacrificial layer and acetylene as a carbon precursor. Therefore, the void space inside and among these CVS nanobeads can be formed by removing CaCO3 with diluted hydrochloric acid. As prepared, silicon granadillas having 30% silicon content deliver a reversible capacity of around 1100 mAh g−1 at a current density of 250 mA g−1 after 200 cycles. Besides, this composite exhibits an excellent rate performance of about 830 and 700 mAh g−1 at the current densities of 1000 and 2000 mA g−1, respectively. (≈4200 mAh g −1 ), relatively low discharge potential (≈0.5V vs Li/Li + ), abundance, and environmental benignity. [1][2][3][4][5][6] However, the dramatic volume change (>300%) during lithiation and delithiation processes leads to severe pulverization and continual formation of solid electrolyte interphase (SEI) on the newly formed silicon surfaces, resulting in a large capacity loss. [7][8][9][10][11] Therefore, the cycling performance of silicon-based anodes is still far from satisfactory from a commercial point of view. [ 12 ] Silicon nanoparticles (Si NPs) have been found to tolerate extreme changes in volume with cycling. [ 13 ] Hence, great efforts have been made to improve the cycling stability and electrical conductivity by using various Si-based nanostructures, including Si nanowires, [ 3,14,15 ] porous Si, [16][17][18][19] and conductive agent coated Si such as carbon, [ 18,20,21 ] Ag, [ 22,23 ] and conducting polymer. [ 24 ] Among them, a yolkshell-structured carbon@void@silicon (CVS) composite [ 25,26 ] is quite promising for practical applications, because the void space between the outer carbon shell and the inside Si NP allows the room for volume changes of Si NP without deforming the carbon shell and SEI fi lm, which in turn allows for the growth of a stable SEI on the surface of the outer carbon shell. [ 26 ] Besides, the homogeneous carbon coating shell can prevent the electrolyte ingress and the direct contact of Si NPs with the electrolyte, so the SEI will only be formed on the outer surface of the carbon shell, leading to the high Coulombic effi ciency and improved cycling stability. [ 25 ] For instance, Cui and co-workers achieved a high capacity of ≈2800 mAh g −1 with a very good cycling s...

Section: Introductionmentioning

confidence: 99%

A Green and Facile Way to Prepare Granadilla‐Like Silicon‐Based Anode Materials for Li‐Ion Batteries

Rajagopalan

Guo

et al. 2015

Adv Funct Materials

204

109

“…In addition, Su's group also used commercial silicon microparticles as the silicon source to react with CH3Cl gas over a Cu-based catalyst to create large amounts of macropores within the unreacted silicon (Figure 2c and 2d). 40 Thanks to the interconnected porous structure, this porous silicon-based anode material exhibited excellent electrochemical performance. The discharge capacity of this silicon-based porous material was around 1000 mAh g -1 after 100 cycles, and the average capacity fading rate of this anode was around 0.35%/cycle.…”

Section: Silicon Microparticlesmentioning

confidence: 99%

“…Facile methods such as electroless etching [30][31][32][33][34][35][36][37][38][39][40][41] and electrochemical etching [42][43][44][45][46][47][48] are able to convert bulk silicon wafer into a porous structure with tunable pore size and porosity, which is called 'integral' porosity. For example, with an appropriately doped Si wafer, porous Si and Si nanowires can be synthesized in the presence of silver nitrate (AgNO3) in hydrofluoric acid (HF) etchant solution.…”

Section: Silicon Wafermentioning

confidence: 99%

Si-containing precursors for Si-based anode materials of Li-ion batteries: A review

Energy Storage Materials

Liu

Zhao

et al. 2016

Lithium-ion batteries with high energy density are in demand for consumer electronics, electric vehicles, and grid-scale stationary energy storage. Si is one of the most promising anode materials due to its extremely high specific capacity. However, the full application of Si-based anode materials is limited by poor cycle life and rate capability resulted from low ionic/electronic conductivity and large volume change over cycling. In recent years, great progress has been made in improving the performance of Si anodes by employing nanotechnology. The preparation methods are essentially important, in which the precursors used are crucial to design and control the microstructure for the Si-based materials. In this review, we provide comprehensive summary and comment on different Si-containing precursors for preparation of nanosized Si-based anode materials and focus on the corresponding electrochemical performances in lithium-ion batteries. Bulk sized silicon, silicon wafer and silicon microparticles are generally used as starting materials to synthesize porous or nanosized silicon, and the routes for the synthesis are rather mature and commercially available. Silica is also commonly used to form silicon by conversion through a facile magnesiothermic reduction. Silica derivation from natural resources, especially from rice husks, is much more sustainable and lower cost than alternative methods, which attracts considerable research attention. In addition, gaseous Si-based sources like SiH4, Si2H6 and SiHxCly, liquid silicon sources like trisilane and phenylsilane and elemental silicon have successfully used to prepare nanosized or carbon-coated silicon. Further considerations on massive production possibility have also been presented. Si-Containing Precursors for Si-Based Anode Materials of Li-Ion Batteries AbstractLithium-ion batteries with high energy density and large power output are in demand for consumer electronics, electric vehicles, and grid-scale stationary energy storage. Silicon is one of the most promising anode materials because it has 10 times higher specific capacity than that of the commercial graphitic carbon anode. Unfortunately, the practical utilization of silicon-based anode materials is still hindered by its low electronic conductivity and high capacity fading rate due to the large volume changes upon insertion and extraction of Li ions during cycling. Introducing porous structure, along with decreasing the dimension of Si-based materials to nanosize, is an effective way to address these problems. During the past decade, tremendous attention has been paid to improve Si anodes so as to give them better electrochemical performance. In this review, we focus the Si-containing precursors for preparation of Si-based anode materials.3

“…[ 30 ] Our group developed a scalable method for synthesis of porous Si materials by using the Rochow reaction commonly used in the organosilane industry, in which the Si microparticles react with gas CH 3 Cl over Cu-based catalyst, and demonstrated their promising application as porous Si/C anode materials in Li-ion batteries (LIBs). [ 20 ] In recent years, there has been an increasing demand for portable electronics, electric vehicles, and energy storage devices/technologies, which has stimulated signifi cant interest in LIBs with both high energy density and power performance. [ 31,32 ] Comparing with graphite (372 mAh g −1 ), Si is considered to be the next generation anode materials for LIBs, because of its large theoretical capacity (4200 mAh g −1 ), relatively low discharge potential (≈0.5 V versus Li/Li + ), abundant resource, low cost, and safety.…”

mentioning

confidence: 99%

“…[ 16 ] Controllable fabrication of Si nanostructures is the prerequisite for developing their practical applications but still quite challenging. Many methods, such as vapor-liquid-solid growth, [ 9,17,18 ] solvothermal method, [ 19 ] Rochow reaction method, [ 20 ] electrochemical etching, [ 21 ] reduced various silica using Mg powders, [ 22,23 ] and noble metal-assisted chemical etching [ 24,25 ] have been developed or applied for their fabrication. For example, Cui's group manufactured interconnected Si hollow nanospheres by chemical vapor deposition (CVD) of SiH 4 on the silica template, followed with removal of the silica cores by hydrofl uoric acid…”

mentioning

confidence: 99%

Low‐Cost Synthesis of Porous Silicon via Ferrite‐Assisted Chemical Etching and Their Application as Si‐Based Anodes for Li‐Ion Batteries

Wang

Ren

et al. 2015

Adv Elect Materials

Self Cite

orientation of Si nanostructures relative to the substrate, and the high surface-to-volume ratio structures, and all the experiments can be carried out in a chemical lab without expensive equipment. [ 28 ] However, because of the use of noble metal as the catalysts, the fabrication cost is still too high for practical applications. Recently, Jiang et al. developed a simple and inexpensive method to prepare porous Si powder by acid etching Al-Si alloy powder. [ 29 ] Qian's group reported a hydrothermal synthesis of porous Si anode materials using very cheap silica sol. [ 30 ] Our group developed a scalable method for synthesis of porous Si materials by using the Rochow reaction commonly used in the organosilane industry, in which the Si microparticles react with gas CH 3 Cl over Cu-based catalyst, and demonstrated their promising application as porous Si/C anode materials in Li-ion batteries (LIBs). [ 20 ] In recent years, there has been an increasing demand for portable electronics, electric vehicles, and energy storage devices/technologies, which has stimulated signifi cant interest in LIBs with both high energy density and power performance. [ 31,32 ] Comparing with graphite (372 mAh g −1 ), Si is considered to be the next generation anode materials for LIBs, because of its large theoretical capacity (4200 mAh g −1 ), relatively low discharge potential (≈0.5 V versus Li/Li + ), abundant resource, low cost, and safety. [ 33 ] Tremendous efforts have been made to synthesize Si-based anodes with porous structure and coated with a conductive carbon layer to improve the capacity and cycling performance, [ 34,35 ] include porous Si particles, [ 36,37 ] and porous Si/C composites. [ 38 ] This is because the porous Si structure can absorb the huge volume change of Si during Li insertion and extraction reactions and hinder the cracking or crumbling of the electrode, whereas the porous Si/C composites can possess the advantages of both C (long cycle life) and porous Si. [ 39 ] In addition, carbon coated porous metal oxides composites are also good anode materials for LIBs because of their larger lithium storage capacities and better safety than that of the commercially used graphite. [ 40,41 ] Inspired by above mentioned reported work about noble metal-assisted chemical etching method, [ 24,25 ] here, we developed another novel method to prepare porous Si materials using the low-cost ferrite catalyst by replacing the noble metals to catalyze the reaction between Si and liquid glycol. This new approach inherits the advantages of the noble metal-assisted chemical etching method but avoids its disadvantages and can be easily scaled up for porous Si materials production. Compared with recent other low cost synthesis porous Si strategies (such as acid etching Al-Si alloy powder [ 29 ] and hydrothermal synthesis using silica sol, [ 30 ] this strategy has advantages of Nanostructured porous Si materials have received great attention because of their numerous potential applications in electronics, [1][2][3] photonics, [4][5][6] ...