Reconstructed Nano-Si Assembled Microsphere via Molten Salt-Assisted Low-Temperature Aluminothermic Reduction of Diatomite as High-Performance Anodes for Lithium-Ion Batteries

Abstract

Silicon (Si), as a promising candidate anode material of lithium-ion batteries (LIBs), is going to have large-scale applications. Its high theoretical specific capacity, low lithiation potential, and natural abundance can meet the consumer expectation for the high energy density and cycle life of LIBs. At present, the huge volume change and very high manufacturing costs also hinder its wide applications. Therefore, preparation of Si material using abundant siliceous rocks in earth and reasonable structure design are important strategies to solve the problems. Here, we report a new nano/microstructure of Si microsphere assembled by nano-Si via molten salt-assisted lowtemperature aluminothermic reduction of diatomite. The use of abundant diatomite can reduce the synthetic cost of Si. Moreover, the molten salt-assisted low-temperature aluminothermic reduction can significantly lower the synthesis temperature and energy consumption to further reduce the cost. More importantly, the new nano/ microstructure of Si microsphere can disperse expansion stress in local nanocrystalline area compared to the bulk perfect crystalline Si. As the anode of LIBs, the electrode exhibits good cycle stability and can deliver a reversible capacity of 1330.1 mAh g −1 after 200 cycles at 0.2 A g −1 . This work offers a cheap synthesis route to prepare new nano/microstructure and is significant for large-scale applications of Si materials.

Silicon Nanospheres Supported on Conductive MXene Nanosheets as Anodes for Lithium-Ion Batteries

“…The high-resolution TEM (HRTEM) image exhibits a lattice spacing of 0.31 nm, which corresponds to the (111) plane of the Si crystal (Figure 2f). 36 The elemental analysis of the Si NP/MXene composite (Figure 2g) shows features corresponding to Si, Ti, and C elements and confirms that Si NPs firmly anchored to the MXene nanosheets. Through electrostatic assembly and annealing treatment, Si NPs bound to MXene sheets to form a stable hierarchical structure.…”

“…The edge magnification shows that the MXene nanosheet presents wrinkles, and Si NPs are firmly embedded onto MXene nanosheets (Figure e). The high-resolution TEM (HRTEM) image exhibits a lattice spacing of 0.31 nm, which corresponds to the (111) plane of the Si crystal (Figure f) . The elemental analysis of the Si NP/MXene composite (Figure g) shows features corresponding to Si, Ti, and C elements and confirms that Si NPs firmly anchored to the MXene nanosheets.…”

Nitrogen Plasma-Assisted Functionalization of Silicon/Graphite Anodes to Enable Fast Kinetics

“…As silicon-based anodes combining graphite anodes offer higher gravimetric and volumetric capacities than conventional lithium-ion batteries (LIBs), utilizing more plausible and practical perspectives to establish high-energy storage applications has attracted several research strategies for silicon-based anodes. − Owing to their higher specific capacity (3579 mA h g –1 ) than the graphite anode (372 mA h g –1 ), silicon-based anodes play a significant role in next-generation battery applications. , Especially, in terms of commercialized battery anodes, the portion of graphite is gradually replaced with silicon to achieve a high-energy density composite electrode. , However, to utilize silicon as the principal active material, existing challenges need to be considered with its intrinsic properties. , The major problem is the volume expansion of silicon material, which accompanies the cracking of the material itself and eventually degrades the electrode structure, generating electrically isolated electrode components. , The volume expansion of silicon induces undesirable solid electrolyte interphase (SEI) layer growth aroused on the newly exposed silicon surface after particle fracture, which is another vital issue that promotes excessive electrolyte consumption …”

“…2,10 The major problem is the volume expansion of silicon material, which accompanies the cracking of the material itself and eventually degrades the electrode structure, generating electrically isolated electrode components. 11,12 The volume expansion of silicon induces undesirable solid electrolyte interphase (SEI) layer growth aroused on the newly exposed silicon surface after particle fracture, which is another vital issue that promotes excessive electrolyte consumption. 13 Another drawback of silicon is the inherently low electrical conductivity of silicon (6.7 × 10 −4 S cm −1 ) itself, which limits the conductive pathway of the electrode.…”

In Situ Synthesis of a Si/CNTs/C Composite by Directly Reacting Magnesium Silicide with Lithium Carbonate for Enhanced Lithium Storage Capability

“…Nowadays, the fast development of electric vehicles and portable electronic devices requires lithium-ion batteries (LIBs) with a high energy density and long cycling life. , A silicon (Si)-based anode material is considered to be the most promising candidate because of its high lithium storage capacity of 3579 mA h g –1 (Li 15 Si 4 ), low voltage platform (∼0.4 V vs Li/Li + ), and abundant resources. − The commercial implementation of Si-based anodes is greatly restricted by low intrinsic conductivity and a huge volume variation of 380% during continuous charge–discharge cycles. This large volume expansion would pulverize the active particles, resulting in gradual capacity fading and unstable growth of the solid–electrolyte interphase (SEI). − Moreover, the poor electrical and ionic conductivity causes slow electron and Li-ion transportation, leading to an inferior rate performance of the final batteries. − …”