Scalable 3D porous residual Al-doped Si/SiOx composites for high performance anodes: Coupling effects of porosity, conductive sites and oxide layer

Economic synthesis of sub-micron brick-like Al-MOF with designed pore distribution for lithium-ion battery anodes with high initial Coulombic efficiency and cycle stability

Metal-organic frameworks (MOFs) have exhibited great potential for lithium-ion batteries (LIBs). However, to date, it is difficult to fabricate MOF electrode materials with regular shape and rational pore distribution by an economic approach, and the currently achieved MOF electrode materials usually have a relatively low initial Coulombic efficiency and poor cycle stability, which is not satisfactory for practical application. In this study, by using the recycled AlCl₃ solution after dealloying treatment of Al-Si alloy, an evenly distributed brick-like Al-MOF with sub-micron size and rational pore distribution was synthesized for the first time. Because of the larger size and more macropores, the as-prepared Al-MOF electrode exhibits superior initial Coulombic efficiency as high as 96.6% for LIB anodes. Moreover, on account of the irregular crystal defects at the edge of the designed macropores, which result from unstable connection between the inorganic nodes (AlO₆ octahedral cluster) and the organic linkers (PTA) and result in the formation of spherical nano-sized particles with better structural stability, the electrode materials show excellent cycle stability with discharge attenuation rate of 0.051%. The electrochemical performance considerably outperforms that of reported Al-MOF anodes and some representative MOF anodes in other studies. The robust realization of high initial Coulombic efficiency and cycle stability defines a critical step to capturing the full potential of MOF electrode materials in practical LIBs.

Recycling Si waste cut from diamond wire into high performance porous Si@SiO2@C anodes for Li-ion battery

The Si particle waste cut from diamond wire in photovoltaic industry is chose as an environmental friendly and low-cost resource for Li-ion battery. In this study, the pollutions of SiO₂ layer, adhered trace metal and organic impurities on the Si particle waste can be removed by the facile processes of corrosion and pyrolysis. The removal ratios of organic and metal impurities were 70.42% and 66.76%, respectively. The different kinetic models for the removal of metal impurities demonstrate that the leaching is more suitable for controlling by second-order reaction of homogeneous models (R² =0.992, m=2). The preparation analysis of porous Si@SiO₂ with a 3D cluster nanoporous structure using a special bubble corrosion method was firstly proposed and discussed intensively. The first discharge and charge capacities of porous Si@SiO₂ @C composites reached 2579.8 and 2184.1 mAh/g, the initial CE reached 84.66%, and the corresponding capacities after 100 cycles reached 1051.4 and 1038.2 mAh/g, which showed the better electrical performance. This study establishes a theoretical basis for recycling Si particle waste cut from diamond wire, and provides technical support for the energy sustainable development.

One-Step Low-Temperature Molten Salt Synthesis of Two-Dimensional Si@SiOx@C Hybrids for High-Performance Lithium-Ion Batteries

Various strategies have been developed to mitigate the huge volume expansion of a silicon-based anode during the process of (de)lithiation and accelerate the transport rate of the ions/electrons for lithium-ion batteries (LIBs). Here, we report a one-step synthetic route through a low-temperature eutectic molten salt (LiCl-KCl, 352 °C) to fabricate two-dimensional (2D) silicon-carbon hybrids (Si@SiO_x@MpC), in which the silicon nanoparticles (SiNPs) with an ultrathin SiO_x layer are fully encapsulated by graphene-like carbon nanosheets derived from a low-cost mesophase pitch. The combination of an amorphous graphene-like carbon conductive matrix and a SiO_x protective layer strongly promotes the electrical conductivity, structure stability, and reaction kinetics of the SiNPs. Consequently, the optimized Si@SiO_x@MpC-2 anode delivers large reversible capacity (1239 mAh g^-1 at 1.0 A g^-1), superior rate performance (762 mAh g^-1 at 8 A g^-1), and long cycle life over 600 cycles (degradation rate of only 0.063% every cycle). When coupled with a homemade nano-LiFePO₄ cathode in a full cell, it exhibits a promising energy density of 193.5 Wh kg^-1 and decent cycling stability for 200 cycles at 1C. The methodology driven by salt melt synthesis paves a low-cost way toward simple fabrication and manipulation of silicon-carbon materials in liquid media.