Dual network porous Si/Al9FeSi3/Fe2O3 composite for high performance Li-ion battery anode

Synthesis of Si/Fe2O3-Anchored rGO Frameworks as High-Performance Anodes for Li-Ion Batteries

By virtue of the high theoretical capacity of Si, Si-related materials have been developed as promising anode candidates for high-energy-density batteries. During repeated charge/discharge cycling, however, severe volumetric variation induces the pulverization and peeling of active components, causing rapid capacity decay and even development stagnation in high-capacity batteries. In this study, the Si/Fe2O3-anchored rGO framework was prepared by introducing ball milling into a melt spinning and dealloying process. As the Li-ion battery (LIB) anode, it presents a high reversible capacity of 1744.5 mAh g-1 at 200 mA g-1 after 200 cycles and 889.4 mAh g-1 at 5 A g-1 after 500 cycles. The outstanding electrochemical performance is due to the three-dimensional cross-linked porous framework with a high specific surface area, which is helpful to the transmission of ions and electrons. Moreover, with the cooperation of rGO, the volume expansion of Si is effectively alleviated, thus improving cycling stability. The work provides insights for the design and preparation of Si-based materials for high-performance LIB applications.

Unraveling the New Role of Metal-Organic Frameworks in Designing Silicon Hollow Nanocages for High-Energy Lithium-Ion Batteries

Metal-organic framework (MOF)-derived materials are attracting considerable attention because of the moldability in compositions and structures, enabling greater performances in diverse applications. However, the nanostructural control of multicomponent MOF-based complexes remains challenging due to the complexity of reaction mechanisms. Herein, we present a surface-induced self-nucleation-growth mechanism for the zeolitic imidazolate framework (ZIF) to prepare a new type of ZIF-8@SiO₂ polyhedral nanoparticles. We discover that the Zn hydroxide moieties (Zn-OH) within ZIF-8 can trigger the hydrolysis of tetraethyl orthosilicate effectively on the ZIF-8 surface precisely, avoiding the formation of free orthosilicic acid (Si(OH)₄) successfully. This is a pioneering work to elucidate the importance of MOF surface properties for preparing multicomponent materials. Then, a novel well-dispersed silicon hollow nanocage (H-Si@C) modified by the carbon was prepared after removal of the ZIF-8 and magnesiothermic reduction. The as-prepared H-Si@C demonstrates an overwhelmingly high lithium storage capability and extraordinary stability in lithium-ion batteries (LIBs), particularly the impressive performances when it was matched with the LiNi_0.6Co_0.2Mn_0.2O₂ cathode in a full cell. The MOF surface-induced self-nucleation-growth strategy is useful for preparing more multifunctional materials, while the study of lithium storage performances of the H-Si@C material is practical for LIB applications.

Sn modified nanoporous Ge for improved lithium storage performance

Although high-capacity germanium (Ge) has been regarded as the promising anode material for lithium ion batteries (LIBs), its actual performance is far from expectation because of low electrical conductivity and rapid capacity decay during cycling. In this work, Sn modified nanoporous Ge materials with different Ge/Sn atomic ratios in precursors were synthesized by a simple melt-spinning and dealloying strategy. As the anodes of LIBs, Sn modified nanoporous Ge materials display improved cycling stability compared with Sn-free nanoporous Ge, revealing a potential role of Sn in improving electrochemical properties of Ge-based anodes. In particular, Sn modified nanoporous Ge with Ge/Sn atomic ratio of 3:1 presents the best Li storage performance among measured electrodes, delivering a reversible capacity of 974 mA h g^-1 after 500 cycles at 200 mA g^-1. It is found that the introduction of appropriate amount of Sn can not only regulate the nanoporous structure of Ge to better alleviate volume expansion, but also improves the conductivity and activity of the electrode material. This improvement is demonstrated by density functional theory calculations. The study uncovers a route to improve Li storage properties by rationally modify Ge-based anodes with Sn, which may facilitate the development of high-performance LIBs.

Improving the Cycling Stability of Fe3O4/NiO Anode for Lithium Ion Battery by Constructing Novel Bimodal Nanoporous Urchin Network

The development of facile preparation methods and novel three-dimensional structured anodes to improve cycling stability of lithium ion batteries (LIBs) is urgently needed. Herein, a dual-network ferroferric oxide/nickel oxide (Fe3O4/NiO) anode was synthesized through a facile dealloying technology, which is suitable for commercial mass manufacturing. The dual-network with high specific surface area contains a nanoplate array network and a bimodal nanoporous urchin network. It exhibits excellent electrochemical performance as an anode material for LIB, delivering a reversible capacity of 721 mAh g-1 at 100 mA g-1 after 100 cycles. The good lithium storage performance is related to the ample porous structure, which can relieve stress and mitigate the volume change in the charge/discharge process, the interconnected porous network that enhances ionic mobility and permeability, and synergistic effects of two kinds of active materials. The paper provides a new idea for the design and preparation of anode materials with a novel porous structure by a dealloying method and may promote the development of the dealloying field.