Polyaniline/Tungsten Trioxide Organic-Inorganic Hybrid Anode for Aqueous Proton Batteries

Aqueous proton batteries have received increasing attention due to their outstanding rate performance, stability and high capacity. However, the selection of anode materials in strongly acidic electrolytes poses a challenge in achieving high-performance aqueous proton batteries. This study optimized the proton reaction kinetics of layered metal oxide WO3 by introducing interlayer structural water and coating polyaniline (PANI) on its surface to prepare organic-inorganic hybrid material (WO3 ⋅ 2H2O@PANI). We constructed an aqueous proton battery with WO3 ⋅ 2H2O@PANI anode and MnO2@GF cathode. After 1500 cycles at a current density of 10 A g-1, the capacity retention rate can still reach 80.2 %. These results can inspire the development of new aqueous proton batteries.

Restricted-magnesium-vapor-reduction of amorphous SiO/C precursors to polycrystalline Si/SiOx/C hybrid anodes

Considering the electrochemical activity/stability and preparation feasibility of silicon (Si) nanomaterials, we designed a restricted-magnesium-vapor-reduction to fabricate sustainable Si/SiO_x/C porous anodes with nanopores and polycrystalline structures.

Rational Design of Silicon Nanodots/Carbon Anodes by Partial Oxidization Strategy with High-Performance Lithium-Ion Storage

Silicon (Si) is considered a promising anode material for rechargeable lithium-ion batteries (LIBs) due to its high theoretical capacity, low working potential, and safety features. However, the practical use of Si-based anodes is hampered by their huge volume expansion during the process of lithiation/delithiation, and they have relatively low intrinsic electronic conductivity, therefore seriously restricting their application in energy storage. Here, we propose a facile approach to directly transform siliceous biomass (bamboo leaves) into a porous carbon skeleton-wrapped Si nanodot architecture through a partial oxidization strategy and magnesium thermal reaction to obtain a high Si nanodot component composite (denoted as Si/C-O). With the synergistic effect of the porous carbon skeleton structure and uniformly dispersed Si nanodots, the Si/C-O composite anode with a stable structure that can avoid pulverization and accommodate volume expansion during cycling is fabricated. As expected, the biomass-converted Si/C-O anode not only presents a high Si component (59.7 wt %) by TGA but also exhibits an excellent capacity of 1013 mAh g^-1 at 0.5 A g^-1 and robust cycling stability with a capacity retention of 526 mAh g^-1 after 650 cycles. Moreover, the Si/C-O anode demonstrates considerable performance in practical LIBs when assembled with a commercial LiNi_0.8Co_0.1Mn_0.1O₂ cathode. This work provides an effective strategy and long-term insights into the utilization of porous Si-based materials converted by biomass to design and synthesize high-performance LIB materials.

Assembly: A Key Enabler for the Construction of Superior Silicon-Based Anodes

Silicon (Si) is regarded as the most promising anode material for high-energy lithium-ion batteries (LIBs) due to its high theoretical capacity, and low working potential. However, the large volume variation during the continuous lithiation/delithiation processes easily leads to structural damage and serious side reactions. To overcome the resultant rapid specific capacity decay, the nanocrystallization and compound strategies are proposed to construct hierarchically assembled structures with different morphologies and functions, which develop novel energy storage devices at nano/micro scale. The introduction of assembly strategies in the preparation process of silicon-based materials can integrate the advantages of both nanoscale and microstructures, which significantly enhance the comprehensive performance of the prepared silicon-based assemblies. Unfortunately, the summary and understanding of assembly are still lacking. In this review, the understanding of assembly is deepened in terms of driving forces, methods, influencing factors and advantages. The recent research progress of silicon-based assembled anodes and the mechanism of the functional advantages for assembled structures are reviewed from the aspects of spatial confinement, layered construction, fasciculate structure assembly, superparticles, and interconnected assembly strategies. Various feasible strategies for structural assembly and performance improvement are pointed out. Finally, the challenges and integrated improvement strategies for assembled silicon-based anodes are summarized.

Advances of Synthesis Methods for Porous Silicon-Based Anode Materials

Silicon (Si)-based anode materials have been the promising candidates to replace commercial graphite, however, there are challenges in the practical applications of Si-based anode materials, including large volume expansion during Li⁺ insertion/deinsertion and low intrinsic conductivity. To address these problems existed for applications, nanostructured silicon materials, especially Si-based materials with three-dimensional (3D) porous structures have received extensive attention due to their unique advantages in accommodating volume expansion, transportation of lithium-ions, and convenient processing. In this review, we mainly summarize different synthesis methods of porous Si-based materials, including template-etching methods and self-assembly methods. Analysis of the strengths and shortages of the different methods is also provided. The morphology evolution and electrochemical effects of the porous structures on Si-based anodes of different methods are highlighted.

Surface Modification and Functional Structure Space Design to Improve the Cycle Stability of Silicon Based Materials as Anode of Lithium Ion Batteries

Silicon anode is considered as one of the candidates for graphite replacement due to its highest known theoretical capacity and abundant reserve on earth. However, poor cycling stability resulted from the “volume effect” in the continuous charge-discharge processes become the biggest barrier limiting silicon anodes development. To avoid the resultant damage to the silicon structure, some achievements have been made through constructing the structured space and pore design, and the cycling stability of the silicon anode has been improved. Here, progresses on designing nanostructured materials, constructing buffered spaces, and modifying surfaces/interfaces are mainly discussed and commented from spatial structure and pore generation for volumetric stress alleviation, ions transport, and electrons transfer improvement to screen out the most effective optimization strategies for development of silicon based anode materials with good property.

Electrostatic Interactions Leading to Hierarchical Interpenetrating Electroconductive Networks in Silicon Anodes for Fast Lithium Storage

Recently, the frequency of combining MXene, which has unique properties such as metal-level conductivity and large specific surface area, with silicon to achieve excellent electrochemical performance has increased considerably. There is no doubt that the introduction of MXene can improve the conductivity of silicon and the cycling stability of electrodes after elaborate structure design. However, most exhaustive contacts can only improve the electrode conductivity on the plane. Herein, a MXene@Si/CNTs (HIEN-MSC) composite with hierarchical interpenetrating electroconductive networks has been synthesized by electrostatic self-assembly. In this process, the CNTs are first combined with silicon nanoparticles and then assembled with MXene nanosheets. Inserting CNTs into silicon nanoparticles can not only reduce the latter's agglomeration, but also immobilizes them on the three-dimensional conductive framework composed of CNTs and MXene nanosheets. Therefore, the HIEN-MSC electrode shows superior rate performance (high reversible capacity of 280 mA h^-1 even tested at 10 A g^-1 ), cycling stability (stable reversible capacity of 547 mA h g^-1 after 200 cycles at 1 A g^-1 ) and applicability (a high reversible capacity of 101 mA h g^-1 after 50 cycles when assembled with NCM622 into a full cell). These results may provide new insights for other electrodes with excellent rate performance and long-cycle stability.

Regulating the carbon distribution of anode materials in lithium-ion batteries

The exploration of electrode materials is considered to be a crucial process affecting the development of lithium-ion batteries. However, the large-scale commercial application of the great mass of anode materials has been hampered by the challenges with conductivity and volume change. These problems can be solved by the combination of a carbon-matrix with anode materials, which has proven to be an effective strategy. This review aims to outline recent advances in carbon-matrix composite anodes based on different dimensions (0D, 1D, 2D, 3D and atomic scale) and functions, with the emphasis on the regulation of carbon distribution of composite anodes. Besides, the matrix forms and carbon sources have also been summarized. This review will provide some light on the future carbon-matrix electrode design trends for LIBs.

Long-term cycling stability of NiCo2S4 hollow nanowires supported on biomass-derived ultrathin N-doped carbon 3D networks as an anode for lithium-ion batteries

A bio-based N-doped carbon 3D network is designed to fabricate a composite anode for LIBs. Benefiting from the highly active substrate and the supported NiCo2S4 hollow nanowires, the composites exhibit an ultrahigh reversible capacity of 1198 mA h g-1 after 500 cycles, holding great potential for long-term applications.

Carbon-coated TiNb2O7 nanosheet arrays as self-supported high mass-loading anodes for flexible Li-ion batteries

A TiNb₂O₇ anode constructed with carbon-coated nanosheet arrays on carbon cloth is prepared by a facile solvothermal process and post carbon-coating for the first time. With nanosized diffusion-length and reduced polarization resistance, this anode exhibits superior high-rate capability based on relatively high mass-loading. Meanwhile, it demonstrates excellent cycling stability and mechanical flexibility as expected from flexible Li-ion batteries.

1-(2-Cyanoethyl)pyrrole enables excellent battery performance at high temperature via the synergistic effect of Lewis base and C[triple bond, length as m-dash]N functional groups

The electrolyte of a lithium ion battery is unstable and is easily decomposed at high temperature, which can lead to the degradation of battery performance. To solve this problem, herein a novel electrolyte additive 1-(2-cyanoethyl)pyrrole (CP) has been proposed to improve the electrochemical performance of LiFePO4 batteries at high temperature. The capacity retention of the battery with 1 wt% CP is 76.7%, while that of the battery without the additive is 38.1% after 200 cycles at 60 °C. Theoretical calculation results reveal that the binding energy of CP and PF5/HF is much higher than that of the solvents in the electrolyte. Surface analysis of the electrodes demonstrates that CP can reduce the decomposition of the electrolyte, and restrain the dissolution of transition metals in the electrolyte at high temperature. TEM/XPS results indicate that CP can modify the protective film on the surface of the cathode material and promote the formation of more regular and thinner CEI films. The promotion of the CP additive is of great significance for improving the high temperature performance of lithium ion batteries and is expected to be applied on a large scale.