Scalable solvent-free mechanofusion and magnesiothermic reduction processes for obtaining carbon nanospheres-encapsulated crystalline silicon anode for Li-ion batteries

Three-Dimensional Characterization of Dry Particle Coating Structures Originating from the Mechano-fusion Process

Dry particle coating processes are of key importance for creating functionalized materials. By a change in surface structure, initiated during coating, a surface property change and thus functionalization can be achieved. This study introduces an innovative approach employing 3D X-ray micro-computed tomography (micro-CT) to characterize coated particles, consisting of spherical alumina particles (d50 = 45.64 μm), called hosts, surrounded by spherical polystyrene particles (d50 = 3.5 μm), called guests. The formed structures, hetero-aggregates, are generated by dry particle coating using mechano-fusion (MF). A deeper understanding of the influence of MF process parameters on the coating structures is a crucial step toward tailoring of coating structure, resulting surface property and functionalization. Therefore, the influence of rotational speed, process time, and total mechanical energy input during MF is explored. Leveraging micro-CT data, acquired of coated particles, enables non-stereologically biased and quantitative coating structure analysis. The guest's coating thickness is analyzed using the maximum inscribed sphere and ray method, two different local thickness measurement approaches. Particle-discrete information of the coating structure are available after a proper image processing workflow is implemented. Coating efficiency and guest's neighboring relations (nearest neighbor distance and number of neighbors inside search radius) are evaluated.

Review of the Scalable Core-Shell Synthesis Methods: The Improvements of Li-Ion Battery Electrochemistry and Cycling Stability

The demand for lithium-ion batteries has significantly increased due to the increasing adoption of electric vehicles (EVs). However, these batteries have a limited lifespan, which needs to be improved for the long-term use needs of EVs expected to be in service for 20 years or more. In addition, the capacity of lithium-ion batteries is often insufficient for long-range travel, posing challenges for EV drivers. One approach that has gained attention is using core-shell structured cathode and anode materials. That approach can provide several benefits, such as extending the battery lifespan and improving capacity performance. This paper reviews various challenges and solutions by the core-shell strategy adopted for both cathodes and anodes. The highlight is scalable synthesis techniques, including solid phase reactions like the mechanofusion process, ball-milling, and spray-drying process, which are essential for pilot plant production. Due to continuous operation with a high production rate, compatibility with inexpensive precursors, energy and cost savings, and an environmentally friendly approach that can be carried out at atmospheric pressure and ambient temperatures. Future developments in this field may focus on optimizing core-shell materials and synthesis techniques for improved Li-ion battery performance and stability.

High-performance Si@C anode for lithium-ion batteries enabled by a novel structuring strategy

Si anode has drawn growing attention because of its features of large specific capacity, low electrochemical potential, and high natural abundance. However, it suffers from severe electrochemical irreversibility due to its large volume change during cycling. In spite of the achievement of improved electrochemical performance after compositing with carbon materials, most of the reported Si/C composite anodes lack a simple preparation process. To obtain a promising Si-based anode material, both simple preparation process and improved performance are necessary. Herein, inspired by the structure of shock proof foam, a novel structure of Si-based composite (Si@FeNO@P), consisting of Si nanoparticles embedded within a highly graphitized Fe3C/Fe3O4 hybrid nanoparticle-interspersed foam-like porous carbon matrix, has been constructed using a simple method, consisting of simple mixing, drying, and carbonization processes. Thus, the well-designed composite structure effectively mitigates issues resulting from volumetric change of the Si during cycle and hence improves its performance significantly. The research results confirm outstanding performance of the Si@FeNO@P anode in the aspects of cycle durability, specific capacity, and rate capability, with 1116.1 (250th cycle), 858.1 (500th cycle), and 503.1 (500th cycle) mA h g-1 at 100, 1000, and 5000 mA g-1, respectively. By comparing the performance and structure of Si@FeNO@P with other control samples, it was substantiated that the outstanding performances of the Si@FeNO@P anode depend on the synergistic effects of the well-designed unique carbon matrix, conductive Fe3C, and Fe3O4-in situ derived metallic Fe nanoparticles during cycling. The outstanding electrochemical performance and simple preparation route make the Si@FeNO@P anode promising for lithium-ion battery applications. This work also gives useful insights into the development of high-performance Si-based anodes with simple practical methods.

Constructing Biomass-Based Ultrahigh-Rate Performance SnOy @C/SiOx Anode for LIBs via Disproportionation Effect

To break the stereotype that silica can only be reduced via a magnesiothermic and aluminothermic method at low-temperature condition, the novel strategy for converting silica to SiO_x using disproportionation effect of SnO generated via low-temperature pyrolysis coreduction reaction between SnO₂ and rice husk is proposed, without any raw materials waste and environmental hazards. After the low-temperature pyrolysis reaction, SnO_y @C/SiO_x composites with unique structure (Sn/SnO₂ dispersed on the surface and within pores of biochar as well as SiO_x residing in the interior) are obtained due to the exclusive biological properties of rice husk. Such unique structural features render SnO_y @C/SiO_x composites with an excellent talent for repairing the damaged structure and the highly electrochemical storage ability (530.8 mAh g^-1 at 10 A g^-1 after 7500 cycles). Furthermore, assembled LiFePO₄ ||SnO_y -50@C/SiO_x full cell displays a high discharge capacity of 463.7 mAh g^-1 after 100 cycles at 0.2 A g^-1 . The Li⁺ transport mechanism is revealed by density functional theory calculations. This work provides references and ideas for green, efficient, and high-value to reduce SiO₂ , especially in biomass, which also avoids the waste of raw materials in the production process, and becomes an essential step in sustainable development.

Design of LiFePO4 and porous carbon composites with excellent High-Rate charging performance for Lithium-Ion secondary battery

Lithium iron phosphate (LFP) is one of the promising cathode materials of lithium ion battery (LIB), but poor electrical conductivity restricts its electrochemical performance. Carbon coating can improve electrical conductivity of LFP without changing its intrinsic property. Uniform coating of carbon on LFP is significant to avoid charge congregation and unpreferable redox reactions. It is the first time to apply the commercial organic binder, Super P® (SP), as carbon source to achieve uniform coating on LFP as cathode material of LIB. The simple and economical mechanofusion method is firstly applied to coat different amounts of SP on LFP. The LIB with the cathode material of optimized SP-coated LFP shows the highest capacity of 165.6 mAh/g at 0.1C and 59.8 mAh/g at 10C, indicating its high capacity and excellent high-rate charge/discharge capability. SP is applied on other commercial LFP materials, M121 and M23, for carbon coating. Enhanced high-rate charge/discharge capabilities are also achieved for LIB with SP-coated M121 and M23 as cathode materials. This new material and technique for carbon coating is verified to be applicable on different LFP materials. This novel carbon coating method is expected to apply on other cathode materials of LIB with outstanding electrochemical performances.

A pre-oxidation strategy to improve architecture stability and electrochemical performance of Na2MnPO4F particles-embedded carbon nanofibers

The rational design of an excellent architecture for active materials combined with carbon matrix is of particular importanceto obtain flexible electrode material with high electrochemical properties. Well-designed nanofibers possess unique 3D network structure, which can significantly improve the electron/ion transportation and supplies sufficient active sites for Li⁺/Na⁺ insertion. Electrospinning-carbonization technology is a popular strategy to prepare nanofibers with active material embedded in carbon. It is found that the architecture of nanofibers tended to be wrecked and destroyed during the carbonization process without pre-oxidation treatment. In this study, we prepared Na₂MnPO₄F particles embedded in carbon nanofibers (Na₂MnPO₄F/C) using PVP as carbon source and investigated the strengthen mechanism of pre-oxidation on their architecture. The experiment and simulation results demonstrate that, without pre-oxidation, the main chain of PVP is severely ruptured during the carbonization procedure, consequently leads to fractured architecture of Na₂MnPO₄F/C nanofibers. In contrast, with pre-oxidation treatment, a long-chain and heat-resistance structured carbon matrix formed, and Na₂MnPO₄F/C nanofibers with stable architecture and improved electrochemical performance can be achieved. This study demonstrates a promising guide to construct carbon based nanofiber electrodes with stable architecture and high electrochemical performance.