Al2O3 coated LiCoO2 as cathode for high-capacity and long-cycling Li-ion batteries

High-efficiency carbon-coated steel wool filter for controlling cooking-induced oil smoke

Cooking oil smoke (COS) contains many harmful substances, such as particulate matter, formaldehyde, and phenyl esters. Currently, commercial COS treatment equipment is expensive and requires a large space. Furthermore, a large amount of agricultural waste is generated and is mainly burned onsite, producing large amounts of greenhouse gases and air pollutants. This waste could be reused as a precursor for biochar and activated carbon. Therefore, this research used saccharification and catalytic hydrothermal carbonization to process rice straw and produce compact carbon-based filters (steel wool-C) for removing cooking-induced pollutants. Scanning electron microscopy indicated that carbon layers were coated on the steel wool. The Brunauer-Emmett-Teller surface area of the carbon filter was 71.595 m2/g, 43 times larger than that of steel wool. The steel wool filter removed 28.9%-45.4% of submicron aerosol particles. Adding a negative air ionizer (NAI) to the filter system enhanced the particle removal efficiency by 10%-25%. The removal efficiency of total volatile organic compounds was 27.3%-37.1% with the steel wool filter, but 57.2%-74.2% with the carbon-containing steel wool filter, and the NAI improved the removal efficiency by approximately 1%-5%. The aldehyde removal efficiency of the carbon filter with NAI was 59.0%-72.0%. Conclusively, the compact steel wool-C and NAI device could be promising COS treatment equipment for households and small eateries.

High-Performance Amorphous Carbon Coated LiNi0.6Mn0.2Co0.2O2 Cathode Material with Improved Capacity Retention for Lithium-Ion Batteries

Coating conducting polymers onto active cathode materials has been proven to mitigate issues at high current densities stemming from the limited conducting abilities of the metal-oxides. In the present study, a carbon coating was applied onto nickel-rich NMC622 via polymerisation of furfuryl alcohol, followed by calcination, for the first time. The formation of a uniform amorphous carbon layer was observed with scanning- and transmission-electron microscopy (SEM and TEM) and X-ray photoelectron spectroscopy (XPS). The stability of the coated active material was confirmed and the electrochemical behaviour as well as the cycling stability was evaluated. The impact of the heat treatment on the electrochemical performance was studied systematically and was shown to improve cycling and high current performance alike. In-depth investigations of polymer coated samples show that the improved performance can be correlated with the calcination temperatures. In particular, a heat treatment at 400 °C leads to enhanced reversibility and capacity retention even after 400 cycles. At 10C, the discharge capacity for carbon coated NMC increases by nearly 50% compared to uncoated samples. This study clearly shows for the first time the synergetic effects of a furfuryl polymer coating and subsequent calcination leading to improved electrochemical performance of nickel-rich NMC622.

Revealing the Fast and Durable Na+ Insertion Reactions in a Layered Na3Fe3(PO4)4 Anode for Aqueous Na-Ion Batteries

Aqueous sodium-ion batteries represent a promising approach for stationary energy storage; however, the lack of appropriate anode materials has substantially retarded their development. Herein, we demonstrated an iron-based phosphate material of Na₃Fe₃(PO₄)₄ as an inexpensive and efficacious anode alternative. While the Fe³⁺/Fe²⁺ redox couple renders a two-Na-insertion reaction with desirable potentials, its unique layered structure further facilitates the Na-insertion kinetics and reversibility. Consequently, this electrode exhibits an appealing Na-insertion performance, with a reversible capacity of ∼83 mAh g^-1, suitable anode potential of -0.4 V vs Ag/AgCl, excellent rate capability of 200 C, and outstanding cycling of 6000 cycles. Utilizing operando synchrotron X-ray diffraction and X-ray absorption spectroscopy, we revealed the structural evolution of the Na₃Fe₃(PO₄)₄ anode during the two-electron reaction, where the extremely small volume expansion (∼3%) enables its fast-charging and long-cycling capability. Our work suggests new considerations of developing versatile iron phosphate compounds as appealing anode materials for energy storage in aqueous electrolytes.

Interfacial processes in electrochemical energy systems

Electrochemical energy systems such as batteries, water electrolyzers, and fuel cells are considered as promising and sustainable energy storage and conversion devices due to their high energy densities and zero or negative carbon dioxide emission. However, their widespread applications are hindered by many technical challenges, such as the low efficiency and poor long-term cyclability, which are mostly affected by the changes at the reactant/electrode/electrolyte interfaces. These interfacial processes involve ion/electron transfer, molecular/ion adsorption/desorption, and complex interface restructuring, which lead to irreversible modifications to the electrodes and the electrolyte. The understanding of these interfacial processes is thus crucial to provide strategies for solving those problems. In this review, we will discuss different interfacial processes at three representative interfaces, namely, solid-gas, solid-liquid, and solid-solid, in various electrochemical energy systems, and how they could influence the performance of electrochemical systems.

Effect of Fluence and Multi-Pass on Groove Morphology and Process Efficiency of Laser Structuring for 3D Electrodes of Lithium-Ion Batteries

Lithium-ion batteries (LIBs) are widely used as energy storage systems. With the growing interest in electric vehicles, battery performance related to traveling distance has become more important. Therefore, there are various studies going on to achieve high-power and high-energy batteries. Laser structuring of electrodes involves a groove being produced on electrodes by a laser. This technique was used to show that battery performance can be enhanced due to improving Li-ion diffusion. However, there is a lack of studies about the morphological variation of grooves and process efficiency in laser parameters in the laser structuring of electrodes. In this study, the LiFePO4 cathode is structured by a nanosecond laser to analyze the morphological variation of grooves and process efficiency depending on laser fluence and the number of passes. First, the various morphologies of grooves are formed by a combination of fluences and the number of passes. At a fluence of 0.86 J/cm2 and three passes, the maximum aspect ratio of 1.58 is achieved and the surface area of structured electrodes is greater than that of unstructured electrodes. Secondly, three ablation phenomena observed after laser structuring are classified according to laser parameters through SEM images and EDX analysis. Finally, we analyze the amount of active material removal and process efficiency during laser structuring. In conclusion, applying low fluence and multi-pass is assumed to be advantageous for laser structuring of electrodes.

An Al2O3 coating layer on mesoporous Si nanospheres for stable solid electrolyte interphase and high-rate capacity for lithium ion batteries

The application of Si-based anode materials is hindered by their extreme volume change, poor cycling stability, and low coulombic efficiency. Solving these problems generally requires a combination of strategies, such as nanostructure designing or surface coating. However, these strategies increase the difficulty of the fabrication process. Herein, a simple and one-pot replacement reaction route was designed to produce an Al2O3 layer anchored on mesoporous Si nanospheres (Si@Al2O3) by employing Al nanospheres with a naturally formed Al2O3 layer as a reducing agent and self-sacrificial template. The obtained Si@Al2O3 was mesoporous, with enough porous space to buffer the volume change and provide a fast lithium ion transfer channel. Furthermore, the coated Al2O3 layer could stabilize the structure and SEI layer of the mesoporous Si nanospheres, endowing the Si@Al2O3 nanospheres with improved initial coulombic efficiency, cycling performance and rate capability. As a result, a high capacity of 1750.2 mA h g-1 at 0.5 A g-1 after 120 cycles and 1001.7 mA h g-1 at 2 A g-1 after 500 cycles were delivered for lithium ion batteries. The good performance could be attributed to the mesoporous structure and the outer-coated Al2O3 layer.