Bipolar Polymeric Protective Layer for Dendrite-Free and Corrosion-Resistant Lithium Metal Anode in Ethylene Carbonate Electrolyte.

The unstable interface between Li metal and ethylene carbonate (EC)-based electrolytes triggers continuous side reactions and uncontrolled dendrite growth, significantly impacting the lifespan of Li metal batteries (LMBs). Herein, a bipolar polymeric protective layer (BPPL) is developed using cyanoethyl (-CH2CH2C≡N) and hydroxyl (-OH) polar groups, aiming to prevent EC-induced corrosion and facilitating rapid, uniform Li+ ion transport. Hydrogen-bonding interactions between -OH and EC facilitates the Li+ desolvation process and effectively traps free EC molecules, thereby eliminating parasitic reactions. Meanwhile, the -CH2CH2C≡N group anchors TFSI- anions through ion-dipole interactions, enhancing Li+ transport and eliminating concentration polarization, ultimately suppressing the growth of Li dendrite. This BPPL enabling Li|Li cell stable cycling over 750 cycles at 10 mA cm-2 for 2 mAh cm-2. The Li|LiNi0.8Mn0.1Co0.1O2 and Li|LiFePO4 full cells display superior electrochemical performance. The BPPL provides a practical strategy to enhanced stability and performance in LMBs application.

Ultrathin Carbon Sheet Obtained by Self-Template Method toward Highly Effective Charge Transfer for Si-Based Anodes.

A dynamic and stable charge transfer process is the key to exerting lithium storage characteristics of the silicon anode with a large volume change. In this work, the composite with an ultrathin carbon sheet skeleton is prepared by freeze-drying and a copyrolysis process after uniformly mixing citric acid and hydroxylated Si NPs, which is different from traditional conformal carbon coating derived from citric acid. A flexible carbon sheet reduces internal particle (Si-OH@NC) slip and cooperates with interfacial Si-O-C bonding to buffer machinal stress in the electrode during cycling. More importantly, the carbon sheet network increases the point-to-surface contact area between the active material and the conductive agent, ensures continuous electrical connection from the current collector to the active material, and promotes a rapid and stable electron transfer process. Besides, the N-doped C structure with remarkable nucleophilicity guarantees fast ion transport, which is confirmed by theoretical calculation. In this way, the reaction reversibility of the Si-based electrode is further realized during cycles. As a result, the electrode delivers excellent cycle performance (reversible capacity of 1001.9 mAh g-1 at 1 A g-1 after 500 cycles) and rate performance (capacity retention of 86.8 and 65.8% at 1 and 3 A g-1, respectively, compared to 0.2 A g-1). The idea of constructing a highly efficient electrode conductive network through a doped-carbon sheet network is also applicable to other active materials with huge volume changes during lithium storage.

Leaching characteristics and solidification strategy of heavy metals in solid waste from natural graphite purification.

The tailings and fluorine-containing sludge were produced during the physical and chemical purification of natural crystalline graphite, containing heavy metals in different occurrence forms. To evaluate the threat of different heavy metals to the environment, this work uses the modified sequential extraction method (BCR) to study the presence of heavy metals in two solid wastes and their dissolution characteristics in different environments. The results show that the pollution risk of heavy metals in graphite tailings to the environment is ranked as Mn > Cr > Ni > Zn, and the pollution risk of Mn in fluorine-containing sludge is higher than that of Cr. This is because the Mn in the two solid wastes mainly exists in the form of weak acid extraction. The leaching number of heavy metals in the two solid wastes is directly proportional to the soaking time and soaking temperature, and inversely proportional to the pH value and the solid-to-liquid ratio. The number of heavy metals dissolved in solid waste landfills is significantly higher than that of acid rain and surface water environments. Based on the above results and the distribution of graphite solid waste, solidification agent was suggested to prevent heavy metal dissolution and reduce environmental risks.

Constructing an artificial boundary to regulate solid electrolyte interface formation and synergistically enhance stability of nano-Si anodes.

Low coulombic efficiency and poor cyclic stability are two common problems for silicon anodes. Therefore, it is of great significance to improve cycling performance and initial coulombic efficiency (ICE) via rational surface engineering on nano-Si anodes. Herein, a new nano-silicon anode is obtained by straightforward constructing a multifunctional polypyrrole protective layer on the surface of silicon nanoparticles, which is further used as the inner boundary of solid electrolyte interface (SEI) film. Specifically, the Li salt decomposition reaction between the electrolyte and silicon surface is effectively inhibited under the protection of the compact artificial boundary. The transfer of Li+ for forming the SEI film is selectively slower than that of lithiation/delithiation reaction. This further reduces the amount of SEI film, leading to a high ICE of 93.2% at 0.5 A g-1 for modified nano-Si anodes. In addition, the flexible SEI precursor combined with the high proportion of organic components in SEIs not only accommodates the volume change of nano-silicon, but also suppresses accumulation of "waste SEI", so the electrode can maintain a reversible capacity of 1153.2 mAh g-1 at 1 A g-1 after 500 cycles. This work provides important guidance for surface structural optimization of alloy-type anodes with high volume change.

A flexible and conductive connection introduced by cross-linked CNTs between submicron Si@C particles for better performance LIB anode.

To improve the inevitable capacity fading issues faced by traditional submicron Si@C electrodes used as anode materials in LIBs, a flexible and conductive connection design is proposed and realized by a solid-state growth approach. In this construction, Si@C is entangled into in situ synthesized carbon nanotube-based network to form a highly connective Si@C/CNTs composite. The interwoven carbon-nanotubes having tight linkages with Si@C contribute to ensure the charge transfer pathway within Si@C particles and accommodate the volume expansion during cycling. The Co/N co-doping further facilitates the transportation of Li ions. As expected, the Si@C/CNT electrode shows improved conductivity and long-term cyclic stability with a high-capacity retention ratio of 80.7% after 500 cycles at 0.5 A g-1. In this study, the flexible and conductive connection design realized by the in situ synthesis of CNTs can provide some reference to the improvement of alloy-type anode materials and not just Si-based anode materials for LIBs.

Preparation of CaO-containing carbon pellet from recycling of carbide slag: Effects of temperature and H3PO4.

CaO-containing carbon pellets (CCCP) was prepared by mixing carbide slag (Ca(OH)2) and powdered char to produce CaC2, achieving the recycling of carbide slag during CaC2 production process. The thermal strength of CCCP was the focus of most attention when employing arc furnaces as reactors for CaC2 production in industry. To improve the thermal strength of CCCP, H3PO4 was used as a binder in this study. The results indicated that Ca3(PO4)2 reacted by H3PO4 and Ca(OH)2 could help refine the average particle sizes of CaO, resulted in a relatively uniform pore diameter distribution of CCCP with low porosity, therefore improving the thermal strength of CCCP. When H3PO4 content was more than 8 wt%, some over-sintering and melting structure for CaO particles appear, and thus resulting in the decrease in thermal strength of CCCP. The experimental results show that CCCP with 3% H3PO4 has the best thermal strength at 1100 °C. The non-isothermal shrinkage kinetics of CCCP indicated that the addition of 3% H3PO4 reduced the apparent activation energy of sintering reactions and accelerated the sintering of CaO particles in CCCP. Furthermore, the addition of H3PO4 has a positive effect on the formation of CaO sintered necks, enhancing the strength of CCCP.

Sulfur removal from bauxite water slurry (BWS) electrolysis intensified by ultrasonic.

Effects of ultrasonic on desulfurization ratio from bauxite water slurry (BWS) electrolysis in NaOH solution were examined under constant current. The results indicated that ultrasonic improved the desulfurization ratio at high temperatures because of the diffusion and transfer of oxygen gas in electrolyte. However, due to the increase in oxygen gas emission, ultrasonic could not improve the desulfurization ratio obviously at low temperatures. Additionally, the particle size of bauxite became fine in the presence of ultrasonic, indicating that the mass transfer of FeS2 phase was improved. According to the polarization curves, the current density increased in the presence of ultrasonic, indicating that the mass transfer of liquid phase was improved. The apparent activation energy (AAE) of electrode reaction revealed that ultrasonic did not change the pathway of water electrolysis. However, ultrasonic changed the pathway of BWS electrolysis, converting indirect oxidation into direct oxidation. The AAE of BWS electrolysis in the presence of ultrasonic was higher than that in the absence of ultrasonic. And the low AAEs (less than 20 kJ/mol) clearly indicated the diffusion control during BWS electrolysis reaction.

Comparative study of CeO2 and doped CeO2 with tailored oxygen vacancies for CO oxidation.

We report on the preparation and characterization of CeO(2) nanofibers (CeO(2)-NFs) and nanocubes (CeO(2)-NCs), as well as Sm- and Gd-doped CeO(2) nanocubes (Sm-CeO(2)-NCs and Gd-CeO(2)-NCs), synthesized by a simple hydrothermal process for CO catalytic oxidation. The samples were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Raman spectroscopy, and photoluminescence spectroscopy. Their oxygen-storing capacity (OSC) was examined by means of hydrogen temperature-programmed reduction (H(2)-TPR) and oxygen pulse techniques. Their catalytic properties for CO catalytic oxidation were comparatively investigated. The results showed that the CeO(2)-NFs possessed a higher catalytic activity compared to the CeO(2)-NCs because of their smaller size and the greater number of oxygen vacancies. The activity of the Sm-CeO(2)-NCs was higher than that of the CeO(2)-NCs due to an increase in the number of oxygen vacancies, which results from the substitution of Ce(4+) species with Sm(3+) ions. In contrast, Gd doping had a negative effect on the CO catalytic oxidation due to the special electron configuration of Gd(3+) (4f(7)). Our work demonstrates that the oxygen vacancies in pure CeO(2) and the electron configuration of the dopants in doped CeO(2) play an important role in CO oxidation.