Anhua Liu

Poor intrinsic conductivity and the presence of irreversible lithiation phase affect the electrochemical performance of silicon oxycarbide anode materials. Even though it can be improved by increasing free carbon content or composition, scarification of reversible capacity and initial Coulombic efficiency (ICE) remain as challenge. Here, polycarbosilane (PCS) with alternating distribution of silicon and carbon atoms is employed as precursor of SiOC ceramics. Air oxidation cross‐linking is used to regulate the content of oxygen and carbon elements in PCS at atom level, so as to explore a solution to improve the intrinsic conductivity and reversible lithium phase content of SiOC ceramics. This strategy provides extremely excellent rate capability, areal/volumetric capacity, and ICE. This is also the first concept for feasible precursor structure design to control the SiOC glass phase and regulate the growth of C nanoribbon that can improve the intrinsic conductivity and reversible capacity of SiOC ceramic anode materials.

Continuous Fe-SiC fibers with the highest Fe content of 7.70 wt% were successfully fabricated and exhibit excellent EMW absorbing performance. The microstructure of Fe-SiC fibers possesses SiC crystallites, turbostratic carbon, and Fe_xSi_y@C.

Severe volume expansion and inherently poor lithium ion transmission are two major problems of silicon anodes. To address these issues, we proposed a pomegranate-type Si/C composite anode with highly dispersed tiny silicon particles as the core assisted by small amount of SiC. Skillfully exploiting the high heat from magnesiothermic reduction, SiC can assist the good dispersion of silicon and provide good interface compatibility and chemical stability. The silicon anchored to the carbon shell provides multipoint contact mode, that together with the carbon shell frame, significantly promoting the transfer of dual charge. Besides, the pomegranate-type microcluster structure also improves the tap density of the electrode, reduces the direct contact area between active material and electrolyte, and enhances the electrochemical performance.

Silicon is considered as the desirable anode material for lithium‐ion batteries due to its suitable discharge potential, abundant reserve, and ultra‐high specific capacity. However, poor conductivity and unstable battery performance caused by large volume change during cycling limit the further development of silicon anode. In order to avoid the unstable solid electrolyte interface layer caused by the direct contact between silicon and electrolyte, and to eliminate the structural collapse caused by the volume change during cycling, dimension size reduction, reserved voids, and novel structural framework are usually adopted. Although these methods can effectively improve the defects, a new problem is introduced and cannot be ignored: contact engineering between the coating layer and silicon core. Herein, contact engineering is classified into three categories: face to face (F2F), line to line (L2L), and point to point (P2P) according to the contact modes between the coating and core. There is utilizability of the structure categories of different contact modes and their influence on electrochemical performance. Therefore, in the future research of silicon anode, contact engineering is a non‐negligible aspect in the structural design process. Finally, feasible strategies based on contact engineering have been indicated.

In order to enhance dielectric properties of polymer-derived SiC ceramics, a novel single-source-precursor was synthesized by the reaction of an allylhydrido polycarbosilane (AHPCS) and divinyl benzene (DVB) to form carbon-rich SiC. As expected, the free carbon contents of resultant SiC ceramics annealed at 1600 °C are significantly enhanced from 6.62 wt% to 44.67 wt%. After annealing at 900–1600 °C, the obtained carbon-rich SiC ceramics undergo phase separation from amorphous to crystalline feature where superfine SiC nanocrystals and turbostratic carbon networks are dispersed in an amorphous SiC(O) matrix. The dielectric properties and electromagnetic (EM) absorption performance of as-synthesized carbon-rich SiC ceramics are significantly improved by increasing the structural order and content of free carbon. For the 1600 °C ceramics mixed with paraffin wax, the minimum reflection coefficient (RC_min) reaches –56.8 dB at 15.2 GHz with the thickness of 1.51 mm and a relatively broad effective bandwidth (the bandwidth of RC values lower than –10 dB) of 4.43 GHz, indicating the excellent EM absorption performance. The carbon-rich SiC ceramics have to be considered as harsh environmental EM absorbers with excellent chemical stability, high temperature, and oxidation and corrosion resistance.

In this work, porous core‐shell structured Co ₂ Si@SiC/C/SiOC/SiO ₂ /Co ₃ O ₄ nanoparticles were fabricated by a polymer‐derived ceramic approach. The in situ formation of mesopores on the shell, microstructural, and phase evolution of resulting nanoparticles were investigated in detail. The obtained nanoparticles‐paraffin composites possess a very low minimum reflection coefficient (RC _min ) −60.9 dB, broad effective absorption bandwidth 3.50 GHz in the X‐band and 15.5 GHz in the whole frequency range (from 2.5 to 18 GHz). The results indicate outstanding electromagnetic wave (EMW) absorbing performance among all the reported cobalt‐based nanomaterials, due to the reasons as follows: (a) The unique core‐shell structure as well as complex phase composition of SiC/C/SiOC/SiO ₂ /Co ₃ O ₄ in the shell, result in a large number of heterogeneous interfaces in the nanoparticles; (b) Nanoparticles have both dielectric and magnetic loss; (c) Mesopores in the shell prolong the propagation path of EMW, thereby increasing the absorption/reflection ratio of EMWs. Thanks to the material structure design, the resulting core‐shell structured cobalt‐containing ceramic nanoparticles have great potential for thin and high‐performance EMW absorbing materials applied in harsh environment.