Current status of research on composite bipolar plates for proton exchange membrane fuel cells (PEMFCs): nanofillers and structure optimization.

The proton exchange membrane fuel cell (PEMFC) is an efficient and clean energy source with promising applications. However, drawbacks such as high cost and low durability limit its application. Bipolar plates are an important component of PEMFCs, which not only account for a large proportion of the price and quality, but also affect the performance and durability of PEMFCs. Unlike traditional graphite and metal bipolar plates, composite bipolar plates have the advantages of easy processing, low cost, and corrosion resistance, but their lower performance limits their practical applications. This paper firstly summarizes the current research progress of various nanofillers used to improve the performance of composite bipolar plates, and discusses the improvement of the performance of composite bipolar plates by different forms and types of nanofillers. The morphological characteristics of different types of nanofillers and their effects on the improvement of conductive pathways are also analyzed. Subsequently, the means of structural optimization of composite bipolar plates are summarized, and specific optimization methods for phase interface, graphite/resin dispersion morphology, and conductive network structure are discussed in detail. Finally, challenges are discussed. Overall, this review can provide a reference for future research on composite bipolar plates.

The fabrication of silicon/dual-network carbon nanofibers/carbon nanotubes as free-standing anodes for lithium-ion batteries.

Silicon, known for its high theoretical capacity and abundant resources, is regarded as one of the most promising anode materials for lithium-ion batteries (LIBs). However, the application of silicon anode materials is limited by huge expansion and poor electricity of silicon. Herein, a novel free-standing Si/C anode (noted as Si/CNFs/CNTs) is synthesized by combining electrospinning and in situ chemical vapor deposition, in which Si nanoparticles are composited with a conducting dual-network composed of carbon nanofibers (CNFs) and in situ deposited carbon nanotubes (CNTs). In situ deposited CNTs surround the surface of CNFs to form an elastic buffer layer on the surface of Si attached to CNFs, which ensures structural integrity. CNTs with excellent conductivity and a large specific surface area shorten Li+ transport pathways. Therefore, Si/CNFs/CNTs exhibits stable cycling performance and maintains a capacity of 639.9 mA h g-1 and a capacity retention rate of 69.9% after 100 cycles at a current density of 0.1 A g-1. This work provides a promising approach for the structural modification of self-supporting Si/C electrodes.