Intensive research effort is currently focused on the development of efficient, reliable, and environmentally safe electrochemical energy storage systems due to  the ever-increasing global energy storage demand. Li ion battery systems have been used as the primary energy storage device over the last three decades. However, low abundance and uneven distribution of lithium and cobalt in the earth crust and the associated cost of these materials, have resulted in a concerted effort to develop beyond lithium electrochemical storage systems. In the case of non-Li ion rechargeable systems, the development of electrode materials is a significant challenge, considering the larger ionic size of the metal-ions and slower kinetics. Two-dimensional (2D) materials, such as graphene, transition metal dichalcogenides, MXenes and phosphorene, have garnered significant attention recently due to their multi-faceted advantageous properties: large surface areas, high electrical and thermal conductivity, mechanical strength, etc. Consequently, the study of 2D materials as negative electrodes is of notable importance as emerging non-Li battery systems continue to generate increasing attention. Among these interesting materials, graphene has already been extensively studied and reviewed, hence this report focuses on 2D materials beyond graphene for emerging non-Li systems. We provide a comparative analysis of 2D material chemistry, structure, and performance parameters as anode materials in rechargeable batteries and supercapacitors.

Development of efficient electrochemical energy storage systems with high energy and power densities coupled with minimal carbon footprint is an important technological challenge. One vital aspect in this regard is the correct choice of electrode material, as its properties (chemical, electrical) and assorted aspects (availability, processability) strongly influence the performance of the electrochemical system. Significant research has gone into developing novel electrode materials for the various electrochemical systems (Li-ion and other metal-ion rechargeable batteries, supercapacitors, etc); however, in most cases, it is hard to identify a single electrode material that works suitably well across all systems. Molecular precursor or polymer derived ceramics (PDCs), because of their amorphous nanodomain structure, processing flexibility, easy availability of precursors, and tunable electrochemical properties, are promising candidates as electrode materials for a range of electrochemical energy storage devices. With progressive research, as more information is garnered about the relationship between PDC molecular structure and electrochemical behavior, it is expected that PDC-based materials will make a significant impact on the development of the next generation of high capacity, energy efficient batteries and supercapacitors. This article therefore looks to provide a detailed discussion of the properties of PDCs and their status as energy storage materials, along with the challenges that lie ahead.

Electrospinning of ceramic mats for high temperature applications.

Ceramics derived from organic polymer precursors, which have exceptional mechanical and chemical properties that are stable up to temperatures slightly below 2000 °C, are referred to as polymer-derived ceramics (PDCs). These molecularly designed amorphous ceramics have the same high mechanical and chemical properties as conventional powder-based ceramics, but they also demonstrate improved oxidation resistance and creep resistance and low pyrolysis temperature. Since the early 1970s, PDCs have attracted widespread attention due to their unique microstructures, and the benefits of polymeric precursors for advanced manufacturing techniques. Depending on various doping elements, molecular configurations, and microstructures, PDCs may also be beneficial for electrochemical applications at elevated temperatures that exceed the applicability of other materials. However, the microstructural evolution, or the conversion, segregation, and decomposition of amorphous nanodomain structures, decreases the reliability of PDC products at temperatures above 1400 °C. This review investigates structure-related properties of PDC products at elevated temperatures close to or higher than 1000 °C, including manufacturing production, and challenges of high-temperature PDCs. Analysis and future outlook of high-temperature structural and electrical applications, such as fibers, ceramic matrix composites (CMCs), microelectromechanical systems (MEMSs), and sensors, within high-temperature regimes are also discussed.