ABSTRACT
With the expectation of the rapid depletion of conventional fossil fuels and, exponentially, the ever-increasing global demands on energy, recently there has been growing interest in developing alternative technologies for green (zero emissions) energy storage and conversion devices such as batteries, supercapacitors, fuel cells, and solar cells for transportation, stationary power, and distributed power generation applications. Compared to fuel cells, which require a constant supply of fuels and oxidants, batteries and supercapacitors can be completely self-contained, only requiring an occasional supply of chemical input or export across their entire lifetime. However, 52batteries have gained greater attention than supercapacitors due to their high energy density, constant output voltage, and very low self-discharge. Similar to other electrochemical devices, batteries also consist of three basic components viz., an electrolyte, which allows the transfer of ions from the negative (anode) to the positive (cathode) electrode during discharge, facilitating the continuous flow of electrons through an external circuit. During charging, the opposite reaction takes place with ions moving in the opposite direction, and the use of electrical energy pushes the electrons and ions back to the anode where they are stored in the galleries of the layered anode. Among the different battery technologies such as lead-acid, nickel-cadmium, and nickel-metal hydride batteries, so far, Li-ion batteries (LIBs) have exhibited the highest volumetric and gravimetric energy densities, with very low self-discharge and good power density [1–4]. Hence, during the past decades, lithium-ion batteries have gained much attention from the electronics industry and have become the primary power source for electronic gadgets [5–9]. However, to date, LIBs have suffered from serious safety issues, including the flammability of typical organic liquid electrolytes, which has caused serious incidents such as catching fire due to the thermal runway resulting from the failure of the electrolyte [10,11]. Compared to portable electronic devices, this is a particularly serious concern for hybrid/electrical vehicles and stationary power banks. Recent incidents in a unit of the Tesla Model S and the Boeing 787 Dreamliner airplane (fires in lithium-ion batteries) have impelled a mandatory safety policy on rechargeable lithium-ion batteries [12].
