Demand for energy in day to day life is increasing exponentially. However, existing energy storage technologies like lithium ion batteries cannot stand alone to fulfill future needs. In this regard, potassium ion batteries (KIBs) that utilize K ions in their charge storage mechanism have attracted considerable attention due to their unique properties and are therefore established as one of the future battery systems of interest among the scientific community. Nevertheless, the development and identification of appropriate electrode materials is very essential for practical applications. This review features the current development in KIBs electrode and electrolyte materials, the present challenges facing this technology (in the commercial aspect), and future aspects to develop fully functional KIBs. The potassium storage mechanisms, evolution of the KIBs, and the advantages and disadvantages of each category of materials are included. Additionally, various approaches to enhance the electrochemical performances of KIBs are also discussed. This review is not only an amalgamation of different viewpoints in literature, but also contains concise perspectives and strategies. Moreover, the potential emergence of a novel class of K‐based dual ion batteries is also analyzed for the first time.

A yolk-shell-structured carbon@void@silicon (CVS) anode material in which a void space is created between the inside silicon nanoparticle and the outer carbon shell is considered as a promising candidate for Li-ion cells. Untill now, all the previous yolk-shell composites were fabricated through a templating method, wherein the SiO2 layer acts as a sacrificial layer and creates a void by a selective etching method using toxic hydrofluoric acid. However, this method is complex and toxic. Here, a green and facile synthesis of granadillalike outer carbon coating encapsulated silicon/carbon microspheres which are composed of interconnected carbon framework supported CVS nanobeads is reported. The silicon granadillas are prepared via a modified templating method in which calcium carbonate was selected as a sacrificial layer and acetylene as a carbon precursor. Therefore, the void space inside and among these CVS nanobeads can be formed by removing CaCO3 with diluted hydrochloric acid. As prepared, silicon granadillas having 30% silicon content deliver a reversible capacity of around 1100 mAh g−1 at a current density of 250 mA g−1 after 200 cycles. Besides, this composite exhibits an excellent rate performance of about 830 and 700 mAh g−1 at the current densities of 1000 and 2000 mA g−1, respectively. (≈4200 mAh g −1 ), relatively low discharge potential (≈0.5V vs Li/Li + ), abundance, and environmental benignity. [1][2][3][4][5][6] However, the dramatic volume change (>300%) during lithiation and delithiation processes leads to severe pulverization and continual formation of solid electrolyte interphase (SEI) on the newly formed silicon surfaces, resulting in a large capacity loss. [7][8][9][10][11] Therefore, the cycling performance of silicon-based anodes is still far from satisfactory from a commercial point of view. [ 12 ] Silicon nanoparticles (Si NPs) have been found to tolerate extreme changes in volume with cycling. [ 13 ] Hence, great efforts have been made to improve the cycling stability and electrical conductivity by using various Si-based nanostructures, including Si nanowires, [ 3,14,15 ] porous Si, [16][17][18][19] and conductive agent coated Si such as carbon, [ 18,20,21 ] Ag, [ 22,23 ] and conducting polymer. [ 24 ] Among them, a yolkshell-structured carbon@void@silicon (CVS) composite [ 25,26 ] is quite promising for practical applications, because the void space between the outer carbon shell and the inside Si NP allows the room for volume changes of Si NP without deforming the carbon shell and SEI fi lm, which in turn allows for the growth of a stable SEI on the surface of the outer carbon shell. [ 26 ] Besides, the homogeneous carbon coating shell can prevent the electrolyte ingress and the direct contact of Si NPs with the electrolyte, so the SEI will only be formed on the outer surface of the carbon shell, leading to the high Coulombic effi ciency and improved cycling stability. [ 25 ] For instance, Cui and co-workers achieved a high capacity of ≈2800 mAh g −1 with a very good cycling s...

The methodology employed here utilizes the sodium super ion conductor type sodium iron phosphate wrapped with conducting carbon network to generate a stable Fe /Fe redox   couple, thereby exhibiting higher operating voltage and energy density of sodium-ion batteries. This new class of sodium iron phosphate wrapped by carbon also displays a cycling stability with >96% capacity retention after 200 cycles.

Organic materials offer a new opportunity to develop high-performance, low-cost, environmentally benign sodium ion batteries. This review provides insights into the different sodium storage mechanisms in various categories of organic materials.