Rational Assembly of Hollow Microporous Carbon Spheres as P Hosts for Long‐Life Sodium‐Ion Batteries

Abstract

have been considered as an alternative to lithium-ion batteries (LIBs) for largescale applications like smart grid energy storage. [1][2][3][4][5][6] Significant progress has been made in developing cathode materials for high-performance SIBs, such as layered transition metal oxides (Na x MeO 2 , Me = 3d transition metals), [7] polyanionic compounds, [8] and miscellaneous Na insertion materials. [9] The progress of designing efficient anode materials, however, has been relatively slow and finding proper ones is exigent because the commercial graphite anode for LIBs cannot be used to host the Na + ions whose diameter is ≈34% larger than Li + ions in the commonly used carbonate-based electrolytes. [10][11][12][13] Further, graphite has negligible capacities of 30-35 mA h g −1 in SIBs. [14,15] Although Si has been considered the most promising anode for LIBs, it holds very limited Na storage capacities at ambient temperature due to the unfavorable kinetics. [16][17][18] In view of the abovementioned reasons, it is crucial to identify anode materials that possess high capacities and long cyclic stability in SIBs. Benefiting from the high theoretical capacity of 2596 mA h g −1[19-23] by forming a highly reactive Na 3 P phase [24] and a safe working potential of ≈0.45 V versus Na/Na + , [25] phosphorus (P) has been considered a promising anode candidate for SIBs among many proposed materials. [26,27] Red P presents better chemical stability at room temperature and is commercially available at lower cost than other phosphorus allotropes, like white P, black P, [28] and violet P. [29] Nevertheless, most electrodes made from red P suffered low rate capacities, severe capacity reduction, and poor electrochemical reversibility, [19,21,30] which hindered the wide application of red P-based anodes. The following unfavorable reaction mechanisms are responsible for the poor electrochemical performance. (i) The extremely large volume expansion over 300% occurring when red P is transformed to Na 3 P phase causes pulverization of the active material and separation of red P from the current collectors, leading to rapid capacity deterioration. [23,[31][32][33] (ii) The electrically insulating amorphous red P whose electrical conductivity is ≈10 −14 S cm −1 results in large polarization and poor utilization of active material, [20,21,23,25,34] limiting the high-rate performance. (iii) The unstable, electronically insulating solid electrolyte This paper reports the rational assembly of novel hollow porous carbon nanospheres (HPCNSs) as the hosts of phosphorous (P) active materials for high-performance sodium-ion batteries (SIBs). The vaporization-condensation process is employed to synthesize P/C composites, which is elucidated by both theories and experiments to achieve optimized designs. The combined molecular dynamics simulations and density functional theory calculations indicate that the morphologies of polymeric P 4 and the P loading in the P/C composites depend mainly on the pore size and surface condition of carbon supports. M...

Porous Carbons: Structure‐Oriented Design and Versatile Applications

“…Similarly adopting pyrrole–aniline copolymer as the carbon source and Triton X‐100 as the soft template, hollow microporous carbon spheres with abundant micropores (1–2 nm in diameter) were generated after carbonization removal of Triton X‐100 tails. [ 263 ] Theoretical studies denoted that the oxygenated functional groups and micropores would positively boost both P loading and structure stability of carbon/P composite, which showed excellent electrochemical performance as an electrode material for sodium‐ion battery.…”

Mild‐Temperature Solution‐Assisted Encapsulation of Phosphorus into ZIF‐8 Derived Porous Carbon as Lithium‐Ion Battery Anode

“…A general strategy is to physically deposit RP in the carbon hosts via an evaporation/condensation process. [ 5–19 ] Note that a necessary high temperature of 500–900 °C is commonly applied in order to ensure the conversion of the bulk RP into the gas phase. In this process, RP sublimates and diffuses in the carbon hosts and finally form a carbon/RP composite.…”

“…[ 5 ] Moreover, the unstable, toxic, and flammable white phosphorus will also generate accompanied with the evaporation/condensation process, generally requiring further annealing thereafter washing with toxic CS 2 . [ 5–19 ] Recently, a solution‐processed encapsulation method has been developed to facilitate the formation of RP nanoparticles inside MWCNTs and meanwhile allow the easy removal of the external phosphorus anchored on the outer wall of MWCNTs because this solution‐based process avoids the formation of crystalline RP, and finally the phosphorus@MWCNTs hybrids exhibited a significantly improved cycling stability. [ 20 ]…”

“…So far, CNTs/MWCNTs, [ 5–9 ] graphene, [ 9–13 ] carbon nanofibers, [ 14,15 ] and some carbonaceous materials derived from biomass and organic precursors have been reported as porous carbon hosts for loading RP. [ 14–19 ] Among them, metal–organic frameworks (MOFs) derived porous carbons have attracted much interest due to their outstanding advantages such as controllable and high porosity, good thermal/chemical stability, high electrical conductivity, as well as easy modification with other elements and materials, etc. [ 21–24 ] Especially in the case of porous carbons derived from zinc‐based MOFs, their porosity can be further increased by evaporating the reduced zinc at an operationally feasible boiling point, which would enable to load more RP to improve the mass loading and thus the corresponding energy density.…”

Carbon‐Based Alloy‐Type Composite Anode Materials toward Sodium‐Ion Batteries

“…Hollow microporous carbon spheres (HMCS) has been also recruited as host to confine the RP as an anode for SIBs, which theoretically and experimentally exhibited good electrochemical performance as well as extremely low volume expansion of ≈67.3% during cycles . The authors also suggested that the porous structure was favorable for increasing the loading amount of RP.…”