Ab Initio Study of Phosphorus Anodes for Lithium- and Sodium-Ion Batteries

Abstract

Phosphorus has received recent attention in the context of high-capacity and high-rate anodes for lithium and sodium-ion batteries. Here, we present a first principles structure prediction study combined with NMR calculations which gives us insights into its lithiation/sodiation process. We report a variety of new phases phases found by AIRSS and the atomic species swapping methods. Of particular interest, a stable Na 5 P 4 -C2/m structure and locally stable structures found less than 10 meV/f.u. from the convex hull, such as Li 4 P 3 -P2 1 2 1 2 1 , NaP 5 -Pnma and Na 4 P 3 -Cmcm. The mechanical stability of Na 5 P 4 -C2/m and Li 4 P 3 -P2 1 2 1 2 1 has been studied by first principles phonon calculations . We have calculated average voltages which suggests that black phosphorus (BP) can be considered as a safe anode in lithium-ion batteries due to its high lithium insertion voltage, 1.5 V; moreover, BP exhibits a relatively low theoretical volume expansion compared with other intercalation anodes, 216% (∆V /V ). We identify that specific ranges in the calculated shielding can be associated with specific ionic arrangements, results which play an important role in the interpretation of NMR spectroscopy experi- * ments. Since the lithium-phosphides are found to be insulating even at high lithium concentrations we show that Li-P-doped phases with aluminium have electronic states at the Fermi level suggesting that using aluminium as a dopant can improve the electrochemical performance of P anodes.

In Situ Visualization of Interfacial Sodium Transport and Electrochemistry between Few‐Layer Phosphorene

“…Both the HRTEM image and the FFT pattern have verified the generation of the stable orthorhombic NaP‐ P21/c phase at this stage. For higher sodium concentrations, the Na–P structures are formed by isolated P ions, which ultimately leads to the formation of an amorphous structure, that is, Na 3 P matrix (Figure i). Although the alloying reactions of few‐layer phosphorene with sodium have been widely studied though theoretical and experimental calculations, there is currently a lack of direct evidence.…”

“…For higher sodium concentrations, the Na–P structures are formed by isolated P ions, which ultimately leads to the formation of an amorphous structure, that is, Na 3 P matrix (Figure i). Although the alloying reactions of few‐layer phosphorene with sodium have been widely studied though theoretical and experimental calculations, there is currently a lack of direct evidence. The present observations not only disclose the interfacial electrochemistry between solid–solid electrodes, but also clarify the whole reaction mechanism of few‐layer phosphorene with sodium.…”

Alloy‐Based Anode Materials toward Advanced Sodium‐Ion Batteries

“…As a result, the low initial reversible specific capacity along with the fast capacity fading of BP nanosheets for SIBs hinders its future application significantly. [153,154,[175][176][177][178][179] As we discussed above, the further strategies could focus on developing the BPcarbon composites similar to RP, surface engineering of BP nanosheets with enhanced electrical conductivity, choosing proper electrolyte additives and binders, and so on. [162] It exhibited a high specific capacity of 2440 mA h g −1 at 0.05 A g −1 with 83% capacity retention after 100 cycles (Figure 8d).…”

Post‐Graphene 2D Chemistry: The Emerging Field of Molybdenum Disulfide and Black Phosphorus Functionalization

“…In contrast to graphite,w here the intercalation of guest systems,s uch as alkali metals or small inorganic molecules between the graphene sheets yields al arge variety of intercalation compounds,t hat have been investigated in great detail for many years, [58b,59, 60] the field of BP intercalation compounds (BPICs) [79] (Figure 14) remained almost completely unexplored for along time. [80] It is clear that the interfacial spacing between two individual BP layers with about 5.23 is roughly 2 larger than that in graphite and this provides an ideal prerequisite for the uptake of small guest systems.T heoretical investigations [81] on BPICs have shown exciting opportunities for developing high capacity sodium or lithium ion batteries with up to about 2600 mAh g À1 outperforming graphite-based LIBs.F or the intercalation of lithium (Li)i nto FL-BP, superconductivity with a T c of 16.5 Kh as been predicted. [82] Tw of amilies of BPICs are especially attractive,n amely 1) AM-BPICs (AM = alkali metal) and 2) BPICs containing small molecules.T heoretical calculations have predicted that in Na-BPICs the layered structure of BP remains intact up to amaximum loading stoichiometry of 0.25 equiv sodium (Na) relative to P. [83] Very recently,some experimental evidence on BPICs was obtained by in situ TEM.…”