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 found by the ab initio random structure searching (AIRSS) and the atomic species swapping methods. Of particular interest, a stable Na5P4–C2/m structure and locally stable structures found less than 10 meV/f.u. from the convex hull such as Li4P3–P212121, NaP5–Pnma, and Na4P3–Cmcm. The mechanical stability of Na5P4–C2/m and Li4P3–P212121 has been studied by first-principles phonon calculations. We have calculated average voltages, which suggest 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, 2...
Highlights
Owing to their relatively high specific energy and capacity, Liion batteries (LIBs) are the energy source of choice for portable electronic devices.[1]
The stable structures found on the convex hull, in increasing lithium concentration order, are black phosphorus (BP)−Cmca, LiP7−I41/acd,[54] Li3P7−P212121,55 LiP−P21/c,56 Li3 P−P63/mmc,[57] and Li−Im3̅m
All the known Li−P phases are found on the convex hull, except for LiP5 −Pna[21,54] which is found 12 meV/ f.u. from the convex tie-line in our 0 K density-functional theory (DFT) calculation
Summary
Owing to their relatively high specific energy and capacity, Liion batteries (LIBs) are the energy source of choice for portable electronic devices.[1]. Ni, Mn, Intercalation electrodes experience slight changes during charge and discharge, for example, less than 7% volume change in C negative electrodes[3] leading to a high capability of retaining their capacity over charge/discharge cycles. These electrodes suffer from low specific capacity due to the limited intercalation sites available for Li ions in the host lattice,[5] for example, 372 mAhg−1 for graphite. To overcome the capacity limitation of intercalation anodes, it has been suggested to use different alloys of lithium as LIB anodes.[3,5−9] A wide range of materials have been studied for this purpose such as group IV and V elements, magnesium, aluminum, and gallium among others.[3,7] Alloy materials can achieve 2−10 times higher capacity compared to graphite anodes, where the highest capacity is achieved by silicon, 3579 mAhg−1.10 alloys tend to undergo relatively large structural changes under lithiation,[2,3,7,10] leading to a poor cycle life
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