  Sodium ion batteries become popular due to their low cost. Among possible
anode materials of sodium ion batteries, phosphorus has great potential owing
to its high theoretical capacity. Previous research that yielded high capacity
and long duration of phosphorus anode used expensive materials such as black
phosphorus (BP) and phosphorene. To take advantage of the low cost of sodium
ion batteries, we report a simple and low-cost method to fabricate anode:
condensing red phosphorus on carbon xerogel. Even with large particle size (~
50 $\mu$m) and high mass loading (2 mg cm$^{-2}$), the composite cycled at 100
mA g$^{-1}$ yielded a capacity of 357 mA g$^{-1}$ or 2498 mAh g$^{-1}_P$ based
on phosphorus after subtracting the contribution of carbon. The average
coulombic efficiency is as high as 99.4%. When cycled at 200 mA g$^{-1}$, it
yielded a capacity of 242 mAh g$^{-1}$ or 1723 mAh g$^{-1}_P$, with average
degradation rate only 0.06% in 80 cycles. Our research provided an innovative
approach to synthesize anodes for sodium ion batteries at extremely low cost,
with performance exceeding or comparable to state-of-the-art materials, which
will promote their commercialization.
