The electrochemical behaviour of a Sn-based anode in a potassium cell is reported for the first time. The material is active at low potentials vs. K/K⁺, and encouraging capacities of around 150 mA h g⁻¹ are recorded. Experimental evidence shows that Sn is capable of alloying/de-alloying with potassium in a reversible manner.

With the expected theoretical capacity of 2596 mA h g⁻¹, phosphorus is considered to be the highest capacity anode material for sodium-ion batteries and one of the most attractive anode materials for lithium-ion systems. This work presents a comprehensive study of phosphorus–carbon nanocomposite anodes for both lithium-ion and sodium-ion batteries. The composite electrodes are able to display high initial capacities of approximately 1700 and 1300 mA h g⁻¹ in lithium and sodium half-cells, respectively, when the cells are tested within a larger potential windows of 2.0–0.01 V vs. Li/Li⁺ and Na/Na⁺. The level of demonstrated capacity is underpinned by the storage mechanism, based on the transformation of phosphorus to Li₃P phase for lithium cells and an incomplete transformation to Na₃P phase for sodium cells. The capacity deteriorates upon cycling, which is shown to originate from disintegration of electrodes and their delamination from current collectors by post-cycling ex situ electron microscopy. Stable cyclic performance at the level of ∼700 and ∼350–400 mA h g⁻¹ can be achieved if the potential windows are restricted to 2.0–0.67 V vs. Li/Li⁺ for lithium and 2–0.33 vs. Na/Na⁺ for sodium half-cells. The results are critically discussed in light of existing literature reports.

Potassium electrochemistry of a battery anode based on black phosphorus is reported. The phosphorus component operates via electrochemical alloying with potassium and has a theoretical capacity of 843 mA h g⁻¹.