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.

ARTICLE This journal isWith the expected theoretical capacity of 2,596 mAh 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 phosphoruscarbon nanocomposite anodes for both lithium-ion and sodium-ion batteries. The composite electrodes are able to display high initial capacities of approximately 1,700 and 1,300 mAh 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 Li 3 P phase for lithium cells and an incomplete transformation to Na 3 P 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 mAh 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. Figure 4. TEM analysis of phosphorus and phosphorus-carbon samples . (a, b) Selected area electron diffraction patterns of the red and black phases of phosphorus (bright-field images are shown as insets); (c, d, e) an elastic image, carbon and phosphorus energy-filtered elemental maps of the composite C-1; (f, g, h) an elastic image, carbon and phosphorus energy-filtered elemental maps of the composite C-2 (colour scheme: green -carbon, red -phosporus).Phosphorus -carbon nanocomposites were systematically evaluated as high capacity anodes for both lithium-ion and sodium-ion batteries. The composites are able to provide attractive capacities based on alloying-dealloying operating mechanism but their cyclic performance depends significantly on the operating potential window; the capacity declines monotonously within the window of 2 -0.01 V vs Li/Li + or Na/Na + and is very stable in a narrower potential window.

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.

The electrochemical behaviour of Co3O4 with sodium is reported here. Upon cycling in the voltage window of 0.01-3.0 V, Co3O4 undergoes a conversion reaction and exhibits a reversible capacity of 447 mA h g(-1) after 50 cycles. Therefore, nanostructured Co3O4 presents feasible electrochemical sodium storage, offering possibilities to develop new anode materials for sodium-ion batteries.