Capillary Encapsulation of Metallic Potassium in Aligned Carbon Nanotubes for Use as Stable Potassium Metal Anodes

Abstract

Metallic potassium (K) is a desirable anode for potassium secondary batteries due to its low electrode potential in nonaqueous electrolytes and high theoretical capacity. Nevertheless, instability caused by dendritic growth, large volume changes, and parasitic side reactions hamper its practical application. Here, an anode containing metallic K is fabricated by infiltrating an aligned carbon nanotube membrane (ACM) with molten K because of its good wettability to molten K due to the strong capillary forces. The K metal is spatially distributed on the 3D ACM framework, which offers sufficient electrode/electrolyte contact for charge transfer. The robust ACM host provides a large number of K nucleation sites and physically confines the K deposited there, thus mitigating dimensional changes during cycling. The pathways for electrons and ions in the anode are associated to form a mixed conducting network, which is beneficial for the electrochemical redox. Consequently, the anode shows stable plating/stripping profiles with low polarization in symmetric cells using conventional carbonate‐based electrolytes. In addition, dendrite growth is suppressed, and the anode demonstrates excellent suitability when paired with a Prussian blue cathode in a full cell. This design strategy is expected to provide a way to address the problems with using metallic K anodes.

Dendrite‐Free Potassium Metal Anodes in a Carbonate Electrolyte

“…In another study, the authors applied an electrochemical polishing method to create ultrasmooth ultrathin solid‐electrolyte interphase layers resulting in stable Li, Na, K anodes in FSI‐DME electrolytes . Researchers cleverly employed a puffed millet/NiO slurry or K melt‐infiltrated carbon nanotube membranes to stabilize the metal front. Goodenough and coworkers employed a deep eutectic Na–K alloy to promote self‐healing through the formation of a liquid phase .…”

A Site‐Selective Doping Strategy of Carbon Anodes with Remarkable K‐Ion Storage Capacity

“…One of the main reasons for this reality is the lack of suitable high‐performance PIB anode . Despite the success achieved in potassium metal anode, the long‐term cycling of potassium metal anode is still a challenge. On the other hand, various alloying and intercalating anodes have attracted widespread attention .…”

A Site‐Selective Doping Strategy of Carbon Anodes with Remarkable K‐Ion Storage Capacity

“…[11] One of the main reasons for this reality is the lack of suitable high-performance PIB anode. [12] Despite the success achieved in potassium metal anode, [13][14][15] the longterm cycling of potassium metal anode is still a challenge. On the other hand, various alloying and intercalating anodes have attracted widespread attention.…”