Dendrite-Free Potassium–Oxygen Battery Based on a Liquid Alloy Anode

Abstract

The safety issue caused by the dendrite growth is not only a key research problem in lithium-ion batteries but also a critical concern in alkali metal (i.e., Li, Na, and K)-oxygen batteries where a solid metal is usually used as the anode. Herein, we demonstrate the first dendrite-free K-O battery at ambient temperature based on a liquid Na-K alloy anode. The unique liquid-liquid connection between the liquid alloy and the electrolyte in our alloy anode-based battery provides a homogeneous and robust anode-electrolyte interface. Meanwhile, we manage to show that the Na-K alloy is only compatible in K-O batteries but not in Na-O batteries, which is mainly attributed to the stronger reducibility of potassium and relatively more favorable thermodynamic formation of KO over NaO during the discharge process. It is observed that our K-O battery based on a liquid alloy anode shows a long cycle life (over 620 h) and a low discharge-charge overpotential (about 0.05 V at initial cycles). Moreover, the mechanism investigation into the K-O cell degradation shows that the O crossover effect and the ether-electrolyte instability are the critical problems for K-O batteries. In a word, this study provides a new route to solve the problems caused by the dendrite growth in alkali metal-oxygen batteries.

Strategies Toward Stable Nonaqueous Alkali Metal–O2 Batteries

“…In addition to Si anode, other anode materials widely studied in alkali-ion batteries are available in AMOBs. [77] A stable and long cycle life over 70 cycles was achieved with a low discharge/ charge overpotential less than 200 mV in the KPF 6 /DEGDME electrolyte. [72] A sodiated carbon, which is widely studied as anode material for Na-and K-ion batteries with high capacity, [73] showed high stability without dendrite formation in a Na-O 2 cell (Figure 8c,d).…”

Room‐Temperature Liquid Na–K Anode Membranes

“…Initially we used ac arbon paper that soaked up the Na-K liquid only at aw etting temperature of 420 8 8C. [9] Therefore, we report here that the liquid Na-K alloy can be vacuum infiltrated into many metal foams or carbon paper at 25 8 8C. [9] Therefore, we report here that the liquid Na-K alloy can be vacuum infiltrated into many metal foams or carbon paper at 25 8 8C.…”

“…[3,5] Other cells with molten liquid-metal electrodes suffer from similar problems. [7][8][9] However,a tr oom temperature,t he liquid Na-K alloy has av ery high surface tension, which prevents it from spreading out over the liquid electrolyte surface.Inorder to wet each other,the liquid Na-K alloy has to be immobilized into ap orous matrix membrane. [7][8][9] However,a tr oom temperature,t he liquid Na-K alloy has av ery high surface tension, which prevents it from spreading out over the liquid electrolyte surface.Inorder to wet each other,the liquid Na-K alloy has to be immobilized into ap orous matrix membrane.…”

“…[7][8][9] However,a tr oom temperature,t he liquid Na-K alloy has av ery high surface tension, which prevents it from spreading out over the liquid electrolyte surface.Inorder to wet each other,the liquid Na-K alloy has to be immobilized into ap orous matrix membrane. [9] Therefore, we report here that the liquid Na-K alloy can be vacuum infiltrated into many metal foams or carbon paper at 25 8 8C.We also show that the resulting electrode membranes are stable on contact with the organic liquid carbonate electrolytes,but not with the organic ether electrolytes.TheNa-K alloy is liquid at 25 8 8Cfrom 9.2 to 58.2 wt %of sodium; [10] within this range,o nce fresh sodium metal meets potassium metal, al iquid forms spontaneously at ambient temperature.F igure 1a illustrates this process;s upplemen- Figure 1. [7,8] Although the liquid Na-K alloy remained immobilized in the carbon paper at ambient temperature,w hich allowed its use with al iquid electrolyte and an insertion-compound cathode,t he high temperature infiltration of the highly reactive alkalialloy into the carbon paper is neither economical nor convenient for research and commercialization.…”

New Insights into the Electrochemistry Superiority of Liquid Na–K Alloy in Metal Batteries

“…Recently, Goodenough and co‐workers have in succession reported liquid Na‐K alloy anode enables dendrite‐free potassium batteries . Yu et al employed the Na‐K alloy as the anode for K−O 2 batteries to address the issues from the dendrite growth, but they could not improve ICE . Despite the preliminary exploration made, very minute is known about the difference in the electrochemical behaviors of the cathode material with the liquid Na‐K alloy from the solid Na and solid K. What's more, by comparison with the extensive research of the traditional metal ion or metal‐sulfur batteries, the exploration of alkali metal batteries requires more endeavors and efforts in terms of reaction kinetics and intercalation/extraction behaviors.…”