Chemical Prepotassiation Realizes Scalable KC₈Foil Anodes for Potassium‐Ion Pouch Cells

Abstract

potassium (K) metal are two typical anodes for PIBs. [4][5][6][7] Nevertheless, the former is facing the challenge of low initial coulombic efficiency (ICE, typically < 80%) and poor cycling stability in conventional electrolytes. [8][9][10][11][12][13][14] In order to compensate the consumption of active K + ions, the electrochemical prepotassiation of Gr anode is generally carried out to improve the overall performance of potassium-ion full cells. [15] This method seems to be effective, while the lack of standardized prepotassium potential of Gr can mislead the assessment of full battery performance. [16] Although K metal anodes have attracted great attention for realizing high energy density of half-cell PIBs in recent years, [17][18][19][20][21][22] the low metallic bonding energy makes it unavailable to be directly processed into rollable and foldable foils as commercial Li metal foils with thickness of micrometer scales (Figure S1, Supporting Information). [23][24][25][26] Particularly, K metal suffers from notorious dendrite growth and inevitable parasitic reactions with electrolytes which usually lead to safety issues and rapid degradation. [27] What is worse, the real electrochemical behavior of electrodes is concealed although infinite K + ions can be provided by K metal. It is obvious that the use of Gr and K metal as anodes for potassium-ion coin cells is still inadequate, not to mention the research for potassium-ion pouch cells. KC 8 , a Gr intercalation compound, is thermodynamically stable, and exhibits similar electrochemical properties as K metal anodes such as the low redox potential (−2.7 vs −2.93 V) and high specific volume capacity (544 vs 609 mAh cm −3 ). [28][29][30] More interestingly, KC 8 seems to be compatible with both ether and ester-based solvents, suggesting it is a highly promising alternative to K metal anode for PIBs. [27,30] Recently, smart strategies have been proposed to prepare KC 8 , including electrochemical prepotassiation, [15,16] high-temperature mixing of Gr and metallic K, [30] and compressing K metal directly on the surface of Gr moistened with electrolytes. [27] Nevertheless, these methods face the challenges of troublesome disassembly/reassembly processes of K||Gr half cells or impure-phase KC 8 products, which impedes the practical applications of KC 8 . Therefore, the scalable production of pure-phase KC 8 is urgently needed to facilitate the fundamental research of PIBs and the advancement of pouch cells.Here, through adopting a chemical prepotassiation strategy of Gr anodes, a large-area KC 8 foil was successfully fabricated Currently, graphite (Gr) and potassium metal are two typical and widely used anodes for potassium-ion batteries (PIBs). Unfortunately, the inevitable electrochemical prepotassiation of Gr anode and the unprocessable nature of K metal hinder the advancement of potassium-ion pouch cells. There is an urgent need to develop alternative anodes for promoting the practical applications of PIBs. Herein, KC 8 is proposed as a specialized anode for t...

Reticular Elastic Solid Electrolyte Interface Enabled by an Industrial Dye for Ultrastable Potassium‐Ion Batteries

“…Figure 2f shows that the capacity retention is still over 82.2% after K|| PTCDI cell cycles more than 1200 cycles. The cell's initial Coulombic efficiency (ICE) [ 50 ] increased from 78.1% to 89.1%, indicating that the addition of PG‐7 improved the compatibility of the electrolyte with the PTCDI electrode. Moreover, the rate performance of the cell also improved.…”

Rechargeable Potassium‐Ion Full Cells Operating at −40 °C

“…However, current researches on low‐temperature PIBs mainly focus on half cells with K metal as the reference electrode, while the research on cryogenic full cells is still blank [12,17] . Particularly, the utilization of K metal presents enormous safety hazards due to its propensity for dendrite growth and the occurrence of parasitic reactions, rendering it unsuitable for practical applications [18–20] . Hence, it is urgent to develop commercially available and universal anode materials for low‐temperature K‐ion full cells.…”

Conductive Polymer-Based Interlayers in Restraining the Polysulfide Shuttle of Lithium–Sulfur Batteries

“…Lithium–sulfur batteries (LSBs) are considered one of the most promising energy storage devices due to the advantages of high theoretical specific capacity, resource abundance and low toxicity. However, the severe diffusion of polysulfides during repeated charging/discharging leads to the low utilization of active materials, corrosion of lithium anode and large polarization of sulfur cathode, and seriously limits their practical application [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. In this regard, plenty of work has been carried out to suppress the diffusion of polysulfides in LSBs [ 9 , 10 , 11 , 12 , 13 , 14 ], such as the design of host materials [ 4 ], the introduction of interlayers between cathodes and separators [ 15 , 16 , 17 , 18 , 19 ] and the optimization of electrolytes [ 20 , 21 ].…”