Rechargeable K‐CO₂ Batteries with a KSn Anode and a Carboxyl‐Containing Carbon Nanotube Cathode Catalyst

Abstract

Metal K‐CO2 batteries suffer from large polarization and safety hazards, which mainly result from the difficult decomposition of K2CO3 and dendrite growth. Moreover, the battery redox mechanism remains not fully understood. Here we report K‐CO2 batteries with KSn alloy as the anode and carboxyl‐containing multi‐walled carbon nanotubes (MWCNTs‐COOH) as the cathode catalyst, proving the redox mechanism to be 4 KSn + 3 CO2 ⇄ 2 K2CO3 + C + 4 Sn. Compared with K metal, the less active and dendrite‐free KSn anode effectively enhances the safety and stability of CO2 batteries. More importantly, the strong electrostatic interaction between MWCNTs‐COOH and K2CO3 weakens the C=O bond in K2CO3 and thus facilitates K2CO3 decomposition. As a result, the K‐CO2 batteries show excellent cycling stability (an overpotential increase of 0.89 V after 400 cycles) and good rate performance (up to 2000 mA g−1). This work paves a way to develop highly stable and safe CO2‐based batteries.

Design Principles of Sodium/Potassium Protection Layer for High‐Power High‐Energy Sodium/Potassium‐Metal Batteries in Carbonate Electrolytes: a Case Study of Na2Te/K2Te

“…Note that, the bubbles on the surface of bare Na are much more than those of Na@Na 2 Te, indicating the Na 2 Te protection layer is able to reduce the side reactions between Na metal and electrolyte. [ 9,59 ] The morphology evaluations of bare Na and Na@Na 2 Te during the plating/stripping process are schematically illustrated in Figure S22 (Supporting Information). The Na + prefers to deposit on the bulge of Na metal, resulting in the dendrites grow continuously and SEI crack.…”

“…The peaks of C1s XPS spectrum with binding energy at 289.9, 286.2, and 285.1 eV correspond to carbonate, CO bond, and CC bond, respectively. [ 9 ] In terms of O 1s spectra, the binding energies of Na KLL, CO, and carbonate are located at 536.5, 532.4, and 531.4 eV, respectively. [ 30 ] As to F 1s spectra, two peaks located at 689.3 and 684.4 eV can be assigned to CF/TeF bond and NaF salt.…”

“…Compared to traditional anode materials, the sodium‐ and potassium‐metal anodes possess high theoretical specific capacity (1165 and 687 mAh g −1 for Na and K, respectively), low redox potential (−2.71 (Na) and −2.93 V (K) vs standard hydrogen electrode), and abundant resources (2.8 wt% (Na) and 1.5 wt% (K) in the Earth's crust). [ 1–6 ] Additionally, the sodium‐ and potassium‐metal anodes can pair with high capacity cathodes to achieve high energy and power density, including Na/K‐O 2 , [ 7,8 ] Na/K‐CO 2 , [ 9,10 ] Na/K‐S, [ 11–13 ] and Na/K‐organic batteries. [ 14 ] Therefore, the sodium‐metal batteries (SMBs) and potassium‐metal batteries (PMBs) have been considered as the most promising potential candidates for low‐cost and large‐scale energy storage systems.…”

Prospects of Electrode Materials and Electrolytes for Practical Potassium‐Based Batteries

“…The conversion materials, such as, chalcogen elements (O 2 , [36,38,[127][128][129][130][131] S, [41,42,[132][133][134][135][136][137] Se, [138][139][140][141][142][143] Te [144,145] ), CO 2 , [39,40] and I 2 , [146,147] usually possess a high theoretical capacity and operating voltage when used as a cathode for PIBs, leading to a high theoretical energy density. Also, the low-cost and potential economic advantages of conversion materials make them more attractive in large-scale EESs.…”

“…[32][33][34] In 2004, Ali Eftekhari [35] pioneered a potassium secondary battery by employing a Prussian blue-based cathode in the non-aqueous 1 m KBF 4 in EC: EMC electrolyte, which attracted much interest from the battery community. Subsequently, various potassium-based batteries/electrodes/electrolytes started booming, including the potassium-air (K-O 2 /K-CO 2 ) batteries, [36][37][38][39][40] potassium-sulfur (K-S)batteries, [41][42][43] potassium-based dual ion batteries (PDIBs), [44][45][46][47][48] and potassiumion capacitors (PICs) or battery-supercapacitor hybrid devices (BSHs). [49][50][51][52][53][54] To date, researchers have developed various kinds of anode and cathode materials for PIBs.…”