Conventional carbon anodes for potassium-ion batteries: Progress, challenges and prospects

Polydopamine (PDA) as an anode of potassium ion batteries (PIBs) has received a lot of attention due to its convenient preparation, environment friendliness, and low cost. However, due to the low conductivity of organic polydopamine, the active substance can easily dissolve in the cycle process, which leads to a low rate performance and short cycle life of PIBs. Here, dopamine was quantitatively polymerized onto the surface of a carbon-intertwined network of carbon nanotubes (CNTs). By means of density functional theory calculation and electrochemical measurement, the adsorption/desorption of potassium ions by oxygen-containing and nitro-containing functional groups in PDA and its promotion by CNTs are revealed. The π-π superposition effect between dopamine and CNTs effectively alleviates the dissolution of PDA during the cycle. A combination of PDA and CNTs could resolve low conductivity issues and provide excellent battery cycle performance. Results show that PDA@CNT-10 exhibits a high reversible capacity (223 mA h g-1, 200 cycles at 0.2 A g-1) and a long cycle life (151 mA h g-1, 3000 cycles at 1 A g-1). When first used as an organo-potassium hybrid capacitor assembled from the anode of the battery and activated carbon as the cathode, it can provide a high reversible capacity (76 mA h g-1, 2000 cycles at 2 A g-1), which promotes the potential application of PIBs in the future.

Graphite can be successfully used as an anode for potassium-ion batteries (PIBs), while its conversion to KC8 leads to huge volume expansion, destruction of solid electrolyte interphase (SEI), and thus poor cycling stability. Incorporating additives into electrolytes is an economical and effective way to construct robust SEI for high-performance PIBs. Herein, we developed a series of sulfur-containing additives for PIB graphite anodes, and the impacts of their molecular structure and contents on the SEI are also systematically investigated. Compared with butylene sulfites and 1,3-propane sultone, the 1,3,2-dioxathiolane 2,2-dioxide (DTD) additive endows the graphite electrode (GE) with a higher reversible capacity, and better cycling stability in both the dilute potassium bis(fluorosulfonyl)imide (KFSI)- and potassium hexafluorophosphate (KPF6)-based carbonate electrolyte, as a result of a thinner and sulfate-enriched SEI. Moreover, the addition of a trace amount (0.2 wt %) DTD to the electrolyte can effectively protect the GE running over 800 cycles at 1 C. Excessive additives in the electrolyte will induce continuous SEI growth and render a rapid capacity fading of the GE. This strategy using the electrolyte additive paves the way for the design of novel PIB electrolytes and thus provides a great opportunity for commercial PIBs.

Coupling graphene microribbons with carbon nanofibers: New carbon hybrids for high-performing lithium and potassium-ion batteries

Designing N-doped graphene/ReSe2/Ti3C2 MXene heterostructure frameworks as promising anodes for high-rate potassium-ion batteries

Flower-like graphitic carbon derived from biomass for anode of potassium ion battery

High entropy anodes in batteries: From fundamentals to applications

Studies have found that oxygen-rich-containing functional groups in carbon-based materials can be used as active sites for the storage performance of K+, but the basic storage mechanism is still unclear. Herein, we construct and optimize 3D honeycomb-like carbon grafted with plentiful COOH/C = O functional groups (OFGC) as anodes for potassium ion batteries. The OFGC electrode with steady structure and rich functional groups can effectively contribute to the capacity enhancement and the formation of stable solid electrolyte interphase (SEI) film, achieving a high reversible capacity of 230 mAh g−1 at 3000 mA g−1 after 10,000 cycles (almost no capacity decay) and an ultra-long cycle time over 18 months at 100 mA g−1. The study results revealed the reversible storage mechanism between K+ and COOH/C = O functional groups by forming C-O-K compounds. Meanwhile, the in situ electrochemical impedance spectroscopy proved the highly reversible and rapid de/intercalation kinetics of K+ in the OFGC electrode, and the growth process of SEI films. In particular, the full cells assembled by Prussian blue cathode exhibit a high energy density of 113 Wh kg−1 after 800 cycles (calculated by the total mass of anode and cathode), and get the light-emitting diodes lamp and ear thermometer running.

ZnS has acquired increasing attention for high-performance PIBs anode because of its remarkable theoretical capacity, and redox reversibility for conversion reaction. However, the larger volume variation and delayed reaction kinetics for the ZnS in the discharge/charge processes lead to pulverization and severe capacity degradation. Herein, the trumpet-like ZnS@C composite was synthesized by template method by using sodium citrate as carbon source followed by vulcanization process. As potassium ion batteries (PIB) anode, ZnS@C composite exhibits good rate performance and long life (stable reversible capacity of 107.8 mAh/g over 2000 charge-discharge cycles at 5 A/g and high reversible capacity of 310 mAh/g at 0.1 A/g). The outstanding electrochemical performance of the ZnS@C composite is ascribed to its unique structure, which can mitigate the volume expansion of ZnS in the charge discharge process, expand the contact area between the electrode and electrolyte, and improve the conductivity of electrode materials by the introduction of carbon layer. This method of synthesizing trumpet-like ZnS@C composite provides an important strategy for obtaining potassium ion batteries anode with long cycle.

Unraveling the advances of trace doping engineering for potassium ion battery anodes via tomography

Cobalt-catalyzed organic nano carbon source for hybrid hard carbon/graphite nanoribbon anode in high-potential potassium-ion batteries.

Large-scale low-cost synthesis methods for potassium ion battery (PIB) anodes with long cycle life and high capacity have remained challenging. Here, inspired by the structure of a biological cell, biomimetic carbon cells (BCCs) were synthesized and used as PIB anodes. The protruding carbon nanotubes across the BCC wall mimicked the ion-transporting channels present in the cell membrane, and enhanced the rate performance of PIBs. In addition, the robust carbon shell of the BCC could protect its overall structure, and the open space inside the BCC could accommodate the volume changes caused by K+ insertion, which greatly improved the stability of PIBs. For the first time, a stable solid electrolyte interphase layer is formed on the surface of amorphous carbon. Collectively, the unique structural characteristics of the BCCs resulted in PIBs that showed a high reversible capacity (302 mAh g−1 at 100 mA g−1 and 248 mAh g−1 at 500 mA g−1), excellent cycle stability (reversible capacity of 226 mAh g−1 after 2100 cycles and a continuous running time of more than 15 months at a current density of 100 mA g−1), and an excellent rate performance (160 mAh g−1 at 1 A g−1). This study represents a new strategy for boosting battery performance, and could pave the way for the next generation of battery-powered applications.

Unraveling the effect of salt chemistry on long-durability high-phosphorus-concentration anode for potassium ion batteries

Here, we demonstrate the production of 2D nanosheets of arsenic disulfide (As2S3) via liquid-phase exfoliation of the naturally occurring mineral, orpiment. The resultant nanosheets had mean lateral dimensions and thicknesses of 400 and 10 nm, and had structures indistinguishable from the bulk. The nanosheets were solution mixed with carbon nanotubes and cast into nanocomposite films for use as anodes in potassium-ion batteries. These anodes exhibited outstanding electrochemical performance, demonstrating an impressive discharge capacity of 619 mAh/g at a current density of 50 mA/g. Even after 1000 cycles at 500 mA/g, the anodes retained an impressive 94% of their capacity. Quantitative analysis of the rate performance yielded a capacity at a very low rate of 838 mAh/g, about two-thirds of the theoretical capacity of As2S3 (1305 mAh/g). However, this analysis also implied As2S3 to have a very small solid-state diffusion coefficient (∼10-17 m2/s), somewhat limiting its potential for high-rate applications.

Protein-derived 3D amorphous carbon with N, O doping as high rate and long lifespan anode for potassium ion batteries

Potassium-ion batteries (PIBs) are considered potential candidates for large-scale energy storage systems due to the abundant resources of potassium. Among various reported anode materials, bismuth anodes with the advantages of high theoretical specific capacity, low cost, and nontoxicity have attracted widespread attention. However, bismuth anodes experience significant volume changes during the charge/discharge process, leading to unsatisfactory cycling stability and rate performance. In this review, we focus on summarizing the research progress of bismuth anodes in PIBs. We discuss in detail the modification strategies for bismuth anodes in PIBs, including electrolyte optimization, morphology design, and hybridization with carbon materials. In addition, we attempt to propose possible future directions for the development of bismuth anodes in PIBs, aiming to expedite their practical application. It is believed that this review can assist researchers in more efficiently designing high-performance bismuth anode materials for PIBs.