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As post‐lithium ion batteries, both sodium‐ion batteries (SIBs) and potassium ion batteries (PIBs) possess great potential for large scale energy storage. However, the application of both SIBs and PIBs are hindered by the lack of suitable electrode materials. Here, we synthesized the sulfur decorated Ti3C2Tx (S−T3C2Tx) MXene as electrode material for SIBs and PIBs. Thanks to the sulfur functional group and the formation of Ti−S bond, which facilitates the sodium in‐/desertion and strengthens the potassium ion adsorption ability, as well as enhances ion reaction kinetics and improved structure stability, the S−T3C2Tx exhibit excellent sodium/potassium storage performance, high reversible capacities of 151 and 101 mAh g−1 at 0.1 mA g−1 were achieved for SIBs and PIBs, respectively. Moreover, the S−T3C2Tx exhibits remarkable long‐term capacity stability at a high density of 500 mA g−1, providing an impressive storage of 88 mAh g−1 for SIBs and 41 mAh g−1 for PIBs even after 2000 cycles. This work could give a deep comprehension of the heteroatom modification influence on the MXene‐based framework and promote the application of MXene electrodes. [ABSTRACT FROM AUTHOR]

To relieve the overwhelming pressure on fossil energy, aqueous magnesium ion batteries attracted tremendous attention owing to their low cost and high safety. However, the cathode materials are apt to occur lattice distortion because of the electrostatic interaction between magnesium ions and crystal. The 2×2 manganese octahedral molecular sieve with potassium ions and water located in the tunnels (K‐OMS‐2), utilized as a cathode material for chargeable magnesium ions batteries, is exposed to irreversible Mg2+ intercalation/deintercalation due to lattice distortion, which heavily damages the electrochemical properties and declines the capacity. Herein, we carry out an ion doping strategy to overcome the above issues, leading to an enhanced Mg Mg2+ storage behavior. The Nb or V cation is successfully doped into K‐OMS‐2 by a facile reflux method under room temperature. The specific surface area is enlarged by the addition of cations, which promise a large electrode‐electrolyte contact area. The Nb and V doped K‐OMS‐2 present a capacity of 252.6 and 265.9 mAh/g at 20 mA/g, respectively. This work demonstrates an ion doping approach toward exploiting the stable and high‐capacity Mg‐ion battery cathode and provides potential cathode materials for a large‐scale aqueous Mg‐ion‐based energy storage system. [ABSTRACT FROM AUTHOR]

Potassium‐ion hybrid capacitors have attracted increasing attention due to good energy density, high power density, and low cost. Ti3C2Tx‐MXene is considered as a promising anode material for K ion storage. However, undesirable stacking issues decrease its exposed area and breeds sluggish K ion transport. Herein, a facile spray‐lyophilization strategy is proposed to construct stacking‐resistant Ti3C2Tx with 3D structures. As‐prepared Ti3C2Tx hollow spheres/tubes present stack resistance, a large specific surface area, and a short ion diffusion pathway. When serving as an anode material, it shows enhanced capacity and thickness‐independent rate performance compared to 2D Ti3C2Tx. After 10 000 cycles, a specific capacity of 122 mAh g−1 is obtained at 1 A g−1. Systematic kinetics analyses demonstrate the significance of concentration polarization on the electrode's rate ability. Furthermore, a 3D Ti3C2Tx‖hierarchical porous activated carbon (HPAC) K‐ion hybrid capacitor is assembled and displays remarkable energy and power densities with energy retention of 100% after 10 000 cycles at 1 A g−1. Following this strategy, other 3D structures from nanosheets can also be obtained, such as 3D Ti3C2Tx microtubes and graphene oxide nanoscrolls. This study provides a viable approach to solve the stacking issues of 2D nanosheets to promote the application of 2D materials. [ABSTRACT FROM AUTHOR]

MoSSe nanosheets anchored carbon tubes (CTs) were prepared with facile hydrothermal method and further selenized carbonization treatment. The hollow tubular carbon skeletons with abundant functional groups can regulate the uniform growth of MoS 2 clusters. In the subsequent step, the selenation treatment can extend the interlayer spacing of MoS 2 and form chemical bond (Mo N C) between the interface of MoSSe and CTs, which can effectively facilitate the transport of electron/ions. As the electrode materials for both SIBs and KIBs, the MoSSe@CTs presented a high and efficient Na+/K+ ions storage capability and good cycling stability. [Display omitted] • The tubular carbon skeletons expose abundant active sites for MoS 2 nanosheets growth. • The selenization treatment can expand the interlayer spacing of MoS 2 nanosheets. • The unique structure can improve rate capability and cycling stability of batteries. The structural stability and reaction kinetics of anodes are essential factors for high-performance battery systems. Herein, the molybdenum sulfide selenide (MoSSe) nanosheets anchored on carbon tubes (MoSSe@CTs) are synthesized by a facile hydrothermal method combining with further selenization/calcination treatment. The unique tubular carbon skeletons expose abundant active sites for the well-dispersed growth of MoS 2 ultrathin nanosheets on both sides of the tubular carbon skeleton. In addition, the further selenization treatment can expand the interlayer spacing of molybdenum sulfide (MoS 2) nanosheets and facilitate the fast sodium/potassium-ion transition and storage. When used in sodium-ion batteries (SIBs), MoSSe@CTs electrode delivers a specific capacity of 486 mAh g−1 at 1 A g−1 and retains a stable reversible capacity of 465 mAh g−1 after 1000 cycles, indicating its good cycling stability. For potassium-ion batteries (KIBs), the MoSSe@CTs composite shows a capacity of 352 mA hg−1 at 1 A g−1 and a good cycling stability (maintains at 272 mA hg−1 after 1000 cycles). This work shows informative guiding significance for exploring advanced electrode materials of sodium/potassium-ion batteries. [ABSTRACT FROM AUTHOR]

Potassium ion batteries or capacitors are a promising technology for large-scale energy storage due to the abundant resource and low cost of potassium. However, the development of stable electrode materials with high capacity, capable rate ability, and excellent cycling stability remains a challenge. Herein, carbon dots modified reduced graphene oxides (LAP-rGO-CDs) are designed and synthesized via a rapid and green microwave-assisted method with l -Ascorbic acid 6-palmitate (LAP) as the reducing agent. LAP-rGO-CDs present enlarged interlayer spacing and faster ion transfer rate owing to the introducing of carbon dots. Serving as a potassium ion battery electrode, LAP-rGO-CDs showed a high specific capacity of 299 mAh g−1 at 1 A g−1 and excellent cycling stability. Moreover, a LAP-rGO-CDs//AC full carbon-based potassium ion capacitor is assembled and displays a maximum energy density of 119 Wh kg−1 and a power density of 5352 W kg−1. This work demonstrates the potential application of LAP-rGO-CDs for high-performance potassium ion storage. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbon coated MoS 2 hierarchical microspheres are synthesized with PVP assistance. • MoS 2 @C display the capacity of 124 mAh/g over 700 cycles at 1000 mA g−1 for K ion batteries. • The capacitive contribution promises the rate ability and cycling performance of MoS 2 @C. • The K ions storage mechanism in MoS 2 @C is investigated via ex-situ XRD and TEM. Potassium ion batteries (PIBs) is becoming a capable battery technology that can be used for coming generation low-cost energy storage. Although conversion-type transition metal dichalcogenides have shown major application prospects as high-capacity anode in PIBs, the dramatic structural degradation of materials during the potassium ions (de)intercalation process leads to unsatisfied cycling performance and poor rate ability. Herein, we carry out an interfacial engineering strategy to design and synthesize carbon-coated MoS 2 hierarchical microspheres (MoS 2 @C) for PIBs. The uniform carbon coating layer maintains the structural integrity and the heterointerfaces in MoS 2 @C provide an electron transport highway. As a consequence, at 100 mA g-1, for the MoS 2 @C hierarchical microspheres, a remarkable capacity of 332 mAh g-1 can be obtained, with a remarkable cycling ability. Moreover, at 1000 mA g-1, MoS 2 @C can still provide the capacity of 124 mAh g-1 over 700 cycles. The kinetics analysis and ex-situ characterization demonstrated the fast and reversible K ions storage behavior of MoS 2 @C. This work is helpful to design other conversion-type electrode materials for metal ion storage systems. [ABSTRACT FROM AUTHOR]

• Three F-doped biomass carbon were prepared by combining PTFE, DAST, HF and hemp. • The fluorinated products showed unexpected morphology and structure. • Products (by PTFE) exhibit the best capacity, rate capability, and lifetime in PIBs. • A lot of defects and high heteroatom content are key merits. Heteroatom doping can effectively improve the electrochemical activity of carbon materials. In this paper, three kinds of fluorine-doped biomass carbon are synthesized using industrial hemp core as the precursor and Poly tetra fluoroethylene (PTFE), Diethylaminosulphur trifluoride (DAST) and Hydrofluoric acid (HF) as fluorinating agents, respectively. Among them, the PTFE-treated biomass carbon (PTFE-CHEMP) is wrapped by fluorine-containing nanotubes, which has the most defects, the most F doping amount and the optimum pore size, and is beneficial to the adsorption of K +. When used as the anode of potassium ion batteries (PIBs), the PTFE-CHEMP electrode can provide an average reversible capacity of 369.6 mAh g−1 (200 mA g−1) in 500 cycles. Even at a high current of 2000 mA g−1, it can still provide an excellent rate capability of 229.3 mAh g−1. Kinetic analysis verify that its excellent rate performance comes from the K + storage mechanism dominated by surface-driven behavior. In addition, the constant current intermittent titration technique (GITT) shows that it still has the storage capacity for K + at high potentials. This work not only provides a reference for subsequent research on fluorine-doped biomass carbon, but also provides a potential solution for the production of low-cost, high-capacity PIBs anodes. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Nitrogen-rich biomass carbon (N-CHC) was prepared by urea etching method. • N-CHC exhibits excellent capacity and rate performance as a K+ half-cell anode. • Large specific surface area, lots of defects and heteroatoms are key advantages. • The hybrid capacitor composed of N-CHC and AC exhibits high energy and power density. Potassium ion hybrid capacitors have the advantages of high energy density, high power density, and low cost, and are expected to replace expensive lithium ion storage devices in large-scale applications. Here, an innovative nitrogen-rich biomass carbon (N-CHC) is prepared using urea as the etchant and hemp core as the raw material, which has a high specific surface area of 1185.3 m2 g−1 and nitrogen content of 8.56%. In addition, it shows a capacity of 442.4 mAh g−1 as a potassium ion half-cell anode at 30 mA g−1. Even under the high current test of 2000 mA g−1, N-CHC also shows excellent performance (175.0 mAh g−1). Further, the good rate performance is attributed to the large-scale capacitance control by analyzing reaction process kinetics. And the constant current intermittent titration technique (GITT) results show that N-CHC has a larger K+ diffusion coefficient than unetched biomass carbon. The maximum energy density of the full carbon-based hybrid capacitor composed of N-CHC anode and activated carbon cathode is 127.36 Wh kg−1, and the maximum power density is 2371 W kg−1. [ABSTRACT FROM AUTHOR]

• Sulfur-doped hemp-derived carbon is used in PIBs high-performance anodes. • It exhibits a higher capacity and better rate capability at 60 °C than at 25 °C. • Bonded sulfur is awakened at high temperature to enhance the adsorption of K +. • High temp promotes the decomposition of electrolyte is the main cause of danger. • The full cell composed of PTCDA exhibits excellent capacity at 60 °C. Potassium-ion batteries (PIBs) have huge advantages in terms of price and resource abundance, and are ideal substitutes for lithium-ion batteries (LIBs), but there is currently little research on their high-temperature fields. In this work, the sulfur-doped biomass carbon (CHP/S) is synthesized from biomass hemp stalks as the carbon source and sulfur powder as the sulfur source, with a high sulfur content of 18.6%. Sulfur mainly exist in the form of bonded sulfur (S-C, S-O) and have quite favorable stability. As a PIBs anode, it exhibits a specific capacity of 589 mAh g−1 (30 mA g−1) at 60 °C, which is 1.5 times the capacity at 25 °C. Electrochemical analysis and kinetic analysis indicate that the increased capacity mainly comes from the "arousal effect" of sulfur under high temperature conditions, and an increased temperature has a positive effect on the absorption and desorption performance of the material. In addition, the full cell assembled with Perylene-3, 4, 9, 10-tetracarboxylic dianhydride (PTCDA) cathode shows greater capacity (~80 mAh g−1) at 60 °C than at 25 °C. Unfortunately, the electrolyte decomposition problem caused by high temperature is easily dangerous. The result is of great significance to the research of high-temperature PIBs. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Carbon-coated SnS nanosheets and reduced graphene oxide composites are designed and synthesized. • Dual-carbon modification enhances the rate performance of SnS. • Potassiation stage adjustment results in stable cycling performance. Potassium ion batteries (PIBs) have attracted lots of attention due to its abundant resources. Exploring capable anode materials becomes one of the critical issues to achieve high-performance PIBs. Herein, carbon-coated SnS nanosheets and reduced graphene oxide (SnS@C/rGO) composite are designed and synthesized by a solvothermal reaction and heat treatment. The strategy of double carbon modification enhances the rate performance of SnS. Meanwhile, the cycling stability of SnS@C/rGO can be further improved by optimizing the voltage window, which can achieve the potassiation stage adjustment. K ions storage mechanism of SnS@C/rGO is investigated under different voltage windows. The deep alloying reaction occurs under low potential and is harmful to cycling performance. Moreover, the electrochemical kinetics of K ions storage is investigated by quantitative kinetics analysis. This work highlights the important effect of dual-carbon modification and adjusting the potassiation stage on the K ion storage. [ABSTRACT FROM AUTHOR]

This work presents a novel method for loading phosphorus nanoparticles by gas deposition. A large amount of nano phosphorus is loaded on the carbon matrix by the reaction of phosphine gas heating. The carbon is obtained by carbonization of hemp and has a natural porous structure. The combination of phosphorus and carbon in the form of C–O–P has better stability. The product obtained a stable capacity of 463 mAh/g at 0.04 A/g. There was still a reversible capacity of 270 mAh/g after continuous operation for 6 months at a high current density of 1 A/g, and the capacity retention rate was 96.7%. The excellent cyclic stability is due to new methods of phosphorus deposition. It can reach 10 times the running time of the same type of battery, which provides a new idea for preparing phosphor-doped electrode materials. Assembled into a potassium ion capacitor, an energy density of 294.2 Wh/kg can be obtained. [ABSTRACT FROM AUTHOR]