Structural engineering of SnS quantum dots embedded in N, S Co-Doped carbon fiber network for ultrafast and ultrastable sodium/potassium-ion storage

Tunable Interfacial Electric Field-Mediated Cobalt-Doped FeSe/Fe3Se4 Heterostructure for High-Efficiency Potassium Storage

The interfacial electric field (IEF) in the heterostructure can accelerate electron transport and ion migration, thereby enhancing the electrochemical performance of potassium-ion batteries (PIBs). Nevertheless, the quantification and modulation of the IEF for high-efficiency PIB anodes currently remains a blank slate. Herein, we achieve for the first time the quantification and tuning of IEF via amorphous carbon-coated undifferentiated cobalt-doped FeSe/Fe3Se4 heterostructure (denoted UN-CoFe4Se5/C) for efficient potassium storage. Co doping can increase the IEF in FeSe/Fe3Se4, thereby improving the electron transport, promoting the potassium adsorption capacity, and lowering the diffusion barrier. As expected, the IEF magnitude in UN-CoFe4Se5/C is experimentally quantified as 62.84 mV, which is 3.65 times larger than that of amorphous carbon-coated FeSe/Fe3Se4 heterostructure (Fe4Se5/C). Benefiting from the strong IEF, UN-CoFe4Se5/C as a PIB anode exhibits superior rate capability (145.8 mAh g-1 at 10.0 A g-1) and long cycle lifespan (capacity retention of 95.1 % over 3000 cycles at 1.0 A g-1). Furthermore, this undifferentiated doping strategy can universally regulate the IEF magnitude in CoSe2/Co9Se8 and FeS2/Fe7S8 heterostructures. This work can provide fundamental insights into the design of advanced PIB electrodes.

Recent advances in rational design for high-performance potassium-ion batteries

The growing global energy demand necessitates the development of renewable energy solutions to mitigate greenhouse gas emissions and air pollution. To efficiently utilize renewable yet intermittent energy sources such as solar and wind power, there is a critical need for large-scale energy storage systems (EES) with high electrochemical performance. While lithium-ion batteries (LIBs) have been successfully used for EES, the surging demand and price, coupled with limited supply of crucial metals like lithium and cobalt, raised concerns about future sustainability. In this context, potassium-ion batteries (PIBs) have emerged as promising alternatives to commercial LIBs. Leveraging the low cost of potassium resources, abundant natural reserves, and the similar chemical properties of lithium and potassium, PIBs exhibit excellent potassium ion transport kinetics in electrolytes. This review starts from the fundamental principles and structural regulation of PIBs, offering a comprehensive overview of their current research status. It covers cathode materials, anode materials, electrolytes, binders, and separators, combining insights from full battery performance, degradation mechanisms, in situ/ex situ characterization, and theoretical calculations. We anticipate that this review will inspire greater interest in the development of high-efficiency PIBs and pave the way for their future commercial applications.

Interface engineering of metal sulfides-based composites enables high-performance anode materials for sodium-ion batteries

Metal sulfides (MSs) have attracted much attention as anode materials for sodium-ion batteries (SIBs) due to their high sodium storage capacity. However, the unsatisfactory electrochemical performance induced by the huge volume change and sluggish kinetics hampered the practical application of SIBs. Herein, guided by the heterostructure interface engineering, novel multicomponent metal sulfide-based anodes, including SnS, FeS, and Fe3N embedded in N-doped carbon nanosheets (SnS/FeS/Fe3N/NC NSs), have been synthesized for high-performance SIBs. The as-prepared SnS/FeS/Fe3N/NC NSs with abundant heterointerfaces and high conductivity of N-doped carbon nanosheet matrix can shorten the Na+ diffusion path and promote reaction kinetics during the sodiation/desodiation process. Moreover, the presence of Fe3N can promote the reversible conversion of SnS and FeS during the cycling process. As a consequence, when evaluated as anode materials for SIBs, the SnS/FeS/Fe3N/NC NSs can maintain a high sodium storage capacity of 473.6 mAh g-1 after 600 cycles at 2.0 A g-1 and can still provide a high reversible capacity of 537.4 mAh g-1 even at 5.0 A g-1 This discovery offers a novel strategy for constructing metal sulfide-based anode materials for high-performance SIBs.

Biomass-derived carbon-sulfur hybrids boosting electrochemical kinetics to achieve high potassium storage performance

Potassium-ion batteries (PIBs) as an emerging battery technology have garnered significant research interest. However, the development of high-performance PIBs critically hinges on reliable anode materials with comprehensive electrochemical performance and low cost. Herein, low-cost N-doped biomass-derived carbon-sulfur hybrids (NBCSHs) were prepared through a simple co-carbonization of the mixture of a biomass precursor (coffee grounds) and sulfur powder. The sulfur in NBCSHs predominantly exists in the form of single-atomic sulfur bonded with carbon atoms (CSC), functioning as main active redox sites to achieve high reversible capacity. Electrochemical evaluations reveal that the NBCSH 1-3 with moderate sulfur content shows significantly improved potassium storage performance, such as a high reversible capacity of 484.7 mAh g-1 and rate performance of 119.4 mAh g-1 at 5 A g-1, 4.5 and 14.7 times higher than that of S-free biomass-derived carbon, respectively. Furthermore, NBCSH 1-3 exhibits stable cyclability (no obvious capacity fading even after 1000 cycles at 0.5 A g-1) and excellent electrochemical kinetics (low overpotentials and apparent diffusion coefficients). The improved performance of NBCSHs is primarily attributed to pseudocapacitance-dominated behavior with fast charge transfer capability. Density functional theory calculations also reveal that co-doping with S, N favors for achieving a stronger potassium adsorbing capability. Assemble K-ion capacitors with NBCS 1-3 as anodes demonstrate stable cyclability and commendable rate performance. Our research envisions the potential of NBCSHs as efficient and sustainable materials for advanced potassium-ion energy storage systems.

Heterostructured CoS2/SnS2 encapsulated in sulfur-doped carbon exhibiting high potassium ion storage capacity

Metallic sulfides are currently considered as ideal anode materials for potassium-ion batteries by virtue of their high specific capacities. However, their low intrinsic electronic conductivity, large volume variation and dissolution of polysulfides in electrochemical reactions hinder their further development toward practical applications. Here, we propose an effective structural design strategy by encapsulating CoS2/SnS2 in sulfur-doped carbon layers, in which internal voids are created to relieve the strain in the CoS2/SnS2 core, while the sulfur-doped carbon layer serves to improve the electron transport and inhibit the dissolution of polysulfides. These features enable the as-designed anode to deliver a high specific capacity (520 mAh/g at 0.1 A/g), a high rate capability (185 mA h g-1 at 10 A/g) and lifespan (0.016 % capacity loss per cycle up to 1500 cycles). Our comprehensive electrochemical characterization reveals that the heterostructure of CoS2/SnS2 not only promotes charge transfer at its interfaces, but also enhances the rate of K+ diffusion. Additionally, potassium-ion capacitors based on this novel anode are able to attain an energy density up to 162 Wh kg-1 and ∼ 96 % capacity retention after 3000 cycles at 10 A/g.The demonstrated design rule combining morphological and structural engineering strategies sheds light on the development of advanced electrodes for high performance potassium-based energy storage devices.