Anode For Potassium-ion Batteries Research Articles

Modulating Co[sbnd]Co bonds average length in Co0.85Se1−xSx to enhance conversion reaction for potassium storage

While alloying transition metal chalcogenides (TMCs) with other chalcogen elements can effectively improve their conductivity and electrochemical properties, the optimal alloying content is still uncertain. In this study, we study the influence of dopant concentration on the chemical bonds in TMC and reveal the associated stepwise conversion reaction mechanism for potassium ion storage. According to density function theory calculations, appropriate S-doping in Co0.85Se (Co0.85Se1−xSx) can reduce the average length of CoCo bonds because of the electronegativity variation, which is thermodynamically favourable to the phase transition reactions. The optimal Se/S ratio (x = 0.12) for the conductivity has been obtained from experimental results. When assembled as an anode in potassium-ion batteries (PIBs), the sample with optimized Se/S ratio exhibits extraordinary electrochemical performance. The rate performance (229.2 mA h g−1 at 10 A g−1) is superior to the state-of-the-art results. When assembled with Prussian blue (PB) as a cathode, the pouch cell exhibits excellent performance, demonstrating its great potential for applications. Moreover, the stepwise K+ storage mechanism caused by the coexistence of S and Se is revealed by in-situ X-ray diffraction and ex-situ transmission electron microscopy techniques. Hence, this work not only provides an effective strategy to enhance the electrochemical performance of transition metal chalcogenides but also reveals the underlying mechanism for the construction of advanced electrode materials.

A universal method for N/B codoped carbon bubbles for enhanced potassium ion storage

Carbon materials are widely regarded as highly promising anode materials for potassium ion batteries due to their features of tunable structure, affordable price, excellent conductivity, and favorable chemical stability. However, due to the sluggish potassium storage kinetics and relatively severe volumetric effect brought about by the large radius of potassium ions, carbon materials often suffer from unsatisfactory reversible capacity and weak rate performance. In this work, we propose to prepare a distinctive dual-atom doped carbon bubble material by a simple self-templating method. This unique structural design results in a high specific surface area, large layer spacing, abundant pore structure and enriched active sites. Owing to these merits, the N, B-doped carbon exhibits a high reversible capacity (534.0 mA h g−1 at 0.1 A g−1 after 200 cycles), long-term cycling stability and excellent rate capacity when used as the anode for potassium-ion batteries. The results of electrochemical kinetic studies indicate that capacitance control effects play a dominant role in the total energy storage mechanism. Furthermore, this preparation method has good generalizability and is expected to have applications in other batteries, supercapacitors or catalysis.

Thermal Induced Conversion of CoFe Prussian Blue Analogs Nanocubes Wrapped by Doped Carbon Network Exhibiting Fast and Stable Potassium Ion Storage as Anode.

Prussian blue analogs (PBAs) show great promise as anode materials for potassium-ion batteries (PIBs) due to their high specific capacity. However, PBAs still suffer from the drawbacks of low electronic conductivity and poor structural stability, leading to inadequate rate and cyclic performance. To address these limitations, CoFe PBA nanocubes wrapped with N/S doped carbon network (CoFe PBA@NSC) as anode for PIBs is designed by using thermal-induced in situ conversion strategy. As expected, the structural advantages of nanosized PBA cubes, such as abundant interfaces and large surface area, enable the CoFe PBA@NSC electrode to demonstrate superior rate properties (557 and 131mAhg-1 at 0.05 and 10Ag-1) and low capacity degradation (0.093% per cycle over 1000 cycles at 0.5Ag-1). Furthermore, several ex situ characterizations revealed the K-ion storage mechanism. Fe+ and Co0 are generated during potassicization, followed by a completely reversible chemical state of iron while some cobalt monomers remained during depotassication. Additionally, the as-built potassium-ion hybrid capacitor based on CoFe PBA@NSC anode exhibits a high energy density of 118Whkg-1. This work presents an alternative but promising synthesis route for Prussian blue analogs, which is significant for the advancement of PIBs and other related energy storage devices.

Electrosprayed hierarchical mesoporous Mn0.5Ti2(PO4)3@C microspheres as promising High-Performance anode for Potassium-Ion batteries

NASICON-structured Ti-based polyanion compounds benefit from a stable structural framework, large ion channels, and fast ion mobility. However, the large radius of potassium and its poor electronic conductivity restrict its use in potassium-ion batteries. Herein, hierarchical mesoporous Mn0.5Ti2(PO4)3@C microspheres have been successfully synthesized using a simple electrospraying method. These microspheres consist of Mn0.5Ti2(PO4)3 nanoparticles evenly embedded in three-dimensional mesoporous carbon microspheres. The hierarchical mesoporous micro/nanostructure facilitates the rapid insertion and extraction of K+, while the three-dimensional carbon microspheres matrix enhances electrical conductivity and prevents active materials from collapsing during cycling. So the hierarchical mesoporous Mn0.5Ti2(PO4)3@C microspheres exhibit a high reversible discharge specific capacity (306 mA h g−1 at 20 mA g−1), a notable rate capability (123 mA h g−1 at 5000 mA g−1), and exceptional cycle performance (148 mA h g−1 at 500 mA g−1 after 1000 cycles). The results show that electrosprayed Mn0.5Ti2(PO4)3@C microspheres are a promising anode for PIBs.

Confining SnSe particles in nitrogen-doped carbon nanofibers: A free-standing, binder-free anode for potassium-ion batteries

SnSe alloy has garnered attention as a promising anode material for potassium-ion batteries due to its high theoretical capacity of 847 mAh g−1. However, its practical application is limited by significant volume change during cycling, which leads to rapid capacity degradation. To address this challenge, we’ve introduced an innovative method using electrospinning and subsequent heat treatment to produce SnSe particles confined within nitrogen-doped carbon nanofibers (SnSe@NCNF). This design not only mitigates the volume expansion of SnSe particles but also provides a continuous 1D conduction network. Notably, SnSe@NCNF functions as an anode material without necessitating polymer binders or current collectors. Our optimized SnSe@NCNF-2 anode has shown commendable electrochemical performance, retaining a discharge capacity of 154.61 mAh g−1 after 1000 cycles at a substantial specific current of 500 mA g−1.

Constructing Carbon Nanotube-Enhanced Ultra-Thin Organic Compounds with Multi-Redox Sites for "All-Temperature" Potassium-Ion Battery Anode and its Step-Wise K-Storage Mechanism.

Organic compounds are regarded as important candidates for potassium-ion batteries (KIBs) due to their light elements, controllable polymerization, and tunable functional groups. However, intrinsic drawbacks largely restrict their application, including possible solubility in electrolytes, poor conductivity, and low diffusion coefficients. To address these issues, an ultrathin layered pyrazine/carbonyl-rich material (CT) is synthesized via an acid-catalyzed solvothermal reaction and homogeneously grown on carbon nanotubes (CNTs), marked as CT@CNT. Such materials have shown good features of exposing functional groups to guest ions and good electron transport paths, exhibiting high reversible capacity and remarkable rate capability over a wide temperature range. Two typical electrolytes are compared, demonstrating that the electrolyte of LX-146 is more suitable to maximize the electrochemical performances of electrodes at different temperatures. A stepwise reaction mechanism of K-chelating with C═O and C═N functional groups is proposed, verified by in/ex situ spectroscopic techniques and theoretical calculations, illustrating that pyrazines and carbonyls play the main roles in reacting with K+ cations, and CNTs promote conductivity and restrain electrode dissolution. This study provides new insights to understand the K-storage behaviors of organic compounds and their "all-temperature" application.

Low‐Temperature Carbonized N/O/S‐Tri‐Doped Hard Carbon for Fast and Stable K‐Ions Storage

AbstractHard carbon stands out as one of the premier anodes for potassium‐ion batteries (PIBs), celebrated for its cost‐effectiveness, natural abundance, and high yield. Yet, its performance in PIBs remains subpar due to slow kinetics, a result of the large ionic radius of K‐ions. Herein, a unique lamellar N/O/S‐tri‐doped hard carbon (NOSHC) has been developed at an impressively low pyrolysis temperature of 500°C, showcasing a distinct “slope‐dominated” characteristic. NOSHC delivers superior rate performance with a dominant surface‐driven capacitive contribution (71.6% at a scan rate of 0.5 mV s−1), maintaining a robust reversible specific capacity of 125 mAh g−1 (half its peak) even at 5 A g−1. Its stability is equally commendable, as it sustains a substantial specific capacity of 265 mAh g−1 after 100 cycles at 0.1 A g−1 and retains 210 mAh g−1 post‐1000 cycles at 1 A g−1. Moreover, NOSHC undergoes continuous activation via potassiation/depotassiation during cycling. Rich heteroatom doping introduces a plethora of defects and vacancies, creating abundant active sites. The distinct lamellar structure, featuring minimal pores, optimizes K‐ions transport by shortening the diffusion length. This study unveils the potential of enhancing hard carbon anodes for PIBs by harnessing a low carbonization temperature approach.

Nano hollow carbon regulated by carbon dots as a high-performance anode for potassium and sodium ion battery

In this paper, carbon dots (CDs) derived from citrus peel were used as regulators to adjust the size of template SiO2 and further prepare hollow carbon spheres with different diameter. During the synthesis process of SiO2 templates, the abundant surface functional groups of CDs interact strongly with the functional groups (hydroxyl groups, etc.) possessed by silicic acid and TEOS, thereby inhibiting the growth of SiO2 spheres. By changing the content of CDs added, the size of the SiO2 template changes accordingly. A series of nano-hollow carbon spheres were prepared through high-temperature treatment of as-obtained SiO2 spheres coated with PDA and then acid washing. Among them, HCN-60 with optimized size and hollow structure exhibited excellent potassium/sodium storage performance. This research provides a new idea for the rational design of high-performance carbon anodes.

Fully exposed (101) plane endowing CoSe anode with fast and stable potassium storage

Transition-metal selenides, especially cobalt selenides (CoSe), are widely regarded as a promising anode for potassium-ion batteries (KIBs) due to their high theoretical capacity and good electrical conductivity. However, CoSe easily suffers from a substantial volume change upon repeated cycling, leading to a fast capacity decay and poor cycling stability. Herein, a dual-carbon confined CoSe is successfully designed by using metal-organic frameworks as raw materials. Various characterizations disclose that the introduction of the extra carbon phase is conducive to the growth of (101) plane of CoSe, and based on this, rationally regulating carbonization temperature can further promote the exposure of (101) plane. Such fully exposed (101) plane not only provides sufficient active surface to uptake K-ions, but also favors the accommodation of electrode structure fluctuation, accounting for a high capacity and prolonged cycle lifespan. As a result, the optimized sample (denoted as 750 °CNC@CoSe/NC) delivers 392.5 mAh g−1 at 0.5 A g−1, accompanied by an excellent cycling stability over 400 cycles with 196.7 mAh g−1 at a high current density of 1 A g−1. This work is expected to offer effective guidance for constructing advanced CoSe anode toward KIBs.

Oxygen-driven bulk defect engineering in carbon to reduce voltage hysteresis for fast potassium storage at low voltage

Reducing the voltage hysteresis and enhancing the rate performance of carbon anode materials are critical for boosting the energy and power density of potassium-ion full-cell devices. In this study, we report an oxygen-driven bulk defect engineering in carbon to reduce the voltage hysteresis, enabling reversible and fast potassium storage at low voltage. Through high-concentration hydrothermal treatment, the oxidized pitch structure units undergo a process where oxygen bridge bonds are formed, resulting in the creation of interconnected bulk structures. The oxygen-containing functional groups are removed during carbonization, thereby introducing bulk defects into the carbon materials to enhance the kinetics of K+ insertion in the nanographite domains. The bulk carbon anode achieves low voltage hysteresis, high reversible capacity below 1 V (248 mAh g−1 at 0.05 A g−1) and high-rate (192 mAh g−1 at 1 A g−1). Additionally, the full cell exhibits a discharge plateau at approximately 3.1 V and high cyclic stability (95 % capacity retention from the 10th to the 120th cycle). This study presents a novel approach for constructing bulk defects in carbon materials to achieve efficient potassium storage at low potential, thus advancing the application of advanced carbon anodes in potassium-ion batteries.

Layered Potassium Titanium Niobate/Reduced Graphene Oxide Nanocomposite as a Potassium-Ion Battery Anode

HighlightsKTiNbO5 and KTiNbO5/reduced graphene oxide (rGO) nanocomposites were successfully synthesised via solvothermal methods. Optimising the rGO wt% yielded a composite with 12 wt% (KTNO/rGO-12). KTNO/rGO-12 was tested for its potassium storage performance, achieving a first charge capacity of 128.1 mAh g−1 and retaining 76.1% over 500 cycles at 20 mAh g−1.The mechanism of intercalation was examined, suggesting a potentially low-strain material, with both titanium and niobium redox activity contributing to the charge storage.

BiPO4 is embedded in reduced graphene oxide as an anode for potassium ion batteries

BiPO4/reduced graphene oxide (BiPO4/rGO) composites were prepared by solvothermal method and annealing process. In terms of cycle and rate performance, BiPO4/rGO composites surpasses BiPO4 when utilized as anode materials in potassium ion batteries (PIBs). The discharge capacity of BiPO4/rGO composite maintained 204 mAh/g after 500 cycles at 100 mA g−1. The capacity might reach 194 mAh/g at a high current density of 1000 mA g−1. Additionally, the electrochemical reaction mechanism of BiPO4/rGO composites in potassium ion batteries is studied using an ex-situ XRD test.

Mechanistic exploration of Co doping in optimizing the electrochemical performance of 2H-MoS2/N-doped carbon anode for potassium-ion battery

The 2H-MoS2/nitrogen-doped carbon (2H-MoS2/NC) composite is a promising anode material for potassium-ion batteries (PIBs). Various transition metal doping has been adopted to optimize the poor intrinsic electronic conductivity and lack of active sites in the intralayer of 2H-MoS2. However, its optimization mechanisms have not been well probed. In this paper, using Cobalt (Co) as an example, we aim to investigate the influence of transition metal doping on the electronic and mechanical properties and electrochemical performance of 2H-MoS2/NC via first-principles calculation. Co doping is found to be effective in improving the electronic conductivity and the areas of active sites on different positions (C surface, interface, and MoS2 surface) of 2H-MoS2/NC. The increased active sites can optimize K adsorption and diffusion capability/processes, where general smaller K adsorption energies and diffusion energy barriers are found after Co doping. This helps improve the rate performance. Especially, the pyridinic N (pyN), pyrrolic N (prN), and graphitic N (grN) are first unveiled to respectively work best in K kinetic adsorption, diffusion, and interfacial stability. These findings are instructive to experimental design of high rate 2H-MoS2/NC electrode materials. The roles of different N types provide new ideas for optimal design of other functional composite materials.

S/N co-doped hierarchical porous carbon from lignite as high-performance anode for potassium-ion batteries

Because of their lower prices and exceptional physicochemical features, hard carbon materials have received a lot of interest in potassium ion batteries (PIBs). However, the slow K+ transport kinetics and significant volume expansion make the use of carbonaceous materials in PIBs anodes difficult. Here, S/N co-doped hierarchical porous carbon composites are designed as anodes for PIBs using lignite as raw material. The S/N co-doped carbon composites produced feature a hierarchical porous structure, which ensures structural resilience and speeds up ion/electronic transport. S/N co-doping in the carbon matrix not only creates an abundance of defects and active sites for K+, but it also increases the distance between layers, allowing for more accessible K+ intercalation/deintercalation. As a result, when used as anodes for PIBs, the obtained S/N co-doped hierarchical porous carbon composites have a large reversible capacity of 347.5 mAh g−1 after 100 cycles at 0.1 A g−1 with a capacity retention of up to 94 %, as well as excellent long cycle stability of 136 mAh g−1 after 1500 cycles at 1.0 A g−1.

Green Ether Electrolytes for Sustainable High-voltage Potassium Ion Batteries.

Ether-based electrolytes are promising for secondary batteries due to their good compatibility with alkali metal anodes and high ionic conductivity. However, they suffer from poor oxidative stability and high toxicity, leading to severe electrolyte decomposition at high voltage and biosafety/environmental concerns when electrolyte leakage occurs. Here, we report a green ether solvent through a rational design of carbon-chain regulation to elicit steric hindrance, such a structure significantly reducing the solvent's biotoxicity and tuning the solvation structure of electrolytes. Notably, our solvent design is versatile, and an anion-dominated solvation structure is favored, facilitating a stable interphase formation on both the anode and cathode in potassium-ion batteries. Remarkably, the green ether-based electrolyte demonstrates excellent compatibility with K metal and graphite anode and a 4.2 V high-voltage cathode (200 cycles with average Coulombic efficiency of 99.64 %). This work points to a promising path toward the molecular design of green ether-based electrolytes for practical high-voltage potassium-ion batteries and other rechargeable batteries.

N-Doped Carbon Nanonecklaces as a Potassium-Ion Battery Anode

N-Doped Carbon Nanonecklaces as a Potassium-Ion Battery Anode

Investigating K+ Storage Behavior of Highly Graphitized Carbon Fibers as Anodes for a Potassium-Ion Battery.

Many problems of potassium-ion batteries (PIBs) are hidden under a low mass load of the active material. However, developing research based on areal capacity is challenging for PIBs, due to the lack of an anode capable of delivering a stable capacity of more than 1 mAh cm-2. This work investigates the K+ storage behavior of highly graphitized carbon fibers (HG-CF), which exhibit automatic structural adjustments to mitigate voltage polarization. The created defects and residual K+ in the structure favor the reversible insertion/deinsertion of K+. HG-GF after structural adjustment realizes a capacity of 2 mAh (1.13 cm-2) without K deposition and a stable cyclic stability (>500 h). In situ X-ray diffraction and in situ Raman spectra were used to detect defect formation and structural evolution during cycles. This work demonstrates the feasibility of HG-GF as an anode for PIBs and provides a suitable anode for further research of PIBs based on areal capacity.

Ultrathin Cobalt-Based Prussian Blue Analogue Nanosheet-Assembled Nanoboxes Interpenetrated with Carbon Nanotubes as a Fast Electron/Potassium-Ion Conductor for Superior Potassium Storage.

Rechargeable potassium-ion batteries (PIBs) are regarded as potential substitutes for industrial lithium-ion batteries in large scale energy storage systems due to the world's abundant potassium supplies. Althogh cobalt hexacyanocobaltate (CoHCC) exhibits broad potential as a PIB anode material, its performance is currently unsatisfactory. Herein, novel 5 nm scale ultrathin CoHCC nanosheet-assembled nanoboxes with interspersed carbon nanotubes (CNTs/CoHCC nanoboxes) are fabricated to realize a highly reactive PIB anode. The ultrathin CoHCC layers substantially accelerate electron conduction and provide numerous active sites, while the connected CNTs provide fast axial electron transport. Consequently, the optimized anode exhibits a remarkable discharge capacity of 580.9 mAh g-1 at 0.1 A g-1 and long-term stability with 71.3% retention over 1000 cycles. In situ and ex situ characterizations and density functional theory calculations are further employed to elucidate the K+ storage process and the reason for the enhanced performance of the CNTs/CoHCC nanoboxes.

Reduced Graphene Oxide Modulated FeSe/C Anode Materials for High-Stable and Long-Life Potassium-Ion Batteries.

Reduced graphene oxide (rGO) has been demonstrated to effectively enhance the potassium storage performance of transition metal selenides due to its robust mechanical properties and high conductivity. However, the impact of rGO on the electrode-electrolyte interface, a crucial factor in the electrochemical performance of potassium-ion batteries (PIBs), requires further exploration. In this study, we synthesized a seamless architecture of rGO on FeSe/C nanocrystals (FeSe/C@rGO). Comparative analysis between FeSe/C and FeSe/C@rGO reveals that the rGO layer exhibits robust adsorption energies towards EC and DEC, inducing the formation of organic-rich solid-electrolyte interphase (SEI) without damage to the structural integrity. Furthermore, incorporating rGO triggers K+ -ions into the double electrode layer (EDL), markedly improving the transport of K+ -ions. As a PIB anode, FeSe/C@rGO exhibits a reversible capacity of 332 mAh g-1 at 200 mA g-1 after 300 cycles, along with excellent long-term cycling stability, showcasing an ultralow decay rate of only 0.086 % per cycle after 1900 cycles at 1000 mA g-1 .

Recent progress on metal-organic framework derived carbon and their composites as anode materials for potassium-ion batteries

Potassium-ion batteries (PIBs) are considered as promising alternatives to lithium-ion batteries (LIBs) due to their abundant potassium resources, cost-effectiveness, and comparable electrochemical performance to LIBs. However, the practical application of PIBs is hindered by the slow dynamics and large volume expansion of anode materials. Owing to their unique morphology, rich pores, abundant active sites, and tunable composition, metal-organic framework (MOF)-derived carbon and its composites have been widely studied and developed as PIB anodes. In this review, the basic configuration, performance evaluation indicators, and energy storage mechanisms of PIBs were first introduced, followed by a comprehensive summary of the research progress in MOF-derived carbon and its composites, especially the design strategies and different types of composites. Moreover, the advances of in situ characterization techniques to understand the electrochemical mechanism during potassiation/depotassiation were also highlighted, which is crucial for the directional optimization of the electrochemical performance of PIBs. Finally, the challenges and development prospects of MOF-derived carbon and its composites for PIBs are prospected. It is envisioned that this review will guide and inspire more research efforts toward advanced MOF-derived PIB anode materials in the future.