Anode For Potassium-ion Batteries Research Articles

Highly crystalline graphite nanofibers as an anode for high-performance potassium-ion batteries

Graphite nanofibres with high crystallinity and low defect levels for potassium-ion batteries with high initial Coulombic efficiency and long cycling stability are reported in this study.

SAXS unveils porous anodes for potassium-ion batteries: dynamic evolution of pore structures in Fe@Fe2O3/PCNFs composite nanofibers.

The porous structure of composite nanofibers plays a key role in improving their electrochemical performance. However, the dynamic evolution of pore structures and their action during ion intercalation/extraction processes for negative electrodes are not clear. Herein, porous carbon composite nanofibers (Fe@Fe2O3/PCNFs) were prepared as negative electrode materials for potassium-ion batteries. Electrochemical test findings revealed that the composites had good electrochemical characteristics, and the porous structure endowed composite electrodes with pseudo-capacitive behaviors. After 1500 discharge/charge cycles at a current density of 1000 mA g-1, the specific capacity of the potassium-ion batteries was 144.8 mAh g-1. We innovatively used synchrotron small-angle X-ray scattering (SAXS) technique to systematically investigate the kinetic process of potassium formation in composites and showed that the kinetic process of potassium reaction in composites can be divided into four stages, and the pores with smaller average diameter distribution are more sensitive to changes in the reaction process. This work paves a new way to study the deposition kinetics of potassium in porous materials, which facilitates the design of porous structures and realizes the development of alkali metal ion-anode materials with high energies.

A bimetallic sulfide FeCoS4@rGO hybrid as a high-performance anode for potassium-ion batteries.

We synthesized a low metal-to-sulfur atomic ratio (0.5) FeCoS4, exhibiting high reversible specific capacity. Reduced graphene oxide was covered on the surface to improve the cycling stability and rate performance further. Density functional theory calculations show that composite materials can effectively increase the adsorption energy and enhance the diffusion kinetics.

Advances in bismuth-based anodes for potassium-ion batteries

Bi-based materials with low cost, high capacity and suitable operating voltage are promising candidates for potassium-ion battery anodes. Rational optimization strategies are expected to bring them from laboratory to commercial applications.

Anisotropic lens-shaped mesoporous carbon from interfacially perpendicular self-assembly for potassium-ion batteries.

Anisotropic lens-shaped nitrogen-doped carbon (Lens-NMC) with unidirectionally aligned mesopores was achieved via perpendicular block copolymer self-assembly at the polymer interface. Lens-NMC is applied as a potassium-ion battery anode material as a next-generation battery system.

Deciphering Unexplored Reversible Potassium Storage and Small Volume Change in a CaV4O9 Anode with In Situ Transmission Electron Microscopy

AbstractVanadium‐based compounds are explored as promising electrode materials in lithium/sodium‐ion batteries exhibiting superior energy storage properties. However, similar attempts are rarely reported for potassium‐ion batteries (PIBs), in which the fundamental reaction mechanisms remain inexplicit. Herein, porous CaV4O9 nanobelts (NBs) are selected as a PIB anode to systematically investigate potassium storage mechanisms through in situ transmission electron microscopy. In situ measurements track overall electrochemical potassiation reactions of CaV4O9 and identify a polyphase state of V4O7, CaO, and K2O phases after potassiation. Unexpectedly, the potassiated products can be partially converted back to the original CaV4O9 phase with residual VO2 and CaO phases, which is different from the irreversible phase transformations in lithium/sodium storages of CaV4O9. Impressively, the cavities in NBs alternately disappear and appear with (de)potassiation, avoiding the drastic volume change and structural degradation of anodes. The reversible potassium storage and stable cycling are evaluated by electrochemical measurements and in situ X‐ray diffraction analysis. This work provides a paradigm by revisiting the existing anode materials in lithium/sodium‐ion batteries to seek out viable anodes for next‐generation PIBs.

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.