Anode Material For Potassium-ion Batteries Research Articles

Pyrolysis fuel oil-derived hollow carbon nanocages as high-stability anode materials for potassium ion storage

The use of graphite to make anode materials for potassium-ion batteries (KIBs) results in diminished electrochemical performance, largely due to significant interlayer expansion caused by potassation/depotassiation. To address this limitation, novel hollow carbon nanocages (HCNCs) are prepared from pyrolysis fuel oil (PFO), a cost-effective byproduct. The HCNCs heat-treated at 1500 °C has a graphitic structure with high porosities and numerous closed pores and exhibits a notable potassium-ion storage capacity of 307.2 mAh/g at a current density of 50 mA g−1. Moreover, structurally stable HCNCs withstand the substantial volume expansion associated with potassium-ion intercalation. The stability of the material is attributed to a hybrid adsorption/insertion mechanism, which results from synergistic interplay between the unique morphologies of the HCNCs and the developed carbon layers. This configuration delivers a specific capacity of 131.6 mAh/g and 98.9 % capacity retention over 1000 cycles at a high current density of 2000 mA g−1. Consequently, these proposed HCNCs present a significant advance in developing efficient carbon materials for KIBs, and addressing the critical challenges of graphite such as unstable cycling stability.

Nanomesh NiO-modified carbon cloth for highly efficient self-supporting potassium metal anodes

Potassium metal is one of the most promising anode materials for potassium-ion batteries owing to its low cost and ability to withstand high current density and relatively low operating potential. However, it is restricted from being used in practical implementations because of its high reactivity and disordered dendrite growth. To circumvent these issues, we stabilize potassium metal anodes by growing NiO with high potassium affinity and interconnected network porous structure on carbon cloth fibers (CC-NiO). A symmetric cell assembled from a composite material formed by infiltrating molten K into CC-NiO (K@CC-NiO) can cycle stably for 1840 h at a low overpotential of 33 mV. Furthermore, the first-cycle discharge capacities of the full batteries with carbon nanotubes-interwoven KFeSO4F microspheres (KFSF@CNTs) and perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) as the cathodes are 101.4 and 105.1 mAh g−1, respectively. The capacity retention of KFSF@CNTs||K@CC-NiO full battery after 1000 cycles is 79.3 %, and the capacity retention of PTCDA||K@CC-NiO full battery after 800 cycles is 70.2 %. The strategy of utilizing NiO as an efficient potassium metal nucleation anchor opens up a new direction for the development of high-energy and long-cycle-life potassium metal batteries.

Cellulose nanocrystal-derived carbon electrodes for sustainable potassium-ion charge storage systems

We have here produced carbon electrode materials derived from Crystalline NanoCellulose (CNC) for low-cost potassium-ion based energy storage systems through conventional annealing as well as through a fast and energy efficient microwave assisted carbonization process. A two-step 4-minute synthesis with ZnCl2 activation in a domestic microwave leads to a micro/mesoporous carbon with high surface area (SBET∼1800 m2 g−1). These CNC-derived carbons, if assessed in symmetric supercapacitor C/C cells cycled with 0.5 M K2SO4 aqueous electrolyte, show reversible capacitance values up to 66 F g−1 at current densities of 5 A g−1, retaining 83% of its initial capacitance after 10.000 cycles without any conducting additive. Due to its large electrochemical window of 1.7 V, a competitive energy density for an aqueous system of 20.9 W h kg−1 is achieved. A hybrid aqueous capacitor built with this carbon as negative electrode and coupled with a Prussian White as positive results in cell capacitance values up to 135 F g−1 under a voltage operation window of 1.8 V in 0.5 M K2SO4. On the other hand, non-activated carbons produced through a 2.25 hour thermal annealing at 900 °C, present much lower surface area (SBET∼450 m2 g−1), most of it due to its high micropore volume. This low external and mesoporous surface area carbon is a competitive anode material for potassium-ion batteries with a reversible capacity of ∼200 mA h g−1 cycled at 28 mA g−1 using 3.9 M KFSI in DME electrolyte (favourably most of it below 1 V vs K+/K) in a potassium half-cell with >80% retention in 100 cycles. The present research shows that sustainable CNC derived carbons produced through energy efficient methods are competitive electrode materials in low-cost K based energy storge systems.

Bimetallic alloy nanoparticles embedded in N-doped carbon-based as an anode for potassium-ion storage material

Metal-organic frameworks (MOFs) have great potential as anode materials for potassium-ion batteries (PIBs) due to their hierarchical porous structures, large number of reaction sites, and adjustable chemistry. However, the larger size of potassium ions adversely impacts the electrochemical performance and specific capacity. Therefore, it is imperative to develop novel electrode materials featuring distinctive structures for PIBs. This study achieved bimetal introduction by adding Ammonium ferric citrate during ZIF-67 growth. The resulting metal–organic skeleton of the bimetallic alloy nanoparticle (FeCo@PAZ-C) exhibits a core–shell structure and adorned with numerous microspheres on its surface, thereby offering an abundance of active sites for K+ storage. This architecture effectively reduces the diffusion path length for potassium ions and enhances electron transport pathways, ultimately contributing to improved performance. At 100 mA g−1 and after 500 cycles, the FeCo@PAZ-C electrode material demonstrated a stable specific capacity of 328 mAh/g with 95 % capacity retention. This self-sacrificing template method for MOFs offers a new approach to developing high-capacity and cycling-stable potassium-ion battery materials, broadening their potential applications.

Liquid phase oxidation enables stable soft carbon anodes for potassium-ion batteries

Soft carbon has been recognized as a promising anode material for potassium-ion batteries (PIBs), due to low cost, high conductivity and low voltage platform. However, their practical application is hampered by slow storage kinetics and unsatisfactory cycle life. In this work, pitch-derived needle coke, a typical soft carbon, was incorporated with oxygenated functional groups through liquid phase oxidation by using H2O2 oxidant. When used as anode materials for PIBs, the oxidized needle coke delivers a high reversible capacity of 322.7 mAh g−1, significantly superior to that of the needle coke (237.9 mAh g−1). The enhanced electrochemical performance can be attributed to the abundant oxygenated functional groups and resultant defects on the surface of oxidized needle coke, which not only serve as extra active sites for potassium storage, but also provide sufficient pathways for K+ migration across the adjacent carbon layers. Moreover, the expanded interlayer spacing derived from H2O2 oxidation facilitates rapid K+ intercalation and deintercalation. This work offers an effective modification strategy for the fabrication of high-performance pitch-based soft carbon anodes for PIBs.Graphical

Boosting Potassium Adsorption and Diffusion Performance of Carbon Anodes for Potassium-Ion Batteries via Topology and Curvature Engineering: From KT-Graphene to KT-CNTs.

We propose a two-dimensional carbon allotrope (named KT-graphene) by incorporating kagome and tetragonal lattices consisting of trigonal, quadrilateral, octagonal, and dodecagonal rings. The introduction of non-hexagonal rings can give rise to the localized electronic states that improve the chemical reactivity toward potassium, making KT-graphene a high-performance anode material for potassium-ion batteries. It shows a high theoretical capacity (892 mAh g-1), a low diffusion barrier (0.33 eV), and a low average open-circuit voltage (0.51 V). The presence of electrolyte solvents is propitious to boost the K-ion adsorption and diffusion capabilities. Moreover, one-dimensional nanotubes (KT-CNTs), rolled up by the KT-graphene sheet, are metallic regardless of the tube diameter. As the curvature increases, KT-CNTs exhibit significantly increased surface activity, which can promote the electron-donating ability of K. Furthermore, the curvature effect greatly enhances the efficiency of K diffusion on the inner surface compared to that on the outer surface.

Encapsulating Bi Nanoparticles in Reduced Graphene Oxide with Strong Interfacial Bonding toward Advanced Potassium Storage.

Bismuth (Bi) is regarded as a promising anode material for potassium ion batteries (PIBs) due to its high theoretical capacity, but the huge volume expansion during potassiation and intrinsic low conductivity cause poor cycle stability and rate capability. Herein, a unique Bi nanoparticles/reduced graphene oxide (rGO) composite is fabricated by anchoring the Bi nanoparticles over the rGO substrate through a ball-milling and thermal reduction process. As depicted by the in-depth XPS analysis, strong interfacial Bi-C bonding can be formed between Bi and rGO, which is beneficial for alleviating the huge volume expansion of Bi during potassiation, restraining the aggregation of Bi nanoparticles and promoting the interfacial charge transfer. Theoretical calculation reveals the positive effect of rGO to enhance the potassium adsorption capability and interfacial electron transfer as well as reduce the diffusion energy barrier in the Bi/rGO composite. Thereby, the Bi/rGO composite exhibits excellent potassium storage performances in terms of high capacity (384.8 mAh g-1 at 50mA g-1 ), excellent cycling stability (197.7 mAh g-1 after 1000 cycles at 500mA g-1 with no capacity decay) and superior rate capability (55.6 mAh g-1 at 2 A g-1 ), demonstrating its great potential as an anode material for PIBs.

Needle coke anodes for potassium-ion batteries: Storage mechanism and interfacial evolution in soft carbon

Needle coke has attracted much attention as soft carbon anode material for potassium-ion batteries (PIBs) owing to its high crystallinity and conductivity. However, limited research has been conducted on the storage mechanism and the functional and structural evolution of the solid electrolyte interphase (SEI) in ester and ether based electrolytes. This work investigates the potassium ion storage mechanisms of soft carbon anodes in three electrolytes: KPF6 EC/DEC, KPF6 DME, and KFSI DME, and reveals that K+ stored in the KPF6 EC/DEC electrolyte could be through an “adsorption-intercalation” mechanism. Whereas K+ stored in the DME-based electrolytes is believed to undergo a “co-intercalation/adsorption-intercalation” process. Interfacial analyses indicate that the SEI formed in the EC/DEC electrolyte inhibits co-intercalation of potassium ion and solvent, which preserves sufficient space to accommodate potassium ion. Conversely, the [K-DME]+ solvation co-intercalation in DME-based electrolytes compromises the structural integrity, and results in a persistent capacity decline. This work offers novel insights into potassium ion storage in ester and ether-based electrolytes, and provides theoretical support for the fabrication of high-performance soft carbon anodes.

Realizing Low-Temperature Graphite-based Rechargeable Potassium-Ion Full Battery.

Graphite (Gr) has been considered as the most promising anode material for potassium-ion batteries (PIBs) commercialization due to its high theoretical specific capacity and low cost. However, Gr-based PIBs remain unfeasible at low temperature (LT), suffering from either poor kinetics based on conventional carbonate electrolytes or K+ -solvent co-intercalation issue based on typical ether electrolytes. Herein, a high-performance Gr-based LT rechargeable PIB is realized for the first time by electrolyte chemistry. Applying unidentate-ether-based molecule as the solvent dramatically weakens the K+ -solvent interactions and lowers corresponding K+ de-solvation kinetic barrier. Meanwhile, introduction of steric hindrance suppresses co-intercalation of K+ -solvent into Gr, greatly elevating operating voltage and cyclability of the full battery. Consequently, the as-prepared Gr||prepotassiated 3,4,9,10-perylene-tetracarboxylicacid-dianhydride (KPTCDA) full PIB can reversibly charge/discharge between -30 and 45 °C with a considerable energy density up to 197 Wh kgcathode -1 at -20 °C, hopefully facilitating the development of LT PIBs.

Facile Fabrication of Porous MoSe2/Carbon Microspheres via the Aerosol Process as Anode Materials in Potassium-Ion Batteries

Recently, potassium-ion batteries (KIBs) have attracted significant interest due to a number of factors, including the growing demand for energy and limited lithium resources. However, their practical use is hampered by poor cycling stability due to the large size of K+. Therefore, it is critical to develop a structural design that effectively suppresses large volume changes. This study presents a simple method of using a salt template to fabricate porous microspheres (p-MoSe2@C MS) of MoSe2 and a carbon matrix as anode materials in KIBs. These microspheres have a distinct porous design, with uniformly distributed MoSe2 nanocrystals embedded in the carbon matrix to prevent MoSe2 overgrowth due to material diffusion during heat treatment. The manufacturing process combined one-step spray drying with recyclable NaCl as a hard template. Through a two-step thermal process under an inert atmosphere, the initial dextrin, NaCl, and Mo salt microspheres were converted into a p-MoSe2@N MS composite. The carbon structure derived from the dextrin maintained the shape of the microspheres when NaCl was removed, ensuring no overgrowth of MoSe2. This well-designed porous structure improves the interaction with the electrolyte, facilitating the transport of ions and electrons and reducing the K+ diffusion distances. In addition, the porous carbon structure accommodates large volume changes during cycling and maintains its structural strength. As a result, p-MoSe2@C MS composite exhibits superior electrochemical properties, with remarkable capacity, long-term cycling stability (193 mA h g−1 after 500 cycles at 2.0 A g−1), and rate capability.

Ginger-derived hierarchical porous carbon as an anode material for potassium-ion batteries and capacitors

Carbonaceous materials are ideal as an anode for potassium-ion batteries (KIBs) because of their low cost, tunable physiochemical properties, and excellent reversible intercalation of potassium-ions (K+).

Peapod-Like Structured B/N Co-Doped Carbon Nanotube Array Encapsulating MxPy (M = Fe, Co, and Ni) Nanoparticles for High-Rate Potassium Storage.

Potassium-ion batteries (PIBs) have become the desirable alternatives for lithium-ion batteries (LIBs) originating from abundant reserves and appropriate redox potential, while the considerable radius size of K+ leading to poor reaction kinetics and huge volume expansion limits the practical application of PIBs. Hybridization of transition-metal phosphides and carbon substrates can effectively optimize the obstacles of poor conductivity, sluggish kinetics, and huge volume variation. Thus, the peapod-like structural MxPy@BNCNTs (M = Fe, Co, and Ni) composites as anode materials for PIBs were synthesized through a facile strategy. Notably, the unique architecture of B/N codoped carbon nanotube array as fast ion/electron transfer pathways effectively improves the electronic conductivity of composites. The MxPy nanoparticles (NPs) are encapsulated in BNCNTs with an amorphous carbon layer (5-10 nm), which discernibly alleviate the volume changes during potassiation/depotassiation. In conclusion, the composites show a commendable cycling performance, possessing reversible capacities of 111, 152, and 122 mA h g-1 after 1000 cycles at 1.0 A g-1 with a negligible capacity loss for FeP@BNCNT, CoP/Co2P@BNCNT, and Ni2P@BNCNT electrodes, respectively. Especially, after 1000 cycles at 2.0 A g-1, the CoP/Co2P@BNCNT electrode still possesses a capacity of 87.9 mA h g-1, demonstrating excellent rate performance and long-term life. This work may offer an innovative and viable route to construct a stable architecture for solving the issue of poor stability of TMP-based anodes at a high current density.

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.

First-principles study of bismuthene as a high energy density and excellent rate performance anode material for potassium-ion batteries

Potassium-ion batteries (KIBs), with their abundance of resources, lower cost, high ion conductivity, and comparable redox potential, hold potential as an alternative to lithium-ion batteries (LIBs) for large-scale energy storage. Nonetheless, the scarcity of high-performance electrode materials remains a major obstacle in the advancement of KIBs. Here, the viability of bismuthene as an anode material for KIBs was systematically investigated using first-principles calculations. We found that bismuthene exhibits a maximum adsorption capacity of two layers of K atoms, offering a moderate theoretical capacity of 256.5 mAh g−1. Additionally, the adsorption of K atoms on bismuthene leads to a notable enhancement in the electronic conductivity. Moreover, the ultralow average open circuit voltage (0.17 V) and diffusion barrier (0.02 eV) of K on bismuthene monolayer along the zigzag direction, suggesting a high energy density and outstanding rate performance of batteries. Hence, bismuthene demonstrates remarkable potential as a high-performance KIBs anode material, making it a hopeful contender in the field of energy storage.

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.

Bilayer and Trilayer C3N/Blue-Phosphorene Heterostructures as Potential Anode Materials for Potassium-Ion Batteries.

Two-dimensional (2D) van der Waals heterostructures outperform conventional anode materials for postlithium-ion batteries in terms of mechanical, thermal, and electrochemical properties. This study systemically investigates the performance of bilayer and trilayer C3N/blue phosphorene (C3N/BlueP) heterostructures as anode materials for potassium-ion batteries (KIBs) using first-principles density functional theory calculations. This study reveals that the adsorption and diffusion of K ions on bilayer and trilayer C3N/BlueP heterostructures are markedly superior to those of their monolayer counterparts. A bilayer heterostructure (C3N/BlueP) effectively reduces the bandgap of the BlueP monolayer (1.98 eV) to 0.02 eV, whereas trilayer heterostructures (bilayer-C3N/BlueP and C3N/bilayer-BlueP) exhibit metallic behavior with no bandgap. Additionally, the theoretical capacity of the bilayer and trilayer heterostructures ranges from 636.7 to 755.5 mA h g-1, considerably higher than the theoretical capacity of other prospective 2D heterostructures for KIBs investigated in the literature. This study also shows that the heterostructures exhibit K-ion diffusion barriers as low as 0.042 eV, ensuring the relatively fast diffusion of K ions.

Simultaneous Catalytic Acceleration of White Phosphorus Polymerization and Red Phosphorus Potassiation for High-Performance Potassium-Ion Batteries.

Red phosphorus (P) as an anode material of potassium-ion batteries possesses ultra-high theoretical specific capacity (1154mAhg-1 ). However, owing to residual white P during the preparation and sluggish kinetics of K-P alloying limit its practical application. Seeking an efficient catalyst to address the above problems is crucial for the secure preparation of red P anode with high performance. Herein, through the analysis of the activation energies in white P polymerization, it is revealed that the highest occupied molecular orbital energy of I2 (-7.40eV) is in proximity to P4 (-7.25eV), and the lowest unoccupied molecular orbital energy of I2 molecule (-4.20eV) is lower than that of other common non-metallic molecules (N2 , S8 , Se8 , F2 , Cl2 , Br2 ). The introduction of I2 can thus promote the breaking of the P─P bond and accelerate the polymerization of white P molecules. Besides, the ab initio molecular dynamics simulations show that I2 can enhance the kinetics of P-K alloying. The as-obtained red P/C composites with I2 deliver excellent cycling stability (358mAhg-1 after 1200 cycles at 1Ag-1 ). This study establishes catalysis as a promising pathway to tackle the challenges of P anode for alkali metal ion batteries.

3D network and wrapping strategy derived loofah-like Sb@CNTs@C for high performance K+/Na+ storage

Antimony (Sb) has an ultra-high theoretical specific capacity and is a very promising anode material for potassium-ion batteries (PIBs) and sodium-ion batteries (SIBs). In this paper, carbon coated carbon nanotubes (CNTs) and Sb (Sb@CNTs@C) nanomaterials were efficaciously synthesized by way of a one-step solvothermal and thermal reduction method. As the anode material of PIBs, Sb@CNTs@C has decent electrochemical performance and good cycle stability. The initial charge specific capacities at 0.2 A g−1 is 974 mAh g−1. Even at 1 A g−1, 206 mAh g−1 is retained after 1000 cycles. As the anode material of SIBs, the Sb@CNTs@C exhibited a charging capacity of 221 mAh g−1 at 0.2 A g−1 after 1000 cycles. The loofah-like Sb@CNTs@C nanomaterial has good electrochemical properties, which is mainly due to the formation of a 3D network structure by Sb, CNTs and carbon coating. In response to the volume expansion problem of Sb in K+/Na+ storage, the loofah-like Sb@CNTs@C has constructed a good conductive network, provided sufficient volume expansion space, and also formed an effective protective layer.

Construction of Sugar-Gourd-Shaped Carbon Nanofibers Embedded with Heterostructured Zinc-Cobalt Selenide Nanocages for Superior Potassium-Ion Storage.

Transition metal selenides are considered as promising anode materials for potassium-ion batteries (PIBs) due to their high theoretical capacities. However, their applications are limited by low conductivity and large volume expansion. Herein, sugar-gourd-shaped carbon nanofibers embedded with heterostructured ZnCo-Se nanocages are prepared via a facile template-engaged method combined with electrospinning and selenization process. In this hierarchical ZnCo-Se@NC/CNF, abundant phase boundaries of CoSe2/ZnSe heterostructure can promote interfacial electron transfer and chemical reactivity. The interior porous ZnCo-Se@NC nanocage structure relieves volume expansion and maintains structural integrity during K+ intercalation and deintercalation. The exterior spinning carbon nanofibers connect the granular nanocages in series, which prevents the agglomeration, shortens the electron transport distance and enhances the reaction kinetics. As a self-supporting anode material, ZnCo-Se@NC/CNF delivers a high capacity (362mAhg-1 at 0.1Ag-1 after 100 cycles) with long-term stability (95.9% capacity retention after 1000 cycles) and shows superior reaction kinetics with high-rate K-storage. Energy level analysis and DFT calculations illustrate heterostructure facilitates the adsorption of K+ and interfacial electron transfer. The K+ storage mechanism is revealed by ex situ XRD and EIS analyses. This work opens a novel avenue in designing high-performance heterostructured anode materials with ingenious structure for PIBs.

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.