Anode Material For K-ion Batteries Research Articles

Confined graphitization induced pore generation for designing novel potassium-ion battery carbon anode with large capacity and ultra-long cycle life

Carbon is one of the most superior anode materials for K-ion batteries but faces the challenges of low capacity and poor cycle stability. In general, the K+ storage capacity depends on the graphitized carbon layers and defective structure, while the cycle stability can be enhanced by constructing sufficient nanospace to alleviate the volume expansion during the potassiation/depotassiation process. However, the above structures are difficult to integrate into a single carbon material because graphitization often eliminates defects and pore structures. In this work, we find that ultrathin carbon sheets have a confined graphitization effect, which allows the carbon layer to orientationally arrange at a low heating-treatment temperature. More importantly, this orientational arrangement causes size shrinkage, inducing structural splitting on the faces of the carbon sheets and producing abundant defects and a large number of pores. Based on this, we obtain a novel carbon with highly graphitized, large-surface-area and defect-rich frameworks, which gives a K+ storage capacity of 358 mAh g−1, and after 4000 cycles, this carbon shows no obvious capacity degradation, with a capacity retention rate of nearly 100 %. Carbon anodes of K-ion batteries with such large capacity and long cycling life have rarely been achieved before.

Adsorption of potassium atoms on twin T-graphene and twin-graphene surfaces for K-ion batteries

With the development of potassium-ion (K-ion) batteries, the search for two-dimensional materials with potassium storage potential has become a research hotspot. Twin T-graphene (TTG) and twin-graphene (TG) were studied as anode materials for K-ion batteries in terms of their adsorption energies, electronic structures, theoretical capacitances, diffusion barriers, and open circuit voltages (OCV) using first-principles calculations. Seven different adsorption sites of individual K atoms on TTG and TG were investigated. The most stable adsorption sites for TTG and TG were the H2 and B sites, respectively. After K atom adsorption, both semiconducting TTG and TG transform into metals, which facilitates K-ion diffusion and migration within the anode material. The K atoms were physically adsorbed on the TTG and TG surfaces, and the K adsorbed by TG was more stable than its TTG counterpart. Both TTG and TG could accommodate up to two layers of K atoms, with a maximum theoretical capacity of 372.22 and 496.30 mA·h/g, respectively. The average OCVs of TTG and TG were 1.12 and 1.58 V, while their diffusion barriers were 0.24 and 0.30 V, respectively. Therefore, TG has better theoretical capacity than TTG, while TTG excels in average OCV and diffusion barrier performance. This study underscores the broad potential applications of both TTG and TG as new energy materials for potassium storage.

Adsorption and diffusion of K in N-doped layered carbon TA-BGY with pores for anode of K ion batteries

The exploration of anode materials is important for the development of K-ion batteries (KIBs) as the promising alternative of Li-ion batteries. The large ionic radius of K ions greatly constrains the selection of anode materials. We propose the pores with appropriate size in structure can promote the storage of K ions. In this work, we studied the potential of layered carbon with pores as the anode of KIBs with TA-BGY as structural model by combining the first-principles calculations and molecular dynamical (MD) simulations. It is found that the doped N with lone electron pair can promote the adsorption of K ions at the edge of pore. The theoretical capacity of K can reach 796 mAh/g and the open circuit voltage is just 0.6 V. In addition, this structure has the low diffusion barrier of 0.48 eV and high structural stability under high K loading. We posit that N-doped layered carbon TA-BGY, featuring pores, holds the potential to serve as an exceptional anode material for KIBs.

Investigation of Sulfur Redox Chemistry in MoS2 Anodes for Potassium Ion Battery

Molybdenum disulfide (MoS2) with layered structure composed of molybdenum atoms coordinated with sulfur atoms makes it a suitable intercalation and conversion-based anode material for K-ion batteries (KIBs). But the electrochemical mechanism for K-ion storage in MoS2 remains unclear due to the probable occurrence of both conversion and polysulfide reactions. The formation of elemental sulfur (S0) due to irreversible conversion reaction of MoS2 is predicted to be a contributor for polysulfide reactions. Hence, in this study we utilised commercially available MoS2 as an anode for KIBs and studied the electrochemical performance by controlling the depth of discharge in the first cycle. It is identified that K-ion storage mechanism in MoS2 differs widely by operating at different discharge voltages. As a result, the characteristic voltage profile differs from the subsequent cycle, signifying dissimilar reaction pathways. Our results suggest that by controlling the depth of potassiation in MoS2, sulfur redox reactions co-exist along with conversion reaction. The existence of Mo metal and sulfur in the charge state is confirmed from various ex-situ spectroscopy studies. Moreover, formation of potassium polysulfides in the discharge state also strongly confirms the occurrence of sulfur redox reactions. Due to the dual reaction pathways, K-ion storage capacity is boosted up to 256 mAh g-1 and 93 mAh g-1 at 0.03 and 2 A g-1, respectively. The dual reaction also stabilizes the structure, which helps to attain a capacity retention of 84 % and 58 % after 500 and 1000 cycles, respectively. This study provides a mechanistic insight into the reaction pathway of K-ion storage in MoS2 when operating at various potential windows. Also, it may provide reference to utilising metal sulfides as a catalytic cathode in metal-sulfur batteries.

Relaxation of Stress Propagation in Alloying-Type Sn Anodes for K-Ion Batteries.

Alloying-type metallic tin is perceived as a potential anode material for K-ion batteries owing to its high theoretical capacity and reasonable working potential. However, pure Sn still face intractable issues of inferior K+ storage capability owing to the mechanical degradation of electrode against large volume changes and formation of intermediary insulating phases K4 Sn9 and KSn during alloying reaction. Herein, the TiC/C-carbon nanotubes (CNTs) is prepared as an effective buffer matrix and composited with Sn particles (Sn-TiC/C-CNTs) through the high-energy ball-milling method. Owing to the conductive and rigid properties, the TiC/C-CNTs matrix enhances the electrical conductivity as well as mechanical integrity of Sn in the composite material and thus ultimately contributes to performance supremacy in terms of electrochemical K+ storage properties. During potassiation process, the TiC/C-CNTs matrix not only dissipates the internal stress toward random radial orientations within the Sn particle but also provides electrical pathways for the intermediate insulating phases; this tends to reduce microcracking and prevent considerable electrode degradation.

A Novel Two-Dimensional ZnSiP2 Monolayer as an Anode Material for K-Ion Batteries and NO2 Gas Sensing.

Using the crystal-structure search technique and first-principles calculation, we report a new two-dimensional semiconductor, ZnSiP2, which was found to be stable by phonon, molecular-dynamic, and elastic-moduli simulations. ZnSiP2 has an indirect band gap of 1.79 eV and exhibits an anisotropic character mechanically. Here, we investigated the ZnSiP2 monolayer as an anode material for K-ion batteries and gas sensing for the adsorption of CO, CO2, SO2, NO, NO2, and NH3 gas molecules. Our calculations show that the ZnSiP2 monolayer possesses a theoretical capacity of 517 mAh/g for K ions and an ultralow diffusion barrier of 0.12 eV. Importantly, the ZnSiP2 monolayer exhibits metallic behavior after the adsorption of the K-atom layer, which provides better conductivity in a period of the battery cycle. In addition, the results show that the ZnSiP2 monolayer is highly sensitive and selective to NO2 gas molecules.

Realization of Sn2P2S6-carbon nanotube anode with high K+/Na+ storage performance via rational interface manipulation–induced shuttle-effect inhibition and self-healing

Because the electrochemical performance of next-generation batteries is strongly affected by the electronic properties of their electrode materials, it is highly desirable to find ways to easily tune these properties. In this study, we synthesized a Mott–Schottky-type Sn2P2S6-carbon nanotube heterojunction with many heterointerfaces and accelerated interfacial electron/ion transfer as the anode material for K-ion batteries (KIBs) and Na-ion batteries (NIBs). The constructive built-in electric fields directly affect the quality and composition of the solid-electrolyte interphase, preventing the entrapment of K+/Na+ ions inside the electrode during charging, the abnormal aggregation and coarsening of Sn nanoparticles, polyphosphide and polysulfide shuttling, and the accumulation of detrimental intermediate phases. Moreover, SnPS3 nanocrystals experience reversible self-healing and regeneration during long-lasting recharge reactions. In the KIBs, the composite delivers an initial discharge capacity of 930 mAh g−1 (at 0.05 A g−1) and approximately 100% capacity retention at 1 A g−1 after 600 cycles; in the NIBs, the composite delivers an initial discharge capacity of 1400 mAh g−1 (at 0.1 A g−1) and an 80.62% retention at 1 A g−1 after 600 cycles. The concept implemented for the construction of heterostructures with regulated electronic band structures can be used to exploit the electrochemical properties of other emerging electrode materials.

A carboxylate- and pyridine-based organic anode material for K-ion batteries

In this work, a new carboxylate- and pyridine-based organic anode material was exploited in K-ion batteries. The results demonstrate the critical role of multiple active centers (CO and CN) in one molecule to enhance the electrochemical performance.

Theoretical study of SnS2 encapsulated in graphene as a promising anode material for K-ion batteries

Rechargeable batteries with superior electronic conductivity, large capacity, low diffusion barriers and moderate open circuit voltage have attracted amount attention. Due to abundant resources and safety, as well as the high voltage and energy density, potassium ion batteries (KIBs) could be an ideal alternative to next-generation of rechargeable batteries. Based on the density functional theory calculations, we find that the SnS2 monolayer expands greatly during the potassiumization, which limits its practical application. The construction of graphene/SnS2/graphene (G/SnS2/G) heterojunction effectively prevents SnS2 sheet from deformation, and enhances the electronic conductivity. Moreover, the G/SnS2/G has not only a high theoretical special capacity of 680 mAh g−1, but an ultra-low K diffusion barrier (0.08 eV) and an average open circuit voltage (0.22 V). Our results predict that the G/SnS2/G heterostructure could be used as a promising anode material for KIBs.

N-doped three-dimensional porous carbon materials derived from bagasse biomass as an anode material for K-ion batteries

To realize the sustainability of potassium-ion (K-ion) batteries for large-scale energy storage applications, a resource-abundant and cost-effective anode material is the key to design. Herein, we develop nitrogen-doped three-dimensional biomass porous activated carbon materials using bagasse biomass waste by carbonization and further activation with NiCl2 and urea as an advanced anode material for K-ion batteries. The results demonstrate that NiCl2 is an important factor in the formation of porous structure and nitrogen doping also promotes the change of morphology, enabling fast transport of K+ and electrons. More importantly, the as-synthesized carbon material could exhibit a superior K-storage property with a reversible capacity of 100.4 mAh g−1 at a current density of 200 mA g−1 over 400 cycles without any obvious capacity fading in K-ion batteries. This work provides significant guideline for structural design in large-scale application.

Balsa wood derived three-dimensional hierarchical porous carbon materials as an anode material for K-ion batteries

Balsa wood derived three-dimensional hierarchical porous carbon materials as an anode material for K-ion batteries

SnSe nanocomposite chemically-bonded with carbon-coating as an anode material for K-ion batteries with outstanding capacity and cyclability

• A chemically bonded, nanosize SnSe@C composite is fabricated by a scalable method. • The chemically bonded SnSe@C nanocomposite anode is explored for use in K-ion batteries. • The use of amorphous carbon and selenium can significantly suppress the volume expansion of SnSe. • The chemically bonded SnSe@C nanocomposite exhibits excellent cyclability and rate capability. The use of SnSe alloys as anode materials in potassium-ion batteries (PIBs) has recently attracted considerable attention owing to the natural abundance of Sn and Se and the environmental friendliness, high theoretical capacity, and 2D layered structure of SnSe. However, due to the large volumetric change and severe pulverisation during potassiation and depotassiation, they exhibit poor cycling stability in PIBs. In this work, we fabricated a strongly chemically bonded SnSe@C nanocomposite using a simple two-step process consisting of a facile chemical reaction followed by high-energy ball milling. In addition, the introduction of amorphous carbon and selenium effectively suppressed the stress/strain originating from volume expansion during potassiation/depotassiation. The chemically bonded SnSe@C nanocomposite exhibited high initial discharge and charge capacities of 744.8 and 440.7 mAh g −1 , respectively. Even after 50 cycles, it retained a charge capacity of 401 mAh g −1 at 50 mA g −1 , with a coulombic efficiency (CE) of 99.6%. Even at high specific currents of 300 and 500 mA g −1 , the electrode maintained capacities of 270.7 and 203.4 mAh g −1 after 100 and 1000 cycles, respectively, and the CE was almost 100%. Furthermore, a SnSe@C/KFe[Fe(CN) 6 ·xH 2 O] full cell also showed superior cyclability and better rate capability. After 100 cycles, it retained a discharge capacity of 213.9 mAh g −1 at 200 mA g −1 . In addition, the phase transitions in the SnSe@C electrode during potassiation/depotassiation were investigated using ex-situ X-ray diffraction analysis. This work will provide an effective reference for Sn-Se alloy-based anodes for batteries to replace the lithium-ion batteries (LIBs).

Effect of the external metal on the electrochemical behavior of M3[Co(CN)6]2 (M: Co, Ni, Cu, Zn), towards their use as anodes in potassium ion batteries

A series of crystalline-cubic Prussian blue analogues (PBA) M3[Co(CN)6]2 (M=Co, Ni, Cu, Zn) were straightforwardly synthesized via the coprecipitation method as confirmed by X-ray diffraction and FTIR spectroscopy. These transition metal hexacyanocobaltates show electrochemical activity related to reversible K-ion storage between 0.05-2.6 V vs Ko/K+, that makes them suitable as anode-materials in K-ion batteries. The non-steady open circuit potential (OCP) observed in cells containing Cu3[Co(CN)6]2 and Zn3[Co(CN)6]2 electrodes suggests the presence of spontaneous redox reactions at the electrolyte/PBA interface, which leads to the loss of electrochemical activity with the time. On the other hand, the Co3[Co(CN)6]2 and Ni3[Co(CN)6] show extended -stability periods and multiple reduction/oxidation reactions which lead to the reversible charge storage mechanism. From an in-depth electrochemical study on the Co3[Co(CN)6]2-PBA, used as reference, an improvement on capacity retention is observed when the electrode is discharged at high negative potentials, 0.2 V vs Ko/K+, possibly due to the beneficial effect of a different electrochemical reaction on the PBA surface. The Ni3[Co(CN)6]2-PBA does not follow this trend, suggesting a different kinetics for this reaction on the particle surface, avoiding to observe its favorable effect as in the case of the Co3[Co(CN)6]2. This is the first time that transition metal-modified hexacyanocobaltates are reported as anode materials for K-ion batteries; particularly the Ni3[Co(CN)6]2-PBA exhibits specific capacities as high as ~ 310 mA h g−1 in the first discharge making it a promising material for applications in novel energy-storage technologies as K-ion batteries.

A computational study on the BN and AlN nanocones as anode materials for K-ion batteries

The potential application of BN nanocone (BNNC) and AlN nanocone (AlNNC) as the anode material for the potassium-ion batteries (PIBs) was explored by means of the density functional theory calculations. The K cation adsorbed over the center of the apex ring of BNNC and AlNNC with the adsorption energies of −24.1 and −38.0 kcal/mol, respectively. While the K atom was physically adsorbed with a small adsorption energy. The maximum energy barrier which should be passed by the K cation to migrate over the surface of BNNC and AlNNC is 7.2 and 5.7 kcal/mol, respectively. These values are very small which yield a high ion mobility and quick charge/discharge rate. The minimum diffusion coefficient for K cation on the BNNC or AlNNC is computed to be 9.72 × 10−8 or 2.89 × 10−6 cm2/s. The cell voltage belonging to BNNC or AlNNC are nearly 0.90 or 1.47 V. We concluded that the AlNNC is a more promising anode material for PIB compared to the BNNC because of its higher voltage, ion mobility, and diffusion coefficient. By using diethyl ether as a solvent, the cell voltage is decreased by about 0.03 and 0.15 V in the case of BNNC and AlNNC, respectively.

Tempura-like carbon/carbon composite as advanced anode materials for K-ion batteries

An advanced tempura-like carbon/carbon composite featuring robust encapsulation structure and effective S doping is prepared via a facile process, exhibiting impressive K-storage properties. Moreover, K-storage mechanism and reasons of performance improvement are also confirmed. • An advanced carbon/carbon composite with tempura-like morphology is prepared successfully. • Impressive K-storage properties include excellent rate capability and long cycle life. • The K-storage mechanism is revealed by a series of measurements and analyses. • Electrochemical kinetics, capacitive contribution, and DFT calculation are investigated. Graphite as a promising anode candidate of K-ion batteries (KIBs) has been increasingly studied currently, but corresponding rate performance and cycling stability are usually inferior to amorphous carbon materials. To protect the layer structure and further boost performance, tempura-like carbon/carbon nanocomposite of graphite@pitch-derived S-doped carbon (G@PSC) is designed and prepared by a facile and low-temperature modified molten salt method. This robust encapsulation structure makes their respective advantages complementary to each other, showing mutual promotion of electrochemical performances caused by synergy effect. As a result, the G@PSC electrode is applied in KIBs, delivering impressive rate capabilities (465, 408, 370, 332, 290, and 227 mA h g −1 at 0.05, 0.2, 0.5, 1, 2, and 5 A g −1 ) and ultralong cyclic stability (163 mA g −1 remaining even after 8000 cycles at 2 A g −1 ). On basis of ex-situ studies, the sectionalized K-storage mechanism with adsorption (pseudocapacitance caused by S doping)-intercalation (pitch-derived carbon and graphite) pattern is revealed. Moreover, the exact insights into remarkable rate performances are taken by electrochemical kinetics tests and density functional theory calculation. In a word, this study adopts a facile method to synthesize high-performance carbon/carbon nanocomposite and is of practical significance for development of carbonaceous anode in KIBs.

Facile synthesis of Fe-based metal-organic framework and graphene composite as an anode material for K-ion batteries

We have reported an iron-based metal-organic framework (MOF-235) and graphene composite as a suitable anode host in the up-coming K-ion batteries. The bulk MOF-235 delivers poor K-storage performance and large electrochemical polarization due to its inherent poor electronic conductivity. Accordingly, a modified hydrothermal reaction was performed to contrast a MOF-235 and graphene (G) composite and the as-prepared MOF-235+20G composite could deliver a remarkable capacity of 180 mAh/g over 200 cycles at a current density of 200 mA/g. Due to the addition of the two-dimensional layered conductive graphene, the electronic conductivity of the composite could be significantly improved. And the MOF-235 single crystal can be evenly embedded in the surface or interlayer of graphene to prevent the agglomeration phenomenon of the active material. Furthermore, the active material can be fully utilized during charging and discharging processes which is more conductive to the rapid transport of K+ and electron.

Flexible C6BN Monolayers As Promising Anode Materials for High-Performance K-Ion Batteries.

K-ion batteries attract extensive attention and research efforts because of the high energy density, low cost, and high abundance of K. Although they are considered suitable alternatives to Li-ion batteries, the absence of high-performance electrode materials is a major obstacle to implementation. On the basis of density functional theory, we systematically study the feasibility of a recently synthesized C6BN monolayer as anode material for K-ion batteries. The specific capacity is calculated to be 553 mAh/g (K2C6BN), i.e., about twice that of graphite. The C6BN monolayer is characterized by high strength (in-plane stiffness of 309 N/m), excellent flexibility (bending strength of 1.30 eV), low output voltage (average open circuit voltage of 0.16 V), and excellent rate performance (diffusion barrier of 0.09 eV). We also propose two new C6BN monolayers. One has a slightly higher total energy (0.10 eV) than the synthesized C6BN monolayer, exhibiting enhanced electronic properties and affinity to K. The other is even energetically favorable due to B–N bonding. All three C6BN monolayers show good dynamical, thermal, and mechanical stabilities. We demonstrate excellent cyclability and improved conductivity by K adsorption, suggesting great potential in flexible energy-storage devices.

AlN nanotubes and nanosheets as anode material for K-ion batteries: DFT studies

We explored the possible application of (5,0), (6,0), (7,0), (8,0) and (9,0) zigzag AlN nanotubes and an AlN nanosheet in the K-ion batteries (KIBs) using B3LYP-gCP-D3/6-31G* model chemistry. In the case of (5,0) tube, the K and K+ adsorption energies, maximum energy barrier for K+ migration, ion diffusion coefficient, and cell voltage are calculated to be −1.22 and −0.32 eV, 0.36 eV, 8.58×10−8 cm2/s, and 0.90 V, respectively. We found that dispersion term (D3) has much more significant effect on the K/K+ adsorption energies compared to the basis set superposition error (gCP). Reducing the AlN nanostructure curvature, the K atom interaction significantly weakens while the K+ interaction is slightly affected. As a result, the cell voltage increases by decreasing the AlN curvature, and reached to 1.11 V in the AlN sheet. The AlN nanostructures with lower curvature may be plausible candidates for application in the anode of KIBs.

Exploration of low-cost microporous Fe(Ⅲ)-based organic framework as anode material for potassium-ion batteries

Potassium-ion (K-ion) batteries were regarded as the promising candidate for increasingly large-scale energy storage system, mainly due to the abundant resources, low standard potential as well as fast ion transport capability. Exploring suitable anode materials that can fully accommodate the large ionic radius of K+ have been a research hotspot. Herein, a low-cost iron based metal organic framework, namely MOF-235 was initially proposed as newly anode material for K-ion batteries. After in-situ composited with multiwall-carbon tubes (MCNTs), the as-prepared MOF-235/MCNTs composite can show a specific capacity of 132 mAh g−1 over 200 cycles with remarkable rate property. The reaction mechanism was further investigated by XRD, FT-IR and XPS analysis. The superior K-storage behavior were ascribed to the large surface area of MOF-235, the enhanced electronic conductivity and the organic terephthalate moiety as the active site. These results are of significant to explore advanced anode materials for K-ion batteries.

A novel selenium-phosphorous amorphous composite by plasma assisted ball milling for high-performance rechargeable potassium-ion battery anode

Potassium-ion batteries (PIBs) are becoming one of the promising alternative metal-ion battery systems to lithium-ion batteries due to the abundance and low cost of potassium. Among the anode materials for the metal-ion battery systems, phosphorus-based materials are attractive due to the low cost and their high theoretical-specific capacity. Herein, for the first time, we report the selenium -phosphorous-carbon (Se–P–C) amorphous composites prepared by the plasma-assisted ball milling method as the high-performance anode material for PIBs. In particular, when the amorphous Se–P composite anode with the molar ratio of 1:2 and the P-milling time of 30 h (Se–2P/C@30 h), the associated PIB delivers a high reversible capacity of 634 mA h g−1 at a current density of 0.05 A g−1 and excellent rate capability of 248.6 mA h g−1 at a current density of 1 A g−1. Furthermore, the experimental characterization and analysis reveal the reaction mechanisms that K–P (K2P3) and K–Se (KSe) phases are formed during the potassiation process. The present work provides a facile approach to achieve a promising anode material for K-ion batteries, and the preparation route can be viewed as a reference for the further development of phosphorous-based anodes with high capacity and long cycle life for PIBs.