K-ion Batteries Research Articles

The outstanding electrochemical performance of porous hexagonal boron nitride as a K-ion battery anode

Within the current piece of research, we propose a porous model of hexagonal boron nitride (h-BN) monolayer (h-BNML) through DFT calculations in order develop an anode material for KIBs. We in particular focused on the impact of the pore on the diffusion of K ions and upon the storage process. We created the porous model of the h-BNML by using a pure h-BNML structure via the removal of B atoms which mimics the formation of the pore. Based on the DFT calculations, there was no change in the original planar structure of the h-BNML after the formation of the pore. There was a dramatic change in the electronic and structural attributes of the h-BNML indie the poor based on the introduced vacancies, which allowed the K-ion to adhere effectively within the pore. Based calculations demonstrated the interaction between the K ions and the pores through electrostatic attraction. The model exhibited the ability to keep a high number of K ions at its surface without any change in the initial planar structure of h-BN, which was closely associated with an increased theoretical specific capacity, which increased with porosity. Hence, the pore formation increased the diffusion of K ions in comparison with the pure h-BNML. This can be insightful to designing enhanced anode materials for KIBs. Finally, the current work can provide insights into tailoring porous BN materials for application in KIBs.

Density functional theory study on zigzag and armchair nanotubes of َAlP for potential K-ion battery application

The B3LYP-gCP-D3/6-31G* model was employed to explore the potential use of armchair AlP nanotube (A-AlPNT) and zigzag Z-AlPNT as anode materials for use in K-ion batteries (KIBs). The adhesion energy of K+ on the A-AlPNT or Z-AlPNT was found to be −46.6 or −43.1 kcal/mol, while the interaction with K atoms was weaker with an adhesion energy of −5.3 or −4.7 kcal/mol, respectively. The dispersion term was more crucial for K atom interaction than the adhesion of K+, contributing 63.1 and 4.1 % to the adsorption energy on Z-AlPNT, respectively. The cell voltage and maximum energy barrier for the migration of K+ were 1.67 V and 11.3 kcal/mol for Z-AlPNT and 1.79 V and 10.7 kcal/mol for A-AlPNT, respectively. This indicates that AlPNTs have excellent ion mobility with low energy barriers, which enable faster charge/discharge rates. The higher cell voltage and greater ion mobility suggest that A-AlPNTs are promising anode materials for KIBs when compared to Z-AlPNTs. We have also discussed the impact of K/K+ adsorption on the electronic properties of AlPNTs.

Sb Doping and Amorphization Co-Induced High Capacity and Excellent Durability of Tin Sulfide-Based Anode for K-Ion Batteries.

The carbon nanotubes (CNTs) supported amorphous Sb doped substoichiometric tin dulfide (Sb─SnSx ) with a carbon coating (the C/Sb─SnSx @CNTs-500) is reported to be an efficient anode material for K+ storage. The formation of the C/Sb─SnSx @CNTs-500 is simply achieved through the thermally induced desulfurization of tin sulfide via a controlled annealing of the C/Sb─SnS2 @CNTs at 500°C. When used for the K+ storage, it can deliver stable reversible capacities of 406.5, 305.7, and 238.4mAhg-1 at 0.1, 1.0, and 2.0Ag-1 , respectively, and shows no capacity drops when potassiated/depotassiated at 1.0 and 2.0Ag-1 for >3000 and 2400 cycles, respectively. Even at 10, 20, and 30Ag-1 , it can still deliver stable reversible capacities of 138.5, 85.1, and 73.8mAhg-1 , respectively. The unique structure, which combines the advantageous features of carbon integration/coating, metal doping, and desulfurization-induced amorphous structure, is the main origin of the high performance of the C/Sb─SnSx @CNTs-500. Specifically, the carbon integration/coating can increase the electric conductivity and stability of the C/Sb─SnSx @CNTs-500. The density function theorycalculation indicates that the Sb doping and the desulfurization can facilitate the potassiation and increase the electric conductivity of Sb─SnSx . Additionally, the desulfurization can increase the K+ diffusivity in Sb─SnSx .

Anode Properties of Sb-Based Alloy Electrodes for K-Ion Batteries in an Ionic-Liquid Electrolyte

Anode Properties of Sb-Based Alloy Electrodes for K-Ion Batteries in an Ionic-Liquid Electrolyte

A novel K-ion KVPO4F0.5O0.5/graphite full cell: Correlation between XPS SEI studies and electrochemical testing results

Like li- and Na-ion batteries, electrolyte reactivity (i.e., salt and solvent decomposition) is important in the electrochemical performance of K-ion batteries (KIBs). Indeed, X-ray photoelectron spectroscopy (XPS) analysis of a solid electrolyte interphase (SEI) in KIBs is still based on K-ion half-cells. This may lead to incorrect interpretations of the results considering the contamination of the studied electrode SEI due to the high K metal reactivity. Therefore, this study aims to provide a reliable XPS study without potassium metal, investigating the impact of various parameters, including open-circuit voltage (OCV) temperature, upper cut-off voltage (UCV), depth of discharge (DOD), and vanadium dissolution, on the electrochemical performance of KVPO4F0.5O0.5/graphite full cells. This work highlights the importance of SEI preformation, which is more pronounced at higher OCV temperatures. At specific UCV and DOD, the cell provides the best trade-off between the organic and inorganic passivation layer, leading to good electrochemical performance. The study also demonstrates that vanadium dissolution is a potential mechanism affecting capacity fading in K-ion batteries. Finally, understanding these SEI growth mechanisms should help researchers get reliable XPS analysis of the SEI in KIBs and move forward with the practical passivation layer characterizations.

K-Ion Slides in Prussian Blue Analogues.

We study the phenomenology of cooperative off-centering of K+ ions in potassiated Prussian blue analogues (PBAs). The principal distortion mechanism by which this off-centering occurs is termed a "K-ion slide", and its origin is shown to lie in the interaction between local electrostatic dipoles that couple through a combination of electrostatics and elastic strain. Using synchrotron powder X-ray diffraction measurements, we determine the crystal structures of a range of low-vacancy K2M[Fe(CN)6] PBAs (M = Ni, Co, Fe, Mn, Cd) and establish an empirical link between composition, temperature, and slide-distortion magnitude. Our results reflect the common underlying physics responsible for K-ion slides and their evolution with temperature and composition. Monte Carlo simulations driven by a simple model of dipolar interactions and strain coupling reproduce the general features of the experimental phase behavior. We discuss the implications of our study for optimizing the performance of PBA K-ion battery cathode materials and also its relevance to distortions in other, conceptually related, hybrid perovskites.

Prospective utilization of boron nitride and beryllium oxide nanotubes for Na, Li, and K-ion batteries: a DFT-based analysis.

In the present work, we investigated the adsorption mechanism of natural sodium (Na), potassium (K), and lithium (Li) atoms and their respective ion on two nanostructures: boron-nitride nanotubes (BNNTs) and beryllium-oxide nanotubes (BeONTs). The main goal of this research is to calculate the gain voltage for Na, K, and Li ionic batteries. Density function theory (DFT) calculations indicated that the adsorption energy between Na + is higher than that of the other cations, and this is particularly clear in the BeONT. Furthermore, gain voltage calculations showed that BNNTs generate a higher potential than BeONTs, with the most significant difference observed in BNNT/Na + . This research provides theoretical insights into the potential uses of these nanostructures as anodes in Na, K, and Li-ion batteries. Density function theory used to compute the ground state properties for BeONT and BNNT with and without selected atoms and their ions (Li, K, and Na). B3LYP used for exchange correlation between electrons and ions, and 6-31G* basis set used for all atoms and ions. Gauss Sum 2.2 software used for estimate the density of state (DOS) for all structure under investigation.

Stabilization of layered-type potassium manganese oxide cathode with fluorine treatment for high-performance K-ion batteries

Layered potassium manganese oxides (KxMnO2) have been widely investigated as potential cathode materials for K-ion batteries owing to their high capacity and low material cost. However, the KxMnO2 cathodes generally suffer from unsatisfactory cycle life due to Mn dissolution into the electrolyte triggered by acidic HF corrosion and structural stress at the particle surface during cycling. In this study, we introduce an efficient strategy to stabilize the aggressive chemistry between the organic electrolyte solution and the P′3-type K0·6MnO2 (KMO) cathode surface through fluorine treatment. KF-coated P′3-type K0.6MnO1.97F0.03 (KMOF-7) is prepared by introducing 7 mol% of ammonium fluoride (NH4F) during a pyro-synthesis of K0·6MnO2. The partial substitution of F to oxygen atom narrows the interlayer spacing, which helps to reduce the insertion of electrolyte molecules into the crystal structure; meanwhile, the formation of KF coating layer on the cathode surface can suppress the Mn dissolution by protecting KMOF-7 from reacting with HF in the electrolyte solution during charge–discharge processes. This strategy can relieve the structural stress and stabilize the interfacial stability of KMOF-7, thereby, facilitating K+ transportation and depress the charge transfer resistance upon cycling. The KMOF-7 cathode demonstrates the significantly improved cycling stability and power capability compared to KMO.

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.

Effect of pore morphology on the enhanced potassium storage in hard carbon derived from polyvinyl chloride for K-ion batteries

Effect of pore morphology on the enhanced potassium storage in hard carbon derived from polyvinyl chloride for K-ion batteries

Sustainably flexible and free-standing organic carbonyl potassium salt with continuous conductive network as high-performance anode in K-ion batteries

Developing suitable electrode materials with high flexibility, superior cyclic performance and low-cost have been the new topic and difficulty in the up-coming wearable flexible device. Herein, organic potassium terephthalate (K2TP) with MWCNTs and conductive polymer PEDOT:PSS co-coated K2TP/2MWCNTs/PP composite endowing continuous conductive network, was initially developed as a pliable and free-standing anode material for potassium ion batteries. By analyzing the internal microstructure, external topography and varies electrochemical characterization of the prepared samples, the incorporation of reasonable MWCNTs and PEDOT:PSS allows for the construction of a continuous conductive network with a large specific surface area, the creation of an effective electron transfer channel, an improvement in the kinetics of K+ diffusion and the maintenance of structural integrality. A preeminent specific capacity of 154.3 mAh g−1 can be maintained after 100 cycles at the current density of 50 mA g−1, prevailing over the majority of claimed anode materials employed in K-ion batteries. Furthermore, a high-performance all-organic full battery based on flexible anode and cathode material was successfully assembled delivering an extraordinary energy density of 320 Wh Kg−1. These results can put forward the practical application of organic electrode materials in systems for massive-scale energy storage.

Exploring the potential of di-boron di-nitride monolayer (o-B2N2) as a K-ion battery anode: A DFT study

Due to favorable future use of electrochemical energy storage systems in portable electronic devices, these systems have received much attention. Employing these systems in "smart" clothes equipped with piezoelectric pieces to gain energy from body movement and roll-up displays is promising. Nevertheless, further development of these technologies is a significant challenge due to lack of appropriate battery electrodes that supply desirable electrochemical performance. 2D flexible and light materials with remarkable chemical and physical attributes such as acceptable conductivity, high surface metal diffusivity, hydrophilic surfaces, and mechanical strengths were introduced as potential options for battery electrodes. In present research, 2D orthorhombic di-boron di-nitride monolayer (o-B2N2) as a novel 2D boron nitride allotrope has been investigated. Systematically, various impacting factors like their electrochemical and electronic features (theoretical capacity, equilibrium voltage, binding strength, etc.) were investigated. It is noteworthy that specific capacity of K-ion batteries (KIBs) reaches 2347 mAh.g-1. In addition, the existence of o-B2N2 ring accelerates the diffusion of K-ions, and diffusion barriers are 0.14 eV. Mean open circuit voltage (OCV) and low diffusion barrier of o-B2N2 monolayer guarantee long service life and fast charging/discharging for practical purposes. Based on results, monolayer o-B2N2 is proper as a high-performance negative electrode material in KIBs.

Anion Vacancy Regulated Sodium/Potassium Intercalation in Potassium Prussian Blue Analog Cathodes for Hybrid Sodium‐Ion Batteries

AbstractFe‐based potassium Prussian blue analogs (K‐PBAs) are commonly used as K‐ion battery (KIB) cathodes. Interestingly, K‐PBAs are appealing cathodes for Na‐ion batteries (NIBs). In a hybrid NIB cell, where Na‐ion is in the electrolyte and K‐ion is in the PBA cathode, cation intercalation and electrochemical performance of the cathode can be significantly affected by [Fe(CN)6]4− anion vacancy. This work studies the effect of anion vacancy in K‐PBAs on regulating K‐ion/Na‐ion intercalation mechanism in hybrid NIB cells, by comparing two K‐PBA cathodes with different vacancy contents. The results demonstrate that introducing a level of anion vacancy can maximize the number of K‐ion intercalation sites and enhance K‐ion diffusion in the PBA framework. This facilitates K‐ion intercalation and suppresses Na‐ion intercalation, resulting in a K‐ion‐dominated and high‐discharge‐voltage ion storage process in the hybrid NIB cell. The K‐PBA cathode with 20% anion vacancy delivers 128 mAh g−1 at 25 mA g−1 and 67 mAh g−1 at 1000 mA g−1, as well as retains 89% and 81% capacity after 100 and 300 cycles, respectively. It completely outperforms the counterpart with 7% anion vacancy, which exhibits increased Na‐ion intercalation but overall deteriorated ion storage.

Inhibiting the dissolution of the intermediate with conductive polymer coating layer to improve the stability of CuTCNQ cathode for K-ion batteries

The seriously dissolution of the intermediate into the organic electrolyte has been the key limitation for metal-organic compounds in K-ion batteries. Here, we initially inhibit the dissolution of intermediate products (TCNQ0) with a highly conducting polymer (polypyrrole, PPy) coated on the CuTCNQ. And the adsorption energy between the conductive polymer PPy and the intermediate product TCNQ can be significantly enhanced (−0.55 eV) as compared to the TCNQ molecules (0.21 eV), which can restrain the free intermediate product dissolved in the organic electrolyte, resulting in an enhanced cyclic stability as well as rate performance. Additionally, the highly conductive PPy exhibits flexible structure, which can weaken the interface effect between the electrode and the coating layer. This work provides further understanding on surface coating on metal-organic compounds and has significant basic scientific sense for the in-depth research of K-ion batteries.

Evaluation of P3-Type Layered Oxides as K-Ion Battery Cathodes.

Given the increasing energy storage demands and limited natural resources of Li, K-ion batteries (KIBs) could be promising next-generation systems having natural abundance, similar chemistry, and energy density. Here, we have investigated the P3-type K0.5TMO2 (where TM = Ti, V, Cr, Mn, Co, or Ni) systems using density functional theory calculations as potential positive intercalation electrodes (or cathodes) for KIBs. Specifically, we have identified ground-state configurations and calculated the average topotactic voltages, electronic structures, on-site magnetic moments, and thermodynamic stabilities of all P3-K0.5TMO2 compositions and their corresponding depotassiated P3-TMO2 frameworks. Additionally, we evaluated the dynamic stability and K-mobility in select P3 structures. We find that K adopts the honeycomb or zig-zag configuration within each K-layer of all P3 structures considered, irrespective of the transition-metal (TM). In terms of voltages, we find the Co- and Ti-based compositions to exhibit the highest (4.59 V vs. K) and lowest (2.24 V) voltages, respectively, with the TM contributing to the redox behavior upon K (de-)intercalation. We observe all P3-K0.5TMO2 to be (meta)stable and hence experimentally synthesizable according to our 0 K convex hull calculations, while all depotassiated P3-TMO2 configurations are unstable and may appear during electrochemical cycling. Also, we verified the stability of the prismatic coordination environment of K compared to octahedral coordination at the K0.5TMO2 compositions using Rouxel and cationic potential models. Finally, combining our voltage and stability calculations, we find P3-KxCoO2 to be the most promising cathode composition, while P3-KxNiO2 is worth exploring. We also find P3-KxMnO2 to be worth pursuing given its dynamic stability and facile migration of K+ at both potassiated and depotassiated compositions. Our work should contribute to the exploration of strategies and materials required to make practical KIBs.

An organic cathode in non-flammable phosphate electrolyte for K-ion batteries

A non-flammable potassium-ion battery is constructed by using an advanced n-type organic cathode called 2PTCDA@C and K-metal anode in triethyl phosphate electrolyte, which can show the peak discharge capacity of 125 mAh g−1cathode in 1.5–3.5 V and stably run for 100 cycles.

Characterising the Ionic Transport and Thermodynamic Properties of Potassium-Ion Electrolytes

The lithium price has increased more than sevenfold since the start of 2021 (as of May 2022), reaching unprecedented price levels and demonstrating significant challenges for the security of supply of lithium for lithium-ion batteries (LIBs)1. With forecasts showing a potential significant lithium supply deficit by 20301, the case for alternative chemistries based on abundant minerals which can fulfil some LIB functions has never been stronger. Sodium-ion batteries (NIBs) and potassium-ion batteries (KIBs) are emerging as promising complementary technologies to lithium-ion batteries (LIBs) due to the availability and low cost of sodium and potassium, and the minerals comprising their leading electrodes2 , 3. KIBs have a significant advantage over NIBs as K+ can reversibly intercalate into the graphite electrodes used in LIBs, thus one of the primary components of KIBs is already available at commercial scale, unlike for NIBs2. The lower charge density of K+ compared to Li+ has also been suggested to result in superior ion transport in the electrolyte with KIBs potentially able to deliver superior rate capability and low-temperature performance. However, a comprehensive characterisation of the ionic transport and thermodynamic properties of nonaqueous K-ion electrolytes, critical to the development of KIBs, has not yet been reported. Here, for the first time, we fully characterise the ionic transport and thermodynamic properties of a nonaqueous K-ion electrolyte4, potassium bis(fluorosulfonyl)imide (KFSI) in 1,2-dimethoxyethane (DME) and compare it with its Li-ion equivalent (LiFSI in DME) over the concentration range 0.25–2 m. This was realised by developing a K metal preparation protocol enabling sufficient K metal stability for electrolyte characterisation. Our results demonstrate that the K-ion electrolyte indeed displays significantly higher salt diffusion coefficients and transference numbers than the Li-ion electrolyte, evidencing the potential for high-power applications of KIBs. IEA. Global EV Outlook 2022. (IEA, 2022).Dhir, S., Wheeler, S., Capone, I. & Pasta, M. Outlook on K-Ion Batteries. Chem vol. 6 2442–2460 (2020). doi: 10.1016/j.chempr.2020.08.012Hosaka, T., Kubota, K., Hameed, A. S. & Komaba, S. Research Development on K-Ion Batteries. Chem. Rev. acs.chemrev.9b00463 (2020) doi:10.1021/acs.chemrev.9b00463.Dhir, S., Jagger, B., Maguire, A. & Pasta, M. Characterising the Ionic Transport and Thermodynamic Properties of Potassium-ion Electrolytes. Res. Sq. (2022) doi:10.21203/RS.3.RS-2310020/V1. Figure 1

Enhancing the Electrochemical Properties of the Layered-Type K0.4V2O5 Cathode Materials through Cationic Metal Substitution in K Sites

Layered-type K0.4V2O5 have been widely investigated as cathode materials for potassium-ion batteries (PIBs) due to their high specific capacity. [1,2] However, sluggish intercalation kinetics of K ions into their crystal structure generally result in drastic capacity fading and poor power capability. [3] Here, we present significantly enhanced K-ion storage performances of the layered-type K0.4V2O5 cathode enabled by substitution of cationic metal for K-site. Density functional theory calculations data indicates that cationic metal prefer to occupy the K-site than transition metal layer. During charge and discharge process, inactive cationic metal acts as a pillar, thereby suppressing the irreversible phase transition and structural deterioration. In addition, cationic metal creates vacancies at k site, improving K-ion diffusion kinetics. Compared to K0.4V2O5, the modified cathode demonstrated the better cycling stability and power capability. A insitu X-ray diffraction and X-ray absorption near edge structure was used to verify role of cationic metal in improving electrochemical performance of the K0.4V2O5 cathode. Deng, X. Niu, G. Ma, Z. Yang, L. Zeng, Y. Zhu, L. Guo. Layered Potassium Vanadate K0.5V2O5 as a Cathode Material for Nonaqueous Potassium Ion Batteries, Adv. Func. Mater. 28 (2018) 1800670.Yang, Z. Liu, L. Deng, L. Tan, X. Niu, M. M. S. Sanad, L. Zeng, Y. Zhu. A Non-Topotactic Redox Reaction enabled K2V3O8 as a High Voltage Cathode Material for Potassium-Ion Batteries, Chem. Commun. 55 (2019) 14988–14991.Q. Fu, A. Sarapulove, L. Zhu, G. Melinte, A. Missyul, E. Welter, X. Luo, M. Knapp, H. Ehrenberg, S. Dsoke. In Operando Study of Orthorhombic V2O5 as Positive Electrode Materials for K-Ion Batteries, J. Energy Chem. 62 (2021) 627–636.

High S-doped amorphous carbon/carbon quantum dots coupled micro-frame for highly efficient potassium storage

Anode materials with excellent rate capability, capacity, and cycle life have been a challenge in obtaining cost-effective K-ion batteries (KIBs). Based on the concept of waste recycling, we prepared the S-doped (21.5%) amorphous carbon/carbon quantum dots coupled micro-frame (SCMF) by combining chemical exfoliation and S/Se-assisted carbonization. SCMF exhibited the advantages of integrating amorphous carbon and carbon quantum dots (CQDs). The CQDs serve as fast electron channels, while amorphous carbon can accommodate more large-size K-ions and mitigate volume expansion. In KIBs, SCMF maintained a high reversible capacity (414.0 mAh g−1, after 100 cycles at 100 mA g−1), a good rate capability (224.0 mAh g−1, 2000 mA g−1), and excellent capacity retention (208.9 mAh g−1, after 2000 cycles at 1000 mA g−1). The molecular dynamic simulation revealed that CQDs provided fast electron transport channels and that C, O and S atoms had suitable interactions with K, facilitating potassium storage. Moreover, the potassium-ion capacitor (PIC) assembled from SCMF and activated carbon exhibited stable electrochemical performance, proving its potential for application. The research provided valuable insights into the reuse of biomass waste in new secondary batteries.

Graphene-like AlP3 monolayer: A high-performance anode material for Li/Na/K-ion batteries

The rational design of anode materials with high capacity, good stability, and fast diffusion rate are crucial demands for rechargeable alkali metal ion batteries (AMIBs). Herein, the density functional theory calculations have been carried out to investigate the feasibility of an AlP3 monolayer with folded graphene-like structure as an anode material for AMIBs. The results indicated that the alkali metal atoms (AM = Li, Na, and K) can be stably adsorbed on the AlP3 monolayer surface and further enhance the conductivity of the system. The average open-circuit voltages are only 0.70 V, 0.28 V, and 0.37 V for Li, Na, and K storages, respectively. The diffusion energy barriers of Li, Na, and K atoms are 0.56 eV, 0.41 eV, and 0.20 eV, respectively. Furthermore, the AlP3 monolayer possesses a high theoretical specific capacity of 447 mAh g−1, 894 mAh g−1, and 1565 mAh g−1 for Li, Na, and K-ion batteries, respectively. Overall, the AlP3 monolayer is an excellent anode material for AMIBs, especially for K-ion batteries.