Cathode Material For Potassium-ion Batteries Research Articles

Orthorhombic K3V3(PO4)4: A low-temperature cathode material for potassium-ion batteries

Potassium-ion battery has been considered as a promising energy storage device with low cost and high sustainability. However, its low-temperature performance is always poor due to the large size of K+ ions and poor ion transportation capability under low temperature. In this work, a carbon-coated orthorhombic K3V3(PO4)4/C cathode material for potassium-ion batteries is developed with promising low-temperature cycle performance. At −10 °C, K3V3(PO4)4/C retains a reversible capacity of 52.2 mAh/g for 1400 cycles at a current density of 100 mA g−1. The superior low-temperature performance is attributed to its open framework structure, which provides three-dimension channels for K-ion transportation. It is revealed that V3+/V4+ redox dominates the charge compensation in K3V3(PO4)4/C during charge and discharge processes. Carbon coating can not only reduce the charge transfer resistance of the electrode and prevent electrode cracking, but also helps to the formation of CF3-rich interfaces between the cathode and electrolyte, ensuring high interfacial stability of K3V3(PO4)4/C during cycling.

Co/Al Co-Substituted Layered Manganese-Based Oxide Cathode for Stable and High-Rate Potassium-Ion Batteries.

Manganese-based layered oxides are promising cathode materials for potassium-ion batteries (PIBs) due to their low cost and high theoretical energy density. However, the Jahn-Teller effect of Mn3+ and sluggish diffusion kinetics lead to rapid electrode deterioration and a poor rate performance, greatly limiting their practical application. Here, we report a Co/Al co-substitution strategy to construct a P3-type K0.45Mn0.7Co0.2Al0.1O2 cathode material, where Co3+ and Al3+ ions occupy Mn3+ sites. This effectively suppresses the Jahn-Teller distortion and alleviates the severe phase transition during K+ intercalation/de-intercalation processes. In addition, the Co element contributes to K+ diffusion, while Al stabilizes the layer structure through strong Al-O bonds. As a result, the K0.45Mn0.7Co0.2Al0.1O2 cathode exhibits high capacities of 111 mAh g-1 and 81 mAh g-1 at 0.05 A g-1 and 1 A g-1, respectively. It also demonstrates a capacity retention of 71.6% after 500 cycles at 1 A g-1. Compared to the pristine K0.45MnO2, the K0.45Mn0.7Co0.2Al0.1O2 significantly alleviates severe phase transition, providing a more stable and effective pathway for K+ transport, as investigated by in situ X-ray diffraction. The synergistic effect of Co/Al co-substitution significantly enhances the structural stability and electrochemical performance, contributing to the development of new Mn-based cathode materials for PIBs.

Review on Layered Manganese-Based Metal Oxides Cathode Materials for Potassium-Ion Batteries: From Preparation to Modification.

Potassium-ion battery is rich in resources and cheap in price, in the era of lithium-ion battery commercialization, potassium-ion battery is the most likely to replace it. Based on the classification and summary of electrode materials for potassium-ion batteries, this paper focuses on the introduction of manganese-based oxide KxMnO2. The layered KxMnO2 has a large layer spacing and can be embedded with large size potassium-ions. This paper focuses on the preparation and doping of manganese-based cathode materials for potassium-ion batteries, summarizes the main challenges of KxMnO2-based cathode materials in the current stage of research and further looks into its future development direction.

Strain-modulated Mn-rich layered oxide enables highly stable potassium-ion batteries

Mn-rich layered oxides show great promise as cathode materials for potassium-ion batteries due to their high capacity and cost-effectiveness. However, internal structural strain and irreversible phase transitions caused by Jahn-Teller distortion affect their cycling stability. Here, we present an efficient strategy to concurrently modulate the internal strain and suppress the irreversible phase transition in Mn-rich cathodes by incorporating amounts of zinc (Zn) ions into the transition metal layers. The substituted Zn serves to regulate local chemistry, thereby mitigating octahedral distortion in Mn-O bonds, relieving the strain between layers, and reducing the occurrence of P3-O3 phase transition under high voltages. These findings are supported by EXAFS, in situ X-ray diffraction, advanced transmission electron microscopy, electron tomography, and DFT simulations. The low-strain K0.5Mn0.8Co0.1Zn0.1O2 electrode exhibits a high reversible capacity retention about ∼90 % (105 mAh g−1 at 100 mA g−1), exceptional rate performance in the voltage of 1.5 ∼ 3.9 V, and a substantial capacity retention after 500 cycles. This strain-relieved approach broadens the scope of lattice engineering by addressing internal strain concerns and mitigating the strain associated with potassium (de)intercalation, thereby having potential to advance the development of stable cathodes for PIBs.

Defect-Free Prussian Blue Analogue as Zero-Strain Cathode Material for High-Energy-Density Potassium-Ion Batteries.

Prussian blue analogues (PBAs) have been widely studied as cathodes for potassium-ion batteries (PIBs) due to their three-dimensional framework structure and easily adjustable composition. However, the phase transition behavior and [Fe(CN)6]4- anionic defects severely deteriorate electrochemical performances. Herein, we propose a defect-free potassium iron manganese hexacyanoferrate (K1.47Fe0.5Mn0.5[Fe(CN)6]·1.26H2O, KFMHCF-1/2) as the cathode material for PIBs. The Fe-Mn binary synergistic and defect-free effects can inhibit the cell volume change and octahedral slip during the K-ion insertion/extraction process, so that the phase transformation behavior (monoclinic ↔ cubic) is effectively inhibited, achieving a zero-strain solid solution mechanism employing Fe and Mn as dual active-sites. Thus, KFMHCF-1/2 contributes the highest initial capacity of 155.3 mAh·g-1 with an energy density of 599.5 Wh·kg-1 at 10 mA·g-1 among the reported PBA cathodes, superior rate capability, and cyclic stability over 450 cycles. The assembled K-ion full battery using K deposited on graphite (K@G) as anode also delivers high reversible specific capacity of 131.1 mAh·g-1 at 20 mA·g-1 and ultralong lifespans over 1000 cycles at 50 mA·g-1 with the lowest capacity decay rate of 0.044% per cycle. This work will promote the rapid application of high-energy-density PIBs.

Advancements in cathode materials for potassium-ion batteries: current landscape, obstacles, and prospects

This perspective highlights progress in the development of cathode materials for potassium-ion batteries, whilst providing valuable insights into unexplored compositional spaces that can be pursued for high-performance electrode materials.

钾离子电池锰基正极材料研究进展

钾离子电池锰基正极材料研究进展

Layer-Structured Multitransition-Metal Oxide Cathode Materials for Potassium-Ion Batteries with Long Cycling Lifespan and Superior Rate Capability.

Manganese (Mn)-based layer-structured transition metal oxides are considered as excellent cathode materials for potassium ion batteries (KIBs) owing to their low theoretical cost and high voltage plateau. The energy density and cycling lifetime, however, cannot simultaneously satisfy the basic requirements of the market for energy storage systems. One of the primary causes results from the complex structural transformation and transition metal migration during the ion intercalation and deintercalation process. The orbital and electronic structure of the octahedral center metal element plays an important role for maintaining the octahedral structural integrity and improving the K+ diffusivity by the introduced heterogeneous [Me-O] chemical bonding. A multitransition metal oxide, P3-type K0.5Mn0.85Co0.05Fe0.05Al0.05O2 (KMCFAO), was synthesized and employed as a cathode material for KIBs. Beneficial from the larger layer spacing for K+ to better accommodate and effectively preventing the irreversible structural transformation in the insertion/extraction process, it can reach a superior capacity retention up to 96.8% after 300 cycles at a current density of 500 mA g-1. The full cell of KMCFAO//hard carbon exhibits an encouraging promising energy density of 113.8 W h kg-1 at 100 mA g-1 and a capacity retention of 72.6% for 500 cycles.

Component design and regulation to stabilize P3-type Mn-based layered cathodes for potassium-ion batteries

Mn-based layered oxides with high theoretical capacity are one of the most promising cathode materials for potassium-ion batteries. However, the Jahn-teller distortion of Mn3+ in Mn-based layered cathodes always brings about harmful disordered structure and irreversible phase transition, resulting in severe degradation of electrochemical performance. Herein, we synthesized P3–K0.5Mn0.6Ni0.2M0.2O2 (M = Fe, Co, FeCo) and systematically investigate the effect of component regulation on the layered structure and electrochemical properties. The P3–K0.5Mn0.6Ni0.2Co0.2O2 exhibits a discharge capacity of 73.77 mAh g−1, demonstrating an excellent capacity retention rate of 70.17 % after 120 cycles at 50 mA g−1. In-depth analysis reveals that P3–K0.5Mn0.6Ni0.2Co0.2O2 possesses a larger K+ layer spacing, making the insertion/extraction of potassium ions become much easier. Furthermore, the introduction of Co into the transition metal layer enhances the content of Mn4+, thereby inhibiting Jahn-Teller distortion and improving structural stability. Especially, the P3–K0.5Mn0.6Ni0.2Co0.2O2 shows a highly reversible single-phase solid solution reaction during the initial cycle, which means the detrimental phase transition of P3–O3 caused by Jahn-Teller effect is effectively suppressed. This work contributes to a better understanding of the effect of component design and regulation on the performance of the layered oxides cathode and provide insight into the design of high-performance cathode materials for potassium-ion batteries.

Promoting reversibility of layered potassium cathode through interstitial doping

With the increasing needs for large-scale and low-cost energy storage devices, Mn-based layered oxide cathodes have achieved considerable researching interests for potassium-ion batteries owing to their high energy density, abundant resource and low toxicity. However, their developments are challenged by the absence of suitable cathode materials to tolerate large-sized K-ion insertion/extraction and the presence of Jahn-Teller distortion of Mn3+. To address this issue, we present a strategy of embedding boron into interstitial tetrahedral sites to obtain a P3-K0.5Mn0.8Co0.2B0.1O2 cathode. Strong B-O covalent bonds facilitate the construction of robust orthorhombic framework and alleviate the undesired elongation of Mn-O bonds, contributing to excellent electrochemical performance. In addition, boron ions are verified to promote the formation of a homogeneous cathode electrolyte interphase layer, improving interfacial stability and realizing highly reversible cycling in a wide voltage range (1.4–4.3 V). This strategy provides a new pathway towards the development of high-performance cathode materials for potassium-ion batteries.

KI-Assisted Formation of Spindle-like Prussian White Nanoparticles for High-Performance Potassium-Ion Battery Cathodes.

Prussian white (PW) is considered as a promising cathode material for potassium-ion batteries (KIBs) due to its low cost and high theoretical capacity. However, the high water content and structural defects and the strict synthesis conditions of PW lead to its unsatisfactory cycling performance and low specific capacity, hindering its practical applications. Herein, a template-engaged reduction method is proposed, using MIL-88B(Fe) as a self-template and KI as the reducing agent to prepare K-rich PW with low defects and water content. Furthermore, the hierarchical porous spindle-like morphology can be inherited from the precursor, furnishing sufficient active sites and reducing the ion diffusion path. Consequently, when applied as a KIB cathode material, spindle-like PW (K1.72Fe[Fe(CN)6]0.96·0.342H2O) manifested remarkable potassium storage properties. Notably, a full cell assembled by the spindle-like PW cathode and graphite anode exhibited a large energy density of ∼216.7 Wh kg-1, demonstrating its huge potential for energy storage systems.

Tetrahedral Occupied V Ions Enabling Reversible Three-Electron Redox of Cr3+ /Cr6+ in Layered Cathode Materials for Potassium-Ion Batteries.

Reversible three-electron redox of Cr3+ /Cr6+ in layered cathode materials for rechargeable batteries is very attractive in layered cathode materials, which leads to high capacity and energy density for rechargeable batteries. However, the poor reversibility and Cr-ion migration make it very challenging. In this work, by introducing V ions into tetrahedral sites of layer-structured NaCrO2 , reversible three-electron redox of Cr3+ /Cr6+ is realized successfully in NaCr0.92 V0.05 O2 (NCV05) cathode for potassium-ion batteries with a cut-off voltage of 4.0V. V ions can weaken the attraction of Cr to electrons, leading to enhanced valence change of Cr ions. On the other hand, V in tetrahedral sites can facilitate the reversible migration of Cr between octahedral and tetrahedral sites via coulombic repulsion to realize the reversible redox between Cr3+ and Cr6+ during charge and discharge processes. In addition, V ions can inhibit the phase transition from O3 phase to O'3 phase during the charge process by adjusting the crystal lattices. As a result, the NaCr0.92 V0.05 O2 cathode exhibits a high reversible capacity of 130mAhg-1 with promising cycle stability and rate capability. The strategy opens new opportunity for developing high-capacity cathode materials for potassium-ion batteries.

MnFe Prussian blue analogue-derived P3-K0.5Mn0.67Fe0.33O1.95N0.05 cathode material for high-performance potassium-ion batteries

Potassium-ion batteries (PIBs), with their high theoretical energy density and abundant natural resources, are emerging as one of the most promising candidates for next-generation energy storage systems. Nevertheless, they suffer from large volume expansion and sluggish K+ transport due to the huge ionic radius of K+, resulting in limited cyclic life and rate performance. Therefore, accelerated transport kinetics may be the key to designing electrodes with excellent potassium storage properties. Herein, we develop a new synthetic method to in-situ construct a high-efficiency PIB cathode, N-doped P3-typed K0.5Mn0.67Fe0.33O1.95N0.05 nanosheets (denoted KMFON), using the low cost Prussian blue analogue Mn2[Fe(CN)6] as a precursor. Combining experimental results and theoretical calculations, the as-synthesized KMFON exhibits large interlayer spacing, small K+ migration energy barrier, high electronic conductivity, and fast K+ transport kinetics, which are attributed to the larger-sized N substitution O. It also manifests an initial reversible capacity of 104.2 mAh g−1 at 20 mA g−1, a rate capability of 41.5 mAh g−1 at 500 mA g−1, and a high discharge capacity of 52.2 mAh g−1 after 300 cycles at 100 mA g−1. Moreover, the KMFON//pitch-derived soft carbon full cell exhibits a satisfactory rate performance of 49.4 mAh g−1 at 200 mA g−1 and a good cycling performance of 46.8 mAh g−1 after 200 cycles at 100 mA g−1, indicating the great potential of KMFON as a cathode material for PIBs.

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.

Zinc-Doping Strategy on P2-Type Mn-Based Layered Oxide Cathode for High-Performance Potassium-ion Batteries.

Mn-based layered oxide is extensively investigated as a promising cathode material for potassium-ion batteries due to its high theoretical capacity and natural abundance of manganese. However, the Jahn-Teller distortion caused by high-spin Mn3+ (t2g 3 eg 1 ) destabilizes the host structure and reduces the cycling stability. Here, K0.02 Na0.55 Mn0.70 Ni0.25 Zn0.05 O2 (denoted as KNMNO-Z) isreported to inhibit the Jahn-Teller effect and reduce the irreversible phase transition. Through the implementation of a Zn-doping strategy, higher Mn valence isachieved in the KNMNO-Z electrode, resulting in a reduction of Mn3+ amount and subsequently leading to an improvement in cyclic stability. Specifically, after 1000 cycles, a high retention rate of 97% isobserved. Density functional theory calculations reveals that low-valence Zn2+ ions substituting the transition metal position of Mn regulated the electronic structure around the MnO bonding, thereby alleviating the anisotropic coupling between oxidized O2- and Mn4+ and improving the structural stability. K0.02 Na0.55 Mn0.70 Ni0.25 Zn0.05 O2 provided an initial discharge capacity of 57 mAh g-1 at 100mA g-1 and a decay rate of only 0.003% per cycle, indicating that the Zn-doped strategy is effective for developing high-performance Mn-based layered oxide cathode materials in PIBs.

Multi-element doping induced transition metal disordered layered oxide for rapid and stable potassium storage

Layered transition metal oxides are highly desirable cathode materials for potassium-ion batteries (PIBs) because of their considerable theoretical capacity and high output voltage. However, the ordered structure of these oxides limits K+ transport kinetics and the stability of the layered structure, resulting in poor rate and cycling performance. Here, a novel disordered Mn-based quinary transition metal oxide cathode, K0.7Fe0.05Co0.1Mn0.75Ni0.05V0.05O2, was developed for use in high-performance PIBs. The designed K0.7Fe0.05Co0.1Mn0.75Ni0.05V0.05O2 is a completely disordered transition metal that exhibits excellent rate capability (77.39 mA h g−1 at 1000 mA g−1) and long cycle life (∼70.3% capacity retention at 1000 mA g−1 after 500 cycles). The kinetics of the facilitated electrode process was demonstrated by density functional theory calculations, where the disordering of transition metals effectively reduces the energy barrier of K+ migration while increasing the electronic conductivity. In situ X-ray diffraction verifies the highly reversible structural evolution during potassium insertion/extraction, achieving an ultra-low volume change (0.65%). The enhanced performance is attributed to a larger d-spacing and stronger metal–oxygen bond. Such results substantiate that multi-element doping to induce quinary disordered transition metals is an efficient strategy to enhance the electrochemical performance of layered oxides and provide a new guideline for the design of advanced PIBs.

Dual-salt assisted synergistic synthesis of Prussian white cathode towards high-capacity and long cycle potassium ion battery

Prussian blue analogues (PBAs) are considered as superior cathode materials for potassium-ion batteries (PIBs) because of their three-dimensional open framework structure, high stability, and low cost. However, the intrinsic lattice defects and low potassium content typically results in poor rate and cycling performance, thus limited their practical applications. In this work, high-quality K1.64FeFe(CN)6 (PW-HQ) material with less crystalline water (6.21%) and high potassium content (1.64 mol−1) was successfully synthesized by a novel coprecipitation method with potassium citrate (K-CA) and potassium chloride (KCl) addition. Specifically, the electrode delivers a reversible capacity of 113.1 mA h g−1 at the current rate of 50 mA g−1 with ∼100% coulombic efficiency. Besides, the electrode retained 90% reversible capacity at 500 mA g−1 current density after 1000 cycles, indicating only 0.01% capacity decay per cycle. Moreover, we have revealed that the introduction of K-CA controlled the chelating rate of Fe(II) and the addition of KCl increased the K+ content, hence improving the capacity and stability of the as-prepared electrodes. Structural evolution and potassium storage mechanism were further investigated by detailed ex-situ X-ray diffraction and in-situ Raman measurements, which demonstrated reversible potassiation/depotassiation behavior and negligible volume change during the electrochemical process. In general, this work provides an efficient strategy to eliminate water contents in Prussian blue cathode and improve its electrochemical performance, which plays a key role in promoting the industrialization of potassium ion batteries.

Highly Crystalline Prussian Blue for Kinetics Enhanced Potassium Storage.

Prussian blue analogs (PBAs) are promising cathode materials for potassium-ion batteries (KIBs) owing to their large open framework structure. As the K+ migration rate and storage sites rely highly on the periodic lattice arrangement, it is rather important to guarantee the high crystallinity of PBAs. Herein, highly crystalline K2 Fe[Fe(CN)6 ] (KFeHCF-E) is synthesized by coprecipitation, adopting the ethylenediaminetetraacetic acid dipotassium salt as a chelating agent. As a result, an excellent rate capability and ultra-long lifespan (5000 cycles at 100mA g-1 with 61.3% capacity maintenance) are achieved when tested in KIBs. The highest K+ migration rate of 10-9 cm2 s-1 in the bulk phase is determined by the galvanostatic intermittent titration technique. Remarkably, the robust lattice structure and reversible solid-phase K+ storage mechanism of KFeHCF-E are proved by in situ XRD. This work offers a simple crystallinity optimization method for developing high-performance PBAs cathode materials in advanced KIBs.

Pillar strategy enhanced ion transport and structural stability toward ultra-stable KVPO4F cathode for practical potassium-ion batteries

KVPO4F (KVPF) is a promising cathode material for potassium-ion batteries (PIBs) because of its high operating voltage, high energy density, and excellent thermal stability. Nevertheless, the low kinetics and large volume change have been the major hurdles causing irreversible structural damage, high inner resistance, and poor cycle stability. Herein, a pillar strategy of Cs+ doping in KVPO4F is introduced to reduce the energy barrier for ion diffusion and volume change during potassiation/depotassiation, which significantly enhances the K+ diffusion coefficient and stabilizes the crystal structure of the material. Consequently, the K0.95Cs0.05VPO4F (Cs-5-KVPF) cathode exhibits an excellent discharge capacity of 104.5 mAh g−1 at 20 mA g−1 and a capacity retention rate of 87.9% after 800 cycles at 500 mA g−1. Importantly, Cs-5-KVPF//graphite full cells attain an energy density of 220 Wh kg−1 (based on the cathode and anode weight) with a high operating voltage of 3.93 V and 79.1% capacity retention after 2000 cycles at 300 mA g−1. The Cs-doped KVPO4F cathode successfully innovates the ultra-durable and high-performance cathode materials for PIBs, demonstrating its considerable potential for practical applications.

Uniform P2-K0.6CoO2 Microcubes as a High-Energy Cathode Material for Potassium-Ion Batteries

Layered transition-metal (TM) oxides have drawn ever-growing interest as positive electrode materials in potassium-ion batteries (PIBs). Nevertheless, the practical implementation of these positive electrode materials is seriously hampered by their inferior cyclic property and rate performance. Reported here is a self-templating strategy to prepare homogeneous P2-K0.6CoO2 (KCO) microcubes. Benefiting from the unusual microcube architecture, the interface between the electrolyte and the active material is considerably diminished. As a result, the KCO microcubes manifest boosted electrochemical properties for potassium storage including large reversible capacity (87.2 mAh g-1 under 20 mA g-1), superior rate performance, and ultralong cyclic steady (an improved capacity retention of 86.9% under 40 mA g-1 after 1000 cycles). More importantly, the fabrication approach can be effectively extended to prepare other layered TM oxide (P3-K0.5MnO2, P3-K0.5Mn0.8Fe0.2O2, P2-K0.6Co0.67Mn0.33O2, and P2-K0.6Co0.66Mn0.17Ni0.17O2) microcubes and nonlayered TM oxide (KFeO2) microcubes.