Voltage Window Research Articles

Synthesis and Properties of the LiMn2O4 Cathode Material for Lithium-ion Batteries

Spinel LiMn2O4 was synthesized by high-temperature solid-state method with lithium salt and manganese salt as raw materials, which were mixing with anhydrous ethanol as solvent under stirring, and calcining at high temperature in in the oxygen atmosphere. X-ray diffraction (XRD) and scanning electron microscope (SEM) showed that the size of lithium manganese particles with spinel structure was 80 to 200 nm, and the particle size distribution was uniform. The results showed that the prepared LiMn2O4 sample sintered at 700°C exhibited superior electrochemical performance when used as a cathode material for lithium-ion batteries with a voltage window of 2.5–4.8 V. The first charge-discharge specific capacity and first discharge capacity can reach 158.0 mAh‧g-1 and 138.4 mAh‧g-1, respectively, at 0.1 A‧g-1 current density, and the first Coulomb retention efficiency is 87.6%. The discharge specific capacity of the LiMn2O4 material can be maintained at 114 mAh‧g-1 when the test current density was returned to 0.1 A‧g-1 after 60 cycles.

An Ultrathin Solid Electrolyte for High‐Energy Lithium Metal Batteries

AbstractSolid‐state electrolytes (SSEs) are key to unlocking the potential of lithium metal batteries (LMBs), but their high thickness (>100 µm) due to poor mechanical properties limits energy density improvements. Herein, an ultrathin (≈5 µm) polymer SSE with a high Young's modulus (10.6 GPa), made from a polyvinylidene fluoride‐hexafluoropropylene (PVDF‐HFP) matrix and an ethylene diamine tetraacetic acid (EDTA) additive is proposed. By virtue of the electron‐donating property, EDTA induces the conformation transformation of PVDF‐HFP, enhancing the mechanical strength by a fine‐grain strengthening mechanism. In addition, PVDF‐HFP with cis‐conformation shortens the pathway for Li+, promotes the Li+ dissociation and immobilizes the anions of lithium salt, thus increasing the ionic conductivity (2.47 × 10−4 S cm−1) and transfer number (0.59) of the electrolyte. Moreover, the electrolyte also possesses a wide voltage window (4.7 V) and good heat/flame resistance. The half cells and full cells with the electrolytes show good cycling and rate performance. Notably, a pouch cell based on the electrolyte exhibits impressive energy densities of 516 Wh kg−1 and 1520 Wh L−1 (excluding packages), showing great potential for practical use in LMBs.

Suitability of late-life lithium-ion cells for battery energy storage systems

The globally installed capacity of battery energy storage systems (BESSs) has increased steadily in recent years. Lithium-ion cells have become the predominant technology for BESSs due to their decreasing cost, increasing cycle life, and high efficiency. However, the cells are subject to degradation due to a multitude of cell internal aging mechanisms, which result in reduced capacity, efficiency, and usable nominal power range over a BESS life cycle. Towards their end-of-life, the cells often show a steep increase in their degradation rate, called nonlinear aging. This work investigates how these ”late-life” lithium-ion cells perform in typical BESS applications. We show how decreased capacity, efficiency, and nominal power range impact the profitability of a home storage system for self-consumption increase (SCI) and a large-scale storage system for energy arbitrage (EA). A physicochemical aging model, which accounts for lithium-plating-induced nonlinear aging, is developed and parameterized based on an experimental cell aging study. The aging study and model show that cells that have entered the nonlinear aging phase can transition back to a significantly reduced degradation rate through adapted operating conditions, namely a reduced charging rate and operating voltage window. The case study highlights that the battery cells enter the nonlinear aging phase significantly earlier when used for the EA application compared to the SCI application. However, by adapting the operating conditions below 80% state of health, the obtainable net present value over the investigated ten-year timeframe in the EA application increases by 39.8%, and the lifetime is significantly prolonged.

Fabrication of nickel foam/MXene/CoAl-layered double hydroxide by electrodeposition as electrode material for high-performance asymmetric supercapacitor

Layered double hydroxides (LDH) have become one of the highly promising electrode materials due to large specific area, excellent cycling stability and high energy density. However, the large internal resistance limits their applications in energy storage. The introduction of highly conductive materials is expected to solve this problem. In here, nickel foam (NF)/MXene/CoAl-LDH is prepared by electrodepositing CoAl-LDH on the surface of MXene-coated NF, and the effects of Co:Al ratio on the electrochemical properties are investigated in detail. The best electrochemical performance of the composite is obtained when Co:Al=2:1, with a specific capacitance of 646.7 F g−1 at 0.5 A g−1 and 450.8 F g−1 at 5 A g−1. Furthermore, the asymmetric supercapacitor is assembled with NF/MXene/CoAl-LDH as the positive electrode and activated carbon (AC) as the negative electrode. The voltage window of the device can reach 1.6 V. The specific capacitance of the device is 126.87 F g−1 at a current density of 0.5 A g−1. At the power density of 400 W kg−1, the energy density of 45.11 Wh kg−1 is provided. Even at the high power density of 4000 W kg−1, the energy density can still reach 17.88 Wh kg−1. After 5000 cycles at a current density of 5 A g−1, it still maintains a capacity retention rate of 92.9%. The asymmetric device with its high specific capacitance, long term stability and good power density and energy density has a great potential in energy storage applications.

Pore-structure control of porous carbon electrode materials and energy-storage performance in water-in-salt electrolytes

The pore structure of carbon-based materials and the voltage window of the electrolyte are two key factors affecting the energy density of carbon-based supercapacitors (SCs). In this paper, activated carbon materials of different pore sizes is successfully synthesized by chemical activation method by adjusting the mass ratio of ZnCl2 to sucrose, and successfully applied to construct SCs based on different electrolyte systems. As the specific surface area of the prepared porous carbon materials shows a tendency to increase and then decrease, reaching a maximum in the presence of micropores. Further summarizing the constitutive relationship between pore structure-electrochemical performance in the high-concentration electrolyte system, it is found that the normalized specific capacity is larger at smaller pore sizes, and with the increase of mesoporous proportion, the normalized specific capacity decreases and tends to be stable. In addition, the different strengths of solvation of anions and cations in the electrolyte, with the cations contributing more to the contrast, and the presence of mesopores providing ion transport channels to improve the efficiency of ion transport in porous materials, which provide directions for designing a suitable pore structure for highly concentrated salt electrolytes, as well as another way of optimizing the properties of carbon-based materials for SCs.

A siloxane-based self-healing gel electrolyte with deep eutectic solvents for safe quasi-solid-state lithium metal batteries

Due to the safety problems caused by the use of flammable organic electrolytes in lithium batteries, it is urgent to develop new solid electrolytes with higher safety. Deep eutectic solvent (DES), as a very promising flame-retardant electrolyte system, has limited its application due to its liquid properties and poor compatibility with lithium metal. Herein, we report a DES-based self-healing polymer (DSHP) electrolyte for quasi-solid-state lithium metal batteries. The electrolyte was prepared by in-situ polymerization of bis (3-amino-propyl)-terminated polydimethylsiloxane (PDMS-NH2) and toluene 2,4-diisocyanate (TDI) monomers in a DES-based electrolyte with fluoroethylene carbonate (FEC) as an additive. The polymer network effectively improves the compatibility of DES with lithium metal and maintains a high ionic conductivity (0.60 mS cm−1 at 30 °C). At the same time, the well-designed siloxane-based DSHP electrolyte not only exhibits self-healing property, but also demonstrates non-flammability advantage with a wide electrochemical voltage window (4.5 V vs Li/Li+) and a high Li+ migration number (0.69). Therefore, the symmetric Li | DSHP | Li cell exhibits long-term cycle stability (>1400 h). The quasi-solid-state lithium battery with DSHP electrolyte coupled with lithium anode and LiFePO4 cathode demonstrates a high specific capacity of 151.6 mA h g−1. More importantly, the DSHP-based pouch cell exhibits excellent flexibility during the deformation process. This work provides a valuable method to design safe and high energy quasi-solid-state lithium batteries.

Accurate ion type and concentration detection using two bare electrodes by machine learning of non-faradaic electrochemical impedance measurements of an automated fluidic system

Detecting ion types and their concentrations in multi-ion aqueous solutions poses a complex challenge with significant implications for sensing applications. This paper introduces an automated fluidic system using two bare electrodes to measure electrochemical impedance spectroscopy (EIS) data and evaluates deep neural network (DNN) for ion type and concentration detection. Additionally, a data-augmentation model is proposed for non-faradaic voltage sweep EIS data, intended for neural network training. To validate the effectiveness of our approach, prepared solutions featuring varying concentrations of LiCl, NaCl, and KCl are experimented. Impedance (Z) vs DC bias voltage (V) data, i.e., ZV-EIS are measured from −400 mV to + 400 mV at 9 different frequencies up to ∼ 200 kHz, for 148 automatically prepared solutions, having total salt concentrations up to 200 mM. DNN models are trained with augmented samples and successfully identified individual ions in test set solutions and their concentrations with 4.51 mM average deviation. The study delves into the nuanced impacts of factors such as sampling voltage window, and measurement frequency on the performance of the machine learning models, 8 mV and 20 Hz giving the most significant results.

Fabrication of high voltage and energy dense supercapacitor with Manilkara zapota seeds derived porous activated carbon in acidic electrolyte

Achieving a high working potential window beyond the water electrolysis limit (>1.23 V) has always been a big challenge in the fabrication of aqueous supercapacitors (SCs). Since energy density has quadratic dependence on voltage, broadening of cell voltage can remarkably increase the energy density of the capacitor. Unfortunately, most of the aqueous electrochemical capacitors operated in strongly acidic or alkaline electrolytes show poor energy densities owing to their narrow operating voltage limit. To obtain a high voltage range of aqueous symmetric carbon/carbon capacitors and achieve high energy density, the chemistry of electrode materials and the electrochemical kinetics of electrolytes play a critical role. Hence, in the present work, we explore a porous activated carbon produced from the seeds of Manilkara zapota (ACMZ-700) in combination with sulfuric acid electrolyte to obtain an encouraging electrochemical stable working voltage window. Thus, the resulting symmetric SC effectively exhibited an enlarged cell voltage of 1.5 V in an acidic medium. Importantly, due to the positive role of oxygenated surface functional groups of the ACMZ-700 active material, the fabricated symmetric cell delivered an attractive specific capacitance of 334 F g−1 @ 1 A/g. As a result of high capacitance and broader working voltage, the symmetric device delivered an excellent energy density of 26 Wh kg−1 at a power density of 748 W kg−1 and held excellent cycling stability over 10,000 charge/discharge cycles.

A single-electrode evaluation method used for analyzing the working mechanism and capability of integrated membrane capacitive deionization

The evaluation of capacitive deionization (CDI) often relies on indicators like salt adsorption capacity and rate. However, these indicators encompass the entire system, including the anode and cathode. In practice scenarios, differences in specific capacitance, weight, and potential of zero charge result in varying theoretical ion adsorption capacity (IAC) and electrode potential. Hence, it is crucial to assess the deionization performance of individual electrodes. In this study, by introducing a reference electrode into the desalination device and enhancing the effective area and mass loading of the counter electrode, a single-electrode evaluation device was established to specifically analyze the deionization performance of the working electrode. Through this evaluation method, the single-electrode deionization performances of the anodic and cathodic integrated membrane electrodes (IMEs) were investigated, respectively, shedding light on the impact of IME on the Faradaic side reactions and co-ion effect. The results indicate that IME maintains an effective working voltage window and improves its stability. The cathodic IME effectively curbs the transport of dissolved oxygen, and the anodic IME prevents the carbon oxidation, thereby bolstering their IACs. This research not only elucidates the operational mechanism of IME but also highlights the feasibility of the single-electrode evaluation strategy in appraising asymmetric CDI.

MXene as Promising Anode Material for High-Performance Lithium-Ion Batteries: A Comprehensive Review.

Broad adoption has already been started of MXene materials in various energy storage technologies, such as super-capacitors and batteries, due to the increasing versatility of the preparation methods, as well as the ongoing discovery of new members. The essential requirements for an excellent anode material for lithium-ion batteries (LIBs) are high safety, minimal volume expansion during the lithiation/de-lithiation process, high cyclic stability, and high Li+ storage capability. However, most of the anode materials for LIBs, such as graphite, SnO2, Si, Al, and Li4Ti5O12, have at least one issue. Hence, creating novel anode materials continues to be difficult. To date, a few MXenes have been investigated experimentally as anodes of LIBs due to their distinct active voltage windows, large power capabilities, and longer cyclic life. The objective of this review paper is to provide an overview of the synthesis and characterization characteristics of the MXenes as anode materials of LIBs, including their discharge/charge capacity, rate performance, and cycle ability. In addition, a summary of the potential outlook for developments of these materials as anodes is provided.

Inkjet printed IGZO memristors with volatile and non-volatile switching

Solution-based memristors deposited by inkjet printing technique have a strong technological potential based on their scalability, low cost, environmentally friendlier processing by being an efficient technique with minimal material waste. Indium-gallium-zinc oxide (IGZO), an oxide semiconductor material, shows promising resistive switching properties. In this work, a printed Ag/IGZO/ITO memristor has been fabricated. The IGZO thickness influences both memory window and switching voltage of the devices. The devices show both volatile counter8wise (c8w) and non-volatile 8wise (8w) switching at low operating voltage. The 8w switching has a SET and RESET voltage lower than 2 V and − 5 V, respectively, a retention up to 105 s and a memory window up to 100, whereas the c8w switching shows volatile characteristics with a low threshold voltage (Vth < − 0.65 V) and a characteristic time (τ) of 0.75 ± 0.12 ms when a single pulse of − 0.65 V with width of 0.1 ms is applied. The characteristic time alters depending on the number of pulses. These volatile characteristics allowed them to be tested on different 4-bit pulse sequences, as an initial proof of concept for temporal signal processing applications.

A Novel Ternary Pseudocapacitive Electrode with Synergistic Contributions

AbstractTernary electrodes represent an exciting strategy to substantially enhance the performance of supercapacitors beyond what binary electrodes offer. However, the interplays among ternary constituents and their possible synergies remain poorly understood. This study investigates a ternary electrode design, wherein ferric oxyhydroxide (FeOOH) and magnesium dioxide (MnO2) are co‐deposited onto carbon nanotube (CNT) mats. The results reveal that the ternary electrode demonstrates a 33.3% reduction in internal resistance and a 59% increase in areal capacitance compared to its binary MnO2/CNT counterpart. Furthermore, the ternary electrode achieves a 25% increase in capacitance compared to the combined capacitances of separate MnO2/CNT and FeOOH/CNT electrodes. These findings demonstrate that combining FeOOH and MnO2 can synergistically enhance electrical conductivity and pseudocapacitance beyond their binary counterparts. This design yields a surface capacitance exceeding 3500 mF cm−2 at an active material loading up to 15 mg cm−2. By pairing with a binary FeOOH/CNT electrode, the resulting asymmetric supercapacitor exhibits an operational voltage window to 1.6 V. To demonstrate the potential of the new design, ternary electrodes are integrated into wearable and structural supercapacitors. The new synergistic ternary electrode approach provides a promising avenue for enhancing energy storage capacitance and expanding the scope of energy storage structure applications.

Lithium Superionic Conductive Nanofiber-Reinforcing High-Performance Polymer Electrolytes for Solid-State Batteries.

Although composite solid-state electrolytes (CSEs) are considered promising ionic conductors for high-energy lithium metal batteries, their unsatisfactory ionic conductivity, low mechanical strength, poor thermal stability, and narrow voltage window limit their practical applications. We have prepared a new lithium superionic conductor (Li-HA-F) with an ultralong nanofiber structure and ultrahigh room-temperature ionic conductivity (12.6 mS cm-1). When it is directly coupled with a typical poly(ethylene oxide)-based solid electrolyte, the Li-HA-F nanofibers endow the resulting CSE with high ionic conductivity (4.0 × 10-4 S cm-1 at 30 °C), large Li+ transference number (0.66), and wide voltage window (5.2 V). Detailed experiments and theoretical calculations reveal that Li-HA-F supplies continuous dual-conductive pathways and results in stable LiF-rich interfaces, leading to its excellent performance. Moreover, the Li-HA-F nanofiber-reinforced CSE exhibits good heat/flame resistance and flexibility, with a high breaking strength (9.66 MPa). As a result, the Li/Li half cells fabricated with the Li-HA-F CSE exhibit good stability over 2000 h with a high critical current density of 1.4 mA cm-2. Furthermore, the LiFePO4/Li-HA-F CSE/Li and LiNi0.8Co0.1Mn0.1O2/Li-HA-F CSE/Li solid-state batteries deliver high reversible capacities over a wide temperature range with a good cycling performance.

Confining Polymer Electrolyte in MOF for Safe and High‐Performance All‐Solid‐State Sodium Metal Batteries

AbstractNanoconfined polymer molecules exhibit profound transformations in their properties and behaviors. Here, we present the synthesis of a polymer‐in‐MOF single ion conducting solid polymer electrolyte, where polymer segments are partially confined within nanopores ZIF‐8 particles through Lewis acid‐base interactions for solid‐state sodium‐metal batteries (SSMBs). The unique nanoconfinement effectively weakens Na ion coordination with the anions, facilitating the Na ion dissociation from salt. Simultaneously, the well‐defined nanopores within ZIF‐8 particles provide oriented and ordered migration channels for Na migration. As a result, this pioneering design allows the solid polymer electrolyte to achieve a Na ion transference number of 0.87, Na ion conductivity of 4.01×10−4 S cm−1, and an extended electrochemical voltage window up to 4.89 V vs. Na/Na+. The assembled SSMBs (with Na3V2(PO4)3 as the cathode) exhibit dendrite‐free Na‐metal deposition, promising rate capability, and stable cycling performance with 96 % capacity retention over 300 cycles. This innovative polymer‐in‐MOF design offers a compelling strategy for advancing high‐performance and safe solid‐state metal battery technologies.

Rational Design of NiCo-borate/GO Heterojunction as a High-Performance Supercapacitor Electrode.

The bottleneck in the preparation of supercapacitors is how to develop high-energy and high-power-density devices by using appropriate materials. Herein, a novel NixCo3-x-B/GO heterostructure material was synthesized through a simple ultrasonic and precipitation method. The prepared NixCo3-x-B/GO heterostructure exhibits significant improvements in supercapacitor performance than NixCo3-x-B. The presence of GO effectively suppresses the excessive growth and accumulation of NixCo3-x-B; therefore, Ni2.7Co0.3-B/GO exhibits the best performance as an electrode material for supercapacitors: a high specific capacitance (Cm, 1789.72 F g-1@1 A g-1) and excellent rate performance. The asymmetric supercapacitor (ASC) device of Ni2.7Co0.3-B/GO//AC exhibits a Cm of 76.6 F g-1@1 A g-1, a large voltage window of 1.6 V, and a high energy density (ED) of 98.0 Wh kg-1. Furthermore, a flexible, all-solid-state supercapacitor assembled with Ni2.7Co0.3-B/GO as both the positive and negative electrodes demonstrates a Cm of 46.9 F g-1@1 A g-1. Even after multiple folding and bending at various angles, the device maintains excellent performance, showcasing remarkable stability. With a power density (PD) of 479.7 W kg-1, the device achieves a high ED of 60.0 Wh kg-1. This work provides valuable insights into the synergistic effects in electrochemical processes based on heterostructure materials.

Dual-function highly oxidative potassium salts empowering high-performance transition metal oxide/activated carbon for hybrid aqueous supercapacitors

In this work, a novel strategy of high-temperature oxidation-activation followed by rapid low-temperature aqueous-reflux treatment is developed to prepare transition metal oxide-activated carbon (TMO-AC) composites for supercapacitor applications. The super-absorbent polymer is selected as the carbon source, and the highly oxidative potassium salts K2FeO4/KMnO4 serve as both precursors for TMO and activators for AC. AC possesses a well-developed porous structure. Moreover, TMO grows uniformly in-situ on AC surface and displays a small size below 10 nm. The prepared Fe2O3-ACFe and MnO2-ACMn composites exhibit remarkable specific capacitance of 645.0 and 548.0 F g−1, respectively. Hybrid aqueous supercapacitors are assembled with Fe2O3-ACFe and MnO2-ACMn as negative and positive electrodes, respectively. A stable operating voltage of 1.2 V is achieved in the KOH electrolyte, resulting in a remarkable 90.2% capacitance retention over 10,000 cycles. Furthermore, in the Na2SO4 electrolyte, a wide 1.6 V voltage window is obtained, contributing to a substantial energy density of 49.35 Wh kg−1. This work provides an interesting approach for the fabrication of high-performance TMO-carbon composite electrodes.

Broadening the Voltage Window of 3D-Printed MXene Micro-Supercapacitors with a Hybridized Electrolyte.

The burgeoning demand for miniaturized energy storage devices compatible with the miniaturization trend of electronic technologies necessitates advancements in micro-supercapacitors (MSCs) that promise safety, cost efficiency, and high-speed charging capabilities. However, conventional aqueous MSCs face a significant limitation due to their inherently narrow electrochemical potential window, which restricts their operational voltage and energy density compared to their organic and ionic liquid counterparts. In this study, we introduce an innovative aqueous NaCl/H2O/EG hybrid gel electrolyte (comprising common salt (NaCl), H2O, ethylene glycol (EG), and SiO2) for Ti3C2Tx MXene MSCs that substantially widens the voltage window to 1.6 V, a notable improvement over traditional aqueous system. By integrating the hybrid electrolyte with 3D-printed MXene electrodes, we realized MSCs with remarkable areal capacitance (1.51 F cm-2) and energy density (675 µWh cm-2), significantly surpassing existing benchmarks for aqueous MSCs. The strategic formulation of the hybrid electrolyte-a low-concentration NaCl solution with EG-ensures both economic and environmental viability while enabling enhanced electrochemical performance. Furthermore, the MSCs fabricated via 3D printing technology exhibit exceptional flexibility and are suitable for modular device integration, offering a promising avenue for the development of high-performance, sustainable energy storage devices. This advancement not only provides a tangible solution to the challenge of limited voltage windows in aqueous MXene MSCs but also sets a new precedent for the design of next-generation MSCs that align with the needs of an increasingly microdevice-centric world.

Aqueous hybrid iron-ion battery capacitors with ultra-long cycle life

With the over-exploitation of lithium resources, there is a tendency to find a new metal-ion energy storage device to replace lithium-ion batteries. In recent years, Fe-ion energy storage devices are acknowledged for their low cost, abundant resources, and safe characteristics, but their full potential has yet to be widely explored. Herein, we propose a new hybrid iron-ion battery capacitor (H-IIBC) energy storage device. The H-IIBC device prepared with nano flower-like activated carbon (FAC) as the cathode material, high-purity iron sheet as the anode material, and 1 M FeSO4 + NH4Cl aqueous solution as the electrolyte. After atomic molecular dynamics simulations and ex situ characterization analysis, ion adsorption/desorption occurs on the surface of the FAC cathode during the charging/discharging process, accompanied by the redox of iron ions. The stripping/deposition of iron occurs at the high-purity iron anode. With the charging/discharging process, the reaction at the anode favors the interconversion between Fe2+ and Fe3+ which requires less energy, thus ensuring that the high purity iron will not be depleted. Thus, the specific capacitance of prepared H-IIBC could reach 644 mF g−1 (399 mF cm−2) at a current density of 1 mA cm−2 in the voltage window of 0–1 V and shows ultra-high cycling stability at 3,000 cycles test. This economical, long-life and safe H-IIBC is expected to realize great potential in the field of energy storage in the near future.

Ultrafast Metal-Free Microsupercapacitor Arrays Directly Store Instantaneous High-Voltage Electricity from Mechanical Energy Harvesters.

Harvesting renewable mechanical energy is envisioned as a promising and sustainable way for power generation. Many recent mechanical energy harvesters are able to produce instantaneous (pulsed) electricity with a high peak voltage of over 100 V. However, directly storing such irregular high-voltage pulse electricity remains a great challenge. The use of extra power management components can boost storage efficiency but increase system complexity. Here utilizing the conducting polymer PEDOT:PSS, high-rate metal-free micro-supercapacitor (MSC) arrays are successfully fabricated for direct high-efficiency storage of high-voltage pulse electricity. Within an area of 2.4 × 3.4cm2 on various paper substrates, large-scale MSC arrays (comprising up to 100 cells) can be printed to deliver a working voltage window of 160V at an ultrahigh scan rate up to 30V s-1 . The ultrahigh rate capability enables the MSC arrays to quickly capture and efficiently store the high-voltage (≈150V) pulse electricity produced by a droplet-based electricity generator at a high efficiency of 62%, significantly higher than that (<2%) of the batteries or capacitors demonstrated in the literature. Moreover, the compact and metal-free features make these MSC arrays excellent candidates for sustainable high-performance energy storage in self-charging power systems.

Internal Vanadium Doping and External Modification Design of P2-Type Layered Mn-Based Oxides as Competitive Cathodes toward Sodium-Ion Batteries.

P2-type layered manganese-based oxides have attracted considerable interest as economical, cathode materials with high energy density for sodium-ion batteries (SIBs). Despite their potential, these materials still face challenges related to sluggish kinetics and structural instability. In this study, a composite cathode material, Na0.67 Ni0.23 Mn0.67 V0.1 O2 @Na3 V2 O2 (PO4 )2 F was developed by surface-coating P2-type Na0.67 Ni0.23 Mn0.67 V0.1 O2 with a thin layer of Na3 V2 O2 (PO4 )2 F to enhance both the electrochemical sodium storage and material air stability. The optimized Na0.67 Ni0.23 Mn0.67 V0.1 O2 @5wt %Na3 V2 O2 (PO4 )2 F exhibited a high discharge capacity of 176 mA h g-1 within the 1.5-4.1 V range at a low current density of 17 mA g-1 . At an increased current density of 850 mA g-1 within the same voltage window, it still delivered a substantial initial discharge capacity of 112 mAh g-1 . These findings validate the significant enhancement of ion diffusion capabilities and rate performance in the P2-type Na0.67 Ni0.33 Mn0.67 O2 material conferred by the composite cathode.