Composite Cathode Research Articles

Screen‐Printed Composite LiFePO4‐LLZO Cathodes Towards Solid‐State Li‐ion Batteries

AbstractLiFePO4 (LFP) is widely used as cathode material for its low cost, high safety, and good thermal properties. It is one of the most exploited cathode materials for commercial Li‐ion batteries (LIBs). Herein, we present a screen‐printing method to prepare a LFP composite cathode, and a rational combination of the typical composite solid electrolytes (CSE) consisting of polyethylene oxide (PEO)/Li‐salt (LiTFSi) electrolyte with ceramic filler (LLZO or Li6.4La3Zr1.4Ta0.6O12 (LLZTO)) has been successfully demonstrated for SSB. The prepared CSE offers: i) a promising ionic conductivity (0.425 mS cm−1 at 60 °C), ii) a wide electrochemical window (>4.6 V), iii) a high Li‐ion transference number (tLi+=0.44), iv) a good interfacial compatibility with the electrode, v) a good thermal stability, and vi) a high chemical stability toward Li metal anode. The Li/CSE/Li symmetric cells can be cycled for more than 1000 h without Li‐dendrites growth at a current density of 0.2 mA cm−2. The final cell screen‐printed LFP composite cathode (LFP+LLZO)//Li metal displays a high reversible specific capacity of 140 mAh g−1 (0.1 C) and 50 mAh g−1 (0.5 C) after 1st and 500th cycles.

Enabling High-Performance Battery Electrodes by Surface-Structuring of Current Collectors and Crack Formation in Electrodes: A Proof-of-Concept

Today's society and economy demand high-performance energy storage systems with large battery capacities and super-fast charging. However, a common problematic consequence is the delamination of the mass loading (including, active materials, binder and conductive carbon) from the current collector at high C-rates and also after certain cycle tests. In this work, surface structuring of aluminum (Al) foils (as a current collector) is developed to overcome the aforementioned delamination process for sulfur (S)/carbon composite cathodes of Li-S batteries (LSBs). The structuring process allows a mechanical interlocking of the loaded mass with the structured current collector, thus increasing its electrode adhesion and its general stability. Through directed crack formation within the mass loading, this also allows an enhanced electrolyte wetting in deeper layers, which in turn improves ion transport at increased areal loadings. Moreover, the interfacial resistance of this composite is reduced leading to an improved battery performance. In addition, surface structuring improves the wettability of water-based pastes, eliminating the need for additional primer coatings and simplifying the electrode fabrication process. Compared to the cells made with untreated current collectors, the cells made with structured current collectors significantly improved rate capability and cycling stability with a capacity of over 1000mAhg−1. At the same time, the concept of mechanical interlocking offers the potential of transfer to other battery and supercapacitor electrodes.

Sandwich-like high-performance Ti3C2Tx MXene/NiCo2O4 nanosphere composites for asymmetric supercapacitor application

NiCo2O4 is a promising electrode material for supercapacitors due to its low cost, high theoretical specific capacitance and good cycling stability. However, NiCo2O4 has the disadvantages of poor electronic and ionic conductivities and easy agglomeration. Moreover, the irreversible structural damage caused by the NiCo2O4 volume expansions during charging and discharging limits its use in supercapacitors. Herein, we fabricated sandwich Ti3C2Tx MXene/NiCo2O4 composites via an electrostatic self-assembly method. The problem of easy agglomeration of the NiCo2O4 nanospheres was solved by intercalating Ti3C2Tx MXene layers with the NiCo2O4 nanospheres. Furthermore, the Ti3C2Tx MXene layer was also utilized as a protective layer to limit serious volume expansion and protect the structure of NiCo2O4 nanospheres from destruction. The results showed that the prepared Ti3C2Tx MXene/NiCo2O4 composite exhibited a high specific capacitance of 1025 F g−1 at a current density of 1 A g−1 and had an initial capacity of 81 % when the current density was increased to 10 A g−1. The Ti3C2Tx MXene/NiCo2O4 composite cathode and activated carbon anode were assembled in an asymmetric supercapacitor, which showed an energy density of 36.67 Wh kg−1 at 800 W kg−1 and a capacity retention of 88.2 % after 5000 cycles.

Rapid mechanochemical synthesis of high-performance Na4Fe2.94Al0.04(PO4)2(P2O7)/C cathode material for sodium-ion storage

Na4Fe3(PO4)2(P2O7) is regarded as a promising cathode material for sodium-ion batteries due to its affordability, non-toxic nature, and excellent structural stability. However, its electrochemical performance is hampered by its poor electronic conductivity. Meanwhile, most of the previous studies utilized spray-drying and sol–gel methods to synthesize Na4Fe3(PO4)2(P2O7), and the large-scale synthesis of the cathode material is still challenging. This study presents a composite cathode material, Na4Fe2.94Al0.04(PO4)2(P2O7)/C, prepared via a straightforward ball-milling technique. By substituting Al3+ minimally into the Fe2+ site of NFPP, Fe defects are introduced into the structure, hindering the formation of NaFePO4 and thereby enhancing Na-ion diffusion kinetics and conductivity. Additionally, the average length of AlO bonds (2.18 Å) is slightly smaller than that of FeO bonds (2.19 Å), contributing to the superior structural stability. The smaller ionic radii of Al3+ induce lattice contraction, further enhancing the structural stability. Moreover, the surface of material particles is coated with a thin layer of carbon, ensuring excellent electrical conductivity and outstanding structure stability. As a result, the Na4Fe2.94Al0.04(PO4)2(P2O7)/C cathode exhibits excellent electrochemical performance, leading to high discharge capacity (128.1 mAh g−1 at 0.2 C), outstanding rate performance (98.1 mAh g−1 at 10 C), and long cycle stability (83.7 % capacity retention after 3000 cycles at 10 C). This study demonstrates a low-cost, ultra-stable, and high-rate cathode material prepared by simple mechanical activation for sodium-ion batteries which has application prospects for large-scale production.

High Ionic Conductive, Mechanical Robust Sulfide Solid Electrolyte Films and Interface Design for All‐Solid‐State Lithium Metal Batteries

AbstractAll‐solid‐state lithium batteries (ASSLBs) are considered a promising technology for next‐generation energy storage systems due to their inherent safety. However, the conventional laboratory‐scale ASSLBs reported to date are based on pellet‐type structures with thick solid electrolyte layers, leading to challenges related to low energy densities and poor electrochemical performance. In this study, porous adhesive poly(ethylene vinyl acetate) (PEVA) scaffolds and polytetrafluoroethylene (PTFE) binders are utilized to interweave sulfide solid electrolytes into freestanding films with an ultra‐low thickness of 40 µm, high ionic conductivity of 1.1 mS cm−1, and a high tensile strength of 74 MPa. To mitigate the reduction reaction between the PTFE binder and the lithium metal anode, a Li3N‐rich solid electrolyte interphase (SEI) in situ on lithium metal is formed, and the assembled symmetric cell shows excellent cycling stability within 800 h at the current density of 0.2 mA cm−2 and room temperature. Additionally, the ASSLBs using oxidatively stable Li2ZrCl5F in the composite cathode and the prepared solid electrolyte film demonstrate exceptional cycling performance and fast‐charging capability, with a high cell‐level energy density of 354.4 Wh kg−1. The ASSLBs prepared by coupling E‐LPSCl film and stable interface design exhibit excellent electrochemical performance and a high cell‐level energy density.

Crystalline Structure and Optical Properties of Cobalt Nickel Oxide Thin Films Deposited with a Pulsed Hollow-Cathode Discharge in an Ar+O2 Gas Mixture

Cobalt nickel oxide films are deposited on Si(111) or fluorine-doped tin-oxide-coated (FTO) glass substrates employing a pulsed hollow-cathode discharge. The hollow cathode is operated with argon gas flowing through the nozzle and with O2 gas admitted to the vacuum chamber. Three different cathode compositions (Co20Ni80, Co50Ni50, and Co80Ni20) are investigated. Deposited and annealed thin films are characterized by X-ray diffraction, infrared (Raman) spectroscopy, and ellipsometry. As-deposited films consist of a single mixed cobalt nickel oxide phase. Upon annealing at 600 °C, the mixed cobalt nickel oxide phase separates into two cystalline sub-phases which consist of cubic NiO and cubic Co3O4. Annealed films are investigated by spectroscopic ellipsometry and the optical bandgaps are determined.

Nitrogen-doped carbon nanotube encapsulated Co9S8 composite cathode for high-selective capacitive extraction of uranium (VI) from radioactive wastewater

Selective extraction of uranium [U(VI)] from uranium containing nuclear wastewater is of great significance in alleviating the uranium resources shortages and eliminating the radioactive radiation. Benefited by the merits of cost-effectiveness and environment-friendliness, capacitive deionization (CDI) shows a great promise towards selective removal of U(VI). However, exploring novel electrode materials with high intrinsic affinity rather than the excessive assistance of external means faces challenges. Herein, a nitrogen-doped carbon tube encapsulated Co9S8 composite (CS-NCNT) was developed as a Faradic cathode for selective electrosorption of U(VI) from radioactive wastewater. This work mainly emphasized on these following results: (i) The electrochemical redox activity and high surface-controlled ratios endowed the optimized CS-NCNT-2 electrode a maximum electrosorption capacity (189 mg g−1) towards U(VI). (ii) Except that CS-NCNT-2 exhibited excellent selective electrosorption performance in U(VI)-containing spiked real seawater, an ultrahigh selectivity coefficient of 707 (UO22+ over Na+) was also achieved at a Na+: UO22+ molar ratio of 200. (iii) The valence state analysis and molecular dynamic simulation revealed the essence of the reversible electrosorption-desorption process and the preferable extraction towards UO22+ compared with Na+ ions, respectively. Overall, this work can be potentially expanded to other metal chalcogenides-based electrode materials for selective removal of UO22+ even other radionuclide in U(VI)-containing radioactive wastewater.

Ce/Fe bimetallic MOF derivatives in situ modified bulk carbon aerogel composite cathode for efficient heterogeneous electro-fenton degradation of chloramphenicol

In this study, we utilized a Ce-modified iron-based metal-organic framework derivative to in situ modify bulk CA (Ce/Fe@C-CA) as a bifunctional composite cathode to degrade chloramphenicol (CAP) in the heterogeneous electro-Fenton (EF) process. The composite cathode exhibited satisfactory CAP degradation efficiency, wide pH adaptability (2–9) and low metal leaching. Under the appropriate conditions (pH = 5, current density = 6 mA/cm2), 94.89% of CAP degradation efficiency was obtained within 60 min. The introduction of Ce increased the oxygen vacancy content, enhanced the cathodic electrochemical activity, promoted the production of a variety of reactive oxygen species and participates in the degradation of CAP, of which ·OH and 1O2 were dominant. Meanwhile, the electron transfer and synergistic catalysis between Ce and Fe promoted the regeneration of the metal active site, which was beneficial to improve the reuse stability of the Ce/Fe@C-CA cathode. The degradation pathway of CAP was obtained by DFT calculations and UPLC-MS/MS detection. This study not only proposed a novel bifunctional electro-Fenton cathode, but also provided a effective strategy for the treatment of actual pharmaceutical wastewater.

Engineering Detrimental Functional Groups in Conductive Additives Toward High-Performance All-Solid-State Batteries.

Conductive additives are of great importance for the adequate utilization of active materials in all-solid-state lithium batteries by establishing conductive networks in the composite cathode. However, it usually causes severe interfacial side reactions with solid electrolytes, especially sulfide electrolytes, leading to sluggish ion transportation and accelerated performance degradation. Herein, a simple hydrogen thermal reduction process is proposed on a commonly used conductive additive Super P, which effectively removes the surface oxygen functional groups and weakens the interfacial side reactions with sulfide. With a small amount of 1 wt % reduced Super P, ASSLBs demonstrates a competitive capacity of 180.2 mAh g-1 , which is much higher than the 130.8 mAh g-1 of untreated Super P. Impressively, reduced Super P based ASSLBs also exhibit a higher capacity retention of 81.8 % than 64.6 % of untreated Super P. The cathode interfacial chemical evolutions reveal that reduced Super P could effectively alleviate the side reactions of sulfide. Reduced Super P shows better reversible capacity compared to reduced carbon nanofiber with almost no loss of capacity retention, due to its more complete conductive network. Our results highlight the importance of oxygen-containing functional groups for conductive additives, lightening the prospect of low-cost 0D conductive additives for practical ASSLBs.

Rate-limiting mechanism of all-solid-state battery unravelled by low-temperature test-analysis flow

All-solid-state batteries (ASSBs) with potentially improved energy density and safety have been recognized as the next-generation energy storage technology. However, their performances at subzero temperatures are rarely investigated, with rate-limiting process/mechanisms unidentified. Herein, the rate-limiting process/mechanisms for -40℃ ASSBs are accurately identified/analyzed by developing a standard test-analysis flow model. We reveal that the rate-limiting processes of LiCoO2 (LCO)+sulfide solid electrolyte (SE) composite cathode are the sluggish ion transport across unfavorable interfacial reaction layer and charge transfer at damaged LCO cathode surface. After inserting Li2ZrO3 (LZO) coating layer to suppress interfacial reactions, the rate-limiting process of LCO@LZO+sulfide SE composite cathode turns into the arduous ion transport across the interphase composed of the self-decomposition products of sulfide SE. Interestingly, by replacing sulfide SE with halide SE, LCO+halide SE composite cathode delivers fast charge transfer and the ion conduction through the thick SE separator becomes the rate-limiting process, thus enabling a superior capacity retention rate (41.4 %) at -40℃. Furthermore, the capacity retention of ASSB coupling LCO+halide SE composite cathode with Si anode can be boosted from 28.9 % to 38.6 % at -40℃ by employing superionic conductor with low activation energy. These successful identifications/modulations on rate-limiting process/mechanism and improvements on low-temperature performance demonstrate the significant role of this test-analysis flow in propelling the development of low-temperature ASSBs.

Optimization of two-dimensional solid-state electrolyte–anode interface by integrating zinc into composite anode with dual-conductive phases

Solid-state electrolytes (SSEs) are a solution to safety issues related to flammable organic electrolytes for Li batteries. Insufficient contact between the anode and SSE results in high interface resistance, thus causing the batteries to exhibit high charging and discharging overpotentials. Recently, we reduced the overpotential of Li stripping and plating by introducing a high proportion of dual-conductive phases into a composite anode. The current study investigates the interface resistance and stability of a composite electrode modified with Zn and a lower proportion of dual-conductive phases. Zn-cation-adsorbed Prussian blue is synthesized as an intermediate component for a Zn-modified composite electrode (Li-FeZnNC). The Li-FeZnNC symmetric cell presents a lower interface resistance and overpotential compared with Li-FeNC (without Zn modification) and Li-symmetric cells. The Li-FeZnNC symmetric cell shows high electrochemical stability during Li stripping and plating at different current densities and high stability for 200 h. Full batteries with a Li-FeZnNC composite anode, garnet-type SSE, and LiFePO4 cathode show low charging and discharging overpotentials, a capacity of 152 mAh g−1, and high stability for 200 cycles.

On the Origin of Anode and Cathode Contributions to the Impedance of All‐Solid‐State Batteries

AbstractAll‐solid‐state‐batteries (ASSBs) are considered as promising next‐generation batteries in order to achieve improvements in both energy density and safety. The complex electrochemical processes in ASSBs taking place on different time scales can be probed by means of electrochemical impedance spectroscopy. However, the separation of anode and cathode contributions to the impedance and the understanding of the underlying electrochemical processes in both electrodes is a challenging task. Here, we compare the impedance spectrum of a prototypical full ASSB to those of symmetric cells anode | separator | anode and cathode | separator | cathode. We use Ni‐rich polycrystalline LiNi0.85Co0.10Mn0.05O2 particles as active material inside the composite cathode and an indium‐lithium alloy as anode. Based on the comparison, we show that the charge transfer process inside the cathode is remarkably fast, i. e., even faster than observed for cathodes of batteries with liquid electrolyte. Our results give indication that the differences in the time scales of cathode and anode processes are related to the distinct transport properties of interphases inside the cathode and at the anode | separator interface, respectively.

In-situ polymerisation of fluorene to achieve theoretical capacity in LiFePO4 cells

This study aims to enhance the electrochemical properties of solid-state lithium-ion batteries by modifying the cathode material, LiFePO4 (LFP), via fluorene addition and in-situ polymerisation. The first modification process involves creating a shell structure (the film thickness of 10 nm) around each LFP particle and establishing a net-like structure to connect the particles before the in-situ polymerisation. Then, electrochemical in-situ polymerisation during battery cycling with a low current and obtaining the composite cathode of lithium iron phosphate (LFP) and polyfluorene. The results demonstrate that adding 20 wt.% fluorene significantly reduces the transfer resistance and enhances the rate performance with the capacity retention of 95.2 % (from 0.1C to 2C and return to 0.2C) of the solid-state batteries. Additionally, the modified LFP cathode demonstrates excellent long-term cycling performance and exhibits capacity (167.2 mAh/g in 0.2 C) close to the theoretical limit, and Coulombic efficiency remains at 99.2 %.

Advanced TiO2/Al2O3 Bilayer ALD Coatings for Improved Lithium-Rich Layered Oxide Electrodes.

Surface modification is a highly effective strategy for addressing issues in lithium-rich layered oxide (LLO) cathodes, including phase transformation, particle cracking, oxygen gas release, and transition-metal ion dissolution. Existing single-/double-layer coating strategies face drawbacks such as poor component contact and complexity. Herein, we present the results of a low-temperature atomic layer deposition (ALD) process for creating a TiO2/Al2O3 bilayer on composite cathodes made of AS200 (Li1.08Ni0.34Co0.08Mn0.5O2). Electrochemical analysis demonstrates that TiO2/Al2O3-coated LLO electrodes exhibit improved discharge capacities and enhanced capacity retention compared with uncoated samples. The TAA-5/AS200 bilayer-coated electrode, in particular, demonstrates exceptional capacity retention (∼90.4%) and a specific discharge capacity of 146 mAh g-1 after 100 cycles at 1C within the voltage range of 2.2 to 4.6 V. The coated electrodes also show reduced voltage decay, lower surface film resistance, and improved interfacial charge transfer resistances, contributing to enhanced stability. The ALD-deposited TiO2/Al2O3 bilayer coatings exhibit promising potential for advancing the electrochemical performance of lithium-rich layered oxide cathodes in lithium-ion batteries.

A composite cathode of biofuel cell based on cross‐linked Poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate and platinum nanoparticles

AbstractGlucose oxidase based enzymatic biofuel cell is the promising technology for implantable medical devices’ power supply. It can open up opportunities for the long‐term implantation of the medical devices like pacemakers without the necessity for replacement of the batteries. Increasing of the cathode efficiency is one of the issues that should be solved before a practical application of biofuel cells. The high catalytic activity of the cathode provides a significant contribution to the efficiency of biofuel cells operation. The creation of cathodes of implantable biofuel cell with the increased power density could resolve the problem with a slow kinetics of the cathodic oxygen reduction reaction. It is especially urgent in the conditions of implantation in physiological fluids, where the oxygen concentration is relatively low. Enzymes application could be an optimal way to increase an efficiency of the cathodic reaction, but enzymes long‐time stability is still in question. Thus, non‐organic and synthetic organic catalysts are considered. In this study, a new type of a cathode for enzymatic biofuel cells is presented. This cathode combines two catalysts: inorganic with platinum nanoparticles (PtNPs) and organic in the form of poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) cross‐linked by poly(ethylene glycol) diglycidyl ether (PEGDE). The received electrodes were investigated by several electrochemical methods: cyclic voltammetry, chronopotentiometry and linear sweep voltammetry method on a rotating disk electrode. It was shown that the combination of PtNPs and PEDOT:PSS provides the maximum cathodic current, due to the fact that both catalysts contribute to the oxygen reduction reaction. The maximum cathodic current was 7.5 μA for an electrode containing 5 % PEGDE with PtNPs, heat‐treated for one hour at 120 °C. The electrodes without platinum nanoparticles were also investigated. This research showed that PEDOT:PSS provides a significant contribution to the overall catalytic effect demonstrated by the electrode proposed in the study. Scanning electron microscopy and X‐ray fluorescence analysis studies showed that the electrodes with combination of PtNPs and PEDOT:PSS were almost fully covered by catalysts.

High performance all-solid-state Li–Se battery based on selenium loaded on Ti3C2 MXene cathode

Selenium has high theoretical volumetric capacity of 3253 mAh cm−3 and acceptable electronic conductivity of 1 × 10−5 S m−1, which is considered as a potential alternative to sulfur cathode for all-solid-state rechargeable batteries with high energy density. However, the development of all-solid-state Li–Se batteries (ASSLSBs) are hindered by sluggish kinetics and poor cycling life. In this work, trigonal Se nanocrystallines are homogenously distributed in the interspace and on the surface of MXene layers (denoted as Se@MXene composite) by a novel melt-diffusion method. ASSLSBs based on this Se@MXene composite cathode exhibit large specific capacity of 632 mAh g−1 at 0.05 A g−1, high-rate capability over 4 A g−1, and excellent cycling stability over 300 cycles at 1 A g−1. The ex-situ analytical techniques demonstrate that the excellent electrochemical performance of Se@MXene cathode largely arises from structural stability with the assistance of conductive MXene and reversible redox behavior between Li2Se and Se during the repeating charge/discharge process. Our study points out the potential of material design of Se cathode based on conducting 2D materials with good electrochemical behavior, which may accelerate the practicability of ASSLSBs.

Preparation of Mn2O3/Fe2O3 composite cathode material for zinc ion batteries from the reduction leaching solution of manganese ore tailing

The high-value utilization of tailings is crucial for saving limited resources and supporting the sustainable development of society. In the present work, a Mn2O3/Fe2O3 composite is prepared from manganese ore tailing through reduction leaching and thermal decomposition methods. Further, the zinc storage performance of the Mn2O3/Fe2O3 composite for zinc ion batteries (ZIBs) is explored. The Mn2O3/Fe2O3 composite maintains a specific capacity of 224.8 mA h g−1 after 300 cycles at 500 mA g−1, suggesting its potential applications in ZIBs. CV and GITT analysis reveal that the Mn2O3/Fe2O3 composite has an obvious pseudocapacitive behavior during the charge/discharge process, and the Zn2+ diffusion coefficient ranges in the orders of 10−14-10−12 cm2 s−1. The charge/discharge mechanism of the Mn2O3/Fe2O3 composite is also explored using ex-situ XRD and XPS measurements. The work provides a new avenue for the high-value use of manganese ore tailing in the electrochemical energy storage field.

Cobalt nanoparticles embedded in nitrogen-doped carbon nanofibers to enhance redox kinetics for long-cycling sodium–sulfur batteries

The shuttle effect resulting from severe volume expansion and polysulfide dissolution imposes limitations to the application of sodium–sulfur (Na–S) batteries. Herein, a three-dimensional self-supported electrode comprised of cobalt nanoparticles embedded in nitrogen-doped carbon nanofibers (CoNCNFs) is constructed to accommodate sulfur as the cathode for Na–S batteries. The carbon fiber framework facilitates direct electrons transmission and reduces the overall contact impedance of the electrode. The abundant pore structure not only promotes electrolyte infiltration but also ensures high loading of sulfur and provides space for volume expansion during charging and discharging. Most significantly, the CoNCNF carrier accelerates the conversion rate of sodium polysulfides into Na2S and guide Na2S deposition on its surface in a three-dimensional progressive nucleation (3DP) mode, resulting in a high Na2S deposition capacity and outstanding long-term cycling performance. When coupled with a Na-metal anode, the CoNCNF/S composite cathode exhibits stable electrochemical properties with a capacity up to 1030.2 mA h/g after 300 cycles at 0.2 C and excellent rate performance.

High‐Capacity, Long‐Life Sulfide All‐Solid‐State Batteries with Single‐Crystal Ni‐Rich Layered Oxide Cathodes

AbstractSulfide all‐solid‐state battery (SASSB) with ultrahigh‐nickel layered oxide cathode (LiNixCoyMn1‐x‐yO2, NCM, x ≥ 0.9) offers the potential of high energy density and safety for superior energy storage systems. However, stable cycling is difficult to realize due to adverse interfacial reactions, space charge layer (SCL), and elemental diffusion. Herein, a straightforward solid‐phase coating strategy is exploited to synthesize Ni90‐S cathode, which greatly improves the charge transmission capability of the composite cathode and suppresses interfacial reactions in SASSB. The consequent SC‐Ni90‐0.2%S/Li6PS5Cl/Li4Ti5O12 SASSB exhibits enhanced electrochemical performance, including a long life of 500 cycles with 87% capacity retention at 1C, high areal capacity of 11.44 mAh cm−2, and excellent rate performance at 20 C. These results promise an efficient strategy for designing cathode materials for SASSBs.

Toward high stability of O3‐type NaNi1/3Fe1/3Mn1/3O2 cathode material with zirconium substitution for advanced sodium‐ion batteries

AbstractWe successfully synthesized a series of O3‐type NaNi1/3Fe1/3Mn1/3−xZrxO2 (x = 0, 0.01, 0.02, 0.04) cathode materials by the solid‐state reaction method. Energy dispersion spectroscopy, X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy results confirmed the successful incorporation of Zr elements into the lattice to substitute Mn. Due to the introduction of Zr4+, the crystal structure modulation of O3‐NaNi1/3Fe1/3Mn1/3O2 has been realized. By increasing the Zr4+ content, the width of the sodium diffusion layer expands, thereby facilitating the diffusion of sodium ions. Consequently, the material exhibits a remarkable enhancement in high‐rate capability. At the same time, increasing the Zr4+ content results in a notable decrease in both the average bond length of TM−O and the thickness of the TMO6 octahedron in the transition metal layer, resulting in a significant improvement in the cycling performance and structural stability of the cathode material. Additionally, the in‐situ XRD results demonstrate that the optimized cathode composition of O3‐NaNi1/3Fe1/3Mn1/3–0.02Zr0.02O2 (NFMZ2) undergoes a reversible phase transition of O3 → O3 + P3 → P3 → O3 + P3 → O3 during the charge–discharge process.