High-performance Cathode Materials Research Articles

Internal doping and surface coating: Mn / La-HCF @ Fe-HCF composites as high-performance cathode materials for sodium-ion batteries

Internal doping and surface coating: Mn / La-HCF @ Fe-HCF composites as high-performance cathode materials for sodium-ion batteries

Zn-doped hollow cubic MnO2 as a high-performance cathode material for Zn ion batteries.

Manganese-based compounds have the characteristics of high theoretical capacity, low cost and stable performance, thus become a research hotspot for cathode materials of zinc-ion batteries (ZIBs). However, in the process of charging and discharging, it is accompanied by problems such as structural collapse and low conductivity, which resulted in severe capacity degration during cycles. In this paper, a kind of Zn2+ doped MnO2 hollow cube cathode material (Zn-MnO2) was prepared by self-sacrificing template method. The Zn2+ doped in MnO2 crystals can induce oxygen vacancies in the structure, thereby improving the structural stability ion diffusion coefficient and electrical conductivity of the material. After 100 cycles at 0.3 A g-1, the high specific capacity of 281.2 mA h g-1 is still maintained. Through ex-situ XPS and ex-situ XRD tests, the mechanism of charge-discharge process was discussed. The results show that the storage mechanism of Zn-MnO2 is H+ and Zn2+ insertion/removal and Mn3+/Mn2+ two-electron reaction pathway. The total state density (TDOS) and partial state density (PDOS) of Zn-MnO2 and MnO2 further demonstrated that the doping of Zn2+ enhanced the electron conductivity and is beneficial to the electron transfer during the electrochemical reaction.

Rational design of α-MnO2@TiO2 composites for high-performance zinc ions batteries

Aqueous zinc ions batteries (AZIBs) have attracted widespread interest due to their remarkable energy density, non-toxicity, environmental friendliness and low cost. However, the application of MnO2 cathode materials for AZIBs is limited owing to the dissolution of Mn2+, structural collapse and intrinsic poor conductivity. Herein, α-MnO2@TiO2 composites were synthesized via simple hydrothermal and calcination approaches. Some smaller TiO2 were coated on the MnO2 nanorods to form the protective layer. The TiO2 protective layer not only prevents the dissolution of Mn2+ and structural collapse of MnO2, but also enhances the conductivity of the material due to the presence of Ti3+ defects, which increased electrode materials wettability, specific surface area and diffusion rate of Zn2+. In addition, the coating TiO2 causes surface adsorbed oxygen and surface binding defects in α-MnO2@TiO2, and increases surface reactivity and electrochemically active sites, which provides abundant channels and available insertion electrochemically active sites for H+/Zn2+ transport. As a result, α-MnO2@TiO2–2 delivers a high specific capacity of 182.90 mAh g−1 at 1 A g−1 after 600 cycles and outstanding rate capacity of 127.91 mAh g−1 at 5 A g−1. This work provides an idea for exploring high-performance cathode materials for AZIBs.

Delaying cyclization of polyacrylonitrile by boric acid for sulfurized poly(acrylonitrile) cathode materials

Sulfurized poly(acrylonitrile) (SPAN) has become one of the most promising cathode materials in rechargeable Lithium-Sulfur (Li-S) batteries due to their inhibited polysulfide dissolution, high sulfur utilization and excellent electrochemical performance via unique solid–solid conversion mechanism. However, the sulfur content of SPAN (<50 %) is still one of the significant reasons that restrict the electrochemical performance and practical applicability. In this paper, a small amount of boric acid (HBO) was introduced into the precursor of SPAN cathode materials easily before heat-treating, to increase the sulfur content and improve the electrochemical performance. Meanwhile, the results of first principles calculation suggested that the increase of sulfur content of SPAN was derived from the delayed cyclization of polyacrylonitrile (PAN) by HBO. We also discovered when the additive amount of HBO was 1.5 % of PAN mass, the SPAN cathode material possessed high sulfur content up to 54.24 wt%, and delivered prominent reversible electrochemical performances of 714 mAh/g at 0.2C and 734 mAh/g at 0.1C with high Coulombic efficiency. In summary, we proposed a simple and easy method to improve sulfur content and introduced a new strategy for the design of high-sulfur content and high-performance SPAN cathode materials.

Suppressing vacancies and crystal water of sodium manganese iron-based Prussian blue analogue by potassium doping for advanced sodium-ion batteries

Sodium manganese iron-based Prussian blue analogue (MnFe-PBAs) is regarded as potential cathode material for sodium-ion batteries due to its simple synthesis process, low production cost, and high theoretical capacity. Unfortunately, electrochemical performances of MnFe-PBAs are inevitably hindered owing to the crystal vacancies and crystal water produced from aqueous co-precipitation process. Herein, highly crystallized cubic potassium-doped sodium manganese iron-based Prussian blue analogue is synthesized by a modified co-precipitation method. By introducing a larger ionic radius potassium (K) to substitute the part of Na in the MnFe-PBAs, a coexistence composite of sodium and potassium phases is obtained with less crystal water and fewer vacancies compared with pure sodium phase compound, resulting that potassium-doped sodium manganese iron-based Prussian blue analogue (Na1.08K0.74Mn[Fe(CN)6]0.86⋅□0.14⋅1·.86H2O, NaKMHCF) can deliver high discharge specific capacity (129.3 mAh/g at 10 mA g−1), excellent rate performance (82.3 mAh/g at 1500 mA g−1) as well as high cycling stability (77.0 % capacity retention at 500 mA g−1 after the 500th cycle). Besides, the full cell, based on NaKMHCF as cathode material and sodium titanium phosphate (NTP) as anode material, confirms its potential as high-performance cathode material for SIBs.

Liner Nanostructure of Metal Boride as a Cathode Material for High-Performance and Flexible Solid-State Asymmetric Hybrid Battery Supercapacitors

Liner Nanostructure of Metal Boride as a Cathode Material for High-Performance and Flexible Solid-State Asymmetric Hybrid Battery Supercapacitors

Sustainable Sulfur-Carbon Hybrids for Efficient Sulfur Redox Conversions in Nanoconfined Spaces.

Nanoconfinement is a promising strategy in chemistry enabling increased reaction rates, enhanced selectivity, and stabilized reactive species. Sulfur's abundance and highly reversible two-electron transfer mechanism have fueled research on sulfur-based electrochemical energy storage. However, the formation of soluble polysulfides, poor reaction kinetics, and low sulfur utilization are current bottlenecks for broader practical application. Herein, a novel strategy is proposed to confine sulfur species in a nanostructured hybrid sulfur-carbon material. A microporous sulfur-rich carbon is produced from sustainable natural precursors via inverse vulcanization and condensation. The material exhibits a unique structure with sulfur anchored to the conductive carbon matrix and physically confined in ultra-micropores. The structure promotes Na+ ion transport through micropores and electron transport through the carbon matrix, while effectively immobilizing sulfur species in the nanoconfined environment, fostering a quasi-solid-state redox reaction with sodium. This translates to ≈99% utilization of the 2e- reduction of sulfur and the highest reported capacity for a room temperature Na-S electrochemical system, with high rate capability, coulombic efficiency, and long-term stability. This study offers an innovative approach toward understanding the key physicochemical properties of sulfurcarbon nanohybrid materials, enabling the development of high-performance cathode materials for room-temperature Na-S batteries with efficient sulfur utilization.

Regulating Intermolecular Hydrogen Bonds in Organic Cathode Materials to Realize Ultra-stable, Flexible and Low-temperature Aqueous Zinc-organic Batteries.

Rational design of molecular structures is one of the effective strategies to obtain high-performance organic cathode materials. However, besides the optimization of single-molecule structures, the influence of the "weak" interaction forces (e.g. hydrogen bonds) in organic cathode materials on the performance of batteries should be fully considered. Herein, three organic small molecules with different numbers of hydroxyl groups (namely nitrogen heterocyclic tetraketone (DAB), monohydroxyl nitrogen heterocyclic dione (HDA), dihydroxyl nitrogen heterocyclic dione (DHT)) were selected as the cathodes of aqueous zinc ion batteries (AZIBs), and the effect of the intermolecular hydrogen bonds on their electrochemical performance was studied for the first time. Clearly, the stable hydrogen-bond networks built through the hydroxyl groups significantly enhance the cycle stability of organic small-molecule cathodes and facilitate rapid proton conduction between the hydrogen-bond networks through the Grotthuss mechanism, thereby endowing them with excellent rate performance. In addition, a larger and more dense two-dimensional hydrogen-bond network can be constructed through multiple hydroxyl groups, further enhancing the structural stability of organic small-molecule cathodes, giving them better cycle tolerance, excellent rate performance, and extreme environmental tolerance.

Sol-gel-based synthesis of high-capacity-NaCoO2 cathode for advanced sodium-ion batteries

This study presents a successful synthesis of phase-pure P2-NaCoO2 by improving the sol-gel-based calcination temperature, yielding a highly crystalline, well-ordered material having P63/mmc hexagonal symmetry, ideal for reversible sodium-ion batteries (SIBs). Advanced physicochemical techniques confirm its pure hexagonal crystal structure along with the desired stoichiometry. NaCoO2 in Na/1M-NaClO4/NaCoO2 cell demonstrates multiple redox peaks for Co3+/Co4+ redox couple, signifying stable multiphase transitions during charge/discharge cycles and exhibiting exceptional structural and electrochemical stability. The cell demonstrates a high discharge specific-capacity of 155.85 mAh/g at 0.1C with outstanding discharge capacity retention of 136.98, 100.6, 84.78, 78.31, and 72.46 mAh/g at the C-rates of 0.15, 0.2, 0.3, 0.5, and 1.0C, respectively, outperforming previously reported values. It shows a remarkable discharge-energy density of 466.04 Wh/kg at 0.1C. Additionally, the small solution and charge transfer resistance with extremely low double-layer capacitance signifies its excellent electrolyte conductivity and potential for high energy density and slow discharge application. These results imply that NaCoO2 is a high-performance and high-capacity cathode material for lightweight and compact SIBs.

Experimental and computational insights into oxygen vacancy-rich MoO2-x/N-doped carbon nanowires as high-performance cathode for magnesium batteries and magnesium-lithium hybrid batteries

This work aims to develop efficient cathode materials for magnesium based batteries, which are considered promising next-generation energy storage and conversion devices. One major challenge in magnesium based batteries is the strong Coulomb interaction between magnesium ions and cathode materials, which hinders ion storage and diffusion. To overcome this, we designed and synthesized oxygen vacancy-rich MoO2-x/N-doped carbon nanowires (MoO2-x-NC-NWS). The materials were prepared through a controlled synthesis process, ensuring the incorporation of N-doped carbon and oxygen vacancies, which play crucial roles in improving magnesium ion diffusion and storage. The prepared MoO2-x-NC-NWS demonstrated superior energy storage performance, achieving a capacity of 64 mAh/g in magnesium batteries and 263 mAh/g in magnesium-lithium hybrid batteries at a current density of 50 mA/g. Theoretical calculations further confirmed that oxygen vacancies enhance the diffusion capabilities of magnesium and lithium ions, thereby improving the overall energy storage performance. Therefore, the controllable synthesis of defects such as oxygen vacancies and the development of composite cathode materials are clearly effective strategies for enhancing the performance of magnesium-based battery cathodes. Meanwhile, this rational design of MoO2-based nanostructures provides valuable insights into the development of high-performance cathode materials for magnesium-based energy storage systems.

Modified structure of vanadium oxide via cadmium doping and in-situ activation for high-performance aqueous zinc ion storage

Vanadium oxides are promising cathode materials for aqueous zinc-ion batteries, but they suffer from severe crystal collapse and poor electrical/ionic conductivity. Herein, we successfully synthesized the designed cadmium-doped, carbon-coated vanadium oxide precursor with abundant oxygen vacancies (Cd0.015V2O3-x@C) using a straightforward one-pot thermal reduction method, followed by in-situ activation to form a high-performance cathode material, Cd0.004V2O5-y·nH2O@C. We find that the interlayered water dramatically reduces the electrostatic force between zinc ions and V2O5-y layers, meanwhile, abundant oxygen vacancies and cadmium doping alter the material’s band structure, resulting in enhanced electronic and ionic conductivities. Leveraging these advantages, the phase transitioned Cd0.004V2O5-y·nH2O@C cathode delivers a remarkably high capacity of 420 mAh/g (0.2 A/g), an excellent rate capability of 198 mAh/g (20.0 A/g), and an outstanding capacity retention of 78.5 % after 3500 cycles (20 A/g). This synergistic structure modification strategy of elemental doping and in-situ activation offers a novel approach to design high-performance vanadium oxide-based cathodes for advanced aqueous batteries.

Fabrication of High-performance LiCoO2 Cathode Materials by Regulated Resource Regeneration from Spent Lithium-Ion Batteries

Fabrication of High-performance LiCoO2 Cathode Materials by Regulated Resource Regeneration from Spent Lithium-Ion Batteries

Insight into the effect of Gd-doping on conductance and thermal matching of CeO2 for solid oxide fuel cell

GDC (Gd-doped CeO2) play a dual role in solid oxide fuel cell (SOFC), effectively blocking the reaction between YSZ (Y2O3-doped ZrO2) electrolyte and high-performance cathode materials such as La0.6Sr0.4Co0.2Fe0.8O3-δ, and improving the low-temperature oxygen ion transport in composite cathodes. It is crucial to systematically investigate the influencing mechanism of Gd-doping on conductance and thermal matching of CeO2 for high-efficiency and stable SOFC. In this paper, the physical phase, morphology and electrochemical performance of Ce1-xGdxO2-δ (x=0.1, 0.15, 0.2, 0.25) were characterized, and the thermal matching between GDC and other cell components was investigated by finite-element thermal stress calculations and cold-heat-cycling tests. The results indicate that Ce0.8Gd0.2O2-δ obtains the optimum conductivity, whether in the low temperature segment affected by the grain boundary with the space charge layer, or in the activation energy controlled medium temperature segment. Moreover, the finite-element calculation shows that the thermal stresses of the electrolyte facing the barrier layer and the barrier layer facing the cathode decrease gradually with the increase of Gd-doping. Consequently, the cell with Ce0.8Gd0.2O2-δ applied to the composite cathode and the barrier layer presents the optimal output performance of 0.87 W⋅cm-2 at 750 °C, and the cell performance decreased by only 1.15% after 50 thermal cycles between 25-800 °C. This is significant for improving the long-term operational stability of SOFC under thermal cycling conditions.

Core-shell cobalt-iron@N-doped carbon: A high-performance cathode material for lithium-sulfur batteries.

Lithium-sulfur batteries hold great promise as energy storage systems, but the shuttle effect of lithium polysulfides (LiPS) and large volume variation limit their capacity and cycle life. We have developed CoFe alloy wrapped in N-doped porous carbon spheres (e-CF@NC) with a core-shell structure through simple copolymerization and pyrolysis. The nitrogen-doped porous carbon shell provides electron and ion transport channels and more active sites for electrolyte ion adsorption. The high chemically stable carbon can limit the segregation of polysulfides, further improving the battery cycling stability. Besides, the inside CoFe alloy particles catalyze the conversion between LiPS and Li2S, speeding up reaction kinetics and reducing solvation of active sites. Consequently, lithium-sulfur batteries with e-CF@NC-2 as the cathode display a high initial specific capacity of 1146 mA h g-1 at 0.1 C, excellent rate performance (891 mA h g-1 at 1 C, 741 mA h g-1 at 2 C), and satisfied cycle stability (average capacity decay rate of 0.033% per cycle at 1 C for 300 cycles), demonstrating significant application potential.

Comparative investigation of composition, microstructure and property influences on electrocatalysis of two representative cathodes: BaCo0.4Fe0.4Zr0.1Y0.1O3-δ versus Ba0.5Sr0.5Co0.8Fe0.2O3-δ

BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY) and Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) perovskites are two representative high-performance cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Here, symmetric cell tests demonstrate that polarization resistance values of BCFZY cathode are only 0.21–0.29 times those of BSCF cathode at 740–660 °C, and 0.21–0.26 times those of BSCF cathode at the oxygen partial pressures of 1.00–0.10 atm. Distribution of relaxation times (DRT) is applied to detect individual electrode processes overlapped in impedance spectra, which finds that the dominant processes of oxygen dissociation, subsequent species transfer and reduction on BCFZY cathode are superior to those of BSCF cathode. By temperature-programmed desorption of oxygen (O2-TPD), thermal expansion coefficient (TEC) measurements, scanning electron micrograph (SEM) and energy dispersive spectra measurements, the strong oxygen combination ability with higher activation energy of oxygen desorption (Ed = 84 kJ/mol), peculiar surface state with evident nano-particle structure, more matchable TEC (19.0 × 10-6 K−1) and excellent interfacial connection with the electrolyte are observed on BCFZY cathode to account for its distinctive catalysis, as compared to BSCF cathode (Ed = 68 kJ/mol, TEC = 24.2 × 10-6 K−1).

Zwitterion Intercalated Manganese Dioxide Nanosheets as High-Performance Cathode Materials for Aqueous Zinc Ion Batteries.

In this study, a novel approach is introduced to address the challenges associated with structural instability and sluggish reaction kinetics of δ-MnO2 in aqueous zinc ion batteries. By leveraging zwitterionic betaine (Bet) for intercalation, a departure from traditional cation intercalation methods, Bet-intercalated MnO2 (MnO2-Bet) is synthesized. The positively charged quaternary ammonium groups in Bet form strong electrostatic interactions with the negatively charged oxygen atoms in the δ-MnO2 layers, enhancing structural stability and preventing layer collapse. Concurrently, the negatively charged carboxylate groups in Bet facilitate the rapid diffusion of H+/Zn2+ ions through their interactions, thus improving reaction kinetics. The resulting MnO2-Bet cathode demonstrates high specific capacity, excellent rate capability, fast reaction kinetics, and extended cycle life. This dual-function intercalation strategy significantly optimizes the electrochemical performance of δ-MnO2, establishing it as a promising cathode material for advanced aqueous zinc ion batteries.

Interlayer Space Engineering-Induced Pseudocapacitive Zinc-Ion Storage in Holey Graphene Oxide-Bearing Vertically Oriented MoS2 Nano-Wall Array Cathode for Aqueous Rechargeable Zn Metal Batteries.

Transition metal dichalcogenides, particularly MoS2, are acknowledged as a promising cathode material for aqueous rechargeable zinc metal batteries (ARZMBs). Nevertheless, its lack of hydrophilicity, poor electrical conductivity, significant restacking, and restricted interlayer spacing translate into inadequate capacity and rate performance. Herein, the unique porous structure and additional functional groups present in holey graphene oxide (hGO) are taken advantage of to dictate the vertical growth pattern of oxygen-doped MoS2 nanowalls (O-MoS2/NW) over the hGO surface. Compared to conventional graphene oxide (GO), the presence of nano-pores in hGO facilitates the homogeneous dispersion of Mo precursors and provides stronger interaction sites, promoting the uniform vertical alignment of O-MoS2/NW. The synergistic interaction between O-MoS2-NW and hGO translates to enhanced electron conductivity, efficient electrolyte penetration, enhanced interlayer spacing, reduced restacking, and enhanced surface area. As a consequence of precise control of various factors that decide the overall battery performance, a high discharge capacity (227mAhg-1 at 100mAg-1) cathode material with significantly lower charge transfer resistance (66Ω) compared to pristine O-MoS2 (153Ω) is developed. These findings underscore the potential of hGO as a multifunctional platform for nanoengineering high-performance cathode materials for the next generation of efficient and durable ARZMBs.

Exploring the Enhanced Zinc Storage Performance of α-MnSe Polyhedral Microspheres and H+/Zn2+ Co-Insertion Mechanism.

The newly emerged Mn-based selenides as cathodes for aqueous Zn-ion batteries (ZIBs) have drawn researchers' interest because of their lower electronegativity and better electronic conductivity compared with the corresponding Mn-based oxides. Nevertheless, the energy storage mechanism of Mn-based selenides still needs to be further clarified. Herein, the MnSe/Se and MnSe polyhedral microspheres are reported as cathodes for ZIBs, and the MnSe cathode achieves significantly enhanced specific capacity, rate performance, and cycling stability. In-depth kinetic analysis confirms that the MnSe cathode presents better kinetic behavior and density functional theory (DFT) calculations verify the fast diffusion kinetics of the MnSe cathode. More importantly, systematic ex situ characterizations reveal that the microstructured MnSe can exist stably during the charge-discharge process and store energy with H+/Zn2+ co-insertion mechanism, which is greatly different from the phase transformation of the nanostructured α-MnSe reported in the literature. Additionally, it is verified that the different types of separators exhibit remarkably different zinc storage performance of the MnSe cathode. This study not only offers a good guidance for developing high-performance ZIBs Mn-based cathode materials and explores the effect of separators on the zinc storage performance, but also provides new insights into the energy storage mechanism of the MnSe cathode.

In-situ TiO2/reduced graphene oxide double-coated LiNi0.5Co0.2Mn0.3O2 microspheres as high-performance Li-ion cathode materials

LiNi0.5Co0.2Mn0.3O2(NCM) layered materials have high energy density and large power density but also exhibit obvious capacity fading and voltage decay during the cycle. A rational surface modification design is reported in this work to address these problems. Herein, tetrabutyl titanate (TBOT) was decomposed into TiO2 by hydrolysis-condensation reaction and high-temperature calcination, thus a homogeneous coating was generated on the surface of NCM. The coating layer of TiO2 stabilizes the crystal structure. Furthermore, rGO and reduced metal (Ni, Co, Ti) would be wrapped on the surface as a highly conductive second coating, which could provide a rapid electron conduction pathway. The dual surface-modified cathode shows an outstanding discharge capacity of 163.4 mAh g−1 at 0.2 C and 120 mAh g−1 at 10 C. This dual coating strategy provides valuable insights for further study on the modification mechanisms of other layered cathode materials.

Ca/Li Synergetic-Doped Na0.67Ni0.33Mn0.67O2 to Realize P2-O2 Phase Transition Suppression for High-Performance Sodium-Ion Batteries.

P2-type layered transition metal oxide Na0.67Ni0.33Mn0.67O2 is considered as a promising cathode for advanced sodium-ion batteries due to its high theoretical specific capacity. However, the P2-type cathode suffers severe P2-O2 phase transition during cycling process, resulting unsatisfactory cyclic stability and rate capability. Herein, a Ca/Li co-doped P2-type Na0.62Ca0.05Ni0.33Mn0.57Li0.10O2 (NCNMLO) cathode material was synthesized through a simple sol-gel method. With the synergistic effect of Ca-doping at Na sites and Li substitution at transition metal (TM) sites, the cathode achieves an excellent electrochemical performance due to the inhibited P2-O2 phase transition and improved ion diffusion with Na+/vacancy disordering arrangement. The NCNMLO cathode exhibits a good cyclic stability with 70.8% of capacity retention at 1 C after 200 cycles and excellent rate capability with 40.1 mAh g-1 at 20 C. The dual sites doping strategy provides an effective and simple approach for designing high-performance layered oxide cathode materials for sodium-ion batteries.