High-performance Cathode Materials Research Articles

Highly reversible transition metal migration in superstructure-free Li-rich oxide boosting voltage stability and redox symmetry

The further practical applications of Li-rich layered oxides are impeded by voltage decay and redox asymmetry, which are closely related to the structural degradation involving irreversible transition metal migration. It has been demonstrated that the superstructure ordering in O2-type materials can effectively suppress voltage decay and redox asymmetry. Herein, we elucidate that the absence of this superstructure ordering arrangement in a Ru-based O2-type oxide can still facilitate the highly reversible transition metal migration. We certify that Ru in superstructure-free O2-type structure can unlock a quite different migration path from Mn in mostly studied cases. The highly reversible migration of Ru helps the cathode maintain the structural robustness, thus realizing terrific capacity retention with neglectable voltage decay and inhibited oxygen redox asymmetry. We untie the knot that the absence of superstructure ordering fails to enable a high-performance Li-rich layered oxide cathode material with suppressed voltage decay and redox asymmetry.

Construction of a bi-continuous charge transport network towards high-performance vanadium-based phosphate cathode materials for potassium ion batteries

As one class of most promising cathode materials for potassium ion batteries (KIBs), polyanionic compounds still suffer from unsatisfactory effective capacity and rate performance due to their poor intrinsic electronic conductivity. In this paper, nanoscale K3V3(PO4)4 (KVP) particles with a bi-continuous charge transport network (denote as KVP-S) are designed and prepared. Carbon nanotubes (CNTs) play a crucial role in this design, not only effectively inhibiting the aggregation and growth of particles, but also providing a three-dimensional (3D) electron conductive network. Benefiting from the advantages of nanoscale particle size and bi-continuous charge transport network, the KVP-S electrode exhibits a high capacity (118mAh g−1 at 20 mA g−1), outstanding rate performance (102 mAh g−1 at 0.5 C; 66 mAh g−1 at 5 C) and excellent cycling stability (94 % retention after 50 cycles at 1 C). Even at a higher rate of 5 C, it still maintains a high capacity retention of 92 % after 300 cycles. More importantly, the capacity can maintain 80 mAh g−1 at 1 C when the mass loading is extended to 4 mg cm−2, In addition, in-situ X-ray diffraction (XRD) and ex-situ X-ray photoelectron spectroscopy (XPS) analyses reveal that the potassium storage mechanism of KVP-S is two single-phase solid solution reactions, involving V2+/V3+/V4+ three-electron redox conversions with a total volume change of 5.5 %. This study provides a new way to rationally design nanoscale particle electrodes with highly conductive charge transport networks.

Hydrophobic Two-Dimensional Layered Superstructure of a Polyoxometalate Cluster as the Cathode Material for Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries hold promise for sustainable energy storage, yet challenges in finding high-performance cathode materials persist. Polyoxovanadates (POVs) are emerging as potential candidates due to their structural diversity and robust redox activity. Despite their potential, issues like dissolution in electrolytes, structural degradation, and byproduct accumulation persist. This work introduces a POV-based hydrophobic two-dimensional (2D) layered superstructure that addresses these challenges. The hydrophobic nature minimizes POV dissolution, enhancing structural stability and inhibiting phase transitions during cycling. The 2D arrangement ensures a larger surface area and improved electronic conductivity, resulting in faster kinetics and higher specific capacity. The superstructure demonstrates improved cycle life and an increased operating voltage, marking a significant advancement in POV-based cathode materials for aqueous zinc-ion batteries.

Laser-Scribed Battery Electrodes for Ultrafast Zinc-Ion Energy Storage.

Aqueous Zn batteries are promising for large-scale energy storage applications but are plagued by the lack of high-performance cathode materials that enable high specific capacity, ultrafast charging, and outstanding cycling stability. In this work, we design a laser-scribed nano-vanadium oxide (LNVO) cathode that can simultaneously achieve these properties. Our material stores charge through Faradaic redox reactions on/near the surface at fast rates owing to the small grain size (2-6nm) of vanadium oxide and interpenetrating three-dimensional (3D) graphene network, displaying a surface-controlled capacity contribution (90%-98%). Multiple characterization techniques unambiguously reveal that zinc and hydronium ions co-insert with minimal LNVO lattice change upon cycling. As a result, we demonstrate that a high specific capacity of 553 mAh g-1 can be achieved by the LNVO/Zn system at 0.1 A g-1 , and an impressive 264 mAh g-1 capacity can be retained at 100 A g-1 with a 10 s charge/discharge cycle, showing excellent rate capability. The LNVO/Zn is also capable of reaching >90% capacity retention after 3,000 cycles at a high rate of 30 A g-1, as well as achieving both high energy (369Wh kg-1) and power densities (56,306W kg-1). Moreover, the LNVO cathode retains its excellent cycling performance when integrated into quasi-solid-state pouch cells, further demonstrating mechanical stability and its potential for practical application in wearable and grid-scale applications. This article is protected by copyright. All rights reserved.

Constructing Cu9S5@CuSe heterostructures under microwave irradiation for rechargeable magnesium batteries

Copper chalcogenides are believed as the prospective cathode materials for rechargeable magnesium batteries. However, their practical application is seriously restricted by slow diffusion and reaction kinetics due to the large charge/radius ratio of divalent Mg2+ ions. Herein, a simple two-step microwave-assisted synthesis method is rationally developed to construct Cu9S5@CuSe heterostructures as the capable cathode materials for rechargeable magnesium batteries. Two-dimensional CuSe nanosheets are vertically grown on the surface of single-crystal Cu9S5 substrate through selenation reaction under microwave irradiation to form the mixed-dimensional heterostructures. Electrochemical measurements reveal that the as-synthesized Cu9S5@CuSe heterostructures show high reversible capacity of 240 mAh g−1 and good long-term cyclic stability with approximate 0.013 % capacity decay per cycle at 500 mA g−1 within 1000 cycles. Furthermore, the obviously enhanced rate capability can be achieved in comparison with that of single-crystal Cu9S5 substrate and CuSe nanoparticles. Ex-situ X-ray photoelectron spectroscopy and X-ray diffraction characterizations reveal favourable electrochemical conversion reaction over the Cu9S5@CuSe heterostructure cathode. The superior electrochemical properties are attributed to the optimized diffusion kinetics within the unique heterostructure. This research offers a valuable strategy to develop high-performance cathode materials with favourable kinetics for magnesium batteries.

FeOCl/polyaniline nanosheets as high-performance cathode for chloride ion battery

Chloride-ion batteries (CIBs) are potentially low-cost and safe alternatives to lithium-ion batteries. As a promising cathode material for CIBs, iron oxychloride shows high theoretical capacity and rich resources. However, the huge volumetric expansion and shrinkage issue for the phase transition result in pulverization of FeOCl particles and structural collapse of electrodes. Herein, FeOCl/polyaniline nanosheets with expanded laminated structure, polyaniline-coated, and high chlorine content have been developed as a high-performance cathode material for CIBs. It was found that the slow in situ intercalation polymerization of aniline into the layer of FeOCl nanosheets results in an irreversible loss of chlorine content, which is unfavorable for high discharge capacity. After being completely intercalated, adding an oxidizing agent is conducive to the polymerization of aniline and keeping the chlorine content stable. As a result, the optimized FeOCl/polyaniline cathode exhibits the highest discharge capacity of 187 mAh·g−1, and a capacity retention of 85.0 % after 50 cycles. Polyaniline was maintained in the doped state and acted as a volume buffering matrix during the cycles.

Topochemical behavior of ferrocene embedded in V2O5·nH2O with weak hydrogen bonding enhancing ammonium-ion storage

Aqueous ammonium ion batteries (AAIBs) are garnering increasing attention due to their utilization of abundant resources, cost-effectiveness, safety, and unique energy storage mechanism. The pursuit of high-performance cathode materials has become a pressing issue. In this study, we propose and synthesize ferrocene-embedded hydrated vanadium pentoxide (Fer/VOH) for implementation in AAIBs. The inclusion of ferrocene serves to expand the interlayer spacing, mitigate interlayer forces, and introduce the electron-rich environment characteristic of ferrocene. This augmentation facilitates the creation of additional oxygen vacancies, substantially enhancing the capacity and efficiency of ammonium ion storage. Notably, our investigation reveals that the incorporation of ferrocene attenuates the hydrogen bonding interactions associated with ammonium ions, rendering them more amenable to the interlayer embedding and release processes. Building upon these advantages, Fer/VOH exhibits a specific capacity of 313 mAh/g at a current density of 0.2 A/g, representing the highest reported performance among vanadium oxides utilized in AAIBs to date. Even after 2000 charge/discharge cycles at a current density of 2 A/g, Fer/VOH maintains a reversible specific capacity of 89 mAh/g, with a capacity retention rate of 54.8%. This study confirms the viability of Fer/VOH as a cathode material for AAIBs and offers a novel approach to enhancing the electrical conductivity and diminishing the hydrogen bonding forces in vanadium oxide intercalation through the embedding of electron-rich species and positronic groups.

Reversible Deposition/Dissolution of Double Hydroxides to Modulate Electrolyte pH Enabling High-Performance Aqueous Zinc-Ion Batteries.

Vanadium oxide has been extensively studied as a host of zinc ion intercalation but still suffers from low conductivity, dissolution, and byproduct accumulation during cycling. Here, we hydrothermally synthesize the VO2@MXene Ti3C2 (MV) composite and find that in the MV//3 M Zn(CF3SO3)2//Zn system, the double hydroxide Zn12(CF3SO3)9(OH)15·nH2O (ZCOH) uniformly covers VO2 during the charging process and dissolves reversibly during the discharge process. In situ X-ray diffraction of the MV combined with in situ pH measurements reveals that ZCOH acts as a pH buffer during cycling, which is beneficial to the cycling stability of batteries. And the theoretical calculation indicates that the decomposition energy required by ZCOH on the MV surface is lower than that on pure VO2, which is more conducive to ZCOH dissolution. The coin battery exhibits high-rate performance of 65.1% capacity retention at a current density of 15 A g-1 (compared to 0.6 A g-1) and a long cycling life of 20,000 cycles with a capacity retention of 80.7%. For a 22.4 mA h soft-packaged battery, its capacity remains at 72.1% after 2000 cycles. This work demonstrates the active role of ZCOH in the electrochemical process of VO2 and provides a new perspective for exploiting this mechanism to develop high-performance aqueous zinc-ion battery vanadium oxide cathode materials.

Preparation of lithium ferromanganese phosphate by non-stoichiometric strategy

LixFexMn1-xPO4 exhibits low production costs, environmental friendliness, high energy density, thermal stability, and cycling stability in lithium-ion batteries (LIBs), presenting broad application prospects. Furthermore, studies have shown that adopting a non-stoichiometric ratio strategy can reduce particle size, decrease anti-site defects, and generate a conductive impurity phase on the material surface. This leads to an enhancement in the electrochemical performance of the material, making it an effective approach to achieving high-performance olivine-type cathode materials. In this study, three materials were successfully prepared using the solid-phase method: Li1.05Fe0.5Mn0.475PO4/C, Li1.05Fe0.5Mn0.5PO4/C, and Li1.05Fe0.475Mn0.5PO4/C. The physical properties of the materials were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The electrochemical performance including specific capacity, rate performance, and cycling performance were studied through charge-discharge tests, with Li1.05Fe0.5Mn0.475PO4/C exhibiting the best specific capacity at all rates. At rates of 0.1 C, 0.5 C, 1 C, 2 C, and 5 C, its average reversible specific capacities were 143.5, 129.5, 122.1, 112.8, and 97.3 mAh·g−1, respectively. Furthermore, differences in electrochemical performance of three materials were discussed in detail through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).

Towards beneficial transformation of aluminum impurity for cathode material regeneration from spent lithium-ion batteries: In-situ Al doping for high-performance LiNi0.9Co0.05Mn0.05O2

Aluminum (Al) from current collector is a quite important impurity element affecting the regenerated cathode materials from spent lithium-ion batteries (LIBs). Currently, Al in the leaching solution is difficult to be removed in depth without causing loss of nickel or cobalt. Herein, the quantitative relationship between Al in the leaching solution and regenerated precursors and cathode materials is investigated, and the effects of Al impurity on the macromorphology and microstructure of the materials is revealed. It suggests that Al introduction suppresses the ordered growth of precursors and further leads to disordered grain morphology of regenerated cathode materials, twisting Li+ diffusion pathway. Meanwhile, Al doping could widen LiO6 layer channel, synchronously stabilize layered structure and interfacial properties. Thus, by balancing the effects between morphology and lattice, Al-doped LiNi0.9Co0.05Mn0.05O2 with superior cycling stability (95.1 % capacity retention efficiency after 200 cycles at 1 C) and rate performance (101.8 mAh g−1 discharge capacity at 10 C) is regenerated when Al concentration in the leaching solution is controlled at 1.08 g/L. This study transforms the harmful Al impurity into a beneficial component, and provides a favorable in-situ Al-doping strategy for regenerating high-performance cathode materials from spent LIBs.

Preparation of high-performance multiphase heterostructures IT-SOFC cathode materials by Pr-induced in situ assembly

Here, in situ assembly in La0.6Sr0.4Co0.2Fe0.8O3-δ and CoFe2O4 composite (LSCFC) cathode was induced by Pr to form La0.6Sr0.4CoxFeyO3-δ/PrCoO3/Co3O4/PrO2 (LSCFC-PI) multiphase heterostructures. The surface of LSCFC-PI forms uniform nanoparticles, and the unique core-shell structure prevents Sr segregation, thereby enhancing CO2 tolerance and increasing oxygen reduction reaction (ORR) active sites. Furthermore, compared with LSCFC, LSCFC-PI increases the oxygen vacancy content of the cathode due to the existence of multiphase heterostructure, improves the ORR kinetics, and the conductivity is also greatly improved. The peak power density (PPD) of LSCFC-PI as a single-cell cathode at 700 ℃ reached 1.51 W cm−2, which was 2.65 times higher than that of LSCFC's 0.57 W cm−2, and in the long-term stability test at a constant voltage ∼0.8 V for 100 hours, showing excellent stability. In situ assembly of multiphase heterostructures is expected to become a new strategy for developing high-performance IT-SOFC cathodes.

Freestanding Ammonium Vanadate Composite Cathodes with Lattice Self-Regulation and Ion Exchange for Long-Lasting Ca-Ion Batteries.

Calcium-ion batteries (CIBs) have emerged as a promising alternative for electrochemical energy storage. The lack of high-performance cathode materials severely limits the development of CIBs. Vanadium oxides are particularly attractive as cathode materials for CIBs, and preinsertion chemistry is often used to improve their calcium storage performance. However, the room temperature cycling lifespan of vanadium oxides in organic electrolytes still falls short of 1000 cycles. Here, based on preinsertion chemistry, the cycling life of vanadium oxides is further improved by integrated electrode and electrolyte engineering. Utilizing a tailored Ca electrolyte, the constructed freestanding (NH4)2V6O16·1.35H2O@graphene oxide@carbon nanotube (NHVO-H@GO@CNT) composite cathode achieves a 305 mAh g-1 high capacity and 10000 cycles record-long life. Additionally, for the first time, a Ca-ion hybrid capacitor full cell is assembled and delivers a capacity of 62.8 mAh g-1. The calcium storage mechanism of NHVO-H@GO@CNT based on a two-phase reaction and the exchange of NH4 + and Ca2+ during cycling are revealed. The lattice self-regulation of V─O layers is observed and the layered vanadium oxides with Ca2+ pillars formed by ion exchange exhibit higher capacity. This work provides novel strategies to enhance the calcium storage performance of vanadium oxides via integrated structural design of electrodes and electrolyte modification.

Modulating Valence Electrons and Na Occupancy in Layered Cathodes for High-Performance Na-Ion Batteries.

Na-ion batteries (NIBs) hold promise as a leading option for large-scale energy storage. However, their development faces challenges due to the lack of high-performance cathode materials. P2-type layered oxides are seen as potential cathode materials for NIBs due to higher structure stability, yet their commercialization is hindered by limited capacity and subpar phase transitions during Na extraction and insertion at high voltages. In this study, we introduce a new P2-type cathode material, Na0.76Ni0.23Li0.1Ti0.02Mn0.65O1.998F0.02 (NLTMOF), synthesized with ternary Li/Ti/F substitution. This modification of ternary Li/Ti/F substitution significantly tailors the electronic structures, increasing the number of valence electrons near the Fermi energy level. This facilitates the electronic conductivity and their involvement in charge compensation, thereby enhancing reversible capacity. Additionally, ternary doping synergistically adjusts the Na occupancy at the Na layer for favorable Na extraction without P2-O2 phase transitions even under a high voltage of 4.4 V, boosting cycling stability. As a result, NLTMOF demonstrates a reversible capacity of 110.0 and 132.2 mAh g-1 at 2-4.2 and 2-4.4 V, respectively, and maintains greatly enhanced cycling stability over long cycles. This study sheds light on the design of transition metal oxides for advanced cathode materials through the modulation of electronic structure and Na occupancy in cathode materials, thus promoting the development of NIBs.

CH3COOLi-assisted lithium source on the synthesis of high-performance single-crystal Ni-rich cathode material

CH3COOLi-assisted lithium source on the synthesis of high-performance single-crystal Ni-rich cathode material

A Feasible Dual Modification Strategy of Internal Anion Redox Chemistry and Surface Engineering on P2 Layer-Structured Cathodes in Sodium-Ion Batteries.

Boosting the anion redox reaction opens up a possibility of further capacity enhancement on transition-metal-ion redox-only layer-structured cathodes for sodium-ion batteries. To mitigate the deteriorating impact on the internal and surface structure of the cathode caused by the inevitable increase in the operation voltage, probing a solution to promote the bulk-phase crystal structure stability and surface chemistry environment to further facilitate the electrochemical performance enhancement is a key issue. A dual modification strategy of establishing an anion redox hybrid activation trigger agent inside the crystal structure in combination with surface oxide coating is successfully developed. P2-type layer structure cathode materials with Zn/Li (Na-O-Zn@Na-O-Li) anion redox hybrid triggers and a ZnO coating layer possess superior capacity and cycle performance, along with outstanding structural stability, decreased Mn-ion dissolution effect, and less crystal particle cracking during the cycling process. This study represents a facile modification solution to perform structure optimization and property enhancement toward high-performance layered structure cathode materials with anion redox features in sodium-ion batteries.

In Situ Constructed Spinel Layer Stabilized Upcycled LiCoO2 for High Performance Lithium-Ion Batteries.

With ever-increasing requirements for cathodes in the lithium-ion batteries market, an efficiency and eco-friendly upcycling regeneration strategy is imperative to meet the demand for high-performance cathode materials. Herein, a facile, direct and upcycling regeneration strategy is proposed to restore the failed LiCoO2 and enhance the stability at 4.6 V. Double effects combination of relithiation and outside surface reconstruction are simultaneously achieved via a facile solid-phase sintering method. The evolution process of the Li-supplement and grain-recrystallization is systematically investigated, and the high performance of the upcycled materials at high voltage is comprehensively demonstrated. Thanks to the favorable spinel LiCoxMn2-xO4 surface coating, the upcycled sample displays outstanding electrochemical performance, superior to the pristine cathode materials. Notably, the 1% surface-coated LiCoO2 achieves a high discharge-specific capacity of 207.9 mA h g-1 at 0.1 C and delivers excellent cyclability with 77.0% capacity retention after 300 cycles. Significantly, this in situ created spinel coating layer can be potentially utilized for recycling spent LiCoO2, thus providing a viable, promising recycling strategy insights into the upcycling of degraded cathodes.

Facile synthesis of V2O3@C nanoribbons by rapid cooling method for high-capacity zinc-ion batteries cathode

Aqueous zinc-ion batteries (ZIBs) have recently gained considerable attention due to their low price and great safety properties. However, the challenge of preparing high-performance cathode materials and developing low-cost, efficient preparation methods still demands urgent solutions. Herein, this paper proposes the use of a rapid cooling method to prepare V2O3@C cathode materials with excellent overall electrochemical performance for ZIBs. Utilizing low-cost ammonium metavanadate as the raw material and melamine as a binding agent, dispersed molecules facilitate the rapid creation of V-based nanoribbon precursors within just 1 h at a low temperature. After the annealing process, the obtained V2O3@C nanoribbons exhibit a unique structural architecture with a V2O3 covered by carbon, providing enhanced structural stability and electric conductivity. In contrast to the commercial V2O3 cathode, the V2O3@C cathode exhibits remarkably improved electrochemical characteristics, including enhanced specific capacity (41 % increase), extended cycle stability (capacity retention of 63 % after 15,000 cycles), and improved rate capability (53 % capacity retention at 10 A g−1). Additionally, the zinc storage mechanism of the V2O3@C cathode was systematically investigated. This facile synthesis method, coupled with the outstanding electrochemical performance, highlights the potential of V2O3@C cathode as a promising candidate for high-capacity cathodes in next-generation ZIBs.

Stabilizing the bulk phase and interface of layered oxide cathode through Li&B double doping

Layered oxide cathodes have attracted widespread attention due to their high-voltage and high discharge capacity. Nevertheless, the irreversible redox reactions of layered oxide cathode and decomposition of electrolyte at high-voltage greatly reduce the reversibility of the batteries. Herein, we employ a double-doping (Li&B) strategy to enhance the electrochemistry performance of the layered NaNi0.3Fe0.3Mn0.4O2 (NNFM) cathode at high voltage. It proved that the dissolution of the transition metal can be restricted by double doping, and the irreversible phase transition is mitigated even at high voltage. As a result, battery with the double-doping cathode exhibits excellent electrochemistry performance, which achieves a capacity of 175 mAh g−1 at 0.2C, maintaining a capacity retention of approximately 87.3% over 100 cycles at 1C, and demonstrates exceptional rate performance. This work presents a novel insight into the doping technique for the high-performance cathode materials and offers a general method for the high energy Na-ion batteries.

Ti-doped O3-NaNi0.5Mn0.5O2 as high-performance cathode materials for sodium-ion batteries

With favorable electrochemical activity, NaNi0.5Mn0.5O2(NNMO) has been a key cathode material in sodium-ion batteries. However, the phase-transition irreversible and kinetics sluggish issues in NaNi0.5Mn0.5O2 greatly limit its application in sodium-ion batteries. Here, various Ti-doped O3-NaNi0.5Mn0.5-xTixO2 cathode materials were fabricated via solid-phase method. The extra Ti-doping treatment effectively stabilized the transition layer of metal and enlarged the Na layer spacing, as well as suppressed the Na+/vacancy ordering. In particular, the obtained O3-NaNi0.5Mn0.46Ti0.04O2 (NNMOTi-4) exhibits initial reversible capacity of 108.6 mAh g−1 at 0.1C and remarkable 65.2% capacity retention after 100 cycles at 1C. Accordingly, this work provides a facile Ti-doping strategy to regulate the structure and electrochemical performance of layered NaxTMO2 for sodium-ion batteries.

Co-insertion of K+ and Ca2+ in vanadium oxide as high-performance aqueous zinc-ion battery cathode material

Inserting metal ions into vanadium oxides can effectively improve their electrochemical properties, and the insertion of different single metal ions into vanadium-based compounds can enhance their electrochemical performance in different ways. Moreover, the insertion of multiple metal ions into vanadium-based compounds may provide a synergistic effect. Therefore, in this work a K0.02Ca0.18V2O5·0.7H2O (KCaVOH) cathode material was obtained by co-inserting the monovalent metal ion K+ and the divalent metal ion Ca2+ into vanadium oxide through a one-step hydrothermal method. The insertion of K+ enhances the structural stability of the cathode material, while the insertion of Ca2+ increases the layer spacing between the V-O layers and improves the specific capacity of the cathode material. The co-insertion of K+ and Ca2+ effectively enhances the electrochemical performance of V2O5·1.6H2O, and the KCaVOH cathode provides a high specific capacity of 410 mAh·g−1 at 0.3 A·g−1. Moreover, the capacity still reaches 265 mAh·g−1 after 1800 cycles at 5 A·g−1. This method provides a strategy for significantly enhancing the electrochemical performance of vanadium-based cathode materials.