Desired crystal oriented LiFePO4 nanoplatelets in situ anchored on a graphene cross-linked conductive network for fast lithium storage

Reduced Graphene Oxide Coating LiFePO4 Composite Cathodes for Advanced Lithium-Ion Battery Applications

Recently, the application of LiFePO4 (LFP) batteries in electric vehicles has attracted extensive attention from researchers. This work presents a composite of LFP particles trapped in reduced graphene oxide (rGO) nanosheets obtained through the high-temperature reduction strategy. The obtained LiFePO4/rGO composites indicate spherical morphology and uniform particles. As to the structure mode of the composite, LFP distributes in the interlayer structure of rGO, and the rGO evenly covers the surface of the particles. The LFP/rGO cathodes demonstrate a reversible specific capacity of 165 mA h g-1 and high coulombic efficiency at 0.2 C, excellent rate capacity (up to 10 C), outstanding long-term cycling stability (98%) after 1000 cycles at 5 C. The combined high electron conductivity of the layered rGO coating and uniform LFP particles contribute to the remarkable electrochemical performance of the LFP/rGO composite. The unique LFP/rGO cathode provides a potential application in high-power lithium-ion batteries.

Controlled Hydrothermal/Solvothermal Synthesis of High-Performance LiFePO4 for Li-Ion Batteries

The sluggish Li-ion diffusivity in LiFePO₄ , a famous cathode material, relies heavily on the employment of a broad spectrum of modifications to accelerate the slow kinetics, including size and orientation control, coating with electron-conducting layer, aliovalent ion doping, and defect control. These strategies are generally implemented by employing the hydrothermal/solvothermal synthesis, as reflected by the hundreds of publications on hydrothermal/solvothermal synthesis in recent years. However, LiFePO₄ is far from the level of controllable preparation, due to the lack of the understanding of the relations between the synthesis condition and the nucleation-and-growth of LiFePO₄ . In this paper, the recent progress in controlled hydrothermal/solvothermal synthesis of LiFePO₄ is first summarized, before an insight into the relations between the synthesis condition and the nucleation-and-growth of LiFePO₄ is obtained. Thereafter, a review over surface decoration, lattice substitution, and defect control is provided. Moreover, new research directions and future trends are also discussed.

Adjusting the Valence State of Vanadium in VO2 (B) by Extracting Oxygen Anions for High-Performance Aqueous Zinc-Ion Batteries

VO₂ generally has a higher theoretical capacity and layered structure suitable for the intercalation/extraction of zinc ions. However, Zn²⁺ ions with high charge density interact with the crystal lattice and limit further improvement in electrochemical performance. Defect engineering is a potential modification method with very promising application prospects, but the established procedures for preparing defects are complicated. In this study, VO_2-x (B) with oxygen deficiency is prepared by a simple solution reaction with NaBH₄ . The presence of oxygen deficiencies is confirmed by positron annihilation lifetime spectroscopy, UV/Vis absorbance spectroscopy and others. Owing to the presence of oxygen defects, the aqueous Zn/VO_2-x (B) battery exhibits improved specific capacity, excellent reversibility, and structural stability. Ex situ characterization techniques are employed to demonstrate the reversible insertion-extraction mechanism of Zn²⁺ ions from and into the host material. In addition, the Zn/VO_2-x (B) batteries still exhibit considerable electrochemical performance, even with high-loading electrodes (about 4 mg cm^-2 ).

A high-performance asymmetric supercapacitor electrode based on a three-dimensional ZnMoO4/CoO nanohybrid on nickel foam

A two-step hydrothermal route was employed to fabricate a ZnMoO₄/CoO nanohybrid supported on Ni foam. The ZnMoO₄/CoO nanohybrid shows a three-dimensional criss-crossed structure. The specific surface area is enhanced from 45 m² g^-1 of ZnMoO₄ to 67 m² g^-1 of the ZnMoO₄/CoO nanohybrid. Furthermore, the existence of electroactive CoO is in favor of reducing the charge transport resistance. The ZnMoO₄/CoO nanohybrid electrode possesses a high capacitance of 4.47 F cm^-2 at 2 mA cm^-2, which is much higher than those of ZnMoO₄ (1.07 F cm^-2) and CoO (2.47 F cm^-2). The ZnMoO₄/CoO nanohybrid electrode also exhibits an ultrahigh cycling stability with 100.5% capacitance retention after 5000 cycles at 20 mA cm^-2. In addition, an asymmetric all-solid-state supercapacitor was assembled using the ZnMoO₄/CoO nanohybrid as the positive electrode and exfoliated graphite carbon paper as the negative electrode. The asymmetric supercapacitor exhibits a superior energy density of 58.6 W h kg^-1 at a power density of 800 W kg^-1 and a considerable cycling stability with 81.8% capacitance retention after 5000 cycles at 5 A g^-1. The ZnMoO₄/CoO nanohybrid demonstrates its tremendous advantages and possibilities as a positive electrode material in energy storage applications. Moreover, for a better understanding of the electrochemical behavior, a combined study of experimental measurements and density functional theory calculations is also applied to illustrate the high-performance of the ZnMoO₄/CoO nanohybrid.

Metal-organic framework derived 3D graphene decorated NaTi2(PO4)3 for fast Na-ion storage

NASCION-type materials featuring super ionic conductivity are of considerable interest for energy storage in sodium ion batteries. However, the issue of inherent poor electronic conductivity of these materials represents a fundamental limitation in their utilization as battery electrodes. Here, for the first time, we develop a facile strategy for the synthesis of NASICON-type NaTi2(PO4)3/reduced graphene oxide (NTP-rGO) Na-ion anode materials from three-dimensional (3D) metal-organic frameworks (MOFs). The selected MOF serves as an in situ etching template for the titanium resource, and importantly, endows the materials with structure-directing properties for the self-assembly of graphene oxide (GO) through a one-step solvothermal process. Through the subsequent carbonization, an rGO decorated NTP architecture is obtained, which offers fast electron transfer and improved Na+ ion accessibility to active sites. Benefiting from its unique structural merits, the NTP-rGO exhibits improved sodium storage properties in terms of high capacity, excellent rate performance and good cycling life. We believe that the findings of this work provide new opportunities to design high performance NASICON-type materials for energy storage.

Stabilizing the structure of LiMn0.5Fe0.5PO4via the formation of concentration-gradient hollow spheres with Fe-rich surfaces

LiMn_xFe_1-xPO₄ (LMFP) has attracted extensive interest owing to its high safety and appropriate redox potential. Nevertheless, its poor electrochemical kinetics and structural instability, depending on its manganese content, are still limiting its further application. Herein, we realize a concentration-gradient LiMn_0.5Fe_0.5PO₄ hollow sphere cathode material with a carbon coating (HCG-LMFP/C) by a facile and controllable two-step solvothermal approach. On the one hand, the porous hollow architecture can sustain excellent structural stabilization against the volume changes that occur during repeated Li⁺ intercalation/deintercalation. On the other hand, the unique concentration-gradient structure with its Fe-rich surface can not only relieve interface deterioration and improve the ionic/electric conductivity due to the active nature of LiFePO₄, but also guarantees the chemical stability of the LMFP against electrolyte attack and remarkably reduces Mn dissolution, even at elevated temperature. Therefore, the obtained concentration-gradient HCG-LMFP/C cathode shows improved high-rate performance (111 and 78 mA h g^-1 at 20 and 60C rates, respectively) and excellent capacity retention (96% after 1000 cycles at the 10C rate) as well as outstanding temperature tolerance (over a temperature range from 40 °C to -10 °C). More importantly, the present gradient strategy opens up a new window for designing high-performance and stable olivine cathodes, which could also be compatible with many other energy-storage materials for various applications.

ReS2-Based electrode materials for alkali-metal ion batteries

In this review, we summarize the recent progress on ReS₂ as an electrode for alkali-metal ion batteries, mainly focusing on the synthesis method, structures, reaction mechanism, and the corresponding electrochemical performance. Additionally, the perspective and challenges of ReS₂ electrodes are also discussed.

Olivine Positive Electrodes for Li-Ion Batteries: Status and Perspectives

Among the compounds of the olivine family, LiMPO4 with M = Fe, Mn, Ni, or Co, only LiFePO4 is currently used as the active element of positive electrodes in lithium-ion batteries. However, intensive research devoted to other elements of the family has recently been successful in significantly improving their electrochemical performance, so that some of them are now promising for application in the battery industry and outperform LiFePO4 in terms of energy density, a key parameter for use in electric vehicles in particular. The purpose of this review is to acknowledge the current state of the art and the progress that has been made recently on all the elements of the family and their solid solutions. We also discuss the results from the perspective of their potential application in the industry of Li-ion batteries.

A rationally assembled graphene nanoribbon/graphene framework for high volumetric energy and power density Li-ion batteries

High volumetric energy and power densities are crucial for Li-ion batteries, which are however hindered by the loose structure and/or insufficient conductivity of conventional electrode laminates. Herein, an efficiently conductive framework of graphene nanoribbons (GNRs) and graphene (G) is rationally constructed to wrap LiFePO4 (LFP) into a binder-free dense electrode by a coupling technique of spray deposition and vacuum filtration. The spray ensures a uniform mixing of LFP, G and GNRs, meanwhile the vacuum filtration leads to a dense packing of the mixture. With only 2 wt% of G and GNRs, the LFP/GNR/G electrode delivers a high rate capability and a stable (dis)charge cycling performance under high LFP loading conditions. Moreover, the dense LFP/GNR/G electrode exhibits superior volumetric properties among all the reported LFP electrodes on the basis of the entire electrode volume, including a Li storage capacity of 318 A h L-1, an energy density of 1020 W h L-1 and a power density of 5.1 kW L-1 at 5C rate. This unique assembly strategy and the electrode structure pave a new way for high-volumetric-performance batteries.

A LiFePO4/Li2Sn hybrid system with enhanced Li-ion storage performance

A LiFePO₄/Li₂S_n hybrid system was designed using a LiFePO₄ cathode and a Li₂S_n-added electrolyte to improve the Li-ion storage performance.

A novel 3D POMOF based on Wells–Dawson arsenomolybdates with excellent photocatalytic and lithium-ion battery performance

A novel 3D POMOF based on Wells–Dawson arsenomolybdates exhibits fluorescence property and efficient and stable photocatalytic activity for MB and RhB under UV irradiation and has also been evaluated as the anode material for LIBs.

Improved rate capability and cycling stability of bicontinuous hierarchical mesoporous LiFePO4/C microbelts for lithium-ion batteries

Bicontinuous hierarchical mesoporous LiFePO₄/C microbelts have been synthesized using a simple dual-solvent electrospinning method for the first time. The sample exhibits a high reversible capacity (153 mA h g⁻¹ at 0.5C), and an excellent high rate cycling performance.

Cu3P/RGO Nanocomposite as a New Anode for Lithium-Ion Batteries

Cu₃P/reduced graphene oxide (Cu₃P/RGO) nanocomposite was successfully synthesized by a facile one-pot method as an advanced anode material for high-performance lithium-ion batteries. Cu₃P nanostructures with a polyhedral shape with the mean diameter (80–100 nm) were homogeneously anchored on the surface of RGO. The flexible RGO sheets acted as elastic buffering layer which not only reduced the volume change, but also prevented the aggregation of Cu₃P nanostructures, the cracking and crumbing of electrodes. On the other hand, the presence of Cu₃P nanostructures could also avoid the agglomeration of RGO sheets and retain their highly active surface area. Therefore, as an advanced anode material for high-performance lithium-ion batteries, the as-prepared Cu₃P/RGO exhibited high capacity of 756.15 mAhg⁻¹ at the current density 500 mAg⁻¹ after 80 cycles, superior cyclic stability and good rate capability.

Template-free synthesis of highly porous V2O5 cuboids with enhanced performance for lithium ion batteries

Highly porous hierarchical V2O5 cuboids have been synthesized by a template-free PVP-assisted polyxol method and the formation mechanism is studied. The cuboids are assembled from numerous mesoporous nanoplates and the preferred orientation of each single nanoplate exposes the 〈110〉 facets, facilitating lithium-ion diffusion by offering a prior channel. This material exhibits a high capacity of 143 mA h g(-1), high rate capacity of 10 C and long life cycling performance up to 1000 cycles. The excellent electrochemical performance of V2O5 cuboid electrodes is due to its unique porous cuboid morphology and optimized structural stability upon cycling. This research provides an effective route to the construction of complex porous architectures assembled from nanocrystals through a surfactant-assisted synthesis method.

Li3V2(PO4)3 as a cathode additive for the over-discharge protection of lithium ion batteries

LVP was added to LCO through a “layer to layer” mode to make a composite cathode and to reduce the potential of LCO during the over-discharge process.

Facile controlled synthesis of a hierarchical porous nanocoral-like Co3S4 electrode for high-performance supercapacitors

In this work, a hierarchical porous coral-like Co₃S₄ electrode is synthesized by a facile one-step hydrothermal approach showing high-performance as a supercapacitor.

A facile hydrothermal synthesis of a reduced graphene oxide modified cobalt disulfide composite electrode for high-performance supercapacitors

In this study, a 3D reduced graphene oxide modified CoS₂ composite electrode (CoS₂/RGO) is synthesized by a facile hydrothermal approach.

Recent progress in hybrid cathode materials for lithium ion batteries

Various binary composite cathode materials for lithium ion batteries are summarized and discussed.

Carbon nanotube decorated NaTi2(PO4)3/C nanocomposite for a high-rate and low-temperature sodium-ion battery anode

NTP/C–CNTs with CNT decorated NTP/C nanoparticles enhance the electrolyte infiltration and provide fast transport pathways for electrons to achieve high-rate capability and low-temperature performance.

Controlled growth of silver nanoparticles on carbon fibers for reinforcement of both tensile and interfacial strength

We have developed an electro-chemical deposition approach to synthesize various structures of Ag NPs on carbon fibers. This improved both the tensile strength and the interfacial property as much as 57.2% and 27.2%, respectively.