Long-life and high-rate Li3V2(PO4)3/C nanosphere cathode materials with three-dimensional continuous electron pathways

The bead-like Li3V2(PO4)3/NC nanofibers based on the nanocellulose from waste reed for long-life Li-ion batteries

In this work, we firstly synthesized the high-quality nanocellulose from the waste reed, a low-cost biomass, and designed the nanostructure for energy applications. We successfully constructed the bead-like Lithium vanadium phosphate/nanofiber carbon (LVP/NC) multi-structure by self-assembly based on the nanocellulose framework. During the carbonization process, the nanocellulose turn into porous carbon nanofiber into which LVP nanoparticles can be embedded to form a bead-like structure. The unique structure can endow the effective electron contacts and ions transportation. As cathode for Li ion batteries, the composite exhibits the discharge specific capacity of 131.6 mA h/g, which is close to the theoretical specific capacity. Moreover, the composites reveal an excellent long-cycle performance. At 10 C, the capacity retention is near 90 % after 1000 cycles. With the excellent performance, this bead-like composite shows great application value and the facile synthesis strategy can be used for preparing other cathode with high performance.

Going Nano with Confined Effects to Construct Pomegranate-like Cathode for High-Energy and High-Power Lithium-Ion Batteries

Pomegranate-like Li₃V₂(PO₄)₃@C (LVP@C) cathode materials are fabricated through confined effect helped by the vacuum-assisted capillary action. The performance of Li_xV₂(PO₄)₃ (x = 0-5) at an extended working voltage of 1.2-4.8 V has been studied by operando X-ray powder diffraction and hybrid functional density functional theory (DFT) calculation. The DFT calculation results suggest that Li₃V₂(PO₄)₃ can be intercalated with another two Li⁺ with a stable crystalline structure, which improves the specific capacity of LVP significantly. The cathode exhibits a specific capacity of 320 mAh g^-1 with an energy density of 736 Wh kg^-1, which is one of the best performances for intercalation cathode materials for Li-ion batteries to our knowledge. Besides, the cathode showed excellent rate capability. In the working potential of 3.0-4.8 V, it exhibits a high specific capacity of 195 mAh g^-1 at 0.2 C, and even at a high rate of 30 C, it still delivers the specific capacity of 145 mAh g^-1 with a power density of 15.93 kW kg^-1. The good performance is mainly attributed to the unique pomegranate structure, which can provide continuous three-dimensional conductive networks for fast electron and Li-ion transfer. This paper provides a new strategy for synthesizing other cathode or anode materials with high energy and power density.

High Performance and Structural Stability of K and Cl Co-Doped LiNi0.5Co0.2Mn0.3O2 Cathode Materials in 4.6 Voltage

The high energy density lithium ion batteries are being pursued because of their extensive application in electric vehicles with a large mileage and storage energy station with a long life. So, increasing the charge voltage becomes a strategy to improve the energy density. But it brings some harmful to the structural stability. In order to find the equilibrium between capacity and structure stability, the K and Cl co-doped LiNi_0.5Co_0.2Mn_0.3O₂ (NCM) cathode materials are designed based on defect theory, and prepared by solid state reaction. The structure is investigated by means of X-ray diffraction (XRD), rietveld refinements, scanning electron microscope (SEM), XPS, EDS mapping and transmission electron microscope (TEM). Electrochemical properties are measured through electrochemical impedance spectroscopy (EIS), cyclic voltammogram curves (CV), charge/discharge tests. The results of XRD, EDS mapping, and XPS show that K and Cl are successfully incorporated into the lattice of NCM cathode materials. Rietveld refinements along with TEM analysis manifest K and Cl co-doping can effectively reduce cation mixing and make the layered structure more complete. After 100 cycles at 1 C, the K and Cl co-doped NCM retains a more integrated layered structure compared to the pristine NCM. It indicates the co-doping can effectively strengthen the layer structure and suppress the phase transition to some degree during repeated charge and discharge process. Through CV curves, it can be found that K and Cl co-doping can weaken the electrode polarization and improve the electrochemical performance. Electrochemical tests show that the discharge capacity of Li_0.99K_0.01(Ni_0.5Co_0.3Mn_0.2)O_1.99Cl_0.01 (KCl-NCM) are far higher than NCM at 5 C, and capacity retention reaches 78.1% after 100 cycles at 1 C. EIS measurement indicates that doping K and Cl contributes to the better lithium ion diffusion and the lower charge transfer resistance.

Nanostructured Li3 V2 (PO4 )3 Cathodes

To further increase the energy and power densities of lithium-ion batteries (LIBs), monoclinic Li₃ V₂ (PO₄ )₃ attracts much attention. However, the intrinsic low electrical conductivity (2.4 × 10^-7 S cm^-1 ) and sluggish kinetics become major drawbacks that keep Li₃ V₂ (PO₄ )₃ away from meeting its full potential in high rate performance. Recently, significant breakthroughs in electrochemical performance (e.g., rate capability and cycling stability) have been achieved by utilizing advanced nanotechnologies. The nanostructured Li₃ V₂ (PO₄ )₃ hybrid cathodes not only improve the electrical conductivity, but also provide high electrode/electrolyte contact interfaces, favorable electron and Li⁺ transport properties, and good accommodation of strain upon Li⁺ insertion/extraction. In this Review, light is shed on recent developments in the application of 0D (nanoparticles), 1D (nanowires and nanobelts), 2D (nanoplates and nanosheets), and 3D (nanospheres) Li₃ V₂ (PO₄ )₃ for high-performance LIBs, especially highlighting their synthetic strategies and promising electrochemical properties. Finally, the future prospects of nanostructured Li₃ V₂ (PO₄ )₃ cathodes are discussed.

Phytic acid-derivative transition metal phosphides encapsulated in N,P-codoped carbon: an efficient and durable hydrogen evolution electrocatalyst in a wide pH range

Applications of highly-efficient and durable non-precious metal electrocatalysts for hydrogen evolution reaction (HER) have great potential to relieve the energy crisis. Here, we demonstrate a green method for fabrication of a number of transition metal phosphides (TMPs) by pyrolyzing melamine and self-assembled phytic acid (PA) cross-linked metal complexes. The obtained materials consisting of TMP nanoparticles (NPs) are encapsulated in N,P-codoped carbon (NPC). Among TMPs, the resultant FeP NPs encapsulated in the NPC matrix (FeP NPs@NPC) show the highest HER activity at all pH values. At a current density of 10 mA cm^-2, FeP NPs@NPC displays overpotentials of 130, 386 and 214 mV in 0.5 M H₂SO₄, 1.0 M phosphate buffer solution (PBS) and 1.0 M KOH, respectively. Additionally, the encapsulation by NPC effectively prevents FeP NPs from corrosion, exhibiting almost unfading catalytic activity after 10 h testing in acidic, neutral and basic electrolytes. More importantly, other TMPs wrapped in NPC (CoP NPs@NPC and Ni₂P NPs@NPC) can be easily obtained by this method, which also exhibit relatively high activity toward HER. Therefore, this generic synthesis strategy opens a door for unprecedented design and fabrication of novel low-cost TMP based electrocatalysts for HER and other electrochemical applications.

3D porous Li3V2(PO4)3/hard carbon composites for improving the rate performance of lithium ion batteries

A 3D porous Li₃V₂(PO₄)₃/hard carbon composite delivers a capacity of 98 mA h g⁻¹ after 1000 cycles at 10C.

Surfactant-assisted solid-state synthesis of 6LiMn0.8Fe0.2PO4·Li3V2(PO4)3/C nanocomposite for lithium-ion batteries

The nanosized 6LiMn_0.8Fe_0.2PO₄·Li₃V₂(PO₄)₃/C nanoparticles were synthesized by a facile surfactant-assisted solid-state method, exhibiting outstanding rate capability and cycling stability.

One-pot synthesis of 3D hierarchical porous Li3V2(PO4)3/C nanocomposites for high-rate and long-life lithium ion batteries

A hierarchical porous Li₃V₂(PO₄)₃/C nanocomposite with excellent cycle stability is fabricated via a simple one-pot process.

Roles of coating carbon, conductive additive and binders in lithium vanadium phosphate/reduced graphene oxide composite cathodes

Supreme high rate cycling performance can be achieved by optimizing the composition of LVP electrode.

Advanced cathode materials for lithium-ion batteries using nanoarchitectonics

In recent years, the global climate has further deteriorated because of the excessive consumption of traditional energy sources. The replacement of traditional fossil fuels with limited reserves by alternative energy sources has become one of the main strategies to alleviate the increasingly serious environmental issues. As a sustainable and promising store of renewable energy, lithium-ion batteries have replaced other types of batteries for many small-scale consumer devices. Notwithstanding their worldwide applications, it has become abundantly clear that the design and fabrication of electrode materials is urgently required to adapt to meet the growing global demand for energy and the power densities needed to make electric vehicles fully commercially viable. To dramatically enhance battery performance, further advances in materials chemistry are essential, especially in novel nanomaterials chemistry. The construction of nanostructured cathode materials by reducing particle size can boost electrochemical performance. The present review is intended to provide readers with a better understanding of the unique contribution of various nanoarchitectures to lithium-ion batteries over the last decade. Nanostructured cathode materials with different dimensions (0D, 1D, 2D, and 3D), morphologies (hollow, core-shell, etc.), and composites (mainly graphene-based composites) are highlighted, aiming to unravel the opportunities for the development of future-generation lithium-ion batteries. The advantages and challenges of nanomaterials are also addressed in this review. We hope to simulate many more extensive and insightful studies on nanoarchitectonic cathode materials for advanced lithium-ion batteries with desirable performance.

An in-situ gas chromatography investigation into the suppression of oxygen gas evolution by coated amorphous cobalt-phosphate nanoparticles on oxide electrode

The real time detection of quantitative oxygen release from the cathode is performed by in-situ Gas Chromatography as a tool to not only determine the amount of oxygen release from a lithium-ion cell but also to address the safety concerns. This in-situ gas chromatography technique monitoring the gas evolution during electrochemical reaction presents opportunities to clearly understand the effect of surface modification and predict on the cathode stability. The oxide cathode, 0.5Li₂MnO₃∙0.5LiNi_0.4Co_0.2Mn_0.4O₂, surface modified by amorphous cobalt-phosphate nanoparticles (a-CoPO₄) is prepared by a simple co-precipitation reaction followed by a mild heat treatment. The presence of a 40 nm thick a-CoPO₄ coating layer wrapping the oxide powders is confirmed by electron microscopy. The electrochemical measurements reveal that the a-CoPO₄ coated overlithiated layered oxide cathode shows better performances than the pristine counterpart. The enhanced performance of the surface modified oxide is attributed to the uniformly coated Co-P-O layer facilitating the suppression of O₂ evolution and offering potential lithium host sites. Further, the formation of a stable SEI layer protecting electrolyte decomposition also contributes to enhanced stabilities with lesser voltage decay. The in-situ gas chromatography technique to study electrode safety offers opportunities to investigate the safety issues of a variety of nanostructured electrodes.

Highly Efficient Storage of Pulse Energy Produced by Triboelectric Nanogenerator in Li3V2(PO4)3/C Cathode Li-Ion Batteries

Triboelectric nanogenerator (TENG) has been considered as a new type of energy harvesting technology, which employs the coupling effects of triboelectrification and electrostatic induction. One key factor having limited its application is the energy storage. In this work, a high performance Li3V2(PO4)3/C material synthesized by low-cost hydrothermal method followed with subsequent annealing treatment was studied to efficiently store the power generated by a radial-arrayed rotary TENG. Not only does the Li3V2(PO4)3/C exhibit a discharge capacity of 128 mAh g(-1) at 1 C with excellent cyclic stability (capacity retention is 90% after 1000 cycles at a rate of 5 C) in Li-ion battery, but also shows outstanding energy conversion efficiency (83.4%) compared with the most popular cathodic materials: LiFePO4 (74.4%), LiCoO2 (66.1%), and LiMn2O4 (73.6%) when it was charged by high frequency and large current electricity directly from by TENG.

A carbon coated NASICON structure material embedded in porous carbon enabling superior sodium storage performance: NaTi2(PO4)3 as an example

Sodium super ion conductor (NASICON) type structure materials (e.g. Na3V2(PO4)3, NaTi2(PO4)3) have been considered as promising electrode materials for sodium-ion batteries (NIBs). However, the inherent poor electronic conductivity of the NASICON type structure materials owing to their poor electronic conductivity of phosphates leads to poor cyclability and rate capability. Here, we develop a general strategy to achieve high rate capability and long cycle life by preparing "double carbon coating" NASICON NaTi2(PO4)3 using a soft-chemical method. The obtained carbon-coated NaTi2(PO4)3 within the porous carbon matrix (denoted as NTP@C@PC) imparts a reversible capability of 103 mA h g(-1) at 5 C after 5000 cycles and a rate capability of 64 mA h g(-1) at 50 C for sodium storage. The high capacity, stable cyclability and excellent rate capability of the NTP@C@PC are attributed to the advantages of the special structure: the fast Na(+)/e(-) transfer in the nanocomposites, large surface area and mesoporous nature of the 3D porous carbon matrix that facilitate the electrolyte to soak in, an intimate interaction between the particles and the carbon matrix. In addition, the 3D porous carbon matrix could effectively accommodate the volume variation during a repeated sodiation/desodiation process.

Carbon-armored Co9S8 nanoparticles as all-pH efficient and durable H2-evolving electrocatalysts

Splitting water to produce hydrogen requires the development of non-noble-metal catalysts that are able to make this reaction feasible and energy efficient. Herein, we show that cobalt pentlandite (Co9S8) nanoparticles can serve as an electrochemically active, noble-metal-free material toward hydrogen evolution reaction, and they work stably in neutral solution (pH 7) but not in acidic (pH 0) and basic (pH 14) media. We, therefore, further present a carbon-armoring strategy to increase the durability and activity of Co9S8 over a wider pH range. In particular, carbon-armored Co9S8 nanoparticles (Co9S8@C) are prepared by direct thermal treatment of a mixture of cobalt nitrate and trithiocyanuric acid at 700 °C in N2 atmosphere. Trithiocyanuric acid functions as both sulfur and carbon sources in the reaction system. The resulting Co9S8@C material operates well with high activity over a broad pH range, from pH 0 to 14, and gives nearly 100% Faradaic yield during hydrogen evolution reaction under acidic (pH 0), neutral (pH 7), and basic (pH 14) media. To the best of our knowledge, this is the first time that a transition-metal chalcogenide material is shown to have all-pH efficient and durable electrocatalytic activity. Identifying Co9S8 as the catalytically active phase and developing carbon-armoring as the improvement strategy are anticipated to give a fresh impetus to rational design of high-performance noble-metal-free water splitting catalysts.

Effects of morphology on the electrochemical performances of Li3V2(PO4)3 cathode material for lithium ion batteries

The effects of various morphologies on the electrochemical performances of Li₃V₂(PO₄)₃ (LVP) were summarized and discussed.

Nanocomposite Li3V2(PO4)3/carbon as a cathode material with high rate performance and long-term cycling stability in lithium-ion batteries

Li₃V₂(PO₄)₃/carbon nanocomposite with high electrochemical performance has been successfully synthesized by combining sol–gel method and nanocasting route.

A better understanding of the capacity fading mechanisms of Li3V2(PO4)3

The main capacity decay of Li₃V₂(PO₄)₃ lies in the kinetic limitation between the LiV₂(PO₄)₃ ↔ V₂(PO₄)₃ phase transition, vanadium dissolution, rather than structure degradation.

A study of the electrochemical behavior at low temperature of the Li3V2(PO4)3 cathode material for Li-ion batteries

CNT coatings combined with an optimized electrolyte are introduced to improve the low temperature performances of Li₃V₂(PO₄)₃.

Enhanced electrochemical performance of Li3V2(PO4)3 microspheres assembled with nanoparticles embedded in a carbon matrix

We have synthesized uniform Li₃V₂(PO₄)₃ microspheres assembled with nanoparticles embedded in carbon matrix as an efficient cathode material for lithium ion battery.

Li3V2(PO4)3 particles embedded in porous N-doped carbon as high-rate and long-life cathode material for Li-ion batteries

The porous N-doped carbon stabilized Li₃V₂(PO₄)₃ particles are obtained by using a modified sol–gel method, and the composite exhibits a high discharge capacity of 114.7 mA h g⁻¹ at 1 C in the voltage range of 3–4.3 V after 600 cycles.

Stable 4 V-class bicontinuous cathodes by hierarchically porous carbon coating on Li3V2(PO4)3 nanospheres

A high performance, durable cathode material for lithium ion batteries is achieved by incorporating ∼50 nm Li3V2(PO4)3/C core-shell nanospheres into a porous carbon framework. The Li3V2(PO4)3/C nanocomposite delivers an initial discharge capacity of 130 mA h g(-1), approaching its theoretical limit (133 mA h g(-1)). At a high current rate (10 C), the nanocomposite displays an impressive long cycle life and remarkable capacity retention (90% after 1200 cycles). Notably, the Coulombic efficiency is above 99% during the course of cycling. The remarkable power capability and cycle stability derived from our simple and scalable synthesis suggests that this 4 V-class material could be one of the most promising candidates for future batteries.

Effect of carbon matrix dimensions on the electrochemical properties of Na3V2(PO4)3 nanograins for high-performance symmetric sodium-ion batteries

Na3V2(PO4)3 nanograins dispersed in different carbon matrices are rationally synthesized and systematically characterized. The acetylene carbon matrix provides the best conductive networks for electrons and sodium ions, which endows Na3V2(PO4)3 stable cyclability and high rate performance. The Na3V2 (PO4)3 -based symmetric sodium-ion batteries show outstanding electrochemical performance, which is promising for large-scale and low-cost energy storage applications.

One-Pot synthesized bicontinuous hierarchical Li3V2(PO4)3/C mesoporous nanowires for high-rate and ultralong-life lithium-ion batteries

Lithium-ion batteries have attracted enormous attention for large-scale and sustainable energy storage applications. Here we present a design of hierarchical Li3V2(PO4)3/C mesoporous nanowires via one-pot synthesis process. The mesoporous structure is directly in situ carbonized from the surfactants (CTAB and oxalic acid) along with the crystallization of Li3V2(PO4)3 without using any hard templates. As a cathode for lithium-ion battery, the Li3V2(PO4)3/C mesoporous nanowires exhibit outstanding high-rate and ultralong-life performance with capacity retention of 80.0% after 3000 cycles at 5 C in 3-4.3 V. Even at 10 C, it still delivers 88.0% of its theoretical capacity. The ability to provide this level of performance is attributed to the hierarchical mesoporous nanowires with bicontinuous electron/ion pathways, large electrode-electrolyte contact area, low charge transfer resistance, and robust structure stability upon prolonged cycling. Our work demonstrates that the unique mesoporous nanowires structure is favorable for improving the cyclability and rate capability in energy storage applications.

Facile synthesis of nitrogen-doped carbon derived from polydopamine-coated Li3V2(PO4)3 as cathode material for lithium-ion batteries

Nitrogen-doped, carbon-coated Li₃V₂(PO₄)₃ cathode materials were prepared by the oxidative self-polymerization of dopamine on the Li₃V₂(PO₄)₃ surface and subsequent carbonization of polydopamine.