Anthracite-Derived Dual-Phase Carbon-Coated Li3V2(PO4)3 as High-Performance Cathode Material for Lithium Ion Batteries

In Situ Hydrogel Polymerization to Form a Flexible Polysaccharide Synergetic Binder Network for Stabilizing SiOx/C Anodes

Today, the commercial application of silicon oxides (SiOx, 1 < x < 2) in lithium-ion batteries (LIBs) still faces the challenge of rapid performance degradation. In this work, by integrating hydrothermal and physicomechanical processes, water-soluble locust bean gum (LBG) and xanthan gum (XG) are utilized to in situ form an LBG@XG binder network to improve the performance of SiOx/C anodes. As a synergy of LBG and XG polysaccharides in hydrogel polymerization, LBG@XG can tightly wrap around SiOx/C particles to prevent plate damage. The flexible SiOx/C anode with the LBG@XG binder exhibits capacity retentions of 74.1% and 76.4% after 1000 cycles at 0.5 A g-1 and 1 A g-1, respectively. The full battery capacity remains stable for 100 cycles at 1 C and the rate performance is excellent (103 mAh g-1 at 3 C). This LBG@XG is demonstrated to be highly electronegative and has a strong attraction to SiOx/C particles, thereby reducing the expansion and increasing the stability of the SiOx/C anodes when coupled with the flexible binder network. In addition to the promising LBG@XG binder, this work also provides a research idea for developing green water-based binders suitable for application in the SiOx/C anodes of LIBs.

Material Optimization Engineering toward xLiFePO4·yLi3V2(PO4)3 Composites in Application-Oriented Li-Ion Batteries

The development of LiFePO4 (LFP) in high-power energy storage devices is hampered by its slow Li-ion diffusion kinetics. Constructing the composite electrode materials with vanadium substitution is a scientific endeavor to boost LFP's power capacity. Herein, a series of xLiFePO4·yLi3V2(PO4)3 (xLFP·yLVP) composites were fabricated using a simple spray-drying approach. We propose that 5LFP·LVP is the optimal choice for Li-ion battery promotion, owning to its excellent Li-ion storage capacity (material energy density of 413.6 W·h·kg-1), strong machining capability (compacted density of 1.82 g·cm-3) and lower raw material cost consumption. Furthermore, the 5LFP·LVP||LTO Li-ion pouch cell also presents prominent energy storage capability. After 300 cycles of a constant current test at 400 mA, 75% of the initial capacity (379.1 mA·h) is achieved, with around 100% of Coulombic efficiency. A capacity retention of 60.3% is displayed for the 300th cycle when discharging at 1200 mA, with the capacity fading by 0.15% per cycle. This prototype provides a valid and scientific attempt to accelerate the development of xLFP·yLVP composites in application-oriented Li-ion batteries.

Magnetic Properties of Li3V2(PO4)3/Li3PO4 Composite

Here, we present the investigation of the magnetic properties of Li3V2(PO4)3/Li3PO4 composites, which can be potentially used as a cathode material in lithium-ion batteries. Li3V2(PO4)3/Li3PO4 was synthesized by the thermal hydrolysis method and has a granular mesoporous structure. Magnetic properties of the composite were investigated using magnetometry and electron spin resonance methods. Based on magnetization measurements, the simultaneous existence of the paramagnetic phase with antiferromagnetic interactions between spins of V3+ ions and magnetically correlated regions was suggested. Most probably, magnetically correlated regions were formed due to anti-site defects and the presence of V4+ ions that was directly confirmed by electron spin resonance measurements.

Boosting the cycling stability of Ni-rich layered oxide cathode by dry coating of ultrastable Li3V2(PO4)3 nanoparticles

Nickel (Ni)-rich layered oxides such as LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) represent one of the most promising candidates for next-generation high-energy lithium-ion batteries (LIBs). However, the pristine Ni-rich cathode materials usually suffer from poor structural stability during cycling. In this work, we demonstrate a simple but effective approach to improve the cycling stability of the NCM622 cathode by dry coating of ultrastable Li₃V₂(PO₄)₃-carbon (LVP-C) nanoparticles, which leads to a robust composite cathode (NCM622/LVP-C) without sacrificing the specific energy density compared with pristine NCM622. The optimal NCM622/LVP-C composite presents a high specific capacity of 162 mA h g^-1 at 0.5 C and excellent cycling performance with 85.0% capacity retention after 200 cycles at 2 C, higher than that of the pristine NCM622 (67.6%). Systematic characterization confirms that the LVP-C protective layer can effectively reduce the side reactions, restrict the cation mixing of NCM622 and improve its structural stability. Moreover, the NCM622/LVP-C||graphite full cells also show a commercial-level capacity of 3.2 mA h cm^-2 and much improved cycling stability compared with NCM622/LVP-C||graphite full cells, indicating the great promise for low-cost, high-capacity and long-life LIBs.

Hierarchical hollow microspheres Na3V2(PO4)2F3C@rGO as high-performance cathode materials for sodium ion batteries

Nanosheet-assembled Na₃V₂(PO₄)₂F₃ microspheres were synthesized by a one-step polyol-assisted hydrothermal method and combined with graphene as the cathode material for SIBs.

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.

Polydopamine-Derived Nitrogen-Doped Carbon-Covered Na3V2(PO4)2F3 Cathode Material for High-Performance Na-Ion Batteries

Nitrogen-doped carbon-covered Na₃V₂(PO₄)₂F₃ (NVPF/C-PDPA) composites have been successfully prepared by self-polymerization of dopamine on the NVPF surface and subsequent sintering. The X-ray diffraction results show that the NVPF/C-PDPA has good crystallinity and introducing dopamine does not affect the lattice structure of NVPF. The high-resolution transmission electron microscopy, high-angle annular dark-field images, and energy dispersive X-ray spectroscopy analyses reveal that the NVPF/C-PDPA particles are covered by a complete and uniform covering layer, which is effective at preventing corrosion of NVPF in the electrolyte to greatly increase cycling stability. Furthermore, N-doping into the carbon layer can produce additional active sites to improve the capacity especially the rate capacity. Such a NVPF/C-PDPA electrode delivers a remarkable rate capacity (98.0 mA h g^-1 at 10 C) and superior cycle performance (∼95.8% capacity retention at 10 C after 800 cycles). We believe that this work may be beneficial for accelerating the development of high-performance electrode materials and the commercialization of Na-ion batteries.

Porous NaTi2(PO4)3/C Hierarchical Nanofibers for Ultrafast Electrochemical Energy Storage

NaTi₂(PO₄)₃ (NTP) with a sodium superionic conductor three-dimensional (3D) framework is a promising anode material for sodium-ion batteries (SIBs) because of its suitable potential and stable structure. Although its 3D structure enables high Na-ion diffusivity, low electronic conductivity severely limits NTP's practical application in SIBs. Herein, we report porous NTP/C nanofibers (NTP/C-NFs) obtained via an electrospinning method. The NTP/C-NFs exhibit a high reversible capacity (120 mA h g^-1 at 0.2 C) and a long cycling stability (a capacity retention of ∼93% after 700 cycles at 2 C). Furthermore, sodium-ion full cells and hybrid sodium-ion capacitors have also been successfully assembled, both of which exhibit high-rate capabilities and remarkable cycling stabilities because of the high electronic/ionic conductivity and impressive structural stability of NTP/C-NFs. The results show that the nanoscale-tailored NTP/C-NFs could deliver new insights into the design of high-performing and highly stable anode materials for room-temperature SIBs.

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.

Organic-phase synthesis of Li3V2(PO4)3@Carbon nanocrystals and their lithium storage properties

Decreasing particle size is an efficient strategy for improving the lithium storage properties of Li₃V₂(PO₄)₃ (LVP) due to a shorter transport distances of lithium ion and electrons. However, designing and synthesizing LVP nanocrystals (NCs) with sizes smaller than 30 nm remains a challenge. In this work, we developed a facile approach for the fabrication of the monodisperse LVP NCs through a robust high-temperature organic-phase method. The thermodynamics of the synthesis and the possible reaction mechanism were investigated. The results indicate that the organic-phase environment (at 320 °C) may not thermodynamically allow the crystallization of LVP. Nevertheless, oleic acid (OA) and oleylamine (OAm) are essential as capping agents to hinder the agglomeration and growth of the particles. Based on the thermodynamic need, calcination is essential to prepare LVP. The surface electronic conductivity of the LVP NCs was enhanced through a subsequent carbon-coating treatment. The optimum combination of reduction and carbon coating is very favorable for the kinetics of electron transfer and lithium ion diffusion. Therefore, the fabricated LVP@C NCs exhibit superior lithium storage properties with excellent rate capability (84 mA h g⁻¹ at a rate of 20C) and perfect cyclic stability (96.2% capacity retention after 200 cycles at 5C), demonstrating their potential application in high-performance lithium-ion batteries.

Li₃V₂(PO₄)₃@Carbon nanocrystals exhibit superior lithium storage properties due to the shortened lithium-ion diffusion length and the enhanced surface electronic conductivity.