Polymer-Templated LiFePO4/C Nanonetworks as High-Performance Cathode Materials for Lithium-Ion Batteries

Preparation of High-Purity Nano-Iron Phosphate from Titanium-Extraction Tailings by Co-Leaching Synergetic Ultrasonic-Enhanced Precipitation Process

The preparation of high-performance electrode materials from metallurgical solid waste is an effective strategy to address current energy and environmental challenges. This study utilizes a mixed acid leaching and ultrasound-assisted precipitation process to extract valuable metallic iron from titanium-extraction tailings (TET) to produce high-purity nano-FePO4 electrode material precursors with unique crystal structures. A leaching efficiency of 95.2% for Fe was attained by using the optimized process parameters, which included a mixed acid concentration of 4 mol/L, a liquid-to-solid ratio of 4:1, and a leaching temperature of 70 °C for 1 h. The optimal precipitation conditions were a pH of 2.0, a temperature of 60 °C, an aging time of 30 min, and a stirring speed of 600 rpm, resulting in FePO4 purity up to 99.6% and fine particle size. Thermodynamic calculations, combined with various characterizations, elucidated the leaching and precipitation mechanisms, highlighting the synergistic effect of phosphoric acid and hydrochloric acid in enhancing the leaching reaction. The thermogravimetric analysis indicated that the decomposition of residual ammonium chloride impurities requires calcination above 360 °C. This research not only provides new insights into the high-value, clean utilization of metallurgical solid waste but also supports sustainable resource recovery and environmental protection by transforming waste into valuable products.

Electrochemical Relithiation in Spent LiFePO4 Slurry for Regeneration of Lithium-Ion Battery Cathode

Recycling spent lithium-ion batteries (LIBs) in a green and economical way is vital for maintaining the sustainability of the LIB industry. However, given the low content of high-value components in olivine-type lithium iron phosphate (LFP), traditional metallurgical processes are economically unfeasible for recycling due to high chemical/energy consumption and labor-intensive procedures. This study proposes a facile electrochemistry strategy to directly regenerate the spent LFP material by an electrically driven lithiation process as a spent LFP slurry (200 g/L) rather than as electrodes. Minimal energy and chemical consumption are achieved by enabling the healing of spent LFP without destroying the original olivine-type crystal structure. The proposed method utilizes mild healing conditions (25 °C for 2 h) and LiCl solution as the only reagent in the regeneration process, significantly lowering the expenses associated with producing cathode electrodes. The electrochemical performance of the regenerated LFP have been dramatically recovered after regeneration, exhibiting a capacity of 151.5 mA h g-1 at 0.1 C and 96.6% capacity retention over 400 cycles at 1 C. This approach demonstrates a high processing capability and offers considerable economic and environmental benefits, making it an eco-friendly option and supporting the sustainable development of the LFP industry.

Novel Synthesis of 3D Mesoporous FePO4 from Electroflocculation of Iron Filings as a Precursor of High-Performance LiFePO4/C Cathode for Lithium-Ion Batteries

This study presents an economic and environmentally friendly method for the synthesis of microspherical FePO₄·2H₂O precursors with secondary nanostructures by the electroflocculation of low-cost iron fillers in a hot solution. The morphology and crystalline shape of the precursors were adjusted by gradient co-precipitation of pH conditions. The effect of precursor structure and morphology on the electrochemical performance of the synthesized LiFePO₄/C was investigated. Electrochemical analysis showed that the assembly of FePO₄·2H₂O submicron spherical particles from primary nanoparticles and nanorods resulted in LiFePO₄/C exhibiting excellent multiplicity and cycling performance with first discharge capacities at 0.2C, 1C, 5C, and 10C of 162.8, 134.7, 85.5, and 47.7 mAh·g^-1, respectively, and the capacity of LiFePO₄/C was maintained at 85.5% after 300 cycles at 1C. The significant improvement in the electrochemical performance of LiFePO₄/C was attributed to the enhanced Li⁺ diffusion rate and the crystallinity of LiFePO₄/C. Thus, this work shows a new three-dimensional mesoporous FePO₄ synthesized from the iron flake electroflocculation as a precursor for high-performance LiFePO₄/C cathodes for 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.

Y–F co-doping behavior of LiFePO4/C nanocomposites for high-rate lithium-ion batteries

Lithium iron phosphate (LFP) has become one of the current mainstream cathode materials due to its high safety and low price.

Fast-Charging Cathodes from Polymer-Templated Mesoporous LiVPO4F

Fast-charging cathodes with high operating voltages are critical to the development of high energy and power density lithium-ion batteries. One route to fast-charging battery materials is through the formation of nanoporous networks, but these methods are often limited by the high calcination temperatures required for synthesis. Here, we report the synthesis of carbon-coated nanoporous LiVPO₄F with excellent rate capabilities that can be stably cycled up to 4.6 V in standard LiPF₆ electrolytes. During charge and discharge at 30C, 110 mAh/g (70% of theoretical capacity) was obtained, and only 9% of capacity was lost after 2000 cycles at 20C. These materials also showed excellent stability, with little self-discharge, an open-circuit voltage of 4.2 V, and a discharge capacity of 139 mAh/g obtained after holding for 12 h. Rate capabilities were further demonstrated in a proof-of-concept full cell made with a nanostructured Nb₂O₅. These devices were able to deliver 200 mAh/g at 1C and 100 mAh/g at 30C. Finally, operando X-ray diffraction and electrochemical kinetics were further used to provide insight into the nature of fast charging in these materials.

All-Solid-State Lithium Ion Batteries Using Self-Organized TiO2 Nanotubes Grown from Ti-6Al-4V Alloy

All-solid-state batteries were fabricated by assembling a layer of self-organized TiO₂ nanotubes grown on as anode, a thin-film of polymer as an electrolyte and separator, and a layer of composite LiFePO₄ as a cathode. The synthesis of self-organized TiO₂ NTs from Ti-6Al-4V alloy was carried out via one-step electrochemical anodization in a fluoride ethylene glycol containing electrolytes. The electrodeposition of the polymer electrolyte onto anatase TiO₂ NTs was performed by cyclic voltammetry. The anodized Ti-6Al-4V alloys were characterized by scanning electron microscopy and X-ray diffraction. The electrochemical properties of the anodized Ti-6Al-4V alloys were investigated by cyclic voltammetry and chronopotentiometry techniques. The full-cell shows a high first-cycle Coulombic efficiency of 96.8% with a capacity retention of 97.4% after 50 cycles and delivers a stable discharge capacity of 63 μAh cm⁻² μm⁻¹ (119 mAh g⁻¹) at a kinetic rate of C/10.

La4NiLiO8-Shielded Layered Cathode Materials for Emerging High-Performance Safe Batteries

Low theoretical capacities of the commercial cathode materials (olivine: ∼170 mA h g^-1 and spinel: ∼140 mA h g^-1) dictate the need for higher energy density alternates such as nickel-rich (denotes as NCM) materials with a theoretical capacity of ∼270 mA h g^-1. However, low conductivity and the bulk degradation after direct contact with liquid electrolytes, especially at temperatures higher than 50 °C, are the biggest issues to resolve for safe use and confident commercialization of the NCM materials. In this context, we first report "La₄NiLiO₈ shields" to simultaneously boost charge conduction characteristics and circumvent the electrolytic degradation of NCM. Consequently, the La₄NiLiO₈-shielded LiNi_0.5Co_0.2Mn_0.3O₂ (LSN5) not only offers a 4.1× less charge transfer resistance and significantly higher discharge capacity (219.7 mA h g^-1) than the nonshielded NCM (187 mA h g^-1) and theoretical capacities of commercial cathode materials but also maintains more than 91.7% of capacity retention at 25 °C after 500 cycles and 84.2% at 60 °C after 200 cycles. In contrast, the nonshielded NCM cathodes can only provide 58.9 and 45.5% capacity retentions at corresponding test temperatures and performance cycles. The acquired excellent electrochemical performance and battery stability at both the ambient and high-temperature conductions infer great importance of the novel La₄NiLiO₈ shields in developing high-performance safe secondary batteries.

Direct regeneration of spent LiFePO4via a graphite prelithiation strategy

A new, low-cost and green regeneration method was developed to revive spent LiFePO₄-based batteries.

Self-assembly of block copolymers towards mesoporous materials for energy storage and conversion systems

This paper reviews the progress in the field of block copolymer-templated mesoporous materials, including synthetic methods, morphological and pore size control and their potential applications in energy storage and conversion devices.

Temperature-Controlled Synthesis of Li- and Mn-Rich Li1.2Mn0.54Ni0.13Co0.13O2 Hollow Nano/Sub-Microsphere Electrodes for High-Performance Lithium-Ion Battery

The calcination temperature plays a significant role in the structural, textural, and energy-storage performance of metal oxide nanomaterials in Li-ion battery application. Here, we report the formation of well-crystallized homogeneously dispersed Li1.2Mn0.54Ni0.13Co0.13O2 hollow nano/sub-microsphere architectures through a simple cost-effective coprecipitation and chemical mixing route without surface modification for improving the efficiency of energy storage devices. The synthesized Li1.2Mn0.54Ni0.13Co0.13O2 hollow nano/sub-microsphere cathode materials are calcined at 800, 900, 950, and 1000 °C. Among them, Li1.2Mn0.54Ni0.13Co0.13O2 calcined at 950 °C exhibits a high discharge capacity (277 mAh g-1 at 0.1C rate) and excellent capacity retention (88%) after 50 cycles and also delivers an excellent discharge capacity of >172 mAh g-1 at 5C rate. Good electrochemical performance of Li1.2Mn0.54Ni0.13Co0.13O2-950 is directly related to the optimized size of its primary particles (85 nm) (which constitute the spherical secondary particle, ∼720 nm) and homogeneous cation mixing. Higher calcination temperature (≥950 °C) leads to an increase of the primary particle size, poor cycling stability, and inferior rate capacity of Li1.2Mn0.54Ni0.13Co0.13O2 due to smashing of quasi-hollow spheres upon repeated lithium ion intercalations/deintercalations. Therefore, Li1.2Mn0.54Ni0.13Co0.13O2-950 is a promising electrode for the next-generation high-voltage and high-capacity Li-ion battery application.

Double Donors Tuning Conductivity of LiVPO4F for Advanced Lithium-Ion Batteries

To fulfill the increasing demand of lithium-ion batteries for realizing high energy density and great cycling stability under high rate, the cathode material capable of efficient electron and Li⁺-ion transportation is necessarily demanded. Herein, we propose a double-donor doping strategy by taking the carbon-coated LiVPO₄F as a model system. The Hall effect confirms that either or both Mg²⁺ substitution of Li⁺ and Nb⁵⁺ substitution of V³⁺ cause the carrier-type transformation from p-type to n-type. The great enhancements of electronic conductivity and ionic conductivity are realized in Li_0.995Mg_0.005V_0.98Nb_0.02PO₄F, which also exhibits a markedly improved Li⁺ diffusion coefficient and reduced electrochemical polarization. The carbon-coating layer can effectively prevent the decomposition reaction of electrolyte, allowing for good structural stability of Li_0.995Mg_0.005V_0.98Nb_0.02PO₄F when suffering fast Li⁺ insertion/extraction. As expected, the Li_0.995Mg_0.005V_0.98Nb_0.02PO₄F cathode exhibited superior electrochemical properties with an initial discharge capacity of 124.5 mA h g^-1 and capacity retention of 97.3% after 600 cycles at 1.6C. Even under a high rate of 8C, the discharge energy density was 392 Wh kg^-1 at the beginning and showed a retention rate of 84.4% after 2000 cycles.

Morphology-Directed Synthesis of LiFePO4 and LiCoPO4 from Nanostructured Li1+2 xPO3+ x

A LiPO₃-type nanostructure has been developed using a simple microwave approach at temperatures as low as 200 °C. This phase presents an ideal architecture for the morphology-directed synthesis of the olivine-type phases LiFePO₄ and LiCoPO₄, through a simple and scalable solution-based technique. Pure and carbon-composited olivine phases of interconnected nanoparticulate morphologies display excellent performance at high rates (up to 20 C) over 500 cycles in Li-ion battery cells.

A LiPO₃-type nanostructured architecture has been developed through a simple microwave approach, and its use as a precursor to olivine-type LiMPO₄/C cathodes allows for morphology retention and excellent electrochemical performance

Clean Block Copolymer Microparticles from Supercritical CO2: Universal Templates for the Facile and Scalable Fabrication of Hierarchical Mesostructured Metal Oxides

Metal oxide microparticles with well-defined internal mesostructures are promising materials for a variety of different applications, but practical routes to such materials that allow the constituent structural length scales to be precisely tuned have thus far been difficult to realize. Herein, we describe a novel platform methodology that utilizes self-assembled block copolymer (BCP) microparticles synthesized by dispersion polymerization in supercritical CO₂ (scCO₂) as universal structure directing agents for both hydrolytic and nonhydrolytic sol-gel routes to metal oxides. Spherically structured poly(methyl methacrylate- block-4-vinylpyridine) (PMMA- b-P4VP) BCP microparticles are translated into a series of the corresponding organic/inorganic composites and pure inorganic derivatives with a high degree of fidelity for the metal oxides TiO₂ and LiFePO₄. The final products are comprised of particles close to 1 μm in size with a highly ordered internal morphology of interconnected spheres between 20-40 nm in size. Furthermore, our approach is readily scalable, enabling grams of pure or carbon-coated TiO₂ and LiFePO₄, respectively, to be fabricated in a facile two step route involving ambient temperature mixing and drying stages. Given that both length scales within these BCP microparticles can be controlled independently by minor variations in the reagent quantities used, the present general strategy could represent a milestone in the design and synthesis of hierarchical metal oxides with completely tunable dimensions.

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.