Nitrogen-doped carbon nanofiber decorated LiFePO<Subscript>4</Subscript> composites with superior performance for lithium-ion batteries

Nitrogen-doped carbon nanofiber (NCNF) decorated LiFePO₄ (LFP) composites are synthesized via an in situ hydrothermal growth method. Electrochemical performance results show that the embedded NCNF can improve electron and ion transfer, thereby resulting in excellent cycling performance. The as-prepared LFP and NCNF composites exhibit excellent electrochemical properties with discharge capacities of 188.9 mAh g^?1 (at 0.2 C) maintained at 167.9 mAh g^?1 even after 200 charge/discharge cycles. The electrode also presents a good rate capability of 10 C and a reversible specific capacity as high as 95.7 mAh g^?1. LFP composites are a potential alternative high-performing anode material for lithium ion batteries.     

Advanced LiTi<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>/C anode by incorporation of carbon nanotubes for aqueous lithium-ion batteries

Inferior rate capability is a big challenge for LiTi₂(PO₄)₃ anode for aqueous lithium-ion batteries. Herein, to address such issue, we synthesized a high-performance LiTi₂(PO₄)₃/carbon/carbon nanotube (LTP/C/CNT) composite by virtue of high-quality carbon coating and incorporation of good conductive network. The as-prepared LTP/C/CNT composite exhibits excellent rate performance with discharge capacity of 80.1 and 59.1 mAh g^?1 at 10 C and 20 C (based on the mass of anode, 1 C = 150 mA g^?1), much larger than that of the LTP/C composite (53.4 mAh g^?1 at 10 C, and 31.7 mAh g^?1 at 20 C). LTP/C/CNT also demonstrates outstanding cycling stability with capacity retention of 83.3 % after 1000 cycles at 5 C, superior to LTP/C without incorporation of CNTs (60.1 %). As verified, the excellent electrochemical performance of the LTP/C/CNT composite is attributed to the enhanced electrical conductivity, rapid charge transfer, and Li-ion diffusion because of the incorporation of CNTs.     

Dandelion-like mesoporous Co<Subscript>3</Subscript>O<Subscript>4</Subscript> as anode materials for lithium ion batteries

A dandelion-like mesoporous Co₃O₄ was fabricated and employed as anode materials of lithium ion batteries (LIBs). The architecture and electrochemical performance of dandelion-like mesoporous Co₃O₄ were investigated through structure characterization and galvanostatic charge/discharge test. The as-prepared dandelion-like mesoporous Co₃O₄ consisted of well-distributed nanoneedles (about 40 nm in width and about 5 μm in length) with rich micropores. Electrochemical experiments illustrated that the as-prepared dandelion-like mesoporous Co₃O₄ as anode materials of LIBs exhibited high reversible specific capacity of 1430.0 mA h g^?1 and 1013.4 mA h g^?1 at the current density of 0.2 A g^?1 for the first and 100th cycle, respectively. The outstanding lithium storage properties of the as-prepared dandelion-like mesoporous Co₃O₄ might be attributed to its dandelion-like mesoporous nanostructure together with an open space between adjacent nanoneedle networks promoting the intercalation/deintercalation of lithium ions and the charge transfer on the electrode. The enhanced capacity as well as its high-rate capability made the as-prepared dandelion-like mesoporous Co₃O₄ to be a good candidate as a high-performance anode material for LIBs.     

Synthesis of hierarchical nanospheres Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/graphene composite and its application in lithium-ion battery as a high-performance anode material

A hierarchically nanospherical α-Fe₂O₃/graphene composite with a homogeneous mono-pore size of 4 nm has been prepared using a hydrothermal method. The composite showed an extremely high rate performance and good cycling stability when applied as an anode material for lithium-ion batteries owing to its unique three dimensional architecture. A specific capacity of 110 mAh/g was obtained at an extremely high current rate of 40 A/g and recover to 830 mAh/g at 0.5 A/g after 60 cycles. After 250 cycles at 2 A/g, the composite electrode exhibited a capacity of 630 mAh/g with a columbic efficiency of 99.5 %.     

Fabrication and electrochemical investigation of Li<Subscript>0.5</Subscript>TiO<Subscript>2</Subscript> as anode materials for lithium ion batteries

Hexagonal and cubic Li_0.5TiO₂ particles have been fabricated through magnesiothermic reduction of Li₂TiO₃ particles in a temperature range of 600 to 640 °C. The prolonged reduction time results in lattice transition from hexagonal to cubic structure of Li_0.5TiO₂. Their microstructures, valance state, chemical composition, as well as electrochemical performance as anode candidates for lithium ion batteries have been characterized and evaluated. The hexagonal Li_0.5TiO₂ exhibits better electrochemical activity compared with the cubic one. Further, the carbon-coated hexagonal Li_0.5TiO₂ displays improved electrochemical performance with initial reversible capacity of 176.6 mAh g^?1 and excellent cyclic behavior except capacity fading in the initial 10 cycles, which demonstrate a novel anode candidate for long lifetime lithium ion batteries.     

Synthesis of hierarchical Na<Subscript>2</Subscript>FeP<Subscript>2</Subscript>O<Subscript>7</Subscript> spheres with high electrochemical performance via spray drying

Hierarchical Na₂FeP₂O₇ spheres with nanoparticles were successfully fabricated by a facile spray drying method. A relatively low drying temperature was introduced in order to form a carbon layer on the surface. As a cathode material for sodium-ion batteries, it delivered a reversible capacity of 84.4 mAh g^?1 at 0.1 C and showed excellent cycling and rate performance (64.7 mAh g^?1 at 5 C). Furthermore, a full sodium battery was fabricated using SP-Na₂FeP₂O₇ as the cathode and hard carbon as the anode, suffering almost no capacity loss after 400 cycles at 1 C. Due to its superior electrochemical property and the low materials cost, Na₂FeP₂O₇ is becoming a promising cathode material for large-scale energy storage systems.     

Preparation and characterization of LiTi<Subscript>2</Subscript>O<Subscript>4</Subscript> anode material synthesized by one-step solid-state reaction

LiTi₂O₄ anode material for lithium-ion battery has been prepared by a novel one-step solid-state reaction method using Li₂CO₃, TiO₂, and carbon black as raw materials. X-ray diffraction, scanning electron microscopy, energy-dispersive spectrometry, and the determination of electrochemical properties show that the single phase of LiTi₂O₄ with spinel crystal structure is formed at 850?°C by this new method, and the lattice parameter is about 8.392?Å. The primary particle size of the LiTi₂O₄ powder is about 0.5–1.0 μm and its morphology is similar to a sphere. The lithium ion insertion voltage of LiTi₂O₄ anode material is about 1.50 V versus lithium metal, the initial discharge capacity is about 133.6 mAh g^-1, the charge–discharge voltage plateau is very flat, and no solid electrolyte interface film is formed when working potential is more than 1.0 V. The reaction reversibility and the cycling stability are excellent, and the high rate performance is good.     

A facile synthesis of heteroatom-doped carbon framework anchored with TiO<Subscript>2</Subscript> nanoparticles for high performance lithium ion battery anodes

Titanium dioxide (TiO₂)-based materials have been well studied because of the high safety and excellent cycling performance when employed as anode materials for lithium ion batteries (LIBs), whereas, the relatively low theoretical capacity (only 335 mAh g^?1) and serious kinetic problems such as poor electrical conductivity (~?10^?13S cm^?1) and low lithium diffusion coefficient (~?10^?9 to 10^?13 cm² s^?1) hinder the development of the TiO₂-based anode materials. To overcome these drawbacks, we present a facile strategy to synthesize N/S dual-doping carbon framework anchored with TiO₂ nanoparticles (NSC@TiO₂) as LIBs anode. Typically, TiO₂ nanoparticles are anchored into the porous graphene-based sheets with N, S dual doping feature, which is produced by carbonization and KOH activation process. The as-obtained NSC@TiO₂ electrode exhibits a high specific capacity of 250 mAh g^?1 with a coulombic efficiency of 99% after 500 cycles at 200 mA g^?1 and excellent rate performance, indicating its promising as anode material for LIBs.     

Urea-assisted solvothermal synthesis of monodisperse multiporous hierarchical micro/nanostructured ZnCo<Subscript>2</Subscript>O<Subscript>4</Subscript> microspheres and their lithium storage properties

High-quality monodisperse multiporous hierarchical micro/nanostructured ZnCo₂O₄ microspheres have been fabricated by calcinating the Zn_1/3Co_2/3CO₃ precursor prepared by urea-assisted solvothermal method. The as-prepared products are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and Brunauer-Emmett-Teller (BET) measurement to study the crystal phase and morphology. When tested as anode material for lithium ion batteries, the multiporous ZnCo₂O₄ microspheres exhibit an initial discharge capacity of 1,369 mAh g^?1 (3,244.5 F cm^?3) and retain stable capacity of 800 mAh g^?1 (1,896 F cm^?3) after 30 cycles. It should be noted that the good electrochemical performances can be attributed to the porous structure composed of interconnected nanoscale particles, which can promote electrolyte diffusion and reduce volume change during discharge/charge processes. More importantly, this ZnCo₂O₄ 3D hierarchical structures provide a large number of active surface position for Li⁺ diffusion, which may contribute to the improved electrochemical performance towards lithium storage.     

Influence of cooling mode on the electrochemical properties of Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> anode materials for lithium-ion batteries

Li₄Ti₅O₁₂ (LTO) was synthesized with two different cooling methods by solid-state method, namely fast cooling and air cooling. The samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), galvanostatic charge–discharge test, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), respectively. XRD revealed that the basic LTO structure was not changed. FESEM images showed that fast cooling effectively reduced the particle sizes and the agglomeration of particles. Galvanostatic charge–discharge test showed that the air cooling sample exhibited a mediocre performance, having an initial discharge capacity of 136.3mAh?·?g^?1 at 0.5 C; however, the fast cooling sample demonstrated noticeable improvement in both of its discharge capacity and rate capability, with a high initial capacity value of 142.7 mAh?·?g^?1 at 0.5 C. CV measurements also revealed that fast cooling enhanced the reversibility of the LTO. EIS confirmed that fast cooling resulted in lower electrochemical polarization and a higher lithium-ion diffusion coefficient. Therefore, fast cooling have a great impact on discharge capacity, rate capability, and cycling performance of LTO anode materials for lithium-ion batteries.     

Facile and surfactant-free synthesis of SnO<Subscript>2</Subscript>-graphene hybrids as high performance anode for lithium-ion batteries

A facile microwave-assisted ethylene glycol method is developed to synthesize the SnO₂ nanoparticles dispersed on or encapsulated in reduced graphene oxide (SnO₂-rGO) hybrids. The morphology, structure, and composition of SnO₂-rGO are investigated by scanning electron microscopy, transmission electron microscope, thermo-gravimetric analyzer, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. The electrochemical performance of SnO₂-rGO as anode materials for lithium-ion batteries was tested by cyclic voltammetry, galvanostatic charge–discharge cycling, and rate capability test. It is found that the SnO₂ nanoparticles with a uniform distribution have p-type doping effect with rGO nanosheets. The as-prepared SnO₂-rGO hybrids exhibit remarkable lithium storage capacity and cycling stability, and the possible mechanism involved is also discussed. Their capacity is 1222 mAhg^?1 in the first cycle and maintains at 700 mAhg^?1 after 100 cycles. This good performance can be mainly attributed to the unique nanostructure, good structure stability, more space for volume expansion of SnO₂, and mass transfer of Li⁺ during cycling.     

Improved Li- storage performance of heat-treated InFeCoO<Subscript>4</Subscript> spinel prepared by glycine assisted chemical route

Herein, we show the synthesis of high-capacity anode, InFeCoO₄ spinel for lithium ion batteries (LIBs), by facile glycine-assisted chemical approach. The structure and morphology are evaluated by X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS) and scanning electron microscopy (SEM) techniques, respectively. The pure phase formation of spinel InFeCoO₄ is confirmed from XRD pattern, whereas the oxidation state of Co in 2+ is determined from XAS analysis. Electrochemical performance of InFeCoO₄ in the half-cell configuration is evaluated by galvanostatic and cyclic voltammetry (CV) in the voltage window of 0.005–3.0 V vs. Li. When cycled at 60 mA g^?1, it shows a high first cycle reversible capacity of 750 (±10) mA h g^?1. However, slow capacity degradation is noticed upon cycling and reached 285 (±10) mA h g^?1 after 40 cycles. An improved Li-storage performance is noticed under similar cycling condition, when the electrode is heat-treated. It shows first cycle reversible capacity of 880 (±10) mA h g^?1 and reached 535 (±10) mA h g^?1 after 40 cycles. The coulombic efficiency is >98 % during cycling. The improved Li-storage performance is possibly due to the distribution of PVDF (binder) in the active materials as well as better electrical contact after heat treatment.     

Synthesis of spinel LiNi<Subscript>0.5</Subscript>Mn<Subscript>1.5</Subscript>O<Subscript>4</Subscript> as advanced cathode via a modified oxalate co-precipitation method

Spinel-type LiNi_0.5Mn_1.5O₄ (LNMO) cathode materials for lithium ion batteries have been synthesized via a modified oxalate co-precipitation method. By virtue of the co-precipitation of Li⁺ with transition metal ions, the target materials can be obtained through one-pot reaction without subsequent mixing with lithium salts. What’s more, a uniform distribution between the lithium and transition metal ions at molecular level could be realized, which is beneficial for final electrochemical performances. The physical and electrochemical properties of the material are characterized by XRD, TGA, EDS, FT-IR, SEM, CV, EIS, and charge/discharge tests. The results prove that the as-prepared material owns a cubic spinel structure with a space group of Fd-3m, high crystallinity, uniform particle size, and excellent electrochemical performances. A higher initial capacity and superior rate performance are delivered compared with that of material by conventional co-precipitation method. High capacities of 131.7 and 104.0 mAh g^?1 could be displayed at 0.5 and 10 C, respectively. Excellent cycle stability is also demonstrated with more than 98.5 % capacity retention after 100 cycles at 1 C.     

Facile synthesis of N-doped carbon-coated Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> anode for application in high-rate lithium ion batteries

A facile sol-gel approach for the synthesis of lithium titanate composite decorated with N-doped carbon material (LTO/NC) is proposed. Urea is used as a nitrogen source in the proposed approach. The LTO/NC exhibits superior electrochemical performances as an electrode material for lithium-ion batteries, delivering a discharge capacity of as high as 103 mAh g^?1 at a high rate of 20 C and retaining a stable reversible capacity of 90 mAh g^?1 after 1000 cycles, corresponding to 100% capacity retention. These excellent electrochemical performances are proved by the nanoscale structure and N-doped carbon coating. NC layers were uniformly dispersed on the surface of LTO, thus preventing agglomeration, favoring the rapid migration of the inserted Li ion, and increasing the Li⁺ diffusion coefficient and electronic conductivity. LTO with the appropriate amount of NC coating is a promising anode material with applications in the development of high-powered and durable lithium-ion batteries.     

Facial synthesis of carbon-coated ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript>/graphene and their enhanced lithium storage properties

Carbon-coated ZnFe₂O₄ spheres with sizes of ~110–180 nm anchored on graphene nanosheets (ZF@C/G) are successfully prepared and applied as anode materials for lithium ion batteries (LIBs). The obtained ZF@C/G presents an initial discharge capacity of 1235 mAh g^?1 and maintains a reversible capacity of 775 mAh g^?1 after 150 cycles at a current density of 500 mA g^?1. After being tested at 2 A g^?1 for 700 cycles, the capacity still retains 617 mAh g^?1. The enhanced electrochemical performances can be attributed to the synergetic role of graphene and uniform carbon coating (~3–6 nm), which can inhibit the volume expansion, prevent the pulverization/aggregation upon prolonged cycling, and facilitate the electron transfer between carbon-coated ZnFe₂O₄ spheres. The electrochemical results suggest that the synthesized ZF@C/G nanostructures are promising electrode materials for high-performance lithium ion batteries.

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High-performance hierarchical cypress-like CuO/Cu<Subscript>2</Subscript>O/Cu anode for lithium ion battery

Composite CuO/Cu₂O/Cu anode for lithium ion battery was designed and synthesized via facile electrodeposition and the subsequent in situ thermal oxidation in air at 300 °C for 1 h. The as-prepared composite CuO/Cu₂O/Cu anode was studied in terms of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), galvanostatic charge/discharge, cyclic voltammetry (CV), and AC impedance. As expected, the composite CuO/Cu₂O/Cu with CuO-rich surface displayed hierarchical cypress-like morphology; furthermore, the hierarchical cypress-like CuO/Cu₂O/Cu anode also delivered satisfactory electrochemical performances. For example, the reversible discharge capacity remained at 534.1 mAh/g even after 100 cycles. The enhanced electrochemical performances were attributed to the hierarchical cypress-like porous structure and the synergistic effect among the composite active copper oxides and highly conductive Cu current collector.     

Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> quantum dots on 3D-framed graphene aerogel as an advanced anode material in lithium-ion batteries

Three-dimensional fabricated Fe₃O₄ quantum dots/graphene aerogel materials (Fe₃O₄ QDs/GA) were obtained from a facile hydrothermal strategy, followed by a subsequently heat treatment process. The Fe₃O₄ QDs (2–5 nm) are anchored tightly and dispersed uniformly on the surface of three-dimensional GA. The as-prepared anode materials exhibit a high reversible capacity of 1078 mAh g^?1 at a current density of 100 mA g^?1 after 70 cycles in lithium-ion batteries (LIBs) system. Moreover, the rate capacity still remains 536 mAh g^?1 at 1000 mA g^?1. The enhanced electrochemical performance is attributed to that the GA not only acts as a three-dimensional electronic conductive matrix for the fast transportation of Li⁺ and electrons, but also provides with double protection against the aggregation and pulverization of Fe₃O₄ QDs during cycling. Apparently, the synergistic effects of the three-dimensional GA and the quantum dots are fully utilized. Therefore, the Fe₃O₄ QDs/GA composites are promising materials as advanced anode materials for LIBs.     

Carbon@SnS<Subscript>2</Subscript> core-shell microspheres for lithium-ion battery anode materials

A novel unique C@SnS₂ core-shell structure composites consisting of well-dispersity carbon microspheres and ultrathin tin disulfide nanosheets were successfully synthesized for the first time through a simple solvothermal method. The thin SnS₂ nanosheets grew onto the carbon microspheres surfaces perpendicularly and formed the close-knit porous structure. When it was used as anode materials for lithium-ion batteries, the hybrid C@SnS₂ core-shell structure composites showed a remarkable electrochemical property than pure SnS₂ nanosheets. Typically, the hybrid composites with SnS₂ nanosheet shells and carbon microsphere’s core exhibited an excellent initial discharge capacity of 1611.6 mAh/g. Moreover, the hybrid composites exhibited capacities of 474.8–691.6 mAh/g at 100 mA/g over 50 battery cycles, while the pure SnS₂ could deliver capacities of 243–517.6 mAh/g in the tests. The results indicated that the improvement of lithium storage performance of the core-shell structure C@SnS₂ anode materials in terms of rate capability and cycling reversibility owing to the introduction of the smooth carbon microspheres and special designing of core-shell structure.     

Enhanced lithium storage performance of a self-assembled hierarchical porous Co<Subscript>3</Subscript>O<Subscript>4</Subscript>/VGCF hybrid high-capacity anode material for lithium-ion batteries

A Co₃O₄/vapor-grown carbon fiber (VGCF) hybrid material is prepared by a facile approach, namely, via liquid-phase carbonate precipitation followed by thermal decomposition of the precipitate at 380 °C for 2 h in argon gas flow. The material is characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller specific surface area analysis, and carbon elemental analysis. The Co₃O₄ in the hybrid material exhibits the morphology of porous submicron secondary particles which are self assembled from enormous cubic-phase crystalline Co₃O₄ nanograins. The electrochemical performance of the hybrid as a high-capacity conversion-type anode material for lithium-ion batteries is investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic discharge/charge methods. The hybrid material demonstrates high specific capacity, good rate capability, and good long-term cyclability, which are far superior to those of the pristine Co₃O₄ material prepared under similar conditions. For example, the reversible charge capacities of the hybrid can reach 1100–1150 mAh g^?1 at a lower current density of 0.1 or 0.2 A g^?1 and remain 600 mAh g^?1 at the high current density of 5 A g^?1. After 300 cycles at 0.5 A g^?1, a high charge capacity of 850 mAh g^?1 is retained. The enhanced electrochemical performance is attributed to the incorporated VGCFs as well as the porous structure and the smaller nanograins of the Co₃O₄ active material.     

Design and synthesis of a novel 3D hierarchical mesocarbon microbead as anodes for lithium ion batteries and sodium ion batteries

This work presents a feasible route for the facile synthesis of three-dimensional (3D) hierarchical mesocarbon microbead (MCMB) as anodes for lithium ion batteries (LIBs) and sodium ion batteries (SIBs). The MCMB is oxidized by modified hummers method, and then the precursor is treated by hydrogen reduction to form the HMCMB. The HMCMB with graphene-like architecture has high specific surface, sufficient pore volume, and increased interlayer spacing, which can provide more active insertion/extraction sites and reduce the Li⁺/Na⁺ diffusion resistance. When employed as anode materials for LIBs and SIBs, HMCMB anodes exhibit improved lithium and sodium storage capability. The HMCMB delivers a higher reversible capacity (471.1 and 177.5 mAh g^?1 at 100 mA g^?1 after 100 cycles) and a good rate performance (250 and 121 mAh g^?1 even at 1000 mA g^?1) for LIBs and SIBs, respectively.