Binder-free combination of amorphous TiO<Subscript>2</Subscript> nanotube arrays with highly conductive Cu bridges for lithium ion battery anode

Binder-free combination of highly conductive Cu bridges with amorphous TiO₂ nanotube arrays for lithium ion battery anode were designed and achieved via one-step facile electrodeposition. The obtained composite Cu/TiO₂ nanotubes electrode was studied in terms of XRD, SEM, EDX, galvanostatic charge/discharge, cycle stability, rate performance, and AC impedance. As expected, the composite electrode delivered higher discharge capacity, rate performance, and cycle stability than the bare one, possibly due to improved electrical conductivity and the synergy effect between conductive Cu bridges and amorphous TiO₂ nanotube arrays.     

Preparation of carbon encapsulated Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> anode material for lithium ion battery through pre-coating method

Carbon encapsulated Li₄Ti₅O₁₂ (C/Li₄Ti₅O₁₂) anode material for lithium ion battery was prepared by using the pre-coat method of two steps, and the TiO₂ was pre coated before the reaction with Li₂CO₃. The structure and morphology of the resultant C/Li₄Ti₅O₁₂ materials were characterized by X-ray diffraction (XRD) and scanning microscopy (SEM). Electrochemical tests showed that at 0.1 C, the initial discharge capacity was 169.9 mAh g^?1, and the discharge capacity was 80 mAh g^?1 at 5 C. After 100 cycles at 2 C, the discharge specific capacity was 108.5 mAh g^?1. Compare with one step coating method, results showed the C/Li₄Ti₅O₁₂ prepared by pre-coat method can reduce the particle’s size and effectively improve the electrochemical performance.     

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.     

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.     

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 electrochemical performance of lithium ion battery cathode Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>/C

Li-ion battery cathode material lithium-vanadium-phosphate Li₃V₂(PO₄)₃ was synthesized by a carbon-thermal reduction method, using stearic acid, LiH₂PO₄, and V₂O₅ as raw materials. And stearic acid acted as reductant, carbon source, and surface active agent. The effect of its content on the crystal structure and electrochemical performance of Li₃V₂(PO₄)₃/C were characterized by XRD and electrochemical performance testing, respectively. The results showed that the content of carbon source has no significant effect on the crystal structure of lithium vanadium phosphate. Lihtium vanadium phosphate obtained with 12.3% stearic acid demonstrated the best electrochemical properties with a typical discharge capacity of 119.4 mAh/g at 0.1 C and capacity retention behavior of 98.5% after 50 cycles. And it has high reversible discharge capacity of 83 mAh/g at 5 C with the voltage window of 3 to 4.3 V.     

Magnetic resonance of Cu and of Gd in insulating GdSr<Subscript>2</Subscript>Cu<Subscript>2</Subscript>NbO<Subscript>8</Subscript> and in superconducting GdSr<Subscript>2</Subscript>Cu<Subscript>2</Subscript>RuO<Subscript>8</Subscript>

Weak-ferromagnetic (or antiferromagnetic) resonance of Cu and electron spin resonance (ESR) of Gd are observed both in insulating GdSr₂Cu₂NbO₈ and in superconducting GdSr₂Cu₂RuO₈. The Cu resonance implies that the CuO₂ planes are magnetic and indicates that the superconducting layer of GdSr₂Cu₂RuO₈ is SrO (not CuO₂), as in its related superconducting compound without cuprate planes, doped Sr₂YRuO₆.     

Spray pyrolysis-deposited TiO<Subscript>2</Subscript> thin films as high-performance lithium ion battery anodes

Focusing on additive-free electrodes, thin films are of typical interest as electrodes for lithium ion battery application. Herein, we report the fabrication of TiO₂ thin films by spray pyrolysis deposition technique. X-ray diffraction and transmission electron microscopic analysis confirms the formation of anatase TiO₂. Electrochemical evaluation of these sub-micron TiO₂ thin films exhibits high-rate performance and long cycling stability. At 1C rate (1C?=?335 mA/g), the electrode delivered discharge capacity of 247 mAh/g allowing about 0.74 lithium into the structure. The electrodes also delivered specific capacities of 122 and 72 mAh/g at 10 and 30C rates, respectively. Without conductive additives, this excellent performance can be attributed to the nanosize effect of TiO₂ particles combined with the uniform porous architecture of the electrode. Upon cycling at high rates (10 and 30C), the electrode exhibited excellent cycling stability and retention, specifically only <?0.6% capacity loss per cycle over 2500 cycles.     

Nanocrystalline Cu<Subscript>2</Subscript>O prepared under high pressures

The effect of high pressure on the structure of Cu₂O is investigated. Polycrystalline samples are treated during different periods of time at different temperatures and pressures in the vicinity of the kinetic curve of the decomposition Cu₂O → Cu+CuO. The structure of the samples subjected to thermobaric treatment is characterized by x-ray diffraction, electron diffraction structural analysis, and electron microscopy at atmospheric pressure. It is found that, upon treatment of Cu₂O at temperatures and pressures close to the decomposition region, the microstructure undergoes a transformation into the nanocrystalline state.     

V<Subscript>2</Subscript>O<Subscript>5</Subscript>-SiO<Subscript>2</Subscript> hybrid as anode material for aqueous rechargeable lithium batteries

V₂O₅-SiO₂ hybrid material was fabricated by heat-treating a mixture of H₂SiO₃ and V₂O₅. SEM, TEM, XRD, and N₂ isotherm analyses were performed to characterize the morphology and structure details of the as-prepared V₂O₅-SiO₂. The possibility of using the as-prepared V₂O₅-SiO₂ as anode material for aqueous lithium-ion batteries was investigated. Potentiostatic and galvanostatic results indicated that the intercalation/de-intercalation of Li⁺ in this material in aqueous electrolyte was quasi-reversible. It was also found that a discharge capacity of up to 199.1 mAh g^?1 was obtained at a current density of 50 mA g^?1 in aqueous solution of 1 M Li₂SO₄, a value which is much higher than the available reported capacities of vanadium (+5) oxides in aqueous electrolytes.     

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 %.     

Magnetism and optical properties of nanocrystalline Cu<Subscript>2</Subscript>O and TiO<Subscript>2</Subscript> powders

The optical spectra of Cu₂O and TiO₂ nanopowders have been studied, which contain information about structural defects and are of interest in the search for optimum regimes providing the synthesis of ferromagnetic nanocrystals with Curie temperatures above room temperature.     

PAN-based carbon fiber@SnO<Subscript>2</Subscript> for highly reversible structural lithium-ion battery anode

The carbon fiber (CF) is frequently preferred because it is considered as a multifunctional lightweight composite, where the CF is not only acted as one completely integrated part of the device with high-performance structural reinforcement, but also served as one of the battery electrode to storage energy. However, the limitation of electrochemical capacity of commercial CFs for the structural lithium-ion battery (SLIB) is an urgent issue should be solved. Therefore, in this work, a novel strategy to fabricate CF@SnO₂ composite is developed by employing one-step tin tetrachloride solvothermal method. The performance of the CFs could be improved by growing the stannic oxide firmly on each CF to form a synergetic electrode. When tested as anode materials, a high reversible capacity of 510 mAh g^?1 at a current density of 100 mAh g^?1 is maintained without obvious decay up to 150 cycles (a huge increase as high as 637.5% than that of the pure CFs). Furthermore, our strategy reveals an attainable route, which could be as a promising way to make a sustainable anode for SLIBs and carbon-based multi-functional composite for other practical applications.     

LiNi<Subscript>0.5</Subscript>Mn<Subscript>1.5</Subscript>O<Subscript>4</Subscript> hollow nano-micro hierarchical microspheres as advanced cathode for lithium ion batteries

The high-voltage spinel-type LiNi_0.5Mn_1.5O₄ (LNMO) is a promising cathode material for next-generation lithium ion batteries. In this study, hollow LNMO microspheres have been synthesized via co-precipitation method accompanied with high-temperature calcinations. The physical and electrochemical properties of the materials are characterized by x-ray diffraction (XRD), TGA, RAMAN, CV, scanning electron microscope (SEM), transmission electon microscopy (TEM), electrochemical impendence spectroscopy (EIS), and charge-discharge tests. The results prove that the microspheres combine hollow structures inward and own a cubic spinel structure with space group of Fd-3m, high crystallinity, and excellent electrochemical performances. With the short Li⁺ diffusion length and hollow structure, the hierarchical LNMO microspheres exhibit 138.2 and 108.5 mAh g^?1 at 0.5 and 10 C, respectively. Excellent cycle stability is also demonstrated with more than 98.8 and 88.2 % capacity retention after 100 cycles at 1 and 10 C, respectively.     

Enhanced electrochemical performance of Cu<Subscript>2</Subscript>O-modified Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> anode material for lithium-ion batteries

Li₄Ti₅O₁₂/Cu₂O composite was prepared by ball milling Li₄Ti₅O₁₂ and Cu₂O with further heat treatment. The structure and electrochemical performance of the composite were investigated via X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge tests. Li₄Ti₅O₁₂/Cu₂O composite exhibited much better rate capability and capacity performance than pristine Li₄Ti₅O₁₂. The discharge capacity of the composite at 2 C rate reached up to 122.4 mAh g^?1 after 300 cycles with capacity retention of 91.3 %, which was significantly higher than that of the pristine Li₄Ti₅O₁₂ (89.6 mAh g^?1). The improvement can be ascribed to the Cu₂O modification. In addition, Cu₂O modification plays an important role in reducing the total resistance of the cell, which has been demonstrated by the electrochemical impedance spectroscopy analysis.     

Evaluation of LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript>-LiNi<Subscript>0.80</Subscript>Co<Subscript>0.15</Subscript>Al<Subscript>0.05</Subscript>O<Subscript>2</Subscript> hybrid material as cathode in soft-packed lithium ion battery

The major electrochemical performances of LiMn₂O₄ (LMO)-LiNi_0.80Co_0.15Al_0.05O₂ (NCA) blending cathodes with full-range ratios are evaluated in industrial perspective. The results indicate that the reversible lithium ions can be fully utilized when NCA percentage reaches up to 50 %. The median voltages of blends are higher than the value calculated from a linear relationship of the two pristine cathodes, which is beneficial to energy density. But a synergy effect on room-temperature cycle performance is not observed for the hybrid cathode. However, the high-temperature (45 °C) capacity retention with 70 % NCA is 97.9 % after 100 cycles, higher than both pristine cathodes. It is not until NCA content increases to more than 50 % that the high-rate performance is much deteriorated. Additionally, the swelling of fully charged pouch-type battery after 4 h storage at 85 °C disappears when NCA percentage is less than 50 %. Hence, it is practically manifested that critical flaws of NCA and LMO can be compromised by blending with each other in a critical ratio. In this way, NCA can be practically used in soft-packed battery.     

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.     

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.     

Electrospinning preparation of one-dimensional Co<Superscript>2+</Superscript>-doped Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> nanofibers for high-performance lithium ion battery

One-dimensional Co²⁺-doped Li₄Ti₅O₁₂ nanofibers with a diameter of approximately 500 nm have been synthesized via a one-step controllable electrospinning method. The Co²⁺-doped Li₄Ti₅O₁₂ nanofibers were systematically characterized by XRD, ICP, TEM, SEM, BET, EDS mapping, and XPS. Based on the cubic spinel structure and one-dimensional effect of Li₄Ti₅O₁₂, Co²⁺-doped Li₄Ti₅O₁₂ nanofibers exhibit the enlarged lattice volume, reduced particle size and enhanced electrical conductivity. More importantly, Co²⁺-doped Li₄Ti₅O₁₂ nanofibers as a lithium ion battery anode electrode performs superior electrochemical performance than undoped Li₄Ti₅O₁₂ electrode in terms of electrochemical measurements. Particularly, the reversible capacity of Co²⁺-doped Li₄Ti₅O₁₂ electrode reaches up to 140.1 mAh g^?1 and still maintains 136.5 mAh g^?1 after 200 cycles at a current rate of 5 C. Therefore, one-dimensional Co²⁺-doped Li₄Ti₅O₁₂ nanofiber electrodes, showing high reversible capacity and remarkable recycling property, could be a potential candidate as an anode material.     

NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript> polyhedra with controllable particle size as high-performance anode for lithium-ion battery

Different particle sizes of dodecahedron precursors are synthesized by controlling the polarity of the solution. Through the results of scanning electron microscope (SEM) images, it can be found that different particle sizes of precursors present obvious edge angles and their morphology can be well retained after annealing. X-ray diffraction (XRD) measurements suggest that the annealed polyhedral products are pure single-phase NiCo₂O₄. When tested as lithium-ion battery anode, 0.5 μm NiCo₂O₄ polyhedra exhibits a specific capacity of 1050 mAh g^?1 at 0.1 C at the 60th cycle, which was higher than theoretical capacity of single metal oxide (NiO 718 mAh g^?1 and Co₃O₄ 890 mAh g^?1). It also exhibits the highest rate capability with an average discharge capacity of 890, 700, 490, 330, and 300 mAh g^?1 at 0.5, 2, 4, 8, and 10 C, respectively. Those advantages are attributed to that small-sized particle with great surface areas decrease the actual current density at the surface and inner of the prepared electrode.