Li0.95Na0.05MnPO4/C nanoparticles compounded with reduced graphene oxide sheets for superior lithium ion battery cathode performance

Sodium-substituted LiMnPO₄/C/reduced graphene oxide (LNMP@rGO) was synthesized in this study via freeze drying and carbon thermal reduction method with graphene oxide as carbon source. Sodium ion doping is optimized and rGO effects are evaluated by XRD, SEM, TEM, BET, Raman, and electrochemical performance measurements. Well-distributed nanoparticles with average size of ~50?nm are evenly distributed on the surface or intercalation between rGO layers, resulting in a porous ion/electronic conductive network. Compared to 122.3?mA?h?g^?1 in unmodified LNMP, the best LNMP@rGO (20?mg rGO) exhibits an excellent initial discharge capacity of 150.4?mA?h?g^?1 at 0.05?C at 122.9% of the initial capacity. The capacity retention rate is 95.8% of the initial capacity after 100 cycles at 1?C. Capacity of 101.2?mA?h?g^?1 is preserved even at rates as high as 10?C.     

V2O3/rGO composite as a potential anode material for lithium ion batteries

V₂O₃ is a promising anode material and has attracted the interests of researchers because of its high theoretical capacity of 1070?mAh?g^?1, low discharge potential, inexpensiveness, abundant sources, and environmental friendliness. However, the development and application of V₂O₃ have been hindered by the low conductivity and drastic volume change of V₂O₃ composites. In this work, V₂O₃/reduced graphene oxide (rGO) nanocomposites are successfully prepared through a facile solvothermal method and annealing process. In this synthesis protocol, V₂O₃ nanoparticles (NPs) are encapsulated by rGO. This unique structure enables rGO to inhibit volume changes and improve the ion and electronic conductivity of V₂O₃. In addition, V₂O₃ NPs, which exhibit sizes of 5–40?nm, are uniformly dispersed on rGO sheets without aggregation. The Li⁺ storage behavior of V₂O₃/rGO is systematically investigated in the potential range 0.01–3.0?V. The V₂O₃/rGO nanocomposite can achieve a high reversible specific capacity of 823.4?mAh?g^?1 under the current density of 0.1?A?g^?1, and 407.3 mAh g^?1 under the high current density of 4.0?A?g^?1. The results of this study provide insight into the fabrication of rGO-based functional materials with extensive applications.     

Ordered mesoporous Co3O4 nanospheres / reduced graphene oxide composites for rutin detection

The ordered mesoporous Co₃O₄ nanospheres encapsulated with reduced graphene oxide (denoted as meso-Co₃O₄ / RGO) were synthesized via electrostatic interaction and firstly for the electrochemical detection of rutin with good sensing effects. The resultant meso-Co₃O₄ / RGO nanocatalyst not only possesses more active sites due to the high surface area deriving from the mesoporous structure, but also has benign conductibility due to the presence of RGO, both of which enhance the sensing properties for the electrochemical detection of rutin. The developed sensor displays low detection limit (0.03?μM) and large sensitivity (74.85?μA?μM^?1 cm^?2). Besides, the rutin sensor possesses good selectivity, stability and reproducibility.     

High capacity three-dimensional ordered macroporous CoFe2O4 as anode material for lithium ion batteries

A three-dimensional ordered macroporous (3DOM) cobalt ferrite (CoFe₂O₄) was prepared using polystyrene (PS) colloidal crystal template. The scanning electron microscopy (SEM) and the transmission electron microscopy (TEM) micrographs showed that the as-prepared CoFe₂O₄ material had a typical 3DOM structure, which was constructed with about 130 nm-sized macropores and 10-20 nm-sized walls. The obtained CoFe₂O₄ material had a specific surface area of 66.67 m² g⁻¹, and could deliver a relatively high capacity of 702 mAh g⁻¹ (about double that of graphite) at a current density of 0.2 mA cm⁻² after 30 cycles. Owing to the 3DOM nanoarchitecture, the as-prepared CoFe₂O₄ electrode exhibited a good rate performance. The results suggest a promising application of the 3DOM CoFe₂O₄ as anode material for lithium ion batteries.     

Synthesis of CuGeO3/reduced graphene oxide nanocomposite by hydrothermal reduction for high performance Li-ion battery anodes

Nowadays, Lithium-ion batteries (LIBs) are prevalently applied in numerous areas, leading to increasing demand of innovative electrodes with high specific capacities. An advanced CuGeO₃/reduced graphene oxide (rGO) structure is designed and fabricated as the anode material taking the advantage of considerable capacity offered by CuGeO₃ and stable framework constructed by rGO. The as-prepared CuGeO₃ with 30 wt% GO addition exhibits the best electrochemical performance. Specifically, a reversible charge capacity of 909 mAh·g⁻¹ with high coulombic efficiency of 91.49% at the current density of 100 mA g⁻¹ after 200 cycles is demonstrated, and the rate capacity retains 747.6 mAh·g⁻¹ with 91.59% capacity retention. These results indicate that the CuGeO₃/rGO composite holds great potential in next-generation LIBs.     

Free-standing SnO2 nanoparticles@graphene hybrid paper for advanced lithium-ion batteries

A free-standing SnO₂/reduced graphene oxide (re-G) hybrid paper has been successfully fabricated by a facile vacuum filtration approach through a uniformly dispersed SnO₂ nanoparticle and graphene oxide mixed solution. As potential anode material for high power and energy applications, the hybrid nanostructures were directly evaluated as anode for rechargeable lithium ion batteries without adding any polymer binder, conductive additives or current collectors. And the composite exhibits a greatly enhanced synergic effect with extremely high energy storage stability of 700 mAh g⁻¹ after 100 cycles benefiting from the advanced structural features.     

Hollow ZnSnO3 cubes@carbon/reduced graphene oxide ternary composite as anode of lithium ion batteries with enhanced electrochemical performance

The ternary composite, carbon coated hollow ZnSnO₃ (ZS@C) cubes encapsulated in reduced graphene oxide sheets (ZS@C/rGO), was synthesized via low-temperature coprecipitation and colloid electrostatic self-assembly. The uniform carbon-coating layer not only plays a role in buffering the volume change of ZnSnO₃ cubes in the charging/discharging processes, but also forms three-dimensional network with the cooperation of graphene to maintain the structural integrity and improve the electrical conductivity. The results show that the reduced graphene oxide sheets encapsulated ZS@C microcubes with a typical core-shell structure of ~700 nm in size exhibit an improved electrochemical performance compared with bare ZS@C microcubes. The ZS@C/rGO electrode delivered an initial discharge capacity of 1984 mA h g⁻¹ at a current density of 0.1 A g⁻¹ and maintained a capacity of 1040 mA h g⁻¹ after 45 cycles. High specific capacity and superior cycle stability indicate that the ZS@C/rGO composite has a great potential for the application of lithium-ion anode material.     

Self-assembly of Fe2O3 nanorods in carbon nanotube network as a 3D aerogel architecture for lithium ion batteries

Self-assembly of nanosized materials has been extensively studied for the assemblies usually exhibit novel properties and show potential applications in many fields. However, there are few studies about the self-assembly behavior during the formation of 3D architectures. Herein, interesting self-assembly of ultrathin α-Fe₂O₃ nanorods into micrometer-scale flakes or rods is exhibited during the formation of single walled carbon nanotube hydrogel network. The results show that this self-assembly is driven by oriented attachment mechanism with the assistance of surfactant acting as a template and 3D hydrogel structure as confined space. Benefitting from the 3D porous and interpenetrated structure, improved electron transfer network and increased active facets of Fe₂O₃, an initial charge capacity is high as 891?mAh/g and 73% could be retained after 200 cycles. While great rate capability (42% preserved at 1000?mA/g) are also demonstrating its potential for applications in lithium ion batteries.     

Li4Ti5O12 hollow microspheres assembled by nanosheets as an anode material for high-rate lithium ion batteries

In this paper, Li₄Ti₅O₁₂ (LTO) hollow microspheres with the shell consisting of nanosheets have been synthesized via a hydrothermal route and following calcination. Because of the favorable transport properties of this hollow structure, it is the rate performance at high current densities which is exceptional. When the LTO hollow microspheres were used as the anode material in lithium ion battery, they exhibited superior rate performance and high capacity even at a very high rate (131 mAh g⁻¹ at 50 C).     

Nanosized α-Fe2O3 and Li-Fe composite oxide electrodes for lithium-ion batteries

Nanosized α-Fe₂O₃ (ca. 50 nm) and Li-Fe composite oxides (ca. 29 nm) powders were synthesized via gel polymer route. The gels were obtained with thermal polymerization of acrylic acid solutions of iron and lithium nitrates. The calcination of these gels at temperatures from 300 °C to 500 °C results in α-Fe₂O₃ from Fe(NO₃)₃ precursor and Li-Fe composite oxides Li₂O-Fe₃O₄-LiFeO₂ from a mixed precursors of Fe(NO₃)₃ and LiNO₃. Thermal gravimetric analysis, X-ray diffraction and transmission electron microscopy were used to investigate the precursors and products. The electrochemical performance of the Fe-based oxides was also evaluated. After 200 cycles, their capacity can be as high as 1300 mAh/g for α-Fe₂O₃ and 1400 mAh/g for Li-Fe oxide while the initial capacity loss is as low as 21.8%. The Li-Fe oxide electrodes exhibit better capacity retention than the α-Fe₂O₃ electrodes. They are interesting negative electrodes for high energy density lithium-ion batteries.     

Study on capacity fade factors of lithium secondary batteries using LiNi0.7Co0.3O2 and graphite-coke hybrid carbon

In our previous work, 10 Wh-class (30650 type) lithium secondary batteries, which were fabricated with LiNi_0.7Co_0.3O₂ positive electrodes and graphite-coke hybrid carbon negative electrodes, showed an excellent cycle performance of 2350 cycles at a 70% state of charge charge-discharge cycle test. However, this cycle performance is insufficient for dispersed energy storage systems, such as home use load leveling systems. In order to clarify the capacity fade factors of the cell, we focused our investigation on the ability discharge capacity of the positive and negative electrodes after 2350 cycles. Although the cell capacity deteriorated to 70% of its initial capacity after 2350 cycles, it was confirmed that the LiNi_0.7Co_0.3O₂ positive electrode and graphite-coke hybrid negative electrode after 2350 cycles still have sufficient ability discharge capacity of 86 and 92% of their initial capacity, respectively. Accompanied by the result for a composition analysis of the positive electrode material by inductively coupled plasma (ICP) spectroscopy and atomic absorption spectrometry (AAS), electrochemical active lithium decreased and the Li_xNi_0.7Co_0.3O₂ positive electrode could be charged-discharged in a narrow range of between x=0.41 and 0.66 in the battery, although it had enough ability discharge capacity that can use between x=0.36 and 0.87. It is predicted that solid electrolyte interface formation by electrolyte decomposition on the carbon negative electrode during the charge-discharge cycle test is a main factor of the decrease of electrochemical active lithium.     

Hydrazine hydrate-induced hydrothermal synthesis of MnFe2O4 nanoparticles dispersed on graphene as high-performance anode material for lithium ion batteries

Herein, a MnFe₂O₄/graphene (MnFe₂O₄/G) nanocomposite has been synthesized via a facile N₂H₄·H₂O-induced hydrothermal method. During the synthesis, N₂H₄·H₂O is employed to not only reduce graphene oxide to graphene, but also prevent the oxidation of Mn²⁺ in alkaline aqueous solution, thus ensuring the formation of MnFe₂O₄/G. Moreover, MnFe₂O₄ nanoparticles (5–20 nm) are uniformly anchored on graphene. MnFe₂O₄/G electrode delivers a large reversible capacity of 768 mA h g⁻¹ at 1 A g⁻¹ after 200 cycles and high rate capability of 517 mA h g⁻¹ at 5 A g⁻¹. MnFe₂O₄/G holds great promise as anode material in practical applications due to the outstanding electrochemical performance combined with the facile synthesis strategy.     

Enhanced rate performance of carbon-coated LiNi0.5Mn1.5O4 cathode material for lithium ion batteries

Conductive carbon has been coated on the surface of LiNi_0.5Mn_1.5O₄ cathode material by the carbonization of sucrose for the purpose of improving the rate performance. The effect of carbon coating on the physical and electrochemical properties is discussed through the characterizations of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), cycling and rate tests. Results demonstrate that the carbon coating can greatly enhance the discharge capacity, rate capability and cycling stability of the LiNi_0.5Mn_1.5O₄ without degrading the spinel structure. The sample modified with 1 wt.% sucrose displays the best performance. A large capacity of 130 mAh g⁻¹ at 1 C discharge rate with a high retention of 92% after 100 cycles and a stable 114 mAh g⁻¹ at 5 C discharge rate can be delivered. The remarkably improved rate properties of the carbon-coated samples are due to the suppression of the solid electrolyte interfacial (SEI) layer development and faster kinetics of both the Li⁺ diffusion and the charge transfer reaction.     

High capacity ZnFe2O4 anode material for lithium ion batteries

A nanostructured ternary transition metal oxide, ZnFe₂O₄, is synthesized via the simple polymer pyrolysis method. The characteristics of the material are examined by thermogravimetry, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The electrochemical test results show that this method of ZnFe₂O₄ synthesis produces high specific capacities and good cycling performance, with an initial specific capacity as high as 1419.6 mAh g⁻¹ at first discharge that is maintained at over 800 mAh g⁻¹ even after 50 charge–discharge cycles. The electrode also presents a good rate capability, with a high rate of 4C (1C = 928 mA g⁻¹), a reversible specific capacity that can be as high as 400 mAh g⁻¹. ZnFe₂O₄ is a potential alternative to high-performance nanostructured anode material in lithium ion batteries.     

Synthesis of dandelion-like V2O3/C composite with bicontinuous 3D hierarchical structures as an anode for high performance lithium ion batteries

The dandelion-like V₂O₃/C composite was synthesized by a simple and facile template-free solvothermal method followed by a suitable thermal treatment. The dandelion-like V₂O₃/C composite is constructed by bicontinuous 3D hierarchical structures, which are formed by interconnected nanoparticles and interconnected pores, respectively. Moreover, the surface of interconnected nanoparticles is uniformly coated with an ultrathin carbon layer. Upon evaluation as an anode material for LIBs, the as-synthesized product shows superior electrochemical performance. Under the current density of 0.1?A?g^?1, the specific discharge capacity of V₂O₃/C composite is 737?mA?h?g^?1 after 100 cycles. Moreover, after 1000 cycles at a high current density of 2?A?g^?1, the sample exhibits a discharge capacity of 315?mA?h?g^?1 which is 94% of the first-cycle discharge capacity. This excellent electrochemical performance can be ascribed to its unique hierarchical structure with 3D interconnected nanopores and uniform carbon coating.     

Amorphous CoS nanoparticle/reduced graphene oxide composite as high-performance anode material for sodium-ion batteries

Transition metal sulfides have been proved as promising candidates of anode materials for sodium-ion batteries (SIBs) due to their high sodium storage capacity, low cost and enhanced safety. In this study, the amorphous CoS nanoparticle/reduced graphene oxide (CoS/rGO) composite has been fabricated by a facile one-step electron beam radiation route to in situ decorate amorphous CoS nanoparticle on the rGO nanosheets. Benefiting from the small particle size (~2 nm), amorphous structure, and electronic conductive rGO nanosheets, the CoS/rGO nanocomposite exhibits high sodium storage capacity (440 mAh g⁻¹ at 100 mA g⁻¹), excellent cycling stability (277 mAh g⁻¹ after 100 cycles at 200 mA g⁻¹, 79.6% capacity retention) and high rate capability (149.5 mAh g⁻¹ at 2 A g⁻¹). The results provide a facile approach to fabricate promising amorphous and ultrafine metal sulfides for energy storage.     

High lithium ion conducting Li2S–GeS2–P2S5 glass–ceramic solid electrolyte with sulfur additive for all solid-state lithium secondary batteries

Glass–ceramic Li₂S–GeS₂–P₂S₅ electrolytes were prepared by a single step ball milling (SSBM) process. Various compositions of Li_4−xGe_1−xP_xS₄ from x = 0.70 to x = 1.00 were systematically investigated. Structural analysis by X-ray diffraction (XRD) showed gradual increase of the lattice constant followed by significant phase change with increasing GeS₂. All-solid-state LiCoO₂/Li cells were tested by constant-current constant-voltage (CCCV) charge–discharge cycling at a current density of 50 μA cm⁻² between 2.5 and 4.3 V (vs. Li/Li⁺). In spite of the high conductivity of the solid-state electrolyte (SSE), LiCoO₂/Li cells showed a large irreversible reaction especially during the first charging cycle. Limitation of instability of Li₂S–GeS₂–P₂S₅ in contact with Li was solved by using double layer electrolyte configuration: Li/(Li₂S-P₂S₅/Li₂S–GeS₂–P₂S₅)/LiCoO₂. LiCoO₂ with SSEs heat-treated with elemental sulfur at elevated temperature exhibited a discharge capacity of 129 mA h g⁻¹ at the second cycle and considerably improved cycling stability.     

Electrochemical performance of high specific capacity of lithium-ion cell LiV3O8//LiMn2O4 with LiNO3 aqueous solution electrolyte

The electrochemical performance of aqueous rechargeable lithium battery (ARLB) with LiV₃O₈ and LiMn₂O₄ in saturated LiNO₃ electrolyte is studied. The results indicate that these two electrode materials are stable in the aqueous solution and no hydrogen or oxygen produced, moreover, intercalation/de-intercalation of lithium ions occurred within the range of electrochemical stability of water. The electrochemical performance tests show that the specific capacity of LiMn₂O₄ using as the cathode of ARLB is similar to that of ordinary lithium-ion battery with organic electrolyte, which works much better than the formerly reported. In addition, the cell systems exhibit good cycling performance. Therefore, it has great potential comparing with other batteries such as lead acid batteries and alkaline manganese batteries.     

High performance Li3V2(PO4)3/C composite cathode material for lithium ion batteries studied in pilot scale test

Li₃V₂(PO₄)₃/C composite cathode material was synthesized via carbothermal reduction process in a pilot scale production test using battery grade raw materials with the aim of studying the feasibility for their practical applications. XRD, FT-IR, XPS, CV, EIS and battery charge-discharge tests were used to characterize the as-prepared material. The XRD and FT-IR data suggested that the as-prepared Li₃V₂(PO₄)₃/C material exhibits an orderly monoclinic structure based on the connectivity of PO₄ tetrahedra and VO₆ octahedra. Half cell tests indicated that an excellent high-rate cyclic performance was achieved on the Li₃V₂(PO₄)₃/C cathodes in the voltage range of 3.0-4.3 V, retaining a capacity of 95% (96 mAh/g) after 100 cycles at 20C discharge rate. The low-temperature performance of the cathode was further evaluated, showing 0.5C discharge capacity of 122 and 119 mAh/g at −25 and −40 °C, respectively. The discharge capacity of graphite//Li₃V₂(PO₄)₃ batteries with a designed battery capacity of 14 Ah is as high as 109 mAh/g with a capacity retention of 92% after 224 cycles at 2C discharge rates. The promising high-rate and low-temperature performance observed in this work suggests that Li₃V₂(PO₄)₃/C is a very strong candidate to be a cathode in a next-generation Li-ion battery for electric vehicle applications.     

Enhanced high rate properties of ordered porous Cu2O film as anode for lithium ion batteries

Highly ordered porous Cu₂O film is electrodeposited on copper foil through a self-assembled polystyrene sphere template. Compared with the dense Cu₂O film and the octahedral Cu₂O powder, the ordered porous Cu₂O film exhibits an improved electrochemical cycling stability. The capacity of the porous Cu₂O film can maintain 336 mAh g⁻¹ and 213 mAh g⁻¹ after 50 cycles at the rate of 0.1 C and 5 C, respectively. The reversible capacity holds 63.4% as the discharge-charge rate even increases by 50 times. The enhanced high rate properties of the ordered porous film should be attributed to the sufficient contact surface of Cu₂O/electrolyte and the short diffusion length of Li⁺. Moreover, the direct contact between Cu₂O and current collector and the decreasing inactive interfaces of Cu₂O/polymer binder are also suggested as being responsible for the enhanced high rate property.