Chenfeng Guo

Improvement of the electrochemical performance of carbon-coated LiFePO4 modified with reduced graphene oxide

In this work, carbon-coated LiFePO4 was further modified with reduced graphene oxide (RGO) using an ultrasonic-assisted rheological phase method coupled with carbothermal treatment. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and electrochemical methods were used to characterize the materials properties. The results showed that the composite material consisting of carbon-coated LiFePO4 and RGO sheets possesses a unique and effective three-dimensional “sheet-web” structure. In the structure, the LiFePO4 particle size can be maintained at nanosize to form abundant voids between the nanoparticles while the RGO sheets are significantly beneficial for Li+ diffusion. As a result, the electrochemical properties of the composite material have been greatly improved. A sample with 5 wt% RGO exhibited high specific capacity and superior rate performance with the discharge capacities of 160.4 mA h g−1 at 0.2 C and 115.0 mA h g−1 at 20 C. The sample also showed an excellent cycling stability with only about 10% capacity decay at 10 C after 1000 cycles.

A three dimensional SiOx/C@RGO nanocomposite as a high energy anode material for lithium-ion batteries

A co-modification strategy to improve the electrode performance of SiO-based materials through the use of a carbon coating layer and reduced graphene oxide (RGO) network has been developed. The as-synthesized SiOx/C@RGO nanocomposites showed excellent specific capacity, cycling performance and rate capability when used as an anode in lithium-ion batteries.

The composite electrode of LiFePO4 cathode materials modified with exfoliated graphene from expanded graphite for high power Li-ion batteries

In recent years, copious papers have reported the fruitful modifications of LiFePO4-based composites and exhibited excellent electrochemical performance in terms of rate capability and cycling stability. Besides, the optimization of bulk electrodes are essential to keep pace with composites, by enhancement of the electronic and ionic transport to further improve the power performance of an electrode. Therefore, in this work, a facile strategy is adopted to fabricate a composite electrode with NMP as a solvent, containing large-size multilayer graphene, which is prepared by the exfoliation of economical expanded graphite under high power ultrasound in isopropyl alcohol. Active LiFePO4 nanograins, as well as conductive additives, are attached to the superior conductive graphene and thereby fast pathways are established as a “highway” for electronic transport in the bulk electrode. As a result, this composite electrode exhibits a lower polarization at high-rate charge–discharge processes. The operating flat voltage of 20 C rate is maintained at more than 3.0 V in one minute and its discharge capacity is up to 107.8 mA h g−1, representing a better energy density and power density.

Carbon-coated single-crystalline LiFePO4 nanocomposites for high-power Li-ion batteries: the impact of minimization of the precursor particle size

In this work, a high-energy ball mill technique is designed to deal with bulk precursors and achieve particle size minimization. A large amount of the nano-sized precursor is achieved in a narrow particle size distribution of ca. 95 nm. We confirm that the dimensional size of the precursor has a significant influence on the final LiFePO4 particle size and that small grains of the precursor probably form single-crystalline nanoparticles during the calcination process. After carbothermal reduction, the carbon-coated single-crystalline LiFePO4 nanocomposites (nano-CS–LFP) are easily synthesized. Benefiting from the decreasing particle size, the specific surface area of nano-CS–LFP is up to 48.0 m2 g−1, which implies a higher interfacial contact area between the active particles and the electrolyte, as well as an increase in its capacitance capability. Besides, cyclic voltammetry curves of nano-CS–LFP reveal a better capability of reversible reactivity and a lower polarization. Galvanostatic charge–discharge results exhibit excellent rate performance with a discharge capacity of ca. 100 mA h g−1 at 10 °C and a stable cycling property with a capacity retention of ca. 90% after 1000 cycles. In addition, the rapid charge–discharge test over 60 seconds indicates an excellent pulse performance with a high current in a short time period. The combination of the merits of carbon coating and particle size minimization is responsible for the above improvements. Finally, this facile preparation strategy is favorable for the industrial production of economical LiFePO4 materials from lab synthesis.

Corrosion resistance of nickel foam modified with electroless Ni–P alloy as positive current collector in a lithium ion battery

We provide a novel and facile idea to enhance the corrosion resistance of nickel foam and improve the life of a positive current collector in an electrolyte containing LiPF6 salt. The crystal Ni–P alloy was prepared via an electroless Ni–P technique, combined with subsequent thermal treatment. The as-prepared crystal alloy coatings exhibit excellent stability at high operating voltages as positive current collectors in lithium ion batteries.

Nitrogen-doped carbon coated SiO nanoparticles Co-modified with nitrogen-doped graphene as a superior anode material for lithium-ion batteries

One great challenge in the development of lithium-ion batteries is to simultaneously achieve superior reversible specific capacity, cyclic life and rate capability. In this work, nitrogen-doped carbon coated Silicon monoxide nanoparticles further co-modified with nitrogen-doped graphene were developed. The nanostructure of Silicon monoxide was designed and realized by introducing the highly efficient attritor mill technique, which assisted in forming optimized morphology and particle size distributions of the precursor. The nitrogen-doped carbon coating process was achieved by a simple surface coating technique using a carbon and nitrogen containing ionic liquid as a precursor, and the nitrogen-doped graphene was prepared by a facile, catalyst-free thermal annealing approach using low-cost industrial material melamine as the nitrogen source. XRD, XPS, RAMAN, FESEM, EDAX, TEM, HRTEM, AFM, BET, elemental analysis, electrical conductivity measurement and electrochemical methods were used to characterize the materials properties. The results showed that the reduced active particle size, coupled with the co-modification of the NC coating layer and NG network could effectively construct a 3D conducting network through a 3D “sheet-web” mode. As a result, the composite material showed exceptional high reversible specific capacity, ultra long cyclic life and superior high-rate capability. The present strategy opens up the possibility for integrating other anode materials with large volume variations and low electrical conductivities into current lithium-ion battery manufacture technology.

A three-dimensional multilayered SiO–graphene nanostructure as a superior anode material for lithium-ion batteries

A Three-dimensional (3D) multilayered nanostructure to improve the electrode performance of SiO-based material through the use of reduced graphene oxide (RGO) film and a Ni foam substrate has been developed. The lithium storage performance of the prepared anode is evaluated by electrochemistry measurements. The as-synthesized 3D SiO–RGO nanostructures showed excellent electrochemistry properties as an anode in lithium-ion batteries.

Improvement of the electrochemical performance of carbon-coated LiFePO4modified with reduced graphene oxide

In this work, carbon-coated LiFePO4 was further modified with reduced graphene oxide (RGO) using an ultrasonic-assisted rheological phase method coupled with carbothermal treatment. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and electrochemical methods were used to characterize the materials properties. The results showed that the composite material consisting of carbon-coated LiFePO4 and RGO sheets possesses a unique and effective three-dimensional “sheet-web” structure. In the structure, the LiFePO4 particle size can be maintained at nanosize to form abundant voids between the nanoparticles while the RGO sheets are significantly beneficial for Li+ diffusion. As a result, the electrochemical properties of the composite material have been greatly improved. A sample with 5 wt% RGO exhibited high specific capacity and superior rate performance with the discharge capacities of 160.4 mA h g−1 at 0.2 C and 115.0 mA h g−1 at 20 C. The sample also showed an excellent cycling stability with only about 10% capacity decay at 10 C after 1000 cycles.

Improvement of the electrochemical performance of carbon-coated LiFePO 4 modified with reduced graphene oxide

In this work, carbon-coated LiFePO4 was further modified with reduced graphene oxide (RGO) using an ultrasonic-assisted rheological phase method coupled with carbothermal treatment. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and electrochemical methods were used to characterize the materials properties. The results showed that the composite material consisting of carbon-coated LiFePO4 and RGO sheets possesses a unique and effective three-dimensional “sheet-web” structure. In the structure, the LiFePO4 particle size can be maintained at nanosize to form abundant voids between the nanoparticles while the RGO sheets are significantly beneficial for Li+ diffusion. As a result, the electrochemical properties of the composite material have been greatly improved. A sample with 5 wt% RGO exhibited high specific capacity and superior rate performance with the discharge capacities of 160.4 mA h g−1 at 0.2 C and 115.0 mA h g−1 at 20 C. The sample also showed an excellent cycling stability with only about 10% capacity decay at 10 C after 1000 cycles.