Specific Capacity Of Battery Research Articles

Improvement of specific capacity of lithium iron phosphate battery by increasing the surface area and electrical conductivity of cathode electrode using graphene foam

Lithium iron phosphate (LFP) is widely used as an active material in a cathode electrode for lithium-ion batteries (LIBs). LFP has many remarkable properties such as high working voltage and excellent thermal stability. However, it suffers with slow ion diffusion and low electrical conductivity. Graphene foam has many outstanding properties such as large surface area and great electrical conductivity. These properties are suitable for improving the cathode electrode. In this work, the graphene foam was synthesized by chemical vapor deposition. The cathode electrode was prepared by dropping the LFP on the graphene foam. We found that the specific capacity of battery which contained the LFP between the anode and the graphene foam (LFP/GF) was 23.1 mAh⸳g-1 at 3C, while the specific capacity of battery which contained the graphene foam between the anode and the LFP (GF/LFP) was 112.6 mAh⸳g-1 at 3C. The diffusion coefficients of Li+ of GF/LFP was 9.1 times higher than that of LFP/GF. The specific capacity of GF/LFP was higher than that of LFP/GF at high current density due to the high ion transfer rate which arises from the graphene foam.

Graphite/Li2ZrO3 anode for a LiFePO4 battery

Lithium zirconate, Li2ZrO3 (LZO), was added to graphite anode at various compositions of 0%, 20%, and 30% of weight, and used in a LiFePO4 (LFP) battery fabrication. The battery cells were designated as LFP//G, LFP//20LZOG, and LFP//30LZOG, respectively. Herein, battery performance was tested to understand LZO contribution to the LFP cathode at different current rates. The data taken were specific capacity of battery, anodic current density, and a crystallite volume change after 50 cycles of charge–discharge. The result found that addition of 20% weight LZO to graphite increases discharge specific capacity after 50 cycles from 71.87 to 72.53 mAhg−1 with Coulombic efficiency of 99.73%. The capacity retention is 62.1%, which is higher than LFP//G, i.e., 57.7%. The anodic current density of LFP//20LZOG is 9.09 × 10−6 Acm−2, also higher than the current density of LFP//G, i.e., 8.91 × 10−8 Acm−2. It indicates contribution of LZO to increase electrochemical reaction rate during battery usage. Structural investigation shows that the LZO addition decreases the volume change of anode material after 50 cycles of charge–discharge under 1C current rate. It indicates that Li2ZrO3 has good structural stability.

Enhanced cycling performance for all-solid-state lithium ion battery with LiFePO4 composite cathode encapsulated by poly (ethylene glycol) (PEG) based polymer electrolyte

The poor contact between the cathode and the solid polymer electrolyte (SPE) is one of the primary causes for the low specific capacities of lithium ion batteries. In this work, a composite cathode material containing LiFePO4 nanoparticles encapsulated by PEG-based polymer electrolyte (coated LiFePO4) are prepared in order to increase the interfacial contact area between SPE and cathode materials. The LiFePO4/SPE/Li half-cell battery with coated LiFePO4 (C-LFP) and uncoated LiFePO4 (U-LFP) are assembled and their electrochemical performances are studied. The optimal LiFePO4/SPE weight ratio in the composites cathode is 60/15. When the cathode thickness is 100 μm, the specific capacity of battery with C-LFP can reach up to 138 mAhg−1, which is 2.5 times higher than that with U-LFP under 1C charge-and-discharge rate at 60 °C. Moreover, the capacity retention of C-LFP is 91% after 300 cycles, while that of U-LFP is only 18%. Large cracks emerge in the cathode with U-LFP, while no damage can be found in that with C-LFP after 300 cycles at 1C. This should be ascribed to the existence of polymer buffer layers among LiFePO4 nanoparticles to alleviate the stress induced by their volume changes during the charge-and-discharge cycling process. This enhancement effect increases along with the increase of cathode thickness. When the cathode thickness increases up to 200 μm, the specific capacity of battery with C-LFP cathode is almost 4 times higher than that with U-LFP.

Enchanced electrochemical performances of Li4Ti5O12/Sn composites anode via sol-hydrothermal method for lithium ion batteries

Li4Ti5O12 (lithium titanate) were synthesized by sol-gel and hydrothermal method with LiOH as lithium ion source. Li4Ti5O12/Sn composites anode were preparared by ball mill method with three of Sn variation. X-ray diffraction shows spinel, TiO2, and Sn phases with anatase and rutile residue. The lowest electrolyte resistance obtained at the highest Sn value. The specific capacity of battery can be increased from addition of Sn by up to 258.6 mAh/g. Alloying and dealloying reaction of LixSn accomodate the increased specific capacity from charge/discharge. However, Thevolume expansion from LixSn leads to loss of capacity when the C rate increases. The efficient capacity at low and high charge-discharge rate obtained at the highest value of added Sn.

Single Step Synthesis of High-Purity CoO Nanocrystals

Both octahedral and slice-shaped cubic cobalt monoxide (CoO) nanocrystals with narrow size distributions have been successfully synthesized by a simple solvothermal route. It was found that conditions of the solvothermal treatment showed obvious effects on the formation and purity of the as-synthesized CoO nanocrystals, only when cobalt acetate was used as the cobalt source and when temperature reached 190 degrees C could CoO be produced; also, freeze-drying was necessary for obtaining pure CoO. Size of the CoO nanocrystals varied from 30 to 130 nm. Morphology of the products could be controlled by simply changing the type of surfactant in solvent, and the octahedral CoO nanocrystals showed rounded turns. Purity of the products was detected by intensive X-ray photoelectron spectroscopy (XPS) investigation and Fourier transform infrared spectroscopy (FTIR) combined with differential scanning calorimetry/thermal gravity (DSC/TG). The results indicated an absence of unexpected trivalence cobalt series on surface of the samples, thanks to the protection of the surface by trace amount of carbonate ions, adsorbed hydroxylation, and surfactant with a maximum thickness of 2 nm, which were proved by high-resolution transmission electron microscopy (HRTEM). The as-synthesized CoO nanoparticles were added into positive electrode of Ni/MH batteries, and discharge/charge cycling tests were performed under different rates from 0.1C to 5.0C. The results indicated that the specific capacities of batteries with addition of 5% octahedral or slice CoO nanocrystals at 0.1C were 393.3 and 318.1 mAh/g, respectively, which were higher than that without CoO (269.2mAh/g). Specific capacity of battery with addition of 5% octahedral CoO nanocrystals was 40% higher than that without CoO at 5.0C. Octahedral CoO nanocrystals show better electrochemical activity than slice CoO and indicate interesting potential in the field of electrochemical application.