Rate Performance For Lithium Ion Batteries Research Articles

Porous Carbon Spheres Doped with Fe3C as an Anode for High-Rate Lithium-ion Batteries

The search of advanced anodes has been an important way to satisfy the ever-growing demands on high rate performance lithium-ion batteries (LIBs). It was observed that the capacity of Fe3C as an anode is larger than its theoretical one, which might be attributed to the pseudocapacity on the interface between the carbide and electrolyte. In this work, a novel carbon sphere doped with Fe3C nanoparticles was fabricated and tested as the anode in LIBs. In the first place, iron precursors were embedded in the cross-link polymer resorcinol-formaldehyde (RF) spheres via a facile hydrothermal reaction, in which RF served as the carbon source and ethanol as a dispersant agent. Consequently, the hydrothermal products were carbonized successively at 700°C under inert atmosphere to obtain porous carbon spheres doped with Fe3C. When the composite severed as an anode in LIBs, its discharge capacity increased to the largest during the first 250-400 cycles, then dropped down to a similar level of that after 1000 cycles at different current rates. The discharge capacity of the composite increased from ∼300mAhg−1 to ∼540mAhg−1 at the current of 100mAg−1 during the initial hundreds cycles, and even a discharge capacity of ∼230mAhg−1 at the current of 2000mAg−1. Moreover, it was observed that a discharge plateau gradually appeared between 0.7∼1.1V during the first hundreds of cycles. The electrochemical behaviors of the anode before 1000 discharge/charge cycles were compared with that after 1000 discharge/charge cycles by cyclic voltammetry and electrochemical impedance spectroscopy to find out the differences between their features. The high rate performance of LIBs might result from the decomposition of electrolyte and the pseudocapacity behavior presented on the interfacial (surface) lithium storage of the active materials.

Block-shaped pure and doped Li4Ti5O12 containing a high content of a Li2TiO3 dual phase: an anode with excellent cycle life for high rate performance lithium-ion batteries

A pure lithium titanate composite sample is a promising anode for high rate performance lithium ion batteries.

Ru0.01Ti0.99Nb2O7 as an intercalation-type anode material with a large capacity and high rate performance for lithium-ion batteries

Ru0.01Ti0.99Nb2O7, with a much larger capacity than Li4Ti5O12, fulfils the requirements of high power and energy density for electric vehicles.

Ge@C core–shell nanostructures for improved anode rate performance in lithium-ion batteries

The Ge@C core–shell nanostructures exhibit excellent cycling performance and rate capability as an electrode material for lithium ion batteries.

Effect of different carbon sources on electrochemical properties of Li2ZnTi3O8/C anode material in lithium-ion batteries

Pristine Li2ZnTi3O8 and Li2ZnTi3O8/C composites are prepared by a modified solid-state reaction with TiO2, Li2CO3, Zn(CH3COO)2·2H2O and carbon sources (sucrose, oxalic acid, citric acid) as reactants. The crystal structure and morphology of products are systematically investigated by XRD, SEM, HR-TEM, TG and laser particle size analyzer. The sucrose coated Li2ZnTi3O8 composite electrode embodied high electrochemical performance in terms of high capacities (286.5, 214.9, 177.8, 112.5mAhg−1 at current densities of 0.1, 0.5, 1.0, 2.0Ag−1, respectively), which obviously is higher than that of oxalic acid or citric acid coated Li2ZnTi3O8 and pure Li2ZnTi3O8. All as-prepared samples show fairly stable cycling performance. The likely contributing factors to the excellent electrochemical performance of sucrose coated Li2ZnTi3O8 composite could be related to the amorphous carbon layer and carbon network structure (“Conductive Bridge”), which can decrease particle diameter, avoid side reactions at the interfacial contact area of electrode and electrolyte, and enhance electronic conductivity. This research suggests that sucrose coated Li2ZnTi3O8 composite be an alternative anode material with remarkable rate performance for lithium-ion batteries.

Electrodeposited Three-Dimensional Porous Silicon Nanostructure with Excellent Stability and High Rate Performance for Lithium-Ion Batteries

Recently, rechargeable lithium ion batteries with higher energy/power densities and better rate performance have been widely developed to be used for powering future portable electronic devices and for application to renewable energy storage facilities and in electric vehicles (EVs)[1]. Silicon is one of the most promising anode candidates owing to its extremely high theoretical capacity of 4200 mAh/g (with the formation of the Li4.2Si alloy), which is more than 10 times higher than the capacity of graphitic carbon (372 mAh/g) and other Li alloys.[2] Due to a major volume change (300-400%) of Si during the lithiation/delithiation processes, the resulting pulverization and a loss of electrical connection between the active materials and the electrode framework cause serious irreversible capacity loss and poor cyclability. In order to solve the pulverization issues of Si, we have fabricated 3D porous Si/metal (copper or nickel) film by an electrodeposition method using two types of template; one is a hydrogen gas bubble template and the other is inverse opal template. Compared with chemical vapor deposition or etching method for porous 3D Si anode, electrodepostion method is a simple and low-cost method which is used for large scale operation in industry.[3] Our 3D porous silicon/metal anode with a well-defined configuration for lithium ion batteries consists of interconnected metal film, which not only allows for robustness during the charge and discharge process with the volume expansion but enables the formation of a large area for silicon electrodeposition at a high capacity in lithium ion batteries. The resulting self-supported 3D porous Si/metal electrodes exhibit a high reversible capacity (2824 mAh/g), remarkable cycling stability (1628 mAh/g after 100 cycles) and superior rate capability without any binder or conductive additives. The results using the 3D porous Si/metal anode in our study represent a promising approach for high-performance silicon-based anodes which are compatible with scaled-up manufacturing process for next-generation lithium-ion batteries due to their simple and rapid fabrication process.[1] J. Maier, Nature Materials, 2005, 4, 805.[2] B. A. Boukamp, G. C. Lesh, R. A. Huggins, Journal of Electrochemical Society, 1981, 128, 725.[3] Y. Nishimura, Y. Fukunaka, Electrochimica Acta, 2007, 53, 111.

Anodic Rate Performance in Lithium-Ion Batteries of Graphite Materials Based on Carbonaceous Wastes

The rate performance as anode in lithium-ion batteries of two graphite materials denoted A/CVP/2700 and B/CIQ5/2600 that were prepared by high temperature heat-treatment of carbonaceous wastes from coal combustion fly ashes is herein investigated using galvanostatic cycling at increasing electric current densities (C/20–2C charge-discharge interval rate) and subsequent electrochemical impedance spectroscopy (EIS). These materials show a remarkable stable capacity along cycling with capacity retention values >90% as well as an excellent efficiency of cycling (discharge/charge capacity ratio close to 100%) in the whole interval of rates studied and a significant resistance to aging. Provided they have a graphite-like structure as evaluated by XRD and Raman spectroscopy, the excellent rate capability appears to be also related to the small size and irregular shape of the particles which, respectively, improve the diffusion of the lithium ions in the electrode bulk and reduce the lithium migration resistances as confirmed by the EIS results. Furthermore, the capacities delivered by A/CVP/2700 and B/CIQ5/2600 materials at any rate were larger than those of the reference graphite with much larger development of the crystalline structure, which is commercialized for anodes of LIBs.

Electrodeposited 3D porous silicon/copper films with excellent stability and high rate performance for lithium-ion batteries

We report a simple two-step fabrication process of 3D porous Si/copper films by an electrodeposition method using a hydrogen gas bubble template. A 3D porous Si/copper film provides a large surface area, a highly conductive pathway, a short ion diffusion length, and buffer spaces to accommodate the stress during the cycling processes.

Microwave rapid preparation of LiNi0.5Mn1.5O4 and the improved high rate performance for lithium-ion batteries

Spinel LiNi0.5Mn1.5O4 is rapidly synthesized by using microwave heating at 700°C for 7min (MW700C7m). The crystal structure, morphology and elemental deficiency of MW700C7m are carefully studied by Rietveld refinement of XRD patterns, scanning and transmission electron microcopy, and redox titration, in comparison with the sample synthesized by conventional heating at 700°C for 48h (CP700C48h). Both MW700C7m and CP700C48h are well refined using the Fd-3m space group. Microwave irradiation not only accelerates the crystal growth of spinel LiNi0.5Mn1.5O4, but also results in preferential growth behavior. Cyclic voltammetry (CV) of MW700C7m presents low polarization and better structural stability. Galvanostatic charge–discharge cycling of MW700C7m and CP700C48h have minor Mn3+/4+ redox peaks beside Ni2+/4+ redox peaks. At normal current rate, both MW700C7m and CP700C48h present good capacities, close to the theoretical value. At high current rate, MW700C7m delivers much better capacity than CP700C48h. MW700C7m delivers capacity of 108.7mAhg−1 at 10C-rates and fades less than 1% after 150 cycles. The severe capacity loss of LiNi0.5Mn1.5O4 cathodes is still a problem when cycling is carried out at high and low temperatures. Under various temperatures, the contribution and effect of Mn3+/4+ and Ni2+/4+ redox for the capacity are studied in detail.

New facile synthesis of TiO2 hollow sphere with an opening hole and its enhanced rate performance in lithium-ion batteries

With the aid of the slow release of water from esterification reactions, a simple one-step solvothermal method was developed to prepare TiO2 hollow spheres with an opening hole. Organic carboxylic acids (CA) were exploited as not only the reactant to conduct esterification with ethanol, but also the coordination agent to modify titanium n-butoxide (TNB) to manipulate its hydroxylation and condensation process. The specific TiO2 morphologies prepared by this CA-assisted method significantly depend on the molecular structure and relative concentration of the carboxylic acids used. Appropriate carbon chain length of the CA molecule and the optimal molar ratio of CA/TNB are the essential factors to fabricate well-developed TiO2 hollow spheres with an opening hole. The surface hole facilitates active material transportation into the hollow interior, so this structure of TiO2 has been utilized in lithium-ion batteries and exhibits superiority in rate performance compared to closed spheres.

In situ self-catalyzed formation of core–shell LiFePO4@CNT nanowires for high rate performance lithium-ion batteries

In situ self-catalyzed core–shell LiFePO4@CNT nanowires can be fabricated by a two-step synthesis, where one-dimensional LiFePO4 nanowires with a diameter of 20–30 nm were encapsulated into CNTs, and 3D conducting networks of CNTs were obtained from in situ carbonization of a polymer. LiFePO4@CNT nanowires deliver a capacity of 160 mA h g−1 at 17 mA g−1, and 65 mA h g−1 at 8500 mA g−1 (50 C, 1.2 minutes for charging and 1.2 minutes for discharging).

Charge Transfer Reactions in Lithium-ion Batteries

We have studied the charge transfer reactions at electrode/electrolyte interfaces in lithium-ion batteries and found that there exist large activation barriers at the interface for lithium-ion to insert and extract at the electrodes. By the theoretical calculation, the activation barriers were found to be correlated with the interaction between lithium-ion and solvent in electrolyte, and therefore, the activation barriers are principally due to the de-solvation process of lithium-ion in the electrolyte. These results are also confirmed by the model interface consisted of electrolyte/electrolyte. Based on these results, we discuss how the rate performance of lithium-ion batteries will be enhanced.