High-power Lithium-ion Batteries Research Articles

Ionic Conducting and Surface Active Binder of Poly (ethylene oxide)-block-poly(acrylonitrile) for High Power Lithium-ion Battery

In this work, poly(ethylene oxide)-block-poly(acrylonitrile) (PEO-b-PAN) copolymer is used as a binder for LiFePO4 cathodes, where PEO-b-PAN not only conducts Li+ inside the cathode but also acts as a dispersant to disperse LiFePO4. This binder significantly increases the capacity under high discharge rate and overcome the limitation of LiFePO4 for high power density application. By XPS analysis, the incorporation of the PEO-b-PAN binder to the active materials of the LiFePO4 cathodes can be clearly observed from the binding energy of the nitrogen atom of the PEO-b-PAN. Due to the surface active properties of the PEO and PAN, PEO-b-PAN obviously increases the effective contact area and reduces electronical resistance. In addition to the surface active properties, this binder provides Li+ pathway; thus, it features low polarization, less interfacial resistance and good activity for electrochemical reaction. Consequently, these properties enable the PEO-b-PAN binder to have a higher discharge plateau potential at 3.10V, while it is only 2.86V for the PVDF binder at a 5C rate. Moreover, even at a 10C rate, the PEO-b-PAN binder still delivers extraordinary discharge capacities of 101mAhg−1, significantly higher than that of the PVDF binder (32mAhg−1). Overall, this ionic conducting and surface active binder exhibits good electrochemical properties and excellent high rate performance.

Hierarchical carambola-like Li4Ti5O12-TiO2 composites as advanced anode materials for lithium-ion batteries

Hierarchically structured Li4Ti5O12-TiO2 (LTO-TiO2) composites are synthesized using a facile hydrothermal approach upon reaction time control. With control over the time of hydrothermal reaction at 18h, a hierarchical dual-phase LTO-TiO2 composite with appropriate amount of anatase TiO2 can be obtained, and it possesses a uniform carambola-like framework assembled by numerous ultrathin nanosheets, which enable a relatively large specific surface area, along with abundant interlayer channels to favor electrolyte penetration. When used as anode materials for lithium-ion batteries, such carambola-like LTO-TiO2 composite exhibits remarkably improved capacity, high-rate capability, and cycling stability over other LTO-TiO2 samples, which are synthesized at different time of hydrothermal reaction. Specifically, it deliveries a discharge capacity as high as 115.1 and 91.2mAhg−1at a very high current rate of 20 and 40C, respectively, while a stable reversible capacity of 171.7mAhg−1 can be retained after 200 charge-discharge cycles at 1C, corresponding to 88.6% capacity retention. The excellent electrochemical performances benefit from the unique hierarchical carambola-like structure together with the mutually complementary intrinsic advantages between LTO and TiO2. The robust and porous nanosheets-assembled LTO-TiO2 framework not only offers a shorter transport pathway for electron and Li-ion migration within this composite material, but also is able to alleviate the structure distortion during the fast Li-ion insertion/extraction process. The work described here shows that the hierarchical carambola-like LTO-TiO2 composite is a promising anode material for high-power and long-life lithium-ion batteries.

Morphological Evolution of High-Voltage Spinel LiNi(0.5)Mn(1.5)O4 Cathode Materials for Lithium-Ion Batteries: The Critical Effects of Surface Orientations and Particle Size.

An evolution panorama of morphology and surface orientation of high-voltage spinel LiNi(0.5)Mn(1.5)O4 cathode materials synthesized by the combination of the microwave-assisted hydrothermal technique and a postcalcination process is presented. Nanoparticles, octahedral and truncated octahedral particles with different preferential growth of surface orientations are obtained. The structures of different materials are studied by X-ray diffraction (XRD), Raman spectroscopy, X-ray absorption near edge spectroscopy (XANES), and transmission electron microscopy (TEM). The influence of various morphologies (including surface orientations and particle size) on kinetic parameters, such as electronic conductivity and Li(+) diffusion coefficients, are investigated as well. Moreover, electrochemical measurements indicate that the morphological differences result in divergent rate capabilities and cycling performances. They reveal that appropriate surface-tailoring can satisfy simultaneously the compatibility of power capability and long cycle life. The morphology design for optimizing Li(+) transport and interfacial stability is very important for high-voltage spinel material. Overall, the crystal chemistry, kinetics and electrochemical performance of the present study on various morphologies of LiNi(0.5)Mn(1.5)O4 spinel materials have implications for understanding the complex impacts of electrode interface and electrolyte and rational design of rechargeable electrode materials for lithium-ion batteries. The outstanding performance of our truncated octahedral LiNi(0.5)Mn(1.5)O4 materials makes them promising as cathode materials to develop long-life, high energy and high power lithium-ion batteries.

Performance evaluation of electrospun polyimide non-woven separators for high power lithium-ion batteries

The performance of polyimide (PI) non-woven separator used in high power lithium ion battery is investigated to evaluate the feasibility of its industrialized application. PI non-woven separator is prepared via an electrospinning method, and electrospinning process parameters are controlled to get a fibrous membrane consisting of bead-free, uniformly dispersed thin fibers with an average diameter of about 491nm. The as prepared separator with a porosity higher than 90% and relatively high electrolyte uptake exhibits excellent thermal stability without obvious shrinkage at 500°C, and shows sufficient tensile strength of 11MPa to meet the demand of battery assembly and usage. Laminated lithium-ion battery pack assembled with the PI non-woven separators shows a capacity retention ratio of about 33.6% at super high discharge rate of 28.8C, and the capacity remains 99.66% after 320 cycles at 5C rate, exhibiting excellent high-rate discharge capacity and favorable cycling performance, much superior to that of the battery pack assembled with the Celgard polyethylene (PE) separators. The results open great opportunities for the industrialized application of PI electrospun non-woven separator.

Online dynamic equalization adjustment of high-power lithium-ion battery packs based on the state of balance estimation

A novel concept named as state of balance (SOB) is proposed and its online dynamic estimation method is presented for the high-power lithium-ion battery (LIB) packs, based on which the online dynamic equalization adjustment is realized aiming to protect the operation safety of its power supply application. The core parameter detection method based on the specific moving average algorithm is studied because of their identical varying characteristics on the individual cells due to the manufacturing variability and other factors, affecting the performance of the high-power LIB pack. The SOB estimation method is realized with the detailed deduction, in which a dual filter consisting of the Unscented Kalman filter (UKF), equivalent circuit model (ECM) and open circuit voltage (OCV) is used in order to predict the SOB state. It is beneficial for the energy operation and the energy performance state can be evaluated online prior to the adjustment method based on the terminal voltage consistency. The energy equalization is realized that is based on the credibility reasoning together with the equalization model building process. The experiments including the core parameter detection, SOB estimation and equalization adjustment are done and the experimental results are analyzed. The experiment results show that the numerical Coulomb efficiency is bigger than 95%. The cell voltage measurement error is less than 5mV and the terminal voltage measurement error of the LIB pack is less than 1% FS. The measurement error of the battery discharge and charge maintenance current is less than 1% FS. The SOB estimation error is less than 5% in the laboratory room, the temperature of which is about 25°C. The equalization charging current is 2A and the equalization discharging current is 4.4A, which can realize the real-time energy equalization adjustment among the connected cells in the LIB pack, guaranteeing its safety in the power supply application.

Layer-by-Layer Polyelectrolyte Assisted Growth of 2D Ultrathin MoS2 Nanosheets on Various 1D Carbons for Superior Li-Storage

Transitional metal sulfide/carbon hybrids with well-defined structures could not only maximize the functional properties of each constituent but engender some unique synergistic effects, holding great promise for applications in Li-ion batteries and supercapacitors and for catalysis. Herein, a facile and versatile approach is developed to controllably grow 2D ultrathin MoS2 nanosheets with a large quantity of exposed edges onto various 1D carbons, including carbon nanotubes (CNTs), electrospun carbon nanofibers, and Te-nanowire-templated carbon nanofibers. The typical approach involves the employment of layer-by-layer (LBL) self-assembled polyelectrolyte, which controls spatially the uniform growth and orientation of ultrathin MoS2 nanosheets on these 1D carbons irrespective of their surface properties. Such unique structures of the as-prepared CNTs@MoS2 hybrid are significantly favorable for the fast diffusions of both Li-ions and electrons, satisfying the kinetic requirements of high-power lithium ion batteries. As a result, CNTs@MoS2 hybrids exhibit excellent electrochemical performances for lithium storage, including a high reversible capacity (1027 mAh g(-1)), high-rate capability (610 mAh g(-1) at 5 C), and excellent cycling stability (negligible capacity loss after 200 continuous cycles).

Additive-free synthesis of Li4Ti5O12nanowire arrays on freestanding ultrathin graphite as a hybrid anode for flexible lithium ion batteries

Vertically aligned Li4Ti5O12(LTO) nanowire arrays on freestanding ultrathin graphite (FSG) film were developed for lightweight, and high-power flexible lithium ion batteries. The combination of LTO and FSG is fully capable of exhibiting mechanical flexibility and good electrochemical performance.

Al2O3-modified Ti–Mn–O nanocomposite coated with nitrogen-doped carbon as anode material for high power lithium-ion battery

Al2O3-modified Ti–Mn–O nanocomposite coated with nitrogen-doped carbon using simple method exhibits remarkable rate performance.

Synthesis of Li4Ti5O12 nanoclusters for lithium-ion batteries with excellent electrochemical performances

Li4Ti5O12 nanoclusters are successfully prepared by a facile solution-based method and subsequent calcination. The influences of calcination temperatures on the microstructure and electrochemical performance of the products are studied. Results indicate that the sample annealed at 700°C exhibits outstanding rate performances and excellent long-term cycle stabilities. It displays a high initial Coulombic efficiency of 96.0% and a desirable discharge capacity of 176mAhg−1 at 0.1°C between 1.0 and 2.5V (vs. Li/Li+). The discharge capacity at 10°C is as high as 116mAhg−1 with capacity retention of 95.7% over 100cycles. Therefore, this Li4Ti5O12 nanocluster material can be a superior and practical candidate for the anodes of high-power lithium-ion batteries.

Synthesis and characterization of oriented linked LiFePO4 nanoparticles with fast electron and ion transport for high-power lithium-ion batteries

LiFePO4 nanoparticles with different morphologies and sizes were synthesized via a solvothermal method using environmentally benign and low-cost glycerol as the surfactant. The morphology, size, and structure of the particles were found to relate closely to the concentration of glycerol. Oriented linked LiFePO4 nanorods along mostly non-[010] were obtained with the proper concentration of glycerol. The nanorods showed good electronic and ionic conductivities, resulting in superior rate capability and cycling performance. This performance was attributed to the oriented linkages along mostly non–[010], the small particle size along [010], and the occupation of Li at Fe sites. Initial discharge capacities of 162.4 mA·h·g–1 at 0.1 C and 102.1 mA·h·g–1 at 30 C were achieved, with capacity retentions after 500 cycles at 5 and 20 C of 99.5% and 93.2%, respectively. At the rate of 40 C, the solid-solution phase transition dominated during lithiation and delithiation of all samples.

Polyethylene Oxide-Coated Electrospun Polyimide Fibrous Seperator for High-Performance Lithium-Ion Battery

A polyethylene oxide (PEO)-coated polyimide (PI) membrane was prepared by electrospinning method followed by a dip-coating and drying process for high-performance lithium-ion batteries (LIB). Semicrystal PEO was covered on the surface of the fibers and partially enmeshed in PI matrix, which formed unique porous structures. The pores with an average size of 4.1 µm and a porosity of 90% served as ion transport channels. Compared with the cell with Celgard 2400 membrane, the half-cell using PEO-coated PI membrane as a separator exhibits excellent electrochemical performance both at room temperature and at low temperature. The electrolyte uptaking rate of PEO-coated PI membrane was 170% and the ionic conductivity was 3.83 × 10–3 S cm–1. PEO-coated PI membrane possessed 5.3 V electrochemical window. The electrode–electrolyte interfacial resistance was 62.4 Ω. The capacity retention ratios with PEO-coated PI membrane were 86.4% at 5 C and 73.5% at 10 C at 25 °C and 75% at 5 C at 0 °C. Furthermore, the cell using the separator demonstrates excellent capacity retention over cycling. These advanced characteristics would boost the application of the PEO-coated PI membrane for high-power lithium ion battery.

Epicyanohydrin as an Interface Stabilizer Agent for Cathodes of Li-Ion Batteries

We investigated the effect of epicyanohydrin as an additive to a LiPF6 salt–based electrolyte in 1:1:1 EC:EMC:DMC for high-power lithium-ion batteries operated at 60°C. Epicyanohydrin polymerized to form a thermally stable, thin, conductive, and evenly distributed protective film on the cathode surface, preventing dissolution of the cathode material LiNi0.6Co0.2Mn0.2O2 and suppressing interfacial impedance, thereby protecting the surface from further reaction with the electrolyte at 60°C. The cycling performance of the cathode materials with the additive was enhanced due to the formation of an epicyanohydrin-derived polymer solid electrolyte interface (SEI).

Carbon-encapsulated LiMn2O4 spheres prepared using a polymer microgel reactor for high-power lithium-ion batteries

Carbon-encapsulated LiMn2O4 (LMO@C) spheres were prepared using polymer microgel reactor, in which Mn2+ ions are hydrolyzed in situ to form Mn(OH)2, and followed by annealing at a high temperature. The LMO@C spheres are constructed with the spinel LiMn2O4 nanospheres that embedded in a porous carbon matrix uniformly. Owing to possessing three-dimensional (3D) electron-conductive and 3D ion-conductive networks, the LMO@C spheres exhibit high rate capability. They can deliver the specific capacities of 142, 137, 126, 107, and 91 mAh g−1 at the rates of 0.1C, 1C, 5C, 10C, and 20C (1C = 148 mA g−1), respectively. Owing to carbon encapsulation, the LMO@C spheres can retain 80% of the initial capacity at 1C rate after 1000 cycles at 25 °C, displaying stable cycling performance. The results suggest that the LMO@C spheres are promising cathode materials for high-power lithium-ion batteries.

Vacuum induced self-assembling nanoporous LiMn2O4 for lithium ion batteries with superior high rate capability

Spinel LiMn2O4 is an inexpensive, eco-friendly and highly abundant cathode material for lithium ion batteries. Here, we report a synthesis of nanoporous LiMn2O4 cathode material using a simple vacuum induced self-assembly reaction. Ammonia molecules play a key role in the formation of the nanoporous structure in our method. The galvanostatic charge/discharge results show that the nanoporous LiMn2O4 delivers a high specific capacity at high power rates. About 95.9% of its initial capacity (94.5mAhg−1) is retained after 100 cycles at 10C. The enhanced kinetics of nanoporous LiMn2O4 with low apparent activation energies indicates that the nanoporous structure provides short Li-ion diffusion paths and a continuous three-dimensional network of pathways for the transport of Li-ions and electrons. These results reveal that the nanoporous spinel LiMn2O4 material is a promising cathode candidate for next generation of high-power lithium ion battery.

TiO2 Microboxes with Controlled Internal Porosity for High-Performance Lithium Storage.

Titanium dioxide (TiO2) is considered a promising anode material for high-power lithium ion batteries (LIBs) because of its low cost, high thermal/chemical stability, and good safety performance without solid electrolyte interface formation. However, the poor electronic conductivity and low lithium ion diffusivity of TiO2 result in poor cyclability and lithium ion depletion at high current rates, which hinder them from practical applications. Herein we demonstrate that hierarchically structured TiO2 microboxes with controlled internal porosity can address the aforementioned problems for high-power, long-life LIB anodes. A self-templating method for the synthesis of mesoporous microboxes was developed through Na2 EDTA-assisted ion exchange of CaTiO3 microcubes. The resulting TiO2 nanorods were organized into microboxes that resemble the microcube precursors. This nanostructured TiO2 material has superior lithium storage properties with a capacity of 187 mAh g(-1) after 300 cycles at 1 C and good rate capabilities up to 20 C.

High rate performance of LiNi1/3Co1/3Mn1/3O2 cathode material synthesized by a carbon gel–combustion process for lithium ion batteries

The LiNi1/3Co1/3Mn1/3O2 electrode material was prepared via a carbon gel–combustion process using resorcinol–formaldehyde gel as fuel and nitrate as an oxidizer. The carbon gel process ensures the molecular-level homogeneity of the chemical product. The gas derived from carbon gel separates the raw material particles and restrains the growth of the grains to some extent, and well-crystallized nanosized powders are obtained with calcination at 700°C for 6h. As the cathode material for lithium-ion batteries, the discharge capacity of LiNi1/3Co1/3Mn1/3O2 was as high as 175.6mAhg−1 in the first cycle at 0.5C, and it could remain 163.0mAhg−1 within the voltage range of 2.5–4.4V after 50 cycles. The electrode also showed outstanding rate capacities at high discharge rates such as 30C and 50C, suggesting the applications of the material in high power lithium-ion batteries.

LiNi0.5Mn1.5O4 Cathodes for Lithium Ion Batteries: A Review.

Spinel structured LiNi0.5Mn1.5O4 based compounds are promising cathode materials for high power lithium ion batteries, owing to its superior 4.7 V discharge plateau and large reversible capacity. However, its pace of commercialization is hindered by limited rate capability, poor cyclic performance at high current densities and instability with electrolyte. Extensive works have been devoted to tackle these difficulties. This paper presents a review of challenges and recent developments of LiNi0.5Mn1.5O4 based compounds.

Synthesis of hierarchical conductive C/LiFePO4/carbon nanotubes composite with less antisite defects for high power lithium-ion batteries

The low electronic conductivity and Li ion diffusion ability are two major obstacles to realize its wide application for LiFePO4 materials. The material with hierarchical conductive structure and lower antisite defects concentration can effectively enhance the electronic conductivity and Li ion diffusion ability. We firstly report here a modified solvothemal process for the fabrication of hierarchical conductive C/LiFePO4/CNTs composite with less antisite defects. It is found that the modified solvothemal process is facilitated to decrease FeLi antisite defects and enhance the electronic continuity between LFP and CNTs. In favor of its unique properties, the C/LFP/CNTs composites can deliver superior rate capability and cycling stability. Remarkably, even at a high rate of 20C (3400mAg−1), a high initial discharge capacity of 91.6mAhg−1 and good cycle retention of 95% with almost 100% coulombic efficiency are still obtained after 100 cycles.

Thermal management improvement of an air-cooled high-power lithium-ion battery by embedding metal foam

Effect of embedding aluminum porous metal foam inside the flow channels of an air-cooled Li-ion battery module was studied to improve its thermal management. Four different cases of metal foam insert were examined using three-dimensional transient numerical simulations. The effects of permeability and porosity of the porous medium as well as state of charge were investigated on the standard deviation of the temperature field and maximum temperature inside the battery in all four cases. Compared to the case of no porous insert, embedding aluminum metal foam in the air flow channel significantly improved the thermal management of Li-ion battery cell. The results also indicated that, decreasing the porosity of the porous structure decreases both standard deviation of the temperature field and maximum temperature inside the battery. Moreover, increasing the permeability of the metal foam drops the maximum temperature inside the battery while decreasing this property leads to improving the temperature uniformity. Our results suggested that, among the all studied cases, desirable temperature uniformity and maximum temperature were achieved when two-third and the entire air flow channel is filled with aluminum metal foam, respectively.

Highly Reversible Lithium‐ions Storage of Molybdenum Dioxide Nanoplates for High Power Lithium‐ion Batteries

Herein, MoO2 nanoplates have been facilely prepared through a hydrothermal process by using MoO3 microbelts as the intercalation host. The obtained MoO2 nanoplates manifest excellent electrochemical properties when the discharge cutoff voltage is simply set at 1.0 V to preclude the occurrence of conversion reactions. Its initial reversible capacity reaches 251 mAh g(-1), which is larger than that of Li4Ti5O12 , at a current rate of 0.2 C. The average capacity decay is only 0.0465 mAh g(-1) per cycle, with a coulombic efficiency of 99.5% (from the 50th cycle onward) for 2000 cycles at 1 C. Moreover, this MoO2 electrode demonstrates an outstanding high power performance. When the current rate is increased from 0.2 to 50 C, about 54% of the capacity is retained. The superior electrochemical performance can be attributed to the metallic conductivity of MoO2, short Li(+) diffusion distance in the nanoplates, and reversible crystalline phase conversion of the addition-type reaction of MoO2. The prepared MoO2 nanoplates may hopefully replace their currently used analogues, such as Li4Ti5O12 , in high power lithium-ion batteries.