High-power Lithium-ion Batteries Research Articles

Effect of SiO₂ Nanoparticles on the Performance of PVdF-HFP/Ionic Liquid Separator for Lithium-Ion Batteries.

Safety concerns related to the use of potentially explosive, liquid organic electrolytes in commercial high-power lithium-ion batteries are constantly rising. One promising alternative is to use thermally stable ionic liquids (ILs) as conductive media, which are however, limited by low ionic conductivity at room temperature. This can be improved by adding fillers, such as silica or alumina nanoparticles (NPs), in the polymer matrix that hosts the IL. To maximize the effect of such NPs, they have to be uniformly dispersed in the matrix while keeping their size as small as possible. In this work, starting from a water dispersion of silica NPs, we present a novel method to incorporate silica NPs at the nanoscale level (<200 nm) into PVdF-HFP polymer clusters, which are then blended with the IL solution and hot-pressed to form separators suitable for battery applications. The effect of different amounts of silica in the polymer matrix on the ionic conductivity and cyclability of the separator is investigated. A membrane containing 10 wt.% of silica (with respect to the polymer) was shown to maximize the performance of the separator, with a room temperature ionic conductivity of of 1.22 mS cm. The assembled half-coin cell with LiFePO and Li as the cathode and the anode exhibited a capacity retention of more than 80% at a current density of 2C and 60 C.

A novel endurance prediction method of series connected lithium-ion batteries based on the voltage change rate and iterative calculation

High-power lithium-ion battery packs are widely used in large and medium-sized unmanned aerial vehicles and other fields, but there is a safety hazard problem with the application that needs to be solved. The generation mechanism and prevention measurement research is carried out on the battery management system for the unmanned aerial vehicles and the lithium-ion battery state monitoring. According to the group equivalent modeling demand of the battery packs, a new idea of compound equivalent circuit modeling is proposed and the model constructed to realize the accurate description of the working characteristics. In order to realize the high-precision state prediction, the improved unscented Kalman feedback correction mechanism is introduced, in which the simplified particle transforming is introduced and the voltage change rate is calculated to construct a new endurance prediction model. Considering the influence of the consistency difference between battery cells, a novel equilibrium state evaluation idea is applied, the calculation results of which are embedded in the equivalent modeling and iterative calculation to improve the prediction accuracy. The model parameters are identified by the Hybrid Pulse Power Characteristic test, in which the conclusion is that the mean value of the ohm internal resistance is 20.68 mΩ. The average internal resistance is 1.36 mΩ, and the mean capacitance value is 47747.9F. The state of charge prediction error is less than 2%, which provides a feasible way for the equivalent modeling, battery management system design and practical application of pack working lithium-ion batteries.

Investigation of carbon-decorated LiVPO4F nanoparticles as cathode for lithium-ion batteries with enhanced rate capability and cyclic performance

Polyanion-type LiVPO4F has been regarded as a potential candidate of cathode material for lithium-ion batteries due to its high working voltage, excellent thermal stability and good safety. However, the pure LiVPO4F has a low electronic conductivity of 10−11 S cm−1, which greatly limits its application in high-power density batteries. In this research, the core-shell carbon-coated LiVPO4F composite is prepared using a facile sol-gel method followed by a solid-state reaction. Owing to the synergistic effects rendered by the LiVPO4F nanoparticles and conductive carbon coating, the as-prepared composite exhibits high reversible capacity (147.9 mAh g−1 at 0.1 C), excellent rate capability (121.2 mAh g−1 at 5 C) and stable cyclic performance (94% capacity retention after 200 cycles at 2 C). These results reveal that the carbon-coated LiVPO4F material is a promising cathode material for high-power lithium-ion batteries.

Li4Ti5O12 nanosheets assembled in tubular architecture for lithium storage

Owing to their fantastic structural advantages of large surface area and shortened Li+/electron transport pathway, hierarchical tubular nano-/micro-materials have attracted much attention as the anodes used in lithium-ion batteries (LIBs). However, rational design and simple fabrication of hierarchical tubular structures assembled by non-particulate nanoscale building blocks still face many challenges. Herein, well-defined ultrathin Li4Ti5O12 nanosheet-assembled hierarchical tubes (LTONS-HTs) were synthesized through a one-step low-temperature hydrothermal lithiation procedure followed by topotactic transformation via thermal decomposition in air. It was proposed here that the formation of the hierarchical tubular structure was led by an inward dissolution and outward recrystallization mechanism. When tested as anode for LIBs, LTONS-HT manifests high rate capability (e.g. 156 mA h g−1 at 4 A g−1, and 154 mA h g−1 at 10 A g−1) and maintains an outstanding specific capacity of 128 mA h g−1 at 8 A g−1 after 1000 cycles. Moreover, LTONS-HTs is matched with the commercial cathode LiFePO4 to assemble a Li-matched full cell, which demonstrates good rate performance (58 mA h g−1 at 4 A g−1) and very stable energy-storage performance (a capacity retention of ∼80% after 300 cycles 2 A g−1). The superior electrochemical properties verify that the combination of the structural advantages of tubular architecture and ultrathin nanosheet can prompt the lithium insertion/extraction kinetics. Our work offers a new approach to the scalable and cost-effective synthesis of advanced hierarchical Li4Ti5O12 anodes for high-power LIBs.

A dual-layer micro/nanostructured fibrous membrane with enhanced ionic conductivity for lithium-ion battery

Electrospun fiber-based composite membrane with interconnected porous structure has drawn significant attention for application in lithium-ion battery (LIB) owing to its high ion transportation. Here, we report a facile approach to fabricate the hierarchically micro/nanostructured ultrathin SiO2-PAN skin layer on the PAN-PU fibrous membrane surface via electrospinning and sequential electrospraying techniques. Benefiting from the synergistic effect of the micro/nanostructure and the superior electrolyte affinity of the SiO2-PAN skin layer, the as-prepared SiO2-PAN@PAN-PU membrane demonstrates the decreased pore size (1.18 μm), enhanced ionic conductivity (1.4 mS cm−1) and robust electrochemical stability up to 5.08 V. Moreover, the introduction of skin layer endows the as-prepared SiO2-PAN@PAN-PU membrane with improved stress strength (15.7 MPa) and excellent thermostability of 200 °C. Compared with the PAN-PU and Celgard membranes, the dual-layer micro/nanostructured SiO2-PAN@PAN-PU fibrous membrane based Li/LiFePO4 cell assembled with high mass-loading LiFePO4 demonstrates a more stable cycling lifetime with a high discharge capacity (107.4 mAh g−1 at the 105th cycles) and higher rate capability (75.2 mAh g−1 at 1 C). The strategy using electrospraying technique demonstrated in this work will open the door to narrow fibrous membrane pore size and enhance ionic conductivity for potential application in the high-power LIB.

Comparison of lithium-ion battery performance at beginning-of-life and end-of-life

In this paper, a comparison between the performance of a Lithium-ion battery at beginning-of-life (BOL) and at two increased degradation levels is presented. The capacity, internal resistance, and open circuit voltage of a 13 Ah high-power Lithium-ion battery had been measured at BOL for different temperatures, C-rates, and state-of-charge (SOC) levels. Then, two battery cells were aged at two different cycle aging conditions until they lost 40% and 60% of their initial capacity, respectively. At that moment, the two battery cells were removed from the aging processes and were subjected to characterization measurements similar to the ones performed at BOL. The obtained results shown that besides the expected capacity fade and internal resistance increase, there is a dramatic change in the variation of the battery performance parameters with the temperature, C-rate, and/or SOC, between a fresh cell and the two heavily degraded cells.

Fe2O3@C core@shell nanotubes: Porous Fe2O3 nanotubes derived from MIL-88A as cores and carbon as shells for high power lithium ion batteries

To pursue Fe2O3-based electrode with high-rate and long-life lithium storage capacity, we have developed a porous Fe2O3@C core@shell nanotube synthesized by a facile thermal treatment combining with hydrothermal method. As an advanced anode for lithium ion batteries, the Fe2O3@C core@shell nanotubes deliver high initial coulombic efficiency of 80.3% at 0.1 C with the first charge/discharge capacity of 1097.7/1366.9 mAh g−1, and excellent high-rate and long cycling stability with reversible capacity of 811.3 mAh g−1 after 1000 cycles at 1 C. The greatly improved performance is ascribed to the 1D porous nanotube and carbon shell: the 1D porous nanotube can not only effectively increase the contact area between active materials and electrolyte, but also shorten the migration path for Li+ ions and electrons. The carbon shell works as buffer to accommodate volume changes of Fe2O3 during cycling and as conductive support to improve the electrical conductivity of Fe2O3.

Unravelling the Interface Layer Formation and Gas Evolution/Suppression on a TiNb2O7 Anode for Lithium-Ion Batteries.

TiNb2O7 (TNO) has been regarded as a promising anode material for high-power lithium-ion batteries because of the high theoretical capacity and rate performance within the operation voltage range of 1.0-3.0 V. Herein, the electrochemical performance and interface evolution of TNO are comprehensively investigated by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The prepared TNO shows a high initial reversible capacity of 256 mA h g-1 and a satisfactory capacity retention of 68.4% after 200 cycles at 0.1 C. It is generally believed that the formation of solid electrolyte interface (SEI) film could be avoided at the high operating voltage beyond 1.0 V. However, we find that the thin SEI layer is formed during the lithium insertion process and partially dissolved during the following lithium extraction process, and subsequently the SEI layer increases gradually during long-term cycles. Most importantly, we find obvious gassing behavior in the TNO/LiFePO4 pouch cell for the first time and demonstrate effective suppression effects of VC additive on the swelling phenomenon of full batteries.

Porous LiMn2O4 with Al2O3 coating as high-performance positive materials

In order to improve the universality of LiMn2O4 materials, LiMn2O4 coated with Al2O3 (LMO@Al) is prepared by a co-precipitated method to improve the electrochemical performance of the porous LiMn2O4 cathode. The morphologies and microstructures are characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, and energy-dispersive spectroscopy. The electrochemical performances are investigated by galvanostatic charge-discharge test system and inductively coupled plasma emission spectrograph. The results show that the Al2O3 coating uniformly as well as tightly coupled with LiMn2O4 particles. The LMO@Al cathode material also shows outstanding electrochemical behaviors. After 100 cycles, the capacitance can remain 98.6 and 91.2% at 25 and 55 °C, respectively. Moreover, the LMO@Al composite cycled reversibly at 25 °C for 10 C with stable discharge capacities of 94.4 mAh g−1. Superior electrochemical stability of the LMO@Al can be attributed to the uniform coating which inhibited the manganese dissolution and Jahn-Teller effect of LiMn2O4 materials as well as the decomposition of the electrode by HF corrosion. The LMO@Al obtained from this work can open a new possibility in high power lithium ion batteries application.

Investigation into the effectiveness of nanofluids on the mini-channel thermal management for high power lithium ion battery

An effective thermal management system that can maintain the maximum temperature and temperature difference in a desired range is needed to ensure a good performance and safety of lithium-ion batteries. In this paper, a mini-channel cooling system for high-power prismatic battery thermal management is investigated numerically using a three dimensional CFD model. The thermal performances of the cooling system when using different base fluids (i.e. water, ethylene glycol and engine oil) and their corresponding nanofluids as coolants are compared. The thermal conductivities of nanofluids are calculated using a semi-empirical correlation and the dynamic viscosities of nanofluids with different base fluids are obtained by curve fitting using experimental data. Due to its high thermal conductivity, water achieves a much better cooling effect than ethylene glycol and engine oil. However, the impact of adding nanoparticles is more remarkable for fluids with lower thermal conductivity, especially for engine oil. The nanoparticle addition is able to greatly reduce the cell maximum temperature but has a limited effect on the temperature uniformity. In addition, an evident performance enhancement is observed by increasing the suspended nanoparticles volume fractions despite that the required power cost is increased at the same time. Different influencing factors including the flow velocity and coolant inlet temperature on the mini-channel cooling performance and the enhancement of adding nanoparticles are also studied. It is observed that all of these influencing factors have significant impacts on the mini-channel cooling effects.

High rate cyclability of nickle-doped LiNi0.1Mn1.9O4 cathode materials prepared by a facile molten-salt combustion method for lithium-ion batteries

Here we employed a facile low temperature molten-salt combustion method combined with two-stage calcination process to synthesize a series of Ni-doped spinel LiNi0.1Mn1.9O4 cathode materials. All the LiNi0.1Mn1.9O4 materials present well-defined cubic spinel structure with a representative Fd3m space group. With the elevated calcination temperature, the particle size and crystallinity increase simultaneously. Benefiting from the optimization of calcination temperature, the LiNi0.1Mn1.9O4 prepared at 600 °C reveals a favorable crystal structure and morphology consisted of homogeneous nanoparticles with a size of 90–110 nm. Consequently, the optimized LiNi0.1Mn1.9O4 cathode exhibits high rate capability and ultralong cycling stability with a discharge specific capacity of 97.1 mAh g−1 and a capacity retention of 63.5% after 1000 cycles at a high current rate of 10 and 25 °C. Even at a high-temperature of 55 °C, a high initial discharge capacity of 106.1 mAh g−1 and a good capacity retention of 79.0% is also obtained after 100 cycles at 5 C. Such an excellent electrochemical performance together with the facile synthesis approach may endow the as-prepared LiNi0.1Mn1.9O4 to be a promising practical application for high-power lithium-ion batteries.

Layered titanate hierarchical spheres as a promising pseudocapacitive electrode material for high rate lithium ion batteries

Layered titanates with large interlayer spacing (ca. 0.8–0.9 nm) facilitate Li+ movement with less resistance, and are considered suitable anode materials for high power lithium ion batteries (LIBs). Herein, lepidocrocite-type titanate hierarchical spheres (W-THSs) assembled by nanowires are synthesized by supercritical hydrothermal treatment of sodium peroxotitanate complex solution and subsequent acid washing. Nanowire components in the W-THSs interpenetrate each other to form a mesoporous network with high specific surface area (183.6 m2 g−1), which provides electrolyte penetration channels, enlarged electrode/electrolyte contact area, and short charge transport path, favoring fast Li+ insertion/extraction. Consequently, W-THSs exhibits an excellent electrochemical performance, giving a high discharge capacity of 123.6 mAh g−1 even at 5.0 A g−1, and still retaining 180.8 mAh g−1 after 500 cycles at 1.0 A g−1. The rate capability of W-THSs is much superior to the compared anatase TiO2 hierarchical spheres (AHSs) obtained by calcining W-THSs in the air. Moreover, cyclic voltammetry analyses reveal that a pseudocapacitive process occurs during the Li+ storage in W-THSs, significantly contributing to the excellent rate capability.

Fluorinated Copolymer Functionalized with Ethylene Oxide as Novel Water-Borne Binder for a High-Power Lithium Ion Battery: Synthesis, Mechanism, and Application

A novel water-borne fluorinated binder is synthesized via copolymerizing 2-(perfluorohexyl) ethyl methacrylate (PFHEMA) and poly(ethylene glycol) methacrylate (PEGMA) to improve the performance of lithium ion battery with LiFePO4-based cathode materials. The resulting copolymer binders can self-assemble into 150–220 nm particles stably dispersed in aqueous solution. Self-dispersed fluorinated binders (SF binders) with the PFHEMA to PEGMA ratio of 3:1 effectively reduce the overpotential during the high-discharge current density compared with the conventional PVDF cathode binder. Further increasing the PEGMA amount yet decreases the electrochemical performance of SF binders, inconsistent with the expected Li+ conduction of the PEO moiety. Molecular dynamics simulations show that the PEO segments reduce the Li+ and PF6– interaction and increase the amount of unpaired Li+. In contrast, the PEO moiety wrapping around Li+ can decrease its mobility. These competing effects lead to the observed optimum ratio of ...

Preparation and electrochemical performances of xLi2MnO3·(1-x) LiNi0.45Co0.2Mn0.35O2 (0 ≤ x ≤ 1) for high-power lithium-ion batteries

In this paper, a series of cathode materials xLi2MnO3·(1-x) LiNi0.45Co0.2Mn0.35O2 (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) were prepared by a carbonate co-precipitation method followed by a two-step sintering process. The effects of different x values on the phase structure, particles size distribution, tap density and electrochemical properties of as-prepared samples were systematically studied. The results display that the two phases between Li2MnO3 and LiNi0.45Co0.2Mn0.35O2 have a better synergistic effect: firstly, suitable amount of Li2MnO3 can stabilize the hexagonal α-NaFeO2 layered structure of OLO and inhibit the mixing positions of Li+ and Ni2+. Secondly, when the x value is 0.5 (MCO-0.5), spherical precursors have the most monodispersed particles size distribution (d = 0.72) and the highest tap density (1.82 g cm−3) among all prepared powders. Finally, 0.5Li2MnO3·0.5LiNi0.45Co0.2Mn0.35O2 (OLO-0.5) delivers a high initial discharge capacity (220 mAh g−1 at 0.1C) and a superior cyclic stability (~ 96% after 100 cycles). Moreover, OLO-0.5 provides the best rate capability owing to the highest discharge capacity when the C-rate increases from 0.1 to 10C.

Hetero-nanostructured materials for high-power lithium ion batteries

The development of high technology electrical devices increased the importance of higher power density or higher capacity at high current density. Especially, rapid charge/discharge issues remain problematic for electric vehicle commercialization. After extensive investigation, researchers introduced hetero-nanostructured materials to the field of lithium ion batteries (LIBs), aiming to enhance the power density or improve the capacity at high current density and life cycle capability. Hetero-nanostructured materials consist of current collectors and directly attached active nanomaterials. Carbon, carbon nanotube (CNT), graphene, Nickel (Ni), Copper (Cu) and Aluminum (Al) were used for current collector, aiming to improve the electron transfer and the cyclability, due to high electrical conductivity and superior buffering effects. Also, Hetero-nanostructure can produce a favorable lithium diffusion condition by creating a lithium diffusion pathway. This article presents an explanation of important factors for high power density or high capacity at high current density. It summarizes the capacity of electrode materials at high current density, including structural descriptions and material types.

Phosphorus-doped TiO2-B nanowire arrays boosting robust pseudocapacitive properties for lithium storage

TiO2-B has received increasing interest as a possible anode for lithium-ion batteries, but its properties are restricted by the intrinsically low electronic conductivity. Herein, we first demonstrate that phosphorus doping can be an efficient approach to boost the pseudocapacitive properties of TiO2-B nanowire arrays. The phosphorus doping not only promotes electronic conductivity of TiO2-B nanowire arrays by modifying their electronic structure, but also significantly enhances the electrochemical surface reactivity. Density functional theory calculations further reveal that the phosphorus doping could improve the surface lithium affinity of TiO2-B nanowire arrays. Consequently the phosphorus-doped TiO2-B nanowire arrays simultaneously exhibit high reversible capacity (350.9 mAh g−1), remarkable rate capability (142.6 mAh g−1 at 30 C), and impressive cyclability (approximately 80% capacity retention efficiency over 3000 continuous cycles at 10 C), holding promise in high-energy and high-power lithium-ion batteries application.

Suppressing Voltage Decay of a Lithium-Rich Cathode Material by Surface Enrichment with Atomic Ruthenium.

Lithium-rich layered oxides are promising cathode materials for high-energy-density lithium-ion batteries. However, the development of cathode materials based on these layered oxides has been limited by voltage fading, poor rate performance, and the low tap density of these materials. In this work, we prepared a material consisting of micrometer-scale spherical lithium-rich layered oxide particles with a three-dimensional conductivity network design and modified the surface of the primary particles with ruthenium. The as-obtained product with a maximum tap density of 2.1 g cm-3 shows a superior high reversible capacity with 280 mA h·g-1 at 0.1 C, a capacity retention of 98.1% after 100 cycles, and an outstanding rate capability. More importantly, enrichment of the primary particle surface with ruthenium can effectively suppress voltage decay. This cathode is feasible to construct high-energy and high-power lithium-ion batteries. This novel design may furthermore open the door to new material engineering applications for high-performance cathode materials.

Enhanced lithium and electron diffusion of LiFePO4 cathode with two-dimensional Ti3C2 MXene nanosheets

Novel LiFePO4/Ti3C2 composite (LFP/TC) cathodes have been prepared via a simple wet mixing method followed by a heat treatment at 400 °C. Ti3C2 nanosheets bridge the LiFePO4 nanoparticles to form an integrated conductive network via the “plane-to-point” conducting mode. This conductive network acts as short pathways for the diffusion of both lithium ion and electron in the composite cathode. Thus, the electronic and ionic conductivities are simultaneously enhanced, leading to the improved electrochemical properties of LFP/TC composites. Thereinto, the LFP/TC composite with 2 wt% Ti3C2 (LFP/TC2) delivers the highest initial discharge capacity of 159 mAh g−1 at 0.1 C as well as the best rate performance with a high reversible capacity of 86 mAh g−1 at 5 C. Meanwhile, the LFP/TC2 composite also holds the superior capacity retention of 96% at 1 C after 100 cycles. The results demonstrate that LFP/TC composite has promising practical applications as the cathode material in the high-power lithium-ion batteries.

Rational Design and Synthesis of Li3V2(PO4)3/C Nanocomposites As High-Performance Cathodes for Lithium-Ion Batteries

Synthesis of cathode materials with high rates and long cycle life is critical to meet the demands of high-power lithium-ion battery applications. Batteries that can work at extreme low temperature conditions are also urgently needed. Herein, we report the rational design and synthesis of a novel lithium vanadium phosphate/carbon (Li3V2(PO4)3/C) nanocomposite with a thin-layer amorphous carbon shell (∼4 nm) coating and a mesoporous KB carbon matrix. As expected, the Li3V2(PO4)3/C nanocomposite demonstrates an excellent high-rate and long-term cycling performance as well as broad temperature adaptability. Even at a high rate of 16C, a high capacity of 102 mA h g–1 can be achieved. Importantly, the capacity retention is 99% after 1000 cycles and 94% after 2000 cycles when cycled at a rate of 6 C at room temperature in a voltage range of 3–4.3 V. Importantly, this nanocomposite can cycle at −30 °C for 500 cycles with a stable capacity. The excellent rate capability, stable cycling performance, and broad temp...

Synthetic Control and Structural Stabilization of Ni-Rich Layered Oxides As High-Energy Cathode Materials for Lithium Ion Batteries

Ni-rich layered oxides (LiNi1-xMxO2, M=Co, Mn, Al, etc., x<0.5) have been demonstrated as practical cathode materials for high-energy and high-power lithium ion batteries. However, various synthetic factors affect the layered structural ordering of LiNi1-xMxO2 and related electrochemical lithium storage performances. Herein, we report on developing a high-capacity Ni-rich LiNi0.8Co0.1Mn0.1O2 oxide with enhanced cycleability via the synthetic control. Systemic investigation is made to the phase evolution of LiNi0.8Co0.1Mn0.1O2 oxide under different annealing temperatures by ex-situ and in-situ synchrotron X-ray diffraction (XRD) measurements, coupled with quantitative structural analysis through refinements. Structural characterization indicates an intriguing phase transition of LiNi0.8Co0.1Mn0.1O2 from a rock-salt structure at low annealing temperatures directly to a layered α-NaFeO2-type structure with a R-3m space group at high temperatures. The in-situ XRD studies gain us access to the phase diagram in the confined Ni-rich region of the Ni-Mn-Co space, thereby enabling the design of synthetic protocols for preparing high-capacity LiNi1-x-yMnxCoyO2 oxides with stabilized structure and reasonable cycling stability. Furthermore, a preheating process and Li2TiO3 coating layer have been introduced during the synthesis of LiNi0.8Co0.1Mn0.1O2 oxide, in order to manipulate the lithium source reaction by fabricating the outer shell in advance. As a result, the resulting LiNi0.8Co0.1Mn0.1O2 cathode material reveals the higher degree of structural ordering and considerably enhanced lithium storage performances. This work offers a feasible route to optimize the layered structure of Ni-rich cathode materials via the synthetic control of the lithium source reaction, and further sheds light on the fundamental relationship between crystal structure and electrochemical performance for high-energy lithium ion batteries.