High-energy Lithium-ion Batteries Research Articles

Solvent-Free Method Prepared a Sandwich-like Nanofibrous Membrane-Reinforced Polymer Electrolyte for High-Performance All-Solid-State Lithium Batteries.

Solid polymer electrolytes (SPEs) with the advantages of high safety, low volatility, and the ability to suppress Li dendrites are highly desirable to be used in next generation high-safety and high-energy lithium-ion batteries. The exploration of SPEs with superior comprehensive properties has received extensive attention for high-performance all-solid-state batteries (ASSBs). Herein, a sandwich-like nanofibrous membrane-reinforced poly-caprolaclone diol and trimethyl phosphate (TMP) composite polymer electrolyte (CPE) has been designed by a facile "solvent-free" solution-casting method. Specifically, the flame-retardant TMP is employed as a plasticizer, which can improve the ionic conductivity effectively. The as-prepared solid electrolyte exhibits superior comprehensive performance in terms of high ionic conductivity, wide electrochemical window, good compatibility with lithium metal, and superior thermal stability. Furthermore, the assembled Li//LiFePO4 ASSBs with this solid CPE show outstanding cycling stability and high average discharge capacity at room temperature (30 °C). Undoubtedly, our study provides a new facile method and a qualified solid electrolyte material for next generation high-performance ASSBs.

Enhanced high-temperature performance of Li-rich layered oxide via surface heterophase coating

Abstract Li-rich layered oxides have become one of the most concerned cathode materials for high-energy lithium-ion batteries, but they still suffer from poor cycling stability and detrimental voltage decay, especially at elevated temperature. Herein, we proposed a surface heterophase coating engineering based on amorphous/crystalline Li3PO4 to address these issues for Li-rich layered oxides via a facile wet chemical method. The heterophase coating layer combines the advantages of physical barrier effect achieved by amorphous Li3PO4 with facilitated Li+ diffusion stemmed from crystalline Li3PO4. Consequently, the modified Li1.2Ni0.2Mn0.6O2 delivers higher initial coulombic efficiency of 92% with enhanced cycling stability at 55 °C (192.9 mAh/g after 100 cycles at 1 C). More importantly, the intrinsic voltage decay has been inhibited as well, i.e. the average potential drop per cycle decreases from 5.96 mV to 2.99 mV. This surface heterophase coating engineering provides an effective strategy to enhance the high-temperature electrochemical performances of Li-rich layered oxides and guides the direction of surface modification strategies for cathode materials in the future.

Micrometer-sized ferrosilicon composites wrapped with multi-layered carbon nanosheets as industrialized anodes for high energy lithium-ion batteries

Various nanostructured architectures have been demonstrated to be effective to address the issues of high capacity Si anodes. However, the scale-up of these nano-Si materials is still a critical obstacle for commercialization. Herein, we use industrial ferrosilicon as low-cost Si source and introduce a facile and scalable method to fabricate a micrometer-sized ferrosilicon/C composite anode, in which ferrosilicon microparticles are wrapped with multi-layered carbon nanosheets. The multi-layered carbon nanosheets could effectively buffer the volume variation of Si as well as create an abundant and reliable conductivity framework, ensuring fast transport of electrons. As a result, the micrometer-sized ferrosilicon/C anode achieves a stable cycling with 805.9 mAh g −1 over 200 cycles at 500 mA g −1 and a good rate capability of 455.6 mAh g −1 at 10 A g − 1 . Therefore, our approach based on ferrosilicon provides a new opportunity in fabricating cost-effective, pollution-free, and large-scale Si electrode materials for high energy lithium-ion batteries. Ferrosilicon composites wrapped with multi-layered carbon nanosheets (MLC) were fabricated. MLC constructs more abundant and reliable conductive network and provides more effective confinement for micrometer-sized Si than conventional carbon coating, which induces superior electrochemical performance.

Hybrid lithium-ion capacitors based on novel 1-butyl-3-methylimidazolium bis(nonafluorobutanesulfonyl imide) (BMImBNFSI) ionic liquid electrolytes: a detailed investigation of electrochemical and cycling behaviors

Recently, electrochemical energy storage devices and hybrid lithium-ion capacitors (HLICs), in particular have received intensive interest because of their ability to combine the performance of high-energy lithium-ion batteries and high-power supercapacitors. In the present investigation, a new bulky fluorinated ionic liquid, 1-butyl-3-methylimidazolium bis(nonafluorobutanesulfonyl imide), was synthesized via an ion-exchange method and tested for its applications in HLICs. The prepared ionic liquid was used to prepare nonaqueous electrolytes in combination with the lithium salt lithium bis(nonafluorobutane sulfonyl imide) and the solvent propylene carbonate. The electrochemical properties of the resultant ionic liquid electrolytes were analyzed and evaluated through linear sweep and cyclic voltammetry analyses. The maximum ionic conductivity of the prepared electrolytes was on the order of 10−3 S cm−1 at room temperature. HLIC cells fabricated using the prepared ionic liquid electrolytes and activated carbon electrodes delivered a maximum specific capacitance of 102.1F g−1 at a current density of 1 A g−1. Similarly, the prepared HLIC cell with LiCoO2 exhibited a maximum discharge capacity of 128.25mAh g−1 at ambient temperature. The results suggest that the ionic liquid electrolyte has potential applications as an active separator in future HLIC devices.

High-Rate Layered Cathode of Lithium-Ion Batteries through Regulating Three-Dimensional Agglomerated Structure

LiNixCoyMnzO2 (LNCM)-layered materials are considered the most promising cathode for high-energy lithium ion batteries, but suffer from poor rate capability and short lifecycle. In addition, the LiNi1/3Co1/3Mn1/3O2 (NCM 111) is considered one of the most widely used LNCM cathodes because of its high energy density and good safety. Herein, a kind of NCM 111 with semi-closed structure was designed by controlling the amount of urea, which possesses high rate capability and long lifespan, exhibiting 140.9 mAh·g−1 at 0.85 A·g−1 and 114.3 mAh·g−1 at 1.70 A·g−1, respectively. The semi-closed structure is conducive to the infiltration of electrolytes and fast lithium ion-transfer inside the electrode material, thus improving the rate performance of the battery. Our work may provide an effective strategy for designing layered-cathode materials with high rate capability.

Microwave reduction enhanced leaching of valuable metals from spent lithium-ion batteries

Abstract The growing demand for high-energy lithium-ion batteries (LIBs) has promoted the production of LiNixCoyMnZO2 cathode, which results in many spent LIBs to resolve. A novel method that employs microwave carbothermic reduction was used to enhance the leaching of metals from layered LiNi1/3Co1/3Mn1/3O2 of spent LIBs. The thermodynamic analysis showed that LiNi1/3Co1/3Mn1/3O2 could be theoretically reduced to single metals in the presence of graphite. Then experimental results demonstrated that the transition metals can be effectively reduced under the parameters of 500 W microwave energy and 30min time. Afterward, multiscale characterizations revealed that microwave irradiation leads to the disorderly crystal structure and lattice cracks of LiNi1/3Co1/3Mn1/3O2 materials, which is more efficient to facilitate their interparticle liberation and destruction of crystal structure compared with the conventional heating process. Based on the characterization of the reduction products and their leaching performance, the mechanism for microwave carbothermic reduction was accordingly raised. Finally, the leaching experimental results show the optimal efficiencies of 97% transition metals (Co Ni, and Mn) and 99% Li were obtained under microwave carbothermic reduction, which is found more efficient in comparison to the samples without microwave treated. The whole process is found to be effective and sustainable for recovery of valuable metals from the industrial electrode of spent LIBs.

Interface Heteroatom-doping: Emerging Solutions to Silicon-based Anodes.

Silicon-based composites have been recognized as a promising anode material for high-energy lithium-ion batteries (LIBs). However, the intrinsically low conductivity and the huge volume expansion during lithiation/delithiation progresses impede its further practical applications. In the past decades, numerous efforts have been made for surface and interface modification of Si-based anodes. Among these, doping of active materials with heteroatoms is one promising method to endow silicon many unmatched electrochemical properties. In this review, we focus on the effects of heteroatom doping on the interfacial properties of Si-based anodes, and some typical strategies for the interface doping are highlighted. We aim to give some reference for interfacial doping of Si-based anodes in LIBs.

Facile Synthesis of Layered LiV3O8 Nanosheets and Their Electrochemical Performance as Cathode Materials for Li-Ion Batteries

Layered nanosheets of a LiV3O8 cathode material were successfully prepared via a modified solid-state synthesis. The morphological changes of the layered nanosheets of the LiV3O8 cathode, which resulted from preparation at different temperatures, strongly affected the electrochemical performance of this cathode material. The layered nanosheets of the LiV3O8 cathode prepared at 500 °C delivered the highest electrochemical performance with initial charge and discharge capacities of 212 and 175 mAh g−1, respectively, when cycled between 1.5 and 4.0 V versus Li/Li+. The particulate morphology of LiV3O8 showed widths in a range of 100-145 nm and lengths between 1.0 and 2.5 µm. The layered nanosheet structure contributed to the increased electrochemical performance of LiV3O8 as a cathode material for applications in high-energy lithium-ion batteries.

Synthesis of pomegranate-structured Si/C microspheres using P123 as surfactant for high-energy lithium-ion batteries

To meet the urgent needs for higher energy density and longer lifespan of lithium-ion batteries (LIBs), silicon (Si) anode material has been proposed to be the most prospective and brightening substitutions to the commercial graphite anode materials, because of its low working voltage and tremendous theoretical specific capacity. In this paper, a simple and easy way to synthesize the Si/carbon (Si/C) composite is developed via a one-step hydrothermal method using Pluronic P123 as surfactant for the first time. The introduction of P123 is in favor of the dispersion of Si in the glucose water. Thus, the obtained Si/C composite takes on a pomegranate-structure, in which Si nanoparticles evenly inserted into the carbon matrix. The unique structure of Si/C could ensure the better electronic conductivity, and alleviate the big volume change during cycling process. As a consequence, the obtained Si/C composite presents better cycling stability and rate performance than bare Si material. After 100 cycles, the Si/C composite shows the high cycling capacity of 530 mAh g−1 under the current density of 0.5 A g−1 and a prominent high capacity of 460 mAh g−1 even under the high current density of 1 A g−1. The proposed preparation way is easy, simple and practical to carry out for the commercial process to achieve the high-performance for LIBs by efficient anode materials.

Boosting initial coulombic efficiency of Si-based anodes: a review

Silicon-based composites are intensively pursued as one of the most promising anode materials for high-energy lithium-ion batteries (LIBs) owing to their ultrahigh theoretical capacity. However, the extended application of Si-based anode is still retarded by challenge of the poor initial coulombic efficiency (ICE), which will lead to the irreversible capacity loss of the full cell in the first cycle. In recent years, significant achievements have been dedicated to reducing irreversible lithium ion consumption to realize high ICE values. In this review, we summarize the main influence factors of ICE, including electrical conductivity, structural stability, and specific surface area. The major focus of this review is to present the recent progress in rational structural design and scalable prelithiation techniques to boosting the ICE, which is of great significance to promoting the practical applications of silicon-based anodes.

Mitigating the Microcracks of High-Ni Oxides by In Situ Formation of Binder between Anisotropic Grains for Lithium-Ion Batteries.

Increasing attention has been paid to layered high-Ni oxides with high capacity as a promising cathode for high-energy lithium-ion batteries. However, the undesirable microcracks in secondary particles usually occur due to the volume changes of anisotropic primary grains during cycles, which lead to the decay of electrochemical performance. Here, for the first time, a functional electrolyte with di-sec-butoxyaluminoxytriethoxysilane additive integrating the functions of silane and aluminate is proposed to in situ form the binder-like filler between anisotropic primary grains for mitigating the microcracks of high-Ni oxides. It is demonstrated that Li-containing aluminosilicate as a glue layer between the gaps of grains and as a coating layer on the surface of the grains is generated, and these features further enhance the interfacial bonding and surface stability of anisotropic primary grains. Consequently, the microcracks along with side reactions and phase transitions of high-Ni oxides are mitigated. As anticipated, the electrochemical performance and thermal stability of high-Ni oxides are improved, and there is also a capacity retention of 75.4% even after 300 cycles and large reversible capacity of ∼160 mA h g-1 at 5 C. The functional electrolyte offers a simple, efficient, and scalable method to promote the electrochemical properties and applicability of high-Ni oxide cathodes in high-energy lithium-ion batteries.

Author Correction: Scalable synthesis of silicon-nanolayer-embedded graphite for high-energy lithium-ion batteries

Author Correction: Scalable synthesis of silicon-nanolayer-embedded graphite for high-energy lithium-ion batteries

High performance well-developed single crystal LiNi0.91Co0.06Mn0.03O2 cathode via LiCl-NaCl flux method

Ni-rich LiNi1-xCoxMnyO2 (x ≥ 0.8) cathode is regarded as promising cathode for high-energy lithium ion batteries. One important challenge for Ni-rich LiNi1-xCoxMnyO2 is to enhance the long-term stability with maintain high energy density. Herein, we report the preparation of single crystal LiNi0.91Co0.06Mn0.03O2 cathode by flux method to improve the cycle performance. Although single crystal delivers slightly lower discharge capacity (203.8 mAh/g), it shows obviously superior cycle life (80.8% after 70 cycles) than that of polycrystalline (69.8% after 70 cycles). It can be elucidated that single-crystal can be maintained its original morphology during cycling. Therefore, we believe that single crystal LiNi0.91Co0.06Mn0.03O2 can be applied to high-energy and long-life lithium ion batteries.

Preparation and characterization of Li1.167-xKxMn0.583Ni0·25O2 (x=0, 0.025, 0.05 and 0.075) as cathode materials for highly reversible lithium-ion batteries

Lithium-rich cathode materials have the potential for applications in high energy lithium-ion batteries, but they suffer from a low rate performance and an inferior cycling stability. In this work, Li1.167-xKxMn0.583Ni0·25O2 (x = 0, 0.025, 0.05 and 0.075) samples are synthesized and characterized. In addition, K+ doping results in small perturbations in the crystal structure of Li1.167-xKxMn0.583Ni0·25O2, such as the Li–O bond lengths, lattice parameters and the oxidation states of manganese, which effectively improves the lithium diffusion ability and hinders the detrimental interphase growth of the spinel phase during cycling. In a half-cell, Li1·117K0·05Mn0·583Ni0·25O2 (LK2MNO) with an optimized doping quantity of K+ delivers the best capacities of 152.0 mAh g−1 after 100 cycles at a 1C rate and 82.9 mAh g−1 after 300 cycles at a 10C rate, in comparison with Li1·167Mn0·583Ni0·25O2, which has a capacity of only 126.0 and 33.3 mAh g−1. In the full-cell with graphite as the negative electrode, LK2MNO delivers an initial capacity of 249.9 mAh g−1 at a 0.1C rate and retains 90.8% of its initial capacity after 100 cycles. The surface chemical states of the positive electrode and negative electrodes after 100 cycles is studied by ex situ SEM and XPS measurements, and the results reveal that an appropriate K+ doping amount effectively hinders the dissolution of Mn2+ from the cathode material and decreases the decomposition of electrolytes to some degree.

Graphene Flake-Based Electrodes for High-Energy and Power Lithium-Ion Semi-flexible Rechargeable Batteries

Developing devices and related materials for storing and producing electricity is a key issue to meet the global energy demand. Low-cost and high-performance energy-storage devices are important for sustainable energy utilization. Recently, lithium-ion battery (LIB) is emerging as a promising power source for high-performance electronics. However, their technological drawbacks have hindered the development of LIB with improved specific capacity, stable cyclic and coulombic efficiency for portable electronics application, due to the lack of availability of reliable electrode materials that provided superior electrochemical properties. As a solution to this problem, we herein demonstrated two types of few-layered graphene produced by Fenton reaction (FG) and Hummers method (HG) used for the fabrication of electrodes on flexi copper and aluminum foils in two different ways. Lithium iron phosphate (LiFePO4 or LFP) mixed with super-P carbon black (SP) and fabricated cathode, FG and HG, respectively, blended with SP and fabricated two anodes, by carefully balancing the cell composition of the anode and cathode. An optimal cell performance in terms of specific capacity and stable cyclability depends on the fabrication method of electrodes and their chemical composition. The FG electrodes showed a specific capacity of 186 mAh g−1 at 150 mA g−1 charge/discharge (C/D) current rate while HG showed a specific capacity of 195mAh g−1 at same C/D rate without capacity decay during 30 cycles and an excellent cycling stability was also observed when HG was used in cathode with SP in the same ratio at 150, 300 and 450 mA g−1 C/D rate in full LIB.

Toward a high-voltage fast-charging pouch cell with TiO2 cathode coating and enhanced battery safety

Nickel-rich layered lithium transition metal oxides, LiNixCoyMn1-x-yO2, are key cathode materials for high-energy lithium-ion batteries owing to their high specific capacity. However, the commercial deployment of nickel-rich oxides has been hampered by their poor thermostability and insufficient cycle life. Here full batteries with uncoated and TiO2-coated LiNi0.5Co0.2Mn0.3O2 cathodes and graphite anodes are compared in terms of electrochemical performance and safety behavior. The battery using a TiO2-coated LiNi0.5Co0.2Mn0.3O2 cathode exhibited better cyclic performance at high cutoff voltage. Electrochemical impedance spectroscopy analysis indicated that the TiO2-coated LiNi0.5Co0.2Mn0.3O2 cathode gave the battery a more stable charge transfer resistance. Transmission electron microscopy demonstrated that TiO2 coating reduced accumulation of the cathode electrolyte interface layer on the particle surface. Time-of-flight secondary ion mass spectrometry demonstrated that TiO2 coating markedly enhanced the interface stability of the cathode particle and protected the particle from serious etching by the electrolyte. Accelerating rate calorimetry revealed that the trigger temperature of thermal runaway for the battery using TiO2-coated LiNi0.5Co0.2Mn0.3O2 as cathode material was 257 °C, which was higher than that of the battery with the uncoated LiNi0.5Co0.2Mn0.3O2 cathode (251 °C). In situ X-ray diffraction during heating demonstrated that this enhanced safety can be attributed to the suppressed phase evolution of the coated cathode material.

A highly stabilized Ni-rich NCA cathode for high-energy lithium-ion batteries

In this study, we have demonstrated that boron doping of Ni-rich Li[NixCoyAl1−x−y]O2 dramatically alters the microstructure of the material. Li[Ni0.885Co0.1Al0.015]O2 is composed of large equiaxed primary particles, whereas a boron-doped Li[Ni0.878Co0.097Al0.015B0.01]O2 cathode consists of elongated particles that are highly oriented to produce a strong, crystallographic texture. Boron reduces the surface energy of the (0 0 3) planes, resulting in a preferential growth mode that maximizes the (0 0 3) facet. This microstructure modification greatly improves the cycling stability; the Li[Ni0.878Co0.097Al0.015B0.01]O2 cathode maintains a remarkable 83% of the initial capacity after 1000 cycles even when it is cycled at 100% depth of discharge. By contrast, the Li[Ni0.885Co0.1Al0.015]O2 cathode retains only 49% of its initial capacity. The superior cycling stability clearly indicates the importance of the particle microstructure (i.e., particle size, particle shape, and crystallographic orientation) in mitigating the abrupt internal strain caused by phase transitions in the deeply charged state, which occurs in all Ni-rich layered cathodes. Microstructure engineering by surface energy modification, when combined with protective coatings and composition modification, may provide a long-sought method of harnessing the high capacity of Ni-rich layered cathodes without sacrificing the cycling stability.

One-pot synthesis of polymeric LiPON

Lithium metal is a promising anode material for high energy lithium ion batteries due to its high specific capacity. Inherent difficulties such as the chemical reactivity and dendrite growth during cycling have kept it from being operational in energy storage systems so far. One approach to overcome these challenges is the use of a stable interlayer on top of the lithium. The glassy solid-state electrolyte lithium phosphorus oxynitride (LiPON) is a promising candidate to achieve this. However, it is prepared by a time and energy consuming physical vapor deposition technique. As an alternative to this, we developed the synthesis of a modified polyphosphazene having a similar chemical formula as the glassy LiPON which allows for a large scale application of such a stable interface with an easier and cheaper processing. Following a two-step one pot synthesis starting from poly(dichlorophosphazene), this polymeric LiPON could be successfully isolated and showed solubility in different solvents which distinguishes it clearly from sputtered LiPON.

Sol-gel synthesis of Al- and Nb-co-doped Li7La3Zr2O12 solid electrolytes

A series of the Li7−y−3xAlxLa3Zr2−yNbyO12 (y = 0.1–0.25, x = 0–0.25) solid electrolytes were synthesized by sol-gel method and sintered at 1150 °C for 1 h. The phase analysis was done using X-ray diffraction method and Raman spectroscopy; the obtained compounds have a cubic structure Ia-3d. The Li6.6Al0.05La3Zr1.75Nb0.25O12 solid electrolyte has the highest total conductivity, 6.3·10−4 S cm−1 at 25 °C. The growth of Al content in Li6.75−3xAlxLa3Zr1.75Nb0.25O12 system leads to conductivity decreasing and activation energy growth. The conductivity descend can be associated with the decreasing of charge carriers (Li+) amount in the Li6.75−3xAlxLa3Zr1.75Nb0.25O12 structure. Li6.9−3xAlxLa3Zr1.9Nb0.1O12 and Li6.8−3xAlxLa3Zr1.8Nb0.2O12 solid electrolytes with a smaller addition of Nb have lower values of lithium-ion conductivity. Thus, it was concluded that high conductivity of Li6.6Al0.05La3Zr1.75Nb0.25O12 ceramic is caused by the optimal ratio of lithium vacancies and the number of charge carriers in the garnet structure. Thus, obtained solid electrolyte can be used in high-energy lithium and lithium-ion batteries.

Fast and Controllable Prelithiation of Hard Carbon Anodes for Lithium-Ion Batteries.

Hard carbon has been extensively investigated as anode materials for high-energy lithium-ion batteries owing to its high capacity, long cycle life, good rate capability, and low cost of production. However, it suffers from a large irreversible capacity and thus low initial coulombic efficiency (ICE), which hinders its commercial use. Here, we developed a fast and controllable prelithiation method based on a chemical reaction using a lithium-containing reagent (1 M lithium biphenylide dissolved in tetrahydrofuran). The prelithiation extent can be easily controlled by tuning the reaction time. An SEI layer is formed during chemical prelithiation, and the ICE of prelithiated hard carbon in half-cell format can be increased to ∼106% in 30 s. When matched with a LiNi1/3Co1/3Mn1/3O2 cathode, the full cell with the prelithiated hard carbon anode exhibits a much improved ICE (90.2 vs 75%) and cycling performance than those of the pristine full cell. This facile prelithiation method is proved to be a practical solution for the commercial application of hard carbon materials.