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Low initial Coulombic efficiency (ICE) is an obstacle for practical application of Li‐rich Mn‐based layered oxides (LLOs), which is closely related with the irreversible oxygen evolution owing to the overoxidized reaction of surface labile oxygen. Here we report a NH4F‐assisted surface multicomponent integration technology to accurately control the ICE, by which oxygen vacancies, spinel‐layered coherent structure, and F‐doping are skillfully integrated on the surface of treated LLOs microspheres. Though the regulation on the removed amount of labile oxygen by surface integrated structure, the ICE of LLOs cathodes can adjust from starting value to 100 %. X‐ray absorption spectroscopy, refined X‐ray diffraction, and scanning transmission electron microscopy show that the removed labile oxygen mainly comes from Li2MnO3‐like structure. Even operating at a high cut‐off voltage of 5 V, the capacity retention of integrated sample at 200 mA g−1 is still larger than 98 % after 100 cycles. [ABSTRACT FROM AUTHOR]

Voltage decay and capacity fading are the main challenges for the commercialization of Li‐rich Mn‐based layered oxides (LLOs). Now, a three‐in‐one surface treatment is designed via the pyrolysis of urea to improve the voltage and capacity stability of Li1.2Mn0.6Ni0.2O2 (LMNO), by which oxygen vacancies, spinel phase integration, and N‐doped carbon nanolayers are synchronously built on the surface of LMNO microspheres. Oxygen vacancies and spinel phase integration suppress irreversible O2 release and help lithium ion diffusion, while N‐doped carbon nanolayer mitigates the corrosion of electrolyte with excellent conductivity. The electrochemical performance of LMNO after the treatment improves significantly; the capacity retention rate after 500 cycles at 1 C is still as high as 89.9 % with a very small voltage fading rate of 1.09 mV cycle−1. This three‐in‐one surface treatment strategy can suppress the voltage decay and capacity fading of LLOs. [ABSTRACT FROM AUTHOR]

Although Li-rich layered oxides (LLOs) have the highest capacity of any cathodes used, the rate capability of LLOs falls short of meeting the requirements of electric vehicles and smart grids. Herein, a layered-spinel microsphere/reduced graphene oxide heterostructured cathode (LS-rGO) is prepared in situ. This cathode is composed of a spinel phase, two layered structures, and a small amount of reduced graphene oxide (1.08 wt% of carbon). The assembly delivers a considerable charge capacity (145 mAhg-1) at an ultrahigh charge-discharge rate of 60 C (12 Ag-1). The rate capability of LS-rGO is influenced by the introduced spinel phase and rGO. X-ray absorption and X-ray photoelectron spectroscopy data indicate that Cr ions move from octahedral lattice sites to tetrahedral lattice sites, and that Mn ions do not participate in the oxidation reaction during the initial charge process. [ABSTRACT FROM AUTHOR]

Li-rich layered oxides, one of the most promising cathodes for high energy Li-ion batteries, commonly undergo some issues such as poor rate performance, low Coulombic efficiency, voltage degradation and so on. In this work, Li 1.18 Mn 0.56 Ni 0.13 Co 0.13 O 2 cathodes with excellent rate capability and cycling stability are prepared by a new molten-salt method using KCl and NaCl as complex flux. The electrochemical tests show that these cathodes can deliver an initial discharge specific capacity of 224.3 mA h g −1 at 300 mA g −1 . Meanwhile, the capacity retention ratio remains 92.1% after 100 cycles. The outstanding electrochemical performance is mainly attributed to the uniform distribution of TM-elements in Li 1.18 Mn 0.56 Ni 0.13 Co 0.13 O 2 cathodes, which can promote the electrochemical activation of Li 2 MnO 3 -like component. Especially, it is found that the uniformity of TM elements in Li-rich cathodes can be improved by choosing molten-salt method as the synthetic strategy. [ABSTRACT FROM AUTHOR]

In this work, the effect of exposed facets on voltage decay and capacity fading of Li-rich layered oxides (LLOs) is unraveled via two nanoplates which are prepared by very similar co-precipitated-precursor method. The top-bottom surface of one nanoplate is (101) facet (S101 sample, active plane) and the other is exposed (001) facet (S001 sample, inactive plane). Although S101 sample delivers an excellent rate capability (149 mA h g −1 at 2000 mA g −1 ), both its voltage and capacity decrease faster than S001 sample. TEM, HRTEM, XPS and XRD of cycled samples demonstrate: (1) Large area of active surface will accelerate electrochemical corrosion and phase transformation of LLOs and (2) electrochemical corrosion and phase transformation of LLOs with large area of inactive surface can be mitigated, leading to slow voltage decay and capacity fading. In addition, we discover Co and Ni are easier to react with electrolyte than Mn. Therefore, suitable facets and compositions may be more useful for improving the electrochemical performance of LLOs. [ABSTRACT FROM AUTHOR]

In this work, Li 1.15 Mn 0.49 Ni 0.18 Co 0.18 O 2 nanoplates with exposed (012) facet are prepared for the first time by co-precipitation method under the assistance of cetyltrimethyl ammonium bromide. As cathode materials of lithium-ion batteries, the Li 1.15 Mn 0.49 Ni 0.18 Co 0.18 O 2 nanoplates can deliver the initial discharge capacities of 219.8 and 192 mA h g −1 at 300 and 700 mA g −1 , respectively. It suggests the Li 1.15 Mn 0.49 Ni 0.18 Co 0.18 O 2 nanoplates possess an excellent rate capability. After 200 cycles, the capacity retention ratio at 700 mA g −1 is still as large as 82.6%. The superior rate capability can be attributed to the shorter transport distance of lithium ions in these nanoplates with exposed (012) facet. The above results also indicate that the electrochemical performances of Li-rich layered oxides can be improved by allocating proper facets. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO 2 ) has been considered to be a promisingly alternative anode material for lithium-ion batteries and thus attracted wide research interest. But, its practical application in lithium-ion batteries is seriously impeded by low capacity and poor rate capability. In the present work, the electrochemical performance of TiO 2 is significantly improved by elaborately fabricating hierarchical structures. These as-prepared four hierarchical structure TiO 2 assembled by different building blocks (TO 2 -2 h, TO 2 -6 h, TO 2 -18 h and TO 2 -24 h) all exhibit impressed performance. More importantly, the TO 2 -6 h constructed by curved nanosheets exhibits the best performance, delivering a capacity of 231.6 mAh g −1 at 0.2C after 200 cycles, and capacities of 187.1 and 129.3 mAh g −1 at 1 and 10C after even 1200 cycles, respectively. The results indicated that design and fabrication of hierarchical structure is an effective strategy for significantly improving the electrochemical performance of TiO 2 electrodes, and the electrochemical performance of hierarchical structure TiO 2 is heavily dependent on its building blocks. It is suggested that thus excellent electrochemical performance may make TiO 2 -6 h a promising anode material for advanced lithium-ion batteries with high capacity, good rate capability and long life. [ABSTRACT FROM AUTHOR]

Mg-doped Li 2 FeSiO 4 /C is synthesized by using Fe 2 O 3 nanoparticle as iron source. Through Rietveld refinement of X-ray diffraction data, it is confirmed that Mg-doped Li 2 FeSiO 4 owns monoclinic P 2 1 / n structure and Mg occupies in Fe site in the lattice. Through energy dispersive X-ray measurement, it is detected that Mg element is distributed homogenously in the resulting product. The results of transmission electron microscopy measurement reveal that the effect of Mg-doping on Li 2 FeSiO 4 crystallite size is not obvious. As a cathode material for lithium-ion battery, this Mg-doped Li 2 FeSiO 4 /C delivers high discharge capacity of 190 mAh g −1 (the capacity was with respect to the mass of Li 2 FeSiO 4 ) at 0.1C and its capacity retention of 100 charge-discharge cycles reaches 96% at 0.1C. By the analysis of electrochemical impedance spectroscopy, it is concluded that Mg-doping can help to decrease the charge-transfer resistance and increase the Li + diffusion capability. [ABSTRACT FROM AUTHOR]

Developing energy storage equipments that can work at very high charge–discharge rate is crucial, but highly challenging for more efficient use of energy. From the perspective of chemistry, high-rate property of Li-ion batteries can only be achieved by significantly improving the kinetics of lithium ions and electrons in electrode. Here, we for the first time report on a simple method to resolve kinetics problems of ultrafast charging–discharging Li-ion batteries by fabrication of layered LiMO 2 (M = Mn, Co, Ni) hexagonal sheet exposing with facets {101}. The synthetic procedure of hexagonal sheets is proceeded via a simple PVP-assisted co-precipitation, which is followed by a heat treatment. All hexagonal sheets LiMn x Co y Ni z O 2 were demonstrated to deliver a superior excellent rate capability and outstanding cycle stability at high current density of 3000 mA g −1 and under a high cutoff voltage of 4.4 V. The discharge capacity for the composition LiMn 0.075 Co 0.775 Ni 0.15 O 2 at an ultrahigh charge–discharge rate of 10,000 mA g −1 is almost as large as that for LiMn 2 O 4 and commercial LiFePO 4 at low rate of 1C. The methodology reported here to resolve the kinetic problems of lithium ions and electrons in electrodes may have many implications that would help scientists to find more high-rate lithium-ion batteries for powering electric vehicles and other applications. [ABSTRACT FROM AUTHOR]

Neat ionic liquid electrolytes based on functionalized 1,3-dialkylimidazolium cation and bis(fluorosulfonyl)imide anion were investigated in MCMB/LiFePO 4 full cells with commercial electrodes for the first time. Ether functionalization could bring the prominent improvement of initial efficiency and the comparable cycle performance to a conventional carbonate-based electrolyte. In view of full cells, it was inferred that the further oxidation on cathode of the reduction products on anode during the charge process might result in the serious capacity loss of initial cycle. [ABSTRACT FROM AUTHOR]

Silicon anodes hold great promise for the next-generation energy dense lithium-ion batteries (LIBs) due to their high specific capacity, yet the capacity of silicon anodes rapidly decays during repeated charge/discharge processes, which can hardly be alleviated via conventional binders due to the poor mechanical properties, insufficient ion/electronic conduction, and weak adhesion force. Herein, a random terpolymer (AMS) with fast ion transport and robust adhesion force was developed via the radical polymerization of acrylic acid (AA), acrylamide (AM) and 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and used as aqueous binder for silicon/graphite (Si/C) anodes. The carboxyl and amide groups from AA and AM can form numerous of hydrogen bonds with the silicon particles, leading to a strong adhesion effect, while the sulfonic acid groups can construct fast channels for the rapid transport of lithium ions. Finally, the Si/C anode using the AMS411 binder delivers a high specific capacity of 322.48 mAh g−1 along with the superior operation stability at 0.5C (high-capacity retention ratio of 80.8 % after 500 cycles). This work provides that the incorporation of specific functional groups effectively enhances the overall electrochemical performance of the silicon-based anodes. An terpolymer is well designed by combining multiple functional groups including carboxyl, amino, and sulfonic acid moieties and used as aqueous binders to alleviate the volume effect of silicon based anode for high performance lithium ion batteries. [Display omitted] • A terpolymer with multiple functional groups is designed. • The terpolymer binder can alleviate the volume effect of the Si anode. • The mechanism of binding and ion transport acceleration is investigated. • The binder enables a superior electrochemical performance of the Si anode. [ABSTRACT FROM AUTHOR]

Li-rich layered oxide materials possess high voltage and high specific capacity, which makes them attractive cathode candidates for lithium-ion batteries. However, they still suffer from a poor rate capability, which seriously blocks their widespread practical applications. In this work, Li(Li 0.167 Mn 0.5 Co 0.167 Ni 0.167 )O 2 microspheres were synthesized by a hydrothermal-assisted method, in which Ni-Co-Mn-based microspherical precursors obtained by a hydrothermal process with polyethylene glycol-600 (PEG-600) as a surfactant were mixed with lithium sources and then sintered to yield the final products. It is found that the as-prepared Li-rich layered oxide microspheres exhibit high discharge capacity and superior rate performance: delivering an initial discharge capacity of 292 mAh g −1 at a current density of 20 mA g −1 , 189 mAh g −1 at a current density of 600 mA g −1 and 142 mAh g −1 at a current density of 2000 mA g −1 (10C), which are better than that of the sample as-prepared by co-precipitation method. The high discharge capacity and improved rate-capability were beneficial from the microspheres assembled by uniform primary particles around 250 nm, more reversible redox and better electrode kinetics comparing to that of the co-precipitation sample. The preparation strategy reported here may offer hints for achieving various advanced Li-rich layered composite materials that would be used in high-performance energy storage. [ABSTRACT FROM AUTHOR]

Although silicon (Si) anode has extremely high specific capacity, the damage to the electrode caused by the huge volume expansion greatly hinders its practical application in lithium-ion batteries. Aiming to alleviate this problem, a high-performance aqueous binder (AMNG) with gradient hydrogen bonding and flexible three-dimensional network structure is prepared by a one-pot method. Compared to the conventional linear polyacrylic acid (PAA) binder, the AMNG binder exhibits enhanced ionic conductivity and stress dissipation for Si nanoparticles, which is able to greatly reduce the side reactions caused by volume changes and considerably improve the electrochemical performance of Si anodes. As a result, the Si nanoparticles using the AMNG binder exhibit an initial discharge capacity as high as 3101 mAh g−1 with a Coulombic efficiency of 89.95%, and a capacity retention of 71.6% for 120 cycles, which are superior to the electrode using PAA, corresponding to 2832 mAh g−1, 88.37% and 28.1%, respectively. More prominently, the practical application of the AMNG binder is evaluated in high-mass-loading Si-based electrodes and even in full cells with LiFePO 4 , all showing satisfied performance. Therefore, this design approach is valuable as a reference for the preparation of commercial aqueous binders. [Display omitted] • An environmentally friendly binder is prepared by an aqueous one-pot method. • The binder embodies "gradient hydrogen bonding" and "elastic 3D network". • Nitrile groups and ether bonds boost the ionic conductivity of the binder. • The binder is universal for practical application of Si-based anodes. [ABSTRACT FROM AUTHOR]

New mixtures of 3-(2-methoxyethoxy)propanenitrile, fluoroethylene carbonate and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether are introduced as safe electrolytes for lithium-ion batteries. The electrolytes with 30 wt% 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether can own high safety and better wettability to separator and electrodes than the conventional electrolyte. The oxidation potentials of these electrolytes are about 4.8 V versus Li/Li + , and their conductivity can reach 5.42 mS cm −1 at 25 °C. Graphite/LiMn 2 O 4 coin cells are used to evaluate the electrochemical performances, and this kind of safe electrolytes can exhibit better rate and cycle performances than the conventional electrolyte. These results indicate that such ternary electrolytes have a great potential for practical application. [ABSTRACT FROM AUTHOR]

• The structure of spinel phase and Li-rich layered oxides (LLOs) is elucidated. • The influence of spinel phase on the eletrochemcial performance of LLOs is analyzed. • The suggestions of using spinel phase in the commercialization of LLOs are given.. Li-rich Layered Oxides (LLOs), considered as the most promising cathode material with high theoretical specific capacity (>250 mAh g−1) in Lithium-Ion Batteries (LIBs), still suffer from severe intrinsic weaknesses such as low initial coulombic efficiency, poor rate capability, limited cycle life and severe voltage decay. These drawbacks are believed to originate from Transition Metal (TM) ion migration, irreversible oxygen release and cathode-electrolyte interfacial reactions etc. Owing to similar cubic close-packed oxygen arrays with LLOs, spinel phase, which greatly facilitates the transport of Li-ion, protection from organic electrolyte, the suppression of structural collapse and pre-extraction combining with the accommodation of Li-ion at low voltage, is widely applied to ameliorate electrochemical performance. In this article, we systematically review recent progresses of spinel phase on LLOs and comprehensively summarize the effectiveness of proposed strategies in improving the electrochemical performance of LLOs, including surface coating, spinel-layered coherent component, in-situ spinel-layered integration and synergistic effects of spinel with other components. Finally, we discuss the main barrier to the commercialization of LLOs and give advice for future development of LLOs for high-energy–density LIBs. [ABSTRACT FROM AUTHOR]

Abstract: Composites Li[Li x Ni0.34−x Mn0.47Co0.19]O2 (0.18≤ x ≤0.21) were prepared by a solid state reaction method assisted with co-precipitating. The chemical composition, structure, morphology, and specific surface area of as-prepared composites were systematically characterized by ICP, XRD, SEM, and BET, respectively. The electrochemical performances of the composites were evaluated as high-voltage cathode for lithium-ion batteries. Among all the composites, sample SN exhibited a best electrochemical performance. Except for the initial decay, no obvious capacity fading was observed after cycling 30 cycles at different rates. The discharge capacities were maintained steadily as the current density increased up to 500mAg−1. The improved electrochemical performance of sample SN was attributed to the compromise effect between the increased Li2MnO3 phase and the enhanced Li/Ni disorder. [Copyright &y& Elsevier]

• A thorough analysis of existing and emerging binders for Si-based lithium-ion battery anodes. • The binders' working principles and electrochemical mechanisms are described. • Existing challenges and future research directions are provided. Silicon (Si)-based anodes have been intensively pursued as one of the most promising candidates for next-generation high-capacity electrodes in lithium-ion batteries (LIBs) due to their ultra-high theoretical capacity. However, huge volumetric change associated with the insertion and extraction of lithium-ions is a major impediment to the deployment of Si anodes, which result in the pulverization of Si particles and the loss of electric contact, as well as parasitic side reactions; these transformations cause poor cyclic stability and fast capacity fading. Binders, with minor content in electrode systems, have demonstrated their pivotal role in electrodes, particularly in Si-based anodes. Present review aims at providing a thorough analysis of existing and emerging binders, which are either synthetic or biomass polymers, for Si-based LIB anodes in terms of their structures, properties, advantages, limitations, working principles, design rules, as well as associated electrochemical mechanisms to address the challenges of Si-based anodes. On the basis of current progress, a short perspective is provided on existing challenges and research directions on Si-based anodes for commercialization in the near future. [ABSTRACT FROM AUTHOR]

• Ultrahigh dispersed MoO x on N-doped hierarchically porous carbon was prepared. • It shows a high specific capacity of 742 mAh g−1 at 100 mA g−1. • A good stability was achieved with 431 mAh g−1 after 1000 cycles at 1000 mA g−1. • MoO x and N-doped porous carbon synergistically contribute to the performance. Transition-metal oxides based materials have recently been shown to be promising anode material for lithium ion batteries (LIBs) application to replace graphite material. In the present work, highly dispersed ultra-small MoO x nanoparticles anchored on N-doped three-dimensional (3D) hierarchically porous carbon (3D-MoO x @CN) are prepared on the basis of an efficient in-situ chelating and hard-templating strategy. The MoO x nanoparticles with particle sizes between 1.5 and 3.5 nm are observed to be anchored on the surface of the 3D N-doped carbon. The 3D-MoO x @CN composite anode electrode exhibits several appealing characteristics for lithium ion storage, including high specific capacity, good stability against cycling and fast charge transport kinetics. An optimized 3D-MoO x @CN sample (3D-MoO x @CN-700) delivers specific capacities of 742 mAh g−1 at current density of 100 mA g−1 and 431 mAh g−1 at 1000 mA g−1 after 1000 cycles, respectively. The observed excellent performance is due to the unique hierarchical pore structure with strong binding of the ultra-small MoO x nanoparticles onto N-doped carbon surface, which can avoid the agglomeration and alleviate the volume expansion of MoO x nanoparticles in the charge-discharge process. The composite electrode material described in this work holds a great potential for the development of high-performance lithium-ion batteries. Meanwhile, the synthesis method presents a common strategy to prepare other composite materials with highly dispersed metal oxide on the hierarchically porous carbon materials. [ABSTRACT FROM AUTHOR]