The blossoming of mobile electronic devices, plug-in electric vehicles and stationary energy storage have triggered the urgent demand for the exploration of the energy storage systems with high energy density and long cycle life. Lithium-sulfur battery is regarded as one of the most promising candidates of the next-generation rechargeable batteries, since the active substance sulfur is low cost and possesses high theoretical energy density of 2600 Wh.kg(-1). However, the practical applications of lithium-sulfur battery are hindered by a series of severe problems, which are caused by the insulative nature of sulfur and its discharge products, and the dissolution and shuttling of polysulfides. Carbonaceous materials are generally used as sulfur hosts to improve the conductivity of the cathode. Regrettably, due to the weak interaction between non-polar carbonaceous materials and polar polysulfides, the carbonaceous materials can inhibit polysulfides only by limited physical adsorption and restrictions, thus the dramatic capacity decline derived from the notorious "shuttling effect" remains insufficiently resolved. Introducing polar or chemical adsorption sites to carbonaceous materials by element doping, such as N, S, Co and B doping, can greatly enhance the adsorption capacity of carbonaceous materials to polysulfides, so as to sufficiently improve the cycling stability of the cell. Moreover, element doping may improve the electronic conductivity of carbonaceous materials by changing their electronic structure, thus effectively increasing the utilization ratio of the active materials. This article reviews the elements doping commonly applied in carbonaceous materials such as porous carbon, carbon nanotubes and graphene for lithium-sulfur batteries, wherein single-element doping, dual-element doping, and multi-element doping are introduced separately. The effects of different doping elements on performance of carbonaceous materials are analyzed. And the development direction of element-doped carbonaceous materials in lithium-sulfur batteries are prospected.

Main observation and conclusionIn an attempt to overcome the drawbacks of high-capacity layered lithium-rich cathodes xLi(2)MnO(3)center dot(1-x) LiMO2 (0 < x < 1, M = Mn, Ni, and Co), the spinel clothed layered heterostructured materials, x'Li4Mn5O12 center dot(1-x') Li[Li0.2Mn0.55Ni0.15Co0.1]O-2 (x' = 0.01, 0.03, 0.05) have been proposed and synthesized as high-performance cathode materials for high-energy and high-power Li-ion batteries. Based on the characterizations of X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman scattering spectroscopy, it is indicated that ultrathin 3 V spinel Li4Mn5O12 has been successfully clothed on the layered lithium-rich cathode. Electrochemical tests demonstrate the sample 0.01Li(4)Mn(5)O(12)center dot 0.99 Li[Li0.2Mn0.55Ni0.15Co0.1]O-2 with an ultrathin clothing layer of spinel phase, exhibits the highest reversible capacity of 289.4 mAh g(-1) and maintains 259.8 mAh g(-1) after 80 cycles at 0.1 C rate. Meanwhile, it delivers outstanding rate discharge capacities of 229.4 mAh g(-1) at 1 C, 216.8 mAh g(-1) at 2 C and 184.4 mAh g(-1) at 5 C as well as alleviated voltage fade. It is believed the ultrathin clothing spinel layer plays a vital role in the modification of the materials kinetics, and structural and electrochemical stability of the heterostructured cathode.[GRAPHICS].

Lithium-rich manganese-based oxides(LRMOs)have been considered as one of the most promising cathode materials owing to their superior specific capacity and high operating voltage.However,their largescale commercial ap

Layered lithium- & manganese-rich oxides (LMR), with their high capacity and cost-effective advantage, are considered as a potent alternative of the next-generation cathode material for lithium-ion batteries. The behaviors of the electrode-electrolyte interphase (EEI) are crucial to the electrochemical properties of LMR as a cathode material operating at wide voltage regions (from 2 to 4.8 V). Nonetheless, the understanding of EEI for LMR materials and the related renovation techniques are somewhat lacking. Herein, we gain insight into the EEI change mechanism for LMR materials during long electrochemical cycles and demonstrate a renovating method to mitigate its deterioration. As for the pristine electrode based on LMR materials, the increasing amount of POxFyz− and metal fluorides lead to unpleasant degradation for both the EEI and the active material particle, causing evident performance decay. Whereas, the lithium phosphate, if employed in the electrode, effectively enhances the lithium ions transfer, impedes the decomposition of electrolyte salt, and leads to a more stable EEI, thus promoting the electrochemical performances of LMR materials. All results indicate that the EEI should be one of the critical components for comprehensively understanding the LMR material, and the success renovation by the lithium phosphate offers a new orientation for those intrinsic drawbacks of LMR material. © 2019

可移动电子设备、电动汽车及站式储能的蓬勃发展对具有高能量密度和长循环寿命的储能体系的开发提出了迫切需求。锂硫电池由于活性物质硫成本低廉并具有高理论能量密度(2600 Wh·kg-1),成为最具希望的下一代可充电电池。但是,硫及其放电产物导电性差以及多硫化物溶解穿梭导致的一系列严重问题制约了锂硫电池的实际应用。碳基材料通常被用作硫载体以改善正极的导电性,然而,非极性碳材料与极性多硫化物的相互作用较弱,对于多硫化物仅起到有限的物理吸附和阻挡作用,穿梭效应所导致的电池容量严重衰减问题难以得到有效改善。通过杂原子如N、S、Co、B等的掺杂可在碳材料上引入极性或化学吸附位点,大大增强了碳材料对于多硫化物的吸附能力,有效改善了电池的循环稳定性,并且由于掺杂改变了碳材料的电子结构,甚至可以提升碳材料的电子导电性,从而提高了活性物质的利用率。本文对锂硫电池中多孔碳、碳纳米管以及石墨烯等碳基材料常用的元素掺杂进行了介绍,其中包括单元素掺杂、双元素掺杂和多元素掺杂,分析了不同掺杂元素对碳基材料性能的影响,并对元素掺杂碳基材料在锂硫电池中的发展前景进行了展望。

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. © 2020

Designing the optimum cathode configuration for lithium-sulfur (Li-S) batteries has held tremendous scientific momentum to achieve high energy density, fast reaction kinetics, and superior cycle retention. Herein, a self-standing and flexible PPyprGO/CNTs (PCG) paper as sulfur host is constructed by integrating multiwalled carbon nanotubes into polypyrrolepreduced graphene oxide hybrid structure, rooted from in situ redox reaction and spontaneous assembly of pyrrole and graphene oxide. The three-dimensional (3D) corrugated papery frameworks with carbon nanotube (CNT) pillars deliver a highly conducting pathway for electron and ion transfer. Theoretical calculations indicate that ample nitrogen- and oxygen-containing functional groups can form strong polar-polar interaction with lithium polysulfides. Thus, the assembled lightweight PCG-S electrode exhibits a high gravimetric capacity of 1201.9 mA h g(-1) and retains 727.8 mA h g(-1) at 0.2 C after 450 cycles, remarkable rate performance, and excellent cyclic stability with an ultralow decay rate of 0.044% per cycle during 200 cycles at 1 C. Delightedly, thanks to its unique structure, the volumetric sulfur loading amount in the flexible electrode can reach ca. 0.82 g cm(-1), which endows the cathode with an ultrahigh volumetric capacity of 975 A h L-1 at 0.2 C simultaneously. This dense monolithic paper appears to be a scalable potential for developing high-performance cathodes in emerging flexible devices.

With the rapid development of wearable and flexible electronic equipment, the flexible electrochemical energy storage devices with high energy density and high power density have been widely interested and researched in numerous studies. The flexible energy storage devices, mainly include flexible solar batteries, flexible lithium batteries and flexible supercapacitors. As the core components of these devices, flexible electrodes should possess not only basic mechanical flexibility, but also excellent electrical conductivity and superior skeleton supporting strength, so as to ensure the energy storage devices tolerate various deformation such as stretching, bending and twisting and exert their electrochemical performance steadily. As the research goes deep, carbon nanotubes, carbon nanofibers, carbon cloth, polymer, metal compounds and their composites, with different macromorphology and micromorphology, have been reported as flexible matrix for electrodes in a large amount of literature recently. In this review, based on the materials and microstructures, different assembling methods for different microstructures including stacking structure, foam structure, weave structure, grafting structure, etc., for fabricating flexible electrodes, are illustrated. Also the existing methods for quantitatively evaluating the electrode flexibility are summarized. Finally, the major challenges in the future development for the flexible electrodes are illustrated and the prospects are forecast.