三(2-羧乙基)膦阻隔层对锂硫电池穿梭效应的抑制

为了抑制热力学穿梭效应, 改善锂硫电池的电化学性能. 将三(2-羧乙基)膦芳纶纸中间层(TCEP-AP)嵌在锂硫电池正极和隔膜之间. 通过透射电子显微镜(TEM)、 扫描电子显微镜(SEM)、 红外光谱和元素能谱分析(EDS)等对材料进行结构和性能表征. 电化学实验表明, TCEP是一种特别有效的多硫化物剪切剂, 在0.1C倍率时, S-TCEP-AP 锂硫电池的初始放电容量达到1544 mA·h·g ^-1. 在1C倍率下循环400次后, 比放电容量仍维持在609 mA·h·g ^-1, 衰减率极低(每周衰减0.029%), 展现出良好的倍率和循环性能.     

Bimetal-organic frameworks derived Co/N-doped carbons for lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have received extensive attention due to their high theoretical specific energy density. However, the utilization of sulfur is seriously reduced by the shuttle effect of lithium polysulfides and the low conductivity of sulfur and lithium sulfide (Li₂S). Herein, we introduced bimetal-organic frameworks (Co/Zn-ZIF) derived cobalt and nitrogen-doped carbons (Co/N-C) into Li-S batteries through host design and separator modification. The Co/N-C in Li-S batteries effectively limits the shuttle effect through simultaneously serving as polysulfide traps and chemical catalyst. As a result, the Li-S batteries deliver a high reversible capacity of 1614.5 mAh/g and superior long-term cycling stability with a negligible capacity decay of only 0.04% per cycle after 1000 cycles. Furthermore, they have a high area capacity of 5.5 mAh/cm².     

Regulating the Deposition of Insoluble Sulfur Species for Room Temperature Sodium-Sulfur Batteries

Room temperature sodium-sulfur(RT-Na-S) batteries are regarded as promising candidates for next-generation high-energy-density batteries. However, in addition to the severe shuttle effect, the inhomogeneous deposition of the insoluble sulfur species generated during the discharge/charge processes also contributes to the rapid capacity fade of RT-Na-S batteries. In this work, the deposition behavior of the insoluble sulfur species in the traditional slurry-coated sulfur cathodes is investigated using microporous carbon spheres as model sulfur host materials. To achieve uniform deposition of insoluble sulfur species, a self-supporting sulfur cathode fabricated by assembling microporous carbon spheres is designed. With homogeneous sulfur distribution and favorable electron transport pathway, the self-supporting cathode delivers remarkably enhanced rate capability(509 mA·h/g at 2.5 C, 1 C=1675 mA/g), cycling stability(718 mA·h/g after 480 cycles at 0.5 C) and areal capacity(4.98 mA·h/cm² at 0.1 C), highlighting the great potential of manipulating insoluble sulfur species to fabricate high-performance RT-Na-S batteries.     

Atomically Dispersed Fe-N4 Sites and Fe3C Particles Catalyzing Polysulfides Conversion in Li-S Batteries

Lithium-sulfur(Li-S) batteries have been puzzled by the “shuttle effect”. In the recent years, catalytic materials present a huge potential for solving this problem. However, the exploitation for catalytic activity was still challenging in Li-S batteries. In this article, we put forward a single atom catalyst (SAC) of FeN₄ coupled with Fe₃C on the N-doped carbon (FeN₄/Fe₃C@NC) by one-step pyrolysis method. The FeN₄ and Fe₃C synergistically catalyze the polysulfides conversion when the N-doped carbon provides the high conductive three-dimensional skeleton in Li-S batteries. As a result, the FeN₄/Fe₃C@NC shows a specific capacity of 1100 mA·h/g at 0.2 C(1 C=1675 mA/g). In addition, the FeN₄/Fe₃C@NC maintains 99.01% of the pristine specific capacity after 100 cycles at 0.5 C, indicating the improved electrochemical performance in Li-S batteries. This work sheds new lights on the design of engineering catalysts for developing high-performance Li-S batteries.     

Li Ion Exchanged α-MnO2 Nanowires as Efficient Catalysts for Li-O2 Batteries

Due to the limited energy densities, which could be achieved by lithium-ion cells, Li-O₂ batteries, which could provide a promising super energy storage medium, attract much attention nowadays. For its high activity, high storage and low cost, Mn-based oxides have shown versatile application in various batteries. To enhance the cyclability of Li-O₂ batteries, here, we synthesized a kind of α-MnO₂ nanowires as a bifunctional catalyst for Li-O₂ batteries. The particular structure of α-MnO₂ reduces the mass transfer resistance of the battery, and the MnO₂ nanowires were ion exchanged by saturated lithium sulfate solution so as to further improve the performance of the catalyst. The exchanged α-MnO₂ catalyst showed a high discharge specific capacity(6243 mA·h/g at a current density of 200 mA/g) and significantly improved the cyclability up to the 55th cycle(200 mA/g with capacity of 1000 mA·h/g). The results show that the Li ion exchange method is a promising strategy for improving the performance of MnO₂ catalyst for Li-O₂ batteries.     

PEO基聚合物电解质及其锂硫电池性能研究

锂硫电池由于具有高的理论比能量引起了广泛关注,然而传统液态锂硫电池由于多硫化物的“穿梭效应”以及安全问题而限制了其应用,全固态锂硫电池可显著提高电池安全性能并有望解决多硫化物的穿梭问题. 本文采用传统的溶液浇铸法制备了具有不同的[EO]/[Li⁺]的PEO-LiTFSI聚合物电解质,并将其应用于锂硫电池. 研究发现,虽然[EO]/[Li⁺] = 8的聚合物电解质具有更高的离子电导率,但是[EO]/[Li⁺] = 20的电解质与金属锂负极间的界面阻抗更低,界面稳定性更好. Li|PEO-LiTFSI([EO]/[Li⁺]=20)|Li对称电池在60 °C,电流密度为0.1 mA·cm^-2时可稳定循环超过300 h,而Li|PEO-LiTFSI ([EO]/[Li⁺]=8)|Li对称电池循环75 h就出现了短路现象. 基于PEO-LiTFSI([EO]/[Li⁺]=20)电解质的锂硫电池首圈放电比容量为934 mAh·g^-1,循环16圈后放电比容量为917 mAh·g^-1以上. 而基于PEO-LiTFSI ([EO]/[Li⁺]=8)电解质的锂硫电池,由于与锂负极较低的界面稳定性不能够正常循环,首圈就出现了严重过充现象.     

Hollow Micro-/Nanostructure Reviving Lithium-sulfur Batteries

High-energy-density lithium-sulfur(Li-S) batteries are drawing dramatic research interests to fulfill the ever-increasing demands of electrical vehicles. However, challenges with the insulating property of sulfur and its lithiation products and its large volume expansion, and the shuttle effect of lithium polysulfides, hinder the commercial application of Li-S batteries. Lots of material design concepts have been developed to address the failure modes. Among them, hollow micro-/nanostructures with abundant compositional and geometrical feasibility have been proved fruitful in addressing the current obstacles of Li-S batteries. Here, typical examples of designing hollow micro-/nanostructures to address the problems of Li-S batteries and simultaneously improve the practical capacity and lifespan are highlighted. In particular, the great effect of structural engineering on minimizing volume change, inhibiting the shuttle effect and catalyzing polysulfide conversion are discussed systematically. Finally, future directions of hollow nanostructure design to enhance the progress of Li-S batteries are also provided.     

氮硫共掺杂多孔碳材料的制备及其在锂硫电池中的应用

锂硫电池因其较高的理论容量和对环境友好等优势被视为极具发展潜力的储能装置,但是多硫化物的穿梭效应极大地限制了锂硫电池的实际应用。本文以葡萄糖为碳源,离子液体为氮源和硫源,KCl和ZnCl₂为模板剂,KOH为活化剂,通过热解工艺合成了氮硫共掺杂多孔碳（NSPC）。XPS和极性吸附实验表明N、S杂原子成功引入并且提高了碳材料对多硫化物的吸附能力,有效缓解多硫化物的穿梭效应,而较高的比表面积（1290.67 m²·g^-1）有助于提高硫负载量。负载70.1wt.%的硫后（S@NSPC）作为锂硫电池的正极材料表现出了良好的电化学性能。在167.5 mA·g^-1的电流密度下S@NSPC的首次放电容量为1229.2 mAh·g^-1,远高于S@PC的861.6 mAh·g^-1,且S@NSPC循环500圈后容量为328.1 mAh·g^-1。当电流密度从3350 mA·g^-1恢复至167.5 mA·g^-1时,可逆容量达到首圈放电比容量的80%,几乎恢复至其初始值。     

Trithiocyanuric acid derived g-C_3N_4 for anchoring the polysulfide in Li-S batteries application

Lithium-sulfur (Li-S) batteries have great potential as an electrochemical energy storage system because of the high theoretical energy density and acceptable cost of financial and environment.However,the shuttle effect leads to severe capacity fading and low coulombic efficiency.Here,graphitic carbon nitride(g-C_3N_4) is designed and prepared via a feasible and simple method from trithiocyanuric acid (TTCA) to anchor the polysulfides and suppress the shuttle effect.The obtained g-C_3N_4 exhibits strong chemical interaction with polysulfides due to its high N-doping of 56.87 at%,which is beneficial to improve the cycling stability of Li-S batteries.Moreover,the novel porous framework and high specific surface area of g-C_3N_4 also provide fast ion transport and broad reaction interface of sulfur cathode,facilitating high capacity output and superior rate performance of Li-S batteries.As a result,Li-S batteries assembled with g-C_3N_4 can achieve high discharge capacity of 1200 mAh/g at 0.2 C and over 800 mAh/g is remained after 100 cycles with a coulombic efficiency more than 99.5%.When the C-rate rises to 5 C,the reversible capacity of Li-S batteries can still maintain at 607mAh/g.     

镶嵌于NH2-MIL-125 (Ti)衍生氮掺多孔碳中的花状超细纳米TiO2作为高活性和稳定性的锂离子电池负极材料

由于具有高安全性和优异的循环稳定性,二氧化钛(TiO₂)作为负极材料被广泛地应用于锂离子电池领域。但是较差的导电性和离子传输速率限制了TiO₂的进一步应用和发展。鉴于此,我们以花状NH₂-MIL-125 (Ti)为前驱体和硬模板,成功合成出了具有花状结构的超细纳米TiO₂/多孔氮掺杂碳片(N-doped porous carbon)复合物(记为FL-TiO₂/NPC)。过程中所制备的纳米TiO₂-金属有机构架(Ti-MOF)展现出由二维褶皱多孔纳米片堆积、组装而成的花状结构。一方面,二维褶皱纳米片包含TiO₂纳米颗粒可以增大活性物质与电解液的接触面积;另一方面,氮掺杂多孔碳基体可以提高整体复合物的导电性和结构完整性。将所获得的FL-TiO₂/NPC作为负极组装成的锂半电池, 在0.5 A·g^-1、300圈后仍有384.2 mAh·g^-1以及在1 A·g^-1、500圈仍有279.1 mAh·g^-1的比容量。进一步性能测试表明,在2 A·g^-1、2000圈长循环测试后,其仍能保持256.5 mAh·g^-1的比容量和接近100%的库伦效率。该优异的电化学活性和稳定性主要起源于材料独特的花状结构。我们的合成策略为今后制备高储锂性能的金属氧化物/多孔氮掺杂碳负极提供了一种新的思路。     

单原子催化剂在锂硫电池中的研究进展

锂硫电池因其较高的理论比容量和能量密度而成为最有前途的下一代储能系统之一。然而,硫和放电产物硫化锂的低导电率、可溶性多硫化锂（LiPSs）的穿梭以及缓慢的反应动力学致使锂硫电池的循环寿命短、倍率性能低。近年来,研究表明具有强催化活性的单原子（SAs）是理想的LiPSs锚定中心和催化位点。用SAs修饰正极和隔膜有助于吸附多硫化物并催化其转化,修饰负极则可显著提高锂的剥离/沉积效率,抑制锂枝晶的生长。本文综述了SAs在锂硫电池中的研究进展,包括材料合成、表征方法以及应用方向。最后,对SAs应用在电池中所面临的挑战和未来发展方向进行总结。     

Improved Initial Charging Capacity of Na-poor Na0.44MnO2 via Chemical Presodiation Strategy for Low-cost Sodium-ion Batteries

Sodium-ion batteries(SIBs)are promising for grid-scale energy storage applications due to the natural abundance and low cost of sodium.Among various Na insertion cathode materials,Na0.44MnO2 has attracted the most attention because of its cost effectiveness and structural stability.However,the low initial charge capacity for Na-poor Na0.44MnO2 hinders its practical applications.Herein,we developed a facile chemical presodiated method using sodiated biphenly to transform Na-poor Na0.44MnO2 into Na-rich Na0.66MnO2.After presodiation,the initial charge capacity of Na0.44MnO2 is greatly enhanced from 56.5 mA·h/g to 115.7 mA·h/g at 0.1 C(1 C=121 mA/g)and the excellent cycling stability(the capacity retention of 94.1%over 200 cycles at 2 C)is achieved.This presodiation strategy would open a new avenue for promoting the practical applications of Na-poor cathode materials in sodium-ion batteries.     

Enhanced Electrochemical Performance of Na0.67Fe0.5Mn0.5O2Cathode with SnO2 Modification

P2-type layered oxide Na_0.67Fe_0.5Mn_0.5O₂ is recognized as a very promising cathode material for sodium-ion batteries due to the merits of high capacity, high voltage, low cost, and easy preparation. However, its unsatisfactory cycle and rate performances remain huge obstacles for practical applications. Here, we report a strategy of SnO₂ modification on P2-type Na_0.67Fe_0.5Mn_0.5O₂ to improve the cycle and rate performance. Scanning electron microscope(SEM) and transmission electron microscope(TEM) images indicate that an insular thin layer SnO₂ is coated on the surface of Na_0.67Fe_0.5Mn_0.5O₂ after medication. The coating layer of SnO₂ can protect Na_0.67Fe_0.5Mn_0.5O₂ from corrosion by electrolyte and the cycle performance is well enhanced. After 100 cycles at 1 C rate(1 C=200 mA/g), the capacity of SnO₂ modified Na_0.67Fe_0.5Mn_0.5O₂ retains 83 mA·h/g(64% to the initial capacity), while the capacity for the pristine Na_0.67Fe_0.5Mn_0.5O₂ is only 38 mA·h/g(33.5% to the initial capacity). X-Ray photoelectron spectroscopy reveals that the ratio of Mn⁴⁺ increases after SnO₂ modification, leading to less oxygen vacancy and expanded lattice. As a result, the capacity of Na_0.67Fe_0.5Mn_0.5O₂ increases from 178 mA·h/g to 197 mA·h/g after SnO₂ modification. Furthermore, the rate performance of Na_0.67Fe_0.5Mn_0.5O₂ is enhanced with SnO₂ coating, due to high electronic conductivity of SnO₂ and expanded lattice after SnO₂ coating. The capacity of SnO₂ modified Na_0.67Fe_0.5Mn_0.5O₂ at 5 C increases from 21 mA·h/g(pristine Na_0.67Fe_0.5Mn_0.5O₂) to 35 mA·h/g.     

Solution-based Preparation of High Sulfur Content Sulfur/Graphene Cathode Material for Li-S Battery

Practical Li-sulfur batteries require the high sulfur loading cathode to meet the large-capacity power demand of electrical equipment.However,the sulfur content in cathode materials is usually unsatisfactory due to the excessive use of carbon for improving the conductivity.Traditional cathode fabrication strategies can hardly realize both high sulfur content and homogeneous sulfur distribution without aggregation.Herein,we designed a cathode material with ultrahigh sulfur content of 88%(mass fraction)by uniformly distributing the water dispersible sulfur nanoparticles on three-dimensionally conductive graphene framework.The water processable fabrication can maximize the homogeneous contact between sulfur nanoparticles and graphene,improving the utilization of the interconnected conductive surface.The obtained cathode material showed a capacity of 500 mA·h/g after 500 cycles at 2.0 A/g with an areal loading of 2 mg/cm2.This strategy provides possibility for the mass production of high-performance electrode materials for high-capacity Li-S battery.     

锂硫电池正极材料的制备及工艺优化

锂硫电池具有能量密度高、价格低等优势,有希望应用于下一代储能领域. 但锂硫电池仍然存在一些问题,如多硫化物穿梭效应、缺乏有效的锂硫电池规模制备工艺等. 为了解决这些问题,作者以不同商用碳材料（乙炔黑、科琴黑与碳纳米管）和单质硫复合作为正极材料,探究正极制备工艺对多硫化物穿梭效应抑制效果及锂硫电池性能的影响. 通过研究,作者得出以下结论：科琴黑作为单质硫的载体,与单质硫球磨8 h后,匹配粘结剂聚乙烯吡咯烷酮（PVP）制备的正极浆料可实现在涂布和辊压后极片的厚度达到500 μm、压实密度达到991.65 mg·cm ^-3. 作者将最终得到的正极极片应用于高硫载量锂硫软包电池,电池首圈放电容量为137.4 mA·h,经过10圈循环后,放电容量为115.5 mA·h,表现出优异的电化学性能. 该碳硫复合正极材料制备工艺有望在锂硫电池的宏量制备中获得应用.     

用纳米羟基磷灰石@多孔碳构建锂硫电池高效反应界面

由于正极活性物质硫具有能量密度高、成本低廉和储量丰富等优点,锂硫（Li-S）电池受到了人们的极大关注。然而,锂硫电池充放电过程中产生的多硫化锂的“穿梭效应”严重阻碍了其实用化进程。为了解决这个问题,本研究借助动物软骨的组成和结构特点,制备了纳米羟基磷灰石@多孔碳（nano-HA@CCPC）复合材料,并以此设计了面向正极的锂硫电池隔膜涂层。研究表明,纳米羟基磷灰石不仅对多硫化物具有吸附固定作用,并且对多硫化锂的转化具有催化作用,加快了多硫化锂的氧化还原动力学,有效地提升了活性物质硫的利用率。另外,软骨基碳复合材料的多孔结构形成了很好的导电网络,为电化学反应提供了优良的电子传导路径;也有利于电解液的浸润,加快了离子传输;碳的氮原子掺杂进一步限制了多硫化物的穿梭效应。因此,采用nano-HA@CCPC隔膜涂层的锂硫电池表现出较长的循环寿命、低的容量损失以及高的倍率性能。在0.5 C下,循环325次后,电池仍然能保持815 mAh·g^-1的放电比容量,并且每次的容量衰减率仅为0.051%。nano-HA@CCPC的设计制备将为锂硫电池的发展提供新材料。     

锂硫电池中硒缺陷WSe2催化性能的理论研究

二硒化钨具有优异导电性、高比表面积和大间距层状结构等特点,能作为催化材料有效提升锂硫电池的性能;然而少量的边缘活性位点阻碍了其催化活性的进一步提升.通过引入原子空位制造表面缺陷,可使其暴露更多的表面活性位点,提高催化活性.本文通过第一性原理计算考察了不同Se空位缺陷浓度(3.125%,6.25%,9.375%和12.5%)WSe₂表面的多硫化物吸附能力、锂离子迁移能力和多硫化物转化能力,探究了缺陷改性硒化钨在锂硫电池中的应用潜力.结果表明,6.25%中等空位缺陷浓度的WSe₂表面具有适中的多硫化物吸附能力、快速的锂离子迁移和对于充电放电过程的同步促进作用,是最优势的表面;3.125%的低空位缺陷WSe₂表面对于多硫化物吸附、锂离子迁移和充放电过程均不利;9.375%和12.5%的高空位缺陷WSe₂表面虽然有利于锂离子迁移,但是对于短链多硫化物的吸附能力过强,同时不利于放电过程.     

锂离子电池TiO2纳米管负极材料

锂离子电池负极材料二氧化钛(TiO₂)由于其零应变、环境友好和高安全性近年来得到了广泛的研究,但其较低的电子电导和离子迁移率以及较低的比容量(335 mAh·g^-1)限制了其应用前景.本文梳理了一种纳米结构TiO₂纳米管(TNTs)的研究历程以及最近研究进展,综述了TNTs常见的几种制备方法,即水热法、阳极氧化法和模板法及其形成机理,归纳了各种制备方法的优缺点,讨论了制备过程中各项参量对制得TNTs的影响.阐述了其晶体结构与形貌对电化学性能的影响,指出晶格取向一致、管壁厚度小,纳米管开口且同向排列的TNTs具有更好的电化学性能.同时探讨了针对该材料电导性差、比容量低而进行的包括结构设计、掺杂、复合等一系列改进措施,指出与高电导率及高比容量材料复合是一种方便有效的改进措施.最后总结了各种改性方法取得的进展及存在的不足,展望了TNTs的研究趋势和发展前景.     

Dense Sphene-type Solid Electrolyte Through Rapid Sintering for Solid-state Lithium Metal Battery

The sphene-type solid electrolyte with high ionic conductivity has been designed for solid-state lithium metal battery. However, the practical applications of solid electrolytes are still suffered by the low relative density and long sintering time of tens of hours with large energy consumption. Here, we introduced the spark plasma sintering technology for fabricating the sphene-type Li_1.125Ta_0.875Zr_0.125SiO₅ solid electrolyte. The dense electrolyte pellet with high relative density of ca. 97.4% and ionic conductivity of ca. 1.44×10^-5 S/cm at 30℃ can be obtained by spark plasma sintering process within the extremely short time of only ca. 0.1 h. Also the solid electrolyte provides stable electrochemical window of ca. 6.0 V(vs. Li⁺/Li) and high electrochemical interface stability toward Li metal anode. With the enhanced interfacial contacts between electrodes and electrolyte pellet by the in-situ formed polymer electrolyte, the solid-state lithium metal battery with LiFePO₄ cathode can deliver the initial discharge capacity of ca. 154 mA·h/g at 0.1 C and the reversible capacity of ca. 132 mA·h/g after 70 cycles with high Coulombic efficiency of 99.5% at 55℃. Therefore, this study demonstrates a rapid and energy efficient sintering strategy for fabricating the solid electrolyte with dense structure and high ionic conductivity that can be practically applied in solid-state lithium metal batteries with high energy densities and safeties.     

Nitrogen-doped Carbon Coated Na3V2(PO4)3 with Superior Sodium Storage Capability

Cathodes with high cycling stability and rate capability are required for ambient temperature sodium ion batteries in renewable energy storage application. Na₃V₂(PO₄)₃ is an attractive cathode material with excellent electrochemical stability and fast ion diffusion coefficient within the 3D NASICON structure. Nevertheless, the practical application of Na₃V₂(PO₄)₃ is seriously hindered by its intrinsically poor electronic conductivity. Herein, solvent evaporation method is presented to obtain the nitrogen-doped carbon coated Na₃V₂(PO₄)₃ cathode material, delivering enhanced electrochemical performances. N-Doped carbon layer coating serves as a highly conducting pathway, and creates numerous extrinsic defects and active sites, which can facilitate the storage and diffusion of Na⁺. Moreover, the N-doped carbon layer can provide a stable framework to accommodate the agglomeration of the electrode upon electrode cycling. N-Doped carbon coated Na₃V₂(PO₄)₃(NC-NVP) exhibits excellent long cycling life and superior rate performances than bare Na₃V₂(PO₄)₃ without carbon coating. NC-NVP delivers a stable capacity of 95.9 mA·h/g after 500 cycles at 1 C rate, which corresponds to high capacity retention(94.6%) with respect to the initial capacity(101.4 mA·h/g). Over 91.3% of the initial capacity is retained after 500 cycles at 5 C, and the capacity can reach 85 mA·h/g at 30 C rate.