锂硫电池用多孔碳/硫复合正极材料的研究

锂硫电池具有高的理论比容量和理论能量密度,被认为是当前最有前景的二次电池体系之一。现阶段锂硫电池的研究工作主要集中于高性能硫正极材料的设计与合成。具有优良的导电性、良好的结构稳定性和多孔结构的纳米碳材料,比如活性碳、介孔碳、超小微孔碳、多级结构多孔碳、空心碳球和空心碳纤维,充分满足了锂硫电池正极材料对碳基体的要求。本文综述了近年来多孔碳/硫复合材料作为硫正极的研究进展。总结了以具有不同结构特征的多孔碳基体负载硫组装的锂硫电池的电化学性能,并分析了不同多孔结构对性能的影响。最后在此基础上,从多孔碳/硫复合正极材料的设计和合成的角度,展望了其未来的发展趋势。     

硝酸锂作添加剂对锂硫电池电化学性能的影响

采用充放电测试和交流阻抗测试研究了硝酸锂作电解液添加剂对锂硫电池电化学性能的影响. 采用电子扫描显微镜观察分析了添加剂对锂负极的影响, 探讨了硝酸锂的作用机理.  结果表明, 采用硝酸锂作为锂硫电池电解液的添加剂, 可以在锂负极表面形成具有钝化负极活性表面及保护锂负极的界面膜.  该膜可以抑制电解液中高价态聚硫离子与锂负极的副反应, 避免在锂负极表面形成不可逆的硫化锂, 从而提高锂硫电池的循环性能和放电容量. 采用硝酸锂作添加剂的锂硫电池首次放电比容量达1172 mA?h/g, 循环100次比容量保持为629 mA?h/g.     

兼具高负载量和高性能的碳/硫复合材料的低成本合成

正单质硫能够与锂离子在正极发生多电子反应,使得锂硫电池具有高达2567 W?h?kg~(-1)的理论能量密度,因而锂硫电池也成为了目前锂离子电池的研究焦点~1。然而,要实现锂硫电池的大规模应用仍面临诸多挑战,包括:锂枝晶的形成导致     

V2O3空心球的制备及在锂硫电池中的应用

在NH₃辅助下将制备的V₂O₅空心球高温还原为V₂O₃空心球, 并利用透射电子显微镜、 扫描电子显微镜、 X射线衍射和X射线光电子能谱等手段对材料的形貌与结构进行表征. 将V₂O₃空心球与硫机械混合后, 不经过熔融复合直接作为锂硫电池的正极材料. 电化学测试结果显示, 在0.2C倍率下, 电池首次放电比容量达到1375 mA·h/g, 循环100次后放电比容量可以维持在815 mA·h/g; 在1C高倍率下, 电池首次放电比容量为710 mA·h/g, 经过500次循环后, 放电比容量仍能达到530 mA·h/g, 表明V₂O₃空心球的加入能够有效提高锂硫电池的循环性能.     

锂硫电池中的石墨烯掺杂

锂硫电池是以锂为负极,单质硫为正极的二次电池,具有高达1675 mA·h/g的比容量及2600 W·h/kg的比能量密度。理论上讲,相较于现有的锂离子电池,锂硫电池可使容量扩展5倍,这使其成为最有前景的锂离子电池。由于硫正极的绝缘性以及充放电过程中活性物质易溶于电解液,导致其可实现的能量密度远低于理论值。异原子掺杂石墨烯因具有优异的导电性,且对多硫化锂（LiPS）具有强的吸附作用而被广泛应用于锂硫电池,有效缓解了"穿梭效应",提高了电池的循环稳定性。本文主要从单原子掺杂、双原子掺杂两方面综述了异原子（如N,P,S,B）掺杂石墨烯在锂硫电池领域的研究现状,详细分析了其应用于锂硫电池的作用机理,并从掺杂量、掺杂形式、掺杂位置等方面对电池性能的提升进行了梳理和展望。     

高性能锂硫电池材料研究进展

锂-硫氧化还原对的比能量为2 600Wh/Kg,几乎是所有的二次电池氧化还原对中最高的,当锂-硫电池放电产物为Li2S时,电池的比容量可达到1 675mAh/g.近年来,人们在提高锂硫电池的循环可逆性和硫的利用率方面开展了大量的研究工作.本文结合本实验室的工作综述了锂硫二次电池的最新研究进展,对电池的正极、黏结剂、电解...     

锂硫电池硫碳复合正极材料研究现状及展望

二次锂硫电池被视为最具有发展潜力的下一代高能量密度二次电池之一. 但由于正极硫的电导率低（5×10^-30 S·cm^-1）,且在放电过程中产生的中间体多硫化物易溶于有机电解液,致使锂硫电池活性物质利用率降低,溶解后的多硫化物还会迁移到负极,被还原成不溶物Li2S2/Li2S而沉积于负极锂,使电极结构遭受破坏,造成电池容量大幅衰减,循环性能差,从而限制了进一步的开发应用. 研究表明,以碳作为导电骨架的硫碳复合正极材料能在不同程度上解决上述问题,从而有效提高了锂硫电池的放电容量和循环性能. 本文综述了近年来国内外报道的各种锂硫电池正极材料的研究进展,结合作者课题组的研究,重点探讨了硫碳复合正极材料,并对其今后的发展趋势进行了展望.     

高比能锂-硫电池研究进展

随着全球经济快速发展对高效绿色能源需求的不断增长,锂-硫电池因具有较高的能量密度,成为了下一代高能量密度二次电池研发的重点.然而,锂-硫电池面临的循环寿命短、库仑效率低、安全性能差、较高自放电等问题,使其目前还很难实现商品化.锂-硫电池存在的这些问题主要与正极活性硫材料的高绝缘性、放电过程中产生的多硫化物溶解于电解液、硫正极在充放电过程中的体积膨胀与收缩、以及锂负极支晶化等有关.通过从锂-硫电池硫复合正极、电解液、黏结剂和负极等4个方面综述了高比能锂-硫电池的最新研究进展,其中重点介绍了硫正极复合材料的进展情况.     

锂硫电池正极材料研究进展

电动汽车行业的迅速发展,逐步提高了对二次电池容量的要求,因此急需发展新型高容量锂电池。锂硫电池具有高理论比容量(1675mAh/g)和高理论比能量(2600Wh/kg),使其能够实现锂离子电池3~5倍的能量密度。但是,正极长链多硫化物溶解引起的容量衰减快、循环寿命短等因素限制了锂硫电池的实用化进程。本文针对正极聚硫锂溶解问题,从正极材料表面包覆、表面吸附、表面催化的角度对近年来提高锂硫电池循环性能的正极材料研究思路和研究进展进行综述,最后对提高锂硫电池性能的发展趋势提出展望。     

高容量硫/碳复合正极材料

以锂为负极、硫为正极的锂/硫二次电池,由于其较高的理论能量密度(2 600Wh/kg),而成为最具发展潜力的新型高能化学电源体系.但是,硫正极材料存在的活性物质利用率偏低和循环性能较差等缺点制约了锂/硫电池的快速发展.本文主要综述了基于多孔碳材料负载硫来构筑硫/碳复合材料,进而改善硫电极材料电化学性能的研究进展,多孔碳...     

锂-硫二次电池界面反应的特殊性与对策分析

锂-硫电池是在现有锂离子电池基础上最可能实现储能密度大幅提升的实用二次电池体系. 然而,这一电池体系的电化学利用率与循环稳定性仍然难以满足应用要求. 造成锂-硫电池性能不稳定的原因在于硫正极和锂负极的材料结构和反应环境始终处于变化之中,如在充放电过程中,硫-碳反应界面的电化学阻塞、中间产物的溶解流失、正负极之间的穿梭效应等副反应导致正极与负极均难形成稳定的电化学反应界面。针对这些特殊问题,本文简要分析了影响能量利用率和循环稳定性的化学与电化学机制,并提出了构建稳定锂负极与高效硫正极的若干可行性技术.     

Mitigating side reaction for high capacity retention in lithium-sulfur batteries

Li–S batteries have shown great potential as secondary energy batteries. However, the side reaction between Li anodes and polysulfides seriously limited their practical application. Herein, the artificial protective film, which is consisted of Li-Nafion and TiO₂, was designed and successfully prepared to achieve a corrosion-resistant Li anode in Li-S battery. In the composite protective film, the Li-Nafion could efficiently prevent the contact between Li anodes and polysulfides, and t...     

锂硫电池及关键材料研究进展

锂硫电池因具有远高于传统锂离子电池的理论比容量和质量能量密度,而受到人们的广泛关注,近年来一直是高能锂金属电池领域的研究热点之一. 然而这一体系的一些固有特性问题依然没有得到解决,无法实现稳定理论容量输出,严重阻碍了锂硫电池的实际应用. 其中,比较突出的问题是电池充放电过程中生成可溶性中间产物-多硫化物-对硫基正极、锂基负极和电解液等电池关键组成部分具有深刻的影响. 本综述从多硫化物的热力学和动力学等性质入手,详细介绍了锂硫电池中关键材料的功能化设计和优化策略,并对未来的发展做出展望.     

Low-temperature Li-S batteries enabled by all amorphous conversion process of organosulfur cathode

The high degree of crystallinity of discharging in termediates of Li-S batteries(Li₂S₂/Li₂S)causes a severe capacity attenuation at low temperatures.Herein,a sulfur-rich polymer is fabricated,which enables all the discharging in termediates to exist in an amorphous state without long-range order,promoti ng the substantial conversion of discharging intermediates and enhancing Li-S batteries'performance at low temperatures greatly.This cathode material exhibits excellent performance both at room and low temperatures.Even under an extremely low temperature(-40℃),the discharge capacity can remain 67% of that at room temperature.Besides,in-situ UV/Vis spectroscopy and density functional theory calculations reveal that this organosulfur cathode undergoes a new mechanism during discharge.Li₂S₆ and Li₂S₃ are the primary discharging intermediates that are quite different from conventional Li-S batteries.These results provide a new directi on for a broader range of applications of Li-S batteries.     

锂硫电池复合正极研究进展

锂硫电池因其超高的理论能量密度被视为极具前景的下一代电化学储能体系,其中高比容量的硫正极提供了锂硫电池的能量密度优势并直接决定了电池的实际性能。经过数十年的发展,最具前景的硫正极体系分别是硫碳复合（S/C）正极和硫化聚丙烯腈（SPAN）正极。本文系统综述了S/C正极和SPAN正极的最新研究进展。首先,简要介绍了两种正极的工作原理并进行了比较。S/C正极发生固-液-固多相转化反应,充放电表现为双平台特征。与之相比,SPAN正极发生固-固反应,充放电曲线为单平台。然后,对两种正极所面临的挑战和目前报道的优化策略进行了系统的分析与讨论。对于S/C正极,主要调控策略包括电极结构修饰、电催化剂设计与辅助氧化还原介体调控;对于SPAN正极,主要调控策略包括电极结构设计、电极形貌调控、杂原子掺杂和外源性氧化还原介体调控。最后,在电池尺度上对S/C正极和SPAN正极进行了综合比较,并对基于S/C正极和SPAN正极的锂硫电池在未来所面对的机遇与挑战进行了展望。     

Non-trivial Contribution of Carbon Hybridization in Carbon-based Substrates to Electrocatalytic Activities in Li-S Batteries

Appling an electrochemical catalyst is an efficient strategy for inhibiting the shuttle effect and enhancing the S utilization of Li-S batteries. Carbon-based materials are the most common conductive agents and catalyst supports used in Li-S batteries, but the correlation between the diversity of hybridizations and sulfur reduction reaction (SRR) catalytic activity remains unclear. Here, by establishing two forms of carbon models, i.e., graphitic carbon (GC) and amorphous carbon (AC), we observe that the nitrogen atom doped in the GC possesses a higher local charge density and a lower Gibbs free energy towards the formation of polysulfides than in the AC. And the GC-based electrode consistently inherits considerably enhanced SRR kinetics and superior cycling stability and rate capability in Li-S batteries. Therefore, the function of carbon in Li-S batteries is not only limited as conductive support but also plays an unignorable contribution to the electrocatalytic activities of SRR.     

Phosphorene: a Potential 2D Material for Highly Efficient Polysulfide Trapping and Conversion

Effectively trapping lithium polysulfide species and accelerating the reaction conversion kinetics are the main strategies to improve the performance of lithium-sulfur(Li-S) batteries. Since the researchers found in 2014 that two-dimensional(2D) phosphorene nanosheets could be exfoliated from the bulk black phosphorus, numerous researches have been devoted to exploring the phosphorene with unique properties for the application in Li-S batteries. In this review, we summarize the recent theoretical and experimental progress of phosphorene for Li-S batteries. Besides, we also introduce the relationship between the interfacial interaction on phosphorene and the performance enhancement of Li-S batteries. Furthermore, future challenges and remaining opportunities for phosphorene in Li-S batteries are finally discussed.     

TiN nanocrystal anchored on N-doped graphene as effective sulfur hosts for high-performance lithium-sulfur batteries

Lithium-sulfur(Li-S)batteries have become prospective candidates for next-generation energy storage owing to the high energy density and low cost.However,the sluggish kinetics of the electrochemical reaction and shuttle effect result in a rapid capacity decay.Herein,a titanium nitride nanocrystal/Ndoped graphene(TiN@NG)composite is developed to host elemental sulfur.The TiN nanoparticles decorated on graphene sheets attract Li polysulfides(LiPSx)and catalyze the electrochemical reduction and oxidation of LiPSx in the discharge and charge processes,respectively.These two effects effectively restrain the dissolution of the LiPSx and accelerate the electrochemical reactions,thereby,alleviating the shuttle effect.As a result,the cathode composed of TiN@NG/S delivers a remarkable reversible capacity(1390 mA h g^-1 at 0.1 C)and excellent cycling performance(730 mA h g^-1 after 300 cycles).We believe that this work can bring some inspiration for designing high-performance Li-S batteries.     

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。     

In Operando X-ray diffraction and transmission X-ray microscopy of lithium sulfur batteries

Rechargeable lithium-sulfur (Li-S) batteries hold great potential for high-performance energy storage systems because they have a high theoretical specific energy, low cost, and are eco-friendly. However, the structural and morphological changes during electrochemical reactions are still not well understood. In this Article, these changes in Li-S batteries are studied in operando by X-ray diffraction and transmission X-ray microscopy. We show recrystallization of sulfur by the end of the charge cycle is dependent on the preparation technique of the sulfur cathode. On the other hand, it was found that crystalline Li(2)S does not form at the end of discharge for all sulfur cathodes studied. Furthermore, during cycling the bulk of soluble polysulfides remains trapped within the cathode matrix. Our results differ from previous ex situ results. This highlights the importance of in operando studies and suggests possible strategies to improve cycle life.