Li4Mn5O12Cathode for Both 3 V and 4 V Lithium-ion Batteries

Spinel Li₄Mn₅O₁₂ has been of economical and academic interest as cathode material for 3 V lithium-ion batteries(LIBs) since the 1990s. Recent studies also demonstrate that the increase of upper cut-off voltage to 5.0 V can significantly promote the specific capacity and the average operating voltage thus enabling its possibility to be used in 4 V LIBs. It is cost-effective and environmentally benign, shows structural stability without suffering from Jahn-Teller distortion due to the tetravalent oxidation state of Mn ion. However, the undesirable decomposition reactions during high-temperature calcination result in the difficulty of fabricating stoichiometric Li₄Mn₅O₁₂ compounds. Meanwhile, the high capacity led by the enlarged voltage window is combined with fast capacity fading due to the poor reversibility of oxygen redox. In this review, the understanding of the relationship between structure and stochiometric chemistry of Li₄Mn₅O₁₂ is discussed and the ways to improving its electrochemical performance are summarized. Our focus is its recent developments of being used as high voltage cathode or "additive" for layered cathodes. At last, we also provide our perspectives on this material regarding to the target of enabling its application in 4 V LIBs.     

Graphene-Based Nanomaterials as the Cathode for Lithium-Sulfur Batteries

The global energy crisis and environmental problems are becoming increasingly serious. It is now urgent to vigorously develop an efficient energy storage system. Lithium-sulfur batteries (LSBs) are considered to be one of the most promising candidates for next-generation energy storage systems due to their high energy density. Sulfur is abundant on Earth, low-cost, and environmentally friendly, which is consistent with the characteristics of new clean energy. Although LSBs possess numerous advantages, they still suffer from numerous problems such as the dissolution and diffusion of sulfur intermediate products during the discharge process, the expansion of the electrode volume, and so on, which severely limit their further development. Graphene is a two-dimensional crystal material with a single atomic layer thickness and honeycomb bonding structure formed by sp² hybridization of carbon atoms. Since its discovery in 2004, graphene has attracted worldwide attention due to its excellent physical and chemical properties. Herein, this review summarizes the latest developments in graphene frameworks, heteroatom-modified graphene, and graphene composite frameworks in sulfur cathodes. Moreover, the challenges and future development of graphene-based sulfur cathodes are also discussed.     

Systematic Study of Quaternary Ammonium Cations for Bromine Sequestering Application in High Energy Density Electrolytes for Hydrogen Bromine Redox Flow Batteries

Bromine complexing agents (BCAs) are used to reduce the vapor pressure of bromine in the aqueous electrolytes of bromine flow batteries. BCAs bind hazardous, volatile bromine by forming a second, heavy liquid fused salt. The properties of BCAs in a strongly acidic bromine electrolyte are largely unexplored. A total of 38 different quaternary ammonium halides are investigated ex situ regarding their properties and applicability in bromine electrolytes as BCAs. The focus is on the development of safe and performant HBr/Br₂/H₂O electrolytes with a theoretical capacity of 180 Ah L⁻¹ for hydrogen bromine redox flow batteries (H₂/Br₂-RFB). Stable liquid fused salts, moderate bromine complexation, large conductivities and large redox potentials in the aqueous phase of the electrolytes are investigated in order to determine the most applicable BCA for this kind of electrolyte. A detailed study on the properties of BCA cations in these parameters is provided for the first time, as well as for electrolyte mixtures at different states of charge of the electrolyte. 1-ethylpyridin-1-ium bromide [C2Py]Br is selected from 38 BCAs based on its properties as a BCA that should be focused on for application in electrolytes for H₂/Br₂-RFB in the future.     

新型石墨化氮化碳/锡/氮掺杂碳复合物的制备及储钠性能

钠离子电池锡负极因具有较高的理论容量(847 mA·h/g)、 高电导率和合适的工作电位而备受关注. 但锡基负极材料在循环过程中会发生巨大的结构变化, 进而导致活性材料粉化失活和比容量的快速下降. 本文成功制备了基于石墨氮化碳(g-C₃N₄)、 聚多巴胺衍生的氮掺杂碳(NC)和Sn纳米颗粒的复合物(g-C₃N₄/Sn/NC), 其中Sn纳米颗粒包埋在石墨氮化碳和氮掺杂碳中. 在此多层分级结构中, g-C₃N₄和NC的引入可以显著加速电子/离子的传输及电池反应动力学, 从而有助于Sn和钠离子之间的合金化反应; 此外, 这种复合结构有助于保持电极材料的结构稳定性, 进而可以获得优异的储钠性能. 作为钠离子电池负极材料, g-C₃N₄/Sn/NC在0.5 A/g电流密度下经历100次循环, 可逆容量可以达到450.7 mA·h/g; 在1.0 A/g电流密度下, 比容量为388.3 mA·h/g; 此外, 在1.0 A/g电流密度下, 经过400次循环后其比容量依旧能达到363.3 mA·h/g.     

全固态锂金属电池表界面化学的研究进展

传统的锂金属电池存在电解液易泄漏、 易燃等安全隐患, 因此开发不燃性全固态电解质对于解决锂金属电池安全问题至关重要, 而如何有效降低固体电解质与电极之间的界面电阻是发展高性能全固态锂金属电池的关键. 针对如何优化全固态锂金属电池表界面的问题, 本文综述了全固态锂金属电池电极和电解质表面修饰的最新研究进展, 对提高界面接触和降低界面电阻的传统方法进行了探讨, 分析并点评了新型的表面修饰技术, 为进一步提高全固态锂金属电池的综合性能提供新思路. 最后, 对全固态锂金属电池的研究前景进行了展望.     

一步法高效制备纳米Si/C复合材料及其在高性能锂离子电池中的应用

开发了一种一步高效合成纳米硅/碳复合材料的新方法, 该方法通过球磨SiCl₄、 Mg₂Si和商业碳片, 使SiCl₄自下而上还原, 原位形成的纳米硅均匀生长在碳片上, 高效制备了纳米硅与碳片均匀复合物(Nano-Si/C). 该Nano-Si/C用作锂离子电池负极材料展现出高的可逆储锂容量(2450 mA·h/g)、 良好的倍率性能及优异的长循环稳定性, 在2 A/g电流密度下, 经过600次循环后, 容量仍然稳定在1400 mA·h/g. 其突出的电化学性能主要归因于小尺寸纳米硅与碳片均匀复合的纳米结构, 在循环嵌锂/脱锂过程中仍能保持结构和电化学性质的稳定性.     

可充电镁电池负极改性策略

可充电镁电池具有理论体积比容量大、 地壳丰度高、 成本低、 环境友好及更为安全等优点, 是未来高能量存储系统发展的重要方向之一. 在大多数传统电解液中, 镁金属负极表面形成的钝化膜会阻碍镁的可逆沉积溶解过程, 从而限制了可充电镁电池的商业化应用. 由于存在成本高、 合成步骤复杂、 离子电导率低及难以同时与正负极兼容等问题, 聚焦于解决镁负级钝化问题的电解液研究陷入瓶颈. 因此, 通过对镁电池负极进行修饰改性, 使其在传统电解液中实现可逆过程是一种具有发展前景的策略. 本文从合金负极及人工界面形成两方面总结了近年来用于可充电镁电池负极改性的策略, 并在分析对比的基础上提出了进一步发展的结论和展望.     

Overview of the Structure–Dynamics–Function Relationships in Borohydrides for Use as Solid-State Electrolytes in Battery Applications

The goal of this article is to highlight crucial breakthroughs in solid-state ionic conduction in borohydrides for battery applications. Borohydrides, M^z+B_xH_y, form in various molecular structures, for example, nido-M⁺BH₄; closo-M²⁺B₁₀H₁₀; closo-M²⁺B₁₂H₁₂; and planar-M⁶⁺B₆H₆ with M = cations such as Li⁺, K⁺, Na⁺, Ca²⁺, and Mg²⁺, which can participate in ionic conduction. This overview article will fully explore the phase space of boron–hydrogen chemistry in order to discuss parameters that optimize these materials as solid electrolytes for battery applications. Key properties for effective solid-state electrolytes, including ionic conduction, electrochemical window, high energy density, and resistance to dendrite formation, are also discussed. Because of their open structures (for closo-boranes) leading to rapid ionic conduction, and their ability to undergo phase transition between low conductivity and high conductivity phases, borohydrides deserve a focused discussion and further experimental efforts. One challenge that remains is the low electrochemical stability of borohydrides. This overview article highlights current knowledge and additionally recommends a path towards further computational and experimental research efforts.     

La(OH)3负载锌铝水滑石的制备及其应用在锌镍二次电池中的性能

采用共沉淀法将氢氧化镧(La(OH)₃)负载在锌铝水滑石(Zn-Al LDHs)的表面,扫描电镜(SEM)、X射线衍射(XRD)表明La(OH)₃成功负载在锌铝水滑石表面,并且负载后的锌铝水滑石仍然为六边形片状晶体,且粒径均匀、分散性好。La(OH)₃质量其具有较好的可逆性、更大的正腐蚀电位及较小的电池内阻。5%La(OH)₃@Zn-Al LDHs在经过80次循环后,其循环保持率为94.84%。     

铜卟啉金属有机框架材料用于高性能锂硫电池

利用卟啉配体与金属离子的配位特性,通过后修饰将铜离子与卟啉基金属有机框架材料(PCN-222)配位,得到铜卟啉金属有机框架材料(PCN-222-Cu),并首次用于锂硫电池。借助紫外可见光谱(UV-Vis)、粉末X射线衍射(PXRD)、N_2吸附-脱附测试、扫描电子显微镜(SEM)、循环伏安(CV)和恒电流充放电测试等表征手段对材料的晶相结构、形貌和电化学性能进行了系统的研究。其中UV-Vis结果表明,Cu~(2+)与卟啉环成功配位。电化学测试结果表明,负载硫的PCN-222-Cu(S-in-PCN-222-Cu)电极在1C的倍率下循环300周后可逆比容量为840 mAh·g~(-1)。当倍率提高到3C时,循环800周后的容量仍保持430 mAh·g~(-1),每周容量衰减率为0.042%。S-in-PCN-222-Cu电极的电化学性能远优于S-in-PCN-222,说明配体上的Cu~(2+)与卟啉环的协同作用能有效降低电化学极化,从而显著提升卟啉基金属有机框架材料用作硫载体的电化学性能和循环稳定性。