钯催化剂对锂空气电池氧析出和氧还原反应的催化机理的研究

锂空气电池以其超高的能量密度而备受关注, 然而充、放电过电位高等问题严重限制了其实际应用。金属钯作为催化剂可而降低锂空气电池的充、放电过电位, 但其充、放电反应催化机制尚不完善。本研究运用第一原理计算方法, 建立了钯/氧气/过氧化锂(Pd/O₂/Li₂O₂)的三相界面催化模型, 从微观角度揭示钯催化剂在锂空气电池充、放电反应中的催化机制。研究表明, Pd/O基底通过促进Li₂O₂在界面处的电荷转移提高自身对LiO₂吸附作用, 从而加速放电产物在电极表面的形成, 有效降低了充电过电位0.43 V。     

Facile Formation of a Solid Electrolyte Interface as a Smart Blocking Layer for High‐Stability Sulfur Cathode

The practical application of lithium–sulfur batteries (LSBs) is hindered by their poor cycle life, which stems mainly from the “redox shuttle reactions” of dissolved polysulfides. To develop a high‐performance cathode for LSBs, encapsulation of polysulfides with a blocking layer is potentially straightforward. Herein, a novel strategy is reported encapsulate sulfur and the electrolyte together in porous carbon spheres by using a solid electrolyte interface (SEI) that can selectively sieve Li⁺ ions while efficiently avoiding polysulfide accumulation and suppressing undesired polysulfide migration. This strategy is simple, straightforward, and effective. The carbon/sulfur cathode only needs to be cycled a few times within a voltage window of 0.3–1.0 V to form such a smart SEI, allowing the resulting cathode to exhibit superior stability extending 600 cycles. This strategy can be combined with other existing advanced sulfur cathode designs to improve the overall performance of LSBs.     

A Robust and Conductive Black Tin Oxide Nanostructure Makes Efficient Lithium‐Ion Batteries Possible

SnO₂‐based lithium‐ion batteries have low cost and high energy density, but their capacity fades rapidly during lithiation/delithiation due to phase aggregation and cracking. These problems can be mitigated by using highly conducting black SnO_2?x , which homogenizes the redox reactions and stabilizes fine, fracture‐resistant Sn precipitates in the Li₂O matrix. Such fine Sn precipitates and their ample contact with Li₂O proliferate the reversible Sn → Li _x Sn → Sn → SnO₂/SnO_2?x cycle during charging/discharging. SnO_2?x electrode has a reversible capacity of 1340 mAh g^?1 and retains 590 mAh g^?1 after 100 cycles. The addition of highly conductive, well‐dispersed reduced graphene oxide further stabilizes and improves its performance, allowing 950 mAh g^?1 remaining after 100 cycles at 0.2 A g^?1 with 700 mAh g^?1 at 2.0 A g^?1. Conductivity‐directed microstructure development may offer a new approach to form advanced electrodes.     

Reviving Lithium‐Metal Anodes for Next‐Generation High‐Energy Batteries

Lithium‐metal batteries (LMBs), as one of the most promising next‐generation high‐energy‐density storage devices, are able to meet the rigid demands of new industries. However, the direct utilization of metallic lithium can induce harsh safety issues, inferior rate and cycle performance, or anode pulverization inside the cells. These drawbacks severely hinder the commercialization of LMBs. Here, an up‐to‐date review of the behavior of lithium ions upon deposition/dissolution, and the failure mechanisms of lithium‐metal anodes is presented. It has been shown that the primary causes consist of the growth of lithium dendrites due to large polarization and a strong electric field at the vicinity of the anode, the hyperactivity of metallic lithium, and hostless infinite volume changes upon cycling. The recent advances in liquid organic electrolyte (LOE) systems through modulating the local current density, anion depletion, lithium flux, the anode–electrolyte interface, or the mechanical strength of the interlayers are highlighted. Concrete strategies including tailoring the anode structures, optimizing the electrolytes, building artificial anode–electrolyte interfaces, and functionalizing the protective interlayers are summarized in detail. Furthermore, the challenges remaining in LOE systems are outlined, and the future perspectives of introducing solid‐state electrolytes to radically address safety issues are presented.     

Critical Insight into the Relentless Progression Toward Graphene and Graphene‐Containing Materials for Lithium‐Ion Battery Anodes

Used as a bare active material or component in hybrids, graphene has been the subject of numerous studies in recent years. Indeed, from the first report that appeared in late July 2008, almost 1600 papers were published as of the end 2015 that investigated the properties of graphene as an anode material for lithium‐ion batteries. Although an impressive amount of data has been collected, a real advance in the field still seems to be missing. In this framework, attention is focused on the most prominent research efforts in this field with the aim of identifying the causes of such relentless progression through an insightful and critical evaluation of the lithium‐ion storage performances (i.e., 1^st cycle irreversible capacity, specific gravimetric and volumetric capacities, average delithiation voltage profile, rate capability and stability upon cycling). The “graphene fever” has certainly provided a number of fundamental studies unveiling the electrochemical properties of this “wonder” material. However, analysis of the published literature also highlights a loss of focus from the final application. Hype‐driven claims, not fully appropriate metrics, and negligence of key parameters are probably some of the factors still hindering the application of graphene in commercial batteries.     

Carbon‐Coated Na3.32Fe2.34(P2O7)2 Cathode Material for High‐Rate and Long‐Life Sodium‐Ion Batteries

Rechargeable sodium‐ion batteries are proposed as the most appropriate alternative to lithium batteries due to the fast consumption of the limited lithium resources. Due to their improved safety, polyanion framework compounds have recently gained attention as potential candidates. With the earth‐abundant element Fe being the redox center, the uniform carbon‐coated Na_3.32Fe_2.34(P₂O₇)₂/C composite represents a promising alternative for sodium‐ion batteries. The electrochemical results show that the as‐prepared Na_3.32Fe_2.34(P₂O₇)₂/C composite can deliver capacity of ≈100 mA h g^?1 at 0.1 C (1 C = 120 mA g^?1), with capacity retention of 92.3% at 0.5 C after 300 cycles. After adding fluoroethylene carbonate additive to the electrolyte, 89.6% of the initial capacity is maintained, even after 1100 cycles at 5 C. The electrochemical mechanism is systematically investigated via both in situ synchrotron X‐ray diffraction and density functional theory calculations. The results show that the sodiation and desodiation are single‐phase‐transition processes with two 1D sodium paths, which facilitates fast ionic diffusion. A small volume change, nearly 100% first‐cycle Coulombic efficiency, and a pseudocapacitance contribution are also demonstrated. This research indicates that this new compound could be a potential competitor for other iron‐based cathode electrodes for application in large‐scale Na rechargeable batteries.     

Liquid Quinones for Solvent‐Free Redox Flow Batteries

Liquid benzoquinone and naphthoquinone having diethylene glycol monomethyl ether groups are designed and synthesized as redox active materials that dissolve supporting electrolytes. The Li‐ion batteries based on the liquid quinones using LiBF₄/PC show good performance in terms of voltage, capacity, energy efficiency, and cyclability in both static and flow modes. A battery is constructed without using intentionally added organic solvent, and its high energy density (264 W h L^?1) demonstrates the potential of solvent‐free organic redox flow batteries using liquid active materials.