Two-Dimensional Graphitic Carbon-Nitride(g-C_(3)N_(4))-Coated LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)Cathodes for High-Energy-Density and Long-Life Lithium Batteries

High-capacity nickel-rich layered oxides are promising cathode materials for high-energy-density lithium batteries.However,the poor structural stability and severe side reactions at the electrode/electrolyte interface result in unsatisfactory cycle performance.Herein,the thin layer of two-dimensional(2D)graphitic carbon-nitride(g-C_(3)N_(4))is uniformly coated on the LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(denoted as NCM811@CN)using a facile chemical vaporization-assisted synthesis method.As an ideal protective layer,the g-C_(3)N_(4)layer effectively avoids direct contact between the NCM811 cathode and the electrolyte,preventing harmful side reactions and inhibiting secondary crystal cracking.Moreover,the unique nanopore structure and abundant nitrogen vacancy edges in g-C_(3)N_(4)facilitate the adsorption and diffusion of lithium ions,which enhances the lithium deintercalation/intercalation kinetics of the NCM811 cathode.As a result,the NCM811@CN-3wt%cathode exhibits 161.3 mAh g^(−1)and capacity retention of 84.6%at 0.5 C and 55°C after 400 cycles and 95.7 mAh g^(−1)at 10 C,which is greatly superior to the uncoated NCM811(i.e.129.3 mAh g^(−1)and capacity retention of 67.4%at 0.5 C and 55°C after 220 cycles and 28.8 mAh g^(−1)at 10 C).The improved cycle performance of the NCM811@CN-3wt%cathode is also applicable to solid–liquid-hybrid cells composed of PVDF:LLZTO electrolyte membranes,which show 163.8 mAh g^(−1)and the capacity retention of 88.1%at 0.1 C and 30°C after 200 cycles and 95.3 mAh g^(−1)at 1 C.

Ultrathin NiO/Ni_(3)S_(2)Heterostructure as Electrocatalyst for Accelerated Polysulfide Conversion in Lithium-Sulfur Batteries

The practical application of Lithium-Sulfur batteries largely depends on highly efficient utilization and conversion of sulfur under the realistic condition of high-sulfur content and low electrolyte/sulfur ratio.Rational design of heterostructure electrocatalysts with abundant active sites and strong interfacial electronic interactions is a promising but still challenging strategy for preventing shuttling of polysulfides in lithium-sulfur batteries.Herein,ultrathin nonlayered NiO/Ni_(3)S_(2)heterostructure nanosheets are developed through topochemical transformation of layered Ni(OH)_(2)templates to improve the utilization of sulfur and facilitate stable cycling of batteries.As a multifunction catalyst,NiO/Ni_(3)S_(2)not only enhances the adsorption of polysulfides and shorten the transport path of Li ions and electrons but also promotes the Li_(2)S formation and transformation,which are verified by both in-situ Raman spectroscopy and electrochemical investigations.Thus,the cell with NiO/Ni_(3)S_(2)as electrocatalyst delivers an area capacity of 4.8 mAh cm^(-2)under the high sulfur loading(6 mg cm^(-2))and low electrolyte/sulfur ratio(4.3 pL mg^(-1)).The strategy can be extended to 2D Ni foil,demonstrating its prospects in the construction of electrodes with high gravimetric/volumetric energy densities.The designed electrocatalyst of ultrathin nonlayered heterostructure will shed light on achieving high energy density lithium-sulfur batteries.

二维材料范德华间隙的利用

二维材料因为其优异且可调的各种物理化学性质自被发现以来就引起了科研工作者的极大关注。其电学、光学、量子、催化等方面的一些独特性质使其迅速成为一类极其重要的材料体系。二维材料层间弱结合的性质为利用范德华间隙来调控体系的电子结构从而进一步优化材料性能创造了条件。客体原子的引入可以显著改变原有材料的层间间距,改变层间的耦合强度。客体与宿主原子的相互作用也可能改变原始材料的电子结构,从而影响材料的多方面性能,甚至带来新的性质。以锂离子电池为代表的层间存储也是二维范德华间隙在能源存储方面的重要应用,一直受到许多科研工作者的关注。在本综述中,我们从利用插层法改变层间距从而改变层间耦合,引入客体物质与宿主原子相互作用从而改变原材料的物理化学性质或引入新性质和层间储能四个方面系统化阐述了二维材料范德华间隙的各种调控方法及其对合成材料的物理、化学性能的巨大影响,并展望了二维范德华间隙进一步开发利用的方向。

Enhanced mass transfer in three-dimensional single-atom nickel catalyst with open-pore structure for highly efficient CO_(2) electrolysis

Design of efficient catalysts for electrochemical reduction of carbon dioxide (CO_(2)) with high selectivity and activity is of great challenge, but significant for managing the global carbon balance. Herein, a series of three-dimensional (3D) single-atom metals anchored on graphene networks (3D SAM-G) with open-pore structure were successfully mass-produced via a facile in-situ calcination technique assisted by NaCl template. As-obtained 3D SANi-G electrode delivers excellent CO Faradaic efficiency (FE) of >96% in the potential range of −0.6 to −0.9 V versus reversible hydrogen electrode (RHE) and a high current density of 66.27 mA cm^(−2) at −1.0 V versus RHE, outperforming most of the previously reported catalysts tested in H-type cells. Simulations indicate that enhanced mass transport within the 3D open-pore structure effectively increases the catalytically active sites, which in turn leads to simultaneous enhancement on selectivity and activity of 3D SANi-G toward CO_(2) electroreduction. The cost-effective synthesis approach together with the microstructure design concept inspires new insights for the development of efficient electrocatalysts.

Boron-doping induced lithophilic transition of graphene for dendrite-free lithium growth

Li metal,possessing advantages of high theoretical specific capacity and low electrochemical potential,is regarded as the most promising anode material for next-generation batteries.However,despite decades of intensive research,its practical application is still hindered by safety hazard and low Coulombic efficiency,which is primarily caused by dendritic Li deposition.To address this issue,restraining dendrite growth at the nucleation stage is deemed as the most effective method.By utilizing the difference of electronegativity between boron atoms and carbon atoms,carbon atoms around boron atoms in boron-doped graphene(BG)turn into lithiophilic sites,which can enhance the adsorption capacity to Li^(+)at the nucleation stage.Consequently,an ultralow overpotential of 10 mV at a current density of 0.5 mA/cm^(2) and a high average Coulombic efficiency of 98.54%over more than 140 cycles with an areal capacity of 2 mAh/cm^(2) at a current density of 1 m A/cm^(2) were achieved.BG-Li|LiFePO_(4) full cells delivered a long lifespan of480 cycles at 0.5 C and excellent rate capability.This work provides a novel method for rational design of dendrite-free Li metal batteries by regulating nucleation process.

Design of Solid Electrolytes with Fast Ion Transport:Computation-Driven and Practical Approaches

For next-generation all-solid-state metal batteries,the computation can lead to the discovery of new solid electrolytes with increased ionic conductivity and excellent safety.Based on computational predictions,a new proposed solid electrolyte with a flat energy landscape and fast ion migration is synthesized using traditional synthesis methods.Despite the promise of the predicted solid electrolyte candidates,conventional synthetic methods are frequently hampered by extensive optimization procedures and overpriced raw materials.It is impossible to rationally develop novel superionic conductors without a comprehensive understanding of ion migration mechanisms.In this review,we cover ion migration mechanisms and all emerging computational approaches that can be applied to explore ion conduction in inorganic materials.The general illustrations of sulfide and oxide electrolyte structures as well as their fundamental features,including ion migration paths,dimensionalities,defects,and ion occupancies,are systematically discussed.The major challenges to designing the solid electrolyte and their solving strategies are highlighted,such as lattice softness,polarizability,and structural disorder.In addition to an overview of recent findings,we propose a computational and experimental approach for designing high-performance solid electrolytes.This review article will contribute to a practical understanding of ion conduction,designing,rapid optimization,and screening of advanced solid electrolytes in order to eliminate liquid electrolytes.

Evaluation of solid electrolytes: Development of conventional and interdisciplinary approaches

Solid-state lithium batteries(SSLBs)have received considerable attention due to their advantages in thermal stability,energy density,and safety.Solid electrolyte(SE)is a key component in developing high-performance SSLBs.An in-depth understanding of the intrinsic bulk and interfacial properties is imperative to achieve SEs with competitive performance.This review first introduces the traditional electrochemical approaches to evaluating the fundamental parameters of SEs,including the ionic and electronic conductivities,activation barrier,electrochemical stability,and diffusion coefficient.After that,the characterization techniques to evaluate the structural and chemical stability of SEs are reviewed.Further,emerging interdisciplinary visualization techniques for SEs and interfaces are highlighted,including synchrotron X-ray tomography,ultrasonic scanning imaging,time-of-flight secondary-ion mass spectrometry,and three-dimensional stress mapping,which improve the understanding of electrochemical performance and failure mechanisms.In addition,the application of machine learning to accelerate the screening and development of novel SEs is introduced.This review article aims to provide an overview of advanced characterization from a broad physical chemistry view,inspiring innovative and interdisciplinary studies in solid-state batteries.