A Dendrite‐Free Lithium‐Metal Anode Enabled by Designed Ultrathin MgF₂ Nanosheets Encapsulated Inside Nitrogen‐Doped Graphene‐Like Hollow Nanospheres

Abstract

generated on the anode surface breaks fragilely, bringing about further electrolyte decomposition and causing low coulombic efficiency (CE) and rapid capacity fade. [4] For decades, extensive endeavors have been made to overcome these issues by developing functional electrolytes, [5][6][7] constructing artificial SEI films, [8][9][10][11] and engineering well-designed host materials. [12][13][14][15][16][17] Among various strategies, the host materials have gained considerable interest because they are effective in reducing the real current density and accommodating large volume changes during Li plating/stripping processes. For instance, Guo et al. [15,16] reported porous carbon nanofibers as fascinating 3D frameworks for stable LMA. Unfortunately, the poor affinity for Li + makes it difficult for the conventional hosts to regulate the Li + concentration near the electrode/electrolyte interface, leading to unsatisfactory cycle life and rate capability.Recently, hosts coupled with nitrogenor oxygen-containing polar functional groups, possessing high Li + anchoring ability, have become a new trend. [18][19][20][21][22] For example, Wang et al. [22] reported N-doped hollow porous carbon spheres (N-HPCSs) fabricated by a carbonization process of a nitrogen resorcinol-formaldehyde coating layer on a SiO 2 template. The N-HPCSs had good lithiophilicity and enabled preferential homogenous deposition of Li inside the spherical cavities owing to high N doping content and porosity. As a consequence, it exhibited a 98.6% CE for more than 270 cycles at 1 mAh cm −2 . When matched with the S cathode as full cells, N-HPCSs@Li displayed a reversible capacity of 907 mAh g −1 (capacity retention: 80.1%) after 400 cycles at 1 C. More recently, it has been found that Li metal can be preferentially deposited on nanoseeds (Au, Ag, Zn, and Mg) because of their appreciable solubility in Li, attaining ultralow or zero overpotential of nucleation. [23] Subsequently, these metals or metal-Li alloys were introduced into the cavities of hosts to further improve the electrochemical properties of LMA. [24][25][26][27] For example, Qiu et al. [27] reported a 3D Mg x Li y /LiF-Li-rGO composite fabricated by a combined process based on vacuum filtration and meltdiffusion. At a current density of 1 mA cm −2 , the symmetric cells with the anode exhibited a small stable hysteresis voltage Uncontrolled lithium dendrite growth and dramatic volume change during cycling have long been severely impeding the practical applications of Li metal as the ultimate anode. In this work, ultrathin MgF 2 nanosheets encapsulated inside nitrogen-doped graphene-like hollow nanospheres (MgF 2 NSs@NGHSs) are ingeniously fabricated to address these problems by a perfect combination of atomic layer deposition and chemical vapor deposition. The uniform and continuous Li-Mg solid-solution inner layer formed by the MgF 2 nanosheets can reduce the nucleation overpotential and induce selective deposition of Li into the cavities of the NGHSs. Furthermore, the Li deposition beh...

Recent advancements in 3D porous graphene-based electrode materials for electrochemical energy storage applications

“…The synthesis of graphene materials and graphene-based composites has been involved in considerable strategies for energybased applications. Owing to the large flat layered structure with strong sp 2 covalent bonds, high surface area, and excellent electron transport properties, graphene sheets are considered to be a promising electrode material for energy devices such as lithium batteries, supercapacitors, and many others [11,12]. Graphene has a high theoretical surface area value of 2630 m 2 g -1 [13], and it possesses unique physicochemical properties like superior electrical conductivity, excellent 3 chemical stability, and good thermal conductivity [14,15].…”

Lightweight and Flexible 3D ERGO@Cu/PA Mesh Current Collector of Li Metal Battery for Dendrite Suppression

“…Furthermore, the XPS results show that there are CO, C–O groups in the ERGO@Cu/PA mesh, with an obvious oxygen doping level. Mukherjee et al and Wang et al , systematically studied the role of structural defects and oxygen-containing groups in the graphene lattice in inducing Li deposition through theoretical calculation and experimental characterization. It is found that Li is preferentially adsorbed to these topological defects in a stable form and acts as a nucleation site for further deposition to induce uniform deposition of Li.…”

“…For the bottleneck of uncontrollable Li dendrite, several different strategies were used to suppress dendrite growth and enhance the cycling stability, modifying a strong artificial SEI film on the Li interface as a blocking layer for dendritic growth, − or homogenizing the electric field distributions on an anode interface during Li deposition through modification of the electrolyte or the introduction of additives, − as well as reducing the Li nucleation overpotential and homogenize Li deposition by employing lithiophilic materials. − Besides, the 3D Cu − current collector can inhibit the growth of Li dendrite and effectively alleviate the volume expansion through the combination with Li metal (electrodeposition, melting, and rolling), which improves the cycling stability of the Li metal battery, as well as decreases the excessive use of Li foil to a proper extent, reducing the production cost and security risks.…”

β‐Ketoenamine‐Linked Covalent Organic Framework with Co Intercalation: Improved Lithium‐Storage Properties and Mechanism for High‐Performance Lithium‐Organic Batteries

“…The morphology and the porous structure with pore size of COF can be adjusted by selecting the assembled monomers with desired length and geometry at the molecular level. Recently, many reports on the application of COF in photocatalysis, [16,17] CO 2 adsorption, [18] electrochemical energy storage [19][20][21][22][23][24][25] and other fields [26,27] have been reported. It is worth noting that the π-electron delocalization of π-orbital overlap and the maximum energy induced from the van der Waals interaction result in the high specific surface area and high porosity of COF materials, leading to more accessible active sites for energy-storage reactions.…”