Integrating Dually Encapsulated Si Architecture and Dense Structural Engineering for Ultrahigh Volumetric and Areal Capacity of Lithium Storage

Abstract

High-theoretical-capacity silicon anodes hold promise in lithium-ion batteries (LIBs). Nevertheless, their huge volume expansion (∼300%) and poor conductivity show the need for the simultaneous introduction of low-density conductive carbon and nanosized Si to conquer the above issues, yet they result in low volumetric performance. Herein, we develop an integration strategy of a dually encapsulated Si structure and dense structural engineering to fabricate a threedimensional (3D) highly dense Ti 3 C 2 T x MXene and graphene dual-encapsulated Si monolith architecture (HD-Si@Ti 3 C 2 T x @ G). Because of its high density (1.6 g cm −3 ), high conductivity (151 S m −1 ), and 3D dense dual-encapsulated Si architecture, the resultant HD-Si@Ti 3 C 2 T x @G monolith anode displays an ultrahigh volumetric capacity of 5206 mAh cm −3 (gravimetric capacity: 2892 mAh g −1 ) at 0.1 A g −1 and a superior long lifespan of 800 cycles at 1.0 A g −1 . Notably, the thick and dense monolithic anode presents a large areal capacity of 17.9 mAh cm −2 . In-situ TEM and ex-situ SEM techniques, and systematic kinetics and structural stability analysis during cycling demonstrate that such superior volumetric and areal performances stem from its dual-encapsulated Si architecture by the 3D conductive and elastic networks of MXene and graphene, which can provide fast electron and ion transfer, effective volume buffer, and good electrolyte permeability even with a thick electrode, whereas the dense structure results in a large volumetric performance. This work offers a simple and feasible strategy to greatly improve the volumetric and areal capacity of alloy-based anodes for large-scale applications via integrating a dual-encapsulated strategy and dense-structure engineering.

Dual Confinement of Si Nanoparticles in a MXene/ZIF-8-Derived Carbon Framework for Lithium-Ion Batteries

“…25,26 The selected area electron diffraction (SAED) image of Si/MXene@C further demonstrates distinct dispersive diffraction rings (Figure 2h), which were assigned to the (111), (220), and (311) crystal planes of Si, respectively. 27 Figure 2i shows the STEM image of Si/ MXene@C with corresponding element distribution mappings, where Ti, C, Si, and O elements depicted similar profiles in comparison with the STEM image, confirming the uniform distribution of Si nanoparticles within the MXene@C framework.…”

“…Besides, massive pores were detected on the surface of Si/MXene@C, which could be attributed to the sublimation of Zn nanoparticles in the ZIF-8-derived carbon/Zn hybrid at high temperatures. , The porous carbon layer can not only facilitate the ion diffusion in the composite but also coordinate with the MXene substrate to alleviate the volume expansion of Si during lithiation, thus resulting in excellent cycling stability. The high-resolution TEM image of Si/MXene@C reveals distinct lattice fringes with lattice spacings of 0.315 and 0.342 nm, corresponding to the (111) plane of Si and the (002) plane of carbon, respectively. , The selected area electron diffraction (SAED) image of Si/MXene@C further demonstrates distinct dispersive diffraction rings (Figure h), which were assigned to the (111), (220), and (311) crystal planes of Si, respectively Figure i shows the STEM image of Si/MXene@C with corresponding element distribution mappings, where Ti, C, Si, and O elements depicted similar profiles in comparison with the STEM image, confirming the uniform distribution of Si nanoparticles within the MXene@C framework.…”

Constructing a Yolk–Shell Structure SiOx/C@C Composite for Long-Life Lithium-Ion Batteries

“…14,15 In order to overcome the above problems and effectively boost the electrochemical performance of silicon-based electrodes, researchers have paid lots of effort. A series of modification methods has been developed, including nanocrystallization, 16,17 surface coating, 18,19 and structure design, 20,21 to heighten the conductivity of silicon-based anodes. These methods can effectively suppress their volume expansion and improve the structural stability during galvanostatic discharge/charge processes and significantly enhance the overall electrochemical performance.…”

LiI/Cu Mixed Conductive Interface via the Mechanical Rolling Approach for Stable Lithium Anodes in the Carbonate Electrolyte

“…The fast-growing demands for electric vehicles and high-end communication terminals have stimulated the development of storage devices with higher gravimetric and volumetric energy density. 1,2 As an ultimate anode material for the lithium ion batteries (LIBs) with superior energy density, Li metal has been intensively studied recently because of the low mass density, ultrahigh theoretical specific capacity of 3860 mAh g −1 , as well as the most negative reduction potential (−3.04 V vs standard hydrogen electrode). 3−5 Unfortunately, the short lifespan, unsatisfactory rate performance, and safety hazards of Li metal anode have seriously hindered the practical application in Li metal batteries (LMBs).…”

“…The fast-growing demands for electric vehicles and high-end communication terminals have stimulated the development of storage devices with higher gravimetric and volumetric energy density. , As an ultimate anode material for the lithium ion batteries (LIBs) with superior energy density, Li metal has been intensively studied recently because of the low mass density, ultrahigh theoretical specific capacity of 3860 mAh g –1 , as well as the most negative reduction potential (−3.04 V vs standard hydrogen electrode). − Unfortunately, the short lifespan, unsatisfactory rate performance, and safety hazards of Li metal anode have seriously hindered the practical application in Li metal batteries (LMBs). − Because of the high reaction activity, Li metal will react with the liquid electrolyte and a solid electrolyte interface (SEI) is spontaneously formed, which functions as a passivation layer to inhibit the further side reactions. , Nevertheless, the in situ generated SEI layer shows an inhomogeneous structure in both component and thickness, which results in uneven Li + flux and current flow at the Li/electrolyte interface followed by inhomogeneous Li deposition. Besides, the native SEI has poor flexibility and will break easily under the huge volume changes with exposing fresh Li to the organic electrolyte during the plating/stripping processes. − The parasitic reaction at the fresh Li/electrolyte interface promotes the persistent consumption of Li and electrolyte and the generation of Li dendrite, leading to poor Coulombic efficiency (CE) and even safety concerns of LMBs. , Besides, the sluggish Li + diffusion at the Li/electrolyte limits the rate capability of LMBs.…”