Stabilizing Lithium into Cross‐Stacked Nanotube Sheets with an Ultra‐High Specific Capacity for Lithium Oxygen Batteries

Abstract

Although lithium-oxygen batteries possess ah igh theoretical energy density and are considered as promising candidates for next-generation power systems,t he enhancement of safety and cycling efficiency of the lithium anodes while maintaining the high energy storage capability remains difficult. Here,w eo vercome this challenge by cross-stacking aligned carbon nanotubes into porous networks for ultrahighcapacity lithium anodes to achieve high-performance lithiumoxygen batteries.T he novel anode shows ar eversible specific capacity of 3656 mAh g À1 ,approaching the theoretical capacity of 3861 mAh g À1 of pure lithium. When this anode is employed in lithium-oxygen full batteries,t he cycling stability is significantly enhanced, owingt ot he dendrite-free morphology and stabilized solid-electrolyte interface.This work presents anew pathway to high performance lithium-oxygen batteries towards practical applications by designing cross-stacked and aligned structures for one-dimensional conducting nanomaterials.

A Sodiophilic Interphase‐Mediated, Dendrite‐Free Anode with Ultrahigh Specific Capacity for Sodium‐Metal Batteries

“…For the control experiments, the CE of Na@ p ‐CNT (pristine CNT film) delivered a rather limited stability (Figure b; Supporting Information, Figure S18) and it was even harder for Na@Cu to stably cycle (Supporting Information, Figure S19). The deteriorated cycle performance of Na@ p ‐CNT and Na@Cu could be blamed on the heterogeneously distributed active sites on electrode surfaces, which led to the initial uneven Na nucleation, the latter formation of Na dendrites and eventually the poor cycling properties . Impressively, the study on higher areal capacity and current density (10 mAh cm −2 , 5 mA cm −2 ) at realistic application level showed equally outperformed cycling performance of Na@ O f ‐CNT, that is, a stable CE over 99.5 % for at least 680 cycles (or 2700 h; Figure c,d; Supporting Information, Figures S20, S21), further demonstrating the potential for practical high‐energy rechargeable SMBs.…”

“…As viewed from electrochemical impedance spectroscopy (EIS) analysis, the interfacial impedance of the Na@ O f ‐CNT nearly kept unchanged before and after cycling (Figure f). In contrast, the Na@ p ‐CNT and Na@Cu demonstrated drastically increased interfacial impedance attributed to the contaminated SEI and constantly generated dead Na during cycling . Upon continuous cycling under increasing current densities, the interfacial stability of Na@ O f ‐CNT could be well‐maintained, suggesting a stable surface electrochemistry for Na accommodation (Figure g).…”

A Sodiophilic Interphase‐Mediated, Dendrite‐Free Anode with Ultrahigh Specific Capacity for Sodium‐Metal Batteries

“…Notably,a fter 200 cycles of plating/stripping (5 mA cm À2 , 10 mAh cm À2 ), the porous structure of O f -CNT could be well retained when Na was eventually stripped (Figure 2j,k; Supporting Information, Figure S13), and the thickness nearly restored to its original state (Figure 2l;S upporting Information, Figure S14), suggesting the desirable reversibility of O f -CNT.Asastark contrast, dendritic Na shot out on the routine planar Cu foil substrate after several cycles of Na plating/ stripping (Supporting Information, Figure S15). [28] Impressively,the study on higher areal capacity and current density (10 mAh cm À2 ,5mA cm À2 )a tr ealistic application level showed equally outperformed cycling performance of Na@O f -CNT,that is,astable CE over 99.5 %for at least 680 cycles (or 2700 h; Figure 3c,d;S upporting Information, Figures S20, S21), further demonstrating the potential for practical high-energy rechargeable SMBs. Activation process was performed before Na deposition to remove surfacial impurities and form initial SEI layer (details in the Supporting Information, Note S3, Figures S16 and S17), which could reduce the electrolyte consumption during cycling.…”

“…Studies at higher current densities (for example,5mA cm À2 )also showed the superior interfacial stability of Na@O f -CNT (Supporting Information, Figure S23). [14,28] Upon continuous cycling under increasing current densities,t he interfacial stability of Na@O f -CNT could be well-maintained, suggesting astable surface electrochemistry for Na accommodation (Figure 3g). [29][30][31] On the contrary,N a@p-CNT and Na@Cu demonstrated intensive overpotential bumps (inset, Figure 3e;S upporting Information, Figure S24) due to the spatial variation in localized reaction kinetics on the electrode surface.A sv iewed from electrochemical impedance spectroscopy (EIS) analysis,t he interfacial impedance of the Na@O f -CNT nearly kept unchanged before and after cycling (Figure 3f).…”

Stable Li‐Metal Deposition via a 3D Nanodiamond Matrix with Ultrahigh Young's Modulus

“…A superior 3D host must satisfy the following important criteria: (1) sufficient (electro)chemical stability against Li‐metal, (2) superb mechanical property to restrain (or planish) the uneven Li deposition and to maintain the 3D structure, (3) a lightweight host that can maximize the specific capacity of the composite anode, (4) appropriate surface area to find the trade‐off between the decreased local current density and the increased side reactions; usually electrolyte additives are necessary; and (5) sufficient electrical resistivity to avoid Li‐metal nucleation on the top surface of the 3D host…”