Volume 1, Issue 3, Pages 563-575 (November 2017) Free-Standing Hollow Carbon Fibers as High-Capacity Containers for Stable Lithium Metal Anodes  Lin Liu, Ya-Xia Yin, Jin-Yi Li, Nian-Wu Li, Xian-Xiang Zeng, Huan Ye, Yu-Guo Guo, Li-Jun Wan  Joule  Volume 1, Issue 3, Pages 563-575 (November 2017) DOI: 10.1016/j.joule.2017.06.004 Copyright © 2017 Elsevier Inc. Terms and Conditions

Joule 2017 1, 563-575DOI: (10.1016/j.joule.2017.06.004) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 1 Characterization of the 3D-HCFs (A) Photograph of the cotton, as-prepared 3D-HCFs, and the electrode slice. (B) SEM image of 3D-HCFs. Scale bar, 10 μm. Inset: the cross-sectional view SEM image of a single tubular fiber. Scale bar, 5 μm. (C) HRTEM image of the 3D-HCFs. Scale bar, 5 nm. Inset: SAED image. (D) XRD patterns of the 3D-HCFs. (E) Raman spectra of the 3D-HCFs. (F) Nitrogen adsorption-desorption isotherm. Inset: the corresponding pore size distribution of the 3D-HCFs. See also Figure S1. Joule 2017 1, 563-575DOI: (10.1016/j.joule.2017.06.004) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 2 Li Metal Deposition Behavior on Top View SEM Images For a Figure360 author presentation of Figure 2, see the figure legend at http://dx.doi.org/10.1016/j.joule.2017.06.004. (A) Schematic diagrams of Li deposition behavior. Blue, 3D-HCFs; orange, Li. (B–H) Morphology characterization of the Li metal anode during plating/stripping. Top view SEM images of (B) pristine 3D-HCFs without Li metal and after plating (C) 2 mA hr cm−2, (D) 4 mA hr cm−2, and (E) 6 mA hr cm−2 of Li metal into the 3D-HCFs; anodes after stripping (F) 2 mA hr cm−2, (G) 4 mA hr cm−2, and (H) 6 mA hr cm−2 (i.e., recharged to 1 V) from the Li anodes (6 mA hr cm−2) with the 3D-HCFs. (I) Top view SEM image of the Li anode with the 3D-HCFs after 20 cycles. (J) Cross-sectional SEM images of the Li with the 3D-HCFs. (K) The Li plating/stripping states (B–J) are indicated in the galvanostatic discharge/charge voltage profile at 1 mA cm−2. Scale bars, (B–J) 50 μm. See also Figure S2. Figure360: an author presentation of Figure 2 Joule 2017 1, 563-575DOI: (10.1016/j.joule.2017.06.004) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 3 Li Metal Deposition Behavior on Cross-sectional View SEM Images (A–F) Cross-sectional view SEM images of (A) the pristine 3D-HCFs and after plating (B) 1 mA hr cm−2, (C) 2 mA hr cm−2, (D) 3 mA hr cm−2, (E) 4 mA hr cm−2, (F) 6 mA hr cm−2 of Li into the 3D-HCFs. Scale bars, 5 μm. (G) Schematic diagrams of the change in the cross-section with the increase in lithium deposition areal capacities. Joule 2017 1, 563-575DOI: (10.1016/j.joule.2017.06.004) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 4 Electrochemical Performance: Coulombic Efficiency (A) Comparison of Coulombic efficiency of the 3D-HCF electrode (solid symbols) and the planar Cu electrode (hollow symbols) with areal capacity of 2 mA hr cm−2 at a current density of 0.5 mA cm−2 or 1 mA cm−2. (B) Comparison of Coulombic efficiency of the 3D-HCF electrode (solid symbols) and the planar Cu electrode (hollow symbols) with areal capacity of 4 mA hr cm−2 at a current density of 1 mA cm−2 and 2 mA cm−2. (C) Comparison of Coulombic efficiency of the 3D-HCF electrode (solid symbols) and the planar Cu electrode (hollow symbols) with areal capacity of 6 mA hr cm−2 at a current density of 1 mA cm−2. (D) Voltage profiles of the Li plating/stripping process with Li metal as the reference/counter electrode at 1 mA cm−2 for 6 mA hr cm−2. See also Figure S5. Joule 2017 1, 563-575DOI: (10.1016/j.joule.2017.06.004) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 5 Electrochemical Performance: Voltage Profiles of Li Metal Plating/Stripping in Symmetric Cells (A) Voltage profiles of Li metal plating/stripping in three styles of symmetric cells (Li foil, Cu@Li, and 3D-HCFs@Li cells) at 2 mA cm−2 for 1 mA hr cm−2. (B) The detailed voltage profiles from the 200th to the 220th cycle in (A). (C) The detailed voltage profiles from the 400th to the 420th cycle in (A). (D) Average voltage hysteresis of the lithium deposition/dissolution process in three styles of symmetric cells at 2 mA cm−2 for 1 mA hr cm−2. (E) Nyquist plot of the impedance spectra of three styles of symmetric cells after 10 cycles at 2 mA cm−2. See also Figures S6–S8 and S10. Joule 2017 1, 563-575DOI: (10.1016/j.joule.2017.06.004) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 6 Electrochemical Performance: Full Cells (A) The charge/discharge profiles of full cells with LiFePO4 as the cathode and 3D-HCFs@Li (Cu@Li, Li foil) as the anode at 0.2 C. inset: enlarged profiles exhibiting the polarization. (B) Cycling performance of the full cells with three styles of anode at 0.2 C. (C) The charge/discharge profiles of full cells with LiFePO4 as the cathode and 3D-HCFs@Li as the anode at 0.5 C. (D) Cycling performance of the full cells at 0.5 C. Joule 2017 1, 563-575DOI: (10.1016/j.joule.2017.06.004) Copyright © 2017 Elsevier Inc. Terms and Conditions