Accommodating Lithium into a Three-Dimensional Carbon Framework As the Anode for Rechargeable Lithium Batteries

Abstract

Introduction Lithium has drawn great attentions for its unprecedentedly high theoretical specific capacity (3860 mAh g-1) and low redox potential (-3.04V vs NHE). However, the growth of lithium dendrites will cause security problems which restrict the application of lithium metal. It has been proved that the current collector could play an important role in the protection of the lithium metal. In this work, we report a kind of carbon paper which can effectively relieve the growth of lithium dendrites as a three-dimensional (3D) current collector. This 3D-network material, which is constructed with carbon nanotube fibers, can provide a conductive network and a large specific surface area for lithium deposition. The lithium-ions can deposit on the fiber surface uniformly which confines lithium metal deposition within the 3D current collectors. Therefore, this 3D current collector gives a good result to suppress the growth of lithium dendrites. Result and Discussion Fig. 1 (a) and (d) show the SEM images of the original carbon paper before charge-discharge cycles. The carbon paper is consisted of interwoven carbon fibers, which provide much larger specific surface area and more internal spaces than lithium foil to confine lithium deposition inside the 3D-structured current collectors. Fig. 1 (b), (c) and (e) show the SEM images of the carbon paper after cycles. We can obviously see that lithium metal deposits on the surface of carbon paper and no lithium dendrites can be observed. As a comparison, after the same charge-discharge cycles, a lot of lithium dendrites can be found on the surface of the lithium foil and the surface becomes very rough (Fig 1 (f)). Fig.1 (g) shows the galvanostatic discharge/charge voltage profiles of lithium anode with the carbon paper as current collector. The lithium deposition process exhibits a low overpotential of 20 mV at 0.4 mA cm-2. Fig.1 (h) shows the cycling performance of the Li/carbon paper electrode. We can see that the Li/carbon paper electrode exhibits stable voltage profiles at 0.4 mA cm-2 even after more than 570 hours charge-discharge cycles which proves that this 3D current collector exhibits an outstanding cycling stability. In this work, we use a commercial carbon paper as a 3D current collector to suppress the growth of lithium dendrites. Benefitting from the three-dimensional conductive framework which can provide electronic conduction channel to ensures the lithium ion deposit more uniformly. And this 3D current collector can also provide sufficient internal space for lithium metal deposition. Therefore, this 3D carbon current collector gives good results to inhibit the growth of the lithium dendrite. Fig. 1 (a), (d) SEM images of the original carbon paper; (b), (e) SEM images of carbon paper after lithium deposition; (c) SEM image of carbon paper (cross-section) after cycles. (f) SEM image of lithium foil (top) after cycles. (g) Galvanostatic discharge/charge voltage profile of the Li/carbon paper electrode at 0.4mA cm-2. (h) Voltage profiles of Li plating/stripping at 0.4mA cm-2 in the Li/carbon paper electrode. Figure 1