N-Doped C/ZnO-Modified Cu Foil Current Collector for a Stable Anode of Lithium-Metal Batteries

Abstract

The security concerns and poor stability caused by lithium (Li) dendrites and volume changes are the main obstacles posed by the Li-metal batteries (LMBs). These serious issues need to be addressed before LMBs can be commercialized. Herein, a simple way to process the ZIF-8 precursor was designed to oxidize Zn to ZnO; at the same time, the surface of ZnO was coated with a layer of N-doped carbon material to prepare N-doped C/ZnO (NCZ) composite anode. As a lithiophilic framework, the NCZ composite anode acts as a steady Li "host" during the deposition/stripping process of Li. N doping not only improves the conductivity but also provides additional active sites for the deposition of Li. The LiZn alloy formed by ZnO and Li + promotes the uniform deposition and distribution of Li and mitigates the Li dendrite formation caused by an uneven Li-ion distribution. The conductive carbon interconnection framework provides convenient electron/ion transmission channels and alleviates the volume change. Combined with the above strengths, the Li/CF@NCZ composite symmetrical cell has a good cycle endurance of over 1600 h with an ultralow voltage hysteresis (22 mV) at 5 mA cm −2 with 5 mAh cm −2 . This study presents a facile strategy for developing dendrite-free Li-metal anodes.

Controllable and Homogeneous Lithium Electrodeposition via Lithiophilic Anchor Points

“…Moreover, X-ray photoelectron spectroscopic (XPS) analysis was performed on the pristine and lithiated ZnO to verify the presence of LiZn after lithiation (Figure S4). The binding energy of pristine ZnO was divided into peaks at 1021.8 eV (Zn 2p 3/2 ) and 1044.9 eV (Zn 2p 1/2 ) eV with an energy separation of 23.1 eV . As expected, the peaks of lithiated ZnO at 1021.7 and 1044.8 eV are attributed to Zn(0), while the peaks at 1017.2 and 1040.3 eV are attributed to Zn alloying with Li, which corroborates the implication from the XRD results, i.e., the reactions of ZnO + Li → LiZn x + LiO 2 .…”

“…The binding energy of pristine ZnO was divided into peaks at 1021.8 eV (Zn 2p 3/2 ) and 1044.9 eV (Zn 2p 1/2 ) eV with an energy separation of 23.1 eV. 29 As expected, the peaks of lithiated ZnO at 1021.7 and 1044.8 eV are attributed to Zn(0), while the peaks at 1017.2 and 1040.3 eV are attributed to Zn alloying with Li, which corroborates the implication from the XRD results, i.e., the reactions of ZnO + Li → LiZn x + LiO 2 . In particular, the LiZn/Li 2 O nanorod arrays supplied homogeneous anchor points to guide dendrite-free ion deposition.…”

Lithiophilic Cu3Sn Modified Cu Foil as Current Collector for Stable Lithium Metal Anodes

“…On the contrary, the surface of the sample Li@Cu 3 Sn-150 (Figure 3b) is flat, indicating that the Li could fill the surface of the sample uniformly, which could effectively avoid the violent volume expansion of Li. [16] Besides, we also use molten Li and electrochemical deposition to show Li climbing/plating behavior with the Cu 3 Sn-150 sample. Beneficial from its abundant lithiophilic sites, from Figure S4, while placing the Cu 3 Sn-150 onto the molten Li, Li could be infused into it uniformly.…”

“…The XRD pattern of Cu 3 Sn also further demonstrates that the use of electroplating and heat treatment can lead to the successful combination of Cu and Sn elements, which also has a positive effect on the suppression of Li dendrites. [16,21] For further analysis of the success of Cu 3 Sn coating, the elemental composition of the Cu 3 Sn-150 and its chemical valence states are investigated by X-ray photoelectron spectroscopy (XPS). The XPS spectrum of full survey, which is shown in Figure 2g, reveals a coexistence of Cu, Sn and O elements.…”

“…Modifying the surface structure, lithiophilicity, and surface composition of the commercial Cu foil could effectively inhibit the generation of Li dendrites. Researchers have proposed a variety of lithiophilic materials to modify electrodes, for example, (1) polymer film, such as modifying Cu surface with polydopamine coating layer [12] and poly(dimethyl siloxane) thin film; [13] (2) single metal layer, including using highly lithiophilic metal Zn [14] and Ag [15] on Cu foil; (3) oxide modification layer, in‐situ ZnO [16] or CuO [17] growth on Cu foil; (4) alloy layer, alloys with lithiophilic properties such as CuGa 2 , [18] Cu 2 Mg [19] could realize a uniform nucleation and growth of Li metal. Although above alloy surface modification of Cu foil could inhibit the formation of Li dendrites, there are challenges of their processes that need to be addressed.…”