Polyethylene oxide film coating enhances lithium cycling efficiency of an anode-free lithium-metal battery

Abstract

The practical implementation of an anode-free lithium-metal battery with promising high capacity is hampered by dendrite formation and low coulombic efficiency. Most notably, these challenges stem from non-uniform lithium plating and unstable SEI layer formation on the bare copper electrode. Herein, we revealed the homogeneous deposition of lithium and effective suppression of dendrite formation using a copper electrode coated with a polyethylene oxide (PEO) film in an electrolyte comprising 1 M LiTFSI, DME/DOL (1/1, v/v) and 2 wt% LiNO3. More importantly, the PEO film coating promoted the formation of a thin and robust SEI layer film by hosting lithium and regulating the inevitable reaction of lithium with the electrolyte. The modified electrode exhibited stable cycling of lithium with an average coulombic efficiency of ∼100% over 200 cycles and low voltage hysteresis (∼30 mV) at a current density of 0.5 mA cm-2. Moreover, we tested the anode-free battery experimentally by integrating it with an LiFePO4 cathode into a full-cell configuration (Cu@PEO/LiFePO4). The new cell demonstrated stable cycling with an average coulombic efficiency of 98.6% and capacity retention of 30% in the 200th cycle at a rate of 0.2C. These impressive enhancements in cycle life and capacity retention result from the synergy of the PEO film coating, high electrode-electrolyte interface compatibility, stable polar oligomer formation from the reduction of 1,3-dioxolane and the generation of SEI-stabilizing nitrite and nitride upon lithium nitrate reduction. Our result opens up a new route to realize anode-free batteries by modifying the copper anode with PEO to achieve ever more demanding yet safe interfacial chemistry and control of dendrite formation.

Magnetic Field–Suppressed Lithium Dendrite Growth for Stable Lithium‐Metal Batteries

“…[4,29,48] However, under magnetic field, the hysteresis voltage rises with the increase of current density, but it is still very stable without any irregular fluctuations. [64] The application of magnetic field can also improve the rate performance, shown in Figure 6b. This fully demonstrates that the magnetic field contributes to the reversible de-intercalation process of lithium, promotes the uniform deposition of lithium, and improves the rate performance.…”

“…2019, 9,1900260 the cycling stability of the full cell. [64] The application of magnetic field can also improve the rate performance, shown in Figure 6b. The specific capacity reaches 97 mAh g −1 at 4 C, and it still maintains 132 mAh g −1 when returns to 0.5 C. While the rate capacity of the sample without magnetic field is only 68 mAh g −1 at 4 C, and 112 mAh g −1 when backs at 0.5 C. The voltage profiles at different rates under magnetic field are investigated, as shown in Figure 6c.…”

Unfolding the Hidden Message of Anode-Free Lithium Metal Battery

“…3g. The Li//Cu cell is a useful protocol to provide reliable information for the study of electrolyte 23,24,27 , and surface engineering approaches 25,31,32 for mitigating the irreversible Coulombic efficiency ascribed to dead Li formation and reductive electrolyte decomposition.…”

Dendrite‐Free Lithium Plating Induced by In Situ Transferring Protection Layer from Separator

“…First, nonuniform Li deposition with a resulting formation of dendritic Li tends to penetrate porous separator and lead to an internal short circuit and a following extremely fast temperature increase, causing fire or explosion . Second, the Li dendritic depositions can easily falloff from the Li metal anode surface and create the so‐called “dead Li.” Third, stable solid electrolyte interfacial (SEI) layer is hard to be established during changing Li/electrolyte interface, leading to a fast depletion of the liquid electrolyte . All these factors will deteriorate battery performance and limit the application of Li metal in batteries .…”