A promising successor to the state-of-the-art lithium ion batteries is the lithium metal battery (LMB). The high theoretical specific capacity (3860 mAh g-1) and low gravimetric density (0.534 g cm-3) of lithium create auspicious conditions for a cell with a high energy density and specific energy. However, there are some challenges that complicate the entry barrier into commercialization. The inhomogeneous plating on lithium metal leads to the formation of high surface area lithium (HSAL) caused by repeated deposition and dissolution. The continuous formation of the solid electrolyte interphase (SEI) on the HSAL is accompanied by electrolyte and lithium consumption leading to irreversible capacity losses. Furthermore, the aforementioned effects result in a reduced cycle life and safety risks. Another obstacle is the infinite relative volume change of lithium metal electrodes during deposition and dissolution. This volume expansion causes severe challenges for its housing on cell level and accommodation on cell pack level. A promising strategy to prevent this is the directed deposition into 3D structured lithium metal or current collectors.
The application of a lithiated copper mesh as negative electrode was compared to roll-pressed lithium metal on copper foil. A directed lithium deposition in the voids of the copper mesh was observed at a current density of 0.4 mA cm-1. The deposition on top of the copper metal showed a more compressed morphology than the deposition on top of the initial lithium metal.
The initial overpotentials of the cells containing the copper mesh were slightly higher than those of the cells containing the copper foil as a current collector, but decreased after 80 hours reaching comparable values to the overpotentials of the cells containing the copper foil. The overpotentials of the cells containing the lithiated copper mesh after repetitive charging and discharging at 1.0 mA cm 2 for 1 h after 650 cycles were higher than those of the cells containing lithiated copper foil while still being functional.
In terms of electrochemical performance, the cells with the copper mesh and those with the copper foil as current collector for the lithium metal electrode showed very similar results, regarding to the course of the specific discharge capacity (starting at 160 mAh g-1) and the Coulombic efficiencies (close to 100%) over more than 200 cycles.
Summarizing the results, the implementation of the 3D structured copper mesh as a current collector in LMBs was considered successful. The general suitability was proven by a beneficial behaviour in terms of the porosity of the deposited Lithium and a diminished volume change, as well as an electrochemical performance on a par with plain copper foil.
The Author wants to thank the European Union’s Horizon Europe Research and Innovation Programme for funding within the PSIONIC project (Grant Agreement N. 101069703).