Electrochemical Grain Refinement Enables High-Performance Lithium–Aluminum-Anode-Based All-Solid-State Batteries

Lithium–aluminum (Li_xAl, x = the molar ratio of Li to Al), an important alloy anode with a specific capacity over 2 times higher than that of the carbon anode used in commercial liquid electrolyte lithium-ion batteries (LELIBs), has been proven to be a failure in LELIBs due to the notorious pulverization phenomenon. However, whether or not such pulverization persists in all solid state lithium batteries (ASSLBs) remains unclear. Herein, we show that pulverization of the Li_xAl anode is mitigated in ASSLBs due to the applied external stack pressure, thus preventing the mechanical failure of the Li_xAl anode in ASSLBs. Moreover, electron microscopy investigation reveals that, instead of pulverization, electrochemomechanical stress induces 2 orders of magnitude grain size reduction from a few tens of microns to a few hundred nanometers. The grain-refined Li_xAl anode facilitates lithium ion transport, which improves the rate performance and specific capacity of the Li_xAl anode. Consequently, the assembled single-crystal LiNi_0.83Co_0.12Mn_0.05O₂|Li₁₀Si_0.3PS_6.7Cl_1.8|Li_0.4Al ASSLBs reach 2000 cycles with a capacity retention of 100% at 3C (13.9 mA/cm², room temperature), at a high areal capacity of 2.1 mAh/cm². The all-solid pouch cell with a Li_xAl anode can reach an energy density of 219 Wh kg^–1 based on the total mass of the cell. These results demonstrate the prospect of implementing the Al-based anode in ASSLBs for practical energy storage applications.