Multifunctional Properties of Al₂O₃/Polyacrylonitrile Composite Coating on Cu to Suppress Dendritic Growth in Anode-Free Li-Metal Battery

The utilization of an anode-free lithium-metal battery (AFLMB) is pivotal in meeting the high-energy-density demand for portable electronic devices and vehicles. However, the dendritic growth of lithium (Li) and continuous SEI formation on Copper (Cu) current collector limits the lifetime of a cell. Here we report the effect of milled Al2O3/polyacrylonitrile (PAN) composite layer (AOP) coated on Cu, as AOP@Cu, to encourage compact and smoother Li+ deposition extracted from NMC (333) cathode. The excellent wettable nature of the AOP layer promotes uniform ionic flux and improved kinetics. The multifunctional AOP layer offers moderate mechanical support and sufficient strength to the SEI layer to suppress dendritic growth. The formation of Li–Al–O/Al2O3 species at the bottom part of the layer reveals AOP’s lithiophilicity to form new SEI components, besides Al–F, by regulating Li+ deposition. PAN synergism is manifested by its flexible binding role and nitrogen content that has an excellent affinity to Li+. The resulting AOP@Cu||NMC and AOP@Cu||Li cells demonstrated improved cycling stability and Coulombic efficiency. An AOP@Cu||NMC cell run at 0.2 mA cm–2 exhibits a first cycle discharge capacity of 160 mAh g–1 that retains 30% after 82 cycles, whereas the Cu||NMC cell retains ∼30% after only 52 cycles.