Interfacial engineering via in situ LiK bimetallic alloy formation for high-performance solid polymer electrolyte lithium batteries

In this study, we present an innovative interfacial engineering strategy to enhance the performance of lithium metal batteries by constructing a Li K bimetallic alloy anode formed in situ from a LiCl-KCl sacrificial layer. During initial charge-discharge cycles, the sacrificial layer transforms into a protective interphase that undergoes reversible deposition and decomposition. This in situ formation alleviates mechanical stress from lithium deposition, reduces local current density, and promotes uniform Li + deposition. Characterizations using X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry confirm a significant reduction in interfacial resistance, improved electrochemical reversibility, and excellent rate capability. Tested in Li||LFP cells, this approach achieves a high specific capacity of 175 mAh g −1 at 0.5C, retaining 154 mAh g −1 after 200 cycles, with an 11.4 to 13.5 % capacity improvement across various current densities (0.1–2C). In addition, Li||Li symmetric cells exhibit stable cycling for over 500 h at 0.1 mA cm −2 , demonstrating excellent interfacial stability and dendrite suppression. Experimental results demonstrate that this strategy markedly enhances cycling stability and safety, while its simplicity and adaptability offer valuable insights for interfacial design in high-performance lithium metal batteries.