Lignin-reinforced PVDF electrolyte for dendrite-free quasi-solid-state Li metal battery

Quasi-solid-state lithium metal batteries (QSSLMBs) assembled with polyvinylidene fluoride (PVDF) are a promising class of next-generation rechargeable batteries due to their safety, high energy density, and superior interfacial properties. However, PVDF has a series of inherent drawbacks such as low ionic conductivity, ease of crystallization, and hydrophobic character that leading to poor cell properties. To tackle these issues, a lignin-reinforced PVDF electrolyte is proposed in this work to solve these drawbacks of PVDF and enhance the comprehensive performance of QSSBs. The lithophilic polar groups of lignin can promote uniform deposition of Li on the electrodes. Cooperating with the improved mechanical properties can efficiently prevent Li dendrites penetration through the separator. In addition, more active sites provided by lignin can also enhance Li⁺ transport and lead to a faster electrochemical reaction kinetic. Benefitting from the ingenious design, Li symmetric cells with 5% lignin-PVDF quasi-solid-state electrolyte can operate for 900 h at a high current density/capacity of 5 mA·cm⁻²/5 mAh·cm⁻², while short-circuiting occurs after 56 h for the counterpart (pure PVDF). Moreover, a full cell of Li/5% lignin-PVDF/LFP cell demonstrates a high capacity of 96.2 mAh·g⁻¹ after 2000 cycles at 10 C. This work is expected to open up promising opportunities to develop other high-energy/power-density QSSLMBs.