A strong-surface-polarity separator enables dendrite-free lithium metal anodes via coordinated garnet electrolyte

Lithium metal anodes (LMAs) are considered to be the holy grail materials for the new generation of energy storage batteries due to the extremely high theoretical specific capacity and low redox potential. However, the uncontrollable growth of lithium dendrites induces serious safety concerns. Herein, polyacrylonitrile (PAN) coordinated Li6.4La3Zr1.4Ta0.6O12 (LLZTO) (LLZTO@PAN) is used as a functional layer to endow the strong surface polarity to the polypropylene (PP) separator by introducing a large number of polar groups, which not only improves its wettability to the electrolyte, but also increases the lithium ion migration number (tLi+) by immobilizing anions. Moreover, the coordinated LLZTO with improved water dispersion stability makes it possible to replace oily slurry with aqueous slurry, and avoids the coagulation of binder in oily slurry caused by the interaction between LLZTO and organic systems, significantly improving the uniformity of the functional layer. Those effects synergistically optimizes lithium ions (Li+) transfer kinetics on the surface of LMAs, resulting in the obvious suppression of lithium (Li) dendrites. As a consequence, Li symmetrical cells can cycle stably for 2000 h at 2 mA cm−2, and the Li|LiFePO4 (LFP) cell exhibits superior cycling stability at 2C with a capacity retention of 80.7 % after 1000 cycles. This work provides an effective strategy for the well-match of existing commercial separators with LMAs, and expects to advance the practical application of lithium metal batteries (LMBs).