Retarding Li dendrites growth via introducing porous g-C3N4 into polymer electrolytes for solid-state lithium metal batteries

Solid polymer electrolytes (SPEs) based solid-state lithium metal batteries (SSLMBs) are widespreadly practiced as one of the main technical routes aiming for chemically essential safety with acceptable energy density. However, uncontrollable Li dendrites growth and sluggish Li+ transport remain obstacles to the further development of SPEs-based SSLMBs. Herein, a porous g-C3N4 (PCN) is designed and introduced into polyethylene oxide (PEO). Within the following synthesized PEO-based composite solid electrolyte (PEO/PCN/LiTFSI CSE), PCN is found to be an attractive multifunctional filler. For its porous morphology and high specific surface area, abundant Lewis basic active sites are exposed, which facilitates Li+ to be uniformly distributed in PEO/PCN/LiTFSI CSE and thus more effectively mitigates the Li dendrites growth comparing to those with bulk g-C3N4 filler, making PCN-involved Li symmetrical cell (Li|PEO/PCN/LiTFSI|Li) run steadily for 1400 h under the current density of 0.1 mA cm−2 at 60 °C. PCN also accelerates Li+ transport in the manner of reducing PEO crystallinity and promoting LiTFSI dissociation. The Li+ conductivity of PEO/PCN/LiTFSI CSE reaches 3.47 × 10−4 S cm−1 at 60 °C. Therefore, long life span and high rate performances are together achieved in SSLMB assembled with PEO/PCN/LiTFSI CSE. This work reveals a feasible strategy to fabricate dendrite-free SSLMBs cycling within a fairly long time. •Porous g-C3N4 with rich Lewis basic sites regulates Li+ distribution in electrolytes.•Homogeneous Li+ distribution in electrolytes retards Li dendrites growth.•High-specific-area fillers improve Li+ transport ability of electrolytes.•Long life span and high rate performances are simultaneously achieved in batteries.