Carbon Nitrides‐Based Heterojunction for High‐Efficient Li Salt Dissociation

ABSTRACT The solid polymer electrolytes (SPEs) fall short of the stringent requirements of solid‐state lithium metal batteries, primarily due to the insufficient lithium salt dissociation and slow migration rate of Li + ions. In this context, a composite SPE is designed by incorporating H‐CN4@CN5 (C 3 N 5 on the surface of hollow g‐C 3 N 4 ) heterojunction into the polyethylene oxide (PEO) matrix. Such PEO/H‐CN4@CN5 significantly enhances the lithium salt dissociation by means of the spontaneous dipole moment and the built‐in electric fields (BIEFs). In details, the electron depletion region of BIEFs enhances the anchoring of anions, while the electron accumulation region accelerates the rapid migration of Li + ion. Moreover, the particular nanoflower morphology increases active sites for dissociation and transportation, while suppressing the Li dendrite growth. Hence, the Li||PEO/H‐CN4@CN5||Li symmetric cell demonstrates a remarkable stability (2400 h at 0.1 mA cm − 2 ) without lithium dendrites, and the Li||PEO/H‐CN4@CN5||NCM811 batteries achieve a high‐capacity density of 181.2 mAh g − 1 at 0.2 C and a capacity retention of 90.5% after 100 cycles. The heterojunction filler and the innovative heterojunction structure provide a rewarding avenue towards the rational design and preparation of SPEs to build high performance rechargeable solid‐state batteries.