Composite solid electrolytes containing single-ion lithium polymer grafted garnet for dendrite-free, long-life all-solid-state lithium metal batteries

Abstract

Compared with traditional liquid electrolytes, the composite solid electrolytes (CSE) composed of polymer and inorganic particle fillers show better electrochemical stability and safety in lithium-ion batteries. However, the low lithium ion transference number (tLi+) and filler agglomeration still threat CSE performance. In response to these threats, we proposed a flexible anion-immobilized modified ceramic-polymer composite solid electrolyte, which significantly increased the lithium ion transference number and showed promising performance after assembled in an all-solid-state battery. Primarily, the surface of Ta-doped garnet Li6.4La3Zr1.4Ta0.6O12 (@LLZTO) was modified by a silane coupling agent bearing C = C bonds, then the lithium single-ion polymer (lithium (4-styrenesulfonyl) (trifluoromethanesulfonyl) imide (LiSTFSI)) was chemically grafted onto the above particles resulting in the ceramic-polymer composite particles (Li@LLZTO). These particles can be uniformly distributed in the polyethylene oxide (PEO) matrix to form composite solid electrolyte (PL@LCSE). It is found that the PL@LCSE promotes the dissociation of lithium salt and reduces the crystallinity of PEO, and shows a relatively high restriction on the migration of anions. Therefore, PL@LCSE shows a high ionic conductivity (1.5 mS·cm−1), a wide electrochemical window (∼5.3 V vs. Li/ Li+) and a high tLi+ (0.77). The Li/PL@LCSE/Li battery exhibits long cycle stability (cycling more than 1000 h). Excellent cycling stability and high rate capability are demonstrated in the all-solid-state batteries with LiFePO4 and LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode. Consequently, the synthesized garnet-lithium single-ion polymer composite micron particles have great potential in the next generation of all-solid-state lithium metal batteries.