Mortise-tenon joints reinforced Janus composite solid-state electrolyte with fast kinetics for high-voltage lithium metal battery

Bilayer composite solid-state electrolytes (CSSEs) are regarded as promising candidates to meet the requirements of high-voltage lithium metal batteries due to their exceptional compatibility with both opposite electrodes. However, such a configuration usually leads to additional interfacial impedance between CSSEs and discontinuous Li+ migration process, resulting in deteriorated electrochemical performances. Herein, a Janus electrolyte with mortise and tenon joints (JCSSE) is proposed for enhancing interfacial compatibility. It is composed of poly (vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP))/Li6.4La3Zr1.4Ta0.6O12 layer toward cathode and poly(diallyldimethylammonium) bis(trifluoromethanesulfonyl)imide (PDADMATFSI)/UiO-66-SO3Li layer to Li-metal anode. Such a configuration enables not only intimate contact between the two electrolyte layers, but regulated Li+ coordination environment which would improve Li+ transference number. Both simulation and experimental characterization suggest that the defluorinated-P(VDF-HFP) with low highest occupied molecular orbital (HOMO) and PDADMATFSI with strong adsorption energy toward lithium metal can favor the formation of stable electrode/electrolyte interface. Optimized JCSSE exhibits a high ionic conductivity of 0.21 mS cm−1 at 25°C and a wide electrochemical window of 5.0 V. As a result, Li//JCSSE//LiNi0.8Mn0.1Co0.1O2 battery could deliver remarkable cycling performances at 4.3 V for 100 cycles. In addition, JCSSE enables superior cyclability from 25 to 100°C. High-voltage pouch cells employing JCSSE exhibit unexpected endurance under harsh conditions. This novel Janus electrolyte with tenon and mortise structure will accelerate the commercialization of high-energy-density lithium metal batteries.