Phthalocyanine nickel enhanced composite solid-state electrolytes with homogenous and fast Li-ion conduction for high-voltage Li-metal batteries

Herein, a novel composite solid-state polymer electrolytes (CSEs) was regulated by introducing CoNi-MOF (Metal-organic framework) @NiPc (Nickel phthalocyanine) nanofiller (CMN) into PEO (polyethylene oxide) matrix. In this novel system, the NiPc uniformly wrapped around the surface of MOF through hydrogen bond bridging, avoiding the agglomeration of the MOF particles. The chemisorption between Ni²⁺ in NiPc and the O atoms in the bis(triffuoromethanesulfonyl)imide anion (TFSI^-) restricted the mobility of the anions within the CSEs, which improved the release of Li⁺ ions from the NiPcLi. In addition, the π-π conjugated groups present in NiPc facilitated a spontaneous formation of additional lithium ion transport channels within the PEO (polyethylene oxide) matrix. The novel CSEs displayed a Li⁺ transference number of 0.79 and ionic conductivity (2.65 × 10^-4 S cm^-1). The nitro groups at the peripheral position of NiPc acted as intermediaries that firmly combined the PEO and MOF via the formation of mutual hydrogen bonds, avoiding the shedding of active materials from the base polymer and ensuring long-term stability. Moreover, the decrease in the HOMO (highest occupied molecular orbital) energy level of the obtained CSEs indicated an improvement in its ability to resist oxidation. Consequently, an Li//Li(Ni_0.8Co_0.1Mn_0.1O₂) (NCM811) high-voltage battery containing the obtained CSEs displayed good performance. The Li⁺ transport and enhanced electrochemical stability window of the MNPL were further revealed by theoretical calculations. Overall, these results demonstrated a new strategy for the design and preparation of high-performance CSEs through the introduction of multifunctional MPc (Metal phthalocyanine) for solid-state rechargeable Li-metal batteries.