Dual-lithium-salt and continuous Li1.3Al0.3Ti1.7(PO4)3 ion-conduction network for high-performance polyvinylidene fluoride-based solid polymer electrolytes

To enhance the lithium ion transport properties of solid polymer electrolytes, a novel lithium salt—poly(acrylic acid)–boric acid–anhydrous lithium hydroxide–oxalic acid composite (LiPAAOB)—was designed and synthesized. This composite lithium salt was introduced into a polymer system with polyvinylidene fluoride (PVDF) as the matrix, along with LiTFSI, and NASICON-structured Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) was added as an inorganic filler. The resulting solid polymer electrolyte (SPE) exhibits a three-dimensional ion conduction network. LiPAAOB, with its rich carboxyl and borate ester structures, effectively stabilizes anions, increases lithium salt dissociation, and promotes the ordered migration of Li + by providing continuous lithium-affinitive functional groups, significantly improving the Li + transference number. LATP, as an inorganic filler, forms a three-dimensional spatial framework in the polymer system, offering more pathways for Li + migration. This solid polymer electrolyte achieved an ion conductivity of up to 2.34 × 10 −3  S·cm −1 , a Li + transfer number of 0.7 and an enlarged electrochemical window of 5.3 V (vs. Li + /Li), exhibiting excellent electrochemical reversibility. The assembled LiFePO₄|LiPAAOB@LATP SPE|Li full cell retained 90.2 % of its capacity after 500 cycles at 1C rate, and the Li symmetric cell operated stably for over 1800 h at a current density of 0.2 mA·cm −2 , demonstrating excellent interface compatibility and dendrite suppression capability.