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.
To enhance the stability and safety of solid-state lithium metal batteries under high voltage and high energy density conditions, a flexible inorganic–organic hybrid solid-state electrolyte based on polyacrylic acid–boric acid–anhydrous lithium hydroxide–lithium oxalate salt (LiPAAOB) and holey graphene oxide (HGO) was designed and fabricated. By optimizing the doping ratio of HGO, the LiPAAOB&HGO composite electrolyte exhibited optimal electrochemical performance. This composite electrolyte achieved an ionic conductivity as high as 1.5 × 10 −3 S cm −1 at room temperature, significantly exceeding that of the unmodified PVDF-based solid electrolyte (4.6 × 10 −4 S cm −1 ); its activation energy was 0.14 eV, demonstrating excellent lithium-ion mobility. An electrochemical stability window of 4.3 V with good redox reversibility was gained; the lithium-ion transference number (t Li + ) reached 0.77, markedly higher than that of conventional Poly (vinylidene fluoride) (PVDF)-based electrolytes. Linear sweep voltammetry (LSV) further confirmed that the electrochemical stability window of the electrolyte could be extended up to 5.2 V, meeting the requirements for high-voltage cathode materials. Regarding battery performance, the Li | LiPAAOB&HGO SPE | Li symmetric cell achieved stable cycling for over 2900 h under testing conditions of 0.2 mA cm −2 , verifying its excellent interfacial stability and dendrite suppression ability; the Li | LiPAAOB&HGO SPE | LiFePO₄ full cell retained 71.5 % capacity after 900 cycles at 1C rate, with an average coulombic efficiency as high as 99.8 %.
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