In response to the development demand for lithium metal batteries (LMBs) with high energy density and high safety, this study reports a composite solid electrolyte (LPCNE) prepared from poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), cyclopentane-1,1-dicarbonitrile (CPDCN), and Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO). Through gravitational sedimentation, a functionally oriented continuous gradient structure forms inside LPCNE, in which the PVDF-HFP rich layer facing the cathode offers excellent oxidation resistance, while the high modulus LLZTO rich layer facing the lithium metal anode (LMA) effectively suppresses lithium dendrite growth. Such a continuous gradient structure eliminates the interfacial impedance caused by delamination between the organic and inorganic phases, achieving a smooth compositional transition. The incorporation of CPDCN as α-H free nitrile plasticizer increases the ionic conductivity of LPCNE to 0.69 mS cm^–1, and the coordination of CPDCN with metal atoms on the LLZTO surface significantly reduces the concentration of free cyano groups, thereby effectively suppressing side reactions between cyano groups and lithium metal. Consequently, the Li/LPCNE/Li symmetric cell exhibits stable cycling for over 2000 h, and the LiFePO₄/LPCNE/Li cell delivers a discharge specific capacity of 158.3 mAh g^–1 at 0.2 C with 78.4% retention after 650 cycles. Moreover, LPCNE possesses a wide electrochemical stability window of 4.75 V, enabling the LiNi_0.6Co_0.2Mn_0.2O₂/LPCNE/Li cell to deliver a discharge specific capacity of 163.9 mAh g^–1 at 0.1 C with 70% retention after 250 cycles. This study achieves differentiated functionality by adjusting the gradient distribution of the composite solid electrolyte components, providing an innovative solution for high-performance LMBs.

High Li⁺ transference number electrolytes have long been understood to provide attractive candidates for realizing uniform deposition of Li⁺. However, such electrolytes with immobilized anions would result in incomplete solid electrolyte interphase (SEI) formation on the Li anode because it suffers from the absence of appropriate inorganic components entirely derived from anions decomposition. Herein, a boron-rich hexagonal polymer structured all-solid-state polymer electrolyte (BSPE+10% LiBOB) with regulated intermolecular interaction is proposed to trade off a high Li⁺ transference number against stable SEI properties. The Li⁺ transference number of the as-prepared electrolyte is increased from 0.23 to 0.83 owing to the boron-rich cross-linker (BC) addition. More intriguingly, for the first time, the experiments combined with theoretical calculation results reveal that BOB⁻ anions have stronger interaction with B atoms in polymer chain than TFSI⁻, which significantly induce the TFSI⁻ decomposition and consequently increase the amount of LiF and Li₃N in the SEI layer. Eventually, a LiFePO₄|BSPE+10% LiBOB|Li cell retains 96.7% after 400 cycles while the cell without BC-resisted electrolyte only retains 40.8%. BSPE+10% LiBOB also facilitates stable electrochemical cycling of solid-state Li-S cells. This study blazes a new trail in controlling the Li⁺ transport ability and SEI properties, synergistically.

The self-healing solid polymer electrolytes (SHSPEs) can spontaneously eliminate mechanical damages or micro-cracks generated during the assembly or operation of lithium-ion batteries (LIBs), significantly improving cycling performance and extending service life of LIBs. Here, we report a novel cross-linked network SHSPE (PDDP) containing hydrogen bonds and dynamic disulfide bonds with excellent self-healing properties and non-flammability. The combination of hydrogen bonding between urea groups and the metathesis reaction of dynamic disulfide bonds endows PDDP with rapid self-healing capacity at 28 °C without external stimulation. Furthermore, the addition of 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl)imide (EMIMTFSI) improves the ionic conductivity (1.13 × 10⁻⁴ S cm⁻¹ at 28 °C) and non-flammability of PDDP. The assembled Li/PDDP/LiFePO₄ cell exhibits excellent cycling performance with a discharge capacity of 137 mA h g⁻¹ after 300 cycles at 0.2 C. More importantly, the self-healed PDDP can recover almost the same ionic conductivity and cycling performance as the original PDDP.

Succinonitrile-based plastic crystal electrolytes have emerged for high-energy-density Li metal batteries in terms of their superior ambient ionic conductivity, low flammability, and benign compatibility with high voltage cathode, but are hampered by inherent instabilities toward Li anodes. Constructing hierarchical solid electrolytes structure is a fundamental approach to protect Li anode from succinonitrile attacks, with succinonitrile-based oxidation-resistance layer facing high voltage cathode and reduction-tolerant layer contacting Li anode. However, free succinonitrile molecules in succinonitrile-based electrolyte layer can diffuse across the electrolyte/electrolyte interface and further reach Li anode surface during the battery cycle. This chemical “crosstalk” cause reduction-tolerant electrolyte layer to fail to protect the Li anode from the attacks of free succinonitrile molecules. Nano Li_6.4La₃Zr_1.4Ta_0.6O₁₂ is introduced creatively into succinonitrile-based electrolyte layer. By taking advantage of the complexation between La atoms in Li_6.4La₃Zr_1.4Ta_0.6O₁₂ and N atoms in succinonitrile, the free succinonitrile molecules are successfully immobilized in succinonitrile-based electrolyte layer. The resulting low resistance and highly durable solid electrolyte interphase and cathode electrolyte interphase endow NCM622||Li batteries with remarkable cycle stability. Our research provides a new idea for the real application of plastic crystal electrolytes in high voltage solid-state lithium metal batteries.