Pursuing all-solid-state lithium metal batteries with dual upgrading of safety and energy density is of great significance. However, searching compatible solid electrolyte and reversible conversion cathode is still a big challenge. The phase transformation at cathode and Li deformation at anode would usually deactivate the electrode–electrolyte interfaces. Herein, we propose an all-solid-state Li-FeF₃ conversion battery reinforced by hierarchical microsphere stacked polymer electrolyte for the first time. This g-C₃N₄ stuffed polyethylene oxide (PEO)-based electrolyte is lightweight due to the absence of metal element doping, and it enables the spatial confinement and dissolution suppression of conversion products at soft cathode-polymer interface, as well as Li dendrite inhibition at filler-reinforced anode-polymer interface. Two-dimensional (2D)-nanosheet-built porous g-C₃N₄ as three-dimensional (3D) textured filler can strongly cross-link with PEO matrix and LiTFSI (TFSI: bistrifluoromethanesulfonimide) anion, leading to a more conductive and salt-dissociated interface and therefore improved conductivity (2.5 × 10^–4 S/cm at 60 °C) and Li⁺ transference number (0.69). The compact stacking of highly regular robust microspheres in polymer electrolyte enables a successful stabilization and smoothening of Li metal with ultra-long plating/striping cycling for at least 10,000 h. The corresponding Li/LiFePO₄ solid cells can endure an extremely high rate of 12 C. All-solid-state Li/FeF₃ cells show highly stabilized capacity as high as 300 mAh/g even after 200 cycles and of ~200 mAh/g at extremely high rate of 5 C, as well as ultra-long cycling for at least 1200 cycles at 1 C. High pseudocapacitance contribution (>55%) and diffusion coefficient (as high as 10^–12 cm²/s) are responsible for this high-rate fluoride conversion. This result provides a promising solution to conversion-type Li metal batteries of high energy and safety beyond Li-S batteries, which are difficult to realize true “all-solid-state” due to the indispensable step of polysulfide solid–liquid conversion.

追求安全性和能量密度双重升级的全固态锂金属电池意义重大。然而，寻找兼容的固体电解质和可逆转换阴极仍然是一个很大的挑战。阴极的相变和阳极的锂变形通常会使电极-电解质界面失活。在此，我们首次提出了一种由分级微球堆叠聚合物电解质增强的全固态Li-FeF _{3转换电池。}这个 gC ₃ N ₄填充聚环氧乙烷 (PEO) 基电解质由于没有金属元素掺杂而重量轻，它能够在软正极-聚合物界面处对转化产物进行空间限制和溶解抑制，以及在填料增强负极处抑制锂枝晶-聚合物界面。二维 (2D)-纳米片构建的多孔 gC ₃ N ₄作为三维 (3D) 纹理填料可以与 PEO 基质和 LiTFSI（TFSI：双三氟甲磺酰亚胺）阴离子强烈交联，从而导致导电性和盐解离性更高界面，因此提高了电导率（60 °C 时为2.5 × 10 ^{–4 S/cm）和 Li +}转移数 (0.69)。聚合物电解质中高度规则的坚固微球的紧凑堆叠能够通过至少 10,000 小时的超长电镀/剥离循环成功稳定和平滑锂金属。相应的 Li/LiFePO ₄固体电池可以承受 12 C 的极高倍率。全固态 Li/FeF ₃电池显示高度稳定的容量，即使在 200 次循环后也高达 300 mAh/g 和 ~200 mAh/g在 5 C 的极高速率下，以及在 1 C 下至少 1200 个循环的超长循环。高赝电容贡献 (>55%) 和扩散系数（高达 10 ^–12 cm ²/s) 负责这种高速率氟化物转化。这一结果为锂硫电池之外的高能量和安全的转换型锂金属电池提供了一个有前途的解决方案，由于多硫化物固液转换必不可少的步骤，难以实现真正的“全固态”。