High-energy-density lithium metal batteries (LMBs) are confronted with crucial concerns of security and a short cycle lifespan caused by the uncontrollable formation of lithium (Li) dendrites. The poor thermal stability and heterogeneous Li deposition of conventional polyolefin separators often cause battery short circuiting and thermal runaway in LMBs. Herein, a novel dual-functional PE composite separator (PI-COOH/PE) coated by carboxyl polyimide (PI) microspheres is fabricated by an etching-acidification method. The three-dimensional (3D) high-temp PI microsphere with rich carboxyl groups on the surface improve the security of LMBs at extremely high temperatures and facilitate the formation of a stable and uniform SEI layer, which contributes to accelerating the Li⁺ transport and stabilizing the formation of the SEI layer. Consequently, the Li symmetric cell assembled with the (PI-COOH)/PE separator exhibits stable overpotential over 3000 h, and the corresponding Li//NCM811 full cells also show a high-level discharge capacity of 146.6 mAh g^–1 at 5 C. Meanwhile, it also demonstrates outstanding cycling stability and thermal safety, which can survive continuously over 160 min at 140 °C (vs 21 min for PE). The above results indicate the (PI-COOH)/PE separator constructed by a low-cost and industrial-friendly strategy simultaneously addresses high-temperature stability and dendrite resistance.

中文翻译：

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通过 3D 增强聚酰亚胺微球保护层实现调节离子传输的双功能隔膜，用于无枝晶和高温锂金属电池

高能量密度锂金属电池（LMB）面临着安全性和锂（Li）枝晶的不可控形成导致的短循环寿命等关键问题。传统聚烯烃隔膜的热稳定性差和锂沉积不均匀常常导致LMB电池短路和热失控。在此，通过蚀刻-酸化方法制备了一种涂覆有羧基聚酰亚胺（PI）微球的新型双功能PE复合隔膜（PI-COOH/PE）。表面具有丰富羧基的三维（3D）高温PI微球提高了LMB在极高温度下的安全性，并有利于形成稳定均匀的SEI层，有助于加速Li ⁺传输和稳定SEI层的形成。因此，与(PI-COOH)/PE隔膜组装的Li对称电池表现出超过3000小时的稳定过电势，相应的Li//NCM811全电池在5 C下也表现出146.6 mAh g ^–1的高水平放电容量同时，它还表现出出色的循环稳定性和热安全性，可以在140°C下连续存活超过160分钟（而PE则为21分钟）。上述结果表明，采用低成本和工业友好策略构建的(PI-COOH)/PE隔膜同时解决了高温稳定性和抗枝晶问题。