The safety concern on the uncontrollable growth of lithium dendrites in liquid electrolytes is the main challenge for high performance lithium-metal batteries. The traditional ex situ solid electrolytes can solve these issues to a great extent but are still plagued by low ionic conductivity, low Li⁺ transference number, and high interfacial impedance. Herein, a solid polymer electrolyte (SPE) with highly concentrated (3.5 M) lithium bis(fluorosulfonyl)imide (LiFSI) in 1,3-dioxolane (DOL) is developed via a simple in situ initiator-free gelation route at room temperature. This simple and ingeniously designed in situ SPE integrates a high ionic conductivity (7.9 mS cm⁻¹ at room temperature), high Li⁺ transference number (0.82), and low interface impedance. As a result, the in situ 3.5 M LiFSI-DOL SPE demonstrates a superior lithium dendrite-free behavior, which enables the Li|Li symmetric battery to be stably stripped/plated for more than 1000 cycles with a low overpotential of 45 mV at 5 mA cm⁻² and 5 mAh cm⁻². Moreover, the Li|Cu battery with the in situ 3.5 M LiFSI-DOL SPE also exhibits a high coulombic efficiency (CE) up to 98.0% at 5 mA cm⁻². In addition, the in situ 3.5 M LiFSI-DOL SPE used in the Li|LiFePO₄ battery leads to superior cycle life (500 cycles), CE (98.8%), rate performance, and good mechanical flexibility. Remarkably, the Li-S batteries with the in situ 3.5 M LiFSI-DOL SPE also show good compatibility and stability. This work shows tremendous prospect toward high performance solid-state lithium-metal batteries by combining the in situ polymerization and high concentration electrolyte.

液态电解质中锂树枝状晶体失控生长的安全问题是高性能锂金属电池的主要挑战。传统的异位固体电解质可以在很大程度上解决这些问题，但仍然受到离子电导率低，Li ⁺转移数低和界面阻抗高的困扰。本文中，通过简单的原位无引发剂凝胶化方法，在室温下开发了一种固态聚合物电解质（SPE），该聚合物具有在1,3-二氧戊环（DOL）中的高浓度（3.5 M）双（氟磺酰基）酰亚胺锂（LiFSI）。这种简单，新颖的原位SPE设计具有高离子电导率（室温下为7.9 mS cm ^-1），高Li ⁺传输数（0.82）和低接口阻抗。结果，原位3.5 M LiFSI-DOL SPE表现出优异的无锂枝晶行为，这使得Li | Li对称电池能够稳定剥离/镀覆超过1000次循环，而在5时低过电位为45 mV。 mA cm ^-2和5 mAh cm ^-2。此外，原位为3.5 M LiFSI-DOL SPE的Li | Cu电池在5 mA cm ^-2时也表现出高达98.0％的高库仑效率（CE）。另外，Li | LiFePO _4中使用的原位3.5 M LiFSI-DOL SPE电池具有出色的循环寿命（500次循环），CE（98.8％），倍率性能和良好的机械柔韧性。引人注目的是，采用原位3.5 M LiFSI-DOL SPE的Li-S电池也显示出良好的兼容性和稳定性。这项工作将原位聚合和高浓度电解质结合在一起，对高性能固态锂金属电池具有广阔的前景。