Gel polymer electrolytes are regarded as one of the efficient strategies to substitute traditional liquid electrolytes for achieving safer high energy density sodium ion batteries. However, operating under wide temperature range especially at low temperature under zero is still a great challenge for most gel polymer electrolytes and becomes a hindrance to sodium ion batteries further development. Herein, a multifunctional phosphate gel copolymer electrolyte with larger crosslinking degree and encapsulation over a broader operation temperature range (−20 to 70 °C) is designed and synthesized via in situ free radical copolymerization. This gel polymer electrolyte displays a wide electrochemical stability window up to 5.1 V (vs. Na⁺/Na) and high ionic conductivity even at low temperature of − 20 °C (>1.0 × 10⁻³ S cm⁻¹). Moreover, its outstanding interfacial stability is confirmed via alternating-current impedance and Na plating/stripping experiments. The morphology and X-ray photoelectron spectroscopy data of separators after long cycling suggest the gel electrolyte has ability to inhibit the decomposition of liquid electrolyte and suppress the growth of sodium dendrite, hence enhance the cycling stability of battery efficiently at wide temperature range. As a result, the assembled gel Na||Na₃V₂(PO₄)₃ battery delivers outstanding ultralong cycling stability with superior discharge capacity retention over wide temperature range, including at room temperature (0.002% capacity decay per cycle for 3000 cycles), 60 °C (0.005% fade per cycle for 1500 cycles) and −10 °C (0.002% fade per cycle for 1200 cycles).

凝胶聚合物电解质被认为是替代传统液体电解质以获得更安全的高能量密度钠离子电池的有效策略之一。然而，在宽温度范围尤其是零以下的低温下运行对大多数凝胶聚合物电解质来说仍然是一个巨大的挑战，成为钠离子电池进一步发展的障碍。在此，通过原位自由基共聚设计并合成了一种具有更大交联度和在更宽工作温度范围（-20 至 70 °C）内封装的多功能磷酸盐凝胶共聚物电解质。这种凝胶聚合物电解质显示出高达 5.1 V（相对于Na ⁺/Na) 和高离子电导率，即使在 − 20 °C 的低温下 (>1.0 × 10 ^-3 S cm ^-1 )。此外，通过交流阻抗和 Na 电镀/剥离实验证实了其出色的界面稳定性。长时间循环后隔膜的形貌和X射线光电子能谱数据表明，凝胶电解质具有抑制液态电解质分解和抑制钠枝晶生长的能力，从而有效提高电池在宽温度范围内的循环稳定性。结果，组装凝胶Na||Na ₃ V ₂ (PO ₄ ) ₃电池具有出色的超长循环稳定性，在宽温度范围内具有出色的放电容量保持率，包括室温（3000 次循环，每次循环 0.002% 的容量衰减）、60 °C（1500 次循环，每次循环 0.005% 的衰减）和 −10 °C （每循环 0.002% 褪色，持续 1200 次循环）。