Multifunctionalized Safe Separator Toward Practical Sodium‐Metal Batteries with High‐Performance under High Mass Loading

Abstract

Introducing sodium as anode to develop sodium metal batteries (SMBs) is a promising approach for improving the energy density of sodium-ion batteries. However, fatal problems, such as uncontrollable sodium dendrite growth, unstable solid electrolyte interphase (SEI) in low-cost carbonate-based electrolytes, and serious safety issues, greatly impede the practical applications. Here, a multifunctionalized separator is rationally designed, by coating PP separator (<25 µm) with a solid-state NASICON-type fast ionic conductor layer (NZSP@PP) to replace the widely used thick glass fiber separator (>200 µm) and successfully solves all of the above problems, and for the first time creats high performance SMBs by using Na 3 V 2 (PO 4 ) 3 (NVP) cathodes in pouch cell. The Na||NVP full cells can stably cycle over 1200 times with capacity retention of 80% at a high rate of 10 C and deliver a specific capacity of 80 mAh g −1 even at high rate of 30 C, indicating extraordinary fast-charging characters. The full SMBs can also stably cycle 200 times with a retention of 96.4% under high NVP loading of 10.7 mg cm −2 . Most importantly, the SMB pouch cell can also deliver a long-life cycles as well as high-temperature battery performance, which guarantees the safety of SMBs in practical application.

Tailoring composite gel polymer electrolytes with regularly arranged pores and silica particles for sodium metal batteries via breath-figure self-assembly

“…33 In addition to dimensional stability, it is crucial to retain as much liquid electrolyte as possible at elevated temperatures to ensure efficient ion conduction and prevent safety incidents. 18,35 The liquid electrolyte retention ability was evaluated by measuring the weight change of the electrolyte-wetted membranes upon heating at a rate of 2 °C min −1 (Fig. 2e).…”

“…Among them, the incorporation of inorganic additives into composite polymer electrolytes for Na batteries has attracted significant attention, similar to their use in Li battery systems. Inorganic materials, such as Na 3 Zr 2 Si 2 PO 12 (NZSP), 18 metal–organic frameworks, 19 cellulose nanocrystals (CNCs), 20 and β-Al 2 O 3 (ref. 21) serve as reinforcing fillers, enhancing the thermomechanical stability of polymer electrolytes, while also providing additional ion-conducting pathways through their interaction with Na ions.…”

Wide-temperature-range sodium-metal batteries: from fundamentals and obstacles to optimization

“…159 Therefore, the environmental temperature can cause fluctuations in the electromotive force of SMBs, which makes the output voltage and capacity extremely unstable during cycling, thereby leading to battery failure. 120,176 Conclusively, fully considering the interference of extreme environments, especially LT and HT, is an undeniable factor in promoting the practical application of SMBs. 176…”

“…120,176 Conclusively, fully considering the interference of extreme environments, especially LT and HT, is an undeniable factor in promoting the practical application of SMBs. 176…”

“…Owing to the high reactivity and low potential of sodium metal, some issues during the deposition of Na + , such as sluggish dynamics, unstable SEI layer, dendritic growth and volume expansion, threaten the cycling stability, reversibility and safety of SMBs. 176–178 In this section, these issues are carefully explored and the mechanism of Na + deposition revealed.…”