Planar Sodium-Nickel Chloride Batteries with High Areal Capacity for Sustainable Energy Storage

摘要

High-temperature sodium-nickel chloride (Na-NiCl_2) batteries are a promisingsolution for stationary energy storage, but the complex tubular geometryof the solid electrolyte represents a challenge for manufacturing. A planarelectrolyte and cell design is more compatible with automated mass production.However, the planar cell design also faces a series of challenges, suchas the management of molten phases during cycling. As a result, cycling ofplanar high-temperature cells until now focused on moderate areal capacitiesand current densities. In this work, planar cells capable of integrating costefficientnickel/iron electrodes at a substantially enhanced areal capacity of150 mAh cm~(?2) is presented. Due to a low cell resistance during operation at300 ℃, these cells deliver a specific discharge energy of 300 Wh kg~(?1) at highdischarge current densities of 80 mA cm~(?2) (C/2, 10%–100% state-of-charge).This results represent the first demonstration of planar Na-NiCl_2 cells at acommercially relevant combination of areal capacity, cycling rate, and energyefficiency. It is further identified the secondary molten NaAlCl_4 electrolyteto contribute to the cell capacity during cycling. Mitigating electrochemicaldecomposition of NaAlCl_4 will play an important role in further enhancingboth cycling rates and cycle life of high temperature Na-NiCl_2 batteries.