Unlocking the NaCl-AlCl3 phase diagram for low-cost, long-duration Na-Al batteries

卷:56

Article

关键词: ELECTRICAL ENERGY-STORAGE;    CHLORIDE;    TEMPERATURE;    ALUMINUM;    CHALLENGES;    SULFUR;    PERFORMANCE;    IMPEDANCE;    PROSPECTS;    CAPACITY;   

DOI  :  10.1016/j.ensm.2023.01.009

来源: SCIE

【 摘 要 】

Sodium and aluminum are a natural combination of inexpensive, abundant elements as a redox pair for battery energy storage. Recent explorations pairing a sodium anode and aluminum cathode have demonstrated reversible, energy dense Na-Al cells with excellent rate capability using the electrochemical reaction between a molten Na anode and a NaAlCl4/Al cathode. In this work, the NaAlCl4/Al cathode is extended beyond the neutral NaAlCl4 composition by unlocking the NaCl-AlCl3 phase diagram to explore the extra accessible capacity hidden in acidic chloroaluminate melts up to and beyond the composition NaAl2Cl7. This enables higher specific ca-pacity and average discharge voltages than previous Na-Al batteries, utilizing two distinct cell reaction mech-anisms in one battery. Fundamental aspects of the NaAlCl4-NaAl2Cl7 reaction chemistry are investigated, and Na-metal/chloroaluminate batteries with excellent reversibility and areal capacity are demonstrated. Increasing the voltage window of the chloroaluminate Na-Al battery takes advantage of the higher voltage (-2 V vs-1.6 V for neutral NaAlCl4) contributed by the acidic chloroaluminate cathode reaction, unlocking an additional specific energy of-119 Wh kg-1 by utilizing the conversion of NaAlCl4 to NaAl2Cl7, which adds to the neutral melt reaction between NaAlCl4/Al and Na (-493 Wh kg -1 theoretical). By significantly increasing the cathode thickness and therefore accessible areal capacity up to 131.7 mAh cm-2, a discharge duration of 28.2 h is achieved with an estimated raw active materials cost of $7.02 kWh-1. These metrics show the great potential of this unlocked chloroaluminate battery for future low-cost, long-duration electrochemical energy storage.

【 授权许可】

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