A Rechargeable "Rocking Chair" Type Zn-CO2 Battery.

Rising global temperatures and critical energy shortages have spurred researches into CO2 fixation and conversion within the realm of energy storage such as Zn-CO2 batteries. However, traditional Zn-CO2 batteries employ double-compartment electrolytic cells with separate carriers for catholytes and anolytes, diverging from the "rocking chair" battery mechanism. The specific energy of these conventional batteries is constrained by the solubility of discharge reactants/products in the electrolyte. Additionally, H2O molecules tend to trigger parasitic reactions at the electrolyte/electrode interfaces, undermining the long-term stability of Zn anodes. In this report, we introduce an innovative "rocking chair" type Zn-CO2 battery that utilizes a weak-acidic Zn(OTf)2 aqueous electrolyte compatible with both cathode and anode. This design minimizes side reactions on the Zn surface and leverages the high catalytic activity of the cathode material, allowing the battery to achieve a substantial discharge capacity of 6734 mAh g-1 and maintain performance over 65 cycles. Moreover, the successful production of pouch cells demonstrates the practical applicability of Zn-CO2 batteries. Electrode characterizations confirm superior electrochemical reversibility, facilitated by solid discharge products of ZnCO3 and C. This work advances a "rocking chair" Zn-CO2 battery with enhanced specific energy and a reversible pathway, providing a foundation for developing high-performance metal-CO2 batteries.

Universal Design Strategy for Air-Stable Layered Na-Ion Cathodes toward Sustainable Energy Storage.

Na-ion batteries (NIBs) are sustainable alternatives to Li-ion technologies due to the abundant and widely-distributed resources. However, the most promising cathode materials of NIBs so far, O3 layered oxides, suffer from serious air instability issues, which significantly increases the manufactural cost and carbon footprint because of the long-term use of dry rooms. While some feasible strategies are proposed via case studies, universal design strategies for air-stable cathodes are yet to be established. Herein, the air degradation mechanisms of O3 cathodes are investigated via combined first-principles and experimental approaches, with bond dissociation energy proposed as an effective descriptor for predicting air stability. Experimental validations in various unary, binary, and ternary O3 cathodes confirm that the air stability can indeed be effectively improved via simple compositional design. Guided by the predictive model, the designed material can sustain 30-day air-storage without structural or electrochemical degradation. It is calculated that such air-stable cathodes can significantly reduce both energy consumption (≈4 100 000 kWh) and carbon footprint (≈2200-ton CO2) annually for a 2 GWh NIBs manufactory. Therefore, the fundamental understandings and universal design strategy presented open an avenue for rational materials design of NIBs toward both elemental and manufactural sustainability.