High Power- and Energy-Density Supercapacitors through the Chlorine Respiration Mechanism

Toward Ultrahigh-Rate Energy Storage of 3000 mV s-1 in Hollow Carbon: From Methodology to Surface-to-Bulk Synergy Insights

Despite great efforts on economical and functionalized carbon materials, their scalable applications are still restricted by the unsatisfying energy storage capability under high-rate conditions. Herein, theoretical and methodological insights for surface-to-bulk engineering of multi-heteroatom-doped hollow porous carbon (HDPC), with subtly designed Zn(OH)F nanoarrays as the template are presented. This fine-tuned HDPC delivers an ultrahigh-rate energy storage capability even at a scan rate of 3000 mV s-1 (fully charged within 0.34 s). It preserves a superior capacitance of 234 F g-1 at a super-large current density of 100 A g-1 and showcases an ultralong cycling life without capacitance decay after 50 000 cycles. Through dynamic and theoretical analysis, the key role of in situ surface-modified heteroatoms and defects in decreasing the K+-adsorption/diffusion energy barrier is clarified, which cooperates with the porous conductive highways toward enhanced surface-to-bulk activity and kinetics. In situ Raman aids in visualizing the reversibly dynamic adsorption/releasing of the electrolyte ions on the tailored carbon structure during the charge/discharge process. The potential of the design concept is further evidenced by the enhanced performances in water-in-salt electrolytes. This surface-to-bulk nanotechnology opens the path for developing high-performance energy materials to better meet the practical requirements in the future.

Selenium-Anchored Chlorine Redox Chemistry in Aqueous Zinc Dual-Ion Batteries

Chlorine-based batteries with Cl0 to Cl- redox reaction (ClRR) are promising for high-performance energystorage due to their high redox potential and large theoretical capacity. However, the inherent gas-liquid conversion feature of ClRR together with poor Cl fixation can cause Cl2 leakage, reducing battery reversibility. Herein, we utilize a Se-based organic molecule, diphenyl diselenide (di-Ph-Se), as the Cl anchoring agent and realize an atomic level-Cl fixation through chalcogen-halogencoordinating chemistry. The promoted Cl fixation, with two oxidized Cl0 anchoring on a single Ph-Se, and the multivalence conversion of Se contributeto a six-electron conversion process with up to 507 mAh g-1 and an average voltage of 1.51 V, as well as a high energy density of 665 Wh Kg-1 . Based on the superior reversibility of thedeveloped di-Ph-Se electrode with ClRR, a remarkable rate performance (205 mAh g-1 at 5 A g-1 ) and cycling performance (capacity retention of 77.3 % after 500cycles) are achieved. Significantly, the pouch cell delivers a record arealcapacity of up to 6.87 mAh cm-2 and extraordinary self-discharge performance. This chalcogen-halogen coordination chemistry between the Se electrode and Cl provides a new insight for developing reversible and efficientbatteries with halogen redox reactions.

Toward Ultrahigh-Rate Energy Storage of 3000 mV s-1 in Hollow Carbon: From Methodology to Surface-to-Bulk Synergy Insights

Despite great efforts on economical and functionalized carbon materials, their scalable applications are still restricted by the unsatisfying energy storage capability under high-rate conditions. Herein, theoretical and methodological insights for surface-to-bulk engineering of multi-heteroatom-doped hollow porous carbon (HDPC) is presented, with subtly designed Zn(OH)F nanoarrays as the template. This fine-tuned HDPC delivers an ultrahigh-rate energy storage capability even at a scan rate of 3000 mV s-1 (fully charged within 0.34 s). It preserves a superior capacitance of 234 F g-1 at a super-large current density of 100 A g-1 and showcases an ultralong cycling life without capacitance decay after 50 000 cycles. Through dynamic and theoretical analysis, the key role of in situ surface-modified heteroatoms and defects in decreasing the K+ -adsorption/diffusion energy barrier is clarified, which cooperates with the porous conductive highways toward enhanced surface-to-bulk activity and kinetics. In situ Raman further aids in visualizing the reversibly dynamic adsorption/releasing of the electrolyte ions on the tailored carbon structure during the charge/discharge process. The potential of the design concept is further evidenced by the enhanced performances in water-in-salt electrolytes. This surface-to-bulk nanotechnology opens the path for developing high-performance energy materials to better meet the practical requirements in future.

Rechargeable Hydrogen-Chlorine Battery Operates in a Wide Temperature Range

Hydrogen-chlorine (H2-Cl2) fuel cells have distinct merits due to fast electrochemical kinetics but are afflicted by high cost, low efficiency, and poor reversibility. The development of a rechargeable H2-Cl2 battery is highly desirable yet challenging. Here, we report a rechargeable H2-Cl2 battery operating statically in a wide temperature ranging from -70 to 40 °C, which is enabled by a reversible Cl2/Cl- redox cathode and an electrocatalytic H2 anode. A hierarchically porous carbon cathode is designed to achieve effective Cl2 gas confinement and activate the discharge plateau of Cl2/Cl- redox at room temperature, with a discharge plateau at ∼1.15 V and steady cycling for over 500 cycles without capacity decay. Furthermore, the battery operation at an ultralow temperature is successfully achieved in a phosphoric acid-based antifreezing electrolyte, with a reversible discharge capacity of 282 mAh g-1 provided by the highly porous carbon at -70 °C and an average Coulombic efficiency of 91% for more than 300 cycles at -40 °C. This work offers a new strategy to enhance the reversibility of aqueous chlorine batteries for energy storage applications in a wide temperature range.