Tailoring Nitrogen Species in Disk-Like Carbon Anode Towards Superior Potassium Ion Storage

Good Cycling Stabilities of Sn/SnO2/C/S Composite Electrodes with Introduced Active Tin Atoms in Li-S Batteries

Polysulfides are easily dissolved in the electrolyte of Li-S batteries after long cycles. Sn atom modification electrodes are beneficial for improving cycling stabilities of Li-S batteries. However, the influence of Sn atoms on the structure and electrochemical performance of SnO2/C composite materials is not explored. Sn/SnO2/C composite materials are developed as sulfur carriers in Li-S batteries in our work. In addition, the cycling stability mechanism of Sn/SnO2/C/S composite electrodes is also elucidated. Results show that introduced Sn/SnO2/C/S composite electrodes display good cycling stability (420.1 mAh·g-1 at 1C after 1000 cycles) in Li-S batteries. The sulfur load of Sn/SnO2/C/S composite electrodes is 80 wt % (2 mg-1·cm-2). The introduction of Sn into Sn/SnO2/C/S composite electrodes plays three roles. The first role is to enhance the structural stability of SnO2. The second role is to help adsorb active sulfur ions. The last role is to promote the electron transportation ability during the initial discharging/charging process. Sn/SnO2/C/S composite electrodes are beneficial for inhibiting the dissolution of polysulfides in electrolytes after long cycles.

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.

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.

Dynamically Evolving Multifunctional Protective Layer for Highly Stable Potassium Metal Anodes

The construction of an artificial protective layer is an effective method to solve the issues, such as uncontrolled dendrite growth and an unstable solid electrolyte interphase, at the K metal anode. This study proposes a new dynamic evolution strategy that integrates the advantages of previous in situ and ex situ fabrication processes. A multifunctional protective layer enriched with K-Ge alloy is prepared on the K metal electrode by simple surface modification and in situ reduction via an electrochemical process. The protective layer has good potassiophilicity, mechanical flexibility, and high ionic conductivity, which can inhibit dendrite growth and reduce side reactions. The protected K electrode with a protective layer exhibits dendrite-free K plating/striping behavior, and the symmetric cell can run stably for over 1000 h at 1 mA cm-2 and 1 mAh cm-2. Notably, full cells based on this electrode also present excellent rate and cycling performance compared to those of the bare K electrode. This peculiar strategy will open a new avenue for metal anode protection and can be extended to other high-energy battery systems.