A lean-zinc anode battery based on metal-organic framework-derived carbon

Improving zinc metal(Zn^(0))reversibility and minimizing the N/P ratio are critical to boosting the energy density of Zn^(0) batteries.However,in reality,an excess Zn source is usually adopted to offset the irreversible zinc loss and guarantee sufficient zinc cycling,which sacrifices the energy density and leads to poor practicability of Zn^(0) batteries.To address the above conundrum,here,we report a lean-Zn and hierarchical anode based on metal-organic framework(MOF)-derived carbon,where trace Zn^(0) is pre-reserved within the anode structure to make up for any irreversible zinc source loss.This allows us to construct low N/P ratio Zn^(0) full cells when coupling the lean-Zn anode with Zn-containing cathodes.Impressively,high Zn^(0) reversibility(average Coulombic efficiency of 99.4% for 3000 cycles)and long full-cell lifetime(92% capacity retention after 900 cycles)were realized even under the harsh lean-Zn condition(N/P ratio:1.34).The excellent Zn reversibility is attributed to the hierarchy structure that homogenizes zinc ion flux and electric field distribution,as confirmed by theoretical simulations,which therefore stabilizes Zn^(0) evolution.The lean-Zn anode design strategy will provide new insights into construction of high-energy Zn^(0) batteries for practical applications.

Design Principle,Optimization Strategies,and Future Perspectives of Anode‑Free Configurations for High‑Energy Rechargeable Metal Batteries

Metal anodes(e.g.,lithium,sodium and zinc metal anodes)based on a unique plating/stripping mechanism have been well recognized as the most promising anodes for next-generation high-energy metal batteries owing to their superior theoretical specific capacities and low redox potentials.However,realizing full utilization and the theoretical capacity of metal anodes remains challenging because of their high reactivity,poor reversibility,and nonplanar metal evolution patterns,which lead to irreversible loss of active metals and the electrolyte.To minimize the above issues,excess metal sources and flooded electrolytes are generally used for laboratory-based studies.Despite the superior cycling performance achieved for these cells,the metal-anode-excess design deviates from practical applications due to the low anode utilization,highly inflated coulombic efficiency,and undesirable volumetric capacity.In contrast,anode-free configurations can overcome these draw-backs while reducing fabrication costs and improving cell safety.In this review,the significance of anode-free configurations is elaborated,and different types of anode-free cells are introduced,including reported designs and proposed feasible yet unexplored concepts.The optimization strategies for anode-free lithium,sodium,zinc,and aluminum metal batteries are summarized.Most importantly,the remaining challenges for extending the cycle life of anode-free cells are discussed,and the requirements for anode-free cells to reach practical applications are highlighted.This comprehensive review is expected to draw more attention to anode-free configurations and bring new inspiration to the design of high-energy metal batteries.

Laser processed micro-supercapacitors based on carbon nanotubes/manganese dioxide nanosheets composite with excellent electrochemical performance and aesthetic property

Micro-supercapacitors with excellent electrochemical performance and aesthetic property are realized using the carbon nanotubes/manganese dioxide nanosheets（CNTs/δ-MnO2） composite as electrodes.This CNTs/d-MnO2 nanocomposite is excellently compatible with the slurry dispensing process for electrode fabrication, and thus is conducive for preparing thick electrode films, which exhibits a specific capacitance of 257 F/g with an electrode thickness of 13μm. By involving laser-scribing technique, the electrode film can be patterned with a high resolution and fabricated into a planar micro-supercapacitor,showing the maximum energy density of 6.83 mWh/cm^3 at the power density of 154.3 mW/cm^3, and maintained a value of 2.71 mWh/cm^3 at the maximum power density of 2557.5 mW/cm^3. Considering the versatility of the laser-scribing technical platform, the micro-supercapacitors fabricated in this way exhibit excellent aesthetic property and can cater to various miniaturized wearable electronic applications. This technology opens up opportunities for facile and scalable fabrication of high performance energy devices with shape diversity and a meaning of art.