Optimized Modification Of Manganese Dioxide Cathode Material And Construction Of Flexible Zinc Ion Battery

Flexible electronic devices,as an important branch in the field of digital technology,are developing in full swing worldwide.Flexible zinc ion batteries（ZIBs）are the most promising new generation of flexible power sources due to their outstanding performance in terms of environment,cost and performance.MnO₂ has become one of the most important cathode materials for ZIBs because of its high theoretical capacity,high operating voltage,rich crystalline shape and stable structure.However,due to the dissolution problem and low conductivity of MnO₂,their development still faces challenges.In this thesis,flexible ZIBs with both flexibility and stability are prepared,focusing on improvements to MnO₂ based materials,including compounding carbon materials to improve charge transfer,using doping strategies to stabilize lattice tunneling,as well as optimizing the structural design of the devices.The details are as follows:（1）The CNT@MnO₂ ink with three-dimensional structure was prepared by hydrothermal method by compounding the active material MnO₂ with carbon nanotubes（CNT）,and the planar type flexible zinc ion micro-battery was prepared by3D printing technology.In the design of the cathode material,CNT acts as the core to provide a rich conductive network inside the material,while MnO₂ is used as the shell to cover the CNT surface.This structure can increase the specific surface area of the material and reduces the internal resistance to accelerate the carrier transport.In addition,the undesirable consequences caused by dendrite growth are eliminated by constructing the planar structure of the micro-battery,and the stability of the battery is improved.The discharge specific capacity of the coin cell based on CNT@MnO₂cathode is 298 m Ah g^-1 at 0.1 A g^-1,and the Zn//CNT@MnO₂ micro-battery has a discharge specific capacity of 63μAh cm^-2 at a current density of 0.4 m A cm^-2.The maximum capacity change rate of the micro-battery under different bending states is only 2.72%,demonstrating excellent stability and flexibility.（2）A Mo-dopedα-MnO₂ grown on carbon cloth（CC）for a CC@MMO flexible cathode was prepared using a hydrothermal method.Characterization and first-principles calculations show that the pillaring effect of Mo atoms can stabilize the tunneling structure and reduce the migration barrier of zinc ions.As a result,the battery capacity increases to 1.64 times at a current density of 0.1 A g^-1 and retains 80%of its capacity after 1392 deep cycles at 0.5 A g^-1,which is leading the current study.In addition,the electrode exhibits a unique array structure at the microscopic level,in which independently grown nanowires help buffer external stresses and improve the flexibility and stability of the electrode,and the microstructure of the electrode remains well maintained after repeated bending for 50 times.Ultimately,the Zn//CC@MMO flexible battery has a discharge capacity of 0.56 m Ah cm^-2 at 0.3 m A cm^-2,and is stable in supplying energy to electronic products under various deformations or external stresses,demonstrating its excellent practicality.