Structure Design And Surface-Driven Energy Storage Behavior Of Porous Carbon Materials Derived From Sodium Alginate

Zinc-ion hybrid capacitors（ZIHCs）have attracted tremendous attention for their excellent energy/power densities and long cycle lifespan.However,the research system of ZIHCs is still immature.The key to tackle the dilemma of energy storage dynamics and cycle stability of ZIHCs lies in developing carbon-based electrode materials with low cost and high performance.This thesis focuses on the structural design of new porous carbon materials.The natural advantages of sodium alginate self-template were utilized to optimize the carbon matrix from the perspectives of pore structure and heteroatom doping.The energy storage behavior of materials is fully explored by assembling zinc ion capacitors and supercapacitors,which provides a new idea for the follow-up development and application of advanced zinc ion capacitors.The results of this paper are as follows:（1）The microporous sodium alginate-derived carbon materials were prepared by hydrothermal polymerization and carbonization pyrolysis with biomass sodium alginate as carbon precursor,KCl and self-template as double templates.The effect of double template strategy on the morphology,structure and electrochemical characteristics of porous carbon materials were evaluated by a series of characterization methods.Among them,DSPCs-1 sample has the optimal double template activation effect,with a specific surface area of872.6 m²g^-1and a pore volume of 0.462 cm³g^-1.The electrochemical test results show that the symmetrical capacitors based on DSPCs-1 show energy densities of 10.17 and 3.80 Wh kg^-1at power densities of 150 and 6000 W kg^-1,respectively.It broadens the working potential range of water system.The ZIHCs system can reach an outstanding energy density of 99.22 wh kg^-1,and has extraordinary cyclability.（2）The electrochemical properties of ZIHCs carbon-based electrode materials were simply and effectively improved by reasonably adjusting the configuration of heteroatoms in porous carbon.Sodium alginate is used as matrix,NH₄B₅O₈is used as N and B source.The high content N/B co-doped sodium alginate-based hierarchical porous carbon materials were synthesized by strong hydrogen bonding and carbonization.The synergistic mechanism of N and B and the effect of doping amount on the morphology and structure of materials were explored by a series of characterization methods.Among them,NBSPC-4 has the optimal doping ratio of N and B,with N content of 9.61 at%and B content of 6.47 at%.In the symmetrical capacitor system,the reversible specific capacitance of NBSPC-4 reaches 182.9 F g^-1at 0.5 A g^-1.The extreme values of energy/power density are 6.35 Wh kg^-1and 5 k W kg^-1,respectively.And it has an overlength cycle lifespan of 30,000 times.Furthermore,a zinc-ion capacitor was constructed with NBSPC-4 as cathode,which can achieve an ultrahigh energy density of 162.94 Wh kg^-1at 200 W kg^-1.The capacity retention rate is as high as 94.5%and CE is close to 100%in 15,000 cycle tests at 10 A g^-1.In addition,in order to expand the application range of NBSPC-4 samples,a flexible ZIHCs is designed and developed,which can maintain good flexibility and stability under stress.The electrochemical test exhibits that the initial cycle specific charge capacity is 61.1 m Ah g^-1,and the CE is about 32.2%.It also has excellent rate performance and cyclability.This result fully proves the superiority and feasibility of this work,and provides a new way for heteroatom doped carbon materials to be used in high-performance storage devices.