Research On The Preparation And Potassium/Sodium Ion Storage Performance Of Carbonaceous Anode Materials

The current fossil fuel dominated energy framework is accompanied by the shortage of nature sources and non-negligible environmental concerns,which has greatly promoted the research on exploiting renewable energy based techniques.To address the inherent uneven distribution and intermittency of various renewable energy sources(e.g.wind,solar,water,and etc.),it is necessary to develop cost effective largescale electrochemical energy storage devices.Owing to the natural abundance,low cost and electrochemical analogue with Li,potassium/sodium(K/Na)based energy storage devices,such as potassium/sodium ion batteries(KIBs/SIBs)and hybrid capacitors(KIHCs/SIHCs),are drawing increasing attentions.However,the much larger K+/Na+radius(1.38/0.98 (?))compared with that of Li+(0.68 A),generally causes seriously sluggish ion diffusion kinetics and inferior cycling stability,which puts forward high requirement on the composition,morphology and dimension of the electrode materials.During the past decades,carbonaceous materials hold a great potential as a typical series of anode candidates for a variety of energy storage devices due to the advantages of low cost,high electronic conductivity and high physicochemical stability.However,their extended applications for K+/Na+ storage are limited due to the sluggish intercalation kinetics and limited theoretical capacity.Herein,to address the abovementioned challenges,this dissertation develops a series of carbonaceous materials and greatly improves its K+/Na+ storage performance.Meanwhile,the relationships between performance and structure(e.g.morphology,structure,composition,and etc.)are systematically studied.The main contents are summarized as follows:1.The hierarchical nest-like TiO2-nitrogen-doped carbon hybrid nanostructures(TiO2/NC-HN)were fabricated through a facile one-pot strategy based on supramolecular assembly followed by simple thermal annealing treatment,which exhibited outstanding electrochemical performance for both sodium and potassium ion storage with largely improved specific capacity and cycling capability.Specifically,it can deliver a high specific capacity of 382.5 and 323.1 mAh g-1 at the rate of 100 mA g-1 for Na+ and K+ storage,respectively.Moreover,it can also maintain decent storage capacity and ultra-stable cycling capability under high rates.More importantly,the KIHCs based on TiO2/NC-HN anode and activated carbon(AC)cathode can deliver a high energy density of 108.6 Wh kg-1 at the power density of 95 W kg-1 and exhibit superior cycling stability up to 30000 cycles at the rate of 2.5 A g-1.2.The Sn cluster incorporated and nitrogen doped carbonaceous hierarchical nanosheet-assembly(denoted as c-SnNC-HNA)were prepared,which exhibits great potential as universal alkali metal ion host with high reversible capacity and outstanding lifespan.Specifically,it can deliver a high specific capacity of 357.3,360.9 and 1326.7 mAh g-1 at the rate of 0.1 A g-1 for K+,Na+ and Li+ storage,respectively.Besides,it can also maintain decent storage capacity and ultra-stable cycling capability under high rates.The combination of ex-situ XPS and in-situ Raman spectrum meaturaments reveal the carbon sbstrate,nitrogen species and Sn species in the carbon materials can function as active sites for K+ storage.The enhanced ion diffusion kinetics were demonstrated by Galvanostatic intermittent titration technique(GITT).More importantly,the KIHCs based on c-SnNC-HNA anode and AC cathode can deliver a decent energy/power density of 112.5 Wh kg-1/49.1 W kg-1 and exhibit superior cycling stability up to 10 K cycles at 2 A g-1,demonstrating its great potential for practical applications.3.The bi-functional hierarchical porous P/N co-doped pancake-like carbon(PNPanC)was prepared,which delivered superior anions/cations(K+/FSI-)storage performance.Specifically,the PN-PanC delivers high specific capacity(385.8 mAh g1 at 100 mA g-1),stable cycling capability(2000 cycles with an average attenuation rate of 0.21‰ at 1000 mA g-1)for anode application,and remarkable specific capacity(94.2 mAh g-1 at 100 mA g-1)when evaluated as cathode.The origins of the concurrently enhanced K+/FSI-storage are studied by ex-situ XPS,in-situ Raman,EIS analysis and DFT calculations,which could be attributed to the synergistic effect of hierarchical porous structure,exposed active sites,tuned electronic structure and enhanced ion adsorption kinetics.Importantly,the KIHCs assembled by using PN-PanC as both anode and cathode can achieve an outstanding energy density of 155.9 Wh kg-1 at 76.1 W kg-1.Even working at a high power density of 11309.1 W kg-1,it can still retain a promising energy of 22.0 Wh kg-1 and ultra-long lifespan of 20K/40K cycles with decent capacity retentions of 93.4%/77.0%at 500/1000 mA g-1,respectively.4.The Sn incorporated and P/N co-doped carbon with disk-like morphology(P/Nsn-CD)were prepared,where the tuning of nitrogen species and the stabilizing of high content P/N heteroatoms were realized by simply changing the content of SnCl2·2H2O.the P/Nsn-CD electrode can deliver a high specific capacity of 439.3 mAh g-1 at 0.1 A g-1 with a capacity retention of 94.5%after 500 cycles for K+ storage.Besides,it can also maintain decent storage capacity and ultra-stable cycling capability under high rates.The superior K+ storage performance can be attributed to the increased edge-nitrogen species,improved content and stability of P/N heteroatoms,which can be well proved by ex-situ XPS and DFT calculation results.Moreover,the GITT measurement,EIS analysis and calculated DOS results suggest the improved ionic/electronic conductivity are also conductive to the K+ storage.More importantly,when coupled with AC cathode,the KIHCs based on P/Nsn-CD anode can deliver a remarkable energy density of 171.7 Wh kg-1 at 106.8 W kg-1 and power density of 14027.0 W kg-1 with 31.2 Wh kg-1 retained,and ultra-stable and ultra-long lifespan of 30K cycles with 89.7%capacity retention at a rate of 2 A g-1,proving the promising prospect for future practical application.Finally,we summarized the progress of carbonaceous materials as anode in potassium ion storage and look forward to the next research direction.