Controlled Preparation And Potassium Storage Performance Of Nickel-based Anode Materials

Potassium ion batteries(PIBs)have received extensive attention because of low cost and abundant natural reserves.Nickel-based materials have been widely investigated including alloys-mechanismed materials and Ni2P.And it’s essential to clarify the mechanism of potassium storage,find feasible synthesis strategies and enhance the electrochemical performance.Therefore,in this thesis,Ni2P anchored on nitrogen/phosphorus co-doped porous nanosheets and Ni-Sn intermetallic nanocrystals immobilized on nitrogen-doped graphene were synthesized as PIBs anode materials.The main contents are as follows:(1)Two-dimensional composite structures of Ni2P nanoparticles embedded in nitrogen-phosphorus co-doped porous carbon nanosheets(Ni2PcN/P-CNS)were synthesized based on an in situ self-templating transformation strategy.Importantly,this strategy simplifies the synthesis of transition metal phosphate-based hybrids,avoiding the introduction of strong reducing agents,organic solvents and additional carbon sources.The construction of such hierarchical structures effectively relieves low electronic conductivity,kinetic hindrance and large volume changes.The density functional theory(DFT)calculations confirm that the Ni2PcN/P-CNS possesses strong potassium ion adsorption ability,facilitating the reaction kinetics.In situ X-ray diffraction(XRD)further confirms a typical solid-solution reaction potassium storage mechanism.A reversible capacity of 301 mAh g-1 can be achieved after 250 cycles at 0.1 A g-1 with a decay of only 0.01%per cycle.Even after 3000 cycles at 10 A g-1,a capacity of 109 mAh g-1 can be retained.(2)Based on the above work,the structure consisting of intermetallic compound Ni1.5Sn nanocrystals immobilized in nitrogen-doped graphene was designed.The presence of Ni1.5Sn and combination with nitrogen-doped graphene effectively enhance the electron transfer kinetics and provide more favorable channels for the diffusion of ions,boosting the electronic conductivity and structural integrity,displaying excellent electrochemical performance.The capacity is about 319 mAh g-1 after 4800 cycles at 2.0 A g-1,indicating good long-term cycling.This work suggests a feasible strategy to construct the hierarchical structures as the PIBs anode materials.