| Sodium/potassium ion battery has become a research hotspot because of its low cost,abundant sodium/potassium ion storage capacity and similar working principle to lithium ion battery.However,sodium/potassium ions have a large diameter,which is easy to destroy the structure of positive and negative materials in the process of charge and discharge,resulting in the rapid attenuation of battery capacity.Therefore,the key to improve the performance of sodium/potassium ion battery is to develop a negative electrode material with stable structure and rapid de embedding of sodium/potassium ion.Among many negative electrode materials,layered sulfide(Mo S2,Sn S2)is regarded as one of the most potential negative electrode materials because of its large layer spacing and high theoretical capacity.However,layered sulfide has poor conductivity and large volume expansion in the process of charge and discharge,which seriously affects its electrochemical performance in sodium/potassium ion battery.Therefore,in this paper,layered sulfide and bagasse carbon matrix composite were selected to prepare a new cathode material with three-dimensional electron ion transport network through a simple strategy,which was successfully applied to sodium/potassium ion battery,and its electrochemical properties and sodium/potassium storage mechanism were studied.The main research contents include the following two aspects:1)Bagasse,an agricultural and forestry waste,was used as carbon source.After pretreatment,Mo S2 was loaded on bagasse carrier through hydrothermal reaction with molybdenum source and sulfur source.After high-temperature treatment,the carbonization of Mo S2 interlayer carbohydrates and the"self splitting"carbonization of bagasse carrier were realized simultaneously,and the flower cluster Mo S2/C heterojunction@carbon nanomesh composite(Mo S2/C@CNs)was obtained.The flower cluster Mo S2/C heterojunction is evenly embedded in the nano carbon network formed by the"self splitting"carbonization of bagasse.Nano carbon mesh can not only buffer the volume expansion of Mo S2,but also build a three-dimensional electron/ion transport network inside the electrode;The flower cluster Mo S2/C heterojunction maximizes the interface contact between Mo S2 and carbon atoms,which is conducive to improve the intrinsic conductivity and structural stability of the material.Mo S2/C@CNs electrode shows excellent potassium storage performance.After 200 cycles at200 m A g-1 current density,it still maintains a high reversible specific capacity of 350m A h g-1;After 2000 cycles of stable cycling at 2000 m A g-1 high current density,the specific capacity remained at 198 m A h g-1.In addition,we preferred Mo S2/C@CNs The research shows that the KFSI potassium salt electrolyte with 1M concentration shows the best electrochemical performance.2)Using bagasse as carbon source,layered tin disulfide/bagasse composite precursor was synthesized by simple hydrothermal method,and then carbonized at high temperature and calcined in acetylene/argon mixed atmosphere to realize acetylene carbonization coating Sn S2/carbon nanomesh@carbon composite(Sn S2/C@C)was obtained.Sn S2 nanoparticles are uniformly loaded on the carbon nanomesh substrate,and the surface of Sn S2 is tightly coated with acetylene vapor deposited carbon layer.Under the synergistic effect of this double carbon structure,Sn S2/C@C The sodium storage performance of the negative electrode material is significantly improved compared with the pure Sn S2 negative electrode.After 70 cycles at 200 m A h g-1 current density,the specific capacity remains at 200 m A g-1,while the specific capacity of pure Sn S2 negative electrode has attenuated to 6 m A h g-1 after 10 cycles under the same test conditions.The double carbon structure formed by carbon nanomesh substrate and surface carbon layer coating can jointly improve the structural stability of Sn S2,and constant current intermittent titration(GITT)and electrochemical impedance(EIS)tests show that Sn S2/C@C with double carbon structure.Negative electrode materials are also conducive to the rapid transmission of electrons and ions.In addition,based on this synthetic route,single-layer carbon nanomesh materials were further prepared by step-by-step calcination.The fiber diameter of the carbon nanomesh is about 8 nm,which has the characteristics of large pore size and high conductivity.Lithium ion battery,sodium ion battery and potassium ion battery all show high specific capacity and super stability.This functional single-layer carbon nanomesh has broad application prospects in the fields of energy storage,catalysis and so on. |
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