N,S Co-Doped Carbon Based Nanocomposites Derived From Sulfurcontaining Amino Acids Constructed Metal-Organic Frameworks For Lithium/Sodium Storage

Anode materials with transition reaction mechanisms such as transition metal oxides and sulfides have become the focus of attention in lithium/sodium ion batteries due to their high theoretical specific capacities.However,its large volume change during charge and discharge and its low electronic conductivity result in insufficient cycle performance and rate performance.Carbon material modification proved to be an effective means to solve these problems.In this paper,metal-organic frameworks?MOFs?constructed with sulfur-containing amino acids as ligands are used as precursors.Nitrogen and sulfur co-doped carbon-based composites are obtained through one-step carbonization,and their lithium/sodium storage properties are studied.The main content of the paper is as follows:?1?N,S co-doped carbon-based nanocomposites derived from L-cystine constructed MOFs for sodium storage.This chapter uses an efficient and environmentally friendly preparation method to synthesize a series of carbon-coating transition metal sulfide materials.We selected L-cystine as the organic ligand,complexed with different transition metal ions(Mn²⁺,Fe²⁺,Co²⁺,Ni²⁺,Cu²⁺and Zn²⁺)at room temperature to obtain the metal-cystine complex?M-cys?.Then,M-cys were prepared a series of N,S co-doped carbon-coating transition metal sulfide composite materials through one-step carbonization.The composite materials prepared by this process has a core-shell morphology,in which the core is 10-20 nm sulfide particles,and the shell is amorphous carbon.FeS@N,S-C was taken as an example to investigate its electrochemical performance and the effect of different heat treatment temperatures on its electrochemical performance as a negative electrode for sodium ion batteries.FeS@N,S-C-600 has better cycling stability and remarkable rate performance.After 200 cycles(at 0.2 A g^-1),the specific charge and discharge capacity is 689.7/701.8 mAh g^-1 and the coulombic efficiency is 99.4%.?2?N,S co-doped carbon-based nanocomposites derived from L-methionine constructed MOFs for sodium storage.In this chapter,L-methionine is used as the organic ligand to complex with Co²⁺,Ni²⁺and Cu²⁺to obtain metal-methionine complex?M-met?,respectively.Then,a series of N,S co-doped carbon-coating transition metal sulfide composite materials were prepared through M-met one-step carbonization.The composite materials prepared by the method have an obvious sheet structure,and the sulfide nanoparticles are coated with clear amorphous carbon.Taking Co-met derived Co9S8@N,S-C as an example,we investigated its electrochemical performance as a negative electrode for sodium ion batteries,and studied the effect of different heat treatment temperatures on its electrochemical performance.The results show that Co9S8@N,S-C-600 has prominent cycle stability.After 150 cycles,the charge and discharge capacity reache to 594.2/614.9mAh g^-1,and the rate performance is excellent.?3?Synthesis and lithium storage performance of N,S co-doped carbon-coating MnO/MnS composites derived directly from MOFs.In this chapter,L-methionine is used as the organic ligand to complex with Mn²⁺to obtain a manganese-methionine complex?Mn-met?,and then one-step heat treatment prepared N,S co-doped carbon-coating MnO/MnS composite material.And it is used as a negative electrode material for lithium ion batteries.The research results show that the heat treatment temperature is the decisive factor affecting the phase,structure and electrochemical performance of the material.Among them,MnO/MnS@N,S-C-700 has the most outstanding electrochemical performance.After 500 cycles,the discharge specific capacity remains at 578.2 mAh g^-1,and the rate performance is excellent.