| Due to the low abundance and uneven distribution of lithium resources,as well as safety issues,the future large-scale application of lithium-ion batteries have caused concerns.Therefore,to meet the ever-increasing energy demands,developing safe,low-cost and efficient new energy storage devices is imminent.Based on the unique anion-cation dual intercalation mechanism,dual-ion batteries show advantages of high output voltage and high energy density.Besides,their raw materials are widely sourced and low-cost,showing a great potential in the next generation of large-scale energy storage devices.The electrodes of dual-ion batteries usually use carbon-based materials.However,exfoliation of graphite anode usually occurs during cycling process,resulting a capacity decay and poor cycle life.Therefore,it is particularly critical to develop new anode materials with stable structure and high capacity.In this paper,aiming at the low capacity,poor cycling performance and severe self-discharge rate of traditional dual-carbon batteries,organic and sulfide anode materials are used,and the dual-ion batteries based on these anode materials are optimized and comprehensive investigated.The main research work is as follows:（1）5,7,12,14-pentacenetetraone is an organic compound with five benzene rings and four carbonyl groups arranged in a plane,connected by van der Waals force,showing conjugated stacked layered structure,which is beneficial to the migration of ions.Therefore,a graphite/5,7,12,14-pentacenetetraone dual-ion battery system with pure room temperature ionic liquid electrolyte is designed.The electrochemical performances of graphite/5,7,12,14-pentacenetetraone batteries under three ionic liquid electrolytes(Pyr14TFSI,PP14TFSI,and EMIm TFSI)are investigated,indicating that the batteries based on Pyr14TFSI ionic liquid exhibit best performances.The graphite/5,7,12,14-pentacenetetraone system achieves a high specific discharge capacity of～164.5 m A h g-1 at a rate of 0.1 C(1 C=317 m A h g-1).Besides,obtaining a good cycling performance at a high current density of 5 C for 100 cycles,keeping a good capacity retention of 92%.Furthermore,the self-discharge rate is 4.68%h-1,which is better than the conventional dual-carbon batteries.In addition,the working mechanism of this system is investigated by X-ray diffraction and X-ray photoelectron spectroscopy et al,confirming the redox reaction between the Pyr+14 and the four carbonyl groups of 5,7,12,14-pentacenetetraone during the charging and discharging process.（2）Due to the high cost of room temperature ionic liquids at present,and the large Pyr+14is difficult to achieve good intercalation of the anode,a high concentration electrolyte of 4 M Li TFSI is choose instead of pure ionic liquid electrolytes in this chapter.In addition,a two-dimensional layered material of tin disulfide（Sn S2）is prepared by a simple hydrothermal method.As a post transition metal dichalcogenide,Sn S2 shows a typical sandwich-like layered structure,with weak interlayer van der Waals forces and large interlayer spacing～0.59 nm（interlayer spacing of graphite is 0.335 nm）.A graphite/Sn S2dual-ion battery is constructed using Sn S2 as the negative electrode material,coupling with the graphite positive electrode and 4 M Li TFSI electrolyte.Besides,the performances of the graphite/Sn S2batteries in the different solvent systems are studied,and results reveal that the batteries based on the 4 M Li TFSI(Pyr14TFSI-EMC)system show the best performances.Under a current density of 100 m A g-1,the initial discharge specific capacity of battery could reach 114.3 m A h g-1.In addition,the system also exhibits an excellent rate performance with concentrated electrolyte,and the maximum discharge specific capacity can reach 66.3 m A g h-1 under the ultra-high current density of 2000 m A g-1.Notably,the self-discharge rate of graphite/Sn S2dual-ion battery is only 1.19%/h,showing a potential for practical application prospects.（3）In order to improve the electrical conductivity of Sn S2,and alleviate the volume expansion during cycling process,carbon nanofibers act as a basic skeleton,and polyvinylpyrrolidone（PVP）is used as the carbon source for carbon coating by pyrolysis.The（（Sn S-Sn S2）-NC-CF）anode material is prepared.The existence of Sn S-Sn S2 mixed phase in the composite material is proved by XRD and Raman characterization.In addition,graphite/（（Sn S-Sn S2）-NC-CF）exhibits excellent electrochemical performance,with an operating voltage range of up to 4.0 V.Besides,a high discharge specific capacity of 154.3m A h g-1 is achieved at a current density of 100 m A g-1,with an excellent Coulomb efficiency closing to 100%,obtaining a high-capacity retention of 81%after 100 cycles.In addition,long-term cycling performance of 2000 cycles were achieved at a high current density of 1000m A g-1.Furthermore,the batteries show excellent fast charge and slow discharge performance,reveal a great potential application in the field of fast charge batteries.（4）Flower-like tin disulfide(Sn S2)and molybdenum disulfide（Mo S2）heterojunction anode material is synthesized by a simple two-step solvothermal-hydrothermal method,and the conductive network of Sn S2-Mo S2 heterojunction is enhanced by carbon nanotubes doping.In addition,the free-standing graphite paper as the positive electrode avoids the use of current collector,and reduces the weight of the battery,which facilitates to improve the energy density.Benefiting from the flower-like（Sn S2-Mo S2）@CNTs heterojunction structure,which facilitates ion transport and provides space for volume expansion,graphite paper/（Sn S2-Mo S2）@CNTs dual-ion batteries exhibit excellent electrochemical performances.The battery achieves an ultra-high discharge specific capacity of～274.2 m A h g-1(current density at 100 m A g-1),and the capacity retention rate is as high as 95%after 300 cycles at400 m A g-1.In addition,the self-discharge rate is extremely low to 0.006%h-1,as well as an excellent fast charging and slow discharging performance,which could be a competitive large-scale application of energy storage devices in the future. |
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