| Lithium-ion capacitors,lithium-ion batteries and so on have their own unique advantages in lithium-ion energy storage devices,which have become the research hotspot in chemical power source.The electrode material is an important part of the chemical power source.Graphene,as the positive material of lithium-ion capacitor and the additive of the electrode material of lithium-ion battery,and the oxide with special structure,as the negative material of lithium-ion battery,has been widely concerned and has a broad application prospect.The main research subjects of this paper are boron doped self-supporting graphene as the lithium-ion capacitor positive material,silicon-graphene composite as the lithium-ion battery negative material,hollow nano-Ti O2 and carbon-nitrogen co-doped core-shell porous nano-Ti O2 as the lithium-ion battery negative material,and graphene material as the dopant in lithium-ion battery material.These new electrode materials and their application in lithium-ion storage are explored.First,Graphene-based lithium-ion capacitor has been researched.Graphene as the the cathode in lithium ion capacitor,which is easy to cause the irreversible capacity loss in the long cycle process.The modification of graphene has become a research hot spot.Based on plasma enhanced chemical vapor deposition（PECVD）,which is used to dope boron into graphene in this paper.At room temperature,the mixture gas of diborane and hydrogen is used to glow under high frequency electric field to produce various kinds of active boron plasma（BHx,x=0-3）with different energy.It reacts with graphene electrodes with rich functional groups and 3D network space.By adjusting process conditions,the boron doped graphene electrode at the condition of room temperature,100 W glow power and 1 min glow time has the highest specific discharge capacity of140 m Ah g-1 and more than 99.6%of the coulomb efficiency,are higher than that of the pristine one by 28.9%.The composition of graphene and silicon materials as the negative electrode of lithium-ion battery is used to resolve the problem of volume change for silicon materials in the process of charge-discharge process.Based on the plasma enhanced chemical vapor deposition（PECVD）,silane and hydrogen as precursors are used to generate various silicon-containing active plasmas by glow discharge,which react with self-supporting graphene electrodes to prepare silicon-graphene composite electrode.By optimizing the process conditions,the results show that when the silicon content is 12nm,the first cycle discharge capacity of the Si graphene electrode is 30%higher than that of the pristine graphene electrode,and the capacity retention still exists 66.3%after the cycle is 350 cycles.Oxide negative electrode materials have important research significance in the safe lithium-ion batteries.Based on the method of template and high temperature calcination in air,the hollow porous nano-Ti O2 are prepared,which has rich specific surface and provides a lot of space for lithium storage.By optimizing the process conditions,the results show that the K30 PVP and PMMA microsphere templates at 600℃in air,could be obtain hollow porous nano-Ti O2,which has the best electrochemical performance,the specific discharge capacity is up to 165.7 m Ah g-1 and the capacity retention of 200cycles is up to 94.5%.Core-shell materials have important research significance in lithium-ion batteries due to their high stability.Based on the process of sol-gel,freeze-drying and high temperature calcination,a stabilized hybrid composite C-N@MP-Ti O2 with the core-shell structure is prepared,which takes the nitrogen doped carbon as the core and the uniformly distributed nano Ti O2 particles as the shell.By optimizing the process conditions,the hybrid composite C-N@MP-Ti O2 with the high specific surface area of318 m2 g-1 and average pore size of 6.8 nm were prepared.At the current density of0.1A g-1,the initial discharge capacity can reach 360 m Ah g-1.After 350 cycles,the capacity retention can reach 97%.At a current density of 5 A g-1,the capacity is still173.6 m Ah g-1,showing excellent rate performance;in addition,the reversible capacity can be achieved 172.2 m Ah g-1 under high current at 20 A g-1,and can cycle more than100 cycles for a long time.Graphene is used as additives,adding into the preparation process of the hybrid composite C-N@MP-Ti O2.After hydrothermal and high temperature calcination,the self-assembly of graphene are utilized to form continuous conductive network.By optimizing the preparation process,the specific discharge capacity of the composite reaches 212 m Ah g-1 at the current density of 5 Ag-1,and the cycle capacity retention of 300 cycles is almost 100%. |
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