Defects Graphene For Lithium-ion Batteries And Gas Sensors Applications

With the rapid development of portable electronic devices and further progressing ofresearch on automotive power battery,the updated secondary energy has been take a great attention because it has high energy density, long service life, low cost and environment-friendly features. At recent, it has many experimental worksto carry out on the field of anode materials.However, few theoretical researches focused on it. Therefore, in this paper, the mechanism of lithium inserting is analyzed by theoreticalcalculation. Through the establishment of calculation model, new electrode materials are designed. It is expected that thiswork could provide helpful information forthe design and fabrication of anode materials of LIBs.Carbon monoxide is colorless and odorless toxic gas, easy to bind with hemoglobin within bodies, thus hinder the combination of hemoglobin and oxygen, so that hypoxiawill occur to human bodies, causing poisoning accidents. In addition, carbon monoxide is dangerous combustible gas, because violent explosion may happen. On the other hand, carbon monoxide is widely applied in laboratories, industrial production, thus appears frequently in daily life. Therefore, fast accurate detection of carbon monoxide content in aircan guarantee the safety of people’s life and bring real economic benefits. So, researchers have been developing more reliable and accurate carbon monoxidesensors.In recent years, the first principlehas become an important means to studymicroscopic system. Compared with the empirical method, the first principle can help to realize the results more close to the reality. This principle can supplement our real experiment for fasterprediction of material performance with lower cost and can also offer help for design and development of new materials. In recent years, the first principle based on density functional theoryhas been widely used in many fields, especially in the fields of materials design and drug synthesis, thus it has become an indispensable tool for researchers.Currently, in view of the problems arising in application of graphene materials in the field of electrochemical sensor and lithium ion battery, the graphene materials are modified and optimized by means of element doping and surface structure design, and the electrochemical sensing and lithium battery performance are especiallyfocused on, followed bysome exploration of reaction principle. It is expected that this study will provideimportant theoretical and practical referencefor improving and controlling the application of graphene materials in the field of electrochemical sensors and lithium ion battery. This paper can be divided into the following parts:1. The pristine graphene was modeled to investigate the electrical and magnetic properties by first-principles stud. Based on this model, we investigated structural defects in graphene for the electromagnetic properties of materials. And then, we will be doped nitrogen on pristineand vacancy graphene. The results showed thatcompared with the structural vacancy graphene, the nitrogen-doped graphene material has a stronger chemical activity and special electronic properties. The atomic radius of both boron and nitrogen are similar with carbon atom, so we investigated boron doped graphene electrical and magnetic properties. The optimum doping concentration of boron through the study of the stability of different doping concentration graphene.2. Based on physical properties of defects graphene, it found that the presence of defects will enhance the chemical activity of graphene. Therefore, the interaction between the graphene’s surfaceand foreignmolecules is enhanced. The modified nitrogen graphene have great electrically negative which havemore effective to obtain electronic. Therefore, we studied the pristine graphene and nitrogen-doped graphene for the Lithium storage capacity, and its application on Lithium ion battery. The results showed that, compared with pristine graphene, the exits of defects does enhance the interaction between the lithium atoms and the graphene. The nitrogen doped defect graphene system is found that the lithium storage capacity and cycle performance for lithium ion battery have a further improved. The results show the reversible capacity of pyridine graphene can reach1262mAh/g.3. Using first-principles calculations, we investigated thatthe gas sensing performance of defects and nitrogen-doped graphene CO and NO. The results show that the defect can be effectively enhanced the graphene with CO and NO gas molecules interactions, but also enhanced the graphene on the adsorption energy of the molecules of O2in air. The purely defects graphene cannot identify CO and NO gas in the air, because of the strong interaction between the graphene on and O2molecules. Fortunately, only CO can be chemisorbed on NQ and other gas interaction with NG by physical adsorption. In addition, because the adsorption of gas molecule combines with the atoms nearly vacancy by forming a covalent bond with the lone pair electron, the magnetic moments of the system will be tended to vanish. The phenomenon makes sensor to detect CO by the magnetic method. In short, the pyridinic-like N-doped graphene is a very promising candidate for CO detection. It is expected that these results could provide helpful information in designing future toxic gases sensing devices.NO gas molecules adsorbed to the nitrogen-doped graphene NO will repair material defects on the surface, which will lead to decline in Original with paramagnetic defects graphene magnetic. While02adsorbed on the nitrogen-doped graphene, there is no significant chargetransfer, but the magnetic of the material has decline. Therefore, the nitrogen-doped graphene has the potential to become a magnetic sensor which can detect NO gas in the air environment.