Graphite nanosheets are formed by exfoliating graphite with plasma, and the fine antimony sulfide (Sb2S3) is compounded on the nanographite sheet under the mechanical and thermal effects of ball milling to achieve high capacity and long cycle life antimony sulfide-graphite nano Design and preparation of composite negative electrode materials.
1. Preparation method
Anode material of Sb2S3-C composite lithium ion battery was prepared by plasma assisted ball mill
Put Sb2S3 and graphite into a ball mill jar at a mass ratio of 1: 1. At the same time, according to the ratio of 50: 1, the ball with 7mm size is added for ball milling for 6 hours to obtain Sb2S3-C composite anode material. At the same time, Sb2S3 composites with different ball milling times and different mass ratios were compared in the same way.
In the process of ball milling, graphite and mechanical ball milling are used to strip graphite in the direction of van der Waals force, so that graphite is stripped into graphite nanosheets efficiently and efficiently, and antimony sulfide particles are also refined into nano-scale particles. Further, the antimony sulfide particles are embedded in the graphite nanosheets under the impact of the grinding balls to form a Sb2S3-C composite material.
Original Sb2S3; (b), (c) SEM photographs of graphite nanosheets loaded with Sb2S3 particles; (d)-(i) TEM photographs and element distribution diagrams of graphite nanosheets loaded with Sb2S3 particles
Typical microstructure of Sb2S3-C. It can be seen that graphite is stacked in the form of nano graphite sheets. At the same time, the nano-scale antimony sulfide particles are evenly dispersed on the substrate of the nano-graphite sheet.
This structure of embedding antimony sulfide particles into nano-graphite sheets can effectively limit the volume change of antimony sulfide particles during lithium deintercalation, greatly improve the reversibility of antimony sulfide in the conversion reaction stage, and further improve antimony sulfide as a negative electrode material for lithium ion batteries Cycle performance.
2. Comparison of results
Sb2S3-C charge-discharge curve and capacity differential curve after simple and uniform mixing of antimony sulfide and graphite; Sb2S3-C charge-discharge curve and capacity differential curve after plasma ball mill
From the comparison of charge and discharge curves, it can be seen that the reversibility of Sb2S3-C after plasma ball milling has been significantly improved; further analysis of its capacity differential curve shows that Sb2S3 is refined to nanoscale and embedded in graphite nanoparticles by plasma ball milling After the film, the capacity retention rate of Sb2S3 in the alloying reaction and conversion reaction stage was significantly improved.
This is because the volume change of Sb2S3 embedded in the nano-graphite sheet during the circulation process is alleviated, so that the Sb / Li2S generated during the conversion reaction can react to generate Sb2S3 during the reverse conversion reaction. Therefore, Sb2S3- after plasma ball milling C has higher reversible capacity and cycle stability.
3. Conclusion analysis
The capacity of Sb2S3-C after plasma ball milling is still as high as 638.2mAh / g after 250 cycles, while the capacity of Sb2S3-C without ball milling is only 364.8mAh / g, and its capacity has been significantly improved; The rate performance of the latter Sb2S3-C has also been significantly improved.
After 500 cycles at a high current density of 1A / g, Sb2S3-C after plasma ball milling can still maintain a capacity of 498.3mAh / g, with a capacity retention rate of ~ 80%, achieving high-capacity long-cycle stability of the battery system Sex.
By further splitting the capacity contribution interval, it can be seen that Sb2S3-C after plasma ball milling can contribute a higher reversible capacity in both the alloying reaction and the conversion reaction. Compared with other Sb2S3-C work, plasma ball milling Sb2S3-C composite anode material has obvious advantages in capacity retention.
This is precisely because plasma ball milling strips graphite to form graphite nanosheets, and at the same time refines antimony sulfide into nanoparticles and embeds on the graphite sheets. By suppressing the volume change during the Sb2S3 cycle and suppressing the agglomeration of the active phase, Sb2S3 is structurally achieved in The stability in the cycle process finally achieved the high capacity and long cycle stability of the Sb2S3-C composite anode material.