摘 要

SnO₂因其高的理论容量（1494 mAh g^-1）而被广泛研究，量子点因其大的比表面积，能提供更多的活性位点，被广泛应用到催化、吸附及能源储存。本课题利用量子点材料的优势，结合SnO₂与V₂O₃的协同效应以及石墨烯柔性特点，可控制备了SnO₂量子点/石墨烯、SnO₂量子点/V₂O₃纳米片复合结构。该结构由5 nm左右的SnO₂量子点均匀分布在石墨烯、V₂O₃纳米片表面组成，能够提供大的比表面积、高的反应活性位点以及优异的离子、电子传输，有助于锂离子电池性能的提升。进而组装成锂离子电池，进行电化学性能测试，探索其结构与性能的相关性。本课题在量子点纳米结构的设计方面具有极大的推进作用，并且该策略具有普适性，可应用到多个领域。

本文对锂离子电池负极材料进行了探索，测试并研究了SnO₂量子点/石墨烯、SnO₂量子点/V₂O₃纳米片复合材料的电化学性能，并取得了以下成果：

（1）结合低温溶剂热和烧结法成功地制备了SnO₂量子点/石墨烯、SnO₂量子点/V₂O₃纳米片复合材料。生长SnO₂量子点的方法具有推广性，并将这种方法推广至其它金属氧化物，如Cr₂O₃、Fe₃O₄等。

（2）采用XRD、SEM、TEM和BET等测试手段，表征SnO₂量子点/石墨烯、SnO₂量子点/V₂O₃纳米片复合材料的物相成分、形貌结构和比表面积等特性。测试结果表明在石墨烯表面，均匀生长着SnO₂量子点，尺寸大小在5 nm左右；该材料的比表面积高达148 m² g^-1；所测物相为纯相SnO₂。SnO₂量子点/V₂O₃纳米片复合材料的量子点尺寸大小在10 nm以下，均匀生长在V₂O₃纳米片表面。这种0D / 2D相结合的结构在设计和合成单分散量子点领域具有一定普适性。

（3）SnO₂量子点/石墨烯复合材料在电流密度为200 mA g^-1时，具有1385 mAh g^-1的初始容量，充放电循环120圈之后，仍具有1180 mAh g^-1的容量，相对于第二圈，容量保持率高达95%。在2000 mA g^-1的大电流密度下，循环1200次，仍具有700 mAh g^-1的容量。以上结果表明了SnO₂量子点/石墨烯复合材料具有优异的循环性能和高的可逆容量。SnO₂量子点/V₂O₃纳米片复合材料在500 mA g^-1的电流密度下，循环200圈之后，仍能保持920 mAh g^-1的容量；而且在1000 mA g^-1的大电流密度下，循环500圈之后，其容量为724 mAh g^-1，具有优异的循环稳定性和倍率性能。

关键词：SnO₂量子点，石墨烯，V₂O₃纳米片，锂离子电池

Abstract

SnO₂ has been extensively studied due to its high theoretical capacity, quantum dots are widely used for catalysis, adsorption and energy storage because of their large specific surface area to provide more active sites. In this thesis, we prepared SnO₂ quantum dots / graphene, SnO₂ quantum dots / V₂O₃ nanosheets composite structures by using the synergistic effect of SnO₂ and V₂O₃ and the flexibility of graphene. The SnO₂ quantum dots (5 nm) were uniformly distributed on the surface of graphene or V₂O₃ nanosheets, these architectures can provide large specific surface area, more active sites and excellent ion transport, which will be beneficial for lithium ion batteries. And then assembled into a battery, to explore structure and performance relevance. This topic has a great effect on the design of quantum dots nanostructures, and the strategy has wide universality and has potential in many other fields.

In this thesis, the research on the lithium ion anode materials was carried out, and the SnO₂ quantum dots / graphene, SnO₂ quantum dots / V₂O₃ nanosheets were fabricated as the lithium ion anode materials, and the following results are achieved:

(1) The SnO₂ quantum dots / graphene, SnO₂ quantum dots / V₂O₃ nanosheets composite structures were successfully prepared by solvothermal and sintering. The strategy of growing SnO₂ quantum dots was extended to other metals oxides such as Cr₂O₃, Fe₃O₄ and the like.

(2) The phase composition, morphology and specific surface area of SnO₂ quantum dots / graphene and SnO₂ quantum dots / V₂O₃ nanosheets were characterized by XRD, SEM, TEM and BET. The results show that SnO₂ quantum dots grow on the surface of graphene, and the size is about 5 nm, the specific surface area is 148 m² g^-1, SnO₂ quantum dots / graphene composite structure is pure phase SnO₂. About SnO₂ quantum dots / V₂O₃ composite structure, SnO₂ quantum dots (below 10 nm) grow uniformly on the surface of V₂O₃ nanosheets. This combination of 0D / 2D structures has some universality in the design and synthesis of monodisperse quantum dots.

(3) The initial discharge specific capacity of SnO₂ quantum dots / graphene composite structures was 1385 mAh g^-1 at 200 mA g^-1, and after 120 cycles, a capacity of 1180 mAh g^-1 can still be retained, which is 95% of the second-cycle discharge specific capacity. At a high rate of 2000 mA g^-1, there is still a capacity of 700 mAh g^-1 after 1200 cycles. The electrochemical performance test results show that the SnO₂ quantum dot / graphene composite structure has excellent cycling performance and rate capacity. SnO₂ quantum dots / V₂O₃ nanosheets composite structure, can deliver discharge specific capacity of 920 mAh g^-1 after 200 cycles at 500 mA g^-1. And at a high rate of 1000 mA g^-1, the capacity is 724 mAh g^-1 after 500 cycles, showing excellent cycle stability and rate capability.

Key words: SnO₂ quantum dots, graphene, V₂O₃ nanosheets, lithium ion batteries

目 录

摘 要 I

Abstract II

第1章 绪论 1

1.1 引言 1

1.2 锂离子电池及其负极材料 1

1.2.1 电池结构及工作原理 1

1.2.2 锂离子电池负极材料的研究进展 2

1.3 二氧化锡纳米材料的发展现状 4

1.4 本文研究内容及意义 7