锂离子电池是目前比较常见的二次储能器件，具有许多优良的电化学性质，其中

锂离子电池是目前比较常见的二次储能器件，具有许多优良的电化学性质，其中包括能量密度高、使用寿命长、可以快速充放电以及绿色安全等突出优点，因此也受到国内内外专家的广泛关注，并且希望能够进一步提高锂离子电池的电化学性能，扩大使用范围。同时，伴随着柔性电子工艺的迅猛发展，一大批柔性电子产品如：可卷屏手机、智能手环、植入式医疗器械等逐渐出现在大众的视野之中，那么如何制造出与柔性电子器件相匹配的柔性储能元件就显得十分重要。负极材料作为锂离子电池的一部分，其脱/嵌锂离子的数量和速度，会直接影响整个电池的电化学性能，因此我们对负极材料的研究和商业化生产一直非常重视。目前，在碳基负极材料中，石墨的应用最为广泛，它储量大、价格低、导电性好并且化学性质稳定，然而石墨电极的比容量只有372mAh/g，比较低，不能满足高功率、大容量的锂离子电池的要求。在锡基材料当中，二氧化锡（SnO2）的理论比容量比较高，为782mAh/g,而且安全环保，因此非常具有应用前景，然而这种材料在充/放电的循环过程中，其体积膨胀非常厉害(200%~300%)，电极材料的结构容易崩塌，致使电池的循环性能下降，所以在实际应用中都是将SnO2与其它材料复合使用。<br>针对以上情况，本文以SnO2为中心，分别将其与石墨、石墨烯、氧化石墨烯复合，并采用真空抽滤的方法，制作出柔性的锂离子电池薄膜。这样做一方面可以用SnO2来提高纯碳材料的比容量，另一方面也可以用碳材料减缓SnO2在充/放电循环过程中的强烈体积效应，研究内容如下：<br>（1）采用水热法制备SnO2/石墨复合材料，首先用简单真空抽滤的方式将材料抽滤成膜，但发现此方法不可行，随后便采用传统方式，先将材料制成浆料，然后用刮刀涂布的方法，制作柔性薄膜，并分析材料的性能；<br>（2）采用真空抽滤的方式制备纯石墨烯柔性薄膜，并测试材料的电化学性能；<br>(3) The SnO2 / graphene composite material is prepared by hydrothermal method, and the composite material is made into a flexible film by suction filtration, and then the film is characterized and tested to compare the existence of pure graphene flexible electrode and SnO2 / graphene flexible electrode And analyze the reasons; <br>(4) The SnO2 / graphene oxide composite material was prepared by hydrothermal method, and the film was made by vacuum suction filtration, and then the flexible film was characterized and tested to compare the film with SnO2 / graphene Differences in film properties and explain the reasons. <br><br>Keywords: lithium ion battery, flexibility, negative electrode material, graphene, electrochemical performance

Lithium-ion battery is a relatively common secondary energy storage device, with many excellent electrochemical properties, including high energy density, long service life, can be quickly charged and discharged and green safety and other outstanding advantages, so also by domestic and foreign experts, and hope to further improve the electrochemical performance of lithium-ion batteries, expand the scope of use. At the same time, with the rapid development of flexible electronic technology, a large number of flexible electronic products such as: roll-screen mobile phones, smart bracelets, implantable medical devices, etc. gradually appear in the public's field of vision, then how to create flexible energy storage elements to match the flexible electronic devices is very important. As a part of lithium-ion batteries, the number and speed of the de-embedded lithium ions directly affect the electrochemical properties of the entire battery, so we have always attached great importance to the research and commercial production of anegative materials. At present, graphite is the most widely used in carbon-based negative materials, it has large reserves, low price, good conductivity and stable chemical properties, but the graphite electrode ratio capacity is only 372mAh/g, relatively low, can not meet the requirements of high-power, high-capacity lithium-ion battery. In tin-based materials, tin dioxide (SnO2) is theoretically higher than capacity, 782mAh/g, and safe and environmentally friendly, so it has a very application prospect, however, the material in the charging/discharge cycle process, its volume expansion is very strong (200%-300%), the structure of the electrode material is easy to collapse, resulting in the battery cycle performance is reduced, so in practical applications are SnO2 and other materials composite use.<br>In view of the above situation, this paper takes SnO2 as the center, composites it with graphene, graphene and graphene oxide, and uses vacuum extraction to produce a flexible lithium-ion battery film. On the one hand, SnO2 can be used to increase the ratio capacity of pure carbon materials, on the other hand, carbon materials can also be used to reduce SnO2 in the charge/discharge cycle of the strong volume effect, the study is as follows:<br>(1) the use of hydrothermal preparation SnO2 / graphite composite materials, first with a simple vacuum filtration method to filter the material into a membrane, but found that this method is not feasible, and then the traditional way, first the material into slurry, and then with a scraper coating method, the production of flexible film, and analysis of the performance of the material;<br>(2) the use of vacuum extraction to prepare pure graphene flexible film, and test the electrochemical properties of the material;<br>(3) The hydrothermal method is used to prepare SnO2/graphene composite materials, and by pumping the composite material sifted into a flexible film, and then the film is characterized and tested, comparing the performance differences between pure graphene flexible electrode and SnO2/graphene flexible electrode, and analyzing the reasons;<br>(4) Using hydrothermal method to prepare SnO2/ graphene oxide composite materials, and vacuum filtration to make a film, and then the flexible film characterization and testing, compare the performance difference between the film and SnO2/graphene film, and explain the reason.<br><br>Keywords: lithium-ion battery, flexible, anegative material, graphene, electrochemical properties

Lithium-ion battery is a common secondary energy storage device, which has many excellent electrochemical properties, including high energy density, long service life, fast charge and discharge and green safety. Therefore, it is also widely concerned by experts at home and abroad, and hopes to further improve the electrochemical performance of lithium-ion battery and expand the scope of use. At the same time, with the rapid development of flexible electronic technology, a large number of flexible electronic products, such as rolling screen mobile phones, smart bracelets, implantable medical devices and so on, gradually appear in the public's vision. So how to make flexible energy storage components matching with flexible electronic devices is very important. As a part of lithium-ion battery, the number and speed of lithium-ion removal / insertion of anode materials will directly affect the electrochemical performance of the battery, so we have always attached great importance to the research and commercial production of anode materials. At present, graphite is widely used in carbon based anode materials, which has large reserves, low price, good conductivity and stable chemical properties. However, the specific capacity of graphite electrode is only 372mah / g, which is relatively low, and it can not meet the requirements of high-power and large capacity lithium-ion batteries. Among tin based materials, the theoretical specific capacity of SnO2 is relatively high, which is 782mah / g, Moreover, it is safe and environment-friendly, so it has a great application prospect. However, in the process of charge / discharge cycle, the volume expansion of this material is very strong (200% ~ 300%), the structure of electrode material is easy to collapse, which causes the cycle performance of the battery to decline, so in practical application, SnO2 is used in combination with other materials.<br>In view of the above situation, in this paper, SnO2 is taken as the center, which is compounded with graphite, graphene and graphene oxide respectively, and a flexible lithium-ion battery film is made by vacuum filtration. In this way, on the one hand, SnO2 can be used to improve the specific capacity of pure carbon materials, on the other hand, carbon materials can also be used to slow down the strong volume effect of SnO2 during the charge / discharge cycle. The research contents are as follows:<br>(1) SnO2 / graphite composite material was prepared by hydrothermal method. Firstly, the material was filtered into membrane by simple vacuum filtration method, but it was found that this method was not feasible. Then, the traditional method was adopted. Firstly, the material was made into slurry, then the flexible membrane was made by scraper coating method, and the properties of the material were analyzed;<br>(2) The graphene flexible film was prepared by vacuum filtration and its electrochemical properties were tested;<br>(3) SnO2 / graphene composite was prepared by hydrothermal method, and the composite was made into flexible film by suction filtration. Then the film was characterized and tested. The performance differences between pure graphene flexible electrode and SnO2 / graphene flexible electrode were compared, and the reasons were analyzed;<br>(4) SnO2 / graphene oxide composite was prepared by hydrothermal method, and the thin film was made by vacuum filtration. Then the flexible thin film was characterized and tested, and the performance difference between the thin film and SnO2 / graphene film was compared, and the reason was explained.<br>Key words: lithium ion battery, flexibility, anode material, graphene, electrochemical performance<br>