Functional Biopolymer Binders for High-Energy-Density and Ultrafast Cycling Lithium-Ion Batteries Operating at Extreme Temperatures (BLISET)

锂离子电池于1991年首次商业化，并立即取得成功。近30年后，这种成功并没有消失，对高能量密度和长循环寿命的可充电电池的需求只会增加。除了高能量密度和长循环寿命之外，还需要安全性、可持续性、成本效益、高倍率能力和宽温度范围操作。这种强烈的愿望是全球性的。无论是在夏季的巴西还是冬季的西伯利亚，电池都有望在全球范围内提供出色的性能。为了实现这一目标，以前的方法包括优化活性材料。然而，这条道路正在达到极限，因此，注意力已转向电池的其他组件。电池的关键成分之一是粘合剂，它负责均匀分散和连接组成电极的颗粒（活性材料和导电碳），以确保对集电器的牢固持久的粘附力，并有助于锂离子的更快扩散。在该项目中，目的是开发一种更环保的电极制造工艺，通过改善粘合剂的机械，热和导电性能来提高倍率性能并扩展锂离子电池的工作温度范围。为了达到这些目标，将研究基于生物聚合物的新型粘合剂。除了生物聚合物之外，这种新型粘合剂（凝胶粘合剂）还包含离子液体和锂盐。这三种组分的组合导致离子电导率、机械完整性和热稳定性的改善，并有助于形成导电网络。因此，由于快速的电荷转移动力学和较短的锂离子扩散路径，活性材料被充分利用。总体而言，锂离子电池具有高能量密度，长循环寿命（2000 - 3000次循环）和极高的倍率性能（至少高达10C，1000次循环，对应于6分钟内电池充满电）。粘合剂组合物的优化和众所周知的活性材料的使用将实现这一目标。将通过傅里叶变换红外光谱（FTIR）、X射线衍射（XRD）、扫描电子显微镜（SEM）、X射线光电子能谱（XPS）、拉伸试验、电解质吸收测量和热重分析（TGA），对整个项目中制备的样品的结构、形态、机械和热性能进行评价。而电化学表征将通过原位光谱电化学、恒电流循环（GCPL）、电化学阻抗谱（EIS）和循环伏安法进行，不仅在室温（25 º C）下，而且在非常低的温度（-30 °C）和高温（60 ° C）下也是如此。

Lithium-ion (Li-ion) batteries were first commercialized in 1991 and were an immediate success. Almost thirty years later, that success has not faded and the demand for rechargeable batteries with high-energy-density and long cycle life has only increased. In addition to high-energy-density and long cycle life, safety, sustainability, cost-efficiency, high rate capability and wide temperature range operation are also required. The urge is strong and global. Batteries are expected to deliver great performance worldwide no matter if they are used in summery Brazil or wintry Siberia.In order to attain such goals, previous approaches included the optimization of the active material. However, that path is reaching its limit and, thus, attention has been turned to other components of batteries. One of the key component of batteries is the binder, which is responsible for homogenously dispersing and connecting the particles (active material and conductive carbon) that compose electrodes, to ensure a strong and long-lasting adhesion to the current collector, and to contribute to a faster diffusion of lithium ions. In this project, the aim is to develop a more environmentally friendly electrode manufacturing process, improve the rate capability and extend the operating temperature range of Li-ion batteries by improving the binder’s mechanical, thermal and conductive properties. To reach these goals a new type of binder based on biopolymers will be investigated. Besides the biopolymer, this new binder, a gel binder, also comprises an ionic liquid and a lithium salt. The combination of these three components leads to an improvement of the ionic conductivity, mechanical integrity and thermal stability and helps to create a conductive network. Thus, the active materials are fully utilized as a result of fast charge transfer kinetics and shorter lithium ion diffusion paths.Overall, Li-ion batteries with high-energy-density, long cycle life (2000-3000 cycles) and very high rate-capability (at least up to 10C for 1000 cycles, corresponding to a full battery charge in 6 minutes) in a wide range of temperatures (between -30 and 60 ºC) are intended. The optimization of the binder composition and the use of well-known active materials will grant this objective. The structural, morphological, mechanical and thermal properties of the samples prepared throughout this project will be evaluated by means of Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), tensile testing, electrolyte uptake measurements and thermogravimetric analysis (TGA), while the electrochemical characterization will be carried out through in situ spectroelectrochemistry, galvanostatic cycling (GCPL), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry not only at room temperature (25 ºC), but also at very low (-30 ºC) and high temperatures (60 ºC).