Conversion of lignin into dielectric materials for renewable energy storage

在过去的一个世纪里，人类文明严重依赖化石燃料，使大气中的二氧化碳浓度增加了约40%。大气中二氧化碳浓度高往往会捕获增加的红外辐射（即温室效应），从而导致全球变暖。这反过来又导致了一连串的气象灾害。因此，在过去的几十年里，研究人员一直在积极寻找替代能源，其中太阳能和风能越来越受欢迎。然而，由于太阳能和风能发电的间歇性，及时开发相应的储能技术也至关重要。******有两种类型的能量存储设备电容器和电池。一般来说，电容器具有高功率密度而低能量密度，而电池具有相反的特性。这里，功率密度表示存储设备传输能量的速度，而能量密度表示设备每单位体积存储的能量。这就是为什么电容器往往用于短期，而电池用于长期存储。商用电容器通常使用介电材料，如陶瓷，以增加其存储容量。近年来，聚合物基电介质因其重量轻、柔韧性好、易于制造等优点而受到越来越多的关注。此外，聚合物电介质还具有高击穿强度，这对于理想的电容器性能（即即使在高电场（电压）下也能保持介电性能的能力）至关重要。然而，聚合物基电介质的缺点是能量密度低。******为了增加聚合物介质的能量密度，需要增加它们的相对介电常数（即聚合物相对于真空的介电常数），也称为介电常数。一般来说，含有更容易极化的官能团的聚合物表现出更高的相对介电常数。作为纸浆和造纸工业的副产品，木质素是第二丰富的生物质，其结构属性（苯基、酚和羟基的丰富存在）非常适合转化为电介质材料。随着现代合成化学的发展，更强大的工具可以将木质素转化为具有特殊调节介电性能的交联聚合物材料。由于木质素是一种工业废物，成功地将木质素转化为拟议的增值材料不仅有利于环境（使用可再生材料储存可再生能源），而且还提供了经济激励。该项目的主要目标是使用木质素作为前体，制备具有所需介电性能的廉价、环保材料，可用于高功率密度和高能量密度电容器。

Human civilization, with its heavy reliance on fossil fuels over the past century, has increased the concentration of atmospheric CO2 up about 40%. High atmospheric CO2 concentration tends to trap increased amount of infrared radiation (i.e., greenhouse effect) resulting in global warming. This in turn leads to a cascade of many meteorological disasters. Therefore, over the past few decades, researchers have been actively searching for alternative energy sources, among which solar and wind energy is gaining increasing popularity. However, owing the intermittent nature of solar and wind energy generation, it is also vitally important to develop the corresponding energy storage technologies in time. ******There are two types of energy storage devices capacitors and batteries. In general, capacitors exhibit high power density but low energy density while batteries have the opposite properties. Here, power density signifies how fast a storage device can deliver energy while energy density the amount of energy stored per unit volume of the device. That is why capacitors tend to be used for short-term while batteries for long-term storages. Commercial capacitors normally use dielectric materials, such as ceramics, to increase their storage capacity. Recently, polymer-based dielectrics are gaining more attention, as they are lightweight, flexible and easy to fabricate. In addition, polymer dielectrics are also known to possess high breakdown strength, which is vital for ideal capacitor performance (i.e., the ability to maintain dielectric properties even under high electric field (voltage)). However, the drawback of polymer-based dielectrics is their low energy density.******To increase the energy density of polymer dielectrics, one needs to increase their relative permittivity (i.e., permittivity of the polymer relative to that of vacuum), also known as dielectric constant. In general, polymers containing functional groups that are easier to be polarized exhibit higher relative permittivity. Generated as a byproduct in the pulp and paper industry, lignin, the second most abundant biomass, contains the structural attributes (a rich presence of phenyl, phenol and hydroxyl groups) that are ideal to be transformed into dielectric materials. With the development of modern synthetic chemistry, more powerful tools have become available to convert lignin into cross-linked polymeric materials with specifically tuned dielectric properties. Since lignin is an industrial waste, the successful conversion of lignin to the proposed value-added materials not only benefits the environment (use of a renewable material to store renewable energy) but also offers economic incentives. The primary goal for this project is to use lignin as a precursor to prepare inexpensive, ecofriendly materials with the desired dielectric properties that can be used in high power density and high energy density capacitors.