title: Sustainable Materials for Energy Storage Devices
Creators: name: Ling, Han Yeu
Publisher: name: Griffith University
Year: 2021
Subjects: subject: Lithium-ion batteries
subject: Bio-derived materials

description: Bio-derived materials have attracted increased attention recently due to not only the sustainability, care-for-the-environment concerns, but also their naturally possessed unique structures, interesting mechanical properties, and abundant functional groups. These features endow them to potentially solve the issues that the next-generation high-capacity conversiontype lithium-ion batteries (LIBs) are facing, including but not limited to 1) great volume variation during charge/discharge for most conversion-type active materials (AMs), causing electrode pulverization, a phenomenon that active material particles are disassociated with the electrode and 2) serious shuttle effect brought by the dissolution of poly-intermediates into the electrolyte, leading to AMs loss, self-discharging, capacity fading, and shortened battery life. Bio-derived materials could provide strong binding forces and excellent mechanical strength to maintain the electrode integrity for high-capacity anodes, such as aluminum (Al) and silicon (Si) anodes. Meanwhile, Bio-derived materials possess abundant functional groups which could suppress the shuttle effect for high-capacity cathodes, such as lithium-iodine (Li-I2) batteries. These unique chemical, physical and mechanical properties of bio-derived materials make them promising in developing next-generation high-capacity LIBs. In the first study, aluminum with a high specific capacity, abundance, and electrical conductivity had been used as an active material to react with lithium ions and the electrical current collector simultaneously to save cost in the battery manufacturing process. However, its almost 100% volume variation will lead to serious electrode pulverization during lithiation/delithiation and reduce the cycle life of Al anode. Herein, a novel and robust biomassderived poly(furfuryl alcohol)/carbon black binder composite is prepared and applied on the surface of aluminum foil, and this hybrid Al anode had shown a superior 150 cycle life than unprotected Al anode that only can last for 25 cycles under a cut-off capacity loading of 400 mAhꞏg-1. This fast, quick, green, and low-cost method is potentially capable of solving the pulverization issue of high-capacity LIBs with minimal alternation on the existing battery manufacturing process. Instead of adopting complex and costly electrode structural modification methods, applying functional binders has the least impact on the existing LIBs fabrication process. Silicon has the highest theoretical capacity of 4200 mAhꞏg-1 but with an even more significant volume variation (~300%) than that of Al. Natural binders extracted from abundant plants provide effective strategies to solve the pulverization of silicon particles during charge/discharge processes. Green and abundant glutinous rice that had been used to build the Great Wall inspired the use of its main ingredient inside: amylopectin (AP). AP is a long and highly branched bio-polymer rich with carboxylic groups (-COOH) and hydroxyl groups (-OH), which can covalently bond with the SiOx on the Si nanoparticles. Also, its viscoelastic property allows it to accommodate the drastic volume variation of Si during charge/discharge. The asprepared Si-AP can uphold a high discharge capacity of 1517.9 mAhꞏg-1 at a rate of 0.1 C after 100 cycles, in which cycling stability is much higher than that of using traditional polyvinylidene fluoride (PVDF) and aqueous carboxymethylcellulose (CMC) binders. Okra, popularly known as Lady’s finger, is another commonly cultivated crop with a thick and slimy mucilage because of rich polysaccharides in it. It can be extracted and separated from the pods with a facile method and used as a binder, named okra gum (OG), showing great potential in addressing the volume variation of Si during lithiation/delithiation. Benefiting from its complex compositions and highly branched structure with rich hydroxyl groups, and viscoelastic properties, OG is able to form an interconnected network that bonds and holds the Si nanoparticles, conductive carbon, and the current collector. The as-prepared Si-OG electrode exhibits a discharge capacity of 1434 mAhꞏg-1 at a rate of 0.1 C after 50 cycles and is about 1.5 times greater than that of the Si-CMC electrode. These two studies suggest that bio-derived binder materials are able to construct more reliable LIBs with high-capacity, and both the extractions of AP and OG are greener, quicker, and cheaper than refined CMC binder. In contrast to famous lithium-sulfur (Li-S) batteries, lithium-iodine (Li-I2) batteries have also drawn great attention recently due to their high energy and power density, and iodine is low in cost and abundant. However, like Li-S batteries, Li-I2 batteries also suffer from the notorious shuttle effect, in which the dissolved iodine will leak from the cathode and diffuse to the lithium anodic side and cause self-discharge and eventually capacity fades. Here, an instant coffeederived heteroatom-rich honeycomb-like carbon filter is prepared to confine the dissolved iodine on the cathode region. In addition, this as-prepared bio-derived interlayer can bring Li-I2 battery with additional surface pseudo-capacity and results in a robust and highly reversible capacity of 224.5 mAhꞏg-1 at a rate of 10 C, and great capacity retention of 120.2 mAhꞏg-1 after 4,000 cycles. In summary, the explored bio-derived materials demonstrate the potential of solving the challenges that next-generation high-capacity lithium-ion batteries possess. Besides the facts that these materials are sustainable, green, and low cost, the extraction and electrode preparation processes are also beneficial to the environment and the operators. More importantly, these materials with environmentally friendly fabrication processes can be further developed into industrialized products for future high-capacity LIBs.