Energy storage systems play critical roles in modern society due to the increasing demand for electrical power supply for devices such as mobile electronic devices and electric vehicles as well as the need to provide reliable energy supply generated by renewable energy for the general household. The structure of a typical battery or supercapacitor consists of current collector/ cathode/ electrolyte/ membrane/ anode/current collector. Our researches are focus on three areas:
Innovative electrolyte materials for batteries
To address the safety issues of batteries using conventional liquid electrolyte, we have designed and synthesized a series of solid-state electrolyte materials made from lithium iodide (LiI) and a small molecular 3-hydropropionitril (HPN). We have investigated the mechanism of ion conductivity of the electrolyte. Our research has shown that the conductivity of the material can be switched from an iodide -conductor to a lithium ion-conductor by tuning the composition of the LiI-HPN binary material system. We further developed various methods that can effectively increase conductivity of the solid-state electrolyte. The work has led to 6 publication in top-tier journals including J. Am. Chem. Soc. (2005, 127, 6394-6401), Angew. Chem. Int. Ed (2023, 62, e202305004). In addition, our deep understanding of the theoretical predication of material properties-structure relationship has led to the publication of seminal review article in Progress in Materials Science (2022, 133, 101055).
Efficient membrane coating for lithium-sulphur batteries
The increasing demand for energy for portable electronic devices and electrical vehicles requires development of new batteries beyond lithium-ion batteries. Lithium-sulphur (Li-S) batteries are considered as one of the promising next generation batteries that can provide high energy density using readable available materials. Nevertheless, the shuttling effect of polusulfide in Li-S batteries has caused unsatisfactory device performance and stability.
To address this issue, our research has been focus on designing of new membrane coating that can hinder or eliminate cross-over of polysulfides, increasing the device performance. We have successfully designed a series of coating materials with controlled porosity and selective transport for ions based on metal organic framework (MOF) and ionic covalent organic frameworks (COF). Application of these materials as membrane coating in Li-S batteries has led to remarkable enhancement of the device performance and cycling stability.
Electrochemical capacitors also called supercapacitors (SCs) is a complimentary energy storage system to batteries. SCs possess distinguished merit including superior energy density than conventional capacitors and higher power density than batteries. To date, carbon based electrode materials have been used in commercial SC devices and has demonstrated high power density, enabling them very useful in certain areas such as high speed train and power for energy gate of air plane. However the limited energy density of carbon has restricted the application of the supercapacitors in a broader area which requires large amount of energy. Our research has been focus on development of strategies for supercapacitors with ultimate goals of achieving SCs with high energy density while maintaining their power density and cycling stability __ work include
- new electrode materials with tailored nanostructures using transition metal compounds and
- new device design by using the redox chemistry of anions of the electrolytes.