Electrode Suspensions With Tailored Flow Behavior and Electrochemical Performance for Multiscale Lithium Ion Batteries

Abstract

Rechargeable Li-ion batteries (LIBs) are widely used in applications ranging from portable electronics to electric vehicles. They are also being explored for grid-scale energy storage. To date, commercial LIBs have been confined to coin, cylinder, prismatic and pouch cells, which are composed of thin electrode layers (20-100 μm thick). However, the growing demand for LIBs with higher capacity, faster charge-discharge rates, lower cost, and customized form factors underscores the need for new electrode materials, battery architectures, and fabrication methods. My Ph.D. dissertation focuses on fabricating high energy density Li-ion batteries with ultrathick (up to 1.5 mm), biphasic, semisolid electrodes for use in applications ranging from customized Li-ion microbatteries to semisolid flow cells. As an initial demonstration, we printed Li-ion microbatteries (< 1 mm3 in volume) in the form of interdigitated, high aspect ratio LFP/LTO electrodes on patterned gold current collectors, which deliver an areal capacity of ~1.5 mAh cm-2 at a discharge rate below 5C. To improve their electronic transport and area capacity, we created biphasic semisolid electrode inks that are electrolyte-infused for printing LIBs with ultrathick electrodes (~ 1 mm). Specifically, the interactions between the active particles, LFP or LTO, are rendered repulsive, while those between the conductive carbon particles are attractive. Our biphasic ink design enables high solids loading of active materials within a percolative network of conductive carbon particles, which gives rise to electrodes that simultaneously exhibit good flowability, charge transport, and high energy density. These fully 3D printed and packaged LIBs exhibit an areal capacity more than an order of magnitude higher than the micro-LIBs with exceptional cycling performance. As a final demonstration, we used these biphasic electrode suspensions in semisolid flow batteries. Their quick and efficient charge transport reduces overpotential during cell cycling using 1.5 mm thick semisolid electrodes. Based on these measured properties, we also developed an analytical model that predicts the pressure drop required for a given target current. These efficient and scalable biphasic semisolid flow cells offer a promising approach for grid-scale energy storage.