A thick
electrode with high areal capacity is a straightforward
approach to maximize the energy density of batteries, but the development
of thick electrodes suffers from both fabrication challenges and electron/ion
transport limitations. In this work, a low-tortuosity LiFePO4 (LFP) electrode with ultrahigh loadings of active materials and
a highly efficient transport network was constructed by a facile and
scalable templated phase inversion method. The instant solidification
of polymers during phase inversion enables the fabrication of ultrathick
yet robust electrodes. The open and aligned microchannels with interconnected
porous walls provide direct and short ion transport pathways, while
the encapsulation of active materials in the carbon framework offers
a continuous pathway for electron transport. Benefiting from the structural
advantages, the ultrathick bilayer LiFePO4 electrodes (up
to 1.2 mm) demonstrate marked improvements in rate performance and
cycling stability under high areal loadings (up to 100 mg cm–2). Simulation and operando structural characterization
also reveal fast transport kinetics. Combined with the scalable fabrication,
our proposed strategy presents an effective alternative for designing
practical high energy/power density electrodes at low cost.
There is a growing need for thicker electrode designs to achieve high energy/power for ever-increasing power needs by electronic devices and electric automobiles. Though great efforts, such as structure optimization, have been devoted on fabricating thick electrodes, understanding of performance-limiting factors essential to electrode architecture design, has not been well established. In this study, the dependence of electrochemical behavior on electrode mass loading is comprehensively investigated in nanosheet-based electrodes. In particular, the effects of electrical conductivity and porosity are illustrated. In drop-casted electrodes, where nanosheets are highly stacked, ionic diffusion in the electrolyte has been determined to be the controlling step in electrodes with high thickness. To overcome the limitation of such sluggish ionic transport, a facile ice-templating strategy was employed to create vertically aligned channels, offering fast-diffusion pathways for the Li ion in the electrolyte. Impressively, the icetemplated electrodes exhibit a specific capacity of 144 mA h g −1 at 0.2 C and retain 83 mA h g −1 at 10 C with high mass loading ∼10 mg cm −2 . The enhanced ion transport kinetics was verified by various electrochemical and structural characterizations. This work demonstrates the thickness scaling effect of nanosheet-based electrodes and highlights the importance of promoting ionic transport and electrolyte access for designing thick electrodes.
Thick
electrodes, although promising toward high-energy battery
systems, suffer from restricted lithium-ion transport kinetics due
to prolonged diffusion lengths and tortuous transport pathways. Despite
the emerging low-tortuosity designs, capacity retention under higher
current densities is still limited. Herein, we employ a modified ice-templating
method to fabricate low-tortuosity porous electrodes with tunable
wall thickness and channel width and systematically investigate the
critical impacts of the fine structural parameters on the thick electrode
electrochemistry. While the porous electrodes with thick walls show
diminished capability under a C-rate larger than 1.5 C, those with
thinner walls could maintain ∼70% capacity under 2.5 C. The
superior capacity retention is ascribed to the fast diffusion into
the thin lamellar walls compared with their thicker counterparts.
This study provides deeper insights into structure-affected electrochemistry
and opens up new perspective of 3D porous architectural designs for
high-energy and high-power electrodes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.