We further investigated the physical reason for the improvement. As a contrast, the BT dual-gradient type even shows worse charging performance than single-gradient type (fig. The simulated charging curve at 3.75 mA cm −2 indicated that the ST dual gradient could improve the fast-charging performance notable (fig. Two opposite particle size distributions are constructed. However, the improvement is not evident, and then, to further improve the charging performance, gradient distribution of different sized particles is introduced into single-gradient–type structure named dual-gradient type. S1E, when the electrodes were charged to the cutoff voltage (0 V versus Li +/Li), the single-gradient type exhibited higher utilization and lower overpotential. The charging process at high current density of 3.75 mA cm −2 (the theoretical areal capacity of the electrode is 7.5 mAh cm −2) is simulated to investigate the charging performance of the proposed electrode structures. First, a gradient porosity structure with higher porosity on the top than the bottom, which is referred to single-gradient type, is constructed to compare with the electrode having randomly distributed porosity (random type) ( 23). Given the thick electrode with fixed overall porosity (35%) containing randomly distributed particles, we design the spatial distribution of the porosity. RESULTS Particle-level theoretical model to optimize the thick electrode structureĪ two-step iterative design method is used to optimize the electrode structure in the simulation(detailed electrochemical simulation process in the Supplementary Materials) ( 29– 39). More than that, less experimental investigation has been carried out to verify the performance improvement related to the electrode structural design. The real electrode design of particle size distribution and porosity distribution calls for microstructure-resolved models to overcome the trade-off between the energy density and fast-charging performance of the LIBs ( 28).

However, we found that the critical microstructure parameters, average particle size, and electrode porosity have only been individually considered in previously reported pseudo–two-dimensional (P2D) models to reduce the electrode polarization effect ( 23, 25– 27). To acquire high mass transport of Li + ions and reduce the concentration polarization in the graphite anode, microstructure optimization of the electrode is a promising route ( 23, 24). The polarization effect in the graphite anode is mainly attributed to the concentration polarization of Li + ion in the whole electrolyte ( 19– 22). In practical graphite anode with required energy density (porosity 70 μm), there is a detrimental polarization effect ( 17, 18) during the fast-charging process leading to the lithium metal plating on the surface of the electrode. Therefore, up to now, it is still very challenging to overcome the trade-off between the energy density and fast-charging performance of the LIBs. Nevertheless, all these reported graphite anodes behaved with limited electrode parameters such as low graphite mass loading, high porosity, and low thickness, which largely sacrificed the energy density of the fabricated LIBs ( 12). In the past decades, porous graphite particle ( 7), solid electrolyte interphase modification on the graphite ( 8), and the aligned graphite via magnetic field ( 9) have been reported to improve the rate performance of the graphite anode ( 7– 16). The fast-charging capability of the LIB at the material level is limited by the sluggish reaction kinetics and the low equilibrium potential (within 100 mV versus Li +/Li) ( 4) of the graphite anode, which tend to induce the metallic lithium plating under a high charging rate ( 5, 6). Department of Energy has recently proposed a fast-charging goal of 10 miles min −1 for the EV ( 3).

In this scenario, building up extremely fast-charging LIB system is highly desirable, and the U.S. However, much longer recharging time of the EV than the gas-refilling time of traditional fuel vehicle makes it much less competitive ( 2). Electric vehicle (EV) powered by the lithium ion battery (LIB) is one of the promising zero-emission transportation tools to address air pollution and energy crisis issues ( 1).

Lithium ion batteries