Fabrication of Porous Electrodes with a Picosecond Pulsed Laser and Improvement of the Rate Performance of a Porous Graphite Anode and LiFePO₄Cathode

Abstract

To improve the rate performance of graphite anodes and lithium iron phosphate (LiFePO4) cathodes, micrometer-sized through-holes were formed on the electrode surface with a picosecond pulsed laser. The through-holes with 20 m diameters were uniformly arranged with an opening rate of 1%. Compared with that of non-porous electrodes, the discharge capacities of the porous anode and cathode electrodes did not degrade even at a high current density at a 10 C rate. The formation of through-holes on the electrodes provides a remarkable improvement in the rate performance by enhancing the ability of Li + ions to reach the active material surfaces.

An Improved High-rate Discharging Performance of “Unbalanced” LiFePO₄ Cathodes with Different LiFePO₄ Loadings by a Grid-patterned Micrometer Size-holed Electrode Structuring

“…17) is much smaller (20). This larger discharging capacity retention of the holed cathodes can be considered to reflect the fact that a facilitated transfer of Li + ions in the discharging process can occur through both the surface and the sidewalls (produced by forming the holes) of the LFP layer (or LFP/current collector layers), as found recently for the LFP/LFP cathode with the same LFP thickness on both side of a current collector [25][26][27] and the LFP/activated carbon (AC) cathode (in which the thicknesses of LFP and AC layers are different). 28 Table 1.…”

“…1) in which LFP layers were coated on both sides of an Al current collector foil were prepared using the same electrode materials and conditions as those reported in our previous papers. [25][26][27] The preparation is described in detail in the electric supporting information (SI). In order to prepare the LFP/LFP cathodes with different LFP loading amounts on both sides of the Al foil, the gap of a doctor-blade coater was suitably adjusted to prepare the LFP layers with different loading amounts, typically ca.…”

“…0.7-1.0, 1.9-2.1, 3.6-4 and 5.6-6 mg cm ¹2 (Table 1). Holing and characterization of these LFP/LFP cathodes was conducted using a picosecond pulsed laser as described previously [25][26][27][28] (see 1.2 and 1.3 in the SI). Table 1 lists 23 LFP/LFP cathodes examined in this study and hereafter the individual cathodes will be denoted as No.…”

“…[14][15][16][17][18][19][20][21][22][23][24] Recently, we have found that the formation of micrometer-sized holes on the cathodes, i.e., through-holed and non-through-holed cathodes provides a remarkable improvement in the high-rate charging/discharging performance due to the increased paths available in Li + ion transfer from/to the active materials (LFP and graphite layers). [25][26][27] In this study, we aim at clarifying the effect of a grid-patterned micrometer-sized cathode holing on the high-rate discharging performance of the LFP/LFP cathodes which are composed of LFP layer/Al current collector/LFP layer and have different LFP loading amounts (i.e., different capacities) on both sides of an Al current collector and thus will be called "unbalanced" LFP/LFP cathodes. The discharging rate-performance of three kinds of the unbalanced LFP/LFP cathodes, i.e., through-holed, nonthrough-holed and non-holed unbalanced cathodes ( Fig.…”

A Review: Pre‐lithiation Strategies Based on Cathode Sacrificial Lithium Salts for Lithium‐Ion Capacitors

“…To address the problem of slow rate and long time of pre‐lithiation, Tsuda et al. [ 116 ] optimized the above process by introducing a porous graphite anode with an opening area of 1% in 2016. Two types of graphite electrodes (a porous graphite anode with 1% opening area and an anode simply coated with graphite layer on the porous collector) were used to evaluate the dependence of lithiation rate on reaction temperature.…”