Characterization of the Depth of Discharge-Dependent Charge Transfer Resistance of a Single LiFePO₄ Particle

Abstract

The discharged state affects the charge transfer resistance of lithium-ion secondary batteries (LIBs), which is referred to as the depth of discharge (DOD). To understand the intrinsic charge/discharge property of LIBs, the DOD-dependent charge transfer resistance at the solid–liquid interface is required. However, in a general composite electrode, the conductive additive and organic polymeric binder are unevenly distributed, resulting in a complicated electron conduction/ion conduction path. As a result, estimating the DOD-dependent rate-determining factor of LIBs is difficult. In contrast, in micro/nanoscale electrochemical measurements, the primary or secondary particle is evaluated without using a conductive additive and providing an ideal mass transport condition. To control the DOD state of a single LiFePO4 active material and evaluate the DOD-dependent charge transfer kinetic parameters, we use scanning electrochemical cell microscopy (SECCM), which uses a micropipette to form an electrochemical cell on a sample surface. The difference in charge transfer resistance at the solid–liquid interface depending on the DOD state and electrolyte solution could be confirmed using SECCM.

The New Era of High-Throughput Nanoelectrochemistry

“…Finally, the charge transfer resistance on individual LFP particles was quantified, as a model system for exploring battery charging/discharging at high rate. 322 The results affirmed the significance of discharge level and electrolyte solution type (aqueous vs organic solvent here).…”

“…SECCM/SHINERS coupling sheds light onto the stages of a continuously evolving SEI through tweaking the number of cycles and potential cycling range. Finally, the charge transfer resistance on individual LFP particles was quantified, as a model system for exploring battery charging/discharging at high rate . The results affirmed the significance of discharge level and electrolyte solution type (aqueous vs organic solvent here).…”

The new era of high throughput nanoelectrochemistry

“…Finally, the charge transfer resistance on individual LFP particles was quantified, as a model system for exploring battery charging/discharging at high rate. 323 The results affirmed the significance of discharge level and electrolyte solution type (aqueous vs organic solvent here).…”

Direct measurements of size-independent lithium diffusion and reaction times in individual polycrystalline battery particles

“…S10). The number of particles we quantify in this experiment with high reliability and robustness is much greater than past single-particle electrochemistry studies which only investigate one or a few particles 6,7,10,[21][22][23][24][25] ; as we show in the next section, this larger data set is essential in statistically uncovering unexpected mechanisms.…”

“…Inspired by the field of neuroscience 20 , we designed and developed a multi-electrode array that enables high-throughput electrochemical cycling of many individual battery particles. In contrast to previous works using microneedle contacts 6,7,10,21,22 or scanning micropipettes [23][24][25] with limited numbers of particles analyzed, we conduct full electrochemical cycling and analysis on over 20 individual particles under identical conditions. We thereby generate a statistically significant dataset on reaction and diffusion times for many particles.…”