Quantum view of Li-ion high mobility at carbon-coated cathode interfaces

A Positron Implantation Profile Estimation Approach for the PALS Study of Battery Materials

“…In this work, we demonstrated a distinctive application of PAS in parallel with BES as complementary techniques in interfacial characterizations of the electronic and ionic conductivity of functional energy materials. With sufficiently large statistics collected in each measurement (∼ 4•10 6 events in our case), positrons as a quantum analogue of Li-ions, can be used to probe the Li-ion dynamics at the LCO/carbon interface [4]. Various computer programs have been developed for analyzing the positron lifetime by deconvolution of the spectra.…”

“…In this section, the use of the positron implantation profile and source contribution estimation method in our study [4] of the effect of carbon coating on Li + ion mobility in LCO cathodes is demonstrated as an example of the profile analysis with multilayer configurations.…”

“…This spurious component usually has a very low intensity depending on the surface porosity of the material, which is measured to be approximately 0.2-0.4% in our case of the Kapton/LCO interface (see Refs. [2,4] for more details). After subtraction of the source and spurious components, the remaining fraction of the implanted positrons is normalized to unity in the analysis.…”

“…A Schottky or ohmic junction can be formed at the carbon/LCO interface due to the different work functions of the conductive carbon and the semi-conductive LCO, resulting in the negative charges in the LCO grain migrating into the carbon layer and a depletion region on the LCO side. The negative charges locally populated at the carbon/LCO interface create an intrinsic Coulomb field attractive to boost the diffusions of positively charged positrons and Li-ions from the LCO grains into the carbon layer [4]. The BES results of D Li + (in Table 3) indicate that at the same applied external field, Li-ion diffusion in the NT cathode is approximately 4-fold higher than that of the No C cathode attributing to the attractive field created at the carbon/LCO interface.…”

“…As the demand for high performing Li-ion batteries is emerging at a swift pace, conventional cathode materials having a low Li-ion mobility through the microstructure are facing the challenge to fulfil the desired charging-discharging characteristics. Two effective strategies for improving the battery charging efficiency and rate capability are downsizing the grains of the nanostructured active material and coating the active nanoparticles with a conductive carbon layer [4,5]. Battery cathodes with downsized nanograins allow Liion dynamics through the structure in a shorter pathway, and hence improve the rate capability performance.…”