Local State‐of‐Charge Mapping of Lithium‐Ion Battery Electrodes

Abstract

Current lithium‐ion battery technology is gearing towards meeting the robust demand of power and energy requirements for all‐electric transportation without compromising on the safety, performance, and cycle life. The state‐of‐charge (SOC) of a Li‐ion cell can be a macroscopic indicator of the state‐of‐health of the battery. The microscopic origin of the SOC relates to the local lithium content in individual electrode particles and the effective ability of Li‐ions to transport or shuttle between the redox couples through the cell geometric boundaries. Herein, micrometer‐resolved Raman mapping of a transition‐metal‐based oxide positive electrode, Li1‐x(NiyCozAl1‐y‐z)O2, maintained at different SOCs, is shown. An attempt has been made to link the underlying changes to the composition and structural integrity at the individual particle level. Furthermore, an SOC distribution at macroscopic length scale of the electrodes is presented.

Surface studies of high voltage lithium rich composition: Li1.2Mn0.525Ni0.175Co0.1O2

“…Additionally, the integral peak intensity ratio between E g and A 1g significantly changes from the pristine electrode to completely delithiated state, which is a spectroscopic signature of the local lithium concentration [32,33]. The sharpening of Raman band is associated with the decrease in the lattice disorder created by absence of lithium atoms in the interstitial layers during the delithiated or charged state [30]. Fig.…”

“…Raman spectroscopy is a powerful method for probing the chemical nature of the electrochemical interface in a Li-ion battery [30]. Fig.…”

Charge Heterogeneity and Surface Chemistry in Polycrystalline Cathode Materials

“…This is because they can lead to loss of capacity, local over-charge or over-discharge, or unsafe conditions (e.g., loss of oxygen in the case of transition metal oxides at high SOC). [19][20][21] Thus, understanding the formation mechanism of the non-uniformity is fundamentally interesting and practically important. To study heterogeneity at the particle level, it is useful to prepare samples by chemical delithiation using an oxidant such as NO2BF4 or Br2.…”

Thermal conductivity and internal temperature profiles of Li-ion secondary batteries

“…Performance and cycle life are also dependent on battery design [10,11], which will influence current distribution, state of charge (SOC), temperature and voltage distribution. This will influence local temperatures [12] and therefore, local degradation (ageing).…”