New approaches to the lithiation kinetics in reaction-limited battery electrodes through electrochemical impedance spectroscopy

Abstract

Electrochemical impedance spectroscopy is a widely employed technique probing kinetic limitations in the charging of battery electrodes. Hindrance mechanisms locate at the interfaces between the active material and the electrolyte, and in the bulk of the reacting compound. Rate-limiting mechanisms are viewed as resistive circuit elements and can be extracted by standard impedance analyzers. Classical impedance models consider charge transport, mainly ion diffusion as slower carrier, as the principal kinetic limitation impeding full electrode charging. This is indeed the case for many technologically relevant battery compounds. In other instances, instead of being diffusion-limited, electrodes may undergo charging limitation caused by the kinetics of the reduction reaction itself. Specific impedance models for reaction-limited mechanisms are summarized here and proved for relevant electrode compounds, in particular for conversion or alloying electrodes in which Li + intake produces a full rearrangement of the lattice structure with significant atomic displacement.

A Self‐Healing Room‐Temperature Liquid‐Metal Anode for Alkali‐Ion Batteries

“…The fast diffusion agrees with observed performance under large current density. Based on the EIS curves, the SEI layer has a significant contribution to the impedance showing on the semicircle at the medium‐frequency . It is not surprising that Na ions diffuse slower in the system because of the larger ionic radius and a more sluggish electrochemical kinetics.…”

Synergistic Interactions of Different Electroactive Components for Superior Lithium Storage Performance

“…The straight line in the low-frequency region indicates the mass transfer of Li ions . Owing to the enhanced electrical conductivity of lithiated negative electrodes, higher R SEI than R ct was shown in both samples . Interestingly, ZSO@NiO NFs displayed highly suppressed R SEI and R ct compared with ZSO NFs, which reveal that the functional surficial NiO layer improved electrical conductivity and formed a stable SEI layer, resulting in better rate capabilities and durable cycle stability compared with noncoated ZSO NFs.…”

“…Interestingly, ZSO@NiO@G NFs exhibited even higher reversible capacity than ZSO@NiO NFs and showed excellent cyclability even after 1600 cycles, which is the most excellent value (1161 mAh g –1 at a current density of 1000 mA g –1 ) among previously reported mixed transition metal oxide (stannates, molybdates, cobaltates, ferrites, and manganates) based electrodes (Figure d). − The in situ galvanostatic EIS results of the ZSO@NiO@G NFs further supported both the excellent rate capability and cycle stability (Figure ). Generally, R ct is dependent on the electrical conductivity of host materials, since conductive hosts can facilitate Li ion transport to overcome the potential barrier appearing at the electrolyte/active material interface . As can be seen in Figure a,b, ZSO@NiO@G NFs displayed mostly lower R ct compared with ZSO@NiO at a different state of charge (SOC) during lithiation and depth of discharge (DOD) during the delithiation process, indicating a key role of the rGO sheets in favoring the interfacial Li ions intake from the electrolyte to ZSO@NiO NFs.…”

Liquid Alloy Enabled Solid‐State Batteries for Conformal Electrode–Electrolyte Interfaces

“…As Figure 2f shows, the interfacial resistance that is reflected by the charge-transport resistance R ct in an equivalent circuit of the electrochemical impedance spectroscopy (EIS) test differs obviously by electrodes with the same electrolyte. [42] Among three types of anodes, the Na-K anode shows much smaller charge-transfer resistance than both Na or K metal anodes at room temperature, which indicates the best electrical contact between the LM electrode and electrolyte. Between two metal species, the K metal shows lower interfacial resistance with the polymer electrolyte than the Na metal, which is possibly due to the intrinsically lower stiffness of K metal (shear modulus G Na = 3.3 Gpa, G K = 1.3 GPa), as well as the much smaller particle size of SiO 2 nanoparticles in K-ion SPE than NASICON particles in Na-ion SPE that leads to uniform SPE morphology.…”