Electrochemical Kinetic Study of a Polyimide Anode for Lithium-Ion Batteries Using the AC Impedance Technique

Abstract

Electrochemical impedance spectroscopy (EIS) is selected as the main investigation method to study the underlying mechanisms and electrochemical kinetics of a polyimide anode material for lithium-ion batteries (LIBs) through obtaining the primary parameters of Ohmic impedance (R s ), solid-electrolyte-interphase (SEI) impedance (R f ), and charge-transfer resistance (R ct ). A typical polyimide (PNDA) anode material is synthesized using a simple one-step high-temperature polymerization method. The EIS spectrum of PNDA is fitted by two different equivalent circuit models. Charge-transfer activation energies before cycling and after the first cycle are 51.52 and 39.55 kJ mol −1 , respectively, implying a large energy barrier for the discharge of PNDA. The R ct and R f are the key factors influencing the electrochemical performance of PNDA. However, R s exhibits a slight effect on the total electrochemical kinetics. It shows a decreasing trend with increasing operation temperature, but this positive effect could be almost negligible compared to the kinetics of the total electrochemical processes of lithium embedding. The R ct drops significantly with increasing temperature, reflecting a strong dependence of the charge-transfer process on temperature. However, R f displays a noticeable increment with temperature, indicating that the SEI on the PNDA is slightly unstable with elevated temperature even below 80 °C. This value is also commonly regarded as the critical temperature for stable SEI on carbon and silicon anodes. The extent of decrease of R ct with increasing temperature is far greater than that of R f increment, resulting in enhanced total electrochemical kinetics of PNDA with temperature increase, thus enhancing its electrochemical properties at elevated temperature. These parameters of EIS reflect the rate-control step of the electrode-reaction processes and give an evaluation of the electrode-reaction processes. The revealed determining factors of polyimides as anode materials could provide useful insights for the development of high-performance organic electrode materials for LIBs.

Constitutional Isomer-Driven Free Volume Optimization in Polyimide-Based Anodes for Enhanced Capacity and Durability of Li-Ion Batteries

“…The XPS spectrum after the 500th cycle further indicated the effect of the free volume due to the different molecular orientations (Figure ). In the C 1s spectrum, a new peak appeared at 289.5 eV, corresponding to Li 2 CO 3 formation due to electrolyte degradation; similar peaks were observed at 54.5 and 531.0 eV in the O 1s and Li 1s spectra, respectively. ,, Nevertheless, the XPS spectra of PI-L, PI-B, and PI-C were similar, indicating that their chemical properties did not affect SEI layer formation. This further indicates that different free volumes of the PI anodes induce different SEI layer formations, thereby imparting distinct characteristics to Li + diffusion.…”

Application of N-Doped Carbon–Silicon Oxycarbide Based on POSS Synthesis in Lithium-Ion Batteries

“…The TGA and DSC curves of NSiOC (Figure S4) also show a 47.8% retention of the original mass, further indicating the approximate 50 wt % of N and C in the prepared NSiOC material. The existence of carbon coating and micropores could be beneficial in alleviating the volume expansion of silicon and the intercalation of lithium ions, − while nitrogen doping may enhance the conductivity of silicon-based composites and supply active sites by conjugating with the surrounding carbon atoms, which could in turn affect the performance of the thus-assembled LIBs. − …”

“…Figures S8 and illustrate the electrochemical performance of NSiOC integrated into coin cells. It can be widely recognized that the ion transport rate increases as the working temperature rises, which can affect the electrochemical performance of the materials. , However, the solvent dimethyl carbonate in the electrolyte may induce adverse effects and destroy the structure of the electrode material at high temperatures . Therefore, the typical maximum safe operating temperature for LIBs is about 60 °C.…”

Polyimides as Promising Materials for Lithium-Ion Batteries: A Review

“…After this extremum, the specific capacity began to decrease. Changing the repeat units of PIs, the reversible carbonyl reduction reactions and the “hyperlithiation” process will occur, whose process is also trapped by the work of Liao et al [ 112 ] in Fig. 13 b(i-iii).…”