Abstract
The capacitance of Lithium-ion Capacitors (LiCs) highly depends on their terminal voltage. Previous research found that it varies in a nonlinear manner with respect to the voltage. However, none of them modeled the capacitance evolution while considering the physicochemical phenomena that happen in a LiC cell. This paper focuses on developing a new capacitance model that is based on the Stern model of the electrochemical double layer capacitance. The model accounts for the asymmetric V-shape of the C(V) curve, which reflects the variation of the capacitance with respect to the voltage. The novelty of this study concerns the development of a model for LiCs that relies on the fundamental theory of Stern for the differential capacitance. The basic model of Stern is modified in order to account for the hybrid physicochemical structure of LiCs. Moreover, the model was applied to three aged cells to which accelerated calendar aging tests were applied at three voltage values: 2.2, 3 and 3.8 V. A drift of the voltage corresponding to the minimum capacitance was detected for the aged cells. This voltage is related to the neutral state of the positive electrode. The main cause of this phenomenon concerns the loss of lithium ions from the negative electrode of a LiC. In addition, capacitance values decreased after aging, showing an eventual blocking of the pores of the positive electrode. Therefore, the analysis of the C(V) curve was found to be an interesting tool for the interpretation of aging mechanisms.
Highlights
Online monitoring of Energy Storage Systems (ESSs) relies on several tools such as the estimation of the current state of charge and state of health [1,2,3,4]
A Lithium-ion Capacitors (LiCs) that aged at 2.2 V and 70 °C for 20 months lost around 55% of its initial capacitance that be deintercalated from the negative electrode to accumulate on the surface of the positive electrode
The nonlinear capacitance evolution of LiCs was modeled based on a physicochemical analysis of the electrochemical double layer capacitance
Summary
Online monitoring of Energy Storage Systems (ESSs) relies on several tools such as the estimation of the current state of charge and state of health [1,2,3,4]. As a first step towards this goal, the amount of energy stored in the ESS should be assessed For this reason, capacitance estimation is an important factor to be studied [5,6]. In Supercapacitors (SCs), the storage of energy is based on the formation of an electrochemical double layer at the surface of two activated carbon electrodes [7,8]. This phenomenon induces the creation of the electrochemical double layer capacitance that was discovered and modeled by Helmholtz in
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
