Measurements of Electric Performance and Impedance of a 75 Ah NMC Lithium Battery Module

Abstract

Detailed characterization of battery modules is necessary to construct reliable models that incorporate performance related aspects of the modules such as thermodynamics, electrochemical reaction kinetics and degradation mechanisms. Charge-discharge curves, temperature and battery impedance measurements can provide information about these aspects. Charge-discharge curves can be used to measure the battery open circuit voltage and the internal resistance. Temperature measurements provide information about the thermodynamic reactions and impedance spectra yield detailed information about the reaction kinetics. In this paper we present the measurement methods used to examine the internal resistance, the capacity and the impedance of a 75 Ah NMC battery module. In order to measure the impedance of the battery module and of the individual cells in the module, we combine the single sine technique and the Laplace transformed excitation signal technique which each have pros and cons. By combining the two impedance measurement techniques we are able to reduce the measurement time by a factor of 20 relative to ordinary single-sine measurements. Further we use the impedance measurements to calculate the overvoltage as a function of state of charge and the difference between charging overvoltage and discharging overvoltage and compare it with measurements.

Pressurized Operation of a Planar Solid Oxide Cell Stack

“…The measurement system is described further detail elsewhere. [24] From the iV curves, the area specific resistance (ASR) of the individual cells within the stack was found to be ~0.5  cm -2 . This means the voltage vibration amplitude used to record the impedance spectra was ~5 mV on the individual cells such that a linear relationship between current and polarization voltage can be assumed.…”

Characterization of a Planar Solid Oxide Cell Stack Operated at Elevated Pressure

“…The measurement system is described in further detail elsewhere. 21 From the iV curves, the area specific resistance (ASR) of the individual cells within the stack was found to be ∼0.5 cm −2 . This means the voltage pertubation amplitude used to record the impedance spectra was ∼5 mV on the individual cells.…”

A Lithium‐Rich Compound Li7Mn(BO3)3 Containing Mn2+ in Tetrahedral Coordination: A Cathode Candidate for Lithium‐Ion Batteries

“…[7] Recently, we demonstrated a high capacity of 145 mA h g À1 within 4.7-1.7 V for h-LiMnBO 3 by employing nanoparticles and a composite electrode utilizing reduced graphite oxide. [8] Even though the theoretical capacities for LiFeBO 3 and LiMnBO 3 , of approximately 220 and 222 mA h g À1 , respectively, are larger than those of presently employed oxides, capacities are still low compared to what in principle is possible and future needs. [9][10][11] Herein, we present the new Li-rich compound Li 7 Mn-(BO 3 The MnO 4 -tetrahedra form columns extending along the crystallographic c-axis ( Figure 2) and only have Li atoms in their first coordination spheres.…”

“…Together with its large concentration of Li atoms this compound could potentially become a fully lithiated cathode material for lithium-ion batteries, extending the limited range of electric vehicles. [2,3] The presently employed Li x (Ni,Mn,Co)O 2 (NMC) and Li x FePO 4 (LFP) are quite moderate in terms of capacity with theoretical specific charges of 140 to 170 mA h g À1 . [4,5] The poor electronic conductor LFP, which can be activated by wrapping up nanoparticles in a conductive composite, has a high cycling stability which is ascribed to the linking phosphate groups.…”

“…[2,3] The presently employed Li x (Ni,Mn,Co)O 2 (NMC) and Li x FePO 4 (LFP) are quite moderate in terms of capacity with theoretical specific charges of 140 to 170 mA h g À1 . [4,5] The poor electronic conductor LFP, which can be activated by wrapping up nanoparticles in a conductive composite, has a high cycling stability which is ascribed to the linking phosphate groups. Borate groups may fulfill a similar function but at a lower specific weight.…”