Erik R. Scott

Evaluation of Effects of Additives in Wound Li-Ion Cells Through High Precision Coulometry

LiCoO 2 /graphite and LiCoO 2 /Li 4 Ti 5 O 12 wound prismatic cells were examined with and without electrolyte additives using the high precision charger at Dalhousie University. The additives tested were vinylene carbonate, trimethoxyboroxine, and lithium (bis) trifluoromethanesulfonimide. The voltage curves, charge and discharge end point positions, fade, and coulombic efficiency were compared to gain an understanding of the effects of the electrolyte additives on the cells. Long term cycling data (capacity loss over 750 cycles) was compared with predicted lifetime measurements based on high precision coulometry. Design of experiments was used in order to help interpret the results from the 20 groups of cells tested. .

Material and Design Options for Avoiding Lithium Plating during Charging

In lithium ion batteries, an important design objective is to avoid the plating of lithium during charging. Generally, plated Li is not completely reversible, and therefore even small amounts can have significant consequences due to accumulation with cycling. The consequences can include loss of capacity, mechanical swelling and, potentially, the formation of a short. Cell design aspects commonly applied to avoid lithium-plating include cell balance (areal capacity ratio of the negative electrode to that of the positive), electrolyte fill, current and “overlap” (the distance by which the negative electrode extends beyond the edge of the positive electrode, Figure 1).

Modeling Li/CF x -SVO Hybrid-Cathode Batteries

and kinetic parameters, the model simulations are first fit to dis- charge data from Li/CFx and Li/SVO batteries. The model simula- tions are then compared to discharge curves from Li/CFx-SVO hybrid-cathode batteries of various mix ratios, electrode thicknesses and geometric areas. Finally, limits on discharge rates and battery design are established, within which the model accurately predicts performance.

Energy harvesting and implantable medical devices - first order selection criteria

Power density is the critical attribute of an APS for use in an IMD, and benchmark value of at least 0.01mW/cm3 has been established in order for an APS to be volumetrically superior to existing primary and rechargeable battery technologies. The benchmark power density enables the use of simple, physics-based models to quickly evaluate the potential viability of proposed APS technologies.

Modeling Transients in Li/CFx-SVO Hybrid-Cathode Batteries

This document describes a first-principles-based mathematical model developed to predict the transient voltage-time behavior of batteries having hybrid cathodes comprising a mixture of carbon monofluoride (CFx) and silver vanadium oxide (SVO). These batteries typically operate at low to moderate rates of discharge, lasting several years. However, newer applications demand highrate discharges from these batteries, although for a relatively short period of time. The model presented here is a very useful tool for design optimization and performance prediction of batteries under low-rate discharges as well as high-current pulses.

Mathematical Modeling of Li/CFx-SVO Batteries

This document describes a first-principles-based mathematical model developed to predict the voltage-capacity behavior of batteries having hybrid cathodes comprising a mixture of carbon monofluoride (CFx) and silver vanadium oxide (SVO). These batteries typically operate at moderate rates of discharge, lasting several years. The model presented here is an accurate tool for design optimization and performance prediction of batteries under current drains that encompass both the application rate and accelerated testing.

Predicting charge-times of implantable cardioverter defibrillators

A novel method of validation of the mathematical model for batteries that power Medtronics Implantable Cardioverter Defibrillators (ICDs) is presented. In a conventional approach used in the past, the model has been validated against data collected in controlled laboratory conditions. To supplement this approach, we now validate the model against ICD performance data reported from devices used in the field for periods ranging from about five to seven years. The key model output is ICD “charge time” — the time required to charge a high voltage capacitor in preparation to deliver shock to the heart. This validation is carried out for five of Medtronics ICD designs and very close agreement is obtained between model predictions and field data.