Li-Ion Battery Performance Degradation Modeling for the Optimal Design and Energy Management of Electrified Propulsion Systems

Li Chen,Yuqi Tong,Zuomin Dong

doi:10.3390/en13071629

Abstract

Heavy-duty hybrid electric vehicles and marine vessels need a sizeable electric energy storage system (ESS). The size and energy management strategy (EMS) of the ESS affects the system performance, cost, emissions, and safety. Traditional power-demand-based and fuel-economy-driven ESS sizing and energy management has often led to shortened battery cycle life and higher replacement costs. To consider minimizing the total lifecycle cost (LCC) of hybrid electric propulsion systems, the battery performance degradation and the life prediction model is a critical element in the optimal design process. In this work, a new Li-ion battery (LIB) performance degradation model is introduced based on a large set of cycling experiment data on LiFePO4 (LFP) batteries to predict their capacity decay, resistance increase and the remaining cycle life under various use patterns. Critical parameters of the semi-empirical, amended equivalent circuit model were identified using least-square fitting. The model is used to calculate the investment, operation, replacement and recycling costs of the battery ESS over its lifetime. Validation of the model is made using battery cycling experimental data. The new LFP battery performance degradation model is used in optimizing the sizes of the key hybrid electric powertrain component of an electrified ferry ship with the minimum overall LCC. The optimization result presents a 12 percent improvement over the traditional power demand-driven hybrid powertrain design method. The research supports optimal sizing and EMS development of hybrid electric vehicles and vessels to achieve minimum lifecycle costs.

Highlights

With the increasing concerns on the emissions of greenhouse gases (GHG) and other air pollutants, the automotive and marine industry are adopting hybrid electric or pure electric propulsion systems for vehicles and marine vessels with large onboard battery energy storage system (ESS) at an increasing pace
Among different kinds of Li-ion battery (LIB), the LiFePO4 (LFP) battery has been widely used in heavy-duty transportation applications, due to its lower cost and non-toxicity, well-defined performance, better long-term stability, and capability to fit for more extensive variations in temperature
The optimizations of the size and energy management strategy (EMS) of the battery ESS in a hybrid electric propulsion system have been significant interest and focal point of research for years. These optimizations cannot be achieved without an accurate model for predicting the performance degradation and operating life of the battery under different use patterns

Summary

Introduction

With the increasing concerns on the emissions of greenhouse gases (GHG) and other air pollutants, the automotive and marine industry are adopting hybrid electric or pure electric propulsion systems for vehicles and marine vessels with large onboard battery energy storage system (ESS) at an increasing pace. Among different kinds of LIBs, the LiFePO4 (LFP) battery has been widely used in heavy-duty transportation applications, due to its lower cost and non-toxicity, well-defined performance, better long-term stability, and capability to fit for more extensive variations in temperature. The service life of battery ESSs is a critical issue for various types of electrified vehicles (EV), as well as their marine counterparts. Considerable efforts have been devoted to capturing the performance degradation and extending the operating life of batteries. There are limited efforts on the quantitative analysis of how battery capacity loss would

Methods

Results

Conclusion