Modeling of Capacity Fading and Investigation of Maximum Capacity for Lithium-Ion Batteries

• Main Authors: Shih-Cheng Liu, 劉師程
• Other Authors: 吳文方
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/12080929992817127180

碩士 === 國立臺灣大學 === 工業工程學研究所 === 102 === Since the failure of a battery could lead to loss of operation, reduced capability, downtime, and even catastrophic failure, to improve its health and reduce its degradation are important issues to researchers and experts. The mechanism of battery degradation is complicated and related to conditions of usage as well as other external characteristics. Factors affecting the battery life include the ambient temperature, charge and discharge rate, depth of discharge, etc. This research is based on accelerated life test data collected from NASA Ames Prognostics Center of Excellence (PCoE) for its custom-built type 18650 lithium-ion battery. Two capacity fading models are proposed from curve fitting and regression analysis of the data. These two models are then used for estimating cycle-life of the battery in consideration of environmental factors. Based on these two models, this research also investigates relations between battery life and its usage conditions from battery-management point of view. The purpose is to obtain the maximum total capacity of the battery in its life cycle through a battery management optimization problem in which both the depth of discharge and discharge rate are considered. Through the analysis, it is found that an exponential trend fits better than the power trend in capacity fading for higher rates of discharge. It is also found that, when the discharge is in room temperature, the rate of discharge is 1C, and failures of battery are defined as 70%、60% and 50% of the SOH, the maximum total capacities in the life cycle of battery are 253,997, 284,183 and 304,447 mAh, respectively. Moreover, it is suggested to terminate the discharge when the voltage decreases to 3.02 V, 2.98 V and 2.96 V for each of the above conditions. Their corresponding cycle-lives can be found as well. It is believed that the above results can provide battery users as well as manufacturers to achieve the optimal usage of the battery in its life cycle.