Experimental investigation of mechanical abuses influences on local heat generation for an electrically cycled Lithium-ion battery

The effort to save the modern society from energy crisis and the even more alarming environmental pollution has been made for years with challenges and hopes mutually emerging. The change of energy storage and propulsion system is driving a revolution in the automotive field to develop new electrified power-train system and storage system. In this context, Lithium-ion battery made its way along different storage systems because of its significant advantages such as high energy density, low self-discharge rate and high operative voltage. Now, with continuous improvement in lithium ion batteries energy density, enhancing their safety is becoming increasingly urgent for the electric vehicle development. Therefore, abstracting the daily usage of a battery pack, the cells undergo under several stress like temperature variation and different charging conditions and, during crash, mechanical stress could be encountered. Over the years, many tests have been developed to simulate the different stress and damage encountered during crash (ex. nail penetration). Lot of effort has been put into studying abusive and disruptive damage but only few take into consideration non-disruptive damages. This work wants to develop a series of non-disruptive test in order to find differences between a fresh battery and a mechanically loaded one regarding heat generation, voltage variations during electrical cycling and appreciable changing in voltage plateau. The battery under analysis is a laminate pouch-type cell, composed by Graphite as anode material and a spinel of NMC and LMO as Cathode material, with a rated capacity of 41Ah and a nominal voltage of 3.7V. The wanted impact was developed with a pressure applied on a custom plastic impactor. During all the tests voltage and temperature of the battery were registered in order to perpetrate the objectives set and understanding the causes of them.