Understanding and mitigation of Li-ion batteries ageing

A battery is a reversible electrochemical energy storage and conversion system based on redox reactions. It consists of a set of accumulators, also called "cells", electrically connected to deliver energy and electrical power at the chosen voltage level. A battery is usually equipped with an electronic system called "BMS" (Battery Management System) to manage charging and discharging based on current, voltage and temperature signals. Within a battery, each lithium-ion cell comprises the following internal components:

• a positive and a negative electrode which both insert and deinsert lithium ions;

• an electrolyte that transports lithium ions;

• a separator that provides electrical insulation between the two electrodes;

• a connector to ensure the passage of electrons between the electrical circuit and the electrodes;

• a case or packaging to guarantee watertightness, as lithium compounds can be unstable in water and air.

Over time, as a result of chemical or electrochemical instability of these components and/or interaction with the environment, battery ageing is observed, i.e. an irreversible reduction in performance (energy, power) and therefore in its lifespan. Battery ageing depends on many factors, and remains difficult to control. However, the economic and environmental stakes are high, and progress is being made every year in improving battery life .

Since the first Li-ion accumulators were marketed in the early 1990s, and especially over the last fifteen years, the global battery market has experienced very strong growth of around 30% per year, with the development of electric transport and stationary energy storage requiring large volumes of batteries with high storage capacity, safe operation and durability. To meet the demands of these new applications, battery technologies have evolved. Three generations of Li-ion batteries have already been developed, with graphite-based negative electrodes, liquid electrolytes and different positive electrode materials. As a result, there are a multitude of different batteries, with material compositions, microstructure and internal component architecture all varying from one battery reference to another, leading to different initial performance and ageing. Other variables such as cell manufacturing process, battery architecture and conditions of use also need to be taken into account,...