Identifying contaminants in Li-Ion battery production using AZtecFeature

Introduction

Lithium Ion batteries are found in most mobile electronic devices (e.g. laptop computers, phones etc). They are the dominant battery technology due to their superior energy to weight ratio and lack of memory effect. They are also the primary battery type used in the latest generation of electric and hybrid cars.

Quality control and monitoring of the manufacturing process is crucial as small deviations and low levels of contaminants can have catastrophic consequences. There have been many expensive instances during the last years where millions of devices containing Li-ion batteries have had to be recalled due to manufacturing problems. Contamination with metal particles can in some circumstances create a short circuit between the anode and cathode, which can result in a thermal runaway leading to an explosion of the battery.

Metallic foreign particle causes short, leading to thermal runaway (area in red).

Particle Detection and Identification with AZtecFeature

AZtecFeature automatically detects and categorizes small particles over large sample areas according to their size and composition. This information can be used to trace the origin of the particles to specific contamination sources in the production line. Particles gathered from filters installed in a Li-Ion battery manufacturing line were analysed in order to identify the sources of contamination and monitor the level of contaminants.

Figure showing a schematic of Li-Ion battery production process.

AZtecFeature distinguished accurately between particles containing cobalt oxide which are part of the manufacturing process and harmful contaminants containing Fe, Ni and Cr. The accurate quantification by particle size and composition allowed the source of contamination to be traced back to stainless steel piping through which battery parts are transferred between manufacturing steps. Furthermore, accurate size measurement with AZtecFeature was used to screen for particles large enough to pierce the membrane between anode and cathode which can lead to catastrophic failure of the battery. After proof of concept, the manufacturer now uses AZtecFeature to periodically analyse contamination levels in the filters and prevent any significant build-up of detrimental metal particle contamination. A run consisting of finding, analysing and categorising over 900 particles takes just 12 minutes.

Table showing three different classes of particles identified by AZtecFeature.

Figure showing (a) a typical field of view with one particle selected and (b) showing the spectrum of that particle.