State of Charge Tracking Corrections under Battery Open Circuit Hysteresis
Dynamic hysteresis state expansion in Kalman filters fixes open circuit voltage tracking errors, maintaining state of charge accuracy across flat plateau chemistries.
Nanoscale Phase Strain
Meaning
Atomic level deformation occurs within the crystalline structure of electrode materials during the insertion and removal of ions. Advanced characterisation techniques measure nanoscale phase strain to understand the mechanical fatigue that leads to battery degradation. This phenomenon arises when different regions of a particle expand or contract at different rates during a charge cycle.
The resulting stress can eventually cause the active material to crack or lose electrical contact.
Material Fatigue
Accumulation of structural defects over time reduces the ability of the lattice to host lithium atoms. Prolonged exposure to nanoscale phase strain weakens the bond between the individual grains of the cathode. This mechanical breakdown appears as a loss of capacity and an increase in internal resistance.
Materials scientists study these effects to develop more resilient crystal structures for long life batteries.
Measurement Technique
Synchrotron x-ray diffraction provides the resolution needed to observe the shifting planes of atoms within a single nanoparticle. Researchers use this data to map the distribution of nanoscale phase strain across the volume of the electrode. The results show how current density affects the uniformity of the reaction.
High rates of charge often exacerbate the strain gradients and lead to faster wear.
Design Requirement
Mitigation of structural stress involves the selection of dopants or coatings that stabilise the crystal lattice. Reducing the impact of nanoscale phase strain is a primary goal in the development of nickel rich cathode materials.