Full Cell Voltage Boundary Calibration to Prevent Crystalline Lithium Silicide Nucleation
Upper full cell voltage cutoff calibration limits local anode lithiation potential above 50 mV vs Li/Li+ to prevent crystalline silicon phase breakdown.
Incremental Capacity Curve
Meaning
Mathematical transformation of voltage and capacity data into a plot highlighting electrochemical phase transitions defines this tool. Generating an incremental capacity curve involves calculating the derivative of capacity with respect to voltage.
Electrochemical Signature
Unique arrangement of peaks in the plot acts as a fingerprint for the specific chemistry of the electrodes. While an incremental capacity curve shows the locations where the battery accepts the most charge, it also indicates the thermodynamic equilibrium of the system. Each peak corresponds to a phase transition in either the cathode or the anode.
Degradation Analysis
Comparison of the plots over the lifetime of the battery reveals how the internal components are failing. If the peaks on the incremental capacity curve shift or shrink, it signifies the loss of active lithium or the degradation of the electrode material. This non-invasive technique allows for the diagnosis of health without disassembling the cell.
By monitoring the relative heights of the peaks, researchers can distinguish between the loss of inventory and the increase in resistance.
Data Resolution
Quality of the derivative plot depends heavily on the precision of the voltage and current measurements. Because small amounts of noise can obscure the peaks, an incremental capacity curve usually requires filtering or smoothing algorithms. Stable environmental conditions are necessary to prevent temperature fluctuations from distorting the results during the long test periods.