The quality of Li-ion batteries is highly related to the crystallinity of the graphite used in their electrodes. Therefore, the development of two-dimensional detection equipment for evaluating the integrity of graphite electrodes is critical. In this study, a triaxial scanning platform was developed for Raman spectroscopy. Two-dimensional Raman mapping of the defects (D band) and stacking (2D band) of graphite electrodes was performed to determine atomic-level variations caused by charging. Through Raman mapping, the effects of constant-current-constant-voltage (CC-CV) and CC-reFLEX fast charging were compared. The graphite damage from CC-reFLEX fast charging was less extensive than that from CC-CV charging. Furthermore, investigations using the triaxial platform revealed that the graphite on a curved electrode exhibited disordered stacking after several charging-discharging cycles. This phenomenon creates safety concerns.

To address the defects in lithium-ion battery lifespan, this paper proposes a composite waveform generation strategy that offers capacity-recovering effect. Based on digital architecture, this study exploits direct digital synthesis (DDS) to generate data, which are then processed in an analog-to-digital converter to produce a predefined voltage waveform signal. In the process, an arbitrary waveform is converted to digital voltage waveform signal through pulse width modulation (PWM) technology, thus realizing waveform generation through DDS. Subsequently, analog-to-digital conversion is accomplished by going through a buck circuit, resulting in a composite sinusoidal waveform that is used to charge the battery with a recovering effect. This paper comprises an introduction of effective waveforms for capacity recovering, methods of generating composite sinusoidal waveforms, and an example of the application of composite sinusoidal waveform generation. The waveform produced by the circuit may recover the capacity of an aged 18650 lithium-ion battery by about 8%.