Battery Research and Manufacturing
Raman Imaging and Microscopy Energy Storage Applications
Cycle characteristics analysis of silicon-graphite negative electrodes
Lithium-ion batteries power devices like smartphones, laptops, electric vehicles, and renewable energy systems. Silicon-graphite composite negative electrodes combine silicon's energy capacity with graphite's stability, but face challenges like volume expansion and silicon pulverization, limiting longevity and efficiency.
Binders such as PVdF and PAANa effectively tackle these issues by maintaining electrode integrity during charge and discharge cycles. Raman microscopy characterizes the binding mechanism between electrode components and binders, evaluating binder distribution and homogeneity. RAMANtouch analyzed silicon-graphite composite negative electrodes, revealing that PAANa binders promote uniform silicon alloying, enhancing stability.
In contrast, electrodes with PVdF binders showed scattered and inactive nano-silicon after cycling, indicating volume expansion issues. This highlights PAANa's effectiveness in improving electrode stability and demonstrates Raman spectroscopy's utility in battery design optimization. By overlaying surface morphology with Raman images, the distribution and behavior of various components within the electrode material were examined.
Non-atmosphere-exposed Raman imaging of lithium-ion cathodes
Silicon, capable of absorbing more lithium than graphite, is a promising material for high-capacity lithium-ion battery negative electrodes. However, its large volume changes during charging and discharging often lead to a transformation of crystalline silicon into an amorphous state.
This can cause irreversible capacity loss, structural degradation, altered diffusion kinetics, and electrode instability, impacting battery performance and longevity. This is shown in the example below. The condition of silicon-based negative electrodes in lithium-ion batteries was examined using Raman imaging before and after charging.
Additionally, the silicon crystal can also collapse due to volume changes during charging and discharging. This can be omitted by dispersing the silicone particles finely which can be accomplished by using binders such as polyacrylic acid sodium (PANa) and polyvinylidene fluoride PVdF.
In the example below it was shown by Raman imaging that using polyacrylic acid sodium (PANa) as the binder enables homogeneous dispersion of each component. On the other hand, in electrode plates using PVdF as the binder, a bias towards a mixed state of graphite and Ketjen Black is observed compared to when PANa is used as the binder (Figure below).
