Effect of Binder Content on Silicon Microparticle Anodes for Lithium-Ion Batteries

Abstract

Formulation strongly influences the structure, properties, and electrochemical performance of composite electrodes. The role of polymeric binders is especially critical for electrodes containing high volume change active materials, such as silicon. In this study, we investigated the impact of polyimide binder in silicon microparticle electrodes. The impact of binder content on electrode adhesion to the current collector, cohesion, porosity, electrical resistivity, local electrical connectivity, and silicon utilization was characterized in pristine and cycled electrodes to elucidate the mechanisms driving the electrochemical performance during rate and cycle life tests of Si-NMC622 full cells. We observed that capacity retention improved with increasing binder content, but rate performance suffered with excess binder content, indicating that there is an optimal binder weight fraction to balance the trade-off between these two metrics. Our research reveals important design principles for the optimization of binder content in silicon electrode formulations and can be applied to the development of electrodes containing other active materials and conductive additives.

Magnetic Force Dilatometry of Silicon-NMC622 Lithium-Ion Coin Cells: The Effects of Binder, Capacity Ratio, and Electrolyte Selection

“…Our previous work found that silicon utilization with cycling is influenced by binder content. 80 Namely, silicon utilization in the 3 × PI electrodes increases by 200% after 50 cycles, compared to only 75% for the 1 × PI electrodes. We believe this explains the current observation-that reversible expansion in the high binder electrodes increases in later cycles as the silicon utilization also increases.…”

“…The higher binder content also reduces the electrode porosity and limits silicon particle accessibility in early cycles. 80 With less amorphization of the available silicon, we expect less volume change. This trend reverses in later cycles.…”

“…Electrode preparation and coin cell fabrication.-Our NMC622 cathode and silicon anode electrodes with polyimide (PI) binder (Ube corporation, U-Varnish A) was prepared using the same method as described in our previous publication. 80 Briefly, electrode components were mixed in a planetary mixer with N-Methyl-2pyrrolidone to form a slurry, coated onto copper foil by doctor blade, and dried in a vacuum oven at 80 °C overnight before coin cell preparation. In this study, we used an 80/10/10 silicon (2 μm)/ graphene nanoplatelet (GNP, XG Sciences H5)/binder weight ratio as the baseline electrode formulation, called "1 × PI."…”

Investigating the Structure and Performance of Electrodes Made by Dry and Wet Slurry Processes

“…22,29 The former reduces the available capacity, while the latter limits the fast transfer of ions and electrons, leading to decreased performance. 27,30,31 For slurry electrodes, minimal particle cracking and a more homogenous and porous distribution of the PVDF and CB provided more efficient conductive paths, leading to better performance at high C-rates. It is also important to highlight that the electrodes experienced significant capacity loss at >3 C, e.g., 14 and 25 mAh g -1 for dry and slurry electrodes, respectively.…”

Piezoresistive Free‐standing Microfiber Strain Sensor for High‐resolution Battery Thickness Monitoring

“…The state-of-the-art lithium-ion (Li-ion) battery is a widely used rechargeable energy storage device in application areas ranging of the Li-ion battery is a critical domain for improving its lifetime and performance. [4,5] Battery health diagnostic through the characterization of volume or thickness changes has been investigated by numerous studies using different methods: neutron imaging, [6] in situ X-ray diffraction, [7,8] in situ atomic force microscopy, [9] 3D digital image correlation, [10,11] mechanical measurement methods, [1,2,[12][13][14][15] thickness gauges, [3,16] ultrasonic probing, [17,18] and optical sensors. [19][20][21][22] However, all the measurement methods and sensors either require complicated laboratory setups, cannot be seamlessly integrated for in situ monitoring, and are not cost-efficient.…”