PVP (polyvinylpyrrolidone) is a commonly used functional additive in carbon nanotube (CNT) systems for batteries. Its core function is to solve the problem of entanglement and aggregation of carbon nanotubes due to their high specific surface area and strong van der Waals forces, providing crucial support for the effective construction of the electrode conductive network. Carbon nanotubes, as commonly used high-performance conductive agents, possess excellent electron transport capabilities due to their one-dimensional nanostructure. However, in a dry state, they easily entangle and form "cotton-like" aggregates. Direct addition to the electrode can lead to broken conductive pathways and uneven dispersion, hindering the full realization of their conductive advantages and affecting the quality of electrode forming. PVP, through the synergistic effect of its polar lactam groups and non-polar alkyl chains, can rapidly adsorb onto the surface of carbon nanotubes, forming a thin and uniform polymer coating layer.

This layer breaks the attractive forces between particles through steric hindrance, deagglomerating the aggregated carbon nanotubes into single or a small number of bundled structures, while simultaneously inhibiting secondary aggregation, ensuring good dispersion stability of carbon nanotubes in the dry powder system. In electrode fabrication processes, the modification effect of PVP on carbon nanotubes helps improve processing adaptability and overall electrode performance. A common approach is a "premix-compound" process, where PVP and carbon nanotubes are first dry-premixed, utilizing the dispersing effect of PVP to fluff the carbon nanotubes. Then, PVP is compounded with positive electrode active materials (such as NCM, LFP), negative electrode active materials (such as graphite, silicon carbide), and main binders (such as PTFE, SBR). During this process, PVP not only reduces the friction coefficient between powder particles, improves the overall flowability and bulk density of the dry powder, and prevents localized enrichment or uneven distribution of carbon nanotubes, but also provides temporary binding force during dry roll forming, reducing defects such as powder shedding and cracking, and improving electrode density and mechanical strength. Especially in solvent-free dry electrode processes, the dual role of PVP in dispersion and auxiliary bonding is crucial. It helps carbon nanotubes construct a continuous, interconnected conductive network within the electrode, effectively reducing electrode resistivity. Compared to systems without PVP, electrode conductivity is significantly improved, while simultaneously ensuring electrode flexibility and processing continuity.

PVP's modification of the carbon nanotube interface further optimizes the battery's electrochemical performance and cycle stability. The reduced surface energy of PVP-coated carbon nanotubes significantly enhances the interfacial bonding with active material particles and current collectors. During battery charging and discharging, it effectively resists the impact of volume changes in active materials (such as the expansion and contraction of silicon-carbon anodes), reducing conductive network damage and detachment, and maintaining electrode structural stability. Simultaneously, PVP exhibits excellent electrolyte affinity, improving the wetting effect of carbon nanotubes and the entire electrode on the electrolyte, shortening electrolyte penetration time, reducing interfacial impedance, and enhancing ion transport efficiency, thus effectively improving the battery's rate charge/discharge performance. In high-performance battery systems such as high-nickel ternary cathodes and silicon-carbon anodes, the addition amount of carbon nanotubes is relatively high, and dispersion is more difficult. Adding an appropriate amount of PVP (typically 20%-25% of the carbon nanotube mass) can stabilize the conductive network structure with minimal impact on ion conduction, mitigate performance degradation caused by material volume effects, extend battery cycle life, and improve capacity retention.

In practical applications, the use of PVP requires careful control of the addition amount and molecular weight selection to balance dispersion effect and battery performance. Regarding molecular weight, medium molecular weight PVP K25/K30 is a widely used model, with good compatibility between dispersion ability and rheological properties. It can achieve efficient depolymerization of carbon nanotubes without causing abnormal dry powder viscosity due to excessively long molecular chains. High molecular weight PVP K90 is suitable for scenarios requiring high adhesion, but the dosage must be controlled to avoid affecting conductivity efficiency. Regarding the dosage, excessive addition (more than 30% of the carbon nanotube mass) will result in an excessively thick coating layer on the carbon nanotube surface, hindering electron and ion transport, increasing interfacial impedance, and the residual PVP may decompose at high temperatures or affect electrolyte stability. Insufficient addition, on the other hand, will fail to achieve the desired dispersion effect, and the carbon nanotubes will still easily aggregate. With the rapid development of new battery technologies such as dry electrodes and solid-state batteries, higher requirements are placed on the dispersion quality and process adaptability of carbon nanotubes. Due to its good dispersibility, compatibility, and process adaptability, PVP will continue to be a commonly used functional additive in carbon nanotube systems, providing technical support for the research and industrialization of high-performance, low-cost batteries.

PENGFEI is a company dedicated to the research, production, and sales of 2-pyrrolidone (2-P), N-vinylpyrrolidone (NVP), and polyvinylpyrrolidone (PVP)