Can a power bank charge a laptop?

Yes, if it supports USB-C Power Delivery at a high enough wattage. Reviewers recommend 65W or more for most ultrabooks and 100W for power-hungry laptops. A recurring caveat in specialist threads is that advertised 'total' wattage figures (like 145W or 165W) are split across multiple ports, so a single port may cap lower than the headline number.