Place the sweet potato cubes, black beans, onion, garlic, and bell pepper into the slow cooker.
Add the diced tomatoes with their juices and the vegetable broth.
Stir in the smoked paprika, cumin, chili powder, minced chipotle pepper, and salt until the spices are evenly distributed.
Cover and cook on low for 7 hours until the sweet potatoes are tender.
Taste and adjust salt if needed.
Ladle into bowls and add cilantro, a squeeze of lime, and avocado slices before serving.