Add the black beans, onion, garlic, diced tomatoes, jalapeno, vegetable broth, chili powder, cumin, smoked paprika, cayenne pepper, and salt to the slow cooker.
Stir everything together until the spices are evenly distributed.
Cover and cook on low for 6 hours or on high for 3 hours.
Use an immersion blender to partially blend the soup for a thicker texture, leaving some beans whole.
Taste and adjust salt if needed.
Ladle into bowls and top with cilantro, a squeeze of lime, and diced avocado before serving.