Place the sweet potato cubes, black beans, diced tomatoes, and vegetable broth into the slow cooker.
Add the diced onion, minced garlic, chili powder, cumin, and salt.
Stir everything together until the spices are evenly distributed.
Cover and cook on low for 6 to 7 hours or on high for 3 to 4 hours, until the sweet potatoes are tender.
Taste and adjust salt if needed.
Ladle into bowls and top with fresh cilantro and a squeeze of lime.