Coat a large Dutch oven with nonstick cooking spray and place over medium heat. Add oil and heat 1 minute. Add sweet potatoes and onion; cook and stir 7 to 10 minutes or until slightly tender. Stir in garlic, cumin, chili powder, cayenne, and salt to taste.
Add beans, tomatoes, broth and lime juice; stir well to combine. Reduce heat to low. Simmer, covered, 15 to 20 minutes or until sweet potatoes are soft.
Ladle chili into bowls. If desired, top with cheddar, sour cream and cilantro, and serve.