Heat oil in a heavy large saucepan or Dutch oven over medium-high heat; add onion. Reduce heat to medium, and cook, stirring occasionally, about 10 to 15 minutes or until tender. Add bell peppers, jalapeño, and sweet potato; cook, stirring occasionally, 5 minutes. Stir in garlic, and cook about 1 minute. Add chili powder and next 7 ingredients; stir and cook 1 minute. Add tomatoes and broth. Simmer, uncovered, about 30 minutes. Stir in beans, and continue to cook 10 minutes. Remove bay leaf, and stir in lime juice. Garnish, if desired.