To make the spice blend, mix together the chili powder, cumin, coriander, chipotle powder, and oregano in a small bowl. Set aside until needed.
To make the chili, heat the olive oil in a large pot over medium-high heat. Add the onion and a pinch of salt, and cook until it begins to soften, 4 to 5 minutes. Add the poblano and jalapeño peppers, and cook for an addition 3 to 4 minutes. Stir in the garlic and spice blend. Cook for an additional minute or two, until fragrant.
Stir in the sweet potato, corn, beans, tomatoes, broth, and salt. Bring to a boil. Reduce heat to low and cover. Simmer for 25 to 30 minutes, until the sweet potatoes are fork-tender. Add the lime juice, taste and adjust seasonings as desired, and serve with lime wedges and chopped cilantro. The chili will keep in the refrigerator for 5 days. Cooled portions freeze beautifully and are best enjoyed within three months.