Why is electrolytic manganese dioxide supply seen as the bottleneck for sodium-ion battery cathode growth?

Why is electrolytic manganese dioxide supply seen as the bottleneck for sodium-ion battery cathode growth?
Sodium-ion layered oxide cathodes rely mainly on sodium carbonate and manganese dioxide, and soda ash capacity is ample. Manganese dioxide is the real constraint. China's electrolytic manganese dioxide (EMD) capacity totals about 380,500 tonnes, consumed largely by primary alkaline batteries and lithium manganese oxide cathodes. The sector is highly concentrated, with the top three producers holding roughly 79% share. Because EMD is a capacity-restricted product, future expansion is limited, with only a few planned additions. Under an aggressive scenario where layered oxides dominate, manganese dioxide demand could reach around 141,000 tonnes by 2026, a significant jump that tight supply may struggle to meet.