Batteries can come form many manufacturers. Small companies may have lower operating cost but their smaller volume material purchase cannot compete with bigger companies perhaps. They may use lower cost material for casing and cheaper electronic component from clone chip manufacturers.

Explode or not depends can happened even on branded one also. Maybe can refer if the battery has CCP safety approval at least

Anyway, batteries are mostly (if not all) sourced from China. China has all material resources required and cheaper than any country I believe.