Short answer
If the empty cell or device tray says CR2025, do not fit CR2016 (or the reverse) because they “look the same.”
DL2025 / ECR2025 map to CR2025; DL2016 / ECR2016 map to CR2016 — still the same thickness rule.
What is the same
Both are 3-volt lithium coin cells about 20 mm across. Pack labels such as DL2025 / ECR2025 or DL2016 / ECR2016 are brand names for the same IEC size — not a different battery.
What is different
Thickness: CR2025 is about 2.5 mm; CR2016 is about 1.6 mm. A thinner cell can sit loose or lose contact; a thicker cell may not fit the tray or can stress the cover.
Capacity and runtime also differ because of the volume difference — do not assume “close enough” from looking at the face of the cell.
Also in this diameter family
CR2032 is the same 20 mm face but thicker again (~3.2 mm) — see CR2032 vs CR2025 for that 1v1, or CR2032 vs CR2025 vs CR2016 for the full thickness ladder.
Do not use list
Do not swap CR2025 and CR2016 by diameter alone.
Do not treat either cell as a CR2032 substitute without checking thickness.