# Other and primary batteries: Engineering and performance Why non-flammable zinc still loses to lithium on the grid Source page: https://www.materialinsights.org/energy/e_other_batt/sg-eng/ What this tab covers Engineering and operating performance: round-trip efficiency, whether power and energy can be scaled separately, footprint and siting, and safety. Engineering data for emerging chemistries are thin; zinc-based grid systems cost more than lithium-ion in PNNL's 2021 estimate and were not yet available at 100 MW scale. Primary cells are judged on shelf life and energy per cell rather than efficiency. #### Round-trip efficiency Mixed Lithium-ion reaches about 85 to 90% (Sandia). Water-based zinc chemistries are less efficient because of side reactions: Sandia gives about 75% for zinc-manganese dioxide, and a 2025 review reports energy efficiency from below 64% to above 89% depending on the cathode. Round-trip efficiency does not apply to primary cells, which are used once.^[13](https://pubs.rsc.org/en/content/articlehtml/2026/eb/d5eb00159e)^[15](https://www.sandia.gov/app/uploads/sites/273/2021/12/3_Passell_Howard_SNL_NECPUC_Session1_3-19-2021.pdf) Lithium-ion benchmark About 85-90%^[15](https://www.sandia.gov/app/uploads/sites/273/2021/12/3_Passell_Howard_SNL_NECPUC_Session1_3-19-2021.pdf) Zinc-manganese dioxide About 75%^[15](https://www.sandia.gov/app/uploads/sites/273/2021/12/3_Passell_Howard_SNL_NECPUC_Session1_3-19-2021.pdf) Aqueous zinc cells by cathode Below 64% to above 89%^[13](https://pubs.rsc.org/en/content/articlehtml/2026/eb/d5eb00159e) #### Power and energy decoupling Unfavourable These are solid-electrode batteries, so power and energy are fixed by cell design and cannot be sized separately. PNNL estimated a 10 MW, 10-hour zinc-based system at USD 449/kWh in 2021, above a 100 MW, 10-hour lithium iron phosphate system at USD 356/kWh, partly because zinc systems were not yet available at the larger scale.^[1](https://www.energy.gov/sites/default/files/2022-09/2022%20Grid%20Energy%20Storage%20Technology%20Cost%20and%20Performance%20Assessment.pdf) Zinc system, 10 MW / 10 h, 2021 USD 449/kWh^[1](https://www.energy.gov/sites/default/files/2022-09/2022%20Grid%20Energy%20Storage%20Technology%20Cost%20and%20Performance%20Assessment.pdf) LFP system, 100 MW / 10 h, 2021 USD 356/kWh^[1](https://www.energy.gov/sites/default/files/2022-09/2022%20Grid%20Energy%20Storage%20Technology%20Cost%20and%20Performance%20Assessment.pdf) #### Footprint and siting flexibility Mixed Zinc-ion and potassium-ion store less energy per kg than lithium-ion, so systems are larger. Their water-based or less reactive designs may allow denser indoor siting with fewer fire setbacks, but this depends on certification results that are not yet widely published. #### Safety and thermal runaway risk Mixed Zinc-ion's water-based electrolyte does not burn, the main safety advantage over lithium-ion. Potassium-ion uses organic electrolytes like lithium-ion and needs similar fire testing (UL 9540A and NFPA 855 in the US). Among primary cells, lithium coin cells are a known child-ingestion hazard and lithium metal can ignite if crushed. The EU caps mercury at 0.0005% in all batteries and lead at 0.01% in portable batteries from 18 Aug 2024, and requires portable batteries in products to be removable by the user.^[9](https://www.sgs.com/en/news/2023/09/safeguards-11523-eu-issues-new-regulation-on-batteries-and-waste-batteries) EU mercury limit 0.0005% by weight^[9](https://www.sgs.com/en/news/2023/09/safeguards-11523-eu-issues-new-regulation-on-batteries-and-waste-batteries) EU lead limit, portable batteries 0.01% from 18 Aug 2024^[9](https://www.sgs.com/en/news/2023/09/safeguards-11523-eu-issues-new-regulation-on-batteries-and-waste-batteries) #### Sources 1. [2022 Grid Energy Storage Technology Cost and Performance Assessment (PNNL-33283), Executive Summary p. vii](https://www.energy.gov/sites/default/files/2022-09/2022%20Grid%20Energy%20Storage%20Technology%20Cost%20and%20Performance%20Assessment.pdf) Pacific Northwest National Laboratory for US Department of Energy, 2022 2. [SafeGuardS 115/23: EU issues new regulation on batteries and waste batteries (summary of Regulation (EU) 2023/1542)](https://www.sgs.com/en/news/2023/09/safeguards-11523-eu-issues-new-regulation-on-batteries-and-waste-batteries) SGS, 2023 3. [Several concerns about aqueous zinc metal batteries: from components to unit cells (Li, Liang and Fang, EES Batteries, first published 22 Dec 2025)](https://pubs.rsc.org/en/content/articlehtml/2026/eb/d5eb00159e) Royal Society of Chemistry, 2025 4. [Energy Storage Overview (H. Passell, NECPUC Energy Storage Webinar Series, 19 Mar 2021)](https://www.sandia.gov/app/uploads/sites/273/2021/12/3_Passell_Howard_SNL_NECPUC_Session1_3-19-2021.pdf) Sandia National Laboratories, 2021 ## Other sections - [Summary](https://www.materialinsights.org/energy/e_other_batt/index.md) - [Overview](https://www.materialinsights.org/energy/e_other_batt/overview/index.md) - [Correlation](https://www.materialinsights.org/energy/e_other_batt/correlation/index.md) - [Science and technology](https://www.materialinsights.org/energy/e_other_batt/sg-sci/index.md) - [Economics](https://www.materialinsights.org/energy/e_other_batt/sg-econ/index.md) - [Impact and additionality](https://www.materialinsights.org/energy/e_other_batt/sg-impact/index.md) - [What to track](https://www.materialinsights.org/energy/e_other_batt/tracking/index.md) - [Relationships](https://www.materialinsights.org/energy/e_other_batt/links/index.md)