Material Insights · Understanding the Material World

Other and primary batteries: Science and technology

Why zinc, magnesium and potassium are harder than they look

What this tab covers The physics and chemistry: how the energy is stored, which materials it needs (scarcity, toxicity, recyclability) and what makes it age.

This tile covers two very different groups: emerging rechargeable chemistries that replace lithium with zinc, magnesium or potassium, and single-use (primary) cells such as alkaline, lithium coin and silver-oxide. The first is an early-stage bet on cheaper, safer materials; the second is a mature consumer product with a waste problem.

Mechanism

Mixed

Zinc-ion, magnesium-ion and potassium-ion cells copy the lithium-ion principle: ions shuttle between two host electrodes (intercalation) or plate onto a metal anode. Zinc-ion cells use water-based electrolytes; magnesium ions carry two charges, which promises high capacity but makes them move slowly through electrode materials; potassium-ion can reuse graphite anodes and much lithium-ion manufacturing kit. Primary cells are discharged once: an alkaline cell oxidises zinc against manganese dioxide, a lithium coin cell oxidises lithium metal, and a silver-oxide button cell reduces silver oxide. Energizer's AA alkaline datasheet gives about 2,850 mAh at a light 25 mA drain from a 23 g cell, roughly 186 Wh/kg (calculated at the 1.5 V nominal voltage, so an upper bound because voltage sags under load), and a shelf life of 10 years at 21 C on the newer sheet (7 years on an older one). For aqueous zinc pouch cells, a 2025 review estimates about 50 Wh/kg under realistic design parameters and about 110 Wh/kg only under aggressive assumptions. A 2025 review of potassium-ion batteries notes that most progress has been shown in laboratory half-cells with thin electrodes, and that full cells remain well short of commercial needs.2131416

AA alkaline cell (Energizer datasheet) 2,850 mAh at 25 mA, 23 g; about 186 Wh/kg at nominal voltage (calculated, upper bound)2 AA alkaline shelf life 10 years at 21 C (newer sheet); 7 years (older sheet)162 Aqueous zinc pouch cell (design estimate) About 50 Wh/kg realistic; about 110 Wh/kg aggressive case13

Material scarcity and toxicity

Mixed

Zinc, magnesium and potassium are far more abundant than lithium, but supply is still concentrated: China mined about 32% of zinc and produced about 86% of primary magnesium in 2025 (calculated), while Canada supplied about 31% of potash (calculated). Lithium remains 88% a battery metal. Silver for silver-oxide cells is a precious metal; Mexico mined about 24% of world silver (calculated). Mercury has been removed from most batteries, with indium compounds replacing it in alkaline cells, but some button cells may still contain it.345678

China share of primary magnesium, 2025 About 86% (calculated from 950 of 1,100 thousand t)7 China share of zinc mine output, 2025 About 32% (calculated from 4,100 of 13,000 thousand t)6 Mexico share of silver mine output, 2025 About 24% (calculated from 6,300 of 26,000 t)4 Battery share of lithium use 88%5

Degradation and ageing

Mixed

Zinc-ion cells suffer from zinc dendrites and hydrogen gassing at the zinc anode; magnesium-ion cells struggle to find electrolytes that let magnesium plate and strip cleanly; potassium-ion electrodes swell because potassium ions are large. Laboratory coin cells flatter zinc: they often exceed 99.5% coulombic efficiency only because they use under 10% of the zinc, while high-capacity pouch cells often last fewer than 300 cycles; the best reported include an Ah-scale cell beyond 680 cycles and one keeping 88.6% capacity after 750 cycles at 53.3% depth of discharge. Potassium-ion full cells still fall short of commercial cycle-life requirements, and no commercial magnesium-ion cycle data were found. Primary cells age by slow self-discharge on the shelf.1314

Zinc pouch cells, typical Often under 300 cycles13 Best zinc pouch result 88.6% capacity after 750 cycles at 53.3% depth of discharge13

Chemistries covered by this tile131314

ChemistryTypeMaturityMain issue
Zinc-ionRechargeable, water-basedEarly commercial; zinc systems not yet at 100 MW scaleDendrites, cycle life
Magnesium-ionRechargeableLaboratoryElectrolyte compatibility, slow ion movement
Potassium-ionRechargeableLaboratory to pilot; full cells short of commercial needsElectrode swelling, lower energy than lithium-ion
Alkaline (zinc-manganese dioxide)PrimaryMature mass marketSingle use, waste
Lithium coin (lithium metal)PrimaryMatureSwallowing hazard, fire risk if damaged
Silver-oxidePrimary buttonMature nicheSilver cost; some contain mercury

Sources

  1. 2022 Grid Energy Storage Technology Cost and Performance Assessment (PNNL-33283), Executive Summary p. vii Pacific Northwest National Laboratory for US Department of Energy, 2022
  2. Energizer E91 AA alkaline product datasheet, older edition (Form EBC-1102G; undated, hosted by a third-party distributor) Eveready Battery Company (Energizer)
  3. Mineral Commodity Summaries 2026: Mercury US Geological Survey, 2026
  4. Mineral Commodity Summaries 2026: Silver US Geological Survey, 2026
  5. Mineral Commodity Summaries 2026: Lithium US Geological Survey, 2026
  6. Mineral Commodity Summaries 2026: Zinc US Geological Survey, 2026
  7. Mineral Commodity Summaries 2026: Magnesium Metal US Geological Survey, 2026
  8. Mineral Commodity Summaries 2026: Potash US Geological Survey, 2026
  9. Several concerns about aqueous zinc metal batteries: from components to unit cells (Li, Liang and Fang, EES Batteries, first published 22 Dec 2025) Royal Society of Chemistry, 2025
  10. 10 years development of potassium-ion batteries (Li, Wang, Wang, Lyu, Wang, Xia, Mao and Guo, Advanced Materials, article 2416717) Wiley / University of Adelaide repository, 2025
  11. Energizer E91 AA alkaline product datasheet, newer edition (Form EBC-1102Q; undated, hosted on a University of Houston course page) Energizer