Lithium-sulfur batteries promise more than double the energy density of today's best lithium-ion cells, using sulfur, one of the most abundant elements on Earth, instead of the cobalt and nickel that make conventional batteries expensive and geopolitically fraught. The chemistry has been known for decades. What's changed in 2025 and 2026 is that commercial cells are finally shipping. Lyten , the San Jose-based company leading commercialization, has already delivered lithium-sulfur cells for drone and defense applications. The company acquired Northvolt's Swedish gigafactory assets in February 2026 and is planning the world's first lithium-sulfur gigafactory in Nevada. This article explains how lithium-sulfur batteries work, why the chemistry is compelling, what the engineering challenges are, and where the technology stands today. AI-generated image Lithium-sulfur pouch cell — the format Lyten ships for drone and defense applications. Credit: AI-generated How Lithium-Sulfur Batteries Work A lithium-sulfur (Li-S) cell uses a sulfur-based cathode and a lithium metal anode. During discharge, lithium ions travel from the anode through the electrolyte to the cathode, where they react with sulfur to form lithium polysulfides, then lithium sulfide (Li2S). The reaction runs in reverse during charging. 313 Wh/kg Lyten Cell Energy Density (C/3 rate) 600 Wh/kg Theoretical Potential at Maturity 50% Weight Reduction vs. NMC 0 Cobalt, Nickel, Manganese, Graphite 500+ Wh/kg Sion Power Licerion (Li-metal, drone) 2027 Lyten Nevada Gigafactory Target Compared to lithium-ion's theoretical maximum of around 200-300 Wh/kg at the cell level, lithium-sulfur's theoretical ceiling is roughly 2,600 Wh/kg (based on the mass of active materials alone). Practical cells won't approach that ceiling because the electrolyte, current collectors, separator, and packaging all add mass. But even at 30-40% of theoretical performance, Li-S cells would roughly double what lithium-ion can achieve. The cathode material is sulfur itself, either in elemental form or as a sulfur composite. Lyten uses 3D graphene , a proprietary carbon scaffold, to host the sulfur particles and improve conductivity and cycle stability. Sulfur is a byproduct of petroleum refining and natural gas processing, making it extremely cheap, roughly sh.10 per kilogram, compared to the cobalt at 0+ per kilogram or nickel at 0+ per kilogram used in NMC cathodes. July 2026 update The Commercial Signal Is Getting Clearer The story has moved since this explainer first ran. Lithium-sulfur is still not ready to replace LFP in mass-market grid storage or NMC in mainstream EVs, but the early market is becoming more concrete. Lyten continues to position its sulfur-based chemistry around domestic materials, lower weight, and non-China supply chains, while Sion Power is pushing high-energy lithium-metal cells for defense and aerospace systems where weight matters more than pack cost. Three facts now matter for buyers. First, Lyten's public roadmap still points to Nevada gigafactory capacity later this decade, with sulfur, lithium metal, and graphene-enabled cathode work kept close to its U.S. manufacturing base. Second, the company has used Northvolt asset deals to add European battery-system and recycling infrastructure, giving it more than a lab-scale story. Third, Sion Power's large-format Licerion line and 2026 defense push show that lithium-metal adjacent chemistries are finding near-term customers in drones, aerospace, and military packs before passenger cars. Best first markets Drones, satellites, defense electronics, and aviation systems can pay for lighter cells before cycle life reaches EV norms. Factory test Pilot yield is no longer enough. The next proof point is repeatable large-format production with stable quality and real warranty data. EV timing The chemistry needs longer cycle life and lower pack integration risk before automakers treat it as more than a specialty option. The practical takeaway is narrower but stronger. Lithium-sulfur has crossed from research promise into commercial sampling and early deployment, especially where every kilogram saved changes the product. The chemistry still has to earn mainstream trust through cycle life, swelling control, electrolyte stability, and manufacturable lithium-metal protection. Until those numbers improve at scale, Li-S is best understood as an emerging premium lightweight chemistry, not a near-term commodity replacement for LFP. Sources reviewed for this update include Lyten's lithium-sulfur technology and battery news pages, Sion Power's 2026 Licerion update, Sion Power's large-format production-line announcement, and recent industry reporting on Li-S factory plans. Why the Anode Matters Lithium-sulfur cells use a lithium metal anode rather than the graphite anode in most lithium-ion cells. Lithium metal has roughly 10 times the theoretical capacity of graphite (3,860 mAh/g vs. 372 mAh/g). But lithium metal is reactive, prone to forming dendrites (needle-like structures that can pierce the separator and cause short circuits), and difficult to handle in manufacturing. Managing the lithium metal anode is the central engineering challenge that separates promising lab results from durable commercial cells. The Polysulfide Shuttle: The Chemistry's Biggest Problem Lithium-sulfur batteries have been known since the 1960s. The reason they have taken 60 years to reach commercialization comes down to one fundamental issue: the polysulfide shuttle. When sulfur reacts with lithium during discharge, it passes through a sequence of intermediate compounds called lithium polysulfides (Li2Sx, where x is 4 to 8). These polysulfides are soluble in the liquid electrolyte. That means they dissolve out of the cathode, drift across the cell, and react with the lithium anode. The process is self-defeating: sulfur slowly migrates out of the cathode and gets consumed at the anode, causing rapid capacity fade. A cell that performs well on the first few cycles can lose 50% of its capacity within 100 cycles. Several approaches exist to suppress the polysulfide shuttle: • Cathode architecture: Confining sulfur inside porous carbon structures (like Lyten's 3D graphene) that physically trap polysulfides near the cathode, limiting dissolution. • Electrolyte engineering: Using electrolyte compositions that reduce polysulfide solubility or promote protective surface films on the lithium anode. • Solid-state electrolytes: A solid electrolyte physically blocks polysulfide migration. Some solid-state Li-S designs show dramatically improved cycle life, though solid-state manufacturing adds its own complexity. • Separator modifications: Coating the separator with materials that chemically block polysulfide passage while allowing lithium ion transport. • Anode protection: Coating the lithium metal anode with artificial SEI (solid electrolyte interphase) layers that resist polysulfide attack and dendrite formation. Lyten's commercial cells achieve adequate cycle life for drones and defense applications, where missions are measured in dozens of cycles rather than thousands. The automotive and grid storage markets, which require 500-1,500 cycles minimum, remain the medium-term target as cycle life improves. Who Is Building Lithium-Sulfur Batteries AI-generated image Battery gigafactory-scale production is the next frontier for lithium-sulfur commercialization. Credit: AI-generated Company Technology Energy Density Status (2026) Lyten Li-S with 3D graphene cathode 313–362 Wh/kg Shipping (drones, defense) Sion Power Li-metal (Licerion platform) >500 Wh/kg Shipping Q3 2026 (mil. drones) OXIS Energy Li-S polymer electrolyte 350–450 Wh/kg Development (aviation focus) NexTech Li-S with ceramic separator 280–320 Wh/kg Pilot production Lyten's February 2026 acquisition of Northvolt's Swedish assets, including the Skellefteå Northvolt Ett facility with 16 GWh of manufacturing capacity, was a significant strategic mov