01
Fire & safety incidents
Moss Landing, Gateway, and Townsite/Boulder City — major grid battery fires have caused significant damage, reinforcing the need for inherently safer chemistry.
Risk: thermal runaway & flammability
Grid-scale
energy storage
reimagined.
The Aqueous Sulfur Battery combines PolyPlus' Water Stable Protected Anode with proprietary aqueous sulfur cathode chemistry — delivering long-duration grid storage that is safer, cheaper, and free from critical minerals.
250+
Patents granted & pending
Low Cost,
High Capacity
Cathode
High Capacity
Cathode
Li₂S from waste H₂S
Non-Flammable
Aqueous
Electrolyte
Aqueous
Electrolyte
High thermal conductivity reduces need for thermal management
High Energy
Density
Density
~250 Wh/kg & 500 Wh/l
Zero
Self-discharge
Self-discharge
from −20°C to 80°C
Aqueous Sulfur Battery
Li-Seawater Battery
Water Stable Protected Anode (PLE™)
Non-Flammable Electrolyte
Robust Supply Chain
EST. 1991
Founded & operating in Berkeley, CA
Aqueous Sulfur Battery
Li-Seawater Battery
Water Stable Protected Anode (PLE™)
Non-Flammable Electrolyte
Robust Supply Chain
EST. 1991
Founded & operating in Berkeley, CA
The challenge
Grid storage has a problem.
Lithium iron phosphate (LFP) dominates grid storage today. But its supply chain and manufacturing base are almost entirely foreign, and LFP demands costly thermal management to operate across temperature extremes.
There's a better way.
02
Supply chain concentration
Aqueous sulfur batteries are built on a secure, domestic supply chain from end to end.
Advantage: Abundant, low cost raw materials
03
Thermal performance limits
LFP degrades rapidly above 45°C continuous and requires active cooling. Performance drops sharply at low temperatures, limiting deployment geography.
Limit: narrow 0–45°C window
04
Cost plateau
Redox flow batteries remain expensive. LFP has commoditized, but cost reduction is slowing. Long-duration storage needs a step-change.
Gap: long-duration economics
The PolyPlus platform
Three solved problems.
One architecture.
The Aqueous Sulfur Battery pairs PolyPlus' Water Stable Protected Anode (PLE™) with a proprietary aqueous sulfur cathode — the only chemistry that is non-flammable, free of critical minerals, and purpose-built for 4–12+ hour grid storage.
01
Layer 01 · Anode
Water Stable Protected Anode
Graphite anode + ceramic solid electrolyte (PLE™) — water-stable, no lithium metal, no thermal runaway, no critical transition metals.
PLE™ technology02
Layer 02 · Separator
Ceramic Solid Electrolyte
Polycrystalline ceramic membrane - a key component of the PLE, enables stable operation in aqueous environments.
Domestic pilot line03
Layer 03 · Catholyte
Aqueous Sulfur Cathode
Li₂Sₙ in aqueous solution — 1,166 Ah/kg (~7× greater than LFP). Synthesized from H₂S refinery waste. Non-flammable, fully recyclable via solution reconstitution.
1,166 Ah/kg · 7× LFPWhy it matters
Safer, cheaper,
mineral-free.
-
🛡️
Inherently non-flammable
An aqueous electrolyte removes the thermal-runaway pathway that drives LFP and NMC grid fires.
-
⚡
~7× the areal capacity of LFP
Dissolved aqueous polysulfides enable unprecedented capacity density and reversible cycling.
-
🇺🇸
Domestic supply chains
No critical minerals — cathode built from essentially-free H₂S refinery waste.
Sulfur cathode
Non-aqueous Li-S always failed. Aqueous solves it.
✗Non-aqueous: Li₂S insoluble → capacity dies every cycle
✓Aqueous: 3,000× improvement in Li₂S solubility
In organic solvents, polysulfides dissolve, migrate, and deposit as insoluble Li₂S — killing capacity. In water, Li₂S is completely dissolved. Aqueous polysulfides enable unprecedented capacity density (mAh/cm²) and reversible cycling.
The anode problem
The PLE™ makes aqueous sulfur possible.
✗Conventional graphite / Li metal: unstable in water
✓PLE™: fully water-stable, graphite-based, scalable
Aqueous sulfur chemistry was previously impossible — conventional anodes corrode instantly in water. PolyPlus invented the PLE™, a ceramic solid electrolyte membrane that fully protects graphite anodes in aqueous environments. No lithium metal · no thermal runaway · no critical transition metals.
Supply chain
H₂S waste stream → ultra-low-cost cathode.
✗LFP: concentrated supply chain
✓Aqueous sulfur: H₂S refinery byproduct
Cathode cost is determined by the reaction of LiOH with essentially-free H₂S refinery waste — significantly below LFP. No critical minerals. High areal capacity reduces copper, aluminum, separator and binder costs. Dissolved cathode is inherently recyclable — just solution reconstitution.
Grid storage platform
Built for the utility grid.
The PolyPlus Li-ion/sulfur platform is designed from the ground up for multi-hour grid-scale battery energy storage systems (BESS) — where safety, cost, and cycle life matter most.
01
Utility-Scale BESS
Multi-hour storage for transmission-connected utility systems, peak shaving, and grid frequency regulation.
Duration: 4–12+ hours
02
Solar + Storage
Behind-the-meter and front-of-meter storage paired with renewable generation for 4–8 hour dispatch.
Pairing: renewable firming
03
Defense & Resilience
Mission-critical energy storage where safety, domestic sourcing, and temperature tolerance are non-negotiable.
Funded: DOE & DoD programs
04
Underwater / Marine
Li-seawater primary batteries for long-endurance AUVs and subsea systems — proven at 10,000 psi.
Proven: 10,000 psi depth
Competitive landscape
How aqueous sulfur compares.
| Technology | Safety | Cost trajectory | Cycle life | Supply chain | Temperature | Status |
|---|---|---|---|---|---|---|
| PolyPlus Aqueous Sulfur | ✓ Non-flammable | ✓ Byproduct of oil refining | ✓ 3,000+ cycles | ✓ US domestic | ✓ −20°C demonstrated | TRL 5–6 |
| LFP | ✗ Fire incidents | ~ Mature, low margin | ✓ 3,000+ cycles | ✗ Concentrated Supply Chain | ~ 0–45°C optimal | Commercial |
| Redox Flow | ✓ Non-flammable | ✗ Remain too expensive | ✓ Very long life | ~ Mixed | ~ Limited | Commercial |
| NMC Li-ion | ✗ Thermal runaway | ~ Declining | ~ 500–1,000 cycles | ✗ Expensive Critical Minerals | ~ Narrow range | Commercial |
| Conventional Li-S | ✗ Flammable | ~ Moderate | ✗ <100 cycles | ~ Mixed | ✗ Polysulfide shuttle | Development |
Technology portfolio
30+ years of
battery innovation.
Founded on the invention of the protected lithium electrode, PolyPlus has pioneered battery chemistries that were previously considered impossible.
PRIORITY PLATFORM
Grid storage · Primary focus
Li-ion / Sulfur Grid Storage
The primary PolyPlus commercial platform. Water Stable Protected Anode (PLE™) + proprietary aqueous sulfur cathode synthesized from H₂S refinery waste. Non-flammable. No critical minerals. 4–12+ hour discharge duration.
Domestic manufacturing
TRL
5–6 / 9
Consumer · Defense
Glass-Protected Li Metal
Solid-state lithium anode laminate bonded to monolithic sulfide glass — doubles energy density vs. Li-ion. First conductive glass separator for rechargeable Li metal batteries.
2× energy density
TRL
4–5 / 9
Marine · Subsea
Lithium Seawater
1,600 Wh/kg · 1,100 Wh/l energy density. 400 Ah batteries tested in deep ocean. Zero self-discharge stored 4 years. Verified by U.S. Navy and major defense primes. Multi-MWh pilot production line.
Unprecedented Energy
TRL
6–7 / 9
Defense · Soldier power
Lithium Air
World-record 800+ Wh/kg verified at US Army CERDEC Aberdeen. Aqueous electrolyte, ambient air cathode — no toxic chemicals. Ideal for weight-critical portable power.
800+ Wh/kg verified
TRL
4 / 9
Core IP
Protected Lithium Electrode (PLE™)
The foundational PolyPlus invention — a Li anode protected by a dense ceramic membrane, enables high energy batteries combining Li metal or Li-ion anodes with water-based cathodes. Edison Gold Award 2012.
TIME 50 Best Inventions 2011
TRL
7 / 9
Facilities
World-class R&D infrastructure.
The PolyPlus facilities in Berkeley, CA have state-of-the-art equipment and capabilities for battery research and development.
Pilot Production Line
A one-of-a-kind multi-station pilot line for fabricating protected lithium electrodes (PLEs) and protected graphite electrodes (PGE™) — designed by PolyPlus engineers, built by a premiere Li-ion equipment manufacturer.
Dry Room & Glovebox Network
Dry room facility for lithium handling, electrode fabrication, and battery assembly — interconnected to a network of state-of-the-art argon-filled gloveboxes.
Electrochemical & Battery Testing
Several 100-channel Maccor battery testers, plus potentiostat/galvanostat systems with impedance-spectroscopy channels for electrochemical analysis.
Glovebox Network
Double- and triple-workstation gloveboxes operating below 1 ppm moisture and 1 ppm oxygen.
Keyence Microscope Suite
High-resolution optical microscope, confocal laser microscope, and a 3D surface-profiling microscope.
Glass Electrolyte Draw Tower
A draw tower for production of continuous ultra-thin sulfide glass electrolyte ribbon.
Key differentiators
Why PolyPlus Wins on
Cost and Safety.
Non-flammable chemistry is not a marketing claim — it is a fundamental property of the aqueous catholyte architecture.
Robust Supply Chain
Li₂S positive electrode is synthesized from waste H₂S — a byproduct of petroleum refining available at near-zero feedstock cost. No critical minerals.
US graphite sourcing
Non-flammable aqueous catholyte
The Li₂S catholyte is water-based. Unlike LFP or NMC cells, there is no organic solvent in the catholyte that can ignite. This is a structural safety advantage, not a design choice.
vs. LFP organic electrolyte → fire risk
Demonstrated −20°C operation
PolyPlus has cycled Aqueous Sulfur cells at −20°C — a meaningful differentiator for grid applications in cold climates where LFP loses substantial capacity.
Cells demonstrated −20°C cycling
Waste-stream catholyte feedstock
H₂S from petroleum refining — typically a waste disposal liability — becomes the feedstock for Li₂S catholyte synthesis. Refinery-scale availability at near-zero cost.
Refinery waste vs. mined critical minerals
Broad patent protection
250+ granted and pending patents covering the core PLE™, aqueous Li-S chemistry, cell architecture, seals, and manufacturing processes. Comprehensive moat.
250+ patents · 34 years of IP
Deep technical team
PhD-led R&D team with 16,000 ft² facility in Berkeley, CA. Pilot line, dry room, Maccor battery testers, argon gloveboxes, SEM/EDAX — a fully equipped battery development operation.
16,000 ft² · Berkeley, CA
Company
Founded on invention.
Built to scale.
PolyPlus Battery Company was founded in 1991 on the invention of the lithium/organosulfur battery at Lawrence Berkeley National Laboratory. For 34 years, PPBC has operated at the frontier of electrochemical science — combining scientific creativity with disciplined execution and a comprehensive IP portfolio.
- 1991PolyPlus founded in Berkeley
Established on the invention of the lithium/organosulfur battery at Lawrence Berkeley National Laboratory.
- 2000sProtected Lithium Electrode (PLE™)
The protected electrode incorporates a water-stable ceramic membrane, enabling lithium anodes for use in aqueous and ambient environments.
- 2011Lithium-Seawater & Lithium-Air
Record-setting energy densities, proven to 10,000 psi. Named one of TIME's 50 Best Inventions of 2011.
- TodayAqueous Sulfur grid storage
Scaling a safe, low-cost, domestic platform for long-duration grid energy storage.
Leadership team
Steven J. Visco, Ph.D.
CEO & CTO · Co-Founder
150+ US patents · internationally recognized lithium battery expert.
May-Ying Chu, Ph.D.
CFO & COO · Co-Founder
30+ years battery R&D management · 28 US patents.
Eugene Nimon, Ph.D.
Director of R&D
70+ publications · 105+ US patents.
Bruce Katz, MSc
Manager, IP & Business Development
25+ years lithium battery R&D and IP · 80+ US patents.
Samantha Miller, MSc MBA
Head, Corporate Development
Cadence · InCarda · Theravance · Nektar · P&G.
Reinhardt Peper, MBA
Advisor
President & CEO, Robert Bosch Battery Systems 2013–2020.
Celina Mikolajczak, MA
Advisor
Panasonic Energy · Lyten · ESS · Uber · Tesla.
Market applications
Purpose-built for
high-value markets.
PolyPlus battery platforms address critical performance gaps across grid energy storage, defense, and marine applications where conventional chemistries fall short.
Get in touch
Ready to build the grid
of tomorrow?
PolyPlus is actively seeking manufacturing partners, licensing discussions, and strategic investors who share our conviction that grid-scale energy storage needs safer, cheaper, and domestically sourced battery technology.