Flow Battery Patents

Flow battery patents cover electrolyte chemistry and concentration optimization; ion exchange membrane selection and treatment; electrode and bipolar plate materials and geometry; stack and system design for power and energy sizing; state-of-charge and state-of-health monitoring and control; and balance of plant including pumps valves heat exchangers and piping — with IP held by established industrial companies, specialized flow battery startups, and national laboratories: MAJOR FLOW BATTERY PATENT HOLDERS: SUMITOMO ELECTRIC INDUSTRIES: 500+; specific VRFB (specific specific all-vanadium redox flow battery VRFB: specific specific V²⁺/V³⁺ negative electrolyte + specific specific VO²⁺/VO²⁺ positive electrolyte from specific specific 1.0-2.0 M VOSO4 in specific specific 2-3 M H₂SO₄ for specific specific 1.25 V negative + specific specific 1.00 V positive = specific specific 1.6 V cell OCV open-circuit voltage from specific specific carbon felt electrode 8-10 mm PAN-based + specific specific Nafion 117 membrane + specific specific carbon bipolar plate for specific specific 75-80% RTE round-trip efficiency at specific specific 4-8h discharge from specific specific Hokkaido 60 MWh Japan grid + specific specific Sendai 1 MW demonstrator + specific specific 50 MWh system Hokkaido Toyako 2022); INVINITY ENERGY SYSTEMS: 100+; specific containerized VRFB (specific specific VS3 module: specific specific 100 kWh modular VRFB from specific specific self-contained ISO containerizable for specific specific multi-MWh configuration + specific specific 20,000+ cycle life 20-year design life from specific specific all-vanadium shared electrolyte cross-contamination-free from specific specific UK/US/Australia installation solar+wind firming); FORM ENERGY: 50+; specific iron-air (specific specific iron-air battery: specific specific Fe anode reversible oxidation-reduction from specific specific Fe→Fe(OH)₂→Fe₂O₃ discharge + specific specific reverse electrolysis charge from specific specific aqueous alkaline KOH electrolyte for specific specific rust→iron→rust for specific specific $20/kWh target 100h+ discharge at specific specific multi-day grid storage from specific specific 1 MW pilot Glenwood Minnesota 2023 + specific specific West Virginia 1.3 GW contract 2024); PRIMUS POWER (EZCELL): 100+; specific single-flow ZnBr₂ (specific specific zinc-bromine single-flow: specific specific ZnBr₂ aqueous electrolyte no membrane from specific specific Br₂/ZnBr₂ positive + specific specific Zn/ZnBr₂ negative from specific specific single-tank non-membrane for specific specific low-cost no membrane from specific specific ABS plastic tank electrodes for specific specific EZCell 250 kWh scalable for specific specific US DOE commercial demonstration); PACIFIC NORTHWEST NATIONAL LABORATORY (PNNL): 300+; specific organic aqueous flow (specific specific viologen/ferrocyanide: specific specific methyl viologen MV negative + specific specific ferrocyanide Fe(CN)₆⁴⁻ positive in specific specific neutral pH NaCl+KOH electrolyte for specific specific non-toxic non-flammable from specific specific molecular tuning redox potential for specific specific R-MV 100% capacity retention 1000+ cycle); LARGO CLEAN ENERGY; VOILA ENERGY; CEL-TEK: 200+ combined VRFB.

Flow battery electrolyte chemistry innovations improving energy density and stability; ion exchange membrane innovations reducing crossover and improving conductivity; and electrode and bipolar plate design innovations for improved power density and corrosion resistance represent three core flow battery innovation domains: ELECTROLYTE CHEMISTRY PATENTS: SUMITOMO; PNNL; LARGO; UNL (UNIV. NEBRASKA); HARVARD: specific flow electrolyte (specific specific VRFB electrolyte stabilization: specific specific high-concentration 2.0 M V²⁺ in specific specific 3 M H₂SO₄ from specific specific solubility stabilizer from specific specific phosphoric acid H₃PO₄ 0.05 M additive for specific specific precipitation prevention at specific specific 0°C from specific specific H₂SO₄ freezing point depression for specific specific -10°C cold storage at specific specific 40% SOC from specific specific 50 kWh utility VRFB winter Alaska operation; specific specific organic anthraquinone AQDS: specific specific 9,10-anthraquinone-2,7-disulfonic acid from specific specific negative electrolyte from specific specific E°=-0.09 V vs. SHE at specific specific pH 0 for specific specific >95% capacity retention 1000 cycles vs. specific specific bromine positive at specific specific Harvard Kanan group; specific specific manganese electrolyte: specific specific Mn²⁺/Mn³⁺ positive from specific specific H₂SO₄ for specific specific 1.4 V higher potential vs. specific specific VO²⁺ from specific specific cheaper Mn vs. specific specific V₂O₅ raw material for specific specific $50/kWh target); MEMBRANE PATENTS: FUMATECH; GORE; CHEMOURS/DUPONT; SOLVAY; NATIONAL ENERGY TECHNOLOGY LAB NETL: specific flow membrane (specific specific sulfonated polyethylene sulfone SPES: specific specific sulfonation H₂SO₄+SO₃ from specific specific polyethylene sulfone for specific specific <10 mΩ·cm² area resistance at specific specific 40°C + specific specific <1 mL/day/cm² vanadium crossover from specific specific 85 μm thickness vs. specific specific Nafion 117 183 μm 3× thinner at specific specific 40% cost reduction; specific specific sPEEK sulfonated polyether ether ketone: specific specific concentrated H₂SO₄ sulfonation from specific specific DS 1.4 degree of sulfonation for specific specific 1 mΩ·cm² + specific specific chemical resistance in specific specific 1.5 M VOSO4 3M H2SO4 from specific specific >3,000h stability test; specific specific asymmetric PEM: specific specific gradient structure from specific specific dense top layer 10μm + specific specific porous support for specific specific low resistance + specific specific low crossover vs. specific specific homogeneous Nafion tradeoff); ELECTRODE AND BIPOLAR PLATE PATENTS: SUMITOMO; CHEMOURS; MERSEN; PORVAIR; JARI: specific flow electrode (specific specific thermal activation carbon felt: specific specific PAN carbon felt from specific specific 1400°C N2 + specific specific 400°C air oxidation from specific specific -C=O carboxyl + specific specific -OH hydroxyl surface group from specific specific surface wettability contact angle 120°→20° for specific specific electrolyte wetting at specific specific >95% fiber coverage for specific specific >80% electrode utilization from specific specific kinetics enhancement VO2+/VO²⁺ exchange current density i0 10× increase; specific specific graphite-polymer composite bipolar plate: specific specific 80 wt% graphite flake + specific specific 20 wt% PVDF or specific specific polypropylene compression molded at specific specific 200°C for specific specific <10 mΩ·cm² contact resistance + specific specific <10^-3 cc/cm²/min permeability + specific specific chemical resistance in specific specific H2SO4+VOSO4 for specific specific >10,000h lifetime vs. specific specific titanium plate 10× cost).

Flow battery stack design innovations optimizing hydraulic resistance and current distribution; electrochemical state-of-charge SOC monitoring patents for accurate charge management; and long-duration energy storage LDES system-level patents including thermal management and hybrid integration represent three additional flow battery innovation domains: STACK DESIGN PATENTS: SUMITOMO; REDFLOW; VANITEC; LARGO; ESS INC: specific flow stack (specific specific flow field design: specific specific serpentine+interdigitated hybrid from specific specific carbon composite bipolar plate for specific specific uniform electrolyte distribution ±5% current density variation across specific specific 2000 cm² active area from specific specific CFD computational fluid dynamics optimized channel width 1-3 mm + specific specific land width 1-2 mm + specific specific inlet/outlet manifold for specific specific <0.3 bar pressure drop at specific specific 80 mL/min flow at specific specific 50 kW stack; specific specific electrolyte pump optimization: specific specific electrolyte flow rate / specific specific stack current density ratio from specific specific stoichiometric excess factor λ=2-5 for specific specific 100% utilization + specific specific pump efficiency η>75% from specific specific centrifugal pump at specific specific <5% parasitic power at specific specific 75 kW stack for specific specific >85% system RTE; specific specific frame gasket sealing: specific specific EPDM+PTFE composite from specific specific compressed 0.2-0.5 mm for specific specific <1 mL/day/cell electrolyte leak at specific specific 0.5 bar max pressure from specific specific thermal expansion coefficient matching for specific specific -20°C→60°C from specific specific frame material CNC milled PVDF or specific specific injection-molded PP for specific specific >5,000h lifetime); SOC MONITORING PATENTS: SUMITOMO; MIT; U WASHINGTON; BATTELLE: specific SOC monitoring (specific specific OCV measurement SOC: specific specific open-circuit voltage measurement at specific specific sample cell bypass from specific specific Nernst equation E = E° + (RT/nF)ln[V5+][V2+]/[V4+][V3+] for specific specific direct SOC from specific specific coulometric efficiency at specific specific 1 mA reference cell; specific specific in-situ UV-Vis: specific specific optical fiber + specific specific 760 nm absorbance from specific specific VO²⁺ chromophore for specific specific 0-100% SOC at specific specific ±2% accuracy from specific specific in-line electrolyte flow cell for specific specific real-time SOC without specific specific sample bypass; specific specific conductivity+density sensor: specific specific AC impedance 100 Hz from specific specific 4-electrode conductivity for specific specific H₂SO₄+VOSO4 composition at specific specific vanadium oxidation state inference for specific specific SOC±5% from specific specific low-cost sensor at specific specific <$100 vs. specific specific UV-Vis $1,000+ sensor); LONG-DURATION STORAGE SYSTEM PATENTS: FORM ENERGY; ESS INC; AMBRI (LIQUID METAL); ANTORA ENERGY: specific LDES system (specific specific iron-air 100h+ LDES: specific specific iron pellet bed reactor from specific specific 5-20mm Fe pellet in specific specific KOH electrolyte for specific specific reversible Fe→FeOH₂→Fe₂O₃ rusting for specific specific $20/kWh at specific specific 100h+ at specific specific MWh→GWh from specific specific <40 g CO₂/kWh lifecycle from specific specific no critical mineral dependency + specific specific domestic iron ore; specific specific thermal energy storage TES+ORC LDES: specific specific Antora Energy tungsten carbide thermal storage from specific specific >2000°C from specific specific RE electricity for specific specific supercritical CO2 sCO2 ORC turbine 350 kW→5 MW block for specific specific 100+ h at specific specific $10/kWh levelized from specific specific no degradation thermal storage medium).

Flow battery startup IP strategy must understand that Japanese industrial companies (Sumitomo) and national laboratories (PNNL, MIT) hold significant foundational VRFB IP; recognize that novel electrolyte chemistries — particularly organic, aqueous, and iron-air chemistries — offer genuine whitespace; appreciate that the membrane and electrode materials supply chain creates both IP and commercial moats; and understand the distinct market and IP considerations for long-duration energy storage LDES beyond 8 hours: FLOW BATTERY STARTUP IP STRATEGY: UNDERSTAND THE FLOW BATTERY IP LANDSCAPE: SUMITOMO DOMINATES VRFB: Sumitomo Electric (500+) holds the most significant VRFB commercial IP and has the longest field deployment track record — any all-vanadium flow battery startup should perform detailed FTO against Sumitomo; PNNL AND MIT HOLD ORGANIC/AQUEOUS IP: PNNL (300+) and MIT (100+) hold significant organic aqueous flow battery IP including AQDS anthraquinone and viologen/ferrocyanide chemistry — important for any non-vanadium aqueous startup; FORM ENERGY IRON-AIR IS NEWER SPACE: Form Energy (50+) is developing the iron-air battery for multi-day storage — less dense patent landscape, genuine whitespace in iron-air anode design, electrolyte management, and air electrode structure; ZINC-BROMINE IS LESS PROTECTED: Primus Power (100+) EZCell single-flow zinc-bromine is a focused portfolio — ZnBr₂ no-membrane design offers some whitespace for novel electrode or electrolyte additive chemistry; WHEN TO PATENT IN FLOW BATTERIES: NOVEL ELECTROLYTE CHEMISTRY WITH MEASURED ENERGY DENSITY, STABILITY, AND COST: specific novel electrolyte system (specific specific active species + specific specific solvent + specific specific concentration + specific specific additive) with specific measured volumetric energy density Wh/L at specific specific SOC operating range + specific specific capacity retention % per cycle over specific specific 1,000+ cycles + specific specific raw material cost $/kWh at specific specific energy density vs. specific specific vanadium 1.0 M 25 Wh/L $120/kWh baseline or specific specific AQDS negative+ferricyanide positive 3.4 Wh/L neutral pH baseline — measured multi-cycle stability data at realistic cell level (not just half-cell) is essential to distinguish from prior art electrolyte compositions; NOVEL MEMBRANE WITH MEASURED RESISTANCE AND CROSSOVER: specific novel membrane material (specific specific polymer backbone + specific specific functionalization + specific specific crosslink or specific specific orientation) with specific measured area resistance mΩ·cm² at specific specific temperature + specific specific ion crossover mol/cm²/day in specific specific representative electrolyte + specific specific chemical stability hours at specific specific operating conditions vs. specific specific Nafion 117 or specific specific Fumatech FKS reference membrane; NOVEL ELECTRODE TREATMENT WITH MEASURED KINETICS AND UTILIZATION: specific novel electrode activation or functionalization (specific specific treatment conditions + specific specific functional groups created) with specific measured exchange current density i0 mA/cm² for specific specific redox reaction + specific specific electrode utilization % at specific specific flow rate and specific specific current density vs. specific specific thermal activation PAN carbon felt or specific specific graphite baseline; LDES SYSTEM PATENTS: Long-duration energy storage (>10h) is a priority area for DOE LDES Council; filing PCT applications for novel LDES chemistries and systems can protect against international competition in this fast-growing grid storage category; § 101: electrochemical hardware (electrode, membrane, stack structure, pump system) = fully patent-eligible; SOC algorithm alone = potential Alice risk; anchor SOC algorithm claims to specific sensor measurement hardware + specific pump control actuator hardware; KEY FTO CHECKLIST: Sumitomo 500+ VRFB V²⁺/V³⁺ and V⁴⁺/V⁵⁺ 1.0-2.0 M VOSO4 H₂SO₄ carbon felt Nafion 117 75-80% RTE 60 MWh Hokkaido; PNNL viologen/ferrocyanide neutral pH NaCl/KOH 1000+ cycle non-toxic; Harvard AQDS 9,10-anthraquinone-2,7-disulfonic acid -0.09 V vs. SHE >95% capacity 1000 cycle; Form Energy iron-air Fe/FeOH₂/Fe₂O₃ KOH $20/kWh 100h+ multi-day; Primus EZCell ZnBr₂ single-flow no membrane $150/kWh 250 kWh.