Ionblox ($60M for developing Li ion battery for EV and eVTOL)

Ionblox is a next-generation energy company that develops high-performance lithium-ion batteries for electric vehicles by combining high-energy electrodes and unique technology. The company was founded in 2017 in Fremont, California, and was previously known as Zenlabs Energy. Ionblox has raised $60 million in total funding to support its growth.

Challenges: EV lithium battery

Lithium batteries are widely used in consumer electronics due to their relatively high energy density. The market for electric cars has grown in recent years. There is a growing demand for batteries with higher energy density and more stable cycling performance.

Silicon oxide (SiOₓ, 0.1≤ x < 1.9, ) can incorporate a relatively larger amount of lithium ions than conventional graphite anodes, Therefore, SiOₓ can exhibit a larger specific capacity. However, it has been observed that SiOₓ has a capacity that fades relatively quickly with cell cycling, which is undesirable for vehicle applications.

The silicon oxide based anodes generally exhibit a large irreversible capacity loss (IRCL) during the initial charge of the cell. Loss of capacity is typically associated with corresponding irreversible changes to the materials during the initial charge of the cell, such as the formation of a solid electrolyte interphase (SEI) layer between the anode active material and the electrolyte. The high IRCL of a silicon oxide based anode can consume a significant portion of the capacity available for the battery’s energy output, resulting in a battery with low energy.

Ionblox Technology

Ionblox develops stable lithium ion batteries with a high energy density for  eVTOL and EVs. Ionblox has developed an advanced silicon based anode that comprises silicon oxide blended with supplementary lithium, graphite, conductive nanocarbon, and a composite binder composed of high tensile strength polyimide and elastic polymer. The combination of this silicon oxide based anode with a high performing cathode and high voltage electrolyte achieves batteries with a high energy density and stable cycle of over 600 cycles.

The diagram below depicts the structure of Ionblox’s lithium ion battery cell.

The structure of Ionblox's lithium ion battery.
The structure of Ionblox’s lithium ion battery.

The battery cell comprises an anode, a cathode, a separator between the two electrodes, and a liquid electrolyte filled in the cell.

  • Anode

The anode comprises an active material blend (78 – 92 wt%), a polymer binder blend (6 – 20 wt%),  and nanoscale conductive carbon additives (1 – 7 wt%), as shown in the diagram below.

The anode composition of Ionblox's lithium ion battery.
The anode composition of Ionblox’s lithium ion battery.

The electrode is formed into a sheet, dried and pressed to achieve the desired density and porosity. The electrode sheets are generally formed directly on a metal current collector (6 to 10 microns thick), such as a thin metal grid or metal foil. For an assembled cell or battery, electrode layers are formed on both sides of the current collector in order to achieve the desirable performance.

The active material blend comprises a majority of silicon oxide (SiOₓ, 0.1≤ x < 1.9, ) particles and graphite (at least 5 wt%). Graphite provides electrical conductivity of the electrode. Silicon oxide is coated with carbon by pyrolyzing organic compositions at high temperatures of 800 to 900 ºC to form a hard amorphous coating. The carbon coating can increase the electrical conductivity and stabilize the silicon oxide with respect to improving cycling and decreasing irreversible capacity loss.

Supplemental lithium, such as elemental lithium or a lithium alloy, is added to the anode to compensate for the large irreversible capacity loss (IRCL) of the anode and improve the cycling performance. US20110111294A1 and US9601228B2 describe the use of supplemental lithium.

Polymer binder blend provides tensile strength and stabilizes the electrode cycling. The polymer binder also provides good adhesion such that the electrode remains laminated to the current collector. Polymer binder blend comprises of at least about 50 wt% high tensile strength polymer, such as polyimide, blended with at least about 5 wt% elastic polymer, such as polyvinylidene fluoride, carboxymethyl cellulose, styrene-butadiene rubber, and lithiated polyacrylic acid.

The following table lists suppliers of polyimide with high tensile strength:



New Japan Chemical Co., Ltd

Rikacoat PN-20; Rikacoat SN-20; Rikacoat EN-20;



AZ Electronic Materials


Ube Industries. Ltd.

U-Varnish S; U-Varnish A;

Maruzen pertrochemical Co., Ltd.

Bani-X (Bis-allyl-nadi-imide)

Toyobo Co., Ltd.

Vyromax® HR16NN

An appropriate amount of nanoscale carbon further stabilizes the cycling performance of the anode. Nanoscale carbon can be carbon nanofibers, carbon nanotubes, or carbon nanoparticles, such as carbon black. US9190694B2 and US9780358B2 describe the use of nanoscale conductive carbon for cycling stability of silicon based anode.

Carbon nanofibers have diameters of less than 250 nm and are commercially available from Pyrograf® carbon nanofibers (Pyrograf Products, Inc.). 

Single wall or multiwall carbon nanotubes are also commercially available from American Elements, Inc. (CA, USA), Cnano Technologies (China), Fuji, Inc. (Japan), Alfa Aesar (MA, USA) or NanoLabs (MA, USA). 

Carbon blacks are commercially available Super-P® (Timcal), Ketjenblack® (Akzo Nobel), Shawinigan Black® (Chevron-Phillips), and Black Pearls 2000® (Cabot).

  • Cathode

The cathode comprises at least 85 wt% active material, at least 0.4 wt% electrically conductive additive, and at least 0.8 wt% polymer binder, as shown in the diagram below.

The cathode composition of Ionblox's lithium ion battery.
The cathode composition of Ionblox’s lithium ion battery.

The electrode is formed into a sheet, dried and pressed to achieve a desired density and porosity. The electrode sheets are generally formed directly on a metal current collector (14 to 20 microns thick), such as a metal foil or a thin metal grid. For an assembled cell or battery, electrode layers are formed on both sides of the current collector in order to achieve the desirable performance.

The cathode active material consists of a mixture of nickel-rich lithium nickel cobalt manganese oxide and (lithium+manganese) rich-lithium nickel cobalt manganese oxide. When paired with the silicon based anode, the mixture provides a high energy density and long cycling stability over a wide voltage range, making it suitable for automotive applications.

Nickel-rich lithium nickel manganese cobalt oxides (N-NMC) alone can provide desirable cycling and capacity properties. The N-NMC is represented by the formula LiNiₘMnₙCoO₂. The amount of nickel influences the selected charge voltage to balance cycling stability and discharge energy density. N-NMC powders are commercially available from BASF (Germany), TODA (Japan), L&F Materials Corp. (Korea), Unicore (Belgium), and Jinhe Materials Corp. (China).

When N-NMC powers are blended with (lithium rich+manganese rich) lithium nickel manganese cobalt oxides (LM-NMC or HCMR®), the cathode has further improved cycling stability with some loss of energy density due to some reduction of average voltage. The LM-NMC is represented by the formula Li₁₊ₘNiₙMnₖCoₕAₚO₂₋ⱼFⱼ, where A is a metal different from lithium, manganese, nickel, and cobalt. A can be Mg, Sr, Ba, Cd, Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y, Nb, Cr, Fe, or V.

LM-NMC are coated with inorganic compositions, such as metal fluorides (AlF₃, MgF₂, CaF₂, SrF₂, or BaF₂), metal oxide (Al₂O₃, Bi₂O₃, B₂O₃, ZrO₂, MgO, Cr₂O₃, MgAl₂O₄, Ga₂O₃, SiO₂, SnO₂, TiO₂, etc.), and metal halide (AlCl₃, AlBr₃, AlI₃, etc.), to increase specific capacity and improve cycling. US9843041B2, US8535832B2, and US8663849B2 describe the stabilization coatings for cathode active materials.

Polymer binders for the cathode can be polyvinylidine fluoride (PVDF), polyethylene oxide, polyimide, polyethylene, polypropylene, polytetrafluoroethylene, polyacrylates, rubbers (e.g. ethylene-propylene-diene monomer (EPDM) rubber or styrene butadiene rubber (SBR)), or copolymers. Polyvinylidiene fluoride  binder provides good results.

Electrically conductive additives can be carbon nanotubes, carbon nanofibers, or carbon nanoparticles such as carbon black.

  • Separator

A separator is located between the anode and the cathode. The separator is electrically insulating while providing for at least selected ion conduction between the two electrodes.

A variety of materials can be used as separators. Commercial polymer separators include the Celgard® line of separator material from Hoechst Celanese, Charlotte, N.C. Ceramic-polymer separators can be stable at higher temperatures and reduce the fire risk. Ceramic-polymer separators are commercially available Separion® by Evonik Industries, Germany and Lielsort® by Teijin Lielsort Korea Co., Ltd. Also, separators can be formed using porous polymer sheets coated with a gel-forming polymer.

  • Electrolyte

Electrolyte provides for ion transport between the anode and cathode during charging and discharging processes. Electrolytes comprise lithium salts, solvent, and fluorinated additives, as shown in the diagram below.

The electrolyte composition of Ionblox's lithium ion battery.
The electrolyte composition of Ionblox’s lithium ion battery.

The concentration of the lithium salts is 1 to 2 M. Suitable lithium salts include lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis(trifluoromethyl sulfonyl imide), lithium trifluoromethane sulfonate, lithium tris(trifluoromethyl sulfonyl) methide, lithium tetrafluoroborate, lithium perchlorate, lithium tetrachloroaluminate, lithium chloride, and lithium difluoro oxalato borate.

The electrolyte contains a non-aqueous solvent to dissolve the lithium salts. The solvent generally does not dissolve the electroactive materials. Appropriate solvents include propylene carbonate, dimethyl carbonate, diethyl carbonate, 2-methyl tetrahydrofuran, dioxolane, tetrahydrofuran, methyl ethyl carbonate, γ-butyrolactone, dimethyl sulfoxide, acetonitrile, formamide, dimethyl formamide, triglyme (tri(ethylene glycol) dimethyl ether), diglyme (diethylene glycol dimethyl ether), DME (glyme or 1,2-dimethyloxyethane or ethylene glycol dimethyl ether), and nitromethane. US8993177B2 describes particularly useful solvents for high voltage lithium-ion batteries.

Fluorinated additives in the electrolyte further improve the performance of batteries with silicon based negative electrode active material. The fluorinated additives can include fluoroethylene carbonate, fluorinated vinyl carbonate, monochloro ethylene carbonate, monobromo ethylene carbonate, 4-(2,2,3,3-tetrafluoropropoxymethyl)-[1,3]dioxolan-2-one, 4-(2,3,3,3-tetrafluoro-2-trifluoro methyl-propyl)-[1,3]dioxolan-2-one, 4-trifluoromethyl-1,3-dioxolan-2-one, bis(2,2,3,3-tetrafluoro-propyl) carbonate, and bis(2,2,3,3,3-pentafluoro-propyl) carbonate.

Ionblox Patent

  • US9166222B2 Lithium ion batteries with supplemental lithium
  • US9601228B2 Silicon oxide based high capacity anode materials for lithium ion batteries
  • US11476494B2 Lithium ion batteries with high capacity anode active material and good cycling for consumer electronics
  • US9190694B2 High capacity anode materials for lithium ion batteries
  • US10411299B2 Electrolytes for stable cycling of high capacity lithium based batteries
  • US11094925B2 Electrodes with silicon oxide active materials for lithium ion cells achieving high capacity, high energy density and long cycle life performance
  • US20220006090A1 Lithium ion cells with silicon based active materials and negative electrodes with water-based binders having good adhesion and cohesion
  • US20200411901A1 Lithium ion cells with high performance electrolyte and silicon oxide active materials achieving very long cycle life performance
  • US10193135B2 Positive electrode active materials with composite coatings for high energy density secondary batteries and corresponding processes
  • US10886526B2 Silicon-silicon oxide-carbon composites for lithium battery electrodes and methods for forming the composites
  • US10020491B2 Silicon-based active materials for lithium ion batteries and synthesis with solution processing
  • US9780358B2 Battery designs with high capacity anode materials and cathode materials
  • US9070489B2 Mixed phase lithium metal oxide compositions with desirable battery performance
  • US10115962B2 High capacity cathode material with stabilizing nanocoatings
  • US10170762B2 Lithium metal oxides with multiple phases and stable high energy electrochemical cycling
  • US9552901B2 Lithium ion batteries with high energy density, excellent cycling capability and low internal impedance
  • US9159990B2 High capacity lithium ion battery formation protocol and corresponding batteries
  • US10553871B2 Battery cell engineering and design to reach high energy
  • US9139441B2 Porous silicon based anode material formed using metal reduction
  • US20130157147A1 Low Temperature Electrolyte for High Capacity Lithium Based Batteries
  • US8928286B2 Very long cycling of lithium ion batteries with lithium rich cathode materials
  • US9083062B2 Battery Packs for Vehicles and High Capacity Pouch Secondary Batteries for Incorporation into Compact Battery Packs
  • US8663849B2 Metal halide coatings on lithium ion battery positive electrode materials and corresponding batteries
  • US8535832B2 Metal oxide coated positive electrode materials for lithium-based batteries
  • US8475959B2 Lithium doped cathode material
  • US8741484B2 Doped positive electrode active materials and lithium ion secondary battery constructed therefrom
  • US8765306B2 High voltage battery formation protocols and control of charging and discharging for desirable long term cycling performance
  • US8993177B2 Lithium ion battery with high voltage electrolytes and additives
  • US9843041B2 Coated positive electrode materials for lithium ion batteries
  • US8916294B2 Fluorine doped lithium rich metal oxide positive electrode battery materials with high specific capacity and corresponding batteries
  • US10056644B2 Lithium ion batteries with long cycling performance
  • US9012073B2 Composite compositions, negative electrodes with composite compositions and corresponding batteries
  • US8277974B2 High energy lithium ion batteries with particular negative electrode compositions
  • US8187752B2 High Energy Lithium Ion Secondary Batteries
  • US8465873B2 Positive electrode materials for high discharge capacity lithium ion batteries
  • US8389160B2 Positive electrode materials for lithium ion batteries having a high specific discharge capacity and processes for the synthesis of these materials

Ionblox Products

The Launch product is designed for eVTOL, drones, and HAPS applications with high power needs at the beginning as well as the end of a mission, normally coinciding with take-off and landing operations. The cell also exhibits high energy density and long cycle life. The dimension of the Launch product is shown in the figure below. The key features and benefits of Launch product are:

  • Cell dimensions: 145 mm x 64 mm x 6 mm;
  • Cell capacity at C/3 rate: 12 Ah;
  • Specific energy at C/3 rate: 340Wh/Kg;  
  • Energy density at C/3 rate: 850 Wh/L;
  • Specific discharge power at 50% SOC from a 12C, 30 s pulse: 3800 W/Kg;
  • Excellent cycle life (100% DOD at 1C-1C rate): > 700 cycles;
  • Voltage range: 4.2 V to 2.5 V;
  • Pre-lithiated SiOₓ anode and 811 NCM cathode; and
  • Low cost.

The Range product is designed for electric vehicles. You can rapidly charge 80% of the entire battery in 10 minutes. For a 300-mile range vehicle, this means you can charge 240 miles in the time it would take for a normal stop at the gas station. The key features and benefits of Range product are:

  • Cell dimensions: 320 mm x 102 mm x 10 mm;
  • Cell capacity at C/3 rate: 50 Ah;
  • Voltage range: 4.2 V to 2.5 V;
  • Specific energy at C/3 rate: 335 Wh/Kg;
  • High capacity SiOₓ anode paired with 811 NCM cathode;
  • Excellent cycle life (100% DOD at 1C-1C rate): > 1,000 cycles;
  • Fast high-rate charge: 80% in 10 min; and
  • Low cost.

Ionblox Funding

Ionblox has raised a total of $60.8M in funding over 3 rounds: a Grant round and two Series B rounds. Their latest funding was raised on Feb 8, 2023 from a Series B round.

The funding types of Ionblox.
The funding types of Ionblox.
The cumulative raised funding of Ionblox.
The cumulative raised funding of Ionblox.

Ionblox Investors

Ionblox is funded by 5 investors, including Lilium, Applied Ventures, Catalus Capital, Temasek Holdings, and United States Council for Automotive Research. Temasek Holdings and Catalus Capital are the most recent investors.

The funding rounds by investors of Ionblox.
The funding rounds by investors of Ionblox.

Ionblox Founder

Sujeet Kumar, Herman Lopez, and Michael Sinkula are Co-Founders.

Ionblox CEO

Sujeet Kumar is CEO.

Ionblox Board Member and Advisor

Sujeet Kumar is board member.

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