Off the gas: Trinohex® Ultra reduces gas formation and increases safety in LIBs

Swollen battery

A degraded battery is a dangerous battery. In lithium-ion batteries, a clear sign of degradation is gas formation, which results in a bulging or puffed-up cell. The gas itself can contribute to the degradation, creating a dangerous cycle of gassing, more degradation, more gassing and eventually critical battery failure.

Trinohex Ultra reduces gassing both during cell formation and throughout cycling in two critical ways: it prevents the dissolution of the cathode and it increases the electrolyte’s boiling point.

How a healthy battery works

Lithium-ion batteries store and discharge electricity by shuttling lithium ions from the cathode to the anode and vice versa. The movement of lithium ions creates free electrons (e-) in the anode which creates a charge at the positive current collector. This produces the electrical current that flows from the cell to whatever its powering.

Facilitating that shuttling is the electrolyte solution, which is made of a variety of chemicals. When you form a battery and run the first few cycles, electrochemical reactions happen throughout the electrolyte and on the surfaces of the cathode and anode.

At the cathode, metal oxides combine with lithium ions to form lithium-metal oxide (in this case lithium-cobalt oxide or LiCoO).

CoO + Li+ + e-→ LiCoO

At the anode, the compound LiC6 forms graphite (C6) and lithium ions.

LiC6 → C6 + Li+ + e-

The full reactions look like this:

LiC6 + CoO→ C6 + LiCoO

And this reaction repeats continuously, with the lithium shuttling between the anode and cathode to either pick up or drop off the free electron during charge or discharge.

How a battery fails

As batteries degrade, harmful compounds, like hydrogen fluoride, are produced and attack the cathode’s metal oxides, as shown in the equation below.

CoO + 2HF→ CoF2 + H2O

And now that metal oxide is lost forever reducing the battery’s overall energy capacity and creating cobalt fluoride and water instead. By the way, lithium and water do not mix well.

This attack on the cathode also produces more harmful compounds and gas until eventually the battery fails, sometimes catastrophically.

How Trinohex Ultra helps create a safer, longer-lasting battery

During cell formation, Trinohex Ultra helps form a more robust cathode-electrolyte interphase, which acts as a shield protecting the metal oxides in the cathode from attack by hydrogen fluoride throughout the life of the cell. This robust CEI helps reduce gas formation and maintains battery capacity by slowing the dissolution of the cathode’s metal oxides. See how Trinohex Ultra prevents HF attack on the cathode by forming a robust CEI.

Another way Trinohex Ultra reduces gas formation is by elevating the boiling point of the electrolyte solution. Trinohex Ultra has a very high boiling point at 408°C. Typical chemicals used in electrolyte solutions have boiling points between 55°C and 295°C (source). When Trinohex Ultra is added at just 1% (the recommended saturation) into an electrolyte solution it has shown to increase the boiling point by as much as 14°C and, in doing so, increases the energy required to convert that liquid into a gas.

Gases tend to be more reactive than liquids (and liquids more than solids). The more movement the particles have, the faster they will react, which creates even more reactive gas until the battery fails. So by increasing the boiling point of the overall electrolyte solution, Trinohex Ultra prevents gas reactions from building over the cycle life of the battery, ultimately leading to a safer, longer-lasting battery.

Contact us to learn more about how Trinohex Ultra improves lithium-ion battery safety, cycle life and performance across cathode and electrolyte chemistries.