Pavel, let me address that statement you made about "cobalt makes the cathode more stable, ie less prone to corrosion and thermal runaway".

This is an area, not uncommon, where published information can be found on both sides of the question regarding the safety of incorporating Cobalt into lithium ion batteries.  Not a big surprise.

Certainly an article supporting that position comes via the Cobalt industry itself:

Lithium-Cobalt Batteries: Powering the Electric Vehicle Revolution - Visual Capitalist

That article is sponsored by Fuse Cobalt.  However......

In general, the higher the energy density of a lithium ion battery subtype, the greater is the risk for thermal runaway and explosion. Cobalt is one of the main factors in lithium ion batteries allowing for those higher energy density subtypes.  See the abstract for the following:

Key Characteristics for Thermal Runaway of Li-ion Batteries - ScienceDirect

An additional article from the Journal of The Electrochemical Society, 2021 168 060516 tends to reinforce that finding: "thermal runaway behaviors can be more generally tied to aspects of lithium-ion cells such as total stored energy and specific energy. We have found a strong linear correlation between the total enthalpy of the thermal runaway process and the stored energy of the cell, apparently independent of cell size and state of charge. We have also shown that peak heating rates and peak temperatures reached during thermal runaway events are more closely tied to specific energy, increasing exponentially in the case of peak heating rates."  The applicable link:

Investigating the Role of Energy Density in Thermal Runaway of Lithium-Ion Batteries with Accelerating Rate Calorimetry (tsn-j.com)

The quote:  "Koch Sascha’s thermal runaway research results[8] show that for every 1 kWh/kg increase in the energy density of the battery, the thermal runaway trigger temperature will decrease by 0.42 ℃. This means that high energy density batteries are more prone to thermal runaway than ordinary batteries" comes from a paper at the 2020 International Conference on Advanced Materials, Electronical and Mechanical Engineering (AMEME).  35554-56214-1-SM.pdf

The bold type was designated by me and not in the original quote.

A quote of interest:  

"Cobalt, not lithium, in and of itself is toxic and unstable. When used in lithium-ion batteries, it provides the risk of thermal runaway, a chemical reaction internal to the battery, regardless of ambient temperature. When a battery containing cobalt degenerates and goes into a state of thermal runaway, it becomes an unmitigated fire that is toxic and cannot be extinguished by water or flame retardants, or contained within its housing. Instead, the fire must be allowed to burn, releasing toxic fumes."

Source:  Cobalt: the toxic hazard in Lithium batteries that puts profit before people and the planet | by The Beam | TheBeamMagazine | Medium

A short review of just what thermal runaway is can be obtained in the following quote:

"Although Li-ion batteries are widely used, there are increasing challenges from the safety perspective as applications have transitioned from Wh consumer devices to MWh systems. High energy density becomes a disadvantage when a cell is operated outside of recommended conditions and failure liberates large quantities of chemical and electrical energy. This release of energy has the potential to generate heat faster than it can be dissipated and can cause a thermal runaway of the cell, creating fire, smoke, and particulate ejecta. Li-ion batteries using metal oxide positive electrode materials possess all the components required for combustion or even explosion once thermal runaway occurs—fuel, oxygen, and an ignition source. Organic electrolyte is the fuel as it is unstable at elevated temperatures and easily ignited once it is exposed to air. Once the positive electrode is exposed to elevated temperatures during thermal runaway, it releases oxygen."  See:

DOE ESHB Chapter 3: Lithium-Ion Batteries (sandia.gov)

Another quote:

"Cobalt is the dangerous compound, not lithium!

When the reactive chemicals of cobalt are expressed, it leads to overheating, fire and thermal runaway. Lithium (Li) is not the compound that presents a current hazard."

Source:  Are Lithium-Ion Batteries Dangerous? | UMA Solar Blog

"The second issue is safety. The safety performance of large-capacity LCO batteries is not optimistic, especially in the condition of full charge extrusion, overheating or overcharging. LCO batteries will tend to explode under these circumstances. Even if using a high-safety lithium titanate as the negative electrode of cobalt titanium battery, LCO will explode violently when overcharged and squeezed."

The associated link:  Lithium Cobalt Oxide (LCO) Battery - LiCoO2 Manufacturer-battery-knowledge | Large Power

In 2017 the FAA conducted a study on different type of lithium ion batteries.  In the conclusion of that study I did find the following quote:

"In general, of all of the lithium-ion cells that were tested, LiFePO4 would be considered the safest cathode material because of the relatively low temperature rise and the resulting low likelihood for thermal runaway to propagate. LiCoO2 and LiMnNi would be considered the most hazardous because of the relatively large temperature rise and high probability for propagation of thermal runaway to adjacent battery cells."

See: Hazard Analysis for Various Lithium Batteries (faa.gov)