LiCoO2 is mature technology. These cells are derated to 4.025V EOC and ultra reliable.
Agreed, the cells should be very reliable. According to GS Yuasa Technologies,
"[GYT] fixed their chemical design at 1999 and did not change. GYT large Li-ion cells [...] have never showed internal short accident through more than 10 years production. (>5000 cells)"
(from a sales pitch to NASA
https://batteryworkshop.msfc.nasa.go...Ion_TInoue.pdf - which also shows the differences between "aerospace-grade" and typical "commercial" Sony cells. These GS Yuasa cells are certainly well engineered).