This is actually untrue. The chemistry of choice for drone use is not, and never has been LiFePo.
Most of the safety concerns we have with the cells used for ePPG is not the cell chemistry. Rather, it is the safety you nay or may not build into the power delivery system.
Most fires in battery powered machines do not originate from the cell. They are nearly always due to ancillary equipment failure , poor/insufficient current carrying capabilities of wiring and interconnects , shorting to to mechanical failure of insulation etc.
All of the cell types are absolutely capable of supplying currents far exceeding that required to initiate ignition of other materials in case of a short etc.
The current capabilities, and its ability to start fires external to the cell is magnitudes more of a concern that the safety of the cell itself.
Also, those weldless/solderless pack building systems should be ABSOLUTELY AVOIDED. Do NOT consider using them in your PPG project. The contact resistance alone (as they are using what appears to be standard zincated screws as contacts, will be relatively very high. Not to mention thermal issues that will arise from these parts moving all over the place when at higher temps. Just dont do it.
The Tesla packs/cells are perfectly suitable if reconfigured to meet the electrical requirements. However, buying them used is not such a great idea. They are not in service for a reason. The cells are likely at about 60% or less usable life, and a significant reduction in usable capacity.
I have discussed with @Pdwhite in the past about some pack options. I am working on an LTO option, as well as a 26650 cell based option.
I currently work in the automotive industry as a EE. I served 15+ years in the EV industry as a mechanical/manufacturing/electrical engineer with focus being power delivery and traction motors/inverters. I have built motors for Tesla, and have worked closely with cell/battery manufacturers in the development and integration of the packs in to EV’s. I have deep connections in the lithium chemistry cell industry and often get absolutely amazing deals on cells from various manufacturers.
I currently have plethora of various cell types and chemistries I will be testing once the PPG is built. The first two will be Altair Nano LTO cell based, and a MoliCel 26650 based pack.
Also, the first link explaining Li-Ion vs Li-Po is grossly incorrect (as most sources are). Do not use it as a source of valid scientific information in deciding what cell chemistry to use.
I cant stress enough. Dont harp on the cell chemistry much for other than power/energy density concerns. 90% of your focus on safety should be applied to your wiring and interconnects. That is where your primary mode of failure is going to occur.