The perception in the public domain is that lead acid batteries are old technology. Lithium-ion batteries have a different feel, it's more modern and cleaner, it has 3 to 4 times the energy density and has a longer cycle life. With all this, what are the possible advantages of 150-year-old lead-acid technology? Well, actually, everything is not as it seems, look at the data used in the marketing claims behind the headlines, and then apply some common sense, basic research, and some basic science. You will find that the real story is very different.

The first misunderstanding involves volume and specific energy density. The headline value of 4 to 5 times is only associated with a specific energy density and a limited number of Li-ion battery chemistries, some of which are still not in commercial use. Fig. Figure 2 compares several cathodes for lithium-ion batteries, ranging from about 100Wh/kg for the safest Li-FePO4 chemistry to over 200Wh/kg for the nickel-cobalt-aluminum oxide variant. The schematic diagram of lead-acid battery is as follows:

These values are for single cell level only, not for battery packs or conditions of use. Fig. Figure 3 shows the energy density at the cell and system level for different battery chemistries. When all connectivity, cooling, safety and battery management equipment is fully installed, the energy density of lithium-ion batteries is practically halved.

The battery-level advantage with a specific energy density of 3 to 5 times is reduced to 2 to 3 times. Depending on the lithium cathode chemistry, we can almost see the energy density parity between lithium-ion and lead-acid batteries for fully installed battery systems in some applications.

Another factor, cycle life, is also a source of confusion. How many cycles can a lithium-ion battery perform before the capacity drops below 80% of its nameplate rating? Two, three thousand? Table 1 summarizes the performance and cycle life of different Li-ion cathode materials.