Without the invention of lithium-ion batteries, the breakthrough of e-bikes might not have been possible. Lithium-ion batteries offer the same energy density and capacity per pound as older battery types such as nickel metal hydride (NiMH) or nickel cadmium (NiCd). Aside from higher capacity and energy density, Li-ion batteries do not develop memory unless fully charged (as can be the case with NiCd batteries) or simply shut down when power is low (as can be the case with NiMH batteries are the case), but that is not the case. Not perfect.
Two newer battery technologies are emerging, and one of them is already being used in some e-bikes. One type is lithium iron phosphate (LiFePO4), which we’ll take a closer look at after examining solid-state batteries, since solid-state batteries have more in common with lithium-ion batteries.
The Electric bike review The team is excited about the new battery technologies, but there are already some interesting things happening with different types of e-bike batteries. Let’s explore them all, shall we?
What is a solid state battery?
A solid-state battery is actually a lithium-ion battery, but with a different name. Why another name? Its construction and the materials used differ slightly. Both batteries have an electrolyte solution. Okay, but what are electrolytes?
Electrolytes are minerals (usually in the form of salts) that can carry an electrical charge. Electrolytes help move the electrical charge that causes a muscle to contract in humans. Think Gatorade.
In a lithium-ion battery, this electrolyte solution is a liquid and helps conduct ions in both the anode (the + or positive end of the battery) and the cathode (- or the negative end of the battery). The anode and cathode are separated by a barrier between the two ends of the battery. The problem with this technology is that if the barrier between the anode and cathode breaks, a chemical reaction can begin that can lead to thermal runaway, a process that causes lithium-ion batteries to catch fire. Additionally, the major component (by volume) in the liquid electrolyte is ethylene carbonate, which is flammable and produces toxic gases when burned.
In contrast, a solid-state battery uses a solid electrolyte throughout the battery. This form of electrolyte is more stable and does not swell due to temperature changes or undergo thermal runaway like traditional lithium-ion batteries.
Aside from the safety benefits that come with a solid-state battery, there are other selling points for this technology. The first and biggest advantage is that a solid-state battery offers higher capacity because there is no need for a thick membrane separating the anode and cathode of the battery. So more charge, same physical space.
How much more energy capacity can a solid-state battery offer over a lithium-ion battery? Unfortunately, that is difficult to say. This is due to the wide range of battery capacities. The technical term for this capacity is called “specific energy” and is expressed in watts/hours per kilogram (Wh/Kg). At the low end, a lithium-ion battery may only offer 75 Wh/kg, but most are between 150 and 200 Wh/kg. In the upper price segment, the current iPhone 14 has a lithium-ion battery with an energy density of 250 Wh/kg.
In comparison, solid state batteries are manufactured that offer 350-400 Wh/kg. Depending on the battery, this is at least twice the specific energy, but possibly four times the energy. .
That means an e-bike with a battery that currently weighs 8 pounds. It would be conceivable to replace it with a battery that weighs half as much but offers twice the capacity.
The second major advantage is that solid-state batteries have a longer lifespan and can therefore be charged and discharged more frequently.
More is good, but that’s not particularly specific, so let’s quantify it a bit. The average lithium-ion battery can be charged about 2000 times. Some manage closer to 3000 cycles. In comparison, a solid-state battery can last up to 10,000 cycles before needing to be replaced.
Solid-state batteries also benefit from significantly shorter charging times, with some batteries able to be 80 percent charged in 10 minutes and 100 percent charged in 15 minutes.
