The battery is the element that supplies the energy necessary for the movement of the bike. The operating principle is based on the transfer of electrons from the anode to the cathode, while at the same time a flow of ions flows from the cathode towards the anode through a conductive element. The flow of electrons generates a continuous electric current; the potential is a function of the combination of the materials that form the battery.
In the case of a lithium battery, the latter material composes the cathode while the anode can be of different materials that characterize the battery type. The batteries are defined by three main characteristics: the chemical, the voltage and the specific energy. This last figure indicates the amount of energy that can be stored in the battery per unit of weight (Wh/kg).
The technological evolution of the batteries in recent decades has been impressive. From the first lead-acid batteries of about 30Wh/kg , the specific energy reached the one currently achievable by lithium ions batteries. The energy density of them is about 150Wh/kg but it varies greatly depending on the elements used as anode and it can reach almost double values.
In addition to the specific energy, there are other important factors that define the characteristics of a battery, these are: the specific power, the charging speed, the useful life cycles, the heat generated, the safety level, and the cost. From 2010 to 2017, the average cost of the lithium batteries for automotive applications has gone from 1000 $/kWh to 250 $/kWh (source Bloomberg). The forecast according to Tesla is to reach 100 $/kWh in the 2020.
Lithium batteries are currently the most used in all fields of application, including electric mobility, but that it is not the arrival point. Batteries with new materials are under development in research centers of the world's leading manufacturers such as LG Chem, Panasonic and CATL.
The first steps are aimed at replacing the Cobalt with less expensive and safer materials, such as Nickel or Manganese. Looking further ahead, the objectives are to replace Lithium with materials based on Sodium, Magnesium, Zinc or Aluminum. For the electric mobility this will lead to batteries with greater autonomy, lower weight, reduced charging times, greater safety of use and reduced cost.