Batteries - Frequently Asked Questions (FAQ)

Lithium-ion cells have important advantages over many other battery technologies. They have a high energy density, which means they can store a lot of energy despite their low weight and small size. They also have no memory effect and can be recharged at any time. Their self-discharge is low, and they allow for many charging and discharging cycles. This makes them particularly well suited for mobile devices and electric vehicles.

The cathode material of a lithium-ion cell influences several important cell parameters. Among other things, it determines the voltage of the cell, as different materials have different electrode potentials. It also influences the capacity, i.e., how much energy the cell can store, as well as the service life and safety, as some materials are more stable and less prone to overheating. The charging and discharging behavior also depends heavily on the cathode material.

Various anode materials are used in lithium-ion cells. Graphite is most commonly used because it can absorb lithium ions well and is stable. In addition, there is lithium titanate, which allows particularly fast charging and discharging processes. Silicon-based anodes are also being researched because they offer a higher capacity than graphite. Each material has different properties in terms of capacity, service life, and charging speed.

Various anode materials are used in lithium-ion cells. Graphite is most commonly used because it can absorb lithium ions well and is stable. Lithium titanate is also used, which allows for particularly fast charging and discharging processes. Silicon-based anodes are also being researched because they offer a higher capacity than graphite. Each material has different properties in terms of capacity, service life, and charging speed.

An overview of the anode (green) and cathode materials (blue) and their electrode potential relative to Li/Li+ is shown in the image.

The voltage of the cell is determined by the difference between the electrode potential of the anode and the cathode. Due to the different voltages, cells with higher voltages generally also have a higher gravimetric energy density (in watt hours per kilogram [Wh/kg]), because the energy content [Wh] depends on the nominal voltage: Nominal voltage [V] x capacity [Ah] = energy content [Wh].

A lithium metal battery uses pure lithium metal instead of a graphite anode. This allows it to achieve a significantly higher energy density, as more lithium ions can be stored. It is often characterized by a lighter design and greater capacity. However, lithium metal batteries are more sensitive to short circuits and overheating, which is why safety measures are particularly important. They are mainly used in special applications and research.

Solid-state batteries are a new type of battery in which the liquid electrolyte is replaced by a solid electrolyte. They are characterized by a higher level of safety, as there is no leaking or flammable liquid electrolyte. They can also achieve higher energy density and are more durable. Solid-state batteries also enable the use of lithium metal anodes, which can further increase storage capacity. They are considered promising for future electric vehicles and mobile devices.

Solid-state batteries are technically promising, but not yet widely available on the market (for EV's). Many large manufacturers and research projects are working on realizing the first commercial products and pilot lines in the next few years. Small series and demonstration applications (e.g., in prototype vehicles or special equipment) are expected around 2026–2028. For a broad market launch in electric vehicles and other everyday applications, many industry analyses assume that solid-state batteries will not be available in large quantities until around 2030 or later, as challenges in manufacturing, costs, and long-term stability still need to be resolved.

Yes, lithium-ion cells have a so-called comfort zone in which they function best. This is usually at temperatures between about 20 °C and 40 °C. Within this range, the cells achieve their maximum performance, service life, and safety. At too low temperatures, capacity and chargeability decrease, while at too high temperatures, the risk of aging or overheating increases. This is why maintaining this temperature range is particularly important for electric vehicles and mobile devices.

Currently, prismatic, cylindrical, and pouch cells are all in use in the industry:

• There are various standardized formats for prismatic cells. One example is the PHEV2 format (91 x 148 x 26.5; height x length x thickness; in mm), which was developed for hybrid electric vehicles.
• In the field of cylindrical cells, the 18650 cell (18 mm diameter and 65.0 mm height) has long been the standard and is currently being replaced in many applications by the 21700 cell (21 mm diameter and 70.0 mm height). These formats have a solid metal outer shell.
• Pouch cells, whose outer shell consists of a polymer bag, come in many different formats, often customized to specific customer requirements. One area of application for pouch cells is mobile phones.

All formats are currently in use in automobiles. A similar trend can also be observed for storage batteries. Each cell format has type-specific advantages and disadvantages. Due to the wide range of applications for lithium-ion cells, all cell formats will continue to be used in the future.

The cobalt used in many lithium-ion cells comes mainly from the Congo in Africa, where it is mined under sometimes difficult working conditions. Cobalt is used as a component of cathodes because it improves the stability and service life of the cells. Due to social and environmental problems, manufacturers are increasingly striving to reduce the cobalt content or switch to alternatives such as nickel-rich cathodes

Lithium is currently considered an important raw material for batteries, and demand is rising sharply due to electric vehicles and energy storage. Although lithium reserves are large worldwide, supply bottlenecks or price increases could occur in the short term because mining and processing take time. In the long term, it is likely that new mining projects, recycling, and alternative technologies will provide sufficient lithium, making a general shortage unlikely.

Lithium-ion cells are considered fundamentally safe when designed, operated, and protected correctly. Their safety is ensured by integrated protection mechanisms such as temperature sensors, current limits, and electronic battery management systems. Risks arise primarily from overcharging, deep discharge, short circuits, or mechanical damage, as these can lead to overheating or fire.

The safety of Li-ion cells is regulated by international norms and standards, e.g.:

• IEC 62133 – Requirements for the safety of rechargeable batteries for transport and use.
• UN 38.3 – Regulations for the transport of lithium batteries, including tests such as shock, vibration, and temperature change.
• UL 2054 / UL 1642 – Safety standards for household and industrial batteries, particularly in the USA.

These standards ensure that cells are mechanically, thermally, and electrically resilient and offer a high level of safety in everyday use.