Seventy times faster charging possible for Lithium-ion batteries 

A research team from the Netherlands and the UK have used MAX IV to investigate a material that could make charging of lithium-ion batteries seventy times faster than today. It is a promising development for future electric vehicles and renewable energy.

Batteries have an important role to play in a sustainable society. Lightweight, fast-charging batteries open for further utilisation of electric vehicles and renewable but non-continuous energy sources, which require efficient storage to be competitive. Battery research is focused on two tracks: inventing entirely new battery technologies or further developing the lithium-ion batteries that are the most commonly used type of battery today. In the current project, the research team have used MAX IV to investigate a new electrode material for lithium-ion batteries.

“We remain interested in researching lithium-ion batteries over new technologies due to a number of factors,” says Maarten Jager, PhD candidate at the University of Groningen and one of the study’s authors.” The technology readiness level of lithium-ion batteries is very high. In the rechargeable battery market, lithium-ion batteries account for about 67% of the market share. The chemistry involved in lithium-ion batteries is also quite well-known, so there is a more straightforward path to explore new components, which could easily be implemented into the market. New technologies can often be promising, but still take years to be developed enough.”

One of the components of batteries that can be further optimised is the electrode material. The general material for the anode, the negative electrode, in lithium-ion batteries is graphite. 

“Graphite has a relatively good stability, high conductivity, and low cost. However, it also has a number of major drawbacks, which reduce its performance. It has a chemistry that limits the amount of energy each unit can store and is flammable. However, its most important drawback is the amount of power it can deliver. Graphite cannot release and store energy quickly, as it would break the electrode,” says Jager. “One major threshold consumers have for choosing an electric car is the time it takes to fully charge it at a fuel station, often over 20 minutes. Significantly bringing down this charging time without compromising battery life or storage capacity is impossible with graphite. Our experiments show that by replacing graphite with copper niobate, we can, without compromising, charge the battery 70 times faster than graphite.”

The copper niobate the researchers used in their experiment is a special so-called mixed crystal phase copper niobate containing five different crystal structures. It is the first time this type of copper niobate is investigated as a battery electrode material. Generally, so-called pure phase materials containing only one crystal structure have been thought to be the best alternative for batteries, but the new results challenge this idea.

Read more on MAX IV website

BESSY II: How pulsed charging enhances the service time of batteries

An improved charging protocol might help lithium-ion batteries to last much longer. Charging with a high-frequency pulsed current reduces ageing effects, an international team demonstrated. The study was led by Philipp Adelhelm (HZB and Humboldt University) in collaboration with teams from the Technical University of Berlin and Aalborg University in Denmark. Experiments at the X-ray source BESSY II were particularly revealing.

Ageing effects analysed

Lithium-ion batteries are powerful, and they are used everywhere, from electric vehicles to electronic devices. However, their capacity gradually decreases over the course of hundreds of charging cycles. The best commercial lithium-ion batteries with electrodes made of so-called NMC532 (molecular formula: LiNi0.5Mn0.3Co0.2O2) and graphite have a service life of up to eight years. Batteries are usually charged with a constant current flow. But is this really the most favourable method? A new study by Prof Philipp Adelhelm’s group at HZB and Humboldt-University Berlin answers this question clearly with no. The study in the journal Advanced Energy Materials analyses the effect of the charging protocol on the service time of the battery.

Part of the battery tests were carried out at Aalborg University. The batteries were either charged conventionally with constant current (CC) or with a new charging protocol with pulsed current (PC). Post-mortem analyses revealed clear differences after several charging cycles: In the CC samples, the solid electrolyte interface (SEI) at the anode was significantly thicker, which impaired the capacity. The team also found more cracks in the structure of the NMC532 and graphite electrodes, which also contributed to the loss of capacity. In contrast, PC-charging led to a thinner SEI interface and fewer structural changes in the electrode materials.

Read more on HZB website