The past couple of months have been full of activities. Very inspiring events around Europe, including the Swiss ePrint conference, Battery 2030+ annual meeting and Battery Innovation Days, as well as EU project meetings. Adding some proposal writing and other work, I have realized that it has been a bit too much – and I have forgotten to reserve time to recover.

For this blog text, I was planning to write about self-healing batteries. Which I will do, but I will first use some time to think how self-healing could work for people as well.

Self-healing of people

I got inspired by our project partner who mentioned that he is doing a yoga challenge, practicing each day for 30 days. I tested this also myself in January this year. We had then a lot of COVID restrictions, and it was not possible to travel or go to my regular flamenco class, and I was working remotely. Thus, it was relatively easy to do yoga every day as I was anyway home a lot. It was great, but now it felt too challenging to add this to my calendar. So, I decided to test something else instead, and selected meditation. Since if I do not find 10 minutes to take a daily break, I should really be worried.

I had used the Headspace meditation app already previously but was not currently using it actively. As I like the app and VTT supports us by providing it for free (which is great!), I decided to start using Headspace each day for at least 30 days. Let’s see what will happen! And maybe (hopefully) I will continue after the 30-day challenge as well. In 30 days, it might become a habit already 😊

But practicing meditation is not enough as such. My colleague just reminded me that if I take new responsibilities and start new projects, I need to give up on something else. Otherwise, I’m not able to handle everything (or eventually anything?) properly. This is of course obvious, but so easy to forget when there are so many exciting things happening! Thus, a second decision I made was to give up on my role as the safety delegate of our building. Safety and well-being at work are very important, and I have enjoyed my role as the safety delegate where I have been able, in part, to help to build a better working environment. I do not even remember when I started in this role at VTT. It was several years ago, maybe even more than 15 years! But now it is time to let someone else, with fresh ideas and energy, to take this role.

As a third action point, I will start practicing saying “no”. I won’t promise that I will be very good in it, but currently this is super difficult for me, so it can in any case only get better 😉

Self-healing batteries

Then back to the batteries. Batteries do not last forever. Multiple charging and discharging cycles eventually cause degradation in the battery, which leads to capacity loss. Different battery chemistries have different critical degradation mechanisms. When proceeded far enough, some of the degradation types can even lead to safety issues, such as thermal runaway and fire.

Self-healing batteries are batteries, which contain methods to heal, or prevent, the degradation. This increases both the battery lifetime and safety.

Degradation types in batteries

As there are several different battery types, there are also several degradation mechanisms. Some of the problems include cracking of the electrodes and contact loss at the interfaces. Dendrite growth is also an issue, especially for cells with metallic lithium anodes, but also for graphitic anodes, e.g., at high charging rates. Dendrites are metallic “fibers” of lithium, which start to grow from the anode, and eventually reach the cathode side, leading to a short circuit. Dendrite growth happens often simultaneously with formation of dead lithium, which is inactive lithium that eventually blocks the ion transport. At the same time, active lithium is consumed. I’m especially interested in the dendrites, as finding a way to hinder their growth will enable the utilization of Li-metal batteries with high energy density. And high energy density is needed to increase the range of electric vehicles, and to enable electrification of trucks and eventually maybe even planes.

If you want to read about degradation and self-healing mechanisms in more detail, I advise to read a great paper titled “Self-Healing: An Emerging Technology for Next-Generation Smart Batteries”, by Rekha Narayan, Christel Laberty-Robert, Juan Pelta, Jean-Marie Tarascon, and Robert Dominko.

What is self-healing

There are several types of self-healing mechanisms, which can be integrated into a battery. One of the main ways to differentiate the self-healing methods are autonomous vs. triggered and curative vs. preventive self-healing.

Autonomous self-healing works by itself, without any external input. The input comes either directly from the battery itself, or the method works continuously without any trigger.

Triggered self-healing requires a sensor, which first detects the degradation, and then starts the self-healing reaction when needed. It is controlled by the battery management system, which is the brain of the battery.

Curative self-healing detects a degradation, either autonomically or by sensing, and launches then a method to heal the detected problem. There can be for example a crack in the electrode, and it is possible to release a functional “glue” from embedded microcapsules to heal the crack. Especially silicon anodes are prone to cracks as the material expands and shrinks significantly during charging and discharging.

Preventive self-healing works so that it slows down, or in the best case almost prevents, the degradation. This can be done e.g., by artificial interphases or additives in the electrolyte.

The HIDDEN project

One of the self-healing techniques is to use a liquid crystalline electrolyte, which is one of the methods we are developing in an ongoing EU project called HIDDEN: Hindering dendrite growth in Li-metal batteries. It combines both preventive and curative self-healing, and we are testing the method for batteries with a metallic lithium anode.

Liquid crystals are materials that form a fluid-like self-organized and ordered structure. When using an ionically conducting liquid crystal, we can control the Li-ion transport and guide the Li-ions to deposit smoothly on the metallic anode. This will already slow down the dendrite growth in a preventive way.

In addition, it is possible to heat the liquid crystal above the phase transition temperature where it forms a liquid, disordered phase. We expect this phase change to refresh the interface between the metallic anode and the electrolyte, and break the dendrites, which have been already formed. This is the curative approach.

Cost and benefit?

In healthcare, it is in most cases easier to prevent diseases than to cure them. But some of the diseases cannot be prevented, so we must also develop healing methods. The same applies for batteries. However, in some cases the prevention or healing could be very expensive and/or energy consuming. Since batteries are not humans, it is better to replace a damaged battery with a new one if the cost (either in euros or energy) of the prevention or healing is higher than a new battery. Thus, it is very important to evaluate the cost vs. benefit for all self-healing methods with life cycle analysis. If cannot be healed, the damaged battery needs to be recycled, to circulate the raw material back into use. Since luckily, even though the battery has degraded, the materials have not disappeared anywhere, and can be recovered. Recycling could be even considered as an extreme case of self-healing.

The selection of the self-healing method then depends on the cost. Either it does make sense to add preventive or curative healing methods in the battery, or then the battery materials will be recycled.

There is, however, at least one exception regarding the cost. If the degradation will cause a significant safety risk, but the specific battery type is for some reason needed for an application (e.g., due to ultrahigh energy density, or fast charging), the costly self-healing methods are justified if they can ensure safety. I could also imagine that for some use cases that require extreme safety, such as medical or space applications, the cost of the battery is not as relevant than the safety.

Battery 2030+ initiative

Self-healing is one of the themes under the Battery 2030+ research initiative, and the HIDDEN project is one of the projects in this initiative. I’m so grateful to Prof. Kristina Edström and the core team who wrote the first roadmap and designed the EU calls, and who are now coordinating the whole initiative. I still remember that the idea of self-healing batteries was quite new to me when I first read the call text. But with teamwork with the HIDDEN partners, and by carefully studying the roadmap, we anyway built a successful proposal.

It is great to be part of the Battery 2030+ community and I’m extremely happy that our project was one of the lucky ones to be funded. I have learned so much during the first two years, and we still have one year ahead in the program. One of the best things has been to get to know all the wonderful people who are working with batteries around Europe. There are 100 different organizations under the Battery 2030+ umbrella! Last month, we were finally able also to meet in person in Brussels with all the projects:


As with batteries, it is usually easier to use preventive self-healing methods for people as well. Thus, it is good to be reminded about taking care of ourselves. We can use sensors to follow the signs that indicate that we will soon run out of power, both for batteries and people.

However, we, as humans, can learn to listen to the signs also without any external sensors. I stopped using a smart watch that followed my resting heart rate, running speed and sleeping “quality” as it started to stress me too much if any of those numbers were not as good as I was hoping for. Now I’m running as slow as I want and stop to watch birds or take pictures if I want. And I try to listen to my body to notice if I have not been able to recover enough. This works for me better. But it is also great to have family, friends and colleagues who also remind me if I should slow down a bit. Thank you for being there.