Although lithium-ion batteries currently power our cell phones, laptops and electric vehicles, scientists are on the hunt for new battery chemistries that could offer increased energy, greater stability and longer lifetimes. One potential promising element that could form the basis of new batteries is magnesium.
Argonne chemist Brian Ingram is dedicated to pursuing magnesium-ion battery research. In his view, magnesium-ion batteries could one day play a major role in powering our future.
Q: Why do we need to look beyond lithium-ion batteries?
A: Lithium-ion batteries meet the needs of many of society’s applications today for personal electronics and electric vehicles. However, as the energy storage landscape continues to evolve into other applications and energy sectors — particularly in terms of decarbonizing our future — energy storage will face new technical and cost challenges that will require us to find cheaper batteries, better supply chains, faster charging rates, discharge over longer periods, improved safety and longer lifetimes. As battery researchers, we need to develop different kinds of batteries for a diversity of applications, allowing markets to select appropriate technologies and enabling better materials supply chains that can today constrain scaleup and lead to higher costs.
Q: What sorts of challenges can magnesium-ion batteries potentially overcome?
A: In the transportation sector, lithium-ion batteries that are currently found in personal vehicles face two challenges. First, the sustainability impacts and limited availability of elements such as cobalt limit their scalability; second, expanding energy storage to long-haul trucks, rail, marine and aviation will require higher energy densities than lithium-ion can provide. Moving beyond lithium-ion batteries to lower cost, more sustainable and higher performance batteries will improve our energy storage options.
Q: What are magnesium-ion’s advantages?
A: Magnesium batteries are a promising energy storage chemistry. Magnesium batteries are potentially advantageous because they have a more robust supply chain and are more sustainable to engineer, and raw material costs may be less than state-of-the-art lithium-ion batteries.
Q: What makes magnesium-ion batteries different from lithium-ion?
A: The theoretical energy density is at least comparable to lithium-ion batteries, and there is the potential to realize a higher energy density than lithium because there are double the electrons for every individual magnesium ion, compared to lithium. Magnesium is also much more abundant than lithium, which can help enable better supply chains.
Q: How do magnesium-ion batteries work?
A: In principle, magnesium-ion batteries function very similarly to current lithium-ion batteries. Magnesium ions are shuttled between a negative anode (typically made of magnesium metal) and a positive cathode, made of a metal-oxide material. This allows electrons to zip around an external circuit and do work for us.
Q: Are there any drawbacks to magnesium-ion batteries? What challenges do they face?
A: Unfortunately, magnesium-ion batteries face several scientific and technical challenges before they will be a commercial competitor with lithium-ion batteries. These challenges almost all stem from the reality that magnesium is a small ion carrying a lot of electric charge. This results in a lot of often unwanted interactions with surrounding materials.
For instance, transfer of magnesium from the electrolyte to solid electrodes requires excess energy and often results in “parasitic” reactions that compete with the process of storing charge, which limits the lifetime of the batteries. Additionally, motion of magnesium through all materials is more sluggish than lithium. Because of this, charge rates are limited. We are still trying to find ways to overcome these hurdles; that’s what research is all about.
Q: What does this mean for the future of magnesium-ion batteries?
A: It’s too soon to tell, but more research will need to be done. Because these abovementioned challenges exist, and because magnesium-ion batteries have so much potential, there’s a lot of uncertainty. There is still work to be done to provide convincing evidence that energy is actually being stored and released by the metal-oxide positive electrode. Our group recently completed a study and suggested actions the scientific community must take to convincingly claim successful energy storage with magnesium ions. In doing so, we have clarified the significant breakthroughs at the Joint Center for Energy Storage Research, elsewhere at Argonne and at other institutions that have been achieved in less than a decade, and we look forward to building on this progress.
Q: Are there other elements in addition to magnesium that we should be looking at?
A: Calcium is a promising material that maintains many of the advantages of magnesium, but on initial studies is proving to be a more mobile ion. We are in early stages in research on calcium, and many open-ended questions and scientific challenges are still being explored.
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