Currently, the range and charging speed of electric car batteries are limited by lithium-ion technology, which also poses environmental and supply chain challenges. Lithium is costly, environmentally damaging, and scarce, potentially hindering the widespread adoption of electric vehicles.
As the demand for electric cars grows, developing new lithium-free batteries becomes essential. These batteries must match or exceed current efficiency levels while being more eco-friendly and cost-effective. This challenge drives research into new battery materials and designs, critical for reducing the transport sector's carbon footprint.
DTU researcher Mohamad Khoshkalam has developed a promising material for next-generation batteries: solid-state batteries using potassium and sodium silicates, common minerals found in the Earth's crust. These materials, sourced from everyday rocks, are not sensitive to air and humidity, allowing them to be molded into ultra-thin layers within the battery.
Patented Superionic Material
The newly patented potassium silicate material is economical, environmentally friendly, and abundant, covering over 90% of the Earth's surface. It conducts ions effectively at around 40 degrees Celsius and is moisture-resistant. This facilitates safer, cheaper, and more scalable battery production, as it can occur in open environments at near-room temperatures. Moreover, it eliminates the need for expensive and harmful metals like cobalt, used in current lithium-ion batteries to enhance performance and lifespan.
"The potential of potassium silicate as a solid-state electrolyte has been known for a long time, but in my opinion has been ignored due to challenges with the weight and size of the potassium ions. The ions are large and therefore move slower," says Mohamad Khoshkalam.
Understanding Khoshkalam's discovery requires recognizing the electrolyte's vital role in a battery. The electrolyte, which can be liquid or solid, enables ion movement between the anode and cathode, sustaining the electric current during charging and discharging. Its conductivity hinges on ion mobility, traditionally slower in rock silicates due to their larger size compared to lithium-based electrolytes. However, Khoshkalam's process accelerates ion movement in potassium silicate, enhancing its conductivity.
"The first measurement with a battery component revealed that the material has a very good conductivity as a solid-state electrolyte. I cannot reveal how I developed the material, as the recipe and the method are now patented," Mohamad Khoshkalam continues.
The Battery of the Future
Solid-state batteries are seen as the future by researchers and electric car manufacturers. Recently, Toyota announced plans to release a vehicle with a lithium solid-state battery by 2027-28. However, previous announcements have faced setbacks. Unlike conventional batteries, solid-state batteries use solid electrolytes, allowing ions to move faster, improving efficiency and reducing charging time.
A battery cell can be as thin as cardboard, with ultra-thin layers for the anode, cathode, and electrolyte, enabling more powerful, compact batteries. This can translate to driving up to 1,000 km on a single 10-minute charge. Additionally, solid-state batteries are safer as they lack combustible liquid components.
Yet, significant challenges remain before solid-state batteries reach the market. The technology, although successful in labs, is difficult and costly to scale. Material and battery research is intricate and slow, requiring advanced labs and equipment. Even after 20 years, lithium-ion batteries are still evolving.
Furthermore, new production methods are needed to ensure the ultra-thin layers in battery cells remain intact. While high-pressure techniques work in labs, translating this to commercial batteries is complex.
High-Risk, High-Reward Technology
Solid-state batteries based on potassium and sodium silicates have a low Technology Readiness Level (TRL), indicating a lengthy journey from lab discovery to market implementation. Despite the challenges, Khoshkalam remains optimistic.
"We have shown that we can find a material for a solid-state electrolyte that is cheap, efficient, eco-friendly, and scalable-and that even performs better than solid-state lithium-based electrolytes," he said.
Khoshkalam has patented his discovery and is establishing the start-up K-Ion to develop these components for battery companies. Supported by DTU's Earthbound initiative, K-Ion aims to expedite the transition from lab research to societal impact.
The next step is to create a demo battery to showcase to companies and investors, with a prototype expected in 1-2 years.
