Researchers in Julia R. Greer’s lab at Caltech have developed a new method for creating three-dimensional architected battery cathodes. It has been designed to improve safety, reduce environmental impact, and enhance the performance of future batteries.

The new cathode replaces toxic, expensive, and unethically mined cobalt with lithium iron phosphate (LFP) embedded in a carbon matrix. LFP is much safer and less prone to catching fire or short-circuiting when overcharged.

On its own, LFP isn’t a miracle material; it usually suffers from sluggish performance. But by rethinking the internal architecture of the battery, the team found a loophole.

“We’ve developed a versatile way to make three-dimensional architected battery electrodes from safer materials,” said Yingjin Wang, a graduate student in Greer’s lab. 

“Using lithium iron phosphate, commonly referred to as LFP, combined with a carbon matrix, we eliminated the use of dangerous cobalt while improving the mechanical resilience of the battery,” the first author added. 

3D-architected cathodes

Lithium-ion batteries are the dominant power source for modern mobile devices, electric vehicles, and renewable grids. 

These batteries consist of five core components: an anode (negative electrode), a cathode (positive electrode), a liquid electrolyte to transport ions, a separator to prevent short circuits, and current collectors to harvest electricity. 

While commercially vital, standard designs carry persistent safety risks and performance limitations. To address these flaws, a new development has reimagined battery design, paving the way for less dangerous, more environmentally friendly energy storage that also boosts performance.

Conventional lithium-ion batteries rely on flat, two-dimensional (“planar“) electrodes, but in this new work, the team introduced a three-dimensional, architected cathode produced through 3D printing. 

Moreover, transitioning from a flat design to a 3D-architected battery maximizes the active surface area where chemical energy is converted into electricity.

“We think this is advantageous because you can decouple the solid-state versus liquid-state diffusion distance. The electrolyte is liquid, so as it’s channeling through this architecture, which is like a labyrinth, it has a solid surface available to it anywhere,” Greer explained.

Moreover, the design reduces tortuosity and shortens the physical path that ions must travel between the cathode and separator, thereby increasing the battery’s power density and allowing it to release its stored energy much faster.

Safer alternative

A primary drawback of current lithium-ion batteries is their reliance on cobalt in the cathodes. Cobalt supply chains are plagued by unethical mining practices in remote regions worldwide, and the material itself poses a notable safety hazard due to its tendency to catch fire or short-circuit when overcharged. 

In contrast, lithium iron phosphate is a much safer alternative. Its inherently stable chemical profile makes it far less likely to experience dangerous thermal issues or short circuits.

“LFP by itself is not a new material, but using this additive manufacturing, or 3D-printing, approach to create an architected electrode that doesn’t contain cobalt is a new thing,” Greer said. 

The next major milestone for the researchers is to design a complementary 3D-architected LFP anode, which will create a fully 3D-architected battery that is both energy- and power-dense. 

Achieving this will be a highly complex manufacturing challenge given the early state of the research and the intricate fabrication parameters involved. Ultimately, the team aims to integrate a polymer-based electrolyte to achieve a true solid-state battery.

The study was published in the journal ACS Energy Letters.

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