Crab shells: A possible anode for sodium-ion batteries

Researchers are looking to the humble crab shell as a potential energy source for rechargeable battery technology.
Kavita Verma
Freshwater land crab.
Freshwater land crab.


Eating crab or lobster can be challenging as the shells are very tough to crack. Once we've finished our meal, what do we do with all those shells? Typically, they're thrown away without much thought, but scientists have found an interesting way to repurpose them. 

They're taking these shells and turning them into something more useful: a porous material filled with carbon that can be used in various applications such as water filtration and battery storage. 

Recently, a team of researchers has used this crab carbon to create anodes for sodium-ion batteries- an upcoming alternative to lithium-ion chemistries, as ACS stated.

As the amount of lithium metal in the world is limited for making Lithium-ion batteries, researchers have turned to its 'chemical cousins' instead. Earlier, scientists developed a biodegradable zinc-ion battery with the chitin found in crab shells. But these wastes can be turned into hard carbon- a possible anode for sodium-ion batteries.

To find a viable anode for sodium-ion batteries, Yue Zhao, Hongbin Liu, Yun Chen, and Tingli Ma explored combining hard carbon from crab shells with two types of transition metal dichalcogenides (TMDs); tin sulfide and iron sulfide. 

Similar to lithium in composition, the larger size of sodium ions makes them incompatible with traditional lithium-ion battery components such as graphite. However, using these innovative materials makes it possible to create an effective substitute suitable for use within sodium ion cells.

How scientists created crab carbon?

To create their "crab carbon" anode, the researchers heated crab shells to temperatures hotter than a blast furnace. Then this porous material was formed into electrodes with added tin or iron sulfide for enhanced performance. The fibrous nature of these surfaces provided huge surface areas that enabled efficient ion transport and conductivity.

Two separate composites were tested in a model battery and achieved exceptional performance: boasting 200 cycles of endurance with no signs of slowing. 

In an effort to reduce waste, the research could open up possibilities for more sustainable batteries through creative reuse & reclamation.

The study was published in the American Chemical Society on February 28.

Study abstract:

The demand for energy storage devices has increased significantly, and scarce lithium resources limit the sustainable development of lithium-ion batteries. Therefore, alternative sodium-ion batteries, which are rich in the resource may become more competitive in the future market. In this work, we synthesized low-cost SnS2/C and FeS2/C anode materials of sodium-ion batteries which used waste crab shells as biomass carbon precursor. The SnS2 nanosheet and FeS2 nanosphere structures are deposited on the crab shell-derived carbon through simple hydrothermal reaction. Due to the coexistence of transition metal dichalcogenides (TMDs) and crab-derived biomass carbon, the anode material has excellent cycle stability and rate performance. SnS2/C and FeS2/C deliver capacities of 535.4 and 479 mA h g–1 at the current density of 0.1 A g–1, respectively. This study explored an effective and economical strategy to use biomass and TMDs to construct high-performance sodium-ion batteries.