According to New Atlas, lithium-sulfur batteries have five times the energy storage capacity of current lithium-ion solutions, researchers have a strong interest in lithium-sulfur batteries, and a team at the University of Michigan has taken a step toward realizing its real-world potential. The breakthrough hinged on a naturally inspired membrane that overcame stability issues to provide the battery with a "near-perfect" design that would allow it to last more than a thousand cycles.
Nicholas Kotov, head of the research group, said: "There are many reports claiming that lithium-sulfur batteries have hundreds of cycles, but this has been achieved at the expense of other parameters – capacity, charge rate, resilience and safety. The challenge today is to build a battery that increases the cycle rate from the previous 10 cycles to hundreds of cycles and meets a variety of other requirements, including cost. ”
Taking on this challenge, Kotov and his colleagues turned to aramid nanofibers, a nanoscale version of Kevlar fibers, and molded them into elaborate networks that mimic the structure of cell membranes. The material is injected with an electrolyte gel and prevents a common cause of battery failure, which is the growth of dendritic crystals called dendrites forming on one of the electrodes.
However, the benefits of this new membrane go far beyond that. As lithium-sulfur batteries circulate, small particles of lithium and sulfur, known as lithium polysulfides, flow to lithium and damage the capacity of the device. The team solved this problem by integrating tiny, biologically inspired channels into its artificial membrane and adding an electric charge that would repel the particles while allowing positively charged lithium ions to flow freely.
Ahmet Emre, co-first author of the paper, said: "Inspired by the bioion channel, we designed a 'highway' for lithium ions, and lithium polysulfide cannot pass through 'toll stations'. ”
According to Kotov, the result of this so-called ion selectivity is a lithium-sulfur battery with an "almost perfect" design. He said the device has efficiencies close to theoretical limits, while having five times the capacity of a standard lithium-ion battery.
In the real world with fast-charging technology, scientists expect the battery to cycle 1,000 times, which is thought to be a 10-year lifespan. Another fact that benefits the device is that the source of sulfur is more abundant and less problematic than the cobalt used in lithium-ion batteries, while aramid fiber can be taken from old bulletproof vests, making it an overall more environmentally friendly proposition.
Koto said: "The biomimetic engineering of these batteries integrates two scales – the molecular and nanoscales. For the first time, we integrated the ionic selectivity of cell membranes and the toughness of cartilage. Our integrated system approach allows us to solve the top challenges of lithium-sulfur batteries. ”
The study was published in the journal Nature Communications.
Source: cnBeta