Inside the "disappearing battery" revolution

Forest-powered supercapacitors could replace batteries in IoT devices and sensors

Swedish startup uses forest-derived lignin polymer to replace toxic metals

S-Power offers quick charging, a long 8-10 year lifespan, and other savings

Swedish startup Ligna Energy hopes its new S-Power technology could solve the unsustainable demand for batteries as demand for indoor environmental sensors, wearables and other IoT endpoints surges.

The company argues that a growing number of these devices don’t actually require built-in energy storage due to the fact that they consume minimal energy and can operate intermittently. Those that can harvest environmental energy, like light, RF signals, vibration and temperature differences, could be among the most suited to this futuristic tech.

Ligna’s flagship S-Power 2S offers 1.2F capacitance, a 2.7V operating voltage, 0.5Ω Equivalent Series Resistance and more than 250,000 charge cycles, but more importantly, this ultra-thin pouch-format cell is designed to be suitable for even the smallest cards and sensors.

IoT devices, like environmental sensors, have spiked demand for batteries

According to the company, its latest S-Power technology is not just small enough to fit into places that conventional batteries would be too large, but it can also charge much more quickly and survive considerably more cycles.

Perfect for products that are expected to be deployed for years maintenance-free, Ligna believes this technology could save enterprises considerable cash in the long term. While a sensor might only cost a couple of dollars, sending a technician to physically change a battery could cost hundreds in logistics, even though the battery itself is relatively cheap.

With large deployments across utility networks, factories, agricultural environments, smart cities and more, the savings realized could be huge.

The core differences come in how supercapacitors store energy compared with conventional batteries – electrostatically, rather than chemically. It makes supercapacitors like S-Power 2S better for short bursts of periodic power, in turn leading to much slower degradation and an extremely long lifespan.

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Natural polymers are enabling extreme ‘battery’ performance – will supercapacitors replace batteries?

Ligna’s tech is based on forest-derived materials – instead of metals like lithium, cobalt and nickel – which is seen as more sustainable and less environmentally toxic. Tree- and plant-derived lignin is the core material here, said to be the second-most abundant natural polymer on Earth after cellulose and responsible for how trees stand upright. It’s also readily available as by-product of industries like paper manufacturing.

“It is a conventional supercapacitor in terms of electrical performance, but we have tried to optimise the material stack to remove a few nasty materials and offer a different alternative for our customers,” Managing Director John Söderström explained.

At the same time, research into energy-harvesting technologies could align with these next-gen supercapacitors to reduce charging or replacement frequency even further.

By harvesting energy from indoor light, solar, radio, vibrations and heat exchanges, energy trickling into the supercapacitor could drastically improve lifespan.

“When I started at Ligna five years ago, energy harvesting was not widely adopted in wireless electronics,” Söderström added. “What has happened since is that light harvesters have increased efficiency to the point where batteries can be removed even in low-light conditions.”

However, Ligna calls for major rearchitecturing across the entire industry, noting that every single component must be optimized for the smallest possible quiescent current. What it means for the future is likely a new category of products, rather than supercapacitors that can be retrofitted into existing hardware.

The company is now targeting an eight- to 10-year lifespan for its ultra-thin supercapacitors, on track for mass production though not necessarily at the same price points as “some Chinese competitors.”

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