Fast-charging sodium-ion battery uses anodes made from trees

Environment & Technology
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Wood batteries that are better than Lithium Ion? The production of batteries made from wood. -

Fast-charging sodium-ion battery uses anodes made from trees

A month after Natron Energy began its first-of-kind sodium-ion battery mass production, Swedish sodium-ion developer Altris has identified a means of making the lithium-free batteries even more sustainable. Together with partner Stora Enso, it's adapting tree pulp-sourced carbon toward use as an anode material.

A byproduct of wood pulp manufacturing, lignin has long been investigated for possible use as a more sustainable electrode material. Finnish renewable materials company Stora Enso made headlines in 2022 when it partnered up with Swedish battery manufacturer Northvolt toward using its proprietary Lignode material in lithium-ion battery anodes. Stora Enso describes Lignode as a hard carbon material refined from lignin.

By teaming with Altris, Stora Enso looks to go even more sustainable while further localizing the European battery supply chain. As we looked at when Natron Energy kicked off production a few weeks ago, sodium-ion batteries eliminate the need for rare minerals like lithium, cobalt and nickel, relying on abundant sodium that can be sourced locally without harmful mining.

The raw lignin is refined into hard carbon powder that's used to create electrode sheets for use in the battery anode Stora Enso

By swapping the graphite typically used in anode construction with natural byproduct-sourced Lignode, Altris and Stora Enso can further cut reliance on Chinese imports, the source of more than 90 percent of the European Union's graphite, working to secure a local EU supply chain. Stora Enso also says Lignode anodes come with the promise of faster charging and discharging rates.

Stora Enso calls itself one of the largest privately owned forests in the world, owning and leasing over 5 million acres (2 million hectares) of land. It's been processing wood pulp at its mill in Kotka, Finland for over 80 years and extracting lignin on an industrial scale since 2015. It began pilot production of Lignode in 2021 and is now working to expand to commercial scale.

The company points out that 20 to 30 percent of a tree is composed of lignin, making it abundantly available and readily replaceable with sustainable forest management practices, going so far as to say the Lignode-inclusive Altris sodium-ion cells have the potential to become the world's most sustainable battery.

"Bio-based materials are key to improving the sustainability of battery cells," Stora Enso senior VP Juuso Konttinen said in the joint announcement this week. "With Lignode having the potential to become the most sustainable anode material in the world, this partnership with Altris aligns perfectly with our common commitment to support the ambition of more sustainable electrification."

Stora Enso says that it's one of the largest private forest owners in the world, offering a huge raw supply for Lignode sourcing

Over on the other side of the battery cell, Altris makes its cathode out of Prussian white, made from abundant, inexpensive, non-conflict materials like iron, nitrogen, sodium and carbon. Like Natron's Prussian blue, it is free from rare, problematic minerals like lithium and cobalt.

Does a "world's most sustainable" sodium battery with wood pulp-derived anode sound too good to be true? Well, for now it is. Beyond the fact that the ink has barely dried on the collaboration announcement, Altris has yet to begin commercial production and still refers to itself as a sodium-ion battery developer and prototype manufacturer.

Last year, Altris showed a commercial-sized cell with an energy density of 160-Wh/kg, on par with the lithium-iron-phosphate (LFP) batteries used in today's electric vehicles. The cell was developed as part of a research collaboration with Northvolt. Altris CEO Björn Mårlid said at the time the company would target 200-Wh/kg moving forward.

Source: Stora Enso, Altris

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Said to alleviate problems with currently used battery electrolytes, that contain toxic substances like mercury. -

The production of batteries from wood is mainly derived from lignin, a type of complex organic polymer widely found in the cells of woody plants. Lignin is also present in the by-products of the paper industry. In the past, 95% of lignin was discharged directly into rivers as a waste material in the form of “black liquor” or concentrated and incinerated. In recent years, however, several studies have shown that lignin can be used to make batteries. Scientists in Poland and Sweden were the first to find that lignin oxidizes in plants and combines with a substance called polypyrrole to make multilayer polymer electrodes. The charge density of such electrodes can be comparable to or better than that of current lithium-ion batteries, at up to 70-90 mAh/g.

Compared to traditional battery manufacturers, Northvolt is more focused on renewable energy and lower carbon emissions. The partner, Stora Enso, is an integrated forestry company whose main products are forest products like papers. The collaboration between the two parties, which aims to reduce carbon footprint and production costs, attracted a lot of attention after it was announced.

Since lignin is cheap and widely available, lignin-based porous carbons produced by simple and mild chemical activation have become a research focus in environmental remediation, electrocatalysis, and energy storage, especially as anode materials for lithium-ion batteries. The electrolytes currently used in lithium batteries contain volatile liquids that can pose a fire hazard and promote dendrite formation, which affects normal battery performance.

Last year, researchers at Brown University and the University of Maryland found an alternative that uses cellulose nanofibers made from wood. By combining copper with cellulose nanofibers, the cellulose, which is normally ionically insulating, can be shown to allow faster lithium-ion transport in the polymer chain, according to the study. The solid ion conductor formed by a polymer tube made of wood in combination with copper is 10-100 times more conductive than other polymer ion conductors.

Conventional button batteries and ordinary dry-cell batteries contain mercury. When disposed of in nature, mercury slowly seeps into groundwater, enters the human body through plants, and damages human internal organs. One small button battery disposed of in nature can pollute 600,000 liters of water, which is equivalent to a person’s lifetime water consumption. Rechargeable batteries also contain the harmful heavy metal cadmium, which leaches into nature, flows through land and water, and eventually damages the human body.

(Currently I don't know the source link for the above quote, as it was not provided where it was found to be posted.)

The other component - sodium - is abundant, i.e., table salt. That does not even need to be mined, as it can be sourced from the oceans; although there are plenty of salt mines that can provide salt, too.