Swedish battery manufacturer Northvolt has announced that it has signed a joint development agreement with Finnish forestry company Stora Enso to produce wood-based batteries using renewable wood from Nordic forests.

Northvolt, a battery manufacturer, is a new energy company founded in 2016 by giants such as BMW and Volkswagen Groups. Although it has not been around long, it has become a star company in Europe. In March this year, Northvolt officially announced that it will build a new super battery factory in the northern German state of Holstein, the first factory outside Sweden. It is reported that Northvolt plans to go public within two years, and the company’s current valuation has reached $12 billion. Northvolt is targeting a 25% market share in Europe by 2030, with an annual installed capacity in Europe reaching 150 GWh or more.

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.

In the current electric vehicle market, the main metal elements needed to produce batteries are lithium, cobalt and nickel. On the one hand, the resources of these metal elements in the earth’s crust are limited; on the other hand, the mining and production cycles of these minerals are long.

The search for new renewable, resource-rich and environmentally friendly alternatives is a top priority for battery manufacturers. Wood, a renewable energy source, may be the best choice so far. 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.

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.

Raw materials for wood batteries need not contain rare metals, which are in short supply. Organic fibers containing lignin are pure green products, non-toxic, harmless and environmentally friendly. Lignin has a wide range of sources and is inexpensive. In the past, the main source of lignin was wastewater from the pulp and paper industry, which is why it was called paper black.

The pulp and paper industry separates about 140 million tons of cellulose from plants each year, recovering about 50 million tons of lignin as a byproduct. However, no more than 10% of industrial lignin is effectively utilized. The remaining neglected industrial lignin is a huge “treasure” to be recovered and utilized. It is reported that since 2015, Stora Enso’s mill has started industrial production of lignin with an annual production capacity of 50,000 tons. Stora Enso is also the world’s largest producer of kraft lignin.

With the advances in production technology, the performance of wood batteries is optimized and improved, and it becomes possible to replace lithium-ion batteries with more environmentally friendly wood batteries.

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