Shulou(Shulou.com)11/24 Report--

Wood, an insulator as we know it, can also be used to make batteries.

Swedish battery maker Northvolt recently announced a joint development agreement with Finnish forestry company Stora Enso to make batteries from lignin-based hard carbon, which is derived from renewable wood from Nordic forests.

These batteries will become 100% recyclable products.

Northvolt, a battery maker, is a new energy company founded in 2016 by giants such as Volkswagen and Siemens. Although it is not long since its establishment, it has become a star enterprise in Europe.

In March, Northvolt announced that it would build a new superbattery factory in the northern German state of Holstein, becoming the first factory outside Sweden. Two months later, Northvolt began shipping, becoming the first European company to supply power batteries to carmakers.

This is obviously competing for jobs with Ningde era, Panasonic and LG New Energy. It is reported that Northvolt plans to go public within two years, and the company is now valued at $12 billion. Northvolt aims to have a 25 per cent market share in Europe by 2030, with annual production capacity to reach or exceed 150GWh deployed in Europe.

Northvolt focuses more on renewable energy and lower carbon emissions than traditional battery manufacturers. This time the partner Stora Enso, is a comprehensive forest products company, the main products are forest products, paper and packaging paper.

The cooperation between the two sides, aimed at reducing the carbon footprint and production costs, attracted a lot of attention as soon as it was announced.

How to use wood to make batteries? New energy vehicles have been suffering from high-priced raw materials for a long time.

At present, lithium, cobalt and nickel are the main metal elements needed to make batteries in the electric vehicle market. On the one hand, these metal elements have limited resources in the earth's crust, on the other hand, the mining and production cycle of these minerals is long. Superimposed by international factors, the price of battery raw materials remains high.

This has also led to tension in the battery supply chain and rising prices for new cars, such as the price increases just announced by Zero run T03 and smart Genie 1, all due to the high price of raw materials.

Finding new renewable, resource-rich and environmentally friendly alternatives has become a top priority for battery manufacturers.

Wood, a renewable energy, has become the best choice, and the battery produced by wood is mainly derived from lignin.

Lignin is a kind of complex organic polymer, which widely exists in the cells of lignified plants. Lignin is mainly located in the intercellular layer, which is also the part with the highest concentration of cell wall.

Lignin is especially important in the formation of cell wall. after lignin deposition, lignin deposition can increase the thickness of the vessel, improve the hardness and toughness of the vessel, and maintain the smooth transport of nutrients in the vessel.

In addition, lignin can also enhance the mechanical support or compressive strength of cells and promote the formation of mechanical tissue. Lignin can also enhance cell adhesion and is a natural strong adhesive.

Lignin also exists in the by-products of the paper industry. before that, as a waste material, 95% of the lignin was discharged directly into the river in the form of "black liquor" or concentrated and burned.

However, in recent years, many studies have shown that lignin can be used in the preparation of batteries.

Scientists in Poland and Sweden first noticed oxidizing lignin in plants and combining it with a substance called polypyrrole to create multilayer polymer electrodes. The charge density of this electrode can be equal to or better than that of current lithium-ion batteries, up to 70-90mAh/g.

As lignin is a by-product of the paper industry, lignin is cheap and comes from a wide range of sources. Porous lignin-based carbon prepared by simple and mild chemical activation has become a research hotspot in the field of environmental purification, electrocatalysis and energy storage, especially as an anode material for lithium-ion batteries.

02. What else can wood provide for batteries? In fact, in the past decade, many scholars have applied lignin to the research of battery preparation.

For example, using renewable resources and paper industry waste sodium lignosulfonate-lignin into lignosulfonate by sulfonation modification-as dopant and template, finally, polypyrrole / graphene layered nanocomposites with layered structure were prepared by chemical oxidation method, which can be assembled into supercapacitors.

Cellulose nanofibers in wood are also high-quality raw materials for making solid electrolytes.

At present, the electrolytes commonly used in lithium batteries, because they contain volatile liquids, have the risk of fire, and may promote the formation of dendrites and affect the normal performance of the battery. Although some researchers use solid electrolytes made of ceramic materials, the brittleness of ceramic materials can not withstand the pressure of battery charge and discharge.

Last year, researchers at Brown University and the University of Maryland found an alternative to cellulose nanofibers in wood.

The study says that by combining copper with cellulose nanofibers, it can be proved that usually ion-insulated cellulose provides faster lithium ion transport in the polymer chain.

The solid ionic conductor formed by the combination of polymer tube made of wood and copper is 10-100 times higher than that of other polymer ionic conductors.

The researchers say the material has electrochemical stability and can accommodate lithium metal anodes and high-voltage cathodes. It can also be used as an adhesive to encapsulate ultra-thick cathodes in high-density batteries.

In addition, lignin can also be used to prepare carbon materials.

Carbon materials have good electrical conductivity, can be used as electrode active materials in fuel cells and other electrochemical fields, and have broad application prospects in the field of energy storage and conversion.

Industrial lignin has the advantages of low cost, rich sources and high carbon content, so it is a high quality raw material for the preparation of carbon materials. In 2021, researchers at Imperial College London prepared carbon from lignin, an industrial waste by-product, to replace lithium-ion batteries with sodium-ion batteries.

The regulation and control mechanism of striated membrane transport and natural structure of trees in paper factories also provide researchers with innovative ideas.

In 2021, the Wood Industry Research Institute of Chinese Academy of Forestry Sciences, together with research teams from many universities, realized the precise stripping of aggregate thin layer (lamella) in wood secondary cell wall for the first time, and optimized the performance of lithium metal battery.

The separated aggregate thin layer can be used as the interface film of solid electrolyte to solve the problem of lithium ion concentration regulation, which breaks through the technical bottleneck restricting the life of lithium metal battery and increases the battery life by more than 75%.

03. How far is the wooden battery from promotion? Compared with traditional battery materials, the biggest advantage of wooden battery is environmental protection.

Traditional button batteries and ordinary dry batteries contain mercury. When discarded in the natural environment, mercury will slowly seep into groundwater and enter the human body through crops, damaging people's internal organs.

A small button battery is abandoned in nature and can pollute 600000 liters of water, which is equivalent to a person's lifetime water consumption. Rechargeable batteries also contain harmful heavy metal cadmium, which exudates from nature, passes through land and water, and eventually harms the human body.

The raw materials of wooden batteries do not need to use rare metals, which are in tight supply. Organic fiber containing lignin is a pure green environmental protection product, non-toxic, harmless, and non-polluting to the natural environment.

Lignin has a wide range of sources and low cost. Previously, the main source of lignin was the waste water from the pulp and paper industry, so it was also called paper black.

Pulping and papermaking separates about 140 million tons of cellulose from plants every year and gets about 50 million tons of lignin by-products. But the effective use of industrial lignin is no more than 10%. The remaining neglected industrial lignin is a huge "treasure" to be developed and utilized.

It is reported that since 2015, the Stora Enso plant has begun to industrialize the production of lignin with an annual capacity of 50000 tons. Stora Enso is also the world's largest producer of Kraft paper lignin.

And the industrial promotion of wooden batteries will not be too far away.

In 2021, Japanese paper cooperated with Tohoku University in Japan to make a charge accumulator using "cellulose nanofiber (CNF)" with a diameter of 3 nm extracted from the pulp, which was processed into a thin film and clamped with aluminum foil to form an electrode.

Nippon Paper says it plans to build pilot batteries for indoor small drones in 2023 for use in smartphones and small household appliances in 2030, as well as pure electric vehicles.

With the progress of production technology and the optimization and improvement of the performance of wooden batteries, it will be possible for more environmentally friendly wooden batteries to replace lithium-ion batteries.

This article is from the official account of Wechat: Chaodian Lab (ID:SuperEV-Lab). Author: Wang Yu.

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