Turning end-of-life batteries into a valuable material stream

To meet the growing demand for electric vehicles, the world’s lithium-ion production capacity has increased tenfold. With vehicles from the first production wave coming to the end of their life, a tidal wave of spent batteries is set to hit the automotive market.

Redwood Materials is a start-up battery recycling company racing to solve the problem before it begins. Redwood’s CEO and founder, J.B. Straubel, has a deep understanding of the issue, being the co-founder and the previous Chief Technical Officer of Tesla, one of the world’s largest battery manufacturers.

“We will be ready with solutions at the right scale to help make sure no EV batteries end up improperly disposed of and, instead, will turn this problem into a valuable materials stream returning to the battery production supply chain,” writes Redwood on their website.

There are two main ways to deactivate lithium-ion batteries.

The first, called pyrometallurgy, involves burning the batteries to remove unwanted organic materials and plastics. One of the most common pyro methods is smelting.

The second method, called hydrometallurgy, involves soaking the cells in strong acids to dissolve the metals. One of the most common hydro methods is leaching.

Using a combination of both techniques, Redwood can safely deactivate the lithium-ion batteries and recover the valuable materials.

At Redwood, technicians begin the process by wearing reflective silver heat suits that cook the batteries in converters to separate the metals. Rather than using the conventional smelting method, Redwood uses the residual energy from the batteries to drive the conversion process. The remaining material is metal alloy and is filtered through a hydro process to recover the individual compounds.

According to Straubel, the process can recover between 95 and 98 per cent of a battery’s nickel, cobalt, copper, aluminium, and graphite, and more than 80 per cent of its lithium.

Once the battery has been broken down into its basic ingredients, Redwood then reintegrates the battery into the manufacturing process.

“We’re going to build a remanufacturing ecosystem for all those batteries,” says Straubel. “Material can get reused almost infinitely. There’s no inherent degradation to the metal atoms.”

Li-Cycle, one of the largest lithium-ion recyclers in North America, utilises a different approach to recycling than Redwood. Using leaching alone to refine the battery, the company skips the smelting process entirely. Through this method, almost the entire battery is converted into raw materials.

A significant part of Li-Cycle’s success is the design of its recycling facilities. Through a “hub and spoke” approach, batteries are preprocessed at different sites, before the resulting battery material (also referred to as “black mass”) is fed back to the centre hub, where it is refined into usable battery-grade chemicals. These chemicals are then re-inserted into the supply chain, closing the loop between the end-of-life and manufacturing phases.

“We don’t produce any meaningful amounts of waste,” states Tim Johnston, co-founder of Li-Cycle. “We don’t produce any meaningful amount of air emissions, we don’t produce any wastewater, and everything is done at a low temperature. The footprint is very small.”

However, the process of recycling these batteries comes with a wide range of technical, political, and economic challenges including the lack of specialised facilities, the expensive and rigorous shipping restrictions, and the absence of material recovery in mind during the manufacturing process.

“[vehicle batteries weren’t] designed for repair, reuse or upgrade. The key focus at the time was to build it cheaply and quickly”, reports Carlton Cummins, Chief Technical Officer of Acceleron. “The way batteries are designed today, everything is welded and glued together, and the assumption is that at the end of usage it is disposed of.”

To help recycling companies such as Redwood Materials and Li-Cycle, Cummins and his team have designed a hard-shell battery container that compresses the battery and links the cells via a removable circuit.

“We had to reinvent how you assemble batteries with something that is designed for reuse as well as recycling.”

Battery recycling is a vital part of converting the world to clean energy systems. Despite the challenges that face the industry, companies such as Redwood Materials and Li-Cycle are paving the way to a greener future.

Source: Wired | The Race to Crack Battery Recycling – Before It’s Too Late

8 December 2020

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