Mercedes-Benz E-Mobility: Battery Lifecycle (Main Image)
  • The second lives of lithium-ion batteries.

  • The second lives of lithium-ion batteries.

    • 17. March 2016
    • E-Mobility
    • Text: Walther Wuttke
    • Illustration: Florian Sänger

    First on the road, then at home: after serving their time in electric vehicles, recycled lithium-ion batteries make ideal stationary energy storage devices.

    Lithium-ion batteries are the untiring driving force behind electric mobility. They deliver their full output on board vehicles for at least ten years. Nevertheless, there always comes a point where a battery makes its last journey and is duly removed from service. But even after completing their automotive stint, there’s still life in these power packs. These batteries are veritable treasure troves of raw materials.

    At Daimler subsidiary ACCUmotive, a rechargeable battery’s second lease of life begins to take shape well before its first active phase. Right from the earliest development stages, recycling is a prime consideration, in addition to avoiding prohibited substances such as lead and chromium VI.

    Recycling and remanufacturing

    In addition, “we consider right from the very early planning phase whether certain materials have proven particularly suitable for recycling purposes in the past”, notes Hartung Wilstermann, Executive Director of ACCUmotive in Nabern, where the batteries for the electrified Mercedes models are developed. In this connection, the batteries are also designed such that they can be opened easily in an expert manner and the components can be replaced easily and without any risks.

    Daimler ACCUmotive: Mr. Hartung Wilstermann

    Hartung Wilstermann, Executive Director, ACCUmotive

    Apart from classic recycling at the end of a battery’s useful life, involving removal of its valuable materials and reprocessing for different applications, decommissioned energy accumulators can also remain in use after being duly examined. With so-called remanufacturing, the battery continues to be used after replacing defective components.

    Cutting costs, protecting the environment

    “This means that it is important for the battery to be designed from the outset in such a manner as to facilitate the replacement of components”, explains Wilstermann. When a battery cannot be repaired because a certain element is not replaceable, this leads to unnecessary and above all costly waste. “This can be avoided by according due consideration to remanufacturing right from the start of the development process”.

    In this way, costs are reduced for customers while at the same time helping to protect the environment. ACCUmotive applies its extensive experience in the field of lithium-ion storage batteries in the development, production and recycling of batteries. “We are the battery manufacturer with the most extensive experience in this field worldwide. The first car with a lithium-ion battery was the Mercedes-Benz S400 in 2009″, Wilstermann points out.”Today, we are already in the fourth generation”.

    ' Most experienced battery manufacturer worldwide '

    Hartung Wilstermann, Executive Director, ACCUmotive

    Nickel, cobalt, copper

    At the end of their service lives, the batteries are treasure troves for recycling purposes. “First and foremost, nickel, cobalt and copper are retrieved from the battery as salts”, explains chemist Barbara Seling. These metal salts are employed in the area of electroplating, for example. The slag which is additionally produced when melting down the batteries is used in road construction – so things really do come full cycle in the truest sense. The plastic is used in energy production. Battery recycling ultimately attains a recycling rate of 70 to 80 percent. “There’s probably potential for a further increase in this figure, but we are already well above the legally prescribed minimum of 50 percent”, explains Wilstermann.

     

    Bonded, screwed, welded

    The batteries are disassembled by trained electricians at specialised companies. ACCUmotive provides each recycling company with disassembly instructions for the respective battery types, which entail differences right from the opening stage of the process. “The batteries are either bonded, screwed or welded, and it is also crucial to know where the dangerous high-voltage areas are located. The batteries from the various manufacturers also differ in this respect”, explains Wilstermann, providing an idea of the challenges facing the companies which venture to tackle these complex energy storage devices.

    Daimler ACCUmotive: Ms. Barbara Seling

    Barbara Seling, Director of Material Laboratory, ACCUmotive

    At Mercedes-Benz the battery forms part of the vehicle’s overall concept and thus needs to be designed differently from model to model. In view of the varying installation space and the different requirements imposed on the energy accumulators, complete standardisation of the batteries, which would further simplify the disassembly process, is not possible.

    Battery recycling involves experts working with high voltages, and thus calls for the very highest safety standards. A single mistake can have fatal consequences. “Protecting the developers and workers is consequently the prime priority during the development phase for a new battery, which lasts a good three years, with prototypes continually being set up and dismantled again”, notes Wilstermann. The same applies to the subsequent processing of batteries after they have completed their active service on board automobiles.

    Recycling rate up to 80%

    Second use: A fresh lease of life for ex-car batteries

    Recycled lithium-ion batteries from electric vehicles make ideal stationary energy storage devices.

    Full power output for ten years

    Lithium-ion batteries are tough and tenacious operators. The energy accumulators developed by Daimler subsidiary ACCUmotive in Nabern and produced in Kamenz deliver their full output for at least ten years on board vehicles.Their capacity drops to around 80 percent on average over this period, requiring them to be replaced. However, with their remaining output capacities the energy accumulators are all set for a second lease of life, and the more such 'decommissioned batteries' enter the market, the greater the impact will be on the overall energy balance.

    Ideal for stationary storage devices

    Instead of providing energy for the drive systems on board automobiles, these batteries will 'operate in a stationary storage device, where the conditions for the batteries are absolutely ideal', explains ACCUmotive's Managing Director Hartung Wilstermann. Compared to a stationary storage device in a cellar in a constant temperature range, batteries are required to operate in a much harsher environment on board vehicles.

    Vehicle batteries ideally suitable

    A prerequisite is that the energy accumulators must be fully intact after their mobile careers, however. To this end, the batteries undergo a thorough examination before embarking on a new career. In addition, not every type of battery is suitable for a second lease of life as a stationary storage battery. 'A hybrid battery honed for power output is less suitable for a second career as a stationary storage battery, for example. The batteries from all-electric vehicles are best suited here', observes Wilstermann.

    Storage devices generating 30 megawatt hours possible

    Daimler is a pioneer in the field of stationary storage batteries. The world's largest second-use accumulator, with an output of 13 megawatt hours, is shortly to go on stream in Lünen. Former ACCUmotive batteries are employed in the accumulator to balance out energy fluctuations in the grid with virtually no losses. The possible scope of applications for stationary storage batteries ranges from private photovoltaic systems in the cellars of private homes to mega-accumulators with a capacity of 30 megawatt hours which can replace entire power stations, if need be.

    Significant growth potential

    These accumulators can also be deployed in the Third World, in place of costly, high-maintenance and polluting diesel plants. According to a study by the German Association for Electrical, Electronic and Information Technologies (VDE), the second use of lithium-ion batteries will harbour 'significant economic and ecological potential, if the market for electric mobility and battery storage devices grows as forecast'. And calculations by the Schaufenster Elektromobilität initiative foresee an 'overall capacity of 20 gigawatt hours entering the energy market' by 2030.

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