The RETURN-TO-THE-EARTH BATTERYNTT Device Technology Laboratories


    We have created and verified the operation of a battery that does not adversely affect the soil and living organisms (RETURN-TO-THE-EARTH BATTERY) and whose components are made up of fertilizer ingredients, as a non-toxic, rare-metal-free, and low-environmental-impact battery, by leveraging previous technologies and knowhow in storage batteries underpinning communication infrastructures.

    Going forward, NTT plans to use the battery in creating non-toxic, rare-metal-free sensors, which have potential to create new businesses in areas that emphasize harmony with the environment, such as in soil and moisture sensors, in monitoring of the ecosystem and the soil environment, in detection of phenomena related to flooding, pollution, and weather.

    Background and existing issues

    "Would it be possible to recover all the sensors widely scattered all around us during the "Trillion Sensor Era"—the social revolution brought about by a trillion sensors?"
    With the advancement of IoT, various kinds of sensors are foreseen to be widely scattered around us. Discussions regarding the replacement and recovery of these sensors and their batteries, however, have not been sufficiently held. (Figure 1)

    In the future, the failure to carry out "recovery ⇒ reuse" once sensors have become widespread will pose a major threat to the ecosystem. Sensors and batteries that are difficult to recover will be left uncollected, which can have a major impact on the soil and living organisms. NTT has conceptualized and conducted research and development on the RETURN-TO-THE-EARTH BATTERY that has no adverse effect on the soil and living organisms even if left uncollected, as an underlying technology for solving this issue.

    Advantage of this technology

    • Applying biologically-derived carbon to air electrodes, we designed "batteries that return to the earth" which contain fertilizer components, and confirmed their basic operation.

    Use Scenes

    • These batteries can help to create new business opportunities involving the growth of scattered sensors and non-durable consumer devices (consumables) in places where compatibility with nature is required.
    • Uses include soil moisture sensors for the purpose of optimizing water for large-scale soil cultivation in agriculture, environmental monitoring for ecosystems and soil, and detection of floods, contamination, and weather.

    Explanatory chart

    Technical explanation

    1. The spread of electronic devices has led to the demand for long-lasting and high-output batteries that have thus far used expensive rare metals and hazardous materials. Although safety considerations against combustion and other risks have been made in producing these batteries, leaving them uncollected may cause adverse effects on the soil and living organisms since they contain substances that are not naturally part of the soil environment. To address this issue, we proposed a new battery made completely from low-environmental-impact materials (non-toxic and rare-metal-free). Fertilizer ingredients and biologically derived materials, which are biodegradable and do not have adverse effects on the soil and living organisms, were selected as low-environmental-impact materials. In addition, battery electrodes require a three-dimensional conductive porous structure that allows diffusion of atmospheric oxygen. Since conventional electrodes are made from powdered carbon solidified using fluorine-based resins as binding agents, they release toxic gas upon combustion. And, since they contain materials not found in the soil, they cannot be considered as low-environmental-impact materials. There was a need, therefore, of either a non-toxic binding material or an electrode that does not use binding agents. By pre-processing of biologically derived materials, NTT succeeded in creating a porous carbonized structure and developing a carbon electrode that is free from binding agents.
    2. The RETURN-TO-THE-EARTH batteries we built have only 1/10 the battery capacity of commercial batteries, but we have already confirmed that they can power LED lamps. (Figure 2)
    3. In addition, in order to confirm the effect of the batteries on plants, we conducted a plant damage test based on the fertilizer test method (used batteries were crushed and mixed with soil, then we evaluated the germination of komatsuna.) Results confirmed that our batteries did not adversely affect plant growth, unlike household batteries. We successfully achieved the concept of "return to soil." (Figure 3)
      Further, in order to test the effect of the battery on plants, a "cultivation test on the harmful effects to plants" based on the Fertilizer Certification Act as performed (used batteries were pulverized, mixed with the soil, and germination of Japanese mustard spinach were assessed). Results of the test showed that unlike the commercial battery, the new battery did not adversely affect the growth of the plants, substantiating the concept of "RETURN-TO-THE-EARTH" of the battery (Figure 3).

    Department in charge

    NTT Device Technology Laboratories - Social Device Technology Laboratory

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