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Battery tech shrugs off thermal cycling
24 February 2016, Power Electronics / Power Management

Researchers at Stanford University have developed the first lithium-ion battery that shuts down before overheating, then restarts immediately when the temperature cools.

The new technology could prevent the kind of fires that have prompted recalls and bans on a wide range of battery-powered devices, from recliners and computers to navigation systems and hoverboards.

“People have tried different strategies to solve the problem of accidental fires in lithium-ion batteries,” said Zhenan Bao, a professor of chemical engineering at Stanford. “We’ve designed the first battery that can be shut down and revived over repeated heating and cooling cycles without compromising performance.” Bao and her colleagues describe the new battery in a study published in the 11 January issue of the journal Nature Energy.

A typical lithium-ion battery consists of two electrodes and a liquid or gel electrolyte that carries charged particles between them. Puncturing, shorting or overcharging the battery generates heat. If the temperature reaches about 150°C, the electrolyte could catch fire and trigger an explosion.

Several techniques have been used to prevent battery fires, such as adding flame retardants to the electrolyte. In 2014, Stanford engineer Yi Cui created a smart battery that provides ample warning before it gets too hot. “Unfortunately, these techniques are irreversible, so the battery is no longer functional after it overheats,” said study co-author Cui, an associate professor of materials science and engineering and of photon science. “Clearly, in spite of the many efforts made thus far, battery safety remains an important concern and requires a new approach.”

Nanospikes

To address the problem, Cui, Bao and post-doctoral scholar Zheng Chen turned to nanotechnology. Bao recently invented a wearable sensor to monitor human body temperature. The sensor is made of a plastic material embedded with tiny particles of nickel with nanoscale spikes protruding from their surface. For the battery experiment, the researchers coated the spiky nickel particles with graphene, an atom-thick layer of carbon, and embedded the particles in a thin film of elastic polyethylene.

“We attached the polyethylene film to one of the battery electrodes so that an electric current could flow through it,” said Chen, lead author of the study. “To conduct electricity, the spiky particles have to physically touch one another. But during thermal expansion, polyethylene stretches. That causes the particles to spread apart, making the film non-conductive so that electricity can no longer flow through the battery.”

When the researchers heated the battery above 70°C, the polyethylene film quickly expanded like a balloon, causing the spiky particles to separate and the battery to shut down. But when the temperature dropped back down to the same temperature, the polyethylene shrank, the particles came back into contact, and the battery started generating electricity again.

“We can even tune the temperature higher or lower depending on how many particles we put in or what type of polymer materials we choose,” said Bao, who is also a professor, by courtesy, of chemistry and of materials science and engineering. “For example, we might want the battery to shut down at 50°C or 100°C.”

Reversible strategy

To test the stability of the new material, the researchers repeatedly applied heat to the battery with a hot-air gun. Each time, the battery shut down when it got too hot and quickly resumed operating when the temperature cooled. “Compared with previous approaches, our design provides a reliable, fast, reversible strategy that can achieve both high battery performance and improved safety,” Cui said. “This strategy holds great promise for practical battery applications.”


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Further reading:

  • Contenders for the future king of battery technologies
    13 June 2018, S.J. Andrews Electronics, Power Electronics / Power Management
    S.J. Andrews Electronics examines what’s on the horizon in terms of battery chemistries that could replace lead-acid for large-scale storage of electricity.
  • Power efficiency boosted by Sic and GaN technologies
    13 June 2018, Arrow Altech Distribution (AAD), Power Electronics / Power Management
    Texas Instruments’ Sameer Pendharkar looks at how silicon is being superseded when it comes to power supply efficiency.
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    The Genesys+ series of high-power-density programmable DC power supplies from TDK-Lambda includes a 5 kW model with 1U rack height. Utilising digital signal processing technology, these units address ...
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    13 June 2018, RS Components (SA), Power Electronics / Power Management
    The RS Pro range has been bolstered with easily upgradeable power distribution units (PDUs) which give flexibility to retrofit power metering or networked power monitoring cost effectively and with minimal ...
  • 5,5 V step-down power module
    13 June 2018, EBV Electrolink, Power Electronics / Power Management
    Texas Instruments introduced a 5,5 V step-down power module that delivers continuous 6 A output current with up to 95% efficiency. The TPSM82480 DC-DC module integrates power MOSFETs and shielded inductors ...
  • Wireless power development system
    16 May 2018, Power Electronics / Power Management, Telecoms, Datacoms, Wireless
    Under the name 760308EMP-WPT-200W, Würth Elektronik eiSos and Infineon Technologies are offering a 200 Watt development system for wireless power transfer. What makes the development kit special is ...
  • PWM controllers for LED lighting
    16 May 2018, EBV Electrolink, Power Electronics / Power Management
    ON Semiconductor has announced two new QR PSR PWM controllers for LED lighting with power factor control (PFC) function. The dimmable NCL30386 and the non-dimmable NCL30388 provide options for designers ...
  • Reliable, affordable energy storage – the key to unlocking the renewables drive
    16 May 2018, Power Electronics / Power Management
    The power purchase agreements (PPAs) signed recently by state-owned power utility Eskom, ended three years of waiting and uncertainty, and represent a significant step towards a truly sustainable energy ...

 
 
         
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