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Electronics Manufacturing & Production Handbook 2017


 

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:

  • Addressing safety concerns with Li-ion batteries
    15 November 2017, Uniross Batteries, Power Electronics / Power Management
    Lithium-ion is safe but with millions of consumers using batteries, failures are bound to happen.
  • Production cycle of a sealed lead-acid battery
    15 November 2017, Forbatt SA, Power Electronics / Power Management
    It’s easy when commissioning or simply plugging a battery into the device it is destined for, to overlook all the steps that went into its production. Often the minerals that are used in making a battery ...
  • Board-mounted DC-DC converters
    15 November 2017, Vepac Electronics, Power Electronics / Power Management
    XP Power has introduced the JTD15 and JTD20 series of board-mounted DC-DC converters, which target cost sensitive applications where a compact unit with a wide input range is required. The range is aimed ...
  • Non-isolated switching regulators
    15 November 2017, Arrow Altech Distribution (AAD), Power Electronics / Power Management
    Murata has added a 12 V model to its OKI-78SR series of non-isolated switching regulator DC-DC power converters for embedded applications. The fixed single-output converter offers both tight regulation ...
  • Dimmable LED driver
    15 November 2017, Arrow Altech Distribution (AAD), Opto-Electronics, Power Electronics / Power Management
    The AL1673 from Diodes Incorporated is a high-performance, single-stage LED driver-converter operating in flyback and buck-boost topologies, targeting dimmable LED lighting applications. It operates in ...
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    RS Components has announced availability of a new miniaturised and high-performance vacuum tube technology. The Nutube vacuum tube device was developed by KORG, in cooperation with Noritake Itron Corp., ...
  • LLC resonant controller
    15 November 2017, EBV Electrolink, Power Electronics / Power Management
    Texas Instruments introduced a new inductor-inductor-capacitor (LLC) resonant controller with an integrated high-voltage gate driver that enables extremely low standby power. The UCC256301 provides a ...
  • DC-DC converter runs in CV or CC mode
    15 November 2017, ICORP Technologies, Power Electronics / Power Management
    The A7431 is a wide input voltage, high efficiency step-down DC-DC converter that operates in either constant voltage (CV) or constant current (CC) mode. It provides up to 3 A output current at 125 kHz ...
  • Enabling intelligent energy supply via the smart grid
    11 October 2017, EBV Electrolink, This Week's Editor's Pick, Power Electronics / Power Management
    As the worldwide energy supply model is experiencing a trend towards decentralised supply concepts, smart grids allow the challenges of climate change and liberalised electricity markets to be met.
  • Ensuring a longer battery lifecycle
    11 October 2017, Forbatt SA, Power Electronics / Power Management
    It goes without saying that a battery with a longer lifetime provides economic benefits in terms of lower replacement costs, but a longer lasting battery can prove particularly beneficial for certain ...
  • Combining SiC performance with silicon ruggedness
    11 October 2017, Infineon Technologies, Power Electronics / Power Management
    SiC (silicon carbide) MOSFET-based power switches offer significant system advantages in terms of power density, efficiency and cooling effort due to their much lower losses compared to silicon IGBTs. ...
  • Charging methods to prolong lithium-ion battery life
    11 October 2017, Uniross Batteries, Power Electronics / Power Management
    Charging and discharging batteries is a chemical reaction, but lithium-ion (Li-ion) is claimed to be the exception. Battery scientists talk about energies flowing in and out of the battery as part of ...

 
 
         
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