Release of the world's first lithium-ion secondary battery with high heat resistance

©Nikkei BP "Nikkei xTECH Special" First published: March 25 to April 24, 2020

Data utilization is essential when addressing social issues or improving work efficiency. If one wishes to use data effectively, they must be collected from all possible areas. However, places where IoT devices can be installed are limited. The newly released high-heat-resistance Li-ion battery, the “EnerCera” battery series, from NGK Insulators, Ltd. (hereafter referred to as NGK) may solve this problem. With its unprecedented operating temperature up to 85 degrees Celsius(*), realized by utilizing its proprietary ceramic technology, its application for IoT devices may likely extend to extreme conditions, such as for automotive or industrial uses.

*July 15, 2020 – NGK has successfully raised the maximum operating temperature of its coin-type "EnerCera Coin" battery up to 105 degrees Celsius.

Vice President and General Manager of ADC Division, Electronics Business Group, NGK Insulators Mr. Iwao Ohwada

IWAO OHWADA Vice President
General Manager, Advanced Device Components Div., Electronics Business Group of NGK Insulators, Ltd.

Enabling data to be collected from as many sites as possible – at homes, offices, factories, farms and other social infrastructure – is one of the keys to obtaining valuable information on hand through IoT systems. “New approaches that can promote the sophistication of IoT devices and further expand the applicable sites are in demand”, says Iwao Ohwada, Vice President of NGK.

Every IoT device, as an electronic device, requires a power source to operate built-in sensors and wireless communication functions. It is desirable for IoT devices to be small and lightweight as they will be attached to equipment or used in facilities with limited space. However, the situations where traditional batteries can be used as a power source for those devices are limited. For example, devices such as Bluetooth LE (for short range) or LPWA networks (for long range) require bulky batteries in order to secure power required for wireless data transmission. This limits where the devices can be installed. In addition, organic materials are used for electrodes for conventional Li-ion rechargeable batteries, which raises concerns over the product life and heat resistance characteristics. Furthermore, in order to install massive numbers of IoT devices, it is essential to manufacture a large number of devices efficiently and at low cost. However, the production of IoT devices using conventional rechargeable batteries gets complicated since it requires the battery to be installed separately at a later stage of the assembly process.

“Semi-solid-state battery”
as a solution

The lack of an efficient power source has been a bottleneck for IoT devices. Developed as a solution to this drawback is NGK’s EnerCera battery series, which are chip-type ceramic rechargeable batteries. The company has commenced the commercial production of the EnerCera Coin type (shaped like a coin battery) and the EnerCera Pouch type (ultra-thin with bending durability).

While following the same principle as Li-ion rechargeable batteries, the EnerCera battery is based on a new concept called “semi-solid-state battery”. With a small amount of organic electrolyte solution infused into NGK’s crystal-oriented ceramic plate, Li-ions and electrons move smoothly within the electrode.

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The unique features of the EnerCera battery make it possible to have the strengths of both the Li-ion rechargeable battery (that is, a small size yet with a large capacity with a constant voltage output) and a capacitor (that is, large current output and constant voltage charging capability which eliminates the need for a charger IC). As no organic materials are used in the electrodes, it has high heat resistance characteristics. The expected life of the EnerCera battery is as long as 10 years. It can be mounted on the printed circuit board by reflow soldering which is suitable for mass production. With all these features, the EnerCera battery can be an optimum power source for various IoT devices.

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Broader IoT applications with improved
heat resistance characteristics

In December 2019, NGK started shipping samples of the high-heat-resistance EnerCera Coin type with a maximum operating temperature of 85 degrees Celsius, which has been improved from the previous 60 degrees Celsius.

While maintaining its high capacity, high power and small size, the high-heat-resistance EnerCera Coin type can retain more than 95% of its capacity after 1,000 charge and discharge cycles at 85 degrees Celsius.

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Two types of the high-heat-resistance EnerCera Coin type are available: “ET1210C-H” (12 mm in diameter and 1.0 mm thick) and “ET2016C-H” (20mm in diameter and 1.6 mm thick). Of these, ET2016C-H has a nominal capacity of 20mAh (when charged at 2.7V), an energy density of 90 mWh/cc, and a peak discharge current of 45mA.

The release of the high-heat-resistant EnerCera Coin type has made it possible to add advanced functions of data collection and transmission to the devices operating in extreme environments such as automobiles, factory automation equipment, and outdoor facilities. For example, “With the EnerCera battery, broader applications such as tire-pressure monitoring systems (TPMS) with an added function to detect road surface conditions, or unwired automotive onboard networks may become feasible” (Ohwada).

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Realization of
maintenance-free IoT devices

In order to install IoT devices in as many sites as possible, it is desirable to have a maintenance-free power source. Furthermore, it is also necessary to create a tough power source with improved environmental durability. The unique features of the EnerCera battery series, that is, large capacity with high power, are perfectly compatible with energy harvesting technology that converts various forms of ambient energy such as light, vibrations and temperature difference into usable electricity.

If a power supply system is built using the EnerCera battery coupled with energy harvesting, an ideal maintenance-free IoT device can be realized, such as one for sending data continuously over a long period of time. Since electricity generated from energy harvesting is normally attainable only at the µW level, its direct application for wireless data transmission has not been possible. However, with the EnerCera battery in use, such micro power can be constantly stored in a cumulative manner and can be collectively discharged in the order of tens of mW when data are needed to be transmitted.

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NGK has also taken up the challenge to further improve the heat resistance characteristics of the EnerCera battery up to 105 degrees Celsius and 125 degrees Celsius, in order to meet the need to be used in places such as those in the vicinity of the engines of automobiles.

Engineers considering the industrial application of IoT or AI probably perceive limitations to the value of information extractable from the available IoT data. They may well think that “data should be able to be collected from more extreme environments”. The EnerCera battery can be regarded as one of the key technologies to be used to obtain information where continuous data gathering was not feasible. Envisaging specific applications, together with its collaboration partners, NGK is working to develop an IoT device using energy harvesting technology with the EnerCera battery.

Mr. Ohwada asserts, “The EnerCera battery is a power source innovation for IoT devices which expands the field of its applications and enables collection of more valuable data from various places. NGK helps design new applications through the full use of the EnerCera battery and will create new business opportunities.”

“EnerCera Coin” high-heat-resistant type (operable at 85°C)

The “EnerCera Coin” high-heat-resistant type (operable at 85°C), mounted on the circuit board of power supply IC

NGK INSULATORS

Contact us about EnerCera

ADC Division, Electronics Business Group TEL+81-(0)52-872-7935 https://www.ngk-insulators.com/en/