ATSUGI, Japan, June 9, 2026 /PRNewswire/ -- Semiconductor Energy Laboratory Co., Ltd. (hereinafter referred to as "SEL"), headquartered in Atsugi, Kanagawa Prefecture, has conducted a safety demonstration test using a nail penetration test for lithium-ion rechargeable batteries for consumer applications (hereinafter referred to as "the demonstration"). The demonstration utilized a newly developed cathode active material (*1), Ni-doped lithium cobalt oxide (hereinafter referred to as "LCNO (TM)"), developed by SEL. As a result, the company has in place a lithium-ion rechargeable battery that achieves both fire resistance and high energy density (*2).

1. High-energy-density Lithium-ion Rechargeable Battery Having Fire Resistance

The LCNO (TM) battery, the lithium-ion rechargeable battery newly developed by SEL, has successfully improved its fire resistance without compromising the high energy density characteristic of lithium cobalt oxide (LCO (*3)) batteries.

In a nail penetration test, one of the standard safety tests, SEL's prototype LCNO (TM) battery was confirmed not to ignite. There was no temperature rise on the cell surface, indicating that thermal runaway (*4) did not occur.

Image1: https://cdn.kyodonewsprwire.jp/prwfile/release/M104105/202606030266/_prw_PI1fl_W2rwHY3K.png 

Furthermore, LCNO (TM) has improved discharge energy density per weight of cathode material compared with commercial LCO, enabling high-energy-density lithium-ion rechargeable batteries having fire resistance. The structural stability of LCNO (TM), a cathode active material developed by SEL, is crucial in achieving this performance.

Image2: https://cdn.kyodonewsprwire.jp/prwfile/release/M104105/202606030266/_prw_PI2fl_slx7gJzp.png 

Image3: https://cdn.kyodonewsprwire.jp/prwfile/release/M104105/202606030266/_prw_PI3fl_0Auy3Dsm.png 

2. Newly Developed Cathode Material LCNO (TM) (Ni-doped LCO)

LiCoO2 (LCO), a cathode active material, is known to deteriorate due to repeated charging and discharging. General LCO undergoes a phase transition to the H1-3 phase (*5) around 4.55 V (vs. Li+/Li) during charging (when Li is extracted from LCO). As a result, the CoO2 layers shift, making it impossible to return to its original state (O3 phase) during discharging. This contributes to deterioration in charge-discharge cycles.

SEL's newly developed LCNO (TM) involves not only doping Ni into LCO but also adding Mg. Consequently, Ni and Mg occupy Li sites in LCO with a layered rock-salt structure, thereby supporting the CoO2 layers (layered structure). It has been confirmed that this structure remains stable even in a charged state (when Li is extracted from LCNO). XRD measurements have shown that when subjected to high-voltage charging above 4.6 V (i.e., when a significant amount of Li is extracted), LCNO does not undergo transition to the H1-3 phase but instead changes to a different crystal structure (O3' phase) distinct from the O3 phase.

Thus, the LCNO (TM) battery has high structural stability, contributing to the suppression of deterioration during high-voltage charging and charge-discharge cycles.

SEL is confident that this development will contribute to the realization of a safe and secure society free from fire accidents.

Image4: https://cdn.kyodonewsprwire.jp/prwfile/release/M104105/202606030266/_prw_PI4fl_uTGfU5u7.png 

(*1) Cathode material
A material used to form electrodes for storing electricity. Lithium-ion rechargeable batteries have a cathode and an anode, which are made by mixing active material particles with binders and conductive additives, then coating them onto metal foil.

(*2) Energy density
The amount of electrical energy that can be stored per unit volume or mass.

(*3) LCO
Lithium cobalt oxide, which is mainly used as the cathode material for batteries in devices that require small size, light weight, and high-capacity power, such as mobile devices.

(*4) Thermal runaway
A phenomenon where a battery overheats and becomes uncontrollable. Once this starts, the internal materials react, causing a chain reaction that further increases the temperature, ultimately resulting in ignition.

(*5) H1-3 phase
A type of structure that appears when the crystal structure changes during charging, which has a negative impact on charge-discharge cycles.

Paper information
Communications Materials, 5, 108 (2024)
https://doi.org/10.1038/s43246-024-00543-y 

- Title: Controlling lithium cobalt oxide phase transition using molten fluoride salt for improved lithium-ion batteries
- Authors:
Mayumi Mikami (1), Jo Saito (1), Teruaki Ochiai (1), Masahiro Takahashi (1), Tatsuyoshi Takahashi (1), Yohei Momma (1), Kazutaka Kuriki (1), Rihito Wada (1), Kazune Yokomizo (1), Genki Kobayashi (2), Shinichi Komaba (3) & Shunpei Yamazaki (1)

(1) Semiconductor Energy Laboratory Co., Ltd.
(2) The Institute of Physical and Chemical Research
(3) The Tokyo University of Science

About Semiconductor Energy Laboratory Co., Ltd.
Semiconductor Energy Laboratory Co., Ltd. (Head Office: Atsugi, Kanagawa Pref., Japan) has been practicing a unique business model specializing in research and development since its establishment in 1980.

Business:
R&D
- Transistors and integrated circuits fabricated using crystalline oxide semiconductors, and semiconductor devices composed thereof;
- Materials for batteries, and devices composed thereof; and
- Materials and devices for OLED, and display devices composed thereof.

Prototyping devices using crystalline oxide semiconductors for high-volume-manufacturing feasibility evaluation.

Patenting of inventions and licensing patents.

Official website: https://www.sel.co.jp/en/