Atsugi, JapanJune 9, 2026 /PRNewswire/ — Semiconductor Energy Laboratory Co., Ltd. (SEL), headquartered in Atsugi, Kanagawa Prefecture, Japan, conducted a nail penetration test safety verification (hereinafter referred to as “this verification”) for consumer lithium-ion rechargeable batteries. This verification utilized a new positive electrode active material (*1) developed by SEL—nickel-doped lithium cobalt oxide (hereinafter referred to as “LCNO™”). The results demonstrated that the company has successfully achieved a lithium-ion rechargeable battery that combines flame resistance with high energy density (*2).
1. Lithium-ion rechargeable battery combining flame resistance and high energy density
SEL’s newly developed LCNO(TM) battery, a lithium-ion rechargeable battery, successfully enhances flame resistance while maintaining the high energy density characteristics of lithium cobalt oxide (LCO (*3)) batteries.
In the nail penetration test, one of the standard safety tests, the LCNO(TM) battery prototyped by SEL was confirmed not to catch fire. No temperature rise was observed on the battery surface, indicating that thermal runaway (*4) did not occur.
Furthermore, compared to commercial LCO materials, LCNO(TM) improves the discharge energy density per unit weight of positive electrode material, thereby achieving a lithium-ion rechargeable battery that combines flame resistance and high energy density. The key to this performance lies in the structural stability of the positive electrode active material LCNO(TM) developed by SEL.
2. Newly developed positive electrode material LCNO(TM) (nickel-doped LCO)
LiCoO2 (LCO), used as a positive electrode active material, is known to degrade in performance due to repeated charging and discharging. During charging (i.e., when lithium is extracted from LCO), ordinary LCO undergoes a phase transition to the H1-3 phase (*5) at approximately 4.55V (vs. Li+/Li). This results in displacement of the CoO2 layers, which cannot return to the original state (O3 phase) during discharge, leading to a decline in charge-discharge cycle performance.
SEL’s newly developed LCNO(TM) incorporates not only nickel but also magnesium into LCO. Consequently, nickel and magnesium occupy lithium sites in the layered rock-salt structure of LCO, thereby supporting the CoO2 layers (layered structure). It has been confirmed that this structure remains stable even in a charged state (i.e., when lithium is extracted from LCNO). X-ray diffraction measurements indicate that under high-voltage charging conditions above 4.6V (i.e., when a large amount of lithium is extracted), LCNO does not transition to the H1-3 phase but instead transforms into a different crystal structure (O3′ phase) distinct from the O3 phase.
Therefore, the LCNO(TM) battery exhibits extremely high structural stability, helping to suppress performance degradation caused by high-voltage charging and charge-discharge cycling.
SEL believes that this development will contribute to building a safer and more reliable society free from fire accidents.
(*1) Positive electrode material
Material used to form the electrode for storing electricity. A lithium-ion rechargeable battery consists of a positive electrode and a negative electrode, fabricated by mixing active material particles with a binder and conductive additive, then coating the mixture onto a metal foil.
(*2) Energy density
The amount of electrical energy that can be stored per unit volume or unit mass.
(*3) LCO
Lithium cobalt oxide, primarily used as a positive electrode material in batteries for mobile devices and other applications requiring miniaturization, lightweight design, and high-capacity power supply.
(*4) Thermal runaway
A phenomenon where the battery overheats and enters an uncontrollable state. Once it occurs, internal battery materials react, triggering a chain reaction that causes a continuous temperature rise, potentially leading to combustion.
(*5) H1-3 phase
A type of structure that appears when the crystal structure changes during charging, negatively impacting charge-discharge cycle performance.
——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), and 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. (Headquarters: Atsugi City, Kanagawa Prefecture, Japan) has been practicing a unique business model focused on research and development since its establishment in 1980.
Business scope:
Research and development
——Transistors and integrated circuits manufactured using crystalline oxide semiconductors, and related semiconductor devices;
——Battery materials and related devices; and
——OLED materials and devices, and related display equipment.
Prototype device development using crystalline oxide semiconductors to assess mass production feasibility.
Filing of invention patent applications and licensing of patent rights.
Official website: https://www.sel.co.jp/en/