Development of a solid-state secondary battery

01/15/2019

Motivation

  • Lithium ion secondary batteries use electrolytic solution, which may lead to accidents such as ignition occurring due to short-circuiting caused by mechanical shock.
  • If the electrolytes are entirely composed of solids, the batteries can be made extremely safe.
  • We started to develop a solid-state secondary battery, seeking further applicability as energy storage components by allowing flexibility in sizing.

Issue

  • If the dielectric part of MLCC (ceramic condensers) is replaced with a solid electrolyte, would it function as a battery?
  • Aligning the sintering behavior of different materials is the challenge.

Results and Findings

  • We succeeded in developing an oxide-based, solid-state secondary battery with charge/discharge characteristics and good reliability test results.

Background of the issue

  • NAMICS has already developed the prototyping technology of MLCC, ceramic condensers.​​
  • Our development started based on the hypothesis that replacing the dielectric part of MLCC with a solid electrolyte and an active material would enable us to produce solid-state secondary batteries.
  • Commercialization of a solid-state secondary battery will enable safety, long life, and rapid charging.

Concept of the development​​

  • Solid electrolytes are divided into oxide-type and sulfide-type. The sulfide-type has a high ionic conductivity, but there is a risk of it generating hydrogen sulfide (poisonous) in contact with water.

Therefore, we proceeded with the development with the oxide-type solid electrolyte that makes use of the safer sintering technology that is an advantage of NAMICS.

figure：Solid electrolyte

Challenge

The sintering behavior of different materials must be aligned.

Results and Findings

  • We studied the materials for the solid electrolyte/active material and succeeded in developing an oxide-based solid-state secondary battery by adjusting their sintering behaviors.

A secondary battery having the charge/discharge characteristics as shown in the figure below and a good reliability test result was completed.​

The internal structure of the solid-state secondary battery

figure：white:Current collector + active material / Black:Oxide-based solid electrolyte

Charge and discharge characteristics of 3.2 X 2.5 mm 100-layer product

figure：Charge and discharge characteristics of 3.2 X 2.5 mm 100-layer product

Exhibition ICEP 2018
Presentation title Multilayer ceramic Li-ion secondary battery​​

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