Principal Research Results

Research and Development of All-Solid-State Lithium-ion Battery−Low Cost Battery Preparation Approach using Carbon Anode Materials−
Background
Lithium-ion batteries used in mobile electronics contain flammable organic solvent in their electrolytes so that further safety
management is required for the development of kWh scale stationary-type storage system. Although an all-solid-state lithium-ion
battery using non-volatile solid polymer electrolyte (SPE) will be expected for improvement of safety and reduction of cost, thecombination with carbon-based anode material, which is already used in the conventional liquid electrolyte, was believed to be difficult in the suitable combination. Therefore, there was no report about the combination of SPE with such carbon-based electrode until
now.

Objectives
The study aims to determine application of the carbon-based (graphite) anode with low-cost production process and largearea preparation process for the development of all-solid-state lithium-ion battery.

Principal Results
All-solid-state lithium-ion battery, consisting of [LiFePO4 | SPE | Graphite], could be prepared by the overcoating of SPE on
the conventional graphite electrode sheet. The detailed clarified results are listed below.
1. The preparation procedure of all-solid-state lithium-ion battery [Low-cost production]
The battery preparation process using the overcoating method (Fig. 1) required no liquid filling process and needed no highcost separator. Furthermore, the process has the potential to produce the battery by one-line process, so it will be expected to reduce
the preparation process.
2. Large area and stacking battery preparation in one exterior package [Large battery production]
A flat-type (active surface area: 104cm2) battery could be prepared using aluminum-laminated package by the vacuum treatment of the battery inside. The prepared battery could operate with the suitable reversible capacity which was estimated from its
surface area (Fig. 2). Furthermore, the demonstrated series-connected battery in one exterior package suggested the possibility ofcompact and large battery development (Fig. 3).
3. Charge discharge cycle performance [Cycle life]
The prepared all-solid-state lithium-ion battery exhibited suitable initial properties (Fig. 4). Furthermore, the optimized
graphite electrode showed excellent cycle performance of 75% capacity retention at the 250th cycle, which suggested a quite goodprospect for the development of long-life all-solid-state lithium-ion batteries.

Further Developments
Further optimization of battery design and process will be developed.
Main Researcher: Yo Kobayashi,
Research Scientist, Sector, Batteries and Electrochemical Materials, Materials Science Research Laboratory
Reference
Yo Kobayashi et al., 2008, “Research and development of all solid state lithium ion battery”, CRIEPI Report, Q07018 (in Japanese)603. Energy Services for Customer

Fig.4

Charge / discharge voltage profiles of[LiFePO4|SPE|Graphite] all-solid-statelithium-ion cell.

Fig.1 Proposed battery preparation processusing overcoating method.

3Fig.2 A schematic of a flat cell using vacuumgas buffer.

Fig.5 Cycle performance of [Graphite|SPE|Li]
cell. 75% capacity was obtained at the250th cycle.

Fig.3 Operated 4-stack cell（13.69 V,13×8cm
flat-type. No additional pressure fromoutside）

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