報告書番号

T93079

タイトル（和文）

リチウム伝導性固体電解質の開発動向

タイトル（英文）

TRENDS IN RESEARCH ON LITHIUM CONDUCTIVE SOLID ELECTROLYTE

概要 （図表や脚注は「報告書全文」に掲載しております）

次世代型電池として期待されている全固体型リチウム二次電池用固体電解質について，その研究動向を調査した。電池の電解質として，現状の有機電解液を固体にすると，漏液がなくなり，沸点が高くなることから高温における安定性が高まる。また，計上自由度の高さから，エネルギー密度の向上が期待できる。しかし，現状では，大型化を目指した二次電池としては，リチウムイオンの伝導性が十分ではなく，イオン伝導度の改善が課題である。電解質には高分子系と無機系がある。高分子系は，比較的伝導度は高いが，アニオンの移動が考えられ，充放電時の抵抗の増大が懸念される。無機系は，現状の伝導度は低いが，リチウムカチオンのみの伝導である。一方，無機系の伝導メカニズムを高分子マトリクスに取り込んだ混合系は，双方の利点を持つ系として期待できる。

概要 （英文）

LITHIUM SECONDARY BATTERIES HAVE BEEN STUDIED FOR ELECTRIC POWER STORAGE AND ARE USED TO SUPPLY POWER FOR HOME ELECTRONICS. PRESENTLY ,ORGANIC SOLVENTS ARE USED AS ELECTROLYTES. SOME PROBLEMS REMAIN FOR PRACTICAL USE,ESPECIALLY RELIABILITY AND SAFETY. USE OF SOLID ELECTROLYTES IS EXPECTED TO BRING MANY BENEFITS. FOR EXAMPLE,THERE WILL BE NO LIQUID LEAKAGE. THE STABILITY AT HIGH TEMPERATURES WILL IMPROVE BECAUSE OF THE HIGH BOILING POINT OF SOLID ELECTROLYTES. FURTHERMORE,ENERGY DENSITIES OF CELLS ARE EXPECTED TO BE HIGHER BECAUSE OF SHAPE FLEXIBILITY (BIPOLAR CELLS WITH THIN SOLID FILM ELECTROLYTE). URGENT PROBLEMS FOR SOLID ELECTROLYTES INCLUDE INSUFFICIENT CONDUCTIVITY WHICH IS NOT HIGH ENOUGH FOR HIGH-POWER USE OF LITHIUM SECONDARY BATTERIES. PROGRESS IS NEEDED TO REALIZE THE ALL-SOLID-STATE LITHIUM SECONDARY BATTERY. THIS PAPER REPORTS TRENDS IN RESEARCH AND SHOWS PROMISING DIRECTIONS FOR THE FUTURE STUDY OF SOLID ELECTROLYTES FOR ALL-SOLID-STATE BATTERIES. AT PRESENT,THERE ARE TWO SOLID ELECTROLYTES: POLYMER TYPES,ANDINORGANIC TYPES. POLYMER ELECTROLYTES SHOW COMPARATIVELY-HIGH IONIC CONDUCTIVITY,AND THEY CAN BE FORMED INTO THIN,MECHANICALLY-STRONG FILMS. HOWEVER,THE TRANSFERENCE NUMBER IS 0.3-0.5 SUGGESTING THE POSSIBILITY OF ANIONS MOVING AND INCREASING RESISTANCE IN THE CHARGE/DISCHARGE CYCLE. INORGANIC ELECTROLYTES STILL SHOW POOR CONDUCTIVITY AND POOR MECHANICAL PROPERTIES,BUT THE TRANSFERENCE NUMBER IS 1 SO THE LITHIUM IONS CARRY ALL THE ELECTRONS AT CHARGE/DISCHARGE. COMPOSITE ELECTROLYTES USE THECONDUCTION MECHANISM OF INORGANIC ELECTROLYTES,IN A POLYMER MATRIX. THEY MAY HAVE THE ADVANTAGES OF BOTH ELECTROLYTES,SUCH AS HIGH LITHIUM CONDUCTIVITY,HIGH MECHANICAL STRENGTH,AND HIGH TRANSFERENCE NUMBER.

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