실리카 템플레이트를 이용하여 다공성 중공형태를 갖는 LiMn_(2)O_(4) 합성 및 전기화학적 특성 연구
Synthesis and Electrochemical Performance of Mesoporous Hollow Sphere Shape LiMn_(2)O_(4) using Silica Template
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다공성 중공형태의 LiMn_(2)O_(4)는 실리카 템플레이트과 침전법에 의해 합성되었다. 합성한LiMn2O4는 나노사이즈의 1차입자를 가지며 다공성 중공형태를 가지고 있었다. 실리카 템플레이트의 제거는 NaOH를 이용하여 화학적 에칭법이 사용되었다. NaOH의 농도를 높여줌에 따라망간산화물 입자 크기가 증가 하며 다공성의 중공구가 형성되었다. X-선 회절 분석을 통하여 합성된 LiMn_(2)O_(4)는 Fd3m의 공간 그룹을 가지는 스피넬 구조가 형성된 것을 확인 할 수 있었다. 실리카와 망간염의 비율을 높여주었을 경우 합성된 LiMn_(2)O_(4)는 1차입자의 크기는 감소한다. 실리카와 망간염의 비율이 1 : 9 이상인 경우에서 마이크론 단위의 정방정계의 LiMn_(2)O_(4)가 합성되었다. 다공성 중공형태의 LiMn_(2)O_(4)의 전기화학적 특성을 평가하기 위하여 2032형태의 코인셀을 제작하여 충/방전 테스트를 하였다. 나노사이즈의 1차입자를 가진 시료의 경우에는 마이크론 사이즈의1차입자를 가진 시료보다 용량은 낮았지만 용량유지율은 향상되는 것 확인 할 수 있었다.
Abstract
LiMn_(2)O_(4)with mesoporous hollow sphere shape was synthesized by precipitation method with silica template. The synthesized LiMn_(2)O_(4)has nanosized first particle and mesoporous hollow sphere shape. Silica template was removed by chemical etching method using NaOH solution. When the concentration of NaOH solution was increased, first particle size of manganese oxide was decrease and confirmed mesoporous hollow shpere shape. X-ray diffraction(XRD)patterns revealed that the synthesized samples has spinel structure with Fd3m space group. In case the ratio of silica and maganese salt increased, the size of first particles was decreased. The tetragoanal LiMn_(2)O_(4)with micron size was synthesized at ratio of silica and manganese salt over 1 : 9. The prepared samples were assembled as cathode materials of Li-ion battery with 2032 type coin cell and their electrochemical properties are examined by charge-discharge and cyclic performance. Electrochemical measurements show that the nano-size particles had lower capacity than micron-size particles. But, cyclic performance of nano-size particles had better than that of micron-size particles.
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