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Two stage synthesis LiMPO4 (M = Fe, Co, Ni) and NaFePO4 via M2P2O7∙xH2O intermediary: TG-DSC-MS studyтезисы доклада
- Авторы: Svetlana MUDRETSOVA, Andrey STRELETSKI, Alyona KAN, Anastasiya TATARENTSEVA, Vladimir ALYOSHIN
- Сборник: The 11th European Symposium on Thermal Analysis and Calorimetry (ESTAC11), August 17-21, 2014, Espoo, Finland
- Тезисы
- Год издания: 2014
- Место издания: Finland
- Первая страница: 58
- Последняя страница: 58
- Аннотация: At present time the LiMPO4 (M = Fe, Co, Ni) cathode materials for lithium rechargeable batteries are in the greatest interest. The NaMPO4 are perspective for new types of sodium rechargeable batteries. The size and shape of the particles have a significant influence on the electric properties of material. Two-stage synthesis allows obtaining the particles of desired size by forming M2P2O7∙xH2O and MHPO4 intermediary using solution crystallization. These particles may be transformed into LiMPO4 or NaMPO4 without size and form changing by solid-state reaction with lithium or sodium carbonate. The starts MHPO4 were obtained by mixing MSO4 and NaH2PO4 solutions. Pyrophosphates M2P2O7 were precipitated from solution Na4P2O7 by adding MSO4 solution. The obtained substances were separated by centrifugation, then washed thoroughly with water, dried, mixed with lithium carbonate in stoichiometric amounts, and sintered in an argon flow. The chemical reactions between M2P2O7∙xH2O and lithium or sodium carbonate, and MHPO4 with lithium carbonate were studied by TG-DSC with simultaneous mass-spectroscopic analyzing (MS) of gaseous products of reaction, using NETZSCH STA 409 PC/PG and STA 449 C (alumina crucibles) technique with the mass-analyzer QMS 403 C Aëolos. Maxima in the derivative weight correlated with thermal maxima and maxima of gassing. The ions with m/e = 18 (H2O+) and 44 (CO2+) were taken into consideration for determination of vapor composition. The phase composition of start compounds and products of reaction were confirmed by X-ray analysis (Huber G670 diffractometer). To control size and shape of obtained particles the scanning electron microscopy (SEM) was involved. The chemical composition was controlled by ICP-MS. The MHPO4∙xH2O substances are thermally unstable and decomposed with pyrophosphate formation and water escaping under heating. According to the TG-DSC-MS study the basic chemical transformations in reaction between CoHPO4 and Li2CO3 are finished near 650°C, and for Co2P2O7 - near 700°C. The main weight loss associated with escaping of carbon dioxide and water in the first case, and carbon dioxide only in the second case. The stable M2P2O7∙xH2O is more preferable for LiMPO4 synthesis. The pyrophosphate technique is available for obtaining NaMPO4 synthesis in the same experimental conditions. Two-stage crystallization with pyrophosphates formation as intermediates allows obtain lithium and sodium phosphate of 3d-elements. The size and shape of the particles corresponds to the initial pyrophosphate. The reactions of lithium carbonate with cobalt hydrogenphosphates repeats mainly the results obtained previous to ammonia-cobalt phosphates; in case of interaction with intermediate cobalt pyrophosphates the higher temperature is required. The obtained results are discussed.
- Добавил в систему: Алёшин Владимир Алексеевич