Electrochemical Performance Of Electrolytes For LiMn₂O₄ Electrode

Li Mn2O4 is one of the most promising candidates for lithium ion battery cathode materials. However, in the charging and discharging progress, the dissolution of Mn3+ in the traditional LiPF6-based electrolyte leads to the capacity decay quickly especially under the high temperature. In order to search appropriate electrolytes for improving the performance of Li Mn2O4/Li cells, three works have been down.（1） Effect of sulfolane and lithium bis（oxalato）borate-based electrolytes on the performance of spinel LiMn₂O₄ cathodes at 55 °C. To seek a promising candidate electrolyte at elevated temperature for LiMn₂O₄（lithium manganese oxide）/Li cells, the electrochemical performance of 0.7 mol L-1 LiBOB（lithium bis（oxalate）borate）-SL（sulfolane）/DEC（diethyl carbonate）（1:1, in volume） electrolyte was studied at 55 °C. The results demonstrate that the LiBOB-SL/DEC electrolyte can slow down the dissolution and erosion of Mn ions and decrease the interface impedance. Moreover, the LiBOB-SL/DEC electrolyte could obviously improve the capacity retention, the operating voltage（4.05 V）, and the rate performance of Li Mn2O4/Li cells.（2） Effect of LiPF6-based electrolyte with a novel additive on the performance of Li Mn2O4 for lithium-ion batteries. Lithium difluoro（sulfato）borate（LiBF2SO4）!is investigated as an additive for LiMn₂O₄ cathode in lithium-ion batteries. Having compared the LiPF6-based electrolyte containing LiBF2SO4 additive with conventional LiPF6-based electrolyte, the electrolyte with LiBF2SO4 additive exhibits better ability to suppress Mn ion dissolution and wider electrochemical window. And having used in LiMn₂O₄/Li cells, it shows several advantages, such as small impedance, stable cycle performance, and good rate performance.（3） A new method for synthesis of lithium tetrafluoroborate for lithium-ion battery electrolytes. A new and easy method was introduced for synthesizing lithium tetrafluoroborate（LiBF4）. The reaction proceeded between（C2H5）2O·BF3 and an as-prepared Li2SO3 in（C2H5）2O solvent. And the Li2SO3 was synthesized by the reaction between Li2CO3 and H2SO3. The sample was measured by qualitative and quantitative analysis and the results showed that the product was pure LiBF4 and the obtained LiBF4 well meeted the requirement of rechargeable lithium-ion batteries（LIBs）. And having used in LiMn₂O₄/Li cells, it shows several advantages, such as small impedance, stable cycle performance, and high operating voltage.