Research On Low Temperature Performance Of Lithium-Ion Battery

Both negative and positive electrodes in lithium-ion batteries have their own most compatible electrolyte. However, it is impossible for us to use two different kinds of electrolytes in the same battery system. Therefore, the selected electrolyte must have common compatibility with both positive and negative electrode materials.We selected material A from different cathode materials LiCoO2 as researched electrode material. In view of poor electrolyte conductivity at low temperature, we improve performance of normal electrolyte by multi-cosolvents. Of the compatibility of cathode/anode electrode materials with 4 kinds of electrolytes investigated, anode MCMB has the excellent common compatibility with the electrolyte of EC:DEC, which has the highest-melting EC constitute of the 4 kinds of electrolytes. Solutions containing a high percentage of EC conduce to favorable SEI film formation. While cathode LiC0O2 has the excellent common compatibility with the electrolyte of EC:DEC:DMC:X and EC:DEC:DMC:Y.With lowering of the temperature, capacity of MCMB-LiCoO2 cell decreases and electric polarization increases. One may find that the primary cause of the poor Li-ion cell performance at low temperature is related to Li-ion diffusion in the carbon anode and not in the electrolyte and/or SEI film, lithiation into delithiated graphite is more difficult than delithiation out of lithiated graphite at low temperatures, which results in decrease of capacity. The higher polarization voltage may be ascribed to the decrease in ionic conductivity of the electrolyte, the slowness of Li-ion diffusion in the MCMB anode and the new SEI due to deposition of metallic lithium during low-temperature charging.We found by the three-electrode experimental cell, deposition of metallic lithium during low-temperature charging is related to electrolyte, charging rate, cut-off voltage and so on.