The influence of water in electrodes on the solid electrolyte interphase film of micro lithium-ion batteries for the wireless headphone.

During the production of micro lithium-ion batteries (LIBs), which are widely used in wireless headphones and other small portable devices, numerous factors can affect their quality, among which the content of water plays a crucial role. In this work, the influence of water in electrodes on the performances of micro LIBs is studied deeply. When the content of water increases, both the rate performance and the cycling performance of the batteries fade. The discharge capacity retention of the battery from high water content sample group H (group H) is 81.81% after 350 cycles at 2C, while that of the battery from low water content sample group L (group L) is 89.89% under the same condition. As for the rate performance, the discharge capacity of group H is only 58.66% of group L at 5C. To take a step further, it is mainly because an overgrowth of the solid electrolyte interphase film happen with the growth of water content. Accordingly, excess lithium ions are consumed and the porous structure of the anode is destroyed. Considering the results above, we believe that this work can offer a theory foundation to carry out the failure analysis of micro batteries.