Increasing the durability of Li-ion batteries by means of manganese ion trapping materials with nitrogen functionalities

Manganese dissolution from positive electrodes seriously reduces the useful life of Li-ion batteries, especially with positive electrode materials having spinel phases. We show herein that Mn ion trapping separators containing inexpensive mass-produced materials may dramatically increase the life of Li-ion batteries. LiMn₂O₄-graphite cells containing these materials and a LiPF₆ based electrolyte solution display excellent capacity retention during cycling at both room and elevated temperatures, over baseline cells with plain separators. After 30 days of cycling at 55 °C and C/5 rate, LiMn₂O₄-graphite cells containing three different Mn-trapping materials with nitrogen functionalities retain between 75% and 125% more of the initial capacity than the baseline cells. Mn amounts in graphite negative electrodes from cells with the functional separators are 13–21 times lower than in baseline cells. LiMn₂O₄ lattice shrinkage in cells with functionalized separators is negligible compared to baseline cells, indicating major reductions in the loss of electrochemically active Li⁺ ions and increased stability of the LiMn₂O₄ crystal lattice.