Both Interface and Bulk Stable LiNi_0.5Mn_1.5O₄Cathodes for High-Energy Li-Ion Batteries

Delivery of a high operating voltage with stable cycling behavior is a challenge in developing cathodes for high-energy Li-ion batteries (LIBs). The representative spinel LiNi0.5Mn1.5O4 materials own a high discharge voltage of 4.7 V (versus Li+/Li) and a large theoretical specific capacity of 147 mA h g-1. However, they usually suffer from undesired transition metal dissolution and intensive cathode-electrolyte interfacial side reactions during high-voltage cycling, incurring unacceptable capacity decay and short cycle life. To solve these problems, we present a radially aligned hierarchical structure with different chemical compositions from the bulk (LiNi0.4Cr0.1Mn1.5O4) to the surface (LiNi0.5Mn1.5O4) of the structure. The introduction of Cr3+ to the inner end suppresses the Jahn-Teller active Mn3+ and partial Mn2+ dissolution, thus improving the bulk stability. The construction of the undoped shell avoids and eliminates the catalytic effect of the dopant on interfacial side reactions, thus enhancing the interfacial stability. As a consequence, the designed LNMO@iCr-LNMO (6 wt % coating) compound achieves capacity retentions of 95.2% at 1C after 500 cycles and 93.6% at 2C after 1000 cycles. This work highlights the significance of bulk and interface chemistry in high-energy cathode materials for LIBs.