Improved the Structure and Cycling Stability of Ni-rich Layered Cathodes by Dual Modification of Yttrium Doping and Surface Coating.

A crucial challenge for the commercialization of Ni-rich layered cathodes (LiNi0.88Co0.09Al0.03O2) is capacity decay during cyclic process, which originates from its interfacial instability and structural degradation. Herein, a one-step dual-modified strategy is put forward to in-situ synthesize the yttrium (Y) doped and yttrium orthophosphate (YPO4) modified LiNi0.88Co0.09Al0.03O2 cathode material. It is confirmed that the YPO4 coating layer as good ion conductor can stabilize solid-electrolyte interface, while the formative strong Y-O bond can bridle TM-O slabs to intensify lattice structure in the state of deep delithium (>4.3 V). In particular, both combined advantages effectively withstand the anisotropic strain generated upon the H2-H3 phase transition and further alleviate the crack generation in unit cell dimensions, assuring high capacity delivery and fast Li+ diffusion kinetic. This dual-modified cathode shows advanced cycling stability (94.1% at 1 C after 100 cycles in 2.7-4.3 V), even at high cut-off voltage and high rate, and advanced rate capability (159.7 mAh g-1 at 10 C). Therefore, it provides a novel solution to achieve both high capacity and high stable cyclability for Ni-rich cathode materials.