Effect of Lithium Silicate Addition on the Microstructure and Crack Formation of LiNiCoMnO Cathode Particles.

The microstructure of LiNiCoMnO cathode materials was controlled by the addition of lithium silicate, and the influence on the cycle performance and the rate capability was investigated. Si was not included within the lattice, but localized at the grain boundaries of the primary particles and the pores inside the secondary particles. The addition of the lithium silicate greatly decreased the density of the pores between the primary particles and improved the density of the secondary particles. The capacity retention was successfully improved for lithium silicate-added LiNiCoMnO. When lithium silicate-free LiNiCoMnO was charged to 4.3 V, many cracks were formed along the grain boundaries even in the first cycle, while crack formation was remarkably inhibited for lithium silicate-added LiNiCoMnO. Moreover, lithium silicate-added LiNiCoMnO particles were almost free from visible microcracks even after 100 cycles at the discharged state. These results suggest that the lithium silicate reinforces the grain-adhesion at the grain boundaries, inhibiting crack formation and electrolyte decomposition inside the cracks.