Voids almost certainly disrupt Li ion conduction, lowering the rate capability of the active material. Defects in single crystal cathode particles also serve as nucleation points for microcracks after long-term cycling. These defects and voids can to some extent be corrected by optimizing the crystal growth conditions inside the particles, and their subsequent annealing. Long, high temperature annealing (up to 900 • C) is energetically expensive, creating a need for lower-temperature, faster growth conditions. If the temperature during synthesis and annealing is too high, evaporation of the Li salts and loss of oxygen also occur, drastically decreasing the structural stability and performance of the active material. If the temperature is too low, then it becomes difficult to grow large, high-quality crystals. Therefore, tools which can quickly screen and evaluate the probable performance of the active material are valuable. Voids may even confer beneficial effects, by accommodating strain from anisotropic volumetric expansion, depending on the relative rate of different degradation phenomena. Degradation is a function of cycling parameters, and depends on specific device applications. For example, an active material optimized for long-term cycling stability may require a different microstructure than for fastcharging, or deep discharge. Ultimately, the influence of these voids on performance and durability can only be validated using extended cycling, although we anticipate that the role of predictive analytics in cathode development will continue to grow over time.