~140 nm-diameter commercially available silicon nanoparticles with a 60 wt% loading in a slurry with Super P and LiPAA as conductive additive and binder, respectively, were used to prepare composite silicon nanoparticle electrodes with an average mass loading of 0.5-0.6 mg/cm 2 . We first examine cycling using a deep lithiation cut-off of 5 mV, terminating when the specific current reaches 20 mA/g. The CCCV protocol, terminating when a certain minimum specific current is reached, is usually implemented for safe practical charging of Li-ion batteries, and corresponds to lithiation of the anode active material. Therefore, any (detrimental) effects of the CV step on the capacity retention of silicon nanoparticle electrodes are highly technologically relevant. We observe a sharp peak at 0.42 V vs. Li in the dQ/dV plot for delithiation (Figure persists until the 50th cycle (Figure ). However, without a CV step, the dQ/dV indicates delithiation from Li15Si4 during the initial three cycles at 200 mA/g, but delithiation from amorphous lithium silicide as soon as the current is increased to 600 mA/g (Figure ). Despite the difference with respect to c-Li15Si4 formation, the effect on absolute capacity and capacity retention is comparatively minor. The silicon anodes suffer capacity loss at roughly the same rates whether a CV step is included or not (Figure ). The maximum capacity is higher when a constant voltage step is used for silicon nanoparticles, reaching 3474 mAh/g and 3354 mAh/g for the CCCV and CC cells, respectively (Figure ). However, after more than ~20 cycles, both cells approach the same capacity and continue to decay at the same rates. 50 mV is often considered the line above which c-Li15Si4 will not be formed in thin films, although there are contrary examples with nanoparticles that show a dependence on size and charging rate. Specifically, an increase of particle size above ~70 nm and a decrease of charging rates are associated with more formation of the c-Li15Si4 phase. Accordingly, dQ/dV reveals the presence of c-Li15Si4 at 50 mV in the silicon nanoparticle electrodes studied here when a constant voltage step is used (Figure ). Without a constant voltage step, there is a small c-Li15Si4 peak at 0.42 V during the first cycle, and none in subsequent cycles. Including a CV step at 50 mV does come with an increase in capacity, especially in early cycles, going from a maximum capacity of 2809 mAh/g for CC to 3322 mAh/g for the CCCV protocol. Comparisons of capacity retention with and without a constant voltage step are complicated by a fairly large gain in capacity during the first ten cycles (Figure ). Such a rise indicates incomplete lithiation in the early steps, the cause of which is not clear, but may be related to an improvement of electrolyte access resulting from the expansion and contraction of the Si. Nonetheless, after ~25 cycles, both cells converge towards the same absolute capacity, and relative capacity loss is similar for both. The c-Li15Si4 phase still continues to form in the CCCV cell after 25 cycles, but does disappear more quickly with a 50 mV cut-off than with a 5 mV cut-off. To help visualize the quantity of c-Li15Si4 that is formed in each cycle, as well as the differences between 5 mV and 50 mV cut-off, we plot the delithiation capacity before 0.35 V as a percentage of the total delithiation capacity (Figure ). We chose this potential because it is past the peak potential of the first broad delithiation dQ/dV peak of the amorphous phase, and prior to the sharp peak characteristic of c-Li15Si4. When the first phase transition falls between c-Li15Si4 and a-Li2Si at 0.42 V, there should be almost no capacity seen prior to 0.35 V. However, when the fully lithiated material remains amorphous, the fraction of the total capacity prior to 0.35 V approaches 40%, as can be seen from Figure . Plotting delithiation in this manner helps to clarify the following results. First, we can observe the sharp contrast between cycling the 5 mV CC cells at 200 mA/g (cycles 1-3) and at 600 mA/g (cycles 4-80) (Figure ), in which c-Li15Si4 is present and stable at the lower current, but disappears immediately when higher currents are applied. Using relative delithiation capacity <0.35 V, we can also clearly see that c-Li15Si4 stops forming much earlier. With a cut-off of 5 mV and a CV step, the electrodes begin to derive more capacity from a-LixSi after ~40 cycles, with c-Li15Si4 playing a minimal role after ~60 cycles, see Figure . However, when the cut-off voltage is increased to 50 mV, the transition away from the c-Li15Si4 phase starts and ends at ~20 and ~40 cycles, respectively (Figure ). were performed at 200 mA/g, and all subsequent cycles at 600 mA/g. All cells were delithiated to 1.5 V using CC protocol.