Beyond safety and high power, there is an ever-increasing need for long cycle life of LIBs. Low-reactivity SEB cells built with highly stable materials offer longer calendar life (fig. S2), evident from the slow capacity fade when the battery is in idle conditions at room temperature. At elevated temperatures, cycling of SEB cells is also stable. Figure 4A compares capacity retention of the baseline cell with SEB cells during cycling at 60°C of 1C CC charge to 4.2 V CV charge till C/20 and then 1C discharge to 2.8 V. Clearly, the SEB cells outperform the baseline cell as evidenced by a 20% capacity loss at 481 cycles with visible signs of cell deformation due to gas evolution and graphite anode swelling for the baseline cell, while SEB-3 can achieve 2821 cycles before reaching 20% capacity loss. This corresponds to ca. 6× improvement in cycle life. In addition, SEB-3 achieves 4014 cycles at 75% capacity retention while still showing signs of a healthy cell capable of cycling stably (no perceptible gassing or lithium plating). The average discharge capacity of these 4014 cycles is 84.2% of an equivalent full cycle (EFC). Assuming a 153-mile driving range per EFC for an electric vehicle (e.g., 2019 BMW i3), the 4014 cycles mean >517,000 miles of lifetime. That is more than 5× the warranty for commercial electric cars (e.g., BMW i3, 70% capacity for 8 years or 100,000 miles). Improvement of cell lifetime can be further demonstrated by considering the rate of capacity fade during calendar aging at room temperature (i.e., the stable state), which is 7× lower than that at 60°C (the reactive state). The SEB cell will only be heated to the reactive state for situations requiring high power or fast charging. The greater part of its lifetime (>90%) would be spent in idle conditions (the stable state). Therefore, in the field, the SEB cycle life is expected to extend much beyond 4014 cycles before reaching 25% capacity loss.