The development of rechargeable batteries beyond 300 Wh kg−1 for electric vehicles remains challenging, where low-capacity electrode materials (especially a graphite anode, 372 Ah kg−1) remain the major bottleneck. Although many high-capacity alternatives (e.g., Si-based alloys, metal oxides, or Li-based anode) are being widely explored, the achieved energy density has not exceeded 300 Wh kg−1. Herein, we present a new empirical model that considers multiple design parameters, besides electrode capacities, including areal loading density, voltage difference, initial capacity balance between the anode and cathode, and initial Coulombic efficiency, to estimate the achievable energy density. This approach is used to predict battery design that can achieve an energy density of >300 Wh kg−1. The model reveals that the lithium storage capacity of electrode materials is only one of several important factors affecting the ultimate battery energy density. Our model provides a new way to review the current battery systems beyond the prism of the electrode capacity and also presents a straightforward guideline for designing batteries with higher energy densities.