Improvement of electrochemical homogeneity for lithium-ion batteries enabled by a conjoined-electrode structure

[Display omitted] •A conjoined-electrode structure capable of mitigating electrochemical heterogeneity of lithium-ion batteries is proposed.•Rate capability is improved by 26% at a rate of 3C, and capacity fade rate is reduced by 50% under 1C cycling.•A Self-balancing mechanism explaining the effects of the conjoined-electrode structure is revealed by simulation analysis.•Principles of designing structural parameters are established to maximizing the self-balancing effect.•Great commercialization potential is demonstrated in terms of energy density, thermal effect, and mechanical strength. Electrochemical inhomogeneity of lithium-ion batteries stemming from heterogeneous electrode microstructure adversely affects battery rate-performance, lifetime and safety. It is attributed to manufacturing errors of electrodes in previous studies. However, the significant heterogeneous electrochemistry is still found in commercial battery electrodes with high manufacturing accuracy. Here, we propose a conjoined-electrode structure to improve the electrochemical homogeneity, in which every two adjacent cathodes or anodes are connected through microholes on current collectors. The commercial level pouch lithium-ion battery with the conjoined-electrode structure is fabricated and it displays a better rate capability (26% higher capacity at 3C rate) and a lower capacity degradation rate (decreased by 50% in the cycling tests at 1C rate). A 3-D electrochemical-thermal model is used in simulation with inhomogeneous situations to reveal the self-balancing effects of state of charge, current density, and Li-ion concentration in the conjoined-electrode structure, which facilitate more homogeneous electrochemistry in lithium-ion batteries. The limitation factor of the self-balancing effects varies depending on the structural parameters, which limits the conjoined-electrode structure design.