Compared with the external parameters

the internal parameters of lithium-ion batteries can better reflect the true state of lithium-ion batteries. However

the existing research on the estimation method of the state of charge (SOC) for lithium-ion batteries is basically based on external parameters. During the charging-discharging process of lithium-ion batteries

the negative electrode resistance changes regularly with the variation in lithium insertion amount. Based on this factor

a sensing method to monitor the negative resistance in real time is developed in this paper

moreover

a new method for the SOC estimation based on this method and a data-driven approach is proposed. Real-time monitoring of negative electrode resistance is achieved by introducing sensing lug in the negative electrode of the battery

and the position and width of the sensing lug are optimized by current density distribution simulation and long-cycle battery experimentation to reduce the influence of the sensing lug on battery performance. A strong correlation between the negative electrode resistance and SOC is verified through experimental data analysis. Additionally

combined with the gated recurrent unit (GRU) model

it is demonstrated that after introducing negative electrode resistance as an input feature

the root mean square error (RMSE) of the test set result is reduced by 1. 08% compared with that before the introduction. The results show that the SOC estimation method based on negative electrode resistance has promising application prospects and research significance.