Grain boundaries boost the prelithiation capability of the Li2CO3 cathode additives for high-energy-density lithium-ion batteries

•The N-Li2CO3 cathode prelithiation additive enriched with GBs was synthesized.•The Σ(001) GBs in the N-Li2CO3 exhibit enhanced Li-ion and electronic conductivity.•The ∼100 % capacity utilization of the N-Li2CO3 (724 mAh/g) is obtained.•The improved energy density and lifetime of the Si-based full cells are achieved.