Solution-Based Deep Prelithiation for Lithium-Ion Capacitors with High Energy Density.

Lithium-ion capacitors (LICs) exhibit superior power density and cyclability compared to lithium-ion batteries. However, the low initial Coulombic efficiency (ICE) of amorphous carbon anodes (e.g., hard carbon (HC) and soft carbon (SC)) limits the energy density of LICs by underutilizing cathode capacity. Here, a solution-based deep prelithiation strategy for carbon anodes is applied using a contact-ion pair dominant solution, offering high energy density based on a systematic electrode balancing based on the cathode capacity increased beyond the original theoretical limit. Increasing the anode ICE to 150% over 100%, the activated carbon (AC) capacity is doubled by activating Li+ cation storage, which unleashes rocking-chair LIC operation alongside the dual-ion-storage mechanism. The increased AC capacity results in an energy density of 106.6 Wh kg-1 AC+SC, equivalent to 281% of that of LICs without prelithiation. Moreover, this process lowers the cathode-anode mass ratio, reducing the cell thickness by 67% without compromising the cell capacity. This solution-based deep chemical prelithiation promises high-energy LICs based on transition metal-free, earth-abundant active materials to meet the practical demands of power-intensive applications.

Reversible Magnesium Metal Cycling in Additive-Free Simple Salt Electrolytes Enabled by Spontaneous Chemical Activation.

Rechargeable magnesium (Mg) batteries can offer higher volumetric energy densities and be safer than their conventional counterparts, lithium-ion batteries. However, their practical implementation is impeded due to the passivation of the Mg metal anode or the severe corrosion of the cell parts in conventional electrolyte systems. Here, we present a chemical activation strategy to facilitate the Mg deposition/stripping process in additive-free simple salt electrolytes. By exploiting the simple immersion-triggered spontaneous chemical reaction between reactive organic halides and Mg metal, the activated Mg anode exhibited an overpotential below 0.2 V and a Coulombic efficiency as high as 99.5% in a Mg(TFSI)2 electrolyte. Comprehensive analyses reveal simultaneous evolution of morphology and interphasial chemistry during the activation process, through which stable Mg cycling over 990 cycles was attained. Our activation strategy enabled the efficient cycling of Mg full-cell candidates using commercially available electrolytes, thereby offering possibilities of building practical Mg batteries.