Regulating the Li+ -Solvation Structure of Ester Electrolyte for High-Energy-Density Lithium Metal Batteries.

The development of high-energy-density Li metal batteries are hindered by electrolyte consumption and uneven lithium deposition due to the unstable lithium-electrolyte interface (SEI). In this work, tetraglyme is introduced into ester electrolyte to regulate the Li+ -solvation structures for stable SEI while remaining appropriate voltage window for high-voltage cathodes. In the modified solvation structures, an enhanced lowest unoccupied molecular orbital energy level occurs, resulting in relieved electrolyte degradation. In addition, the modified solvation structures can facilitate adequate LiNO3 dissolution in the ester electrolyte (denoted as E-LiNO3 ), contributing to constant supplement of constructing highly conductive LiNx Oy -containing SEI for dendrite-free Li deposition under high capacity condition. As a result, the Li||Cu cell-based on this electrolyte exhibits high Li plating/stripping Coulombic efficiency of 98.2% over 350 cycles. Furthermore, when paired with high-voltage LiNi0.5 Co0.2 Mn0.3 O2 cathodes, the E-LiNO3 enables a stable cycling with a high-energy-density of 296 Wh kg-1 based on the full cell under realistic testing conditions (lean electrolyte of 3 g Ah-1 , limited Li excess of 2.45-fold, and high areal capacity of 4 mAh cm-2 ).

Breaking Free from Cobalt Reliance in Lithium-Ion Batteries.

The exponential growth in demand for electric vehicles (EVs) necessitates increasing supplies of low-cost and high-performance lithium-ion batteries (LIBs). Naturally, the ramp-up in LIB production raises concerns over raw material availability, where constraints can generate severe price spikes and bring the momentum and optimism of the EV market to a halt. Particularly, the reliance of cobalt in the cathode is concerning owing to its high cost, scarcity, and centralized and volatile supply chain structure. However, compositions suitable for EV applications that demonstrate high energy density and lifetime are all reliant on cobalt to some degree. In this work, we assess the necessity and feasibility of developing and commercializing cobalt-free cathode materials for LIBs. Promising cobalt-free compositions and critical areas of research are highlighted, which provide new insight into the role and contribution of cobalt.