Long-Life and Highly Utilized Zinc Anode for Aqueous Batteries Enabled by Electrolyte Additives with Synergistic Effects.

After decades of development, zinc-based batteries with the advantages of high energy density, low cost, and environmental benignity have been considered as a promising battery system in the application of energy storage. However, the poor cycle performance of zinc anode strongly restricts the cycle life of zinc-based batteries and thus limits its large-scale application. Electrolyte additives have been proven to be one of the most straightforward strategies in improving the stability of zinc anode during cycles, while the options of additives are still limited. This work is based on the in-depth investigation of the electrochemical behavior of both the organic additives and the zinc species in the electrolyte. The modification effects of poly(vinyl alcohol) (PVA) and vanillin as two typical additives from the electroplating industry in both the zinc plating and zinc anode are systematically studied. It is revealed that PVA could increase the utilization and rate performance of the anode, while greatly promoting the corrosion and shape change of the zinc anode. On the contrary, the existence of vanillin could maintain the structure of the anode during cycles, while the rate performance of the battery is hindered. With the coaddition of the PVA and vanillin, the zinc anode shows superior performance in cycle life, rate performance, active material utilization, and discharge energy retention. These findings provide insight for the enrichment of electrolyte additives in zinc-based batteries.

High-Efficacy and Polymeric Solid-Electrolyte Interphase for Closely Packed Li Electrodeposition.

The industrial application of lithium metal anode requires less side reaction between active lithium and electrolyte, which demands the sustainability of the electrolyte-induced solid-electrolyte interface. Here, through a new diluted lithium difluoro(oxalato)borate-based (LiDFOB) high concentration electrolyte system, it is found that the oxidation behavior of aggregated LiDFOB salt has a great impact on solid-electrolyte interphase (SEI) formation and Li reversibility. Under the operation window of Cu/LiNi0.8Co0.1Mn0.1O2 full cells (rather than Li/Cu configuration), a polyether/coordinated borate containing solid-electrolyte interphase with inner Li2O crystalline can be observed with the increasing concentration of salt, which can be ascribed to the reaction between aggregated electron-deficient borate species and electron-rich alkoxide SEI components. The high Li reversibility (99.34%) and near-theoretical lithium deposition enable the stable cycling of LiNi0.8Co0.1Mn0.1O2/Li cells (N/P < 2, 350 Wh kg-1) under high cutoff voltage condition of 4.6 V and lean electrolyte condition (E/C ≈ 3.2 g Ah-1).

Advanced liquid electrolytes enable practical applications of high-voltage lithium-metal full batteries.

High-voltage lithium metal batteries (HVLMBs) have received widespread attention as next generation high-energy-density batteries to meet the urgent demands of modern life. However, the unstable interphase between electrolytes and highly reactive electrodes is still an important threshold for practical applications. In this feature article, we review the formation mechanism of the electrode-electrolyte interphase in terms of cathodes and the Li metal anode, respectively, and summarize the surface modification methods to stabilize the interphase of HVLMBs. Electrolyte regulation strategies especially those using electrolyte additives are introduced, and the relationship between liquid electrolyte formulation, interphase engineering and the electrochemical performance of HVLMBs is analyzed. Finally, an industry-level evaluation is carried out and the remaining challenges are discussed for advanced electrolytes to guarantee the practical applications and commercialization of HVLMBs.

Explicit Gain Equations for Hybrid Graphene-Quantum-Dot Photodetectors.

Graphene is an attractive material for broadband photodetection but suffers from weak light absorption. Coating graphene with quantum dots can significantly enhance light absorption and create extraordinarily high photogain. This high gain is often explained by the classical gain theory which is unfortunately an implicit function and may even be questionable. In this work, explicit gain equations for hybrid graphene-quantum-dot photodetectors are derived. Because of the work function mismatch, lead sulfide quantum dots coated on graphene will form a surface depletion region near the interface of quantum dots and graphene. Light illumination narrows down the surface depletion region, creating a photovoltage that gates the graphene. As a result, high photogain in graphene is observed. The explicit gain equations are derived from the theoretical gate transfer characteristics of graphene and the correlation of the photovoltage with the light illumination intensity. The derived explicit gain equations fit well with the experimental data, from which physical parameters are extracted.