Changhong Wang

Ultrahigh-Capacity and Long-Life Lithium-Metal Batteries Enabled by Engineering Carbon Nanofiber-Stabilized Graphene Aerogel Film Host

A safe, high-capacity, and long-life Li metal anode is highly desired due to recent developments in high-energy-density Li-metal batteries. However, there are still rigorous challenges associated with the undesirable formation of Li dendrites, lack of suitable host materials, and unstable chemical interfaces. Herein, a carbon nanofiber-stabilized graphene aerogel film (G-CNF film), inspired by constructional engineering, is constructed. As the host material for Li deposition, the G-CNF film features a large surface area, porous structure, and a robust skeleton that can render low local current density. This allows for dendrite-free Li deposition and mitigation of problems associated with large volume change. Importantly, the G-CNF film can keep high Li plating/stripping efficiency at nearly 99% for over 700 h with an areal capacity of 10 mA h cm-2 (the specific capacity up to 2588 mA h g-1 based on the total mass of carbon host and Li metal). The symmetric cells can stably run for more than 1000 h with low voltage hysteresis. The full cell with the LiFePO4 cathode also delivers enhanced capacity and lowered overpotential. As two-in-one host materials for both cathodes and anodes in Li-O2 batteries, the battery exhibits a capacity of 1.2 mA h cm-2 .

A high-energy sulfur cathode in carbonate electrolyte by eliminating polysulfides via solid-phase lithium-sulfur transformation

Carbonate-based electrolytes demonstrate safe and stable electrochemical performance in lithium-sulfur batteries. However, only a few types of sulfur cathodes with low loadings can be employed and the underlying electrochemical mechanism of lithium-sulfur batteries with carbonate-based electrolytes is not well understood. Here, we employ inxa0operando X-ray absorption near edge spectroscopy to shed light on a solid-phase lithium-sulfur reaction mechanism in carbonate electrolyte systems in which sulfur directly transfers to Li2S without the formation of linear polysulfides. Based on this, we demonstrate the cyclability of conventional cyclo-S8 based sulfur cathodes in carbonate-based electrolyte across a wide temperature range, from −20u2009°C to 55u2009°C. Remarkably, the developed sulfur cathode architecture has high sulfur content (>65u2009wt%) with an areal loading of 4.0u2009mgu2009cm−2. This research demonstrates promising performance of lithium-sulfur pouch cells in a carbonate-based electrolyte, indicating potential application in the future.Carbonate-based electrolytes can impart advantages in lithium sulfur batteries, but performance is often limited by incompatibility with sulfur-based cathodes. Here the authors elucidate a mechanism for conversion of sulfur to lithium sulfide and demonstrate improved performance in a Li-S cell.

Multi-functional nanowall arrays with unrestricted Li+ transport channels and integrated conductive network for high-areal-capacity Li-S batteries

The rational design of cathode hosts with superior polysulfide (PS) confinement properties, excellent Li+/e− transport and improved cyclability is of the utmost importance for high-areal-capacity lithium–sulfur (Li–S) batteries. Herein, multi-functional nanowall arrays (MNWAs) combining the aforementioned properties are fabricated to improve the electrochemical performance of Li–S batteries with high areal sulfur loadings. The integrated conductive networks and top-down vertically aligned Li+ transport channels are beneficial to Li+/e− transport, resulting in high rate performance with a discharge capacity of 620 mA h g−1 at a high current density of 9.6 mA cm−2 for 4 mg cm−2 sulfur-loaded S/MNWA electrodes. Additionally, the strong PS shuttling suppression via the synergetic effects of physical confinement and chemical adsorption leads to Li–S batteries with a sulfur loading of 10 mg cm−2 capable of delivering a high areal capacity of 12.4 mA h cm−2 with a high capacity retention of nearly 85% for over 100 cycles. Whats more, the Li–S batteries assembled with 4 mg cm−2 sulfur-loaded S/MNWA electrodes show an ultra-low capacity decay of 0.07% per cycle over 400 cycles at 3.2 mA cm−2.

High-performance all-solid-state Li–Se batteries induced by sulfide electrolytes

All-solid-state Li–S batteries have attracted significant attention due to their high energy density and high safety. However, the insulating nature of S has limited the electrochemical performance of all-solid-state systems. Alternatively, Se, possessing orders of magnitude higher electronic conductivities, may be a promising cathode candidate but has been completely overlooked in all-solid-state battery systems. Herein, a feasible all-solid-state Li–Se battery is demonstrated using Se–Li3PS4–C as the cathode, Li3PS4 as the electrolyte, and an Li–Sn alloy as the anode. In addition to the high electronic conductivity (1 × 10−3 S cm−1) of Se, a high Li+ conductivity of 1.4 × 10−5 S cm−1 across the Se–Li3PS4 interface can be achieved. The all-solid-state Li–Se cell shows a high reversible capacity of 652 mA h g−1 (96% of theoretical capacity) and exhibits favorable capacity retention upon cycling. This work demonstrates the advantages of a Se cathode in all-solid-state batteries and provides new opportunities for improving the charge transfer of S cathodes in solid-state batteries.

In Situ Li3PS4 Solid-State Electrolyte Protection Layers for Superior Long-Life and High-Rate Lithium-Metal Anodes

A thin and adjustable Li3 PS4 (LPS) solid-state electrolyte protection layer on the surface of Li is proposed to address the dynamic plating/stripping process of Li metal. The LPS interlayer is formed by an in situ and self-limiting reaction between P4 S16 and Li in N-methyl-2-pyrrolidone. By increasing the concentration of P4 S16 , the thickness of the LPS layer can be adjusted up to 60 nm. Due to the high ionic conductivity and low electrochemical activity of Li3 PS4 , the intimate protection layer of LPS can not only prevent the formation of Li dendrites, but also reduces parasitic side reactions and improves the electrochemical performance. As a result, symmetric cells with the LPS protection layer can deliver stable Li plating/stripping for 2000 h. Full cells assembled with the LPS-protected Li exhibit two times higher capacity retention in Li-S batteries (≈800 mAh g-1 ) at 5 A g-1 for over 400 cycles compared to their bare Li counterparts. Furthermore, high rate performances can be achieved with Li-LPS/LiCoO2 cells, which are capable of cycling at rates as high as 20 C. This innovative and scalable approach to stabilizing the Li anode can serve as a basis for the development of next-generation high-performance lithium-metal batteries.