hinder the practical deployment of Li metal batteries. Thus far, various emerging strategies, including electrolyte optimization, [2] solid electrolyte application, [3] and artificial protective layer construction, [4] have been proposed to stabilize SEI. These strategies have achieved remarkable electrochemical performances and provided perspectives for developing long lifespan Li metal batteries. Regrettably, most of them were conducted in a coin cell setting. The resulted from different test conditions make it exceedingly difficult to compare the developed materials or concepts for practical application. [5] In real high-energy Li metal batteries, any minor defects (such as Li dendrites, interface parasitic reactions, and volume expansion) will be aggravated, leading to unstable cycle performance. In particular, when the coin cell is magnified to the pouch cell, it will be accompanied by some unpredictable problems. [6] For example, cell gassing, which is absolutely neglected in typical coin cells but turns into a new, inextricable problem in high-energy Li metal batteries. Gassing is a common phenomenon in other battery systems (such as lead-acid batteries, zinc-air batteries, and lithium titanate-based batteries) and has been studied in depth. [7] However, the gassing of Li metal batteries is often overlooked and has not attracted enough attention. It can be predicted that the gassing problem will be an inevitable topic in the future development of Li metal batteries. Generally, highly active Li metal reacts spontaneously with organic electrolyte to form an SEI layer. [8] Unfortunately, this passivated SEI film (commonly inhomogeneous, low modulus, and poor stability) hardly regulates uniform nucleation and growth of Li and suppresses interfacial parasitic reactions between Li metal and electrolyte, causing severe Li dendrites and gassing behavior, which have a considerable impact on the cycle life of high-energy Li metal batteries (Figure 1a). Hence, constructing a stable and cell-level SEI film to extend the cycle life in practical high-energy Li metal batteries is urgently needed.Here, we constructed an efficient multifunctional silanization interface (MSI) on the Li metal anode surface for highenergy Li metal pouch cells (Figure 1b). Contrasted with the original SEI film, MSI simultaneously possesses the properties of homogenizing Li-ion flux, high modulus, and high stability. The pouch cell assembled with the MSI protected Li metal anode (MSI-Li), high-area capacity LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathode Lithium (Li) metal has attracted unprecedented attention as the ultimate anode material for future rechargeable batteries, but the electrochemical behavior (such as Li dendrites and gassing problems) in real Li metal pouch cells has received little attention. To achieve realistic high-energy Li metal batteries, the designed solid electrolyte interface to suppress both Li dendrites and catastrophic gassing problems is urgently needed at cell level. Here, an efficient multifunctional silanization interfac...

Lithium-ion batteries (LIBs) with LiNixCoyMn1−x−yO2 (NCM) cathode are among the state-of-the-art batteries with high energy and power densities. NCM has been reported with issues of phase transition, volume change upon cycling and reacting with electrolyte. However, the possible degradation behaviors of NCM are still unclear when working at high state of charge (SOC) and elevated temperatures. In this work, life tests for commercial LiNi0.5Co0.2Mn0.3O2 (NCM523)/graphite cells are performed at high SOC (4.0–4.1 V or 4.1–4.2 V) and elevated temperature (45 °C) for the first time. The post-tested cells are characterized with multiple techniques to present a clear and comprehensive image of the cell degradations. The revealed degradation mechanisms of NCM cell at high SOC and high temperature include nikel (Ni) dissolution of NCM523, the formation of the oxidation layer of LixPOyFz on cathode particles and gas release from the oxidation of solvents in the electrolyte.