Atomic Layer Deposition Derived Zirconia Coatings on Ni‐Rich Cathodes in Solid‐State Batteries: Correlation Between Surface Constitution and Cycling Performance

Protective coatings are required to address interfacial incompatibility issues in composite cathodes made from Ni-rich layered oxides and lithium thiophosphate solid electrolytes (SEs), one of the most promising combinations of materials for high energy and power density solid-state battery (SSB) applications. Herein, the preparation of conformal ZrO2 nanocoatings on a LiNi0.85Co0.10Mn0.05O2 (NCM85) cathode-active material (CAM) by atomic layer deposition (ALD) is reported and the structural and chemical evolution of the modified NCM85 upon heat treatment—a post-processing step often required to boost battery performance—is investigated. The coating properties are shown to have a strong effect on the cyclability of high-loading SSB cells. After mild annealing (≈400 °C), the CAM delivers high specific capacities (≈200 mAh g−1 at C/10) and exhibits improved rate capability (≈125 mAh g−1 at 1C) and stability (≈78% capacity retention after 200 cycles at 0.5C), enabled by effective surface passivation. In contrast, annealing temperatures above 500 °C lead to the formation of an insulating interphase that negatively affects the cycling performance. The results of this study demonstrate that the preparation conditions for a given SE/CAM combination need to be tailored carefully and ALD is a powerful surface-engineering technique toward this goal

Unraveling the Electrochemical Mechanism in Tin Oxide/MXene Nanocomposites as Highly Reversible Negative Electrodes for Lithium-Ion Batteries

Lithium-ion batteries are constantly developing as the demands for power and energy storage increase. One promising approach to designing high-performance lithium-ion batteries is using conversion/alloying materials, such as SnO2. This class of materials does, in fact, present excellent performance and ease of preparation; however, it suffers from mechanical instabilities during cycling that impair its use. One way to overcome these problems is to prepare composites with bi-dimensional materials that stabilize them. Thus, over the past 10 years, two-dimensional materials with excellent transport properties (graphene, MXenes) have been developed that can be used synergistically with conversion materials to exploit both advantages. In this work, a 50/50 (by mass) SnO2/Ti3C2Tz nanocomposite is prepared and optimized as a negative electrode for lithium-ion batteries. The nanocomposite delivers over 500 mAh g−1 for 700 cycles at 0.1 A g−1 and demonstrates excellent rate capability, with 340 mAh g−1 at 8 A g−1. These results are due to the synergistic behavior of the two components of the nanocomposite, as demonstrated by ex situ chemical, structural, and morphological analyses. This knowledge allows, for the first time, to formulate a reaction mechanism with lithium-ions that provides partial reversibility of the conversion reaction with the formation of SnO

Unraveling the Electrochemical Mechanism in Tin Oxide/MXene Nanocomposites as Highly Reversible Negative Electrodes for Lithium‐Ion Batteries

Lithium-ion batteries are constantly developing as the demands for power and energy storage increase. One promising approach to designing high-performance lithium-ion batteries is using conversion/alloying materials, such as SnO2. This class of materials does, in fact, present excellent performance and ease of preparation; however, it suffers from mechanical instabilities during cycling that impair its use. One way to overcome these problems is to prepare composites with bi-dimensional materials that stabilize them. Thus, over the past 10 years, two-dimensional materials with excellent transport properties (graphene, MXenes) have been developed that can be used synergistically with conversion materials to exploit both advantages. In this work, a 50/50 (by mass) SnO2/Ti3C2Tz nanocomposite is prepared and optimized as a negative electrode for lithium-ion batteries. The nanocomposite delivers over 500 mAh g−1 for 700 cycles at 0.1 A g−1 and demonstrates excellent rate capability, with 340 mAh g−1 at 8 A g−1 . These results are due to the synergistic behavior of the two components of the nanocomposite, as demonstrated by ex situ chemical, structural, and morphological analyses. This knowledge allows, for the first time, to formulate a reaction mechanism with lithium-ions that provides partial reversibility of the conversion reaction with the formation of SnO

SiOₓ coated graphite with inorganic aqueous binders as high-performance anode for lithium-ion batteries

Inorganic aqueous binders (IAB) are an emerging class of aqueous binders. They offer exceptional physico- chemical properties like intrinsic ionic conductivity, high thermal stability (>1000 ◦C), and environmental benignity making them attractive. In a previous study, we found that graphite anode shows improved electro- chemical performance with these binders as compared to conventional PVDF binder for lithium-ion batteries (LIB). However, the cyclic performance of graphite-IAB at a higher rate (e.g., 1C) showed a declining trend. We attributed it to the poor binding strength between graphite and IAB due to insufficient functional groups in graphite. Therefore, in this report SiOx-based surface coatings of graphite are employed to improve its rate capability with silicate-based IAB by providing functional silicon oxide polymorphs on the coated graphite as an intermediate layer. The nature and structural arrangement of these coatings are investigated by tip-enhanced Raman spectroscopy (TERS), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Optimized SiOx-coated graphite (GS) with sodium metasilicate binder leads to excellent cyclic stability with a capacity retention of >90 % at 20C for >4000 cycles. A high specific capacity of >315 mAhg 1 at 2C, stable for over 1000 cycles, is achieved for GS with IAB. The improved performance of the coated graphite is attributed to ameliorated binding with IAB as well as stable solid electrolyte interphase. We propose inorganic aqueous binders in combination with SiOx-coated graphite as an approach to realize a stable anode for LIB

A Quasi‐Multinary Composite Coating on a Nickel‐Rich NCM Cathode Material for All‐Solid‐State Batteries

Inorganic solid-state batteries are attracting significant interest as a contender to conventional liquid electrolyte-based lithium-ion batteries but still suffer from several limitations. The search for advanced coatings for protecting cathode materials in solid-state batteries to achieve interfacial stability is a continuing challenge. In the present work, the surface of an industrially relevant Ni-rich LiNi$_x$Co$_y$Mn$_z$O$_2$ cathode material, NCM-851005 (85 % Ni), was modified by applying a coating containing Li, Nb and Zn, aiming at a composition Li$_6$ZnNb$_4$O$_14$, by means of sol-gel chemistry. Detailed characterization using scanning transmission electron microscopy combined with energy-dispersive X-ray spectroscopy and nano-beam electron diffraction showed that the surface layer after heating in O$_2$ at 500 °C contains Li$_3$NbO$_4$ nanocrystals and Li$_2$CO$_3$, with Zn presumably acting as a dopant. The protective coating on the NCM-851005 secondary particles significantly increased the cycling performance (reversible capacity, rate capability etc.) and stability of full cells using argyrodite Li$_6$PS$_5$Cl as solid electrolyte. Interestingly, the level of improvement is superior to that achieved with conventional LiNbO$_3$ coatings

In situ Observation of Sodium Dendrite Growth and Concurrent Mechanical Property Measurements Using an Environmental Transmission Electron Microscopy–Atomic Force Microscopy (ETEM-AFM) Platform

Akin to Li, Na deposits in a dendritic form to cause a short circuit in Na metal batteries. However, the growth mechanisms and related mechanical properties of Na dendrites remain largely unknown. Here we report real-time characterizations of Na dendrite growth with concurrent mechanical property measurements using an environmental transmission electron microscopy–atomic force microscopy (ETEM-AFM) platform. In situ electrochemical plating produces Na deposits stabilized with a thin Na2CO3 surface layer (referred to as Na dendrites). These Na dendrites have characteristic dimensions of a few hundred nanometers and exhibit different morphologies, including nanorods, polyhedral nanocrystals, and nanospheres. In situ mechanical measurements show that the compressive and tensile strengths of Na dendrites with a Na2CO3 surface layer vary from 36 to >203 MPa, which are much larger than those of bulk Na. In situ growth of Na dendrites under the combined overpotential and mechanical confinement can generate high stress in these Na deposits. These results provide new baseline data on the electrochemical and mechanical behavior of Na dendrites, which have implications for the development of Na metal batteries toward practical energy-storage applications