Lithium deposition behavior in hard carbon hosts:Optical microscopy and scanning electron microscopy study

Lithium(Li)metal is an ideal anode for the next generation high-energy-density batteries.However,it suffers from dendrite growth,side reactions,and infinite relative volume change.Effective strategies are using porous carbons or surface modification carbons to guide Li deposition into their pores.While the Li deposition behavior is still ambiguous.Here,we systematically determine their deposition behavior in various surface-modified carbons and in different electrolytes via optical microscopy and scanning electron microscopy study.It is found that Li will not spontaneously deposit into the carbon pores,which is significantly dependent on the carbon surface,current density,areal capacity,and electrolyte.Thus,a“lithiophilic”modified commercial hard carbon with Ag is developed as a stable“host”and efficient surface protection derived from the localized high-concentration electrolyte exhibits a pretty low volume change(5.3%)during cycling at a current density of 2 mA·cm^(−2)and an areal capacity of 2 mAh·cm^(−2).This strategy addresses the volume change and dendrite problems by rationally designed host and electrolyte,providing a broad perspective for realizing Li-metal anode.

Effect of Substrate Type on Deposition Behavior and Wear Performance of Ni-Coated Graphite/Al Composite Coatings Deposited by Cold Spraying

This work focused on the deposition characteristics and wear behavior of Ni-coated graphite mixed with40 vol.% Al（Ni-Gr/Al） composite coatings sprayed on an Al alloy and a steel substrate by cold spraying（CS）. The morphology of the flattened Ni-Gr particles was examined by single-impact tests. Crosssectional microstructure and wear performance of the Ni-Gr/Al composite coatings were studied. Results showed that a larger number of Ni-Gr particles were finally bonded with the steel substrate, whereas many craters existed on the Al alloy substrate after the single-impact tests. The coating on the steel substrate had a high thickness, high graphite content and low coeficient of friction（COF） compared to those on the Al alloy substrate. In addition, the CS coatings presented a homogeneous distribution and uniform morphology of graphite, and a comparative COF to that of conventional thermal sprayed coatings. It was shown that CS could avoid the decomposition and transformation of graphite phase.

Spray Deposition Behavior and Numerical Simulation of Growth of Tubular Preform in Spray Forming Process

Analysis on the deposition behavior of spray on deposition surface was made and an optimization method for the movement parameters （u, ω） of substrate was obtained. Simultaneously, a mathematical model of growth of tubular preform, specifically aimed at the kind of atomizer that is fixed and with a tilt angle was established. By in- tegrating the optimization method and the mathematical model, the growth process and shape of preform were simu- lated. The results show that the tilt angle of atomizer plays an important role on the dimensions and shapes of tubular preforms and it can provide a guidance for the development of spray forming equipment.

Effect of Deposition Time on Microstructures and Growth Behavior of ZrC Coatings Prepared by Low Pressure Chemical Vapor Deposition with the Br2-Zr-C3H6-H2-Ar System

ZrC coatings were deposited on graphite substrates by low pressure chemical vapor deposition（LPCVD） with the Br2-Zr-C3H6-H2-Ar system. The effects of deposition time on the microstructures and growth behavior of ZrC coatings were investigated. ZrC coating grew in an island-layer mode. The formation of coating was dominated by the nucleation of ZrC in the initial 20 minutes, and the rapid nucleation generated a fine-grained structure of ZrC coating. When the deposition time was over 30 min, the growth of coating was dominated by that of crystals, giving a column-arranged structure. Energy dispersive X-ray spectroscopy showed that the molar ratio of carbon to zirconium was near 1：1 in ZrC coating, and X-ray photoelectron spectroscopy showed that ZrC was the main phase in coatings, accompanied by about 2.5mol% ZrO2 minor phase.

A systematical study on the electrodeposition process of metallic lithium

In this study,commercial copper(Cu)foil and Cu foam are used as the working electrodes to systematically investigate the electrochemical deposition and dissolution processes of metallic lithium(Li)on these electrodes;Li metal deposited on the Cu foil electrode is porous and loose.The surface solid electrolyte interface(SEI)film after dissolution from Li dendrites maintains a dendritic porous structure,resulting in a large volume effect of the electrode during the cycle.The Cu foam electrode provides preferential nucleation and deposition sites near the side surface of the separator;the difference in Li affinity results in a heterogeneous deposition and dendrite growth of metallic Li.

Electrode structure enabling dendrite inhibition for high cycle stability quasi-solid-state lithium metal batteries

Lithium(Li)metal batteries(LMBs)are widely regarded as the ultimate choice for the next generation of high-energy–density batteries.However,the uncontrollable growth of Li dendrites formed by inhomogeneous deposition seriously hinders its commercialization.Although many studies have achieved significant results in inhibiting the formation of Li dendrites,it is still impossible to eradicate them completely.Therefore,regulating the deposition behavior,such as the growth direction of unevenly deposited Li,is preferable to unilaterally suppressing them in some cases.Here we report a structured anode that can confine the deposited Li within holes and tune it to become vertical-up/horizontal-centripetal mixed growth mode by optimizing the electric field/Li^(+)concentration gradient.The Li^(+) adsorbed by the poly(amic acid)(PAA)insulating layer coated on the anode surface can form the Li^(+)concentration gradient pointing to the center of the hole.Combined with the special electric field formed by the hole structure,it is favorable for the Li^(+)to move into the vertically arrayed holes and simultaneously deposit on the bottom and walls.Furthermore,both in-situ and ex-situ observations confirm that the growth mode is changed and the Li deposition morphology is denser,which can greatly delay capacity fading and prolong cycle life in both liquid and quasi-solid-state LMBs.All the results show that the novel anode provides a new perspective for deep research into solid-state LMBs.

Re-evaluating the nano-sized inorganic protective layer on Cu current collector for anode free lithium metal batteries

Anode free lithium metal batteries(AF-LMBs)have conspicuous advantages both in energy density and the compatibility of battery manufacturing process.However,the limited cycle life of AF-LMBs is a crucial factor hindering its practical application.Fluorinated or nitride artificial inorganic solid electrolyte interphase(SEI)has been found as an effective method to prolong the lifespan of AF-LMBs.Herein,by investigating the impact of nano-sized inorganic gradient layers(LiF or Li3N)on initial Li deposition behavior,we notice that the Li^(+) diffusion barrier and the deposition morphology are highly depended on the thickness of inorganic layers.Thicker protective layers cause larger overpotential as well as more aggregated Li^(+) distribution.This study reveals that the ideal SEI should be synthesized thin and uniformly enough and uncontrollable artificial SEI can cause damage to the lifespan of AF-LMBs.