Unraveling the reaction reversibility and structure stability of nickel sulfide anodes for lithium ion batteries

The electrochemical performance of lithium-ion batteries,i.e.specific capacity and cyclability,is primarily determined by chemical reversibility and structural stability of the electrodes in cycling.Here we have investigated the fundamental reaction behaviors of nickel sulfide(NixSy)as lithium-ion battery anodes by in-situ TEM.We find that Ni_(3)S_(2)is the electrochemically stable phase,which appears in the first cycle of the NixSyanode.From the second cycle,conversion between Ni_(3)S_(2)and Li_(2)S/Ni is the dominant electrochemical reaction.In lithiation,the NixSynanoparticles evolve into a mixture of Ni nanocrystals embedded in Li_(2)S matrix,which form a porous structure upon full lithiation,and with the recrystallization of the Ni_(3)S_(2)phase in delithiation,a compact and interconnected network is built.Structural stability in cycles is susceptible to particle size and substrate restraint.Carbon substrate can certainly improve the tolerance for size-dependent pulverization of NixSynanoparticles.When NixSynanoparticle exceeds the critical size value,the morphology of the particle is no longer well maintained even under the constraints of the carbon substrate.This work deepens the understanding of electrochemical reaction behavior of conversiontype materials and helps to rational design of high-energy density battery anodes.

镍精矿除铜的单纯形优化

本文简要叙述了单纯形优化的基本思想与寻优步骤。应用单纯形法对镍精矿—阳极泥—镍电解阳极液反应体系的深度除铜条件进行了寻优试验,其结果与前人的试验及工业实践基本相同,表明单纯形优化方法是确定多变量湿法冶金体系中某些重要因素的一种快速而简单的方法。

Three-dimensional antimony sulfide anode with carbon nanotube interphase modified for lithium-ion batteries

Antimony sulfide(Sb_(2)S_(3))is a promising anode for lithium-ion batteries due to its high capacity and vast reserves.However,the low electronic conductivity and severe volume change during cycling hinder its commercialization.Herein our work,a three-dimensional(3D)Sb_(2)S_(3) thin film anode was fabricated via a simple vapor transport deposition system by using natural stibnite as raw material and stainless steel fiber-foil(SSF)as 3D current collector,and a carbon nanotube interphase was introduced onto the film surface by a simple dropping-heating process to promote the electrochemical performances.This 3D structure can greatly improve the initial coulombic efficiency to a record of 86.6% and high reversible rate capacity of 760.8 mAh·g^(-1) at 10 C.With carbon nanotubes interphase modified,the Sb_(2)S_(3) anode cycled extremely stable with high capacity retention of 94.7% after 160 cycles.This work sheds light on the economical preparation and performance optimization of Sb_(2)S_(3)-based anodes.

Electrolyte/Structure‑Dependent Cocktail Mediation Enabling High‑Rate/Low‑Plateau Metal Sulfide Anodes for Sodium Storage

As promising anodes for sodium-ion batteries,metal sulfides ubiquitously suffer from low-rate and high-plateau issues,greatly hindering their application in full-cells.Herein,exemplifying carbon nanotubes(CNTs)-stringed metal sulfides superstructure(CSC)assembled by nano-dispersed SnS_(2) and CoS_(2) phases,cocktail mediation effect similar to that of high-entropy materials is initially studied in ether-based electrolyte to solve the challenges.The high nano-dispersity of metal sulfides in CSC anode underlies the cocktail-like mediation effect,enabling the circumvention of intrinsic drawbacks of different metal sulfides.By utilizing ether-based electrolyte,the reversibility of metal sulfides is greatly improved,sustaining a long-life effectivity of cocktail-like mediation.As such,CSC effectively overcomes low-rate flaw of SnS_(2) and highplateau demerit of CoS_(2),simultaneously realizes a high rate and a low plateau.In half-cells,CSC delivers an ultrahigh-rate capability of 327.6 mAh g^(−1) anode at 20 A g^(−1),far outperforming those of monometallic sulfides(SnS_(2),CoS_(2))and their mixtures.Compared with CoS_(2) phase and SnS_(2)/CoS_(2) mixture,CSC shows remarkably lowered average charge voltage up to ca.0.62 V.As-assembled CSC//Na1.5VPO4.8F0.7 full-cell shows a good rate capability(0.05~1.0 A g^(−1),120.3 mAh g^(−1) electrode at 0.05 A g^(−1))and a high average discharge voltage up to 2.57 V,comparable to full-cells with alloy-type anodes.Kinetics analysis verifies that the cocktail-like mediation effect largely boosts the charge transfer and ionic diffusion in CSC,compared with single phase and mixed phases.Further mechanism study reveals that alternative and complementary electrochemical processes between nano-dispersed SnS_(2) and CoS_(2) phases are responsible for the lowered charge voltage of CSC.This electrolyte/structure-dependent cocktail-like mediation effect effectively enhances the practicability of metal sulfide anodes,which will boost the development of high-rate/-voltage sodium-ion full batteries.

Nanostructured Bi2S3 encapsulated within three- dimensional N-doped graphene as active and flexible anodes for sodium-ion batteries

Sodium-ion batteries （SIBs） have been increasingly attracting attention as a sustainable alternative to lithium-ion batteries for scalable energy storage. The key to advanced SIBs relies heavily upon the development of reliable anodes. In this respect, Bi2S3 has been extensively investigated because of its high capacity, tailorable morpholog, and low cost However, the common practices of incorporating carbon species to enhance the electrical conductivity and accommodate the volume change of Bi2S3 anodes so as to boost their durability for Na storage have met with limited success. Herein, we report a simple method to realize the encapsulation of Bi2S3 nanorods within three-dimensional, nitrogen-doped graphene （3DNG） frameworks, targeting flexible and active composite anodes for SIBs. The Bi2S3/ 3DNG composites displayed outstanding Na storage behavior with a high reversible capacity （649 mAh·g^-1 at 62.5 mA·g^-1） and favorable durability （307 and 200 mAh·g^-1 after 100 cycles at 125 and 312.5 mA·g^-1, respectively）. In-depth characterization by in situ X-ray diffraction revealed that the intriguing Na storage process of Bi2Sa was based upon a reversible reaction. Furthermore, a full, flexible SIB cell with Na0.4MnO2 cathode and as-prepared composite anode was successfully assembled, and holds a great promise for next-generation, wearable energy storage applications.