Accurate estimation of Li/Ni mixing degree of lithium nickel oxide cathode materials

Li/Ni mixing negatively influences the discharge capacity of lithium nickel oxide and high-nickel ternary cathode materials.However,accurately measuring the Li/Ni mixing degree is difficult due to the preferred orientation of labbased XRD measurements using Bragg–Brentano geometry.Here,we find that employing spherical harmonics in Rietveld refinement to eliminate the preferred orientation can significantly decrease the measurement error of the Li/Ni mixing ratio.The Li/Ni mixing ratio obtained from Rietveld refinement with spherical harmonics shows a strong correlation with discharge capacity,which means the electrochemical capacity of lithium nickel oxide and high-nickel ternary cathode can be estimated by the Li/Ni mixing degree.Our findings provide a simple and accurate method to estimate the Li/Ni mixing degree,which is valuable to the structural analysis and screening of the synthesis conditions of lithium nickel oxide and high-nickel ternary cathode materials.

Mechanism of Capacity Fading Caused by Mn(Ⅱ)Deposition on Anodes for Spinel Lithium Manganese Oxide Cell

The capacity fade of spinel lithium manganese oxide in lithium-ion batteries is a bottleneck challenge for the large-scale application.The traditional opinion is that Mn（Ⅱ） ions in the anode are reduced to the metallic manganese that helps for catalyzing electrolyte decomposition.This could poison and damage the solid electrolyte interface（SEI） film,leading to the the capacity fade in Li-ion batteries.We propose a new mechanism that Mn（Ⅱ） deposites at the anode hinders and/or blocks the intercalation/de-intercalation of lithium ions,which leads to the capacity fade in Li-ion batteries.Based on the new mechanism assumption,a kind of new structure with core-shell characteristic is designed to inhabit manganese ion dissolution,thus improving electrochemical cycle performance of the cell.By the way,this mechanism hypothesis is also supported by the results of these experiments.The LiMn2-xTixO4 shell layer enhances cathode resistance to corrosion attack and effectively suppresses dissolution of Mn,then improves battery cycle performance with LiMn_2O_4 cathode,even at high rate and elevated temperature.

Critical role of corrosion inhibitors modified by silyl ether functional groups on electrochemical performances of lithium manganese oxides

Lithium manganese oxides(Li Mn2 O4, LMO) have attracted significant attention as important cathode materials for lithium-ion batteries(LIBs), which require fast charging based on their intrinsic electrochemical properties. However, these properties are limited by the rapid fading of cycling retention, particularly at high temperatures, because of the severe Mn corrosion triggered by the chemical reaction with fluoride(F-) species existing in the cell. To alleviate this issue, three types of silyl ether(Si–O)-functionalized task-specific additives are proposed, namely methoxytrimethylsilane, dimethoxydimethylsilane, and trimethoxymethylsilane. Ex-situ NMR analyses demonstrated that the Si-additives selectively scavenged the F-species as Si forms new chemical bonds with F via a nucleophilic substitution reaction due to the high binding affinity of Si with F-, thereby leading to a decrease in the F concentration in the cell. Furthermore, the addition of Si-additives in the electrolyte did not significantly affect the ionic conductivity or electrochemical stability of the electrolyte, indicating that these additives are compatible with conventional electrolytes. In addition, the cells cycled with Si-additives exhibited improved cycling retention at room temperature and 45 °C. Among these candidates, a combination of MTSi and the LMO cathode was found to be the most suitable choice in terms of cycling retention(71.0%), whereas the cell cycled with the standard electrolyte suffered from the fading of cycling retention triggered by Mn dissolution(64.4%). Additional ex-situ analyses of the cycled electrodes using SEM, TEM, EIS, XPS, and ICP-MS demonstrated that the use of Si-additives not only improved the surface stability of the LMO cathode but also that of the graphite anode, as the Si-additives prevent Mn corrosion. This inhibits the formation of cracks on the surface of the LMO cathode, facilitating the formation of a stable solid electrolyte interphase layer on the surface of the graphite anode. Therefore, Si-additives modified by Si–O functional groups can be effectively used to increase the overall electrochemical performance of the LMO cathode material.

Revealing the correlation between structure evolution and electrochemical performance of high-voltage lithium cobalt oxide

Lithium cobalt oxide(LCO)is the dominating cathode materials for lithium-ion batteries(LIBs)deployed in consumer electronic devices for its superior volumetric energy density and electrochemical performances.The constantly increasing demands of higher energy density urge to develop high-voltage LCO via a variety of strategies.However,the corresponding modification mechanism,especially the influence of the long-and short-range structural transitions at high-voltage on electrochemical performance,is still not well understood and needs further exploration.Based on ss-NMR,in-situ X-ray diffraction,and electrochemical performance results,it is revealed that the H3 to H1-3 phase transition dictates the structural reversibility and stability of LCO,thereby determining the electrochemical performance.The introduction of La and Al ions could postpone the appearance of H1-3 phase and induce various types of local environments to alleviate the volume variation at the atomic level,leading to better reversibility of the H1-3 phase and smaller lattice strain,and significantly improved cycle performance.Such a comprehensive long-range,local,and electronic structure characterization enables an in-depth understanding of the structural evolution of LCO,providing a guiding principle for developing high-voltage LCO for high energy density LIBs.

Unexpected Selective Absorption of Lithium in Thermally Reduced Graphene Oxide Membranes

Lithium plays an increasingly important role in scientific and industrial processes, and it is extremely important to extract lithium from a high Mg^(2+)/Li^(+) mass ratio brine or to recover lithium from the leachate of spent lithiumion batteries. Conventional wisdom shows that Li^(+) with low valence states has a much weaker adsorption(and absorption energy) with graphene than multivalent ions such as Mg^(2+). Here, we show the selective adsorption of Li^(+) in thermally reduced graphene oxide(rGO) membranes over other metal ions such as Mg^(2+), Co^(2+), Mn^(2+),Ni^(2+), or Fe^(2+). Interestingly, the adsorption strength of Li^(+) reaches up to 5 times the adsorption strength of Mg^(2+),and the mass ratio of a mixed Mg^(2+)/Li^(+) solution at a very high value of 500 : 1 can be effectively reduced to 0.7 : 1 within only six experimental treatment cycles, demonstrating the excellent applicability of the rGO membranes in the Mg^(2+)/Li^(+) separation. A theoretical analysis indicates that this unexpected selectivity is attributed to the competition between cation–π interaction and steric exclusion when hydrated cations enter the confined space of the rGO membranes.

Facile construction of a multilayered interface for a durable lithium‐rich cathode

Layered lithium-rich manganese-based oxide(LRMO)has the limitation of inevitable evolution of lattice oxygen release and layered structure transformation.Herein,a multilayer reconstruction strategy is applied to LRMO via facile pyrolysis of potassium Prussian blue.The multilayer interface is visually observed using an atomic-resolution scanning transmission electron microscope and a high-resolution transmission electron microscope.Combined with the electrochemical characterization,the redox of lattice oxygen is suppressed during the initial charging.In situ X-ray diffraction and the high-resolution transmission electron microscope demonstrate that the suppressed evolution of lattice oxygen eliminates the variation in the unit cell parameters during initial(de)lithiation,which further prevents lattice distortion during long cycling.As a result,the initial Coulombic efficiency of the modified LRMO is up to 87.31%,and the rate capacity and long-term cycle stability also improved considerably.In this work,a facile surface reconstruction strategy is used to suppress vigorous anionic redox,which is expected to stimulate material design in high-performance lithium ion batteries.

Upcycling the spent graphite/LiCoO_(2) batteries for high-voltage graphite/LiCoPO_(4)-co-workable dual-ion batteries

The worldwide proliferation of portable electronics has resulted in a dramatic increase in the number of spent lithium-ion batteries(LIBs).However,traditional recycling methods still have limitations because of such huge amounts of spent LIBs.Therefore,we proposed an ecofriendly and sustainable double recycling strategy to concurrently reuse the cathode(LiCoO_(2))and anode(graphite)materials of spent LIBs and recycled LiCoPO_(4)/graphite(RLCPG)in Li^(+)/PF^(-)_(6) co-de/intercalation dual-ion batteries.The recycle-derived dualion batteries of Li/RLCPG show impressive electrochemical performance,with an appropriate discharge capacity of 86.2 mAh·g^(-1) at25 mA·g^(-1) and 69%capacity retention after 400 cycles.Dual recycling of the cathode and anode from spent LIBs avoids wastage of resources and yields cathode materials with excellent performance,thereby offering an ecofriendly and sustainable way to design novel secondary batteries.

Spinel Phases LiRE_xMn_(2-x)O_4(RE=Nd, Ce) as Cathode for Rechargeable Lithium Batteries

Several series of LiRE x Mn 2-x O 4(RE=Ce, Nd) samples prepared at different contents and in different rare earth metals substitution were studied in order to further understand the dependence of the electrochemical performance on the doping rare earth metals. These cathodes were more tolerant to repeat lithium extraction and insertion than a standard LiMn 2O 4 spinel electrode in spite of a small reduction in the initial capacity. X ray photoelectron spectroscopy results show that the Mn 4+ contents for spinel LiMn 2O 4 directly affected the initial capacity and cyclability of LiMn 2O 4.

Effect of lithium content on the electrochemical properties of solid-state-synthesized spinel Li_xMn_2O_4

Lithium-substituted LixMn2O4 （x = 0.98, 1.03, 1.08） spinel samples were synthesized by solid-state reaction. X-ray diffraction （XRD） patterns show that the prepared samples have a spinel structure with a space group of Fd 3 m. The cubic lattice parameter was determined from least-squares fitting of the XRD data. Li1.03Mn2O4 shows high capacity at both low and high current densities, while Lil.08Mn2O4shows good cycling performance but relatively low capacity when cycled at both room and elevated temperatures. A variety of electrochemical methods were employed to investigate the electrochemical properties of these series of spinel LixMn2O4.

High power nano-LiMn_2O_4 cathode materials with high-rate pulse discharge capability for lithium-ion batteries

Nano-LiMn2O4 cathode materials with nano-sized particles are synthesized via a citric acid assisted sol-gel route. The structure, the morphology and the electrochemical properties of the nano-LiMn204 are investigated. Compared with the micro-sized LiMn2O4, the nano-LiMn2O4 possesses a high initial capacity （120 mAh/g） at a discharge rate of 0.2 C （29.6 mA/g）. The nano-LiMn2O4 also has a good high-rate discharge capability, retaining 91% of its capacity at a discharge rate of 10 C and 73~ at a discharge rate of 40 C. In particular, the nano-LiMn2O4 shows an excellent high-rate pulse discharge capability. The cut-off voltage at the end of 50-ms pulse discharge with a discharge rate of 80 C is above 3.40 V, and the voltage returns to over 4.10 V after the pulse discharge. These results show that the prepared nano-LiMn2O4 could be a potential cathode material for the power sources with the capability to deliver very high-rate pulse currents.

Dual-shell silicate and alumina coating for long lasting and high capacity lithium ion batteries

Here we demonstrate a theory-driven, novel dual-shell coating system of Li_(2)SrSiO_(4) and Al_(2)O_(3), achieved via a facile and scalable sol-gel technique on LiCoO_(2) electrode particles. The optimal thickness of each coating can lead to increased specific capacity(~185 m Ah/g at 0.5 C-rate) at a cut-off potential of 4.5 V, and greater cycling stability at very high C rates(up to 10 C) in half-cells with lithium metal. The mechanism of this superior performance was investigated using a combination of X-ray and electron characterization methods. It shows that the results of this investigation can inform future studies to identify still better dual-shell coating schemes, achieved by such industrially feasible techniques, for application on similar, nickel-rich cathode materials.

Synthesis and physicochemical properties of LiLa_(0.01)Mn_(1.99)O_(3.99)F_(0.01) cathode materials for lithium ion batteries

Spinel lithium manganese oxide cathode materials were synthesized using the ultrasonic-assisted sol-gel method. The synthesized samples were investigated by differential thermal analysis （DTA） and thermogravimetry （TG）, powder X-ray diffraction （XRD）, scanning electron microscopy （SEM）, cyclic voltammetry （CV）, and the charge-discharge test. TG-DTA shows that significant mass loss occurs in two temperature regions during the synthesis of LiLa0.01Mn1.9903.99F0.01. XRD data indicate that all samples exhibit the same pure spinel phase, and LiLa0.01Mn1.9903.99F0.01 and LiLa0.01Mn1.9904 samples have a better crystallinity than LiMn2O4. SEM images indicate that LiLa0.01Mn1.9903.99F0.01 has a slightly smaller particle size and a more regular morphology structure with narrow size distribution. The charge-discharge test reveals that the initial capacities of LiMn2O4, LiLa0.01Mn1.99O4, and LiLa0.01Mn1.99O3.99F0.01 are 130, 123, and 126 mAh·g^-1, respectively, and the capacity retention rates of the initial value, after 50 cycles, are 84.8%, 92.3%, and 92.1%, respectively. The electrode coulomb efficiency and CV reveal that the electrode synthesized by the ultrasonic-assisted sol-gel （UASG） method has a better re- versibility than the electrode synthesized by the sol-gel method.

Comparative study of LiNiO_2, LiNi_(0.8)Co_(0. 2)O_2 and LiNi_(0.75)Al_(0.25)O_2 for lithium-ion batteries

The comparative study of LiNi_(0.8)Co_(0.2)O_2 and LiNi_(0.75)A_(0.25)O_2 wascarried out by X-ray diffraction (XRD) and electrochemical methods. The results show that Co and Aldoping suppress the phase transition during charge-discharge. The experiments indi cate thatLiNi_(0.75)Al_(0.25)O_2 has the better cycle-ability and over-charge resistance comparing withLiNi_(0.8)Co_(0.2)O_2. The interfacial behavior was studied by use of electrochemical impedancespectroscopy (EIS). The results show that LiNi_(0.75)Al_(0.25)O_2 has a slightly larger polarizationcharacter than LiNi_(0.8)Co_(0.2)O_2.

Upcycling of spent LiCoO_(2) cathodes via nickel- and manganese-doping

Direct recycling has been regarded as one of the most promising approaches to dealing with the increasing amount of spent lithium‐ion batteries(LIBs).However,the current direct recycling method remains insufficient to regenerate outdated cathodes to meet current industry needs as it only aims at recovering the structure and composition of degraded cathodes.Herein,a nickel(Ni)and manganese(Mn)co‐doping strategy has been adopted to enhance LiCoO_(2)(LCO)cathode for next‐generation high‐performance LIBs through a conventional hydrothermal treatment combined with short annealing approach.Unlike direct recycling methods that make no changes to the chemical composition of cathodes,the unique upcycling process fabricates a series of cathodes doped with different contents of Ni and Mn.The regenerated LCO cathode with 5%doping delivers excellent electrochemical performance with a discharge capacity of 160.23 mAh g^(−1) at 1.0 C and capacity retention of 91.2%after 100 cycles,considerably surpassing those of the pristine one(124.05 mAh g^(−1) and 89.05%).All results indicate the feasibility of such Ni–Mn co‐doping‐enabled upcycling on regenerating LCO cathodes.

Nonlinear Electrical Properties of SnO_2-Li_2O-Nb_2O_5 Varistor System

The electrical properties of (Nb, Li)-doped SnO2 ceramics as a new varistor material were investigated. The sample 97.95%SnO2·0.50%Li2O·0.05%Nb2O5 (mol fraction) sintered at 1450= possess the highest density (ρ=6.77 g/cm3) and nonlinear electrical coefficient (α=11.6). The substitution of Sn4+ with Li+ increases the concentration of oxygen vacancies, together with the formation of solid solution, which will increase the sintering rate greatly and decrease the optimized sintering temperature. The substitution of Sn4+ with Li+ and the variation of temperature play very important effects on the densities, dielectric constant, nonlinear electrical properties and other characteristics of the samples. The properties of the grain boundary barrier and the microstructural characteristics were investigated to ensure the effect of the dopants and the temperature. A grain boundary defect barrier model was used to illustrate the grain boundary barriers formation in SnO2-Li2O-Nb2O5 varistors.

Synthesis and Electrochemical Studies on Spinel Phase LiMn_2O_4 Cathode Materials Prepared by Different Processes

Three kinds of processes, high temperature solid state reaction, precipitation and solgel technique were used to synthsize spinel phase LiMn2O4. XRD, DTATG results show that phasepure spinel LiMn2O4 could be synthesized under the lowest calcined temperature by the solgel technique compared to the precipitation method and solid state reaction. BET, SEM and electrochemical measurements results demonstrate that the features of the powders affect directly the electrochemical capacities; large specific area and small homogeneous grain size are of advantage for the lithium ion insertion and extraction in the charge and discharge process.

Carbon combustion synthesis of lithium cobalt oxide as cathode material for lithium ion battery

Lithium cobalt oxide （LiCoO2） was synthesized by carbon combustion synthesis （CCS） using carbon as fuel. X-ray diffraction （XRD） and scanning electron microscope （SEM） measurements showed that carbon combustion led to the formation of layered structure of LiCoO2 and the particle size could be controlled by carbon content. For the LiCoO2 sample prepared at 800℃ for 2 h, at molar ratio of C/Co = 0.5, the particle-size distribution fell in the narrow range of 3-5 μm. Electrochemical tests indicated this LiCoO2 sample delivered an initial discharge capacity of 148 mAh/g with capacity retention rate higher than 97% after 10 cycles.

Improved electrochemical performances of high voltage LiCoO_2 with tungsten doping

The effects of tungsten W doping and coating on the electrochemical performance of LiCoO2 cathode are compara- tively studied in this work. The amount of modification component is as low as 0.1 wt% and 0.3 wt% respectively. After 100 cycles between 3.0 V-4.6 V, 0.1 wt% W doping provides an optimized capacity retention of 72.3%. However, W coating deteriorates battery performance with capacity retention of 47.8%, even lower than bare LiCoO2 of 55.7%. These different electrochemical performances can be attributed to the surface aggregation of W between doping and coating methods. W substitution is proved to be a promising method to develop high voltage cathodes. Practical performance relies on detailed synthesis method.

Enhanced high temperature cycling performance of LiMn_2O_4/graphite cells with methylene methanedisulfonate(MMDS) as electrolyte additive and its acting mechanism

The effects of methylene methanedisulfonate（MMDS） on the high-temperature（0℃） cycle performance of LiMnO/graphite cells are investigated.By addition of 2 wt%MMDS into a routine electrolyte,the high-temperature cycling performance of LiMn204/graphite cells can be significantly improved.The analysis of differential capacity curves and energy-dispersive X-ray spectrometry（EDX） indicates that MMDS decomposed on both cathode and anode.The three-electrode system of pouch cell is used to reveal the capacity loss mechanism in the cells.It is shown that the capacity fading of cells without MMDS in the electrolytes is due to irreversible lithium consumption during cycling and irreversible damage of LiMnOmaterial,while the capacity fading of cell with 2 wt%MMDS in electrolytes mainly originated from irreversible lithium consumption during cycling.

Characterization and Electrochemical Properties of LiMn_2O_4 Thin Films Prepared by Solution Deposition

LiMn2O4 thin films were prepared by solution deposition using lithium acetate and manganese acetate us raw materials. The phase constitution and surface morphalogy were observed by X-ray diffraction and scanning electron microscopy. The electrochemical properties of the thin films were studied by cycilc voltammetry, charge- discharge experiments and impedance spectroscopy in 1 mol· L^-1 LiPF6 / EC- DMC solution using lithium metal as both the counter and reference electrodes. The films prepared by this method are of spinel phase. The lattice parameter increases with the annealing temperature aud annealing time. The film annealed at 750 ℃ for 30 minutes has the highest capacity of 34.5 μAh ·cm^- 2·μm^-1 , and its capacity loss per cycle is 0. 05% afrer being cycled 100 times.