Hong Li

Name:

Organization: Institute of Physics

Department: Department of Mechanical Engineering and Materials Science

Title:

Chemicals
References

In Situ Atomic-Scale Observation of Electrochemical Delithiation Induced Structure Evolution of LiCoO2 Cathode in a Working All-Solid-State Battery

Co-reporter:Yue Gong, Jienan Zhang, Liwei Jiang, Jin-An Shi, Qinghua Zhang, Zhenzhong Yang, Dongli Zou, Jiangyong Wang, Xiqian Yu, Ruijuan Xiao, Yong-Sheng Hu, Lin Gu, Hong Li, and Liquan Chen

Journal of the American Chemical Society March 29, 2017 Volume 139(Issue 12) pp:4274-4274

Publication Date(Web):March 8, 2017

DOI:10.1021/jacs.6b13344

We report a method for in situ atomic-scale observation of electrochemical delithiation in a working all-solid-state battery using a state-of-the-art chip based in situ transmission electron microscopy (TEM) holder and focused ion beam milling to prepare an all-solid-state lithium-ion battery sample. A battery consisting of LiCoO2 cathode, LLZO solid state electrolyte and gold anode was constructed, delithiated and observed in an aberration corrected scanning transmission electron microscope at atomic scale. We found that the pristine single crystal LiCoO2 became nanosized polycrystal connected by coherent twin boundaries and antiphase domain boundaries after high voltage delithiation. This is different from liquid electrolyte batteries, where a series of phase transitions take place at LiCoO2 cathode during delithiation. Both grain boundaries become more energy favorable along with extraction of lithium ions through theoretical calculation. We also proposed a lithium migration pathway before and after polycrystallization. This new methodology could stimulate atomic scale in situ scanning/TEM studies of battery materials and provide important mechanistic insight for designing better all-solid-state battery.

Side-by-side observation of the interfacial improvement of vertical graphene-coated silicon nanocone anodes for lithium-ion batteries by patterning technology

Co-reporter:Chao Wang;Fei Luo;Hao Lu;Bonan Liu;Geng Chu;Baogang Quan;Junjie Li;Changzhi Gu;Liquan Chen

Nanoscale (2009-Present) 2017 vol. 9(Issue 44) pp:17241-17247

Publication Date(Web):2017/11/16

DOI:10.1039/C7NR04041E

We report that vertical graphene coating can greatly improve the electrochemical performance and the interfacial stability of silicon nanocone (SNC) anodes for lithium-ion batteries. The coating patterning technology is innovatively employed for side-by-side demonstration of the exclusive influences of graphene coating on the solid–electrolyte interphase (SEI) formation and the structural stability of the SNC electrode. The silicon nanocone–graphene (SNC-G) electrode achieves a longer cycle life (1715 cycles), higher Coulombic efficiency (average 98.2%), better rate capability, and lower electrode polarization than the SNC electrode. The patterning of the graphene coating provides a much direct and convincing morphological comparison between the SNC-G structure and the SNC structure, showing clearly that the SNC-G area maintains a thin SEI layer and stable nanostructure after cycling, while the SNC area is gradually damaged and covered with a thick SEI layer after 100 cycles. Our results clearly indicate the improved electrochemical performance and interfacial stability attributed to the vertical graphene coating, and the as-proposed patterning technology also paves a new way for comparative research on coating materials for lithium-ion batteries.

Data mining-aided materials discovery and optimization

Co-reporter:Wencong Lu, Ruijuan Xiao, Jiong Yang, Hong Li, Wenqing Zhang

Journal of Materiomics 2017 Volume 3, Issue 3(Volume 3, Issue 3) pp:

Publication Date(Web):1 September 2017

DOI:10.1016/j.jmat.2017.08.003

•Both qualitative and quantitative methods adopted widely in materials data mining (MDM) have been systematically reviewed to meet different tasks of materials discovery and optimization.•The novel qualitative method by using optimal projection recognition technique is reviewed in detail for controllable synthesis of dendritic Co3O4 superstructures based on pattern recognition classification diagram.•The detailed MDM process has been demonstrated in case study on materials design of layered double hydroxide with desired basal spacing based on the quantitative modelling method called relevance vector machine.•The state-of-the-arts of data mining-aided battery materials discovery and thermoelectric materials design have been reviewed, indicating that MDM approach may play a more important role to discover novel materials in future.Recent developments in data mining-aided materials discovery and optimization are reviewed in this paper, and an introduction to the materials data mining (MDM) process is provided using case studies. Both qualitative and quantitative methods in machine learning can be adopted in the MDM process to accomplish different tasks in materials discovery, design, and optimization. State-of-the-art techniques in data mining-aided materials discovery and optimization are demonstrated by reviewing the controllable synthesis of dendritic Co3O4 superstructures, materials design of layered double hydroxide, battery materials discovery, and thermoelectric materials design. The results of the case studies indicate that MDM is a powerful approach for use in materials discovery and innovation, and will play an important role in the development of the Materials Genome Initiative and Materials Informatics.Download high-res image (348KB)Download full-size image

Explore the Effects of Microstructural Defects on Voltage Fade of Li- and Mn-Rich Cathodes

Co-reporter:Enyuan Hu, Yingchun Lyu, Huolin L. Xin, Jue Liu, Lili Han, Seong-Min Bak, Jianming Bai, Xiqian Yu, Hong Li, and Xiao-Qing Yang

Nano Letters 2016 Volume 16(Issue 10) pp:5999-6007

Publication Date(Web):September 26, 2016

DOI:10.1021/acs.nanolett.6b01609

Li- and Mn-rich (LMR) cathode materials have been considered as promising candidates for energy storage applications due to high energy density. However, these materials suffer from a serious problem of voltage fade. Oxygen loss and the layered-to-spinel phase transition are two major contributors of such voltage fade. In this paper, using a combination of X-ray diffraction (XRD), pair distribution function (PDF), X-ray absorption (XAS) techniques, and aberration-corrected scanning transmission electron microscopy (STEM), we studied the effects of micro structural defects, especially the grain boundaries, on the oxygen loss and layered-to-spinel phase transition through prelithiation of a model compound Li2Ru0.5Mn0.5O3. It is found that the nanosized micro structural defects, especially the large amount of grain boundaries created by the prelithiation can greatly accelerate the oxygen loss and voltage fade. Defects (such as nanosized grain boundaries) and oxygen release form a positive feedback loop, promote each other during cycling, and accelerate the two major voltage fade contributors: the transition metal reduction and layered-to-spinel phase transition. These results clearly demonstrate the important relationships among the oxygen loss, microstructural defects and voltage fade. The importance of maintaining good crystallinity and protecting the surface of LMR material are also suggested.Keywords: lithium-ion battery; microstructural defect; prelithiation; voltage fade;

Synthesis and ionic transport mechanisms of α-LiAlO2

Co-reporter:Jian Gao, Siqi Shi, Ruijuan Xiao, Hong Li

Solid State Ionics 2016 Volume 286() pp:122-134

Publication Date(Web):March 2016

DOI:10.1016/j.ssi.2015.12.028

•Pure phase α-LiAlO2 is synthesized.•Room-temperature ionic conductivity of the α-LiAlO2 sample is as low as 10− 21 S·cm− 1.•Defect formation and migration energy of α-LiAlO2 with bias voltage are calculated.•Bias voltage can enhance conductivity of α-LiAlO2.The pure phase α-LiAlO2 is synthesized by a solid-state reaction. The obtained product has nanocrystalline structure with the Li deficient regions near the surfaces. Combining X-ray diffraction (XRD) and thermogravimetry-differential scanning calorimetry (TG-DSC), the synthesis mechanism is revealed. The measured room-temperature ionic conductivity of the α-LiAlO2 ceramic pellet is as low as 10− 21 S·cm− 1. This could be caused by the absence of conduction pathways, as calculated from the bond-valence (BV) method. In addition, a first-principles calculation is performed. The calculated result suggests that although the α-LiAlO2 bulk has the extremely low ionic conductivity, its ionic conductivity could be increased significantly when applied the bias voltage, which is due to the introduction of external lithium sources (lithium reservoirs of interstitials/vacancies) and external charge sources (electrons/holes). This may explain why α-LiAlO2 as the coating layer on cathode for Li-ion batteries does not block the transport of lithium ions.The bulk α-LiAlO2 has no conductive channels, resulting in low ionic conductivity of 10− 21 S·cm− 1, where the bias voltage enhances its concentration of defects and promotes oriented hopping of mobile carriers, the ionic conductivity increases to 10− 11 S·cm− 1.

Toxicity, a serious concern of thermal runaway from commercial Li-ion battery

Co-reporter:Jie Sun, Jigang Li, Tian Zhou, Kai Yang, Shouping Wei, Na Tang, Nannan Dang, Hong Li, Xinping Qiu, Liquan Chen

Nano Energy 2016 Volume 27() pp:313-319

Publication Date(Web):September 2016

DOI:10.1016/j.nanoen.2016.06.031

•Large amount of toxic compounds were first time detected due to this in-situ GC-Mass analysis.•The 100% SOC is the most dangerous state in terms of toxicity.•The CO concentration increases sharply with capacities, however, the organic products' concentrations do not.•Figure out how long the escape time could be obtained for a fire emergency in thermal runaway.The toxicity analysis of combustion products from commercialized Li-ion batteries was performed in this work. More than 100 emitted gaseous products are identified, most of which are hazardous to the human beings and trigger negative impact on the environment. Moreover, the states of charge of battery was found to significantly affect the types of toxic combustion products, and the 100% state of charge even led to the most serious toxicity. The relationship between the concentration of toxic combustion products and battery capacity was also investigated. Interestingly, the concentration of carbon monoxide rose up rapidly up on the increase of the capacity instead of the toxic organic products. This investigation suggests that the efforts on effective battery emergency response could be potentially simplified to achieve cost down for manufacturers.Large amount of very toxic and highly toxic compounds were first time detected due to this in-situ GC-Mass analysis. A comprehensive spectrum associating with toxity of LIBs combustion were also established. The toxic emissions are highly depending on the battery materials, cell capacity, and SOC. The 100% SOC is the most dangerous state in terms of toxicity.The concentrations of CO increases sharply with capacities, however, the concentrations of combustion organic products do not show obvious raise compared to CO, but keep at the level of several ppm. So, it could be predicted that CCO would grow rapidly with capacity increasing, but the concentrations of new toxic COPs not. However, it was still noted strongly that the manufactures should chose less capacity cell but not larger capacity cell for EV considering the thermal runaway combustion toxicity. A cell with larger capacity, much more CO it will release in a limit and sealed space combustion.

Probing Reversible Multielectron Transfer and Structure Evolution of Li1.2Cr0.4Mn0.4O2 Cathode Material for Li-Ion Batteries in a Voltage Range of 1.0–4.8 V

Co-reporter:Yingchun Lyu, Nijie Zhao, Enyuan Hu, Ruijuan Xiao, Xiqian Yu, Lin Gu, Xiao-Qing Yang, and Hong Li

Chemistry of Materials 2015 Volume 27(Issue 15) pp:5238

Publication Date(Web):July 8, 2015

DOI:10.1021/acs.chemmater.5b01362

Li1.2Cr0.4Mn0.4O2 (0.4LiCrO2·0.4Li2MnO3) is an interesting intercalation-type cathode material with high theoretical capacity of 387 mAh g–1 based on multiple-electron transfer of Cr3+/Cr6+. In this work, it has been demonstrated that the reversible Cr3+/Cr6+ redox reaction can only be realized in a wide voltage range between 1.0 and 4.8 V. This is mainly due to large polarization during the discharge. The reversible migration of the Cr ions between octahedral and tetrahedral sites leads to large extent of cation mixing between lithium and transition metal layers, which does not affect the lithium storage capacity and stabilize the structure. In addition, a distorted spinel phase (Li3M2O4) is identified in the deeply discharged sample (1.0 V, Li1.5Cr0.4Mn0.4O2). The above results can explain the high reversible capacity and high structural stability achieved on Li1.2Cr0.4Mn0.4O2. These new findings will provide further in depth understanding on multielectron transfer and local structure stabilization mechanisms in intercalation chemistry, which are essential for understanding and developing a high capacity intercalation-type cathode for next generation high energy density Li-ion batteries.

Thick solid electrolyte interphases grown on silicon nanocone anodes during slow cycling and their negative effects on the performance of Li-ion batteries

Co-reporter:Fei Luo, Geng Chu, Xiaoxiang Xia, Bonan Liu, Jieyun Zheng, Junjie Li, Hong Li, Changzhi Gu and Liquan Chen

Nanoscale 2015 vol. 7(Issue 17) pp:7651-7658

Publication Date(Web):23 Mar 2015

DOI:10.1039/C5NR00045A

Thickness, homogeneity and coverage of the surface passivation layer on Si anodes for Li-ion batteries have decisive influences on their cyclic performance and coulombic efficiency, but related information is difficult to obtain, especially during cycling. In this work, a well-defined silicon nanocone (SNC) on silicon wafer sample has been fabricated as a model electrode in lithium ion batteries to investigate the growth of surface species on the SNC electrode during cycling using ex situ scanning electronic microscopy. It is observed that an extra 5 μm thick layer covers the top of the SNCs after 25 cycles at 0.1 C. This top layer has been proven to be a solid electrolyte interphase (SEI) layer by designing a solid lithium battery. It is noticed that the SEI layer is much thinner at a high rate of 1 C. The cyclic performance of the SNCs at 1 C looks much better than that of the same electrode at 0.1 C in the half cell. Our findings clearly demonstrate that the formation of the thick SEI on the naked nanostructured Si anode during low rate cycling is a serious problem for practical applications. An in depth understanding of this problem may provide valuable guidance in designing Si-based anode materials.

Rechargeable Li/CO2–O2 (2:1) battery and Li/CO2 battery

Co-reporter:Yali Liu, Rui Wang, Yingchun Lyu, Hong Li and Liquan Chen

Energy & Environmental Science 2014 vol. 7(Issue 2) pp:677-681

Publication Date(Web):11 Nov 2013

DOI:10.1039/C3EE43318H

A Li/CO2–O2 (2:1, volume ratio) battery and a Li/CO2 battery with discharging specific capacities of 1808 mA h g−1 and 1032 mA h g−1, respectively, are reported. Li2CO3 is the main discharge product in the Li/CO2–O2 (2:1) battery and can be decomposed during charging. In the Li/CO2 battery, the main discharge products could be Li2CO3 and carbon. Both batteries can be cycled reversibly at room temperature.

Understanding the Rate Capability of High-Energy-Density Li-Rich Layered Li1.2Ni0.15Co0.1Mn0.55O2 Cathode Materials

Co-reporter:Xiqian Yu;Yingchun Lyu;Lin Gu;Huiming Wu;Seong-Min Bak;Yongning Zhou;Khalil Amine;Steven N. Ehrlich;Kyung-Wan Nam;Xiao-Qing Yang

Advanced Energy Materials 2014 Volume 4( Issue 5) pp:

Publication Date(Web):

DOI:10.1002/aenm.201300950

The high-energy-density, Li-rich layered materials, i.e., xLiMO₂(1-x)Li₂MnO₃, are promising candidate cathode materials for electric energy storage in plug-in hybrid electric vehicles (PHEVs) and electric vehicles (EVs). The relatively low rate capability is one of the major problems that need to be resolved for these materials. To gain insight into the key factors that limit the rate capability, in situ X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) studies of the cathode material, Li_1.2Ni_0.15Co_0.1Mn_0.55O₂ [0.5Li(Ni_0.375Co_0.25 Mn_0.375)O₂·0.5Li₂MnO₃], are carried out. The partial capacity contributed by different structural components and transition metal elements is elucidated and correlated with local structure changes. The characteristic reaction kinetics for each element are identified using a novel time-resolved XAS technique. Direct experimental evidence is obtained showing that Mn sites have much poorer reaction kinetics both before and after the initial activation of Li₂MnO₃, compared to Ni and Co. These results indicate that Li₂MnO₃ may be the key component that limits the rate capability of Li-rich layered materials and provide guidance for designing Li-rich layered materials with the desired balance of energy density and rate capability for different applications.

Size-Dependent Staging and Phase Transition in LiFePO4/FePO4

Co-reporter:Changbao Zhu;Lin Gu;Liumin Suo;Jelena Popovic;Yuichi Ikuhara;Joachim Maier

Advanced Functional Materials 2014 Volume 24( Issue 3) pp:312-318

Publication Date(Web):

DOI:10.1002/adfm.201301792

The LiFePO₄/FePO₄ phase transition process is remarkable in terms of its excellent reversibility, making this redox system extremely promising for high rate lithium storage. The recent observation of ordering effects (Li_0.5FePO₄) during the phase transition challenges the traditional two phase models. In this work, the phenomenon of staging for LiFePO₄ for different sizes (70 nm and 50 nm) by high resolution aberration corrected annular bright electron microscopy is detected, investigated, and discussed along with previous results on larger crystals. In the small crystals, staging is found throughout with a decrease of order from center to the surface. For the larger crystal, a staging phase occurs constituting the interfacial zone (width around 15 nm) between LiFePO₄ and FePO₄. A comparison is made to recent experiments on even larger crystals showing such an interphase of smaller extent (around 2 nm). Thus it appears that these zones narrow with increasing size. These findings are discussed in the light of phase transition thermodynamics and kinetics. In particular, the possibility is discussed that the staging interphase may constitute a low energy solution to the LiFePO₄/FePO₄ contact.

A highly reversible, low-strain Mg-ion insertion anode material for rechargeable Mg-ion batteries

Co-reporter:Na Wu, Ying-Chun Lyu, Rui-Juan Xiao, Xiqian Yu, Ya-Xia Yin, Xiao-Qing Yang, Hong Li, Lin Gu and Yu-Guo Guo

NPG Asia Materials 2014 6(8) pp:e120

Publication Date(Web):2014-08-01

DOI:10.1038/am.2014.61

Rechargeable magnesium (Mg) batteries have been attracting increasing attention recently because of the abundance of the raw material, their relatively low price and their good safety characteristics. However, rechargeable Mg batteries are still in their infancy. Therefore, alternate Mg-ion insertion anode materials are highly desirable to ultimately mass-produce rechargeable Mg batteries. In this study, we introduce the spinel Li4Ti5O12 as an Mg-ion insertion-type anode material with a high reversible capacity of 175 mA h g−1. This material possesses a low-strain characteristic, resulting in an excellent long-term cycle life. The proposed Mg-storage mechanism, including phase separation and transition reaction, is evaluated using advanced atomic scale scanning transmission electron microscopy techniques. This unusual Mg storage mechanism has rarely been reported for ion insertion-type electrode materials for rechargeable batteries. Our findings offer more options for the development of Mg-ion insertion materials for long-life rechargeable Mg batteries.

Identifying Li+ ion transport properties of aluminum doped lithium titanium phosphate solid electrolyte at wide temperature range

Co-reporter:Shaofei Wang, Liubin Ben, Hong Li, Liquan Chen

Solid State Ionics 2014 Volume 268(Part A) pp:110-116

Publication Date(Web):15 December 2014

DOI:10.1016/j.ssi.2014.10.004

•Ac impedance spectroscopy of Li1 + xAlxTi2 -x(PO4)3 (x = 0 ~ 0.4) has been investigated at 123 K-333 K.•Undoped LiTi2(PO4)3 shows two bulk and one grain boundary region in impedance spectrum.•Relative density of ceramic has a significant impact on the conductivities of both bulk and grain boundary.A series of Li1 + xAlxTi2 − x(PO4)3 samples (x = 0–0.4) were prepared by solid state reaction and were characterized. Lattice parameters a and c decrease continuously with increase of Al content. The relative density of the Al-doped samples is about 97%, which is much higher than 75% of the undoped LiTi2(PO4)3 sample. Detailed ac impedance measurements from − 150 °C to 60 °C reveal clearly that three electrical response regions with different relaxation time constants coexist in the undoped LiTi2(PO4)3 sample but only two in all Al-doped samples. The bulk ionic conductivities for the Al-doped samples show no significant variation from x = 0.1 to x = 0.4. Their ionic conductivities are slightly higher than those of the undoped sample. However, this increase is not caused by increasing bulk ionic conductivity through introducing more lithium ions via doping, but it is mainly attributed to a densification effect.

Two-Phase Electrochemical Lithiation in Amorphous Silicon

Co-reporter:Jiang Wei Wang, Yu He, Feifei Fan, Xiao Hua Liu, Shuman Xia, Yang Liu, C. Thomas Harris, Hong Li, Jian Yu Huang, Scott X. Mao, and Ting Zhu

Nano Letters 2013 Volume 13(Issue 2) pp:709-715

Publication Date(Web):January 16, 2013

DOI:10.1021/nl304379k

Lithium-ion batteries have revolutionized portable electronics and will be a key to electrifying transport vehicles and delivering renewable electricity. Amorphous silicon (a-Si) is being intensively studied as a high-capacity anode material for next-generation lithium-ion batteries. Its lithiation has been widely thought to occur through a single-phase mechanism with gentle Li profiles, thus offering a significant potential for mitigating pulverization and capacity fade. Here, we discover a surprising two-phase process of electrochemical lithiation in a-Si by using in situ transmission electron microscopy. The lithiation occurs by the movement of a sharp phase boundary between the a-Si reactant and an amorphous LixSi (a-LixSi, x ∼ 2.5) product. Such a striking amorphous–amorphous interface exists until the remaining a-Si is consumed. Then a second step of lithiation sets in without a visible interface, resulting in the final product of a-LixSi (x ∼ 3.75). We show that the two-phase lithiation can be the fundamental mechanism underpinning the anomalous morphological change of microfabricated a-Si electrodes, i.e., from a disk shape to a dome shape. Our results represent a significant step toward the understanding of the electrochemically driven reaction and degradation in amorphous materials, which is critical to the development of microstructurally stable electrodes for high-performance lithium-ion batteries.

Molten salt electrolyte based on alkali bis(fluorosulfonyl)imides for lithium batteries

Co-reporter:Yali Liu, Sisi Zhou, Hongbo Han, Hong Li, Jin Nie, Zhibin Zhou, Liquan Chen, Xuejie Huang

Electrochimica Acta 2013 Volume 105() pp:524-529

Publication Date(Web):30 August 2013

DOI:10.1016/j.electacta.2013.05.044

•A LiFSI and KFSI eutectic molten salt electrolyte is prepared.•Binary phase diagram and transport properties are measured.•It shows wide electrochemical window and can passivate Al film.•It is compatible with cathode but incompatible with anode.•An irreversible reduction reaction occurs at 1.8 V vs. Li+/Li.Molten salts have attracted wide attention as electrolyte for lithium battery due to their nonvolatile and nonflammable features. In this work, the phase diagram of high pure lithium bis(fluorosulfonyl)imide (LiFSI) and KFSI binary system has been measured. This system shows a high transfer number of lithium ion at 85 °C and its conductivity reaches to 10−3–10−2 S cm−1 from 40 °C to 150 °C. The electrochemical windows of this system have been measured using Pt, Al and Cu as working electrode, respectively. The reversibility of lithium deposition in eutectic mixture (LiFSI:KFSI = 0.4:0.6 by mole) were investigated on LiCoO2, artificial graphite and LiFePO4, respectively, by cyclic voltammetry using three-electrodes systems. It is found that the half cell with this eutectic system as electrolyte can charge and discharge reversibly for LiFePO4 cathode but fails for MCMB and Li4Ti5O12 anodes. This problem would be solved partially by forming a passivating layer in advance or coating a protection layer on anode.

Temperature-dependent lithium storage behavior in tetragonal boron (B50) thin film anode for Li-ion batteries

Co-reporter:Xingle Ding, Xia Lu, Zhengwen Fu, Hong Li

Electrochimica Acta 2013 Volume 87() pp:230-235

Publication Date(Web):1 January 2013

DOI:10.1016/j.electacta.2012.09.017

Boron (B) has a high theoretical lithium storage capacity of 3046 mAh g−1 for forming Li5B4 phase. Li–B alloy has been used in high temperature thermal lithium batteries. In this work, a new tetragonal boron (B50) thin film with a thickness of 80 nm has been deposited on a vanadium coated glass substrate by a pulse laser deposition (PLD) method. It is found that this electrode film shows only a lithium storage capacity of 43 mAh g−1 in a nonaqueous electrolyte at room temperature. According to a first-principles calculation, the B50 is a metallic conductor. Therefore, the very poor activity could be related to poor lithium ion diffusion property since the diffusion barrier in this tetragonal B50 lattice is calculated as 2.59 eV. This consists well with the fact that the lithium storage capacity in the B50 thin film is improved significantly to 268 mAh g−1 at 85 °C.Highlights► Polycrystalline B50 thin film is prepared by PLD method. ► Li-storage in the B50 thin film is observed at room temperature and 80 °C. ► Structure of the B50 thin film before and after lithiation are observed by TEM and SAED. ► Dynamic parameters and electronic structure of the B50 are calculated. ► Diffusion barrier of lithium in the B50 lattice is calculated.

Electrochemical decomposition of Li2CO3 in NiO–Li2CO3 nanocomposite thin film and powder electrodes

Co-reporter:Rui Wang, Xiqian Yu, Jianming Bai, Hong Li, Xuejie Huang, Liquan Chen, Xiaoqing Yang

Journal of Power Sources 2012 Volume 218() pp:113-118

Publication Date(Web):15 November 2012

DOI:10.1016/j.jpowsour.2012.06.082

Two types of NiO–Li2CO3 nanocomposite electrodes have been prepared for the electrochemical decomposition studies. The thin film electrode with a thickness of 225 nm and grain size around 5–8 nm is prepared by a pulsed laser deposition method. The powder sample is prepared by a solution evaporation and calcination method with primary particle size in the range of 20–50 nm. Using ex situ TEM, Raman and FTIR spectroscopy and synchrotron based in situ XRD, the electrochemical decomposition of Li2CO3 phase in both types of the NiO–Li2CO3 nanocomposite electrodes after charging up to about 4.1 V vs Li+/Li at room temperature is clearly confirmed, but not in the electrode containing only Li2CO3. The NiO phase does not change significantly after charging process and may act as catalyst for the Li2CO3 decomposition. The potential of using NiO–Li2CO3 nanocomposite material as additional lithium source in cathode additive in lithium ion batteries has been demonstrated, which could compensate the initial irreversible capacity loss at the anode side.Highlights► NiO–Li2CO3 composite thin film and powder electrodes are prepared. ► Li2CO3 phase is decomposable after being charging to 4.1 V. ► NiO acts as a catalyst to decompose Li2CO3.

Direct Observation of Lithium Staging in Partially Delithiated LiFePO4 at Atomic Resolution

Co-reporter:Lin Gu, Changbao Zhu, Hong Li, Yan Yu, Chilin Li, Susumu Tsukimoto, Joachim Maier, and Yuichi Ikuhara

Journal of the American Chemical Society 2011 Volume 133(Issue 13) pp:4661-4663

Publication Date(Web):March 10, 2011

DOI:10.1021/ja109412x

Lithium ions in LiFePO4 were observed directly at atomic resolution by an aberration-corrected annular-bright-field scanning transmission electron microscopy technique. In addition, it was found in partially delithiated LiFePO4 that the remaining lithium ions preferably occupy every second layer, along the b axis, analogously to the staging phenomenon observed in some layered intercalation compounds. This new finding challenges previously proposed LiFePO4/FePO4 two-phase separation mechanisms.