Effect of Zn2+ and F- Co-Modification on the Structure and Electrochemical Performance of Li4Ti5O12 Anode Material

Aijia Wei,Wen Li,Lihui Zhang,Xiaohui Li,Xue Bai,Zhenfa Liu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.5

Zn2+ and F- ions are successfully used to modify pure Li4Ti5O12 via a co-precipitation method followed by calcination at 400℃ for 5 h in an Ar atmosphere in order to further investigate the reaction mechanism of the fluoride modification process. Zn2+ and F- co-modified Li4Ti5O12 samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. After the modification process, no ZnF2 coating layer is formed on the surface of Li4Ti5O12, instead, F- ions react with Li4Ti5O12 to generate a new phase, composed of a small amount of anatase TiO2, rutile TiO2, LiF, and Zn2+ ions are suspected to form a ZnO coating layer on Li4Ti5O12 particles. The electrolyte reduction decomposition is suppressed in Zn2+ and F- co-modified Li4Ti5O12 due to the ZnO coating layer. 1 wt.% Zn2+ and F- co-modified Li4Ti5O12 exhibits the best rate capability, which leads to a charge capacity of 236.7, 227.8, 222.1, 202.7, 188.9 and 150.7 mAh g -1 at 0.2C, 0.5C, 1C, 3C, 5C and 10C, respectively, between 0 V and 3 V. Furthermore, 1 wt.% Zn2+ and F- comodified Li4Ti5O12 exhibits 96.0% charge capacity retention at 3C rate after 200 cycles, which is significantly higher than that of pure Li4Ti5O12 (78.4%).

First-principles calculations of the effect of Ge content on the electronic, mechanical and acoustic properties of Li17Si4-xGex

Xiaohong Li,Hong-Ling Cui,Rui-Zhou Zhang 한국물리학회 2019 Current Applied Physics Vol.19 No.6

The electronic, mechanical and acoustic properties of Li17Si4-xGex (x=0, 2.3, 3.08, 3.53, and 4) have been investigated by using first-principles calculations based on the density functional theory (DFT). The research shows that the bulk modulus B, Young's modulus E, shear modulus G, and hardness Hv gradually decrease with the increasing Ge content. Li17Si4-xGex have the brittle nature from the analysis of B/G ratio and Cauchy pressure. The maximum Young's moduli are all along [1 1 0] plane, and the sequence of degree of anisotropic property is Li17Ge4 > Li17Si0.48Ge3.52 > Li17Si0.92Ge3.08 > Li17Si1.7Ge2.3 > Li17Si4. The analysis of acoustic velocity shows that all the sound velocities decrease with the increasing Ge content for Li17Si4-xGex (x=0, 2.3, 3.08, 3.53, and 4), and the longitudinal wave along [111] direction is fastest for the studied compounds. Debye temperature ΘD, vt and vl decrease with the increasing Ge content. The minimum thermal conductivity decreases with the increasing Ge content, and Li17Si4-xGex have low thermal conductivities and are not potential thermal conductors. The analysis of electronic properties indicates that Li17Si4-xGex have the metal nature and anisotropic electrical conductivity. The electric conduction is improved with the increasing Ge content.

Designed seamless outer surface: Application for high voltage LiNi_0.5Mn_1.5O₄ cathode with excellent cycling stability

Zhang, Kan,Li, Ping,Ma, Ming,Park, Jong Hyeok Elsevier 2016 Journal of Power Sources Vol.336 No.-

<P><B>Abstract</B></P> <P>Suppressing side reactions at the cathode-electrolyte interface (CEI) is critical for alleviating capacity fading of the high-voltage (>5 V) spinel cathode material LiNi<SUB>0.5</SUB>Mn<SUB>1.5</SUB>O<SUB>4</SUB> (LNMO). The primary bottleneck in conventional nanoengineering of LNMO involves an antagonistic relationship between the positive effects of the nanometer particle size and negative effects stemming from the larger CEI area. Inspired by Buckminster Fuller's geodesic domes, we have designed a seamless LNMO hollow sphere (S-LNMO) that comprises average 120 nm-sized triangles and truncated triangle subunits by means of grain growth orientation. The “tensegrity” structure has efficiently hindered the interfacial side reaction, which occurs only within a depth of 5 nm from the surface, thereby improving its electrochemical stability. The embedded layered Li<SUB>2</SUB>TiO<SUB>3</SUB> (LTO) in bulk S-LNMO (LTO:S-LNMO) region further improved the high-rate performance, demonstrating an ∼110 mAh/g capacity with 80.9% retention after 400 cycles at 5 C and remaining stable after 900 cycles at 5 C even after being stored at 50 °C for one week.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Seamless disordered Fd3m-phase LiNi<SUB>0.5</SUB>Mn<SUB>1.5</SUB>O<SUB>4</SUB> hollow spheres are subtly designed. </LI> <LI> The seamless architecture minimized the interfacial side reaction. </LI> <LI> Nanometer depth analysis showed an electrolyte permeation distance of less than 5 nm. </LI> <LI> A layered Li<SUB>2</SUB>TiO<SUB>3</SUB> embedded in LiNi<SUB>0.5</SUB>Mn<SUB>1.5</SUB>O<SUB>4</SUB> enables high-rate performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Effect of Li Content on the Surface Film Formed on the Binary Mg–Li Alloys in NaCl Solution

Chuanqiang Li,Dahui Liang,Yejia Lin,Yong Dong,Binqing Shi,Changjian Yan,Zhengrong Zhang 대한금속·재료학회 2024 METALS AND MATERIALS International Vol.30 No.1

The surface film formed on the Mg–Li alloys with different Li content in 0.1 M NaCl solution were investigated via electrochemicaltesting, morphologies observation and chemical composition analysis in this work. The results revealed that thesurface film of Mg–14Li alloy (L14: body centred cubic (BCC)) possessed higher electrical resistivity and remained a highertolerating over-potential (0.1 V vs. open circuit potential) than those of Mg–4Li (L4: hexagonal closed-packed (HCP)) andMg–7.5Li (L7: HCP+BCC), resulting in a better corrosion performance. After 24 h immersion in NaCl solution, the wholesurface film of L14 remained undamaged and displayed weave-like and dense characteristic, while both L4 and L7 present aseverely damaged film. The cross-sectional details illustrated typical two layers of surface film formed on L14 with the outerlayer of ~ 1.5 μm and inner layer of ~ 2.5 μm in thickness, whilst only one layer of film with less than 2.5 μm in thicknesswas observed on L4 and L7. At last, combining analysis of X-ray diffraction, energy dispersive X-ray spectrometry, X-rayphotoelectron spectroscopy and transmission electron microscope confirmed the composition of outer layer of surface filmon the L14 contains much more Mg(OH)2 and Li-containing compounds, and the porous Mg(OH)2 film can be sealed by theLi-containing compounds, which is very different the single Mg(OH)2 film on the traditional magnesium and L4/L7 alloys. As a result, the best protective function of the surface film on the L14 alloy contribute to its high corrosion resistance.

In-situ PECVD-enabled graphene-V₂O₃ hybrid host for lithium–sulfur batteries

Song, Yingze,Zhao, Wen,Wei, Nan,Zhang, Li,Ding, Feng,Liu, Zhongfan,Sun, Jingyu Elsevier 2018 Nano energy Vol.53 No.-

<P><B>Abstract</B></P> <P>Lithium–sulfur (Li–S) batteries have been regarded as promising candidates for current energy-storage technologies due to their remarkable advantages in energy density and theoretical capacity. However, one of the daunting challenges remained for advanced Li–S systems thus far deals with the synchronous suppression of polysulfide (LiPS) shuttle and acceleration of redox kinetics. Herein, a cooperative interface bridging adsorptive V<SUB>2</SUB>O<SUB>3</SUB> and conductive graphene is constructed <I>in-situ</I> by virtue of direct plasma-enhanced chemical vapor deposition (PECVD), resulting in the design of a novel V<SUB>2</SUB>O<SUB>3</SUB>-graphene hybrid host to synergize the LiPS entrapment and conversion. The redox kinetics and electrochemical performances of thus-derived cathodes were accordingly enhanced owing to the smooth adsorption-diffusion-conversion of LiPSs even at a sulfur mass loading of 3.7 mg cm<SUP>–2</SUP>. Such interfacial engineering offers us a valuable opportunity to gain insight into the comprehensive regulation of LiPS anchoring ability, electrical conductivity and ion diffusive capability in hybrid hosts on suppressing the LiPS shuttle and propelling the redox kinetics. Our devised PECVD route might pave a new route toward the facial and economic design of hetero-phased multi-functional hosts for high-performance Li–S systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Graphene-V<SUB>2</SUB>O<SUB>3</SUB> hybrid host was designed <I>in-situ</I> based on PECVD route. </LI> <LI> Thus-derived cathode showed a low capacity decay of merely 0.046% per cycle at 2 C after 1000 cycles. </LI> <LI> Cathodes with a relatively high sulfur mass loading (3.7 mg cm<SUP>–2</SUP>) were fabricated. </LI> <LI> The smooth adsorption-diffusion-conversion of polysulfides was thoroughly probed <I>via</I> experimental studies and DFT simulations. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Aqueous Processing and Effects of V2O5 on Microwave Dielectric Properties of Multilayer Li1.075Nb0.625Ti0.45O3 Ceramics

Shaochun Li,Yongjuan Geng,Tiejun Zhao,Zuquan Jin,Peng Zhang 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.1

In the present work, we report the development of an aqueous tape casting method and a low temperature co-firing process for fabrication of multilayer Li1.075Nb0.625Ti0.45O3 microwave dielectric ceramics. A co-binder, consisting of polyvinyl acetate latex (PVAc) and polyvinyl alcohol (PVA), was used to prepare aqueous Li1.075Nb0.625Ti0.45O3 tapes. PVA addition increased the tape flexibility and adhesiveness but resulted in decreased tensile strength. Rheological tests indicated that the aqueous ceramic slurry exhibited a typical shear thinning behavior without thixotropy, suitable for tape casting. Scanning electron microscopy (SEM) studies revealed that the green tapes have a defect-free surface and that the multilayer ceramics sintered at 900°C have a fine plate like, grainy microstructure of uniform size. At lower temperatures, increased densification rates were achieved by addition of V2O5 to Li1.075Nb0.625Ti0.45O3 ceramics. The saturated bulk densities and dielectric constants (εr) of Li1.075Nb0.625Ti0.45O3 multilayer ceramics affected by lower sintering temperatures with an increase in V2O5 doping, and then an improvement in the quality factor (Q × f value) of the samples was achieved at the lower sintering temperatures. As a result, the εr of 64.9 and the Q × f value of 8800 GHz were obtained in the sample with an addition of 3 wt. % V2O5, sintered at a temperature of 900°C. No reaction was observed between the ceramic and silver layers when sliver inner-electrode, was sintered with ceramic tapes at 900°C.

Review on State of Charge Estimation Methods for Li-Ion Batteries

Xiaoqiang Zhang,Wei-ping Zhang,Hongyu Li,Mao Zhang 한국전기전자재료학회 2017 Transactions on Electrical and Electronic Material Vol.18 No.3

The state of charge (SOC) is an important parameter in a battery-management system (BMS), and is very significantfor accurately estimating the SOC of a battery. Li-ion batteries boast of excellent performance, and can only remainat their best working state by means of accurate SOC estimation that gives full play to their performances and raisestheir economic benefits. This paper summarizes some measures taken in SOC estimation, including the dischargeexperiment method, the ampere-hour integral method, the open circuit voltage method, the Kalman filter method,the neural network method, and electrochemical impedance spectroscopy (EIS. The principles of the various SOCestimation methods are introduced, and their advantages and disadvantages, as well as the working conditionsadopted during these methods, are discussed and analyzed.

Review on State of Charge Estimation Methods for Li-Ion Batteries

Zhang, Xiaoqiang,Zhang, Weiping,Li, Hongyu,Zhang, Mao The Korean Institute of Electrical and Electronic 2017 Transactions on Electrical and Electronic Material Vol.18 No.3

The state of charge (SOC) is an important parameter in a battery-management system (BMS), and is very significant for accurately estimating the SOC of a battery. Li-ion batteries boast of excellent performance, and can only remain at their best working state by means of accurate SOC estimation that gives full play to their performances and raises their economic benefits. This paper summarizes some measures taken in SOC estimation, including the discharge experiment method, the ampere-hour integral method, the open circuit voltage method, the Kalman filter method, the neural network method, and electrochemical impedance spectroscopy (EIS. The principles of the various SOC estimation methods are introduced, and their advantages and disadvantages, as well as the working conditions adopted during these methods, are discussed and analyzed.

Mechanism and process for the extraction of lithium from the high magnesium brine with N,N-bis(2-ethylhexyl)-2-methoxyacetamide in kerosene and FeCl3

Lianmin Ji,Licheng Zhang,Dong Shi,Xiaowu Peng,Jinfeng Li,Yuze zhang,Taoshan Xu,Lijuan Liao 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.113 No.-

The degradation of TBP has become a stumbling block to the industrial continuous production of lithiumchloride extraction from brines with high Mg/Li ratio by solvent extraction. To develop a more stable andmore efficient extraction system, a novel amide system, containing newly synthesized extractant N,N-bis(2-ethylhexyl)-2-methoxyacetamide (NBEHMOA), FeCl3 6H2O and sulfonated kerosene, was proposed inthis work. Compared with TBP and N523, NBEHMOA extracted Li+ and H+ in the sequence of TBP ˃NBEHMOA ˃ N523 and N523 ˃ TBP ˃ NBEHMOA respectively. The solution containing 5.5 mol/L LiCland 0.5 mol/L HCl was used as the eluent in the scrubbing process. A Li+ extraction efficiency of 96.7%and 22.31 g/L Li+ in the stripping solution were achieved by the whole process with counter-currenttwelve stages. The extraction mechanism investigated via FT-IR spectroscopy illustrated that the metalions Fe3+ and Li+ were mainly coordinated by the carbonyl C = O in NBEHMOA. This novel amide systemcan successfully achieve the cascade extraction effect for lithium, Li/Mg separation and avoid the generationof phase interface objects through counter-current extraction of lithium from brine at a lower acidity. This work provided a novel extraction system to recover lithium from the higher magnesium/lithiumratio brines.

Structure and Performances of xLiFePO4/C·(1 − x)Li3V2(PO4)3/C Cathode for Lithium-Ion Batteries by Using Poly(vinyl alcohol) as Carbon Source

Chang-ling Fan,Wei-hua Zhang,Tao-tao Zeng,Ling-fang Li,Xiang Zhang,Shao-chang Han 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.11

Poly(vinyl alcohol), whose pyrolysis carbon possesses high conductivity of 8.88 × 10−1 S/cm, was used to synthesize xLiFePO4/C·(1 − x)Li3V2(PO4)3/C cathode. It was characterized by X-ray diffraction, scanning electron microscopy, conductivity, cyclic voltammetry, and galvanostatic charge and discharge experiments. Results show that LiFePO4/C and Li3V2(PO4)3/C coexists in the cathode. The particles sizes of 0.75LiFePO4/C·0.25Li3V2(PO4)3/C (x = 0.75) are much smaller than 100 nm due to the role of poly(vinyl alcohol). Its conductivity is 8.79 × 10−2 S/cm. The oxidative and reductive peaks in cyclic voltammetry are sharp and symmetrical. Their low potential gaps indicate that the extractions and insertions of lithium ion possess excellent reversibility. Its discharge capacities at 1 and 5 C are 141.1 and 100.1 mAh/g. The more Li3V2(PO4)3/C in cathode results in the deterioration of electrochemical performances due to its low theoretical capacity. It is concluded that poly(vinyl alcohol) is an effective carbon source in the preparation of xLiFePO4/C·(1 − x)Li3V2(PO4)3/C composite cathode with excellent performances.