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CrO-modified LiNiCoMnO composites are prosperously synthesized through a high-temperature solid-state method. From scanning electron microscopy and transmission electron microscopy analyses, it can be observed that the structures of CrO-modified LiNiCoMnO materials were converted to polycrystalline. An appropriate amount of CrO could reduce the electrochemical polarization of electrode and enhance the electrochemical reaction kinetics of Li insertion/deinsertion. Consequently, the discharge capacity of 2 wt% CrO-modified LiNiCoMnO material is 186.7, 185.5, 174.1, and 171.7 mAh/g, at 0.1, 0.2, 0.5, and 1 C rates, in the voltage range of 2.6-4.6 V, respectively, which are higher than those of other samples. In particular, the rate capacity of 2 wt% CrO-modified LiNiCoMnO material remains 90% even after 63 cycles. Cyclic voltammetry measurements indicate that the materials have favorable structural stability and cycle performance. The enhancement of rate capacity of LiNiCoMnO material was attributed to CrO modification, which increased the conductivity of the material. [ABSTRACT FROM AUTHOR]

• The Li+ and Br− ions are firstly co-doped in LiNi 0.5 Mn 1.5 O 4 via a solid-state method. • Significant increase of Li+ diffusivity and decrease of Mn3+ion contents can be observed in the Li+ and Br− co-doped LiNi 0.5 Mn 1.5 O 4. • Rate performance and cycling capability have been improved by the Li+ and Br− co-doping. • 4. The surface resistance, especially the charge transfer resistance, can effectively reduce by the Li+ and Br− co-doping in spinel LiNi 0.5 Mn 1.5 O 4. Few studies have reported the effects of cation and anion co-doping in LNMO. Pristine LiNi 0.5 Mn 1.5 O 4 and Li 1+ x Ni 0.5 Mn 1.5 O 4- x Br x (0 ≤ x ≤ 0.04, mol%) were synthesized using a facile solid-state ball-milling process. The structural characterization results suggested that Li+ and Br− co-doping effectively decreased the Mn3+content and Li x Ni 1- x O impurity phases, and enhanced chemical and structural stability by forming stronger Mn Br bonds rather than Mn O bonds. Electrochemical performance tests indicated that the Li+ and Br− co-doped Li 1.02 Ni 0.5 Mn 1.5 O 3.98 Br 0.02 sample (LNMO-Br0.02) possessed an excellent rate capability. The corresponding discharge capacity at 0.2 C, 0.5 C, 1 C, 2 C, 3 C, 5 C, 7 C, and 10 C were around 134.6, 132.8, 132.0, 127.4, 122.1, 112.9, 102.9, and 82.5 mAh/g, respectively. Under similar conditions, pristine LiNi 0.5 Mn 1.5 O 4 yielded only 125.7, 124.8, 121.8, 117.0, 111.1, 95.2, 73.0, and 27.6 mAh/g. In addition, LNMO-Br0.02 delivered favorable cycling performance at room temperature (25 °C), and about 95.3% of the initial capacity (120.5 mAh/g) could be obtained after 270 cycles at 3 C. Post-cycling Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses revealed that LNMO-Br0.02 possessed the thinner cathode-electrolyte interphase (CEI) film than the other materials. (a) Schematic illustration of Li 1+x Ni 0.5 Mn 1.5 O 4-x Br x structure; (b) Rate capacities of all the samples at different C-rates. [Display omitted] [ABSTRACT FROM AUTHOR]

K+/Cl− and K+/F− co-doped LiNi0.5Mn1.5O4 (LNMO) materials were successfully synthesized via a solid-state method. Structural characterization revealed that both K+/Cl− and K+/F− co-doping reduced the LixNi1−xO impurities and enlarged the lattice parameters compared to those of pure LNMO. Besides this, the K+/F− co-doping decreased the Mn3+ ion content, which could inhibit the Jahn–Teller distortion and was beneficial to the cycling performance. Furthermore, both the K+/Cl− and the K+/F− co-doping reduced the particle size and made the particles more uniform. The K+/Cl− co-doped particles possessed a similar octahedral structure to that of pure LNMO. In contrast, as the K+/F− co-doping amount increased, the crystal structure became a truncated octahedral shape. The Li+ diffusion coefficient calculated from the CV tests showed that both K+/Cl− and K+/F− co-doping facilitated Li+ diffusion in the LNMO. The impedance tests showed that the charge transfer resistances were reduced by the co-doping. These results indicated that both the K+/Cl− and the K+/F− co-doping stabilized the crystal structures, facilitated Li+ diffusion, modified the particle morphologies, and increased the electrochemical kinetics. Benefiting from the unique advantages of the co-doping, the K+/Cl− and K+/F− co-doped samples exhibited improved rate and cycling performances. The K+/Cl− co-doped Li0.97K0.03Ni0.5Mn1.5O3.97Cl0.03 (LNMO-KCl0.03) exhibited the best rate capability with discharge capacities of 116.1, 109.3, and 93.9 mAh g−1 at high C-rates of 5C, 7C, and 10C, respectively. Moreover, the K+/F− co-doped Li0.98K0.02Ni0.5Mn1.5O3.98F0.02 (LNMO-KF0.02) delivered excellent cycling stability, maintaining 85.8% of its initial discharge capacity after circulation for 500 cycles at 5C. Therefore, the K+/Cl− or K+/F− co-doping strategy proposed herein will play a significant role in the further construction of other high-voltage cathodes for high-energy LIBs. [ABSTRACT FROM AUTHOR]

This work reports improved cycle performance and rate properties of Ni-rich layered oxide cathode material. Trace amounts of Ce were used to modify the crystal structure and surface of the Ni-rich Li 1.02 Ni 0.6 Co 0.2 Mn 0.2 O 2. The structure and electrochemical performances of the materials were characterized using XRD, SEM, TEM, XPS, ICP, charge-discharge testing, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results showed that the peak has a slight shift after Ce modification of the material, showing that some Ce entered the crystal lattice. TEM showed that the remainder of the Ce forms a 8-nm thick coating layer on the surface of the Li 1.02 Ni 0.6 Co 0.2 Mn 0.2 O 2 material. As a result, the Ce-modified sample exhibited superior electrochemical performance. The initial discharge capacity of the Ce modified sample was 161 mAh/g at 1C, the discharge capacity was still kept 84.6% after 200 cycles. • Ce-modified sample didn't change the structure of NCM622. • Ce-modified could optimize the crystal microstructure of Li 1.02 Ni 0.6 Co 0.2 Mn 0.2 O 2. • Initial capacities of Ce-modified Li 1.02 Ni 0.6 Co 0.2 Mn 0.2 O 2 was 161 mAh/g at 1C. • Ce-modified Li 1.02 Ni 0.6 Co 0.2 Mn 0.2 O 2 sample keeps 85% capacity after 200 cycles. • Ce plays a role in both doping and coating role to Li 1.02 Ni 0.6 Co 0.2 Mn 0.2 O 2. [ABSTRACT FROM AUTHOR]

In order to determine the reaction mechanism of the fluoride modification process and its influence on the electrochemical properties of Li 4 Ti 5 O 12 anode material, the “ZrF 4 -modified” Li 4 Ti 5 O 12 was prepared via a co-precipitation method. Structural characterization results shows that both Zr 4+ and F − ions were not incorporated into the lattice structure of Li 4 Ti 5 O 12 after the modification process. Instead, F − reacts with Li 4 Ti 5 O 12 chemically to generate new impurity phase such as anatase TiO 2 and LiF, while Zr 4+ forms amorphous ZrO 2 nano-particles over the Li 4 Ti 5 O 12 particles. There was no dense coating layer formed on the surface of the Li 4 Ti 5 O 12 particles. These results indicate the reaction mechanism of the ZrF 4 -modification process was different from that previously reported (such as “AlF 3 , MgF 2 , ZnF 2 , SrF 2 and CaF 2 -modification”). The rate capability and cycling stability of Li 4 Ti 5 O 12 can be enhanced due to the “ZrF 4 -modification” process. Specifically, the 2 wt% “ZrF 4 -modified” Li 4 Ti 5 O 12 shows the best electrochemical performance. [ABSTRACT FROM AUTHOR]

A Li 4 Ti 5 O 12 /N-doped graphene composite has been successfully prepared by a solid-state method. For comparison, pure Li 4 Ti 5 O 12 and Li 4 Ti 5 O 12 /graphene composite were also synthesized. The results reveal that nitrogen-doped graphene sheets can provide additional free electrons and enhance the electronic conductivity between adjacent Li 4 Ti 5 O 12 particles. Comparing the electrochemical performances of the three materials, the Li 4 Ti 5 O 12 /N-doped graphene composite exhibits excellent performance with specific capacities of 164, 161.5, 157.9, 144.6, 127.8, 104.4, and 80.5 mAh g − 1 at rates of 0.2, 0.5, 1, 3, 5, 10 and 20 C (1 C = 160 mAh g − 1 ), respectively. Moreover, Li 4 Ti 5 O 12 /N-doped graphene composite showed a charge capacity retention of 92% after 200 cycles at a rate of 5 C, which is higher than that of Li 4 Ti 5 O 12 /graphene composite (89.0%) and pure Li 4 Ti 5 O 12 (87.0%). Electrochemical impedance (EIS) and cyclic voltammetry (CV) were used to characterize the electrochemical kinetics. The charge transfer resistance of the Li 4 Ti 5 O 12 /N-doped graphene composite (70.9 Ω) is lower than that of Li 4 Ti 5 O 12 /graphene composite (94.4 Ω) and pure Li 4 Ti 5 O 12 (120.7 Ω). The Li + diffusion coefficient of the Li 4 Ti 5 O 12 /N-doped graphene composite is 5.76 × 10 − 10 cm 2 s − 1 , which is larger than that of Li 4 Ti 5 O 12 /graphene composite (3.61 × 10 − 10 cm 2 s − 1 ) and pure Li 4 Ti 5 O 12 (2.31 × 10 − 10 cm 2 s − 1 ). The improved electrochemical performance of the Li 4 Ti 5 O 12 /N-doped graphene composite may be ascribed to that the N-doped graphene distributed around Li 4 Ti 5 O 12 particles, providing high electronic conductivity and fast lithium ion diffusion. [ABSTRACT FROM AUTHOR]

High-voltage (5-V) lithium–ion batteries (LIBs) have garnered substantial interest due to their superior energy density. Nevertheless, the unstable interphase of high-voltage LIBs can cause electrolyte decomposition, electrode collapse, transition metal dissolution, and lithium dendrite growth during cycling, which impedes their widespread commercial use. To mitigate these challenges, various alkali-metal phosphates were incorporated into a carbonate-based electrolyte as film-forming additives, aiming to improve the electrochemical performance of LiNi 0.5 Mn 1.5 O 4 (LNMO)-based LIBs. Following a detailed comparison of the electrochemical performances of various alkali-metal phosphates, KH 2 PO 4 and NaH 2 PO 4 were selected for an in-depth investigation in this research. The highly protective passivation film generated by KH 2 PO 4 and NaH 2 PO 4 on the electrode surface provided significant protection by effectively inhibiting continuous electrolyte decomposition. This finding was supported by density functional theory calculations and a variety of electrochemical and characterization tests. The H 2 PO 4 − primarily contributed to the formation of the cathode electrolyte interphase film on the cathode surface. KH 2 PO 4 (via the electrostatic shielding effect of K +ions) and NaH 2 PO 4 (through the co-precipitation of Na+ and Li+ ions) both effectively inhibited the growth of lithium dendrites on the lithium metal anode. Additionally, the KH 2 PO 4 and NaH 2 PO 4 additives regulated the amount of HF in the electrolyte through acid–base equilibrium reactions. The electrolytes containing additives significantly enhanced the electrochemical performances of Li||Li, LNMO/Li, LNMO/graphite, and LNMO/Li 4 Ti 5 O 12 cells. LNMO/Li half-cells with standard electrolyte (STD) supplemented with KH 2 PO 4 and NaH 2 PO 4 additives demonstrated capacity retentions of 92.9 % and 90.0 % after 500 cycles at 5 C, respectively, in contrast to only 79.4 % for the STD electrolyte alone. Furthermore, the LNMO/graphite full cell exhibited an increased capacity retention, reaching 81.1 % (STD+KH 2 PO 4) and 78.29 % (STD+NaH 2 PO 4), up from 70.8 % with the STD, after 100 cycles at 0.5 C. Given their ease of use, affordability, and widespread availability, KH 2 PO 4 and NaH 2 PO 4 additives show significant potential to enhance the electrochemical properties of high-voltage LIBs. [Display omitted] [ABSTRACT FROM AUTHOR]

The recent development of Li-ion batteries based on Ni-rich cathodes with high specific capacity has generated considerable interest. However, cathodes with a sufficiently high Ni concentration suffer from rapid capacity decay and poor thermal stability during charge/discharge cycling, which represents a substantial challenge toward commercialization. While the application of a coating layer has been demonstrated to be an effective means of solving this issue, this typically increases the complexity and expense of cathode material fabrication. The present work addresses this issue by applying a LaPO 4 /Li 3 PO 4 (LP) layer on the surface of LiNi 0.83 Co 0.11 Mn 0.06 O 2 cathode materials using a facile in situ coating method. This simple method functions concurrently with the high-temperature solid-state method employed for fabricating the cathode materials using Ni 0.83 Co 0.11 Mn 0.06 (OH) 2 as a precursor with added ammonium dihydrogen phosphate (NH 4 H 2 PO 4) and lanthanum nitrate (La(NO 3) 3). The modified cathode material reacts with residual Li, and forms a LP layer on the Ni-rich cathode surface, while a proportion of the La3+ diffuses into the layered LiNi 0.83 Co 0.11 Mn 0.06 O 2 structure during the modification process. Experimental investigation indicates that the LP layer not only eliminates the residual Li, but also deters the formation of microcracks, and thereby inhibits reactions with the electrolyte during charge/discharge cycling. The LP-modified LiNi 0.83 Co 0.11 Mn 0.06 O 2 sample is demonstrated to attain a capacity retention of 94% and 79.8% after 100 and 500 charge/discharge cycles conducted at 1C, respectively. [ABSTRACT FROM AUTHOR]

Tris (trimethylsilyl) phosphate (TMSP) and tris(2,2,2-trifluoroethyl) phosphate (TTFP) was added to carbonate solvent-based electrolytes as dual-additives to enhance the performance of LiNi 0·5 Mn 1·5 O 4 (LNMO). The X-ray photoelectron spectroscopy results revealed that both TMSP with high oxidation ability and TTFP with high oxidation resistance participated in the formation of cathode–electrolyte interphase (CEI) films. Electrochemical impedance spectroscopy confirmed that the constructed CEI films had excellent electronic insulation and ionic conductivity, reducing the interfacial impedance of the LNMO electrode, and improving the electrochemical performance of LNMO/Li half-cells and LNMO/Li 4 Ti 5 O 12 full-cells. As measured by the nuclear magnetic resonance, the incorporation of TMSP and TTFP significantly reduced the HF content in the electrolytes. Therefore, both LNMO/Li half-cells (500 cycles with 95.7% capacity retention) and LNMO/Li 4 Ti 5 O 12 full-cells (200 cycles with 79.9% capacity retention) displayed higher cycling stabilities at 5 C owing to the synergistic effect of TMSP and TTFP. In comparison, capacity retentions of ∼76.5% after 500 cycles and ∼37.2% after 200 cycles were respectively achieved for the LNMO/Li half-cells and LNMO/Li 4 Ti 5 O 12 full-cells with the standard electrolyte at 5 C. This study provides strong evidence that additive combinations can improve the electrochemical performance of high-energy and high-voltage cathode materials. • The combination of TMSP and TTFP was added to conventional electrolytes. • The cyclability of LNMO-based battery was enhanced by the use of dual-additives. • The action mechanism of the dual-additives was investigated. [ABSTRACT FROM AUTHOR]

LiNi 0.5 Mn 1.5 O 4 cathode materials with a range of boron doping contents were successfully synthesized via an in situ solid-state method. The structures and grain morphologies were examined to elucidate the effect of boron doping on the electrochemical performance of LiNi 0.5 Mn 1.5 O 4. Scanning electron microscopy images show that the particle sizes of boron-doped LiNi 0.5- x /2 B x Mn 1.5- x /2 O 4 samples increase compared with those of pure LiNi 0.5 Mn 1.5 O 4. Characterization results confirm that boron doping could create more Mn3+ ions and increase the Mn3+ ions contents in LiNi 0.5- x /2 B x Mn 1.5- x /2 O 4 samples with increasing boron doping content. A greater number of Mn3+ ions could enhance the cationic disorder degree, thereby resulting in high electronic conductivities of LiNi 0.5- x /2 B x Mn 1.5- x /2 O 4 samples. Charge-discharge tests reveal that improvements in the electrochemical performance are achieved in LiNi 0.5- x /2 B x Mn 1.5- x /2 O 4 samples compared with that of pure LiNi 0.5 Mn 1.5 O 4. The boron-doped LiNi 0.495 B 0.01 Mn 1.495 O 4 (denoted as LNMO-B0.01) cathode exhibits an excellent cycling stability with a capacity retention of 83.3% after 500 cycles at 3 C. Moreover, it also displays an optimal rate capability with discharge capacities of 136.1, 135.7, 130.3, 126.2, 123.1, 114.5, 104.5, and 82.9 mA h g−1 at 0.2, 0.5, 1, 2, 3, 5, 7, and 10 C, respectively. The highest Li+ diffusion coefficient of LNMO-B0.01 determined from cyclic voltammetry tests indicates that an appropriate amount of boron doping could accelerate the Li+ diffusion in LNMO-B0.01. The lowest charge-transfer resistance obtained from the impedance spectra suggests that boron doping could promote kinetic charge transfer. As a result, this modification strategy can be utilized to enhance the electrochemical performance of LiNi 0.5 Mn 1.5 O 4 material. [ABSTRACT FROM AUTHOR]

Abstract The high-voltage spinel LiNi 0.5 Mn 1.5 O 4 (LNMO) is a potential cathode material for lithium-ion batteries with outstanding energy density and power density. Here, we document a facile approach to prepare Al 2 O 3 -modified LNMO cathode materials. The Al 2 O 3 -modified LNMO materials were synthesized via a one-step solid-state reaction and then modified with Al 2 O 3 via a wet chemical technique. The impacts of Al 2 O 3 modification on the structure and electrochemical properties of LNMO materials were examined by X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, charge-discharge tests, cyclic voltammetry measurements, electrochemical impedance spectroscopy, and aging tests. Throughout the modification process, several Al3+ were noted to substitute for Ni2+, resulting in a decrease of Mn4+ to Mn3+; this increased the electronic conductivity and lowered the electrochemical polarization of the LNMO material. An amorphous Al 2 O 3 coating layer developed on the surface of the LNMO particles in the modification, and this could alleviate the strike of HF caused by electrolyte decomposition as well as the development of a solid electrolyte interphase. Thus, the 0.5 wt% Al 2 O 3 -modified LNMO material had decreased R sf and R ct and greater D Li values with a rate capability and cycling stability better than LNMO. The rate capability was 105.6 and 83.3 mAh g–1 at high C rates of 5 C and 7 C, as opposed to 83.3 and 54.9 mAh g–1, respectively; the room temperature (25 °C) capacity retention was 92.6% at 1 C after 200 cycles, as opposed to 87.0%. The high-temperature (55 °C) capacity retention was 90.9% at 1 C rate after 200 cycles as opposed to 86.5%. Thus, this is an easy and feasible method to improve the electrochemical performance of LNMO cathode materials for industrialization. [ABSTRACT FROM AUTHOR]

Abstract Li 4 Ti 5 O 12 /graphene composites with different graphene additives (0.47 wt%, 0.93 wt%, 1.99 wt%) were prepared by a facile one-step solid-state reaction with sand milling followed by sintering at 800 °C. The electrochemical performance of the Li 4 Ti 5 O 12 /graphene composites is influenced significantly by the graphene proportion. The Li 4 Ti 5 O 12 /graphene composite with 0.93 wt% graphene (denoted GLTO-2) exhibits an excellent rate performance with specific charge capacities of 175.2, 175.8, 171.9, 167.9, 166.4, 164.1, 161.4159.4 and 150.8 mAh g−1 at 0.2, 0.5, 1, 3, 5, 10, 15, 20 and 30 C (1 C = 160 mAh g−1), respectively. GLTO-2 also shows a remarkable long-term cycling stability with a charge-capacity retention of 80.2% after 2000 cycles at a rate of 5 C, which is higher than that of pure Li 4 Ti 5 O 12 (57.0%). The significant enhancement in electrochemical properties of GLTO-2 could be attributed to the smallest polarization and charge-transfer resistance (47.3 Ω), and the highest Li+ diffusion coefficient (1.04 × 10−9 cm2 s−1) demonstrated by the cyclic-voltammetry and electrochemical-impedance spectra tests. Our study provides a facile strategy for preparing Li 4 Ti 5 O 12 /graphene composites with an outstanding rate capability for high-power lithium-ion batteries, which is desirable for large-scale applications. Graphical abstract Li 4 Ti 5 O 12 /graphene composites with different graphene additives (0.47 wt%, 0.93 wt%, 1.99 wt%) were prepared by a facile one-step solid-state reaction with sand milling. The Li 4 Ti 5 O 12 /graphene composite with 0.93 wt% graphene (denoted GLTO-2) exhibits an excellent rate performance and also shows a remarkable long-term cycling stability at 5 C. The significant enhancement in electrochemical properties of GLTO-2 could be attributed to the smallest polarization and charge-transfer resistance (47.3 Ω), and the highest Li+ diffusion coefficient (1.04 × 10−9 cm2 s−1) demonstrated by the cyclic-voltammetry and electrochemical-impedance spectra tests. Unlabelled Image Highlights • Li 4 Ti 5 O 12 /graphene composites have been successfully prepared by a facile one-step solid-state reaction with sand milling method. • The electrochemical results show that the Li 4 Ti 5 O 12 /graphene composite with 0.93 wt.% graphene exhibits an superior rate performance and long-term cycling stability over the pure LTO. • The GLTO2 composite with 0.93 wt.% graphene prepared by an one-step solidstate method exhibits an excellent electrochemical performance. [ABSTRACT FROM AUTHOR]

Abstract Spinel Li 4 Ti 5 O 12 doped with F was synthesized via the solid-state reaction of anatase TiO 2 , Li 2 CO 3 , and NH 4 F. The structural characterization and electrochemical performance evaluation of the prepared materials were carried out utilizing X-ray diffraction, scanning electron microscopy, galvanostatic charge-discharge, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) tests. The lattice parameters of all samples were calculated using an internal standard and Rietveld refinement method. The results indicate that the F was successfully doped into the lattice structure of Li 4 Ti 5 O 12 , and this process did not influence the crystal structure and superficial morphology. Moreover, the best-performing material, Li 4 Ti 5 O 11.9 F 0.1 delivers superior rate capacities of 165, 162.1, 160.0, 142.3, 125.1, and 99.2 mAh g−1, at 0.2 C, 0.5 C, 1 C, 3 C, 5 C, and 10 C, respectively, which is higher than those of Li 4 Ti 5 O 12 (150.0, 135.0, 123.5, 93.7, 76.4, and 56.8 mAh g−1 at the same C-rates), and the cycling retention is 82.7% after 150 cycles at 5 C. Meanwhile, the charge-transfer resistance (R ct) of Li 4 Ti 5 O 11.9 F 0.1 (56.4 Ω) is lower than that of pure Li 4 Ti 5 O 12 (80.6 Ω), and the lithium-ion diffusion coefficients (D Li +) of Li 4 Ti 5 O 11.9 F 0.1 (2.505 × 10−10 cm2 s−1) is higher than that of pure Li 4 Ti 5 O 12 (1.694 × 10−10 cm2 s−1). Highlights • The F− doped Li 4 Ti 5 O 12 is synthesized and measured in the 1–3 V voltage window. • The F− doped Li 4 Ti 5 O 12 presents an excellent rate capability and an outstanding cycling stability at a high rate of 5C. • The lithium-ion diffusion coefficient (DLi+) is obtained from the Li 4 Ti 5 O 12 and Li 4 Ti 5 O 11.9 F 0.1 electrodes during the extraction/insertion processes. [ABSTRACT FROM AUTHOR]

A novel Li 4 Ti 5 O 12 (LTO) composite with multiwalled carbon nanotubes (CNTs) co-doped with nitrogen (N) and boron (B) (B,N-CNT), denoted N-B-C-LTO, was successfully obtained from a mixture of N,B-CNT and LTO after calcination. For comparison, LTO, C-LTO (LTO/CNT), N-doped N,C-LTO (LTO/N,CNT) and B-doped B,C-LTO (LTO/B,CNT) were also synthesized. Among the samples, N-B-C-LTO demonstrated the best performance in electrochemical measurements. The reversible capacity of N-B-C-LTO could reach 120 mAh/g, even at a rate of 20 C. After 150 cycles at 20 C, 97.5% of the capacity was retained with negligible capacity fading. The excellent electrochemical performance was possibly due to the separate forms of N and B in the co-doped CNTs, which not only maintained the benefits of the N and B additives, i.e., good electron-donating and electron-accepting capabilities, but also led to a synergistic effect from the unique electronic structure. [ABSTRACT FROM AUTHOR]

Spinel Li 4 Ti 5 O 12 co-doped with Mg 2+ and F − was synthesized by solid-state reaction of anatase TiO 2 , Li 2 CO 3 , NH 4 F, and Mg(NO 3 ) 2 . For comparison, Mg 2+ -doped and F − -doped Li 4 Ti 5 O 12 were prepared using the same method. The structure and electrochemical performance of the prepared materials were investigated by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, electrochemical impedance spectroscopy, and galvanostatic charge-discharge tests. Using an internal standard and Rietveld refinement, we calculated the lattice parameters of the samples. After co-doping with Mg 2+ and F − , the dopant ions enter the Li 4 Ti 5 O 12 lattice, resulting in the reduction of Ti 4+ to Ti 3+ , and increasing the conductivity of the material. Furthermore, the Mg 2+ and F − co-doping technique resulted in smaller primary particles with a narrow size distribution, factors that can accelerate transfer of Li + between the electrode and electrolyte. Consequently, the Mg 2+ and F − co-doped Li 4 Ti 5 O 12 material exhibits a superior rate performance and delivers discharge capacities of 159.4, 154.1, 146.5, 120.8, 102.7, and 76 mAh g −1 at 0.2C, 0.5C, 1C, 3C, 5C, and 10C, respectively, significantly higher than those of pure Li 4 Ti 5 O 12 (155.4, 138.6, 124.2, 94.1, 76.7, and 52.2 mAh g −1 at the same C-rates). Moreover, the Mg 2+ and F − co-doped Li 4 Ti 5 O 12 showed outstanding cycling stability, and the capacity retention was 99.62% after 150 cycles at 5C rate. Therefore, the Mg 2+ and F − co-doping technique has proven an effective approach to improve the electrochemical performance of Li 4 Ti 5 O 12 . [ABSTRACT FROM AUTHOR]

The commercial Li 4 Ti 5 O 12 is co-modified using Mg 2+ and F − via a co-precipitation method with the purpose of understanding the reaction mechanism of the fluoride modification process. For comparison, the commercial Li 4 Ti 5 O 12 is also modified using Mg 2+ and F − , respectively. After the co-modification process, F − reacts with Li 4 Ti 5 O 12 chemically to generate new impurity phase such as anatase TiO 2 , rutile TiO 2 and LiF, while Mg 2+ forms MgO coating layer on the Li 4 Ti 5 O 12 particles. The capacity and rate capability of the Li 4 Ti 5 O 12 have been improved after the 1wt% Mg 2+ and F − co-modification. The charge capacity of the Mg 2+ and F − co-modified Li 4 Ti 5 O 12 at 0.5C, 1C, 3C, 5C and 10C rate in the range of 0 ∼3 V is 234.1, 218.6, 200.8, 182 and 148mAh g −1 , respectively. Meanwhile, the electrolyte reduction decomposition on the Li 4 Ti 5 O 12 was suppressed after the co-modification process, thereby enhancing the cycling performance of the Mg 2+ and F − co-modified Li 4 Ti 5 O 12 . In particular, the 3 wt% Mg 2+ and F − co-modified Li 4 Ti 5 O 12 keeps 74.5% charge capacity after 200 cycle charge-discharged test at a high rate of 5C, which is higher than the commercial Li 4 Ti 5 O 12 (58.7%). [ABSTRACT FROM AUTHOR]

The LaF 3 -modified Li 4 Ti 5 O 12 materials have been synthesized via a chemical co-precipitation method, and the effects of different amounts of LaF 3 modification (0.5 wt%, 1 wt%, 2 wt%, and 3 wt%) on the morphology, structure, and electrochemical performance of the Li 4 Ti 5 O 12 (LTO) materials were investigated. X-ray diffraction and X-ray photoelectron spectroscopy (XPS) characterizations show that the La3+ or F− ions are not incorporated into the LTO particles, and major LaF 3 and minor La 2 O 3 peaks are observed in the LaF 3 -modified LTO samples. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that the generated LaF 3 /La 2 O 3 nanoparticles are continuously wrapped around the surfaces of LTO particles. Charge-discharge tests reveal that the 1 wt% LaF 3 -modified LTO material (1LaFLTO) exhibits the highest rate capacity values among all of the samples of 199.9, 187.4 and 159.7 mAh g−1 at 3C, 5C, and 10C, respectively between 0 and 3 V. Moreover, 1LaFLTO also delivers superior cycling stability with a capacity retention of 94.5% after 300 cycles at 5C between 1 and 3 V. The electrochemical results demonstrate that the appropriate LaF 3 /La 2 O 3 nanoparticles coated on the surface of 1LaFLTO particles not only reduce electrode polarization, SEI film resistance, and charge-transfer resistance but also accelerate Li+ diffusion and improve the reversibility, which is favorable for enhancing the electrochemical performance of LTO material. • The LaF 3 -modified LTO materials were synthesized via a chemical co-precipitation method. • The LaF 3 /La 2 O 3 nanoparticles were generated and former a continuous coating layer on the surface of LTO, which could suppress electrolyte decomposition, reduce the side-reactions at the LTO/electrolyte interfaces, and improve the structural stability of LTO material. • The 1 wt% LaF 3 -modified LTO material exhibited the highest rate capacity and cycling stability among all of the samples at voltages of 0–3 V and 1–3 V. The enhanced electrochemical performance of 1 wt% LaF 3 -modified LTO was ascribed to a higher Li+ diffusion coefficient and a lower electrode polarization, SEI film resistance, and charge-transfer resistance after an appropriate amount of LaF 3 /La 2 O 3 formed as a conductive medium coating on the surface of LTO. [ABSTRACT FROM AUTHOR]

Through utilizing a facile solid-state sand-milling method, Li 4 Ti 5 O 12 /carbon nanotubes composites containing different quantities of carbon nanotubes were prepared. A series of characterizations detail the ways in which carbon nanotubes have affected grain morphology and electrochemical properties. It is clearly seen from scanning-electron-microscopy images that the carbon nanotubes have uniformly distributed around the Li 4 Ti 5 O 12 particles and Li 4 Ti 5 O 12 /carbon nanotubes particles are smaller than that of pure Li 4 Ti 5 O 12. The Li 4 Ti 5 O 12 /carbon nanotubes composite with 4.94 wt% carbon nanotubes (denoted as LTO-CNTs-2) exhibits excellent charge capacities at high C-rates (148.3 mAh g−1 at 20 C, 142.6 mAh g−1 at 30 C) and possesses an outstanding cycling performance with a charge capacity of 138.6 mAh g−1 and a capacity retention of 90.2% at 10 C after 900 cycles. Cyclic-voltammetry test indicates that LTO-CNTs-2 exhibits a larger lithium-ion diffusion coefficient (6.53 × 10−10 cm2 s−1) than that of pure Li 4 Ti 5 O 12 (1.15 × 10−10 cm2 s−1). Electrochemical-impedance spectra curves also show that LTO-CNTs-2 delivers the smallest charge-transfer resistance (61.0 Ω) among all samples. The electrochemical performance of LiCoO 2 (denoted as LCO)/pure Li 4 Ti 5 O 12 and LCO/LTO-CNTs-2 full cells are investigated. The LCO/LTO-CNTs-2 full-cell exhibits a superior cycling performance with a discharge capacity as high as 143.9 mAh g−1 and a capacity loss of only 4.2% than that of LCO/pure Li 4 Ti 5 O 12 full-cell at 5 C after 500 cycles, whose discharge capacity is 110.9 mAh g−1 with a capacity loss of 21.8%. • Li 4 Ti 5 O 12 /carbon nanotubes composites have been successfully prepared by a facile one-step solid-state sand milling method. • The electrochemical results show that the Li 4 Ti 5 O 12 /carbon nanotubes composite (denoted as LTO-CNTs-2) with 4.94 wt% carbon nanotubes exhibits a superior rate performance and long-term cycling stability over the pure LTO. • LTO-CNTs-2 composite prepared by a solid-state method exhibits a superior rate performance and long-term cycling stability. [ABSTRACT FROM AUTHOR]

Mg-doped LiNi 0.85 Co 0.10 Al 0.05 O 2 (NCA) is first synthesized through a solid state reaction using available precursors via a nano-scal sand milling method. Compared with other methods of preparing the nickel-rich precursors, the novel way of obtaining nickel-rich precursors is simple and environmental-friendly. X-Ray Diffraction (XRD) results show that Mg-doped NCA displays a typical layered hexagonal structure with no impurity phase or an enlarged c -axis and d (003) as defined by the Rietveld refinement method. Scanning Electron Microscope (SEM) and X-Ray Photoelectron spectroscopy (XPS) results demonstrate the intact particle morphology and increased the percentage of Ni2+ on the surface of Mg-doped NCA materials, respectively. The cyclic voltammetry results exhibit a slight decrease in the polarization of NCA electrodes after Mg doping. Moreover, Mg-doped NCA possesses higher cycling retention at 25 °C and 55 °C than the pure NCA. Meanwhile, Electrical Impedance Spectroscopy (EIS) and Galvanostatic Intermittent Titration Technique (GITT) tests confirm that Mg-doped NCA shows lower total impedance values after 100 cycles, as well as demonstrate a higher lithium-ion diffusion coefficient of Mg-doped NCA (8.196 × 10−13 cm2·s−1) when compared to NCA (3.743 × 10−13 cm2·s−1) at 3.74 V during discharge process. • Pure Mg-doped LiNi 0.85 Co 0.10 Al 0.05 O 2 were first synthesized without using commercially available spherical precursors. • Mg-NCA exhibits better cycling performance at 25 °C and 55 °C. • High nickel content LiNi 0.85 Co 0.10 Al 0.05 O 2 were prepared by a solid state reaction. • The effect of Mg-doping on lithium-ion diffusion coefficient was evaluated. [ABSTRACT FROM AUTHOR]

Mg2+/F− co-doped LiNi 0.5 Mn 1.5 O 4 cathode material was synthesized by a facile one-step solid-state process. The effect of Mg2+/F− co-doping on grain morphology, phase structure, and electrochemical properties was studied by a series of characterizations. Scanning-electron-microscopy images show that Mg2+/F− co-doped LiNi 0.5 Mn 1.5 O 4 (denoted LNMO-MF) particles grow larger than pure LiNi 0.5 Mn 1.5 O 4 particles. X-ray diffraction, Raman spectra, Fourier transformation infrared spectroscopy, X-ray photoelectron spectroscopy, and cyclic-voltammetry tests indicate that all samples mainly display a Fd -3m space group and more Mn3+ ions in the LNMO-MF sample after Mg2+/F− co-doping, which is conducive to increasing the cationic disorder degree and enhancing the electronic conductivity of electrode material. Results show that the LNMO-MF cathode material delivers an excellent rate performance with discharge capacities of 142, 144, 140 136, 132, 124, 115, and 100 mAh g−1 at 0.2, 0.5, 1, 2, 3, 5, 7, and 10C (1C = 140 mAh g−1), respectively. Remarkably, LNMO-MF also shows cycling stability with a capacity retention of 86.2% at 5C after 400 cycles, which is much higher than that of pure LiNi 0.5 Mn 1.5 O 4 (67.7%). The improvement of LNMO-MF's electrochemical properties could be ascribed to the Mg2+/F− co-doping, delivering a more stable structure, better crystallinity, the highest Li+ diffusion coefficient, and the lowest charge-transfer resistance. [ABSTRACT FROM AUTHOR]