A series of LiFe1−xZnxPO4 (0.0 ≤ x ≤ 1.0) compounds were prepared by solid-state reaction. Effects of the substitution of Zn for Fe on crystal structure and electrochemical properties of LiFe1−xZnxPO4 were investigated. The results show that single-phase regions of LiFe1−xZnxPO4 with orthorhombic (space group Pmna) and monoclinic (Cc) structures were found for the compounds with low Zn (or high Fe) contents of 0.0 ≤ x ≤ 0.30 and high Zn (or low Fe) contents of 0.90 ≤ x ≤ 1.0, respectively. The LiFe1−xZnxPO4 compounds with medium Zn (or Fe) contents of 0.35 ≤ x ≤ 0.80 are two-phase mixtures containing both the orthorhombic and the monoclinic phases. Systematic variations of unit-cell parameters a, b, c, and volume V with the Zn content determined by X-ray diffraction have also been obtained. Our electrochemical study show that the conductivity of LiFe1−xZnxPO4 increases by almost 2 orders of magnitude from 2.13 × 10−9 to 1.27 × 10−7 Scm−1 as the Zn content increasing from x = 0 to 0.3. The initial specific capacity decreases and the cycle performance increase with increasing Zn-doping content in the four orthorhombic LiFe1−xZnxPO4 compounds. Among the four LiFe1−xZnxPO4 compounds, LiFe0.8Zn0.2PO4 has the highest capacity retentions after 6 to 20 cycles and the capacity retention is 93.7% after 20 cycles, even though the initial discharge specific capacity of LiFe0.8Zn0.2PO4 is lower than those of LiFeZnPO4 and LiFe0.9Zn0.1PO4. LiFe0.7Zn0.3PO4 has the highest capacity retention of 97% after 20 cycles.

Co-doped Li3V2−xCox(PO4)3/C (x = 0.00, 0.03, 0.05, 0.10, 0.13 or 0.15) compounds were prepared via a solid-state reaction. The Rietveld refinement results indicated that single-phase Li3V2−xCox(PO4)3/C (0 ≤ x ≤ 0.15) with a monoclinic structure was obtained. The X-ray photoelectron spectroscopy (XPS) analysis revealed that the cobalt is present in the +2 oxidation state in Li3V2−xCox(PO4)3. XPS studies also revealed that V4+ and V3+ ions were present in the Co2+-doped system. The initial specific capacity decreased as the Co-doping content increased, increasing monotonically with Co content for x > 0.10. Differential capacity curves of Li3V2−xCox(PO4)3/C compounds showed that the voltage peaks associated with the extraction of three Li+ ions shifted to higher voltages with an increase in Co content, and when the Co2+-doping content reached 0.15, the peak positions returned to those of the unsubstituted Li3V2(PO4)3 phase. For the Li3V1.85Co0.15(PO4)3/C compound, the initial capacity was 163.3 mAh/g (109.4% of the initial capacity of the undoped Li3V2(PO4)3) and 73.4% capacity retention was observed after 50 cycles at a 0.1 C charge/discharge rate. The doping of Co2+into V sites should be favorable for the structural stability of Li3V2−xCox(PO4)3/C compounds and so moderate the volume changes (expansion/contraction) seen during the reversible Li+ extraction/insertion, thus resulting in the improvement of cell cycling ability.

Single-phase lithium manganese borate, LiMnBO3, was obtained at the temperature higher than 850°C by one-step solid state reaction without using carbon black in the starting materials. The initial specific discharge capacity for the cathode active material was 75.5mAh/g at the current density of 5mA/g and the mean fade of capacity was 0.09% per cycle except for the first cycle. The LiMnBO3 compound maintained a specific discharge capacity of 42.3mAh/g even at the current density of 50mA/g and the capacity fade per cycle was only 0.2% during 40 cycles. The cyclic voltammograms (CV) curves show that the Mn3+/Mn2+ redox couple situated at 2.23 and 4.13V can be clearly observed during anodic and cathodic sweeps. Combined the cyclic voltammograms results with the X-ray diffraction patterns of electrodes before and after cycling, where no significant change of the peak currents and the peak potentials during cycling, it was anticipated that the extraction and insertion of Li-ions are totally reversible in this compounds and the hexagonal structure for LiMnBO3 can be maintained after long cycles under high charge and discharge rate.

Li-ion battery cathode materials Li3V2-xCrx(PO4)3/C(x=0,0.05,0.10 and 0.20)were synthesized by sol-gel method.The effects of Cr doping on the samples were studied by the methods of XRD,SEM,charge-discharge,cyclic voltammetry and conductivity test.The samples were single phase.Although the initial specific capacity at low rate(0.2 C)decreased with the increasing of x,but proper Cr doping could improve its cycle and rate performance.When charge-discharge at 0.2 C and 4.0 C,the initial specific discharge capacities of Li3V1.90Cr0.10(PO4)3/C were 171.4 mAh/g and 130.2 mAh/g,respectively,the capacity retention at the 100th cycle were 78.6% and 88.9%,respectively.

Cr-doped Li3V2−xCrx(PO4)3/C (x=0, 0.05, 0.1, 0.2, 0.5, 1) compounds have been prepared using sol–gel method. The Rietveld refinement results indicate that single-phase Li3V2−xCrx(PO4)3/C with monoclinic structure can be obtained. Although the initial specific capacity decreased with Cr content at a lower current rate, both cycle performance and rate capability have excited improvement with moderate Cr-doping content in Li3V2−xCrx(PO4)3/C. Li3V1.9Cr0.1(PO4)3/C compound presents an initial capacity of 171.4mAhg−1 and 78.6% capacity retention after 100 cycles at 0.2C rate. At 4C rate, the Li3V1.9Cr0.1(PO4)3/C can give an initial capacity of 130.2mAhg−1 and 10.8% capacity loss after 100 cycles where the Li3V2(PO4)3/C presents the initial capacity of 127.4mAhg−1 and capacity loss of 14.9%. Enhanced rate and cyclic capability may be attributed to the optimizing particle size, carbon coating quality, and structural stability during the proper amount of Cr-doping (x=0.1) in V sites.

Ni-doped Li3V2-xNix (PO4)3 compounds were prepared successfully by sol-gel process with Li2CO3, V2O5, NH4H2PO4, citric acid, and Ni (OH)2·H2O as the reactant. The results of Rietveld refinement analysis indicate that single-phase Li3V2-xNix (PO4)3 with monoclinic structure can be obtained for x 0.15. X-ray photoelectron spectroscopy analysis suggests that a- axis, c-axis and the cell volume decrease with the increasing of Ni content. There is a large increase in electrical conductivity even with Ni doping . Ni doped Li3V1.95Ni0.05(PO4)3 can deliver the initial capacity of 177.2 mAh/g and 136.6 mAh/g at 0.1 C and 3 C respectively and 94.2% capacity retention can still be held after 100 cycles at 3 C rate.

Arc ion plating(AIP) has higher deposition rates, whereas macro-particles (MPs) make the film properties decreasing. In this paper, AIP with or without magnetic filter (MF or AIP) and composition of AIP followed with magnetic filter (MFAIP) were designed to deposit TiN films on silicon (Si) and high-speed steel(HSS), respectively. Scanning electron microscope (SEM), nanoindentation and microscratch tests were investigated. SEM showed that both the MF and the MFAIP films had a superfine layer among the columnar crystals grown vertically against substrate surface. However, the columnar crystals of MF films were leptosomatic and well-orientational, while MFAIP ones were coarse and short, and even ragged in size and orientation. Nanoindentation test results showed the highest hardness for MF films and the lowest one for AIP films. A new parameter Scratch Crack Propagation Resistance (CPRs) was introduced to evaluate the film adhesion properties in a scratch test. MF films had the highest adhesion. AIP films were most susceptible to failure as the CPRs was the lowest, although the Lc1 was higher than MFAIP ones. It was proposed that the MPs were effectively removed with the MF, and the MF layers were superfine to improve the properties of the films.