Olivine LiMPO 4 (M = Fe and Mn) cathode materials are already present in commercial batteries for diverse applications ranging from tools to electric vehicles due to their excellent thermal stability, compared to LiCoO 2 . [1][2][3][4][5][6][7][8][9][10][11] LiMnPO 4 (LMP) offers a higher energy density than LiFePO 4 due to its higher redox potential (4.1 V vs. Li/Li + ). However, LMP ( > 10 − 10 Scm − 1 ) suffers from lower intrinsic electrical and ionic conductivities than LiFePO 4 ( > 10 − 8 Scm − 1 ), resulting in much poorer electrochemical performance. In response, strategies including carbon coating on LMP, minimizing particle size, and Mn-site substitution have been applied in efforts to improve the electrochemical performance. [12][13][14][15] Several reports have also noted that the electrochemical performance of LMP is not dramatically enhanced, even when the particle size is decreased to the nanoscale ( ∼ 30 nm) and after carbon coating ( > 20 wt%). [16][17][18][19][20][21][22][23][24][25][26][27] Martha et al. [ 17 ] synthesized platelet-like carbon-coated LMP by a polyol method. After ball-milling of the LMP plate with carbon, core-shell composites consisting of < 5 nm carbon coating layer and ∼ 10 nm LMP were obtained. The results showed a practical capacity of 140 mAhg − 1 and 120 mAh g − 1 at 0.1 C; however, this rather rapidly decreased to 70 mAg − 1 at a 5C charge rate at 30 ° C. In general, cathode materials with poor electrical conductivity tend to increase in specifi c capacity with increasing temperature; however, cycling data including rate capability need to show results at 21 ° C.Considering all these factors, a 3D microporous (3DM) structure in which nanoparticles are well dispersed in the carbon matrix is the best choice to maximize the capacity of an LMP cathode. The advantage of 3D electrodes [ 28 , 29 ] are: 1) the solidstate diffusion length of lithium ions is on the order of a few tens of nanometers; 2) there are a large number of active sites for charge-transfer reactions because of the material's high surface area; and 3) reasonable electrical conductivity of the 3DM carbon matrix. These factors lead to signifi cantly improved rate performance compared to other nanoparticles.In this paper, we describe a method for fl exible construction of 3DM-LMP balls and fl akes using a polymethylmethacrylate (PMMA) template. PMMA colloidal crystals provide a fi rm scaffolding onto the dried LMP precursor solution; once removed during calcination, LiMnPO 4 particles feature pores with a diameter of about 250 nm and porewall thickness of about 40 nm. Depending on the impregnation step of the LMP precursor solution, 3DM balls and fl akes with similar porewall size and porewall thickness were obtained. Both samples demonstrated excellent rate capability and capacity retention both at 21 ° C and 60 ° C. Figure 1 shows the schematic view of the preparation procedure for 3DM-LMP balls and fl akes on a Si substrate. A dilute PMMA solution was fi rst poured onto a Si substrate and dried. This was fo...

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Ni-rich layered LiNi 0.84 Co 0.10 Mn 0.06 O 2 cathode material was modified by doping with vanadium to enhance the electrochemical performances. The XRD, FESEM and XPS analyses were indicated that the vanadium is successfully doped in the crystal lattice of LiNi 0.84 Co 0.10 Mn 0.06 O 2 with high crystallinity. 0.05 mol% vanadium doped LiNi 0.84 Co 0.10 Mn 0.06 O 2 exhibits superior initial discharge capacity of 204.4 mAh g −1 , cycling retention of 88.1% after 80 cycles and rate capability of 86.2% at 2 C compared to those of pristine sample. It can be inferred that the vanadium doping can stabilize the crystal structure and improve the lithium-ion kinetics of the layered cathode materials.

Ni-rich cathode is one of the promising candidate for high-energy lithium-ion batteries. In this work, we prepare the different super-P carbon black amounts [0.1 (SPB 0.1 wt%), 0.3 (SPB 0.3 wt%), 0.5 (SPB 0.5 wt%) and 0.7 wt% (SPB 0.7 wt%)] of carbon coated LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes and their electrochemical performances are investigated. Carbon coating does not change the crystal structure and morphology of NCM811. Among the coated NCM811, the SPB 0.5 wt% NCM811 delivers the excellent cyclability (87.8% after 80 cycles) and rate capability (86.5% at 2 C) compared to those of pristine NCM811. It is ascribed to that the carbon coating not only increase the Li ion and electron transfer as well as protect the NCM811 cathode materials from side reaction at the electrolyte/NCM811 interface. Therefore, we can conclude that the appropriate amount of carbon coating can be regarded as an effective approach for Ni-rich NCM cathode.

Boron-doped Ni-rich LiNi0.84Co0.10Mn0.06O2 (B-NCM) cathode material is prepared and its electrochemical performances are investigated. The structural properties indicate that the incorporation of boron leads to highly-ordered layered structure and low cation disordering. All samples have high areal loadings of active materials (approximately 14.6 mg/cm2) that meets the requirement for commercialization. Among them, the 1.0 wt% boron-doped NCM (1.0B-NCM) shows the best electrochemical performances. The 1.0B-NCM delivers a discharge capacity of 205. 3 mAh g−1, cyclability of 93.1% after 50 cycles at 0.5 C and rate capability of 87.5% at 2 C. As a result, we can conclude that the 1.0B-NCM cathode can be regarded as a promising candidate for the next-generation lithium ion batteries.