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Important progress has been made in the study of LiFePO4, a positive electrode material for lithium ion batteries


Lithium ion battery is a necessary power supply for mobile electronic equipment in today's society. It is composed of positive electrode, negative electrode, diaphragm and electrolyte, etc. Its key performance indexes (such as multiplier performance and cycle life) are determined by the electrochemical performance of positive electrode materials.LiFePO4 is recognized as a positive electrode material. In order to improve its electrochemical performance, people have long been committed to shortening the diffusion distance of lithium ions, that is, reducing the size in the direction of [010].Recent studies have shown that the electrode is composed of a large number of particles, and its electrochemical performance mainly depends on the proportion of the total number of particles (activated particles) involved in the electrochemical reaction during charging and discharging.Therefore, how to obtain LiFePO4 with a high ratio of activated particles is a key problem in the research of positive electrode materials.

To solve this problem, Wang Xiaohui's research group, High Performance Ceramic Materials Research Department, National (Joint) Laboratory of Materials Science, Shenyang Institute of Metals, based on the previous research (J. Phys.Chem. C 114:16806 (2010);Phys. Chem. Chem. Phys. 14: 2669 (2012); Crystengcommuncommunit16:10112 (2014)), by creating an acidic synthetic environment with extreme water shortage, made the first [100] nanometer LiFePO4 nanosheet with a thickness of 12 nm in the world.The voltage hysteresis test results showed that the electrode composed of this material had the smallest voltagegap (voltagegap) so far. The potentiometric gap titration test results indicated that this electrode had high activation rate and conversion rate. These results indicated that the electrode composed of [100] oriented LiFePO4 ultra-thin nanometer sheet had a high ratio of activated particles.Therefore, the electrode has excellent multiplier performance and cycle life.At 10C (60 min /10= 6 min) charge and discharge rate, 90% of the initial capacity can be maintained after 1000 cycles.The capacity can still reach 72% of the theoretical capacity at 20C charge and discharge ratio.The work for the future to further improve the lithium ion battery performance ratio provide new method and Angle, which can not only by reducing the scale of the [010] direction to shorten the lithium ion diffusion distance, at the same time also can control the size of the [100] direction to increase the activation of lithium ion battery population proportion to improve the lithium ion battery performance ratio.The results are published in the January 13, 2016 issue of Nano Letters (16:795-799).

This work is supported by the "Introduction of outstanding scholars" of Institute of Metals and the Youth Innovation Promotion Association of the Chinese Academy of Sciences.

Figure 1(a) XRD pattern of newly synthesized samples and samples dispersed and then dripped onto amorphous silicon.(b) A diagram of Figure A.(c,d) TEM diagram of LiFePO4.(e) The electron diffraction pattern corresponding to (d).Gauss function was used to fit the size statistics of LiFePO4 grains along different directions.(f) Axis A, 12nm; (g) Axis B, 134nm; (h) Axis C, 280nm.

FIG. 2(a) schematic diagram of [100] orientation, microwave-assisted synthesis and [010] orientation LiFePO4.(b) In different charge and discharge currents, from C/2 to C/100, the voltage gap of three electrodes is composed of [100] oriented, microwave-assisted synthesis and [010] oriented LiFePO4.(c) in LiFePO4 Li chemical potential relative to a function of Li score changes, there is a big change barrier (Δ mu b), defined as the maximum and without phase immiscible area in the middle of the chemical potential difference.(d)[100] Orientation and microwave assisted synthesis of LiFePO4 electrode potentiometric gap titration and its fitting experimental data results.