| In order to examine the possibility of using the processing graphite wastes from an electric-carbon factory as the negative electrode materials in lithium ion batteries (LIB), the original samples were heat-treated with different maximum heat treatment temperatures (HTTmax). The microstructures of these heat-treated samples were characterized by their densities, ash contents and XRD spectra. The charging-discharging performances of them were investigated by galvanostatic charging-discharging experiments. The relationship between their charging-discharging performances and microstructures was discussed and the optimized heat treatment technology was determined. Sample XT-28 has a good structure for storing up lithium ions. The compatibility of it with six different kinds of electrolytes was investigated by the galvanostatic charging-discharging experiments, powder microelectrode cyclic voltammetric experiments and FTIR analysis. The influences of some other factors: thegranularity of sample, the content of conductive additive--acetylene black and thecontent of binder--PTFE in the carbon membrane and the charging-dischargingcurrent density etc, on the charging-discharging performances of sample XT-28 were investigated by the orthogonal method through galvanostatic charging-discharging experiments. The cyclic performance of the sample XT-28 under the best experimental conditions was investigated by the powder microelectrode cyclic voltammetric experiments. The experimental results are as follows:1. The heat treatment technology--extracting air during heating from roomtemperature to 2400℃ is helpful to remove part of impurities in the original sample. However, the HTTmax can not be lower than 2800 ℃, if we want to remove the impurities SiC and FesC which hinder the lithium ions from diffusing inside the sample. For saving energy, the best HTTmax of sample should be 2800℃ and sample XT-28 is the best one. In the third cycle, its discharging capacity is 330.2mAh/g and the charging-discharging efficiency is 97.5%.2. Solid electrolyte interphase (SEI) films are formed on the surfaces of the particles of sample in six different electrolytes during the first charging process. The main content of all the SEI films is lithium carbonate. EC-based electrolytes can react with the surfaces of particles moderately and form thin and compact SEI films which only the lithium ions can pass through. On the contrary, the reaction between PC-based electrolytes and the surfaces of particles are intense and the SEI films are thick and nonhomogeneous, which the lithium ions are difficult to pass through.3. According to the results of orthogonal experiments, when sample XT-28 charges and discharges in the electrolyte of 1 mol/L LiC104/EC+DEC(1:1), the factors such as the granularity of sample XT-28 (A), the content of acetylene black (B) and the content of PTFE (C) in the carbon membrane and the charging-discharging current density (D) also make influences on the discharging capacities and the charging-discharging efficiencies of the 3rd cycle (D3 and η3). The influence degree orders of the above four factors on D3 and η3 are the same, that is B>D>A>C. However, the influence on D3 (maximum difference R=23.1~37.3mAh/g) is much greater than that on η3 (R=0.3~1 .2%). The best level combination of the above four factors is A2B3C2D2: the granularity of sample XT-28 is at level 2 (-325 mesh), the content of acetylene black in carbon membrane is at level 3 (6%), the content of PTFE in carbon membrane is at level 2 (5%) and the charging-discharging current density is at level 2 (15mA/g), while D3 is larger than 338.7mAh/g and η3 is greater than 96.1%.4. The powder microelectrode cyclic voltammetric experiments show that sample XT-28 has a good cyclic performance. In the 500th cycle, the discharging capacity keeps 72.22% of the maximum discharging capacity (in the 60th cycle) and the charging-discharging efficiency of the 500th cycle is 93.35%.
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