In order to improve the accuracy of the GRU neural network model in predicting the remaining useful life (RUL) of lithium-ion batteries, the GRU model was optimized based on PCA-GWO and then applied in the prediction. The results show that compared with the traditional GRU model, the PCA-GWO-GRU model presents higher prediction accuracy. When the starting point of the prediction is 90% of the original data, the prediction accuracy can reach the highest, with the corresponding RMSE of 0.004 9, MAE of 0.003 6, and R² of 0.986 3.

The factors and reasons influencing lime activity are presented, and the influencing mechanism of lime activity for digestion performance of bauxite is also expounded. It is found that the particle size of limestone and calcination temperature are two important factors influencing activity of lime. At a calcination temperature of 1 000 ℃, the activity of lime is as high as 33.5 mL, while with the particle size of limestone increased to 17.5-22.5 mm, the activity of lime increases to 46 mL. The analysis results of scanning electron microscopy show that highly active lime has fine particles with uniform particle size and in a structure of honeycomb with well-developed and interconnected pores. The experiment of bauxite digestion shows that the activity of lime and its adding amount will bring influence to the digestion rate of bauxite and the phase composition of red mud. By adding highly active lime with a C/S ratio of 1.0, the relative digestion rate of bauxite is as high as 98.12%.

With manganese sulfate as raw material and hexadecyl trimethyl ammonium bromide as modifier, trimanganese tetroxide was synthesized by complex-precipitation method, with which lithium manganate cathode material was then synthesized by high-temperature solid-state reaction. The effects of modifier amount on the morphology and particle size of trimanganese tetroxide and the specific discharge capacity of lithium manganate cathode material were all discussed. Results show that serious particle agglomeration can occur in the trimanganese tetroxide synthesized without modifier. With 3.0 g/L hexadecyl trimethyl ammonium bromide as the modifier, the synthesized trimanganese tetroxide has uniform particle size, and is dispersed without any agglomeration. Spinel lithium manganate was synthesized with the self-made modified trimanganese tetroxide, and then compared with the spinel lithium manganate synthesized with three kinds of trimanganese tetroxide available on the market. The results show that the lithium manganate synthesized with the self-made modified trimanganese tetroxide can present better electrochemical performance, delivering an initial discharge capacity of 120.43 mAh/g, with a retention rate of 96.79% after 50 cycles at 1C.

A mineral processing test was conducted to treat a low-grade rubidium-bearing lepidolite ore from Hunan Province with the grade of Li₂O and Rb₂O respectively at 0.27% and 0.17%. A flowsheet including a desulphurization and a lithium flotation was adopted, and an efficient collector CK was used in combination with dodecylamine to collect lithium minerals under weak alkaline conditions. In a closed-circuit test, a lithium concentrate was produced with Li₂O grade and recovery of 2.71% and 86.34%, Rb₂O grade and recovery of 1.02% and 51.24%, respectively. It is concluded that efficient utilization of low-grade lepidolite ore can be actualized.

A single-factor experiment was conducted to explore the influence of rotation speed and lateral swing speed of polishing brush, and polishing current on the performance of copper foil and pinholes. Based on that, the polishing process was also optimized by applying response surface methodology, and thus the performance and apparent quality of copper foil was also improved. The results show that by using on-line polishing, with the rotation speed of the polishing brush at 450 r/min, the lateral swing speed of 350 r/min, and the polishing current of 0.50 A, the smooth surface (S surface) of the generated copper foil is uniform, and the pinhole defects are significantly reduced.

The influence of polyether additives on performance of ultra-thin Li-ion battery copper foil with thickness of 5 μm was studied by electrochemistry, scanning electron microscopy, and X-ray diffractometer. The results show that addition of polyether additives into electrolyte can promote negative shift of Cu deposition potential, and polyether additives with suitable concentration can lead to finer grains of copper foil, which is conducive to improving the surface flatness of copper foil. When the mass concentration of polyether additives is 2.3 mg/L, the obtained copper foil has tensile strength of 620.43 MPa, elongation of 3.67%, glossiness of 161 GU, and surface roughness of 1.02 μm, presenting excellent overall performance. The electrolytic copper foil with high tensile strength has a preferred orientation of (111) plane.

Cathode and anode materials in spent lithium iron phosphate battery powder are difficult to be separated by flotation. In order to solve this problem, it was proposed that lithium iron phosphate battery powder was pretreated by oxidative roasting, and then subjected to a flotation process for seperation between the cathode and anode materials of lithium iron phosphate. The results show that after lithium iron phosphate battery powder is pretreated by oxidative roasting at 500 ℃ for 30 minutes, the subsequent flotation process can lead to the graphite-based anode material with carbon grade up from 47.63% to 97.70%, and the cathode material with carbon grade down from 24.00% to 1.01%, presenting a significant separation effect. In comparison, the battery powder without pretreatment has cobweb-like long carbon-chain organic matter on its surface, which causes adhesion between cathode and anode materials of batteries, resulting in poor separation effect by flotation. The pretreatment of oxidative roasting can effectively eliminate the long carbon-chain organic matter on those cathode and anode materials, thus enhancing the difference in surface properties between cathode and anode materials. As a result, the enhanced flotation separation effect makes graphite-based anode material recycled from spent lithium iron phosphate batteries.

With an increase in Ni content, the capacity of high-nickel layered metal oxides (LiNi_xMn_yCo_1-x-yO₂ (0.8≤x<1, NCM) greatly decreases. In view of such problem, it is proposed that singly-crystal NCM cathode material be modified by dual SiO₂@Li₂SiO₃ coating to improve its electrochemical performance. During the synthesis process, the reaction of can consume the residue lithium on the material surface, thus improving diffusion kinetics of interface lithium ions and inhibiting side reaction at the interface. It is shown that the modified cathode material delivers a specific discharge capacity of 156.88 mAh/g after 120 cycles, with capacity retention rate of 70.52%.

A flotation experiment was conducted for a low-grade fine-grained cassiterite from Yunnan. The median dosage of reagent was determined by a single-factor test, and then the reagent dosage for rougher flotation process of cassiterite was optimized by response surface methodology as follows: 285 g/t of activator (KT-51), 13 g/t of inhibitor (OL-1C) and 873 g/t of compound collector (YK-Sn+SN-705). A verification test on flotation with the addition of those agents yielded a tin rougher concentrate grading 1.460% Sn at 74.44% recovery, which was close to the results predicted by response surface methodology. In order to further explore the effect, a closed-circuit test was conducted, resulting in the tin concentrate grading 5.45% Sn at 66.70% recovery. It is shown that efficient recovery of low-grade cassiterite resources can be actualized.

With a flake graphite ore from Africa as the raw material, a beneficiation technique was adopted to recover graphite resource according to ore size fraction. The results show that the fixed carbon content of the graphite feed ore is 32.54%, and the large flake graphite mainly in sheet or banded structure is intergrown with feldspar minerals. The optimized roughing condition is determined as follows: grinding fineness of -0.074 mm 72.87%, kerosene dosage of 50 g/t and terpineol dosage of 150 g/t. A flotation process with one stage of roughing, one stage of scavenging and four stages of cleaning is adopted, in which the large flake graphite is screened from the flotation production of the 1st-stage of cleaning, while the undersize is treated further by three stages of grinding and three stages of cleaning to recover fine flake graphite. The closed-circuit test shows that the fixed carbon content in the large flake graphite (+0.150 mm) concentrate and the fine flake graphite (-0.150 mm) concentrate reaches 96.53% and 96.21%, respectively. The recovery rate of the large flake graphite reaches 22.74%, which is higher by 7.66 percentage points compared to that by conventional regrinding-separation approach.