Li_0.97Na_0.03Fe_7/8Mn_1/8PO₄cathode materials were successfully prepared by carbothermal reduction method.The crystal structure,morphology,elemental distribution,and electrochemical performance of the material were studied by XRD,SEM,EDS,and electrochemical tests,with first-principle calculation being used to analyze the mechanism of the material′s improved performance.The results show that on the one hand,Na-Mn doping leads to the lattice distortion in LiFePO₄and the expansion of lattice volume,expanding the lithium ion migration channels and providing more space for lithium ion insertion and extraction.On the other hand,the material exhibits excellent high-rate performance and cycle stability in electrochemical performance.Na-Mn doping is advantageous in improving the lithium-ion diffusion coefficient and conductivity of the material,thereby improving its electrochemical performance.The first-principle calculation results show that Na-Mn co-doping induces lattice expansion of LiFePO₄,increases lattice volume,narrows energy band gap,enhances electronic density of states near Fermi level,and improves the electronic conductivity and lithium ion mobility of the material.

Lithium-rich manganese-based cathode material Li_1.2Mn_0.54Ni_0.13Co_0.13O₂was prepared by co-precipitation,sol-gel,and solid phase methods,and the phase composition and microstructure of the synthesized material were characterized by XRD,SEM,EDS,etc.The electrochemical performance of the CR2032 button type half cell assembled from the synthesized material was tested using a battery testing system.The results indicate that lithium-rich manganese-based cathode materials with a layered structure have been successfully synthesized by the three synthesis methods.Among them,the sample prepared by co-precipitation method exhibits the lowest degree of cation mixing,and has uniform elemental distribution and particle size,clear grain boundary edges,and no obvious agglomeration.In terms of electrochemical performance,the first cycle discharge specific capacity of the sample synthesized by co-precipitation method at a rate of 0.1 C reaches the highest within the voltage range of 2.0~4.8 V.Moreover,after 100 cycles,the prepared sample still maintains a discharge specific capacity of 195.8 mA·h/g,with a capacity retention rate of 87.3%.Comparatively,the samples prepared by sol-gel method and solid phase method has lower capacity retention rates of only 84.5%and 83.8%,respectively.And compared with the samples prepared by sol-gel method and solid phase method,the co-precipitation method can effectively improve the Li⁺transport efficiency of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂cathode material,thereby improving the rate performance of the sample.

Lamellar Ni-rich Co-free cathode material LiNi_0.94Mn_0.04Al_0.02O₂(NMA)was synthesized by a solid-phase sintering process,and the effects of different sintering temperatures on the crystal structure,microstructure and electrochemical performance of NMA cathode material were investigated.The results show that with excessively low sintering temperature,the crystallinity of the NMA cathode material is re-latively low and residual lithium is formed on the surface,while the extremely high sintering temperature leads to a deterioration of the lamellar structure and an increase in harmful side reactions on the electrode surface.The NMA-750 material synthesized at the optimal temperature of 750℃demonstrates excellent particle morphology,minimal lithium-nickel mixing,and the most complete lamellar structure.Simultaneously,the material exhibits the optimal electrochemical performance:its initial discharge specific capacity(3.0~4.5 V,1 C)is 199.5 mA·h/g,and the capacity retention rate reaches 79.04%after 100 cycles.It also has a discharge specific capacity of 147.6 mA·h/g at 5 C,presenting excellent rate performance.

《稀有金属与硬质合金》由中国有色金属学会和长沙有色冶金设计研究院有限公司联合主办,长沙有色冶金设计研究院有限公司负责编辑出版,为2023版北大中文核心期刊、中国科学引文数据库来源期刊,入编《中国学术期刊(光盘版)》和《中国科技期刊数据库》等数字化网络。

为适应我国信息化建设需要,扩大读作者学术交流渠道,本刊——《稀有金属与硬质合金》已许可中国知网、维普资讯及超星信息等数据库以数字化方式复制、汇编、发行、信息网络传播整刊全文。本刊支付的稿酬已包含上述各数据库的著作权使用费,所有署名作者向本刊提交文章发表之行为视为同意上述声明。

To address the technical challenges in the comprehensive development and utilization of Nanling tungsten-tin polymetallic resources,an acid-alkali combined decomposition process was employed to treat low-grade tungsten-tin mixed ore,achieving efficient leaching of tungsten and resourceful enrichment of tin.The influences of various parameters on the decomposition of tungsten minerals and the reaction behavior of cassiterite during the leaching process were investigated.The results demonstrate that the decomposition of the scheelite component in the minerals requires a high concentration of HCl to provide sufficient driving force,while excessively high H_3PO_4 concentration is detrimental to it.The efficient decomposition of wolframite component is achieved using the conventional alkali autoclaving method,with the associated Sn being enriched in the alkali decomposition slag.In the acid leaching process,a mixed acid of 5 mol/L HCl+75 g/L H₃PO₄ is used as the leachant.Under the process conditions of a liquid-to-solid ratio of 2.5∶1,a reaction temperature of 80℃,and a reaction time of 2 h,the W leaching rate is 77.89%and the W content in the slag is 4.58%.In the alkali leaching process,controlling the conditions of a NaOH concentration at 300 g/L,a liquid-to-solid ratio of 1.25∶1,a reaction temperature of 130℃,and a reaction time of 1.5 h,the W leaching rate could reach 99.79%with the W content in the slag only of 0.06%.The complex occurrence state of Sn in the mixed ore causes its slight loss in both acid and alkali leaching systems.The Sn content in the alkali decomposition slag is enriched to 11.21%,which can be used as a medium-grade tin concentrate for resource utilization.

In the acid leaching of scheelite,the decomposition method that tungsten is produced in the form of isopolytungstate provides a new way for scheelite smelting.However,the subsequent recovery of tungsten from the leaching solution of isopolytungstate matters.This paper compared the adsorption behaviors of different anion exchange resins in isopolytungstate solution and determined that the macroporous weak-base anion exchange resin D301 was the optimal resin.The effects of D301 resin dosage,solution pH,adsorption temperature,tungsten concentration,and adsorption time on the resin′s adsorption of tungsten were investigated.The results show that under the conditions of a resin dosage of 5 times the theoretical amount,solution pH of 2~3,adsorption temperature of 40℃,WO₃ concentration of 50~100 g/L,and adsorption time of 240 min,the adsorption rate of D301 resin for tungsten in the isopolytungstate solution exceeds 99.4%.In addition,the desorption behaviors of tungsten loaded resins were also studied.The results show that NaOH serves as the most effective desorption agent for tungsten loaded D301 resin.And under the conditions of a NaOH solution dosage of 20 mL,NaOH concentration of 4 mol/L,desorption temperature of 50℃,and desorption time of 60 min,the tungsten desorption rate reaches 97.94%.

An oxidative leaching process of hydrogen peroxide combined with ammonia was proposed for selective leaching of molybdenum from spent nickel-molybdenum hydrogenation catalysts.The effects of hydrogen peroxide dosage,leaching temperature and leaching time on the leaching rate of molybdenum were studied by experiments,and the leaching residue was characterized by SEM,EDS and XRD.The results show that the leaching rate of molybdenum can reach over 97%under the conditions of a reaction system pH of 8~9 maintained by adding ammonia,hydrogen peroxide dosage of 2.0 times the theoretical amount,leaching temperature of 80℃,leaching time of 120 min,and stirring speed of 250 r/min,while the dissolution rates of aluminum and nickel remain at a low level.

The sources,properties,and treatment measures of three wastes in the hydrometallurgical process of tantalum-niobium concentrate are comprehensively introduced.Among the three wastes,the waste water undergoes refined treatment,with the extraction raffinate containing radioactive substance or heavy metals being treated separately,achieving complete reuse through resource processing without any discharge.Other production wastewater is treated using lime for step-by-step defluorination and desulfation and negative pressure stripping deammoniation for ammonia recycling.The stripping deammoniation effluent is subjected to pH adjustment,flocculent deposition,and deep defluorination before being discharged to meet the standards.All exhaust gases are collected and sent to the purification system for discharge at high altitude after purification.The purification efficiency of pollution factors in process waste gas,dry waste gas and calcined waste gas exceeds 90%,and the boiler flue gas can be directly discharged by using low-nitrogen burners.Low-level radioactive solid waste and hazardous waste are temporarily stored in the radioactive residue storage and hazardous waste storage within the plant respectively,and are regularly entrusted to qualified units for disposal.General industrial solid waste is either comprehensively utilized or undergoes regular sanitary landfill with domestic waste.The process design not only realizes the standard discharge of three wastes but also promotes the efficient recovery and recycling of resources.

In the process of tantalum niobium hydrometallurgy producing tantalum/niobium oxides,the washing of tantalum/niobium hydroxides generates a large amount of alkaline wastewater with high ammonia nitrogen content,which is treated with stripping deammoniation columns by most smelting plants currently.The qualified treated wastewater generally has a temperature higher than 70℃.And a great deal of high-temperature waste flue gas is generated with the calcination of tantalum/niobium hydroxides.The energy storage waste heat recovery technology introduced in this paper utilizes a plate heat exchanger to recover waste heat from the wastewater and a flue gas heat exchanger to recover waste heat from the waste flue gas.The combination of these two heat exchange methods in tantalum/niobium hydrometallurgy could recover waste heat and generate hot pure water above 70℃,effectively saving energy.