【作者】 刘鑫；

【导师】 张军；

【作者基本信息】 湖北大学 ， 电子科学与技术， 2023， 硕士

【摘要】 随着对储能体系的推进研究广泛研究,锂电以其高能量密度,长循环寿命脱颖而出,并很快进入商业领域应用。然而,锂资源在我国较为稀少导致其使用成本居高不下,同时电解液为有机电解液而存在较大的安全隐患。于是其它可替代的储能电池也就逐步走入人们的视线,其中锌离子电池因其资源丰富、成本较低、水系电解液的高安全性等优势得到越来越多的关注。然而锌离子电池正极材料在实际充/放电过程中的嵌入/脱出会导致材料体积膨胀,与此同时还会导致结构坍塌进而降低电池的能量密度。其中锰基正极材料,具备多种形貌和晶相,能够提供适中的电压窗口的同时还具备不俗的比容量,有着非常高的应用潜力,但在充放电过程中会伴随着歧化反应,这种反应会导致正极材料中的锰发生溶解,严重影响其循环稳定性,严重阻碍着锰基锌离子电池的进一步发展。本论文针对锰基材料因歧化反应而溶解导致锌离子电池稳定性差的问题,提出一种改善正极材料稳定性的简易工艺,即离子交换法掺杂改性。通过对锌离子电池二氧化锰正极材料进行掺杂改性,向二氧化锰中掺入过渡金属离子,改善二氧化锰的晶格稳定性。探究了微观形貌对二氧化锰性能的影响,同时提高了锌离子电池的电导率和稳定性,对掺杂改性提升比容量和稳定性的储能机理进行了探索分析。主要研究内容如下:1.通过一步水热法制备不同的二氧化锰前驱体粉末,再采用离子交换法对二氧化锰前驱体进行镍离子掺杂改性。通过控制变量法,探究前驱体、掺杂剂（种类、浓度）、离子交换环境（温度、时间）对离子交换工艺的影响,最终得到镍掺杂α相二氧化锰（Ni-Mn O₂）。通过一系列的电化学测试发现,离子交换法对Mn O₂进行掺杂改性,能够切实有效地提升Mn O₂的导电能力和循环稳定性。掺杂剂为0.15 mol/L的Ni（NO₃）₂,能够最大程度的提升改性效果,在0.2 A g^-1的电流密度下能够很快地完成活化过程,并稳定维持在206 m Ah g^-1的容量。而在1 A g^-1的稳定性测试中也表现极佳,在2800圈后容量保持率仍能维持在96.3%,相比之下,未经离子交换改性的Mn O₂,在130圈之后就已经下降到19.6%,切实有效的证明了离子交换工艺的有效性。2.探究了过渡金属的钴离子对Mn O₂进行离子交换改性的储能机理。先通过一步水热法制备Mn O₂前驱体,再进行离子交换进行Co离子掺杂改性。Co掺杂能提高Mn O₂的比容量,并在一定程度上提升正极材料的稳定性。同样通过控制变量,研究钴盐的种类、钴盐的浓度对Mn O₂的提升效果。其中掺杂剂为0.15 mol/L的Co SO₄,水热温度为190℃,水热时间为48 h时,能获得最佳的改性效果。在0.1 A g^-1电流密度下Co-Mn O₂比容量可达233 m Ah g^-1,在电流密度为1 A g^-1的循环测试中也是表现出了明显的稳定性提升,循环1400圈后仍有超过100 m Ah g^-1的比容量。通过实验证明了钴元素对α-Mn O₂进行离子交换改性的可行性。3.通过在聚碳酸脂模板上生长纳米管状δ-Mn O₂,分析了微观形貌对Mn O₂性能的影响。通过研究发现纳米管状的微观形貌能够在一定程度上提升Mn O₂的循环稳定性,为了进一步提升其性能,我们对纳米管状δ-Mn O₂进行了Ni离子交换。研究发现,离子交换法能切实有效地提升正极材料的稳定性和比容量,电流密度为1 A g^-1的循环条件下,循环1700圈后仍有着超过95%的容量保持率,相比未进行离子交换的δ-Mn O₂,稳定性有了极大的提升,证明了离子交换与微观形貌控制结合的可行性。综上所述,离子交换法是一种提高锰基锌离子电池正极材料性能的有效策略,通过离子交换对Mn O₂进行掺杂修饰,能够极大的提升Mn O₂的循环稳定性。本论文的相关研究为锌离子电池锰基正极材料的性能优化提供新的思路,为Zn-Mn O₂电池商业化应用奠定一定的实验与理论基础。更多还原

【Abstract】 With the extensive research on energy storage system,lithium electricity stands out for its high energy density and long cycle life,and soon enters the commercial field of application.However,lithium resources are relatively rare in our country,which leads to its cost being very high.Meanwhile,the electrolyte for organic electrolyte has great risks of safety.Therefore,other alternative energy storage batteries have gradually come into the attention of people,among which zinc ion batteries also get more and more attention due to its advantages of rich resources,low cost and high safety of water electrolyte.However,the insertion/removal of zinc ion battery cathode material during the actual charging/discharging process will lead to material volume expansion and structural collapse,thus reducing the energy density of the battery.Among them,although mangan-based cathode materials have various morphologies and crystal phases,which can provide moderate voltage window,but also have good specific capacity,and have very high application potential,it is accompanied by disproportionation reaction in the charging and discharging process,which will lead to the dissolution of manganese in the cathode materials,seriously affecting its cyclic stability.It seriously hinders the further development of manganese-based zinc ion batteries.In order to solve the problem of poor stability of zinc ion batteries caused by dissolving manganese based materials due to disproportionation reaction,a simple technology to improve the stability of positive electrode materials,namely ion exchange doping modification,was proposed in this paper.The lattice stability of manganese dioxide was improved by doping and modifying the cathode material of manganese dioxide for zinc ion batteries and adding transition metal ions into it.The influence of microstructure on the performance of manganese dioxide was investigated,and the conductivity,stability and battery life of zinc ion batteries were improved.The energy storage mechanism of doping modification to improve the stability was studied.The main research contents are as follows:1.Prepared different Mn O₂precursor powders by one step hydrothermal method,and the Mn O₂precursor was modified by Ni ion doping by ion exchange method.The influence of precursor,dopant（type and concentration）and ion exchange environment（temperature and time）on the ion exchange process was investigated by the control variable method,and nickel dopedα-phase manganese dioxide（Ni-Mn O₂）was finally obtained.Through a series of electrochemical tests,it is found that doping Mn O₂by ion exchange method can effectively improve the conductivity and cycling stability of Mn O₂.The dopant is 0.15 mol/L Ni（NO₃）₂,which can improve the modification effect to the greatest extent.The activation process can be completed quickly at the current density of 0.2 A g^-1,and the capacity of 206 m Ah g^-1can be maintained stably.In the stability test of 1 A g^-1,the capacity retention rate remained at96.3%after 2800 cycles,while the unmodified Mn O₂decreased to 19.6%after 130 cycles,which effectively proved the effectiveness of the ion exchange process.2.The energy storage mechanism of Mn O₂modified by transition metal cobalt ion was investigated.Mn O₂precursor was prepared by one-step hydrothermal method,and then Co ion doped modification was carried out by ion exchange.Co doping can increase the specific capacity of Mn O₂and improve the stability of the cathode material to a certain extent.Also,by controlling variables,the enhancement effect of cobalt salt type and cobalt salt concentration on Mn O₂was studied.When 0.15 mol/L Co SO₄was used as the dopant,the hydrothermal temperature was 190℃and the hydrothermal time was 48 h,the best modification effect could be obtained.At 0.1 A g^-1current density,the specific capacity of Co-Mn O₂can reach 233 m Ah g^-1.In the cycle test of 1 A g^-1,it also showed obvious stability improvement.After 1400 cycles,there is still more than 100 m Ah g-1 specific capacity.The feasibility of ion exchange modification ofα-Mn O₂by cobalt element was proved by experiments.3.The effect of nanotube-likeδ-Mn O₂morphology on the properties of Mn O₂was analyzed by growing nanotube-likeδ-Mn O₂on a polycarbonate template.It was found that the nanotube-like morphology can improve the cyclic stability of Mn O₂to a certain extent.In order to further improve its performance,Ni ion exchange was performed on the nanotube-likeδ-Mn O₂.It is found that the ion exchange method can effectively improve the stability and specific capacity of the anode material.Under the circulating condition of 1 A g^-1current density,the capacity retention rate is more than 95%after 1700 cycles.Compared with theδ-Mn O₂without ion exchange,the stability has been greatly improved.The combination of ion exchange and morphology control is feasible.In conclusion,the ion exchange method is an effective strategy to improve the properties of positive electrode materials for Mangan-based zinc ion batteries.The doping modification of Mn O₂by ion exchange can greatly improve the cyclic stability of Mn O₂.The relevant research in this paper provides a new idea for the performance optimization of manganese based cathode materials for zinc ion batteries,and lays a certain experimental and theoretical foundation for the commercial application of Zn-MnO₂ batteries.更多还原