【作者】 李欣；

【导师】 张乃庆；

【作者基本信息】 哈尔滨工业大学 ， 化学工程， 2021， 硕士

【摘要】 以金属锌为负极的水系锌离子电池因其在成本、安全性及无毒性等方面的优势,可作为锂离子电池储能设备的替代体系。然而,由于锌枝晶的不可控生长、腐蚀及析氢副反应的发生,导致金属锌负极循环寿命短且可逆性差,从而限制水系锌离子电池的进一步发展。目前,科研工作者已开发了一些抑制锌枝晶生长和改善锌负极循环性能的方法,大部分工作集中于电解质及电极的改性,但仍存在工艺复杂、成本高等问题。隔膜作为电池的组成部分之一,可调节离子传输,影响电池的电化学性能,因此可从提升隔膜性能出发,抑制锌枝晶生长,提高锌负极寿命和可逆性。以价廉、环境友好和可再生的细菌纤维素作为隔膜原料,通过造纸法制备了厚度为9μm的细菌纤维素膜,其拉伸强度达120 MPa。以细菌纤维素隔膜组装的锌对称电池在0.5 m A cm^-2,0.1 m Ah cm^-2下,可稳定循环超过4000 h,且在高电流密度下(2 m A cm^-2,1 m Ah cm^-2),可稳定充放电循环400 h以上,相比于目前广泛使用的玻璃纤维隔膜,循环稳定性得到明显提升。此外,以细菌纤维素隔膜组装的Zn||Mn O₂电池在1 C倍率下,100圈循环后的可逆容量为171.7 m Ah g^-1,对应的容量保持率达92.6%。在上述研究工作基础上,通过2,2,6,6-四甲基哌啶-1-氧自由基氧化体系氧化制备了羧基化的细菌纤维素,并将其与细菌纤维素混合,制得负电荷改性的细菌纤维素混合膜。该混合膜通过-COO^-基团与Zn²⁺相互作用,调控Zn²⁺传输行为,促进锌负极表面Zn²⁺的均匀分布与沉积,从而提高锌负极寿命。该混合膜组装的Zn||Zn对称电池在2 m A cm^-2,1 m Ah cm^-2下,可稳定循环超过550 h。且在2 m A cm^-2下,锌-碳不对称电池在200圈循环后的平均库伦效率达98.1%,具有高锌沉积/溶解可逆性。此外,以混合膜组装的Zn||Mn O₂电池在1 C下循环100圈后的放电比容量为222.5 m Ah g^-1,对应容量保持率达97.5%。更多还原

【Abstract】 Aqueous zinc ion batteries with zinc metal anodes can be used as an alternative system for energy storage equipment of lithium-ion batteries due to its advantages in cost,safety and non-toxicity.However,due to the uncontrollable growth of zinc dendrites,corrosion and the occurrence of hydrogen evolution side reaction,the metal zinc anodes have a short cycle life and poor reversibility,thereby limiting the further development of aqueous zinc ion batteries.At present,researchers have developed some methods to inhibit the growth of zinc dendrites and improve the cycle performance of zinc anodes.Most of the work focused on the modification of electrolytes and electrodes,but there are still problems such as complex processes and high cost.As an important part of the battery,the separator can regulate ion transmission and affect the electrochemical performance of the battery.Therefore,improving the performance of the separators also can inhibit the growth of zinc dendrites,improve the life and reversibility of the zinc anode.Using cheap,environmentally friendly and renewable bacterial cellulose as the raw material for the membrane,a bacterial cellulose membrane with a thickness of 9μm was prepared by papermaking method,and its yield strength is up to 120 MPa.Zinc symmetric battery assembled with bacterial cellulose membrane can be cycled stably for more than4000 h under 0.5 m A cm^-2,0.1 m Ah cm^-2,and at high current density(2 m A cm^-2,1 m Ah cm^-2),it can stable cycle for more than 400 h.Compared with the widely used glass fiber separator,the cycle stability has been significantly improved.In addition,the Zn||Mn O₂battery assembled with bacterial cellulose membrane has a reversible capacity of 171.7m Ah g^-1 after 100 cycles at a rate of 1 C,and the corresponding capacity retention rate is92.6%.On the basis of the above research work,carboxylated bacterial cellulose was prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl radical oxidation system.And it was mixed with bacterial cellulose to prepare mixed bacterial cellulose membrane with negative charge modification.The mixed membrane interacts with Zn²⁺through the-COO^-group,regulates the transmission behavior of Zn²⁺,promotes the uniform distribution and deposition of Zn²⁺on the surface of zinc anode,thereby improving the life of the zinc anode.The Zn||Zn symmetric battery assembled by the mixed membrane can cycle stably for more than 550 h at 2 m A cm^-2,1 m Ah cm^-2.At 2 m A cm^-2,the average Coulomb efficiency of the zinc-carbon asymmetric cell is up to 98.1%after 200 cycles,showing high zinc deposition/dissolution reversibility.In addition,the specific discharge capacity of the Zn||Mn O₂ battery assembled with the mixed membrane is 222.5 m Ah g^-1after 100 cycles at 1 C,which corresponds to a capacity retention rate of 97.5%.更多还原