Preparation And Modification Of Bacterial Cellulose Membrane For High Performance Aqueous Zinc Ion Batteries

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%.