Functionalization Of Nanocellulose And Its Application In Aqueous Zinc Batterie

Rechargeable aqueous zinc metal batteries（ZMBs）,featuring the advantages of high safety,low cost,and high volumetric energy density(5851 m Ah cm^-3),are indispensable parts of developing diversified energy storage technologies.However,due to the problems of corrosion,hydrogen evolution and dendrite growth,the reversibility of current aqueous ZMBs is still relatively low,and the cycle stability of ZMBs is poor.Most researchers pay more attention to the innovative design of electrode and electrolyte,but ignored the development and utilization of separators.In order to make up for the shortcoming in the development of water-based ZMBs,the separator,guided by the design concept of"salt fixed on an insoluble frame",This paper prepared a single-ion conductor functionalized nanocellulose membrane with excellent mechanical properties.It can effectively improve the reversibility of the battery,and then improve the cycle life of the battery.The specific results are as follows:（1）Taking pulp as raw material,after two-step reaction of sulfonation and ion replacement,the zinc nanocellulose sulfonate（CNF-SO₃Zn）is obtained.Then,the CNF-SO₃Zn film was obtained by suction filtration.Compared with the conventional separators commonly used in batteries,the CNF-SO₃Zn films have better basic electrochemical properties and physical advantages（i.e.,excellent mechanical properties,strong hydrophilicity,and uniform pore distribution）.Without additional addition of zinc salts,the CNF-SO₃Zn films can achieve high ionic conductivity greater than 5×10^-5 S cm^-1 by only absorbing a small amount of water（100 wt%of the dry weight of the separator）.And because the anions are fixed on the nanocellulose skeleton,the Zn²⁺ion migration number of the CNF-SO₃Zn film after water absorption is as high as 0.80.This design concept provides a new idea for the development of multifunctional battery separators,and promotes the application of cellulose nonafiber in the field of energy storage.（2）On the basis of the above work,this work further study the practical application of CNF-SO₃Zn films in aqueous ZMBs.The CNF-SO₃Zn film can significantly reduce the reactivity of water,effectively inhibit the corrosion of the zinc anode and side reactions such as hydrogen evolution,and the coulombic efficiency of the assembled Zn/Ti battery can reach99.5%.Second,the ZMBs assembled with the CNF-SO₃Zn film can perform large-capacity(8 m Ah cm^-2)and deep discharge(DOD_Zn=80%),which are crucial for the development of high-energy-density aqueous ZMBs.It is noted that the CNF-SO₃Zn separator can match a variety of cathodes commonly used in ZMBs（polyaniline,iodine,Prussian blue）,and show good cycle performance.Especially,the specific capacity in the as-assembled Zn/I₂ battery reaches 150 m Ah g^-1,and the capacity retention rate is 80%after 1000 cycles.Good cycling performance is also exhibited in large capacity（150 m Ah）pouch cells assembled with practical high-load polyaniline cathode(18 mg cm^-2).This work provides a simple and effective strategy for developing ZMBs with high energy density and good cycling stability.