Construction of greenly biodegradable bacterial cellulose/UiO-66-NH2 composite separators for efficient enhancing performance of lithium-ion battery

Abstract

The disposal of waste lithium batteries, especially waste separators, has always been a problem, incineration and burial will cause environmental pollution, therefore, the development of degradable and high-performance separators has become an important challenge. Herein, UiO-66-NH2 particles were successfully anchored onto bacterial cellulose (BC) separators by epichlorohydrin (ECH) as a crosslinker, then a BC/UiO-66-NH2 composite separator was prepared by vacuum filtration. The ammonia groups (−NH2) from UiO-66-NH2 can form hydrogen bonds with PF6− in the electrolyte, promoting lithium-ion transference. Additionally, UiO-66-NH2 can store the electrolyte and tune the porosity of the separator. The lithium ion migration number (0.62) of the battery assembled with BC/UiO-66-NH2 composite separator increased by 50 % compared to the battery assembled with commercial PP separator (0.45). The discharge specific capacity of the battery assembled with BC/UIO-66-NH2 composite separator after 50 charge and discharge cycles is 145.4 mAh/g, which is higher than the average discharge specific capacity of 114.3 mAh/g of the battery assembled with PP separator. When the current density is 2C, the minimum discharge capacity of the battery assembled with BC/UiO-66-NH2 composite separator is 85.3 mAh/g. The electrochemical performance of the BC/UiO-66-NH2 composite separator is significantly better than that of the commercial PP separator. In addition, -NH2 can offer a nitrogen source to facilitate degradation of the BC separators, whereby the BC/UiO-66-NH2 composite separator could be completely degraded in 15 days.