Bottom‐Up Design of a Green and Transient Zinc‐Ion Battery with Ultralong Lifespan

Abstract

implementation of widespread approaches for renewable energy generation, [1] and mass-scale adoption of electric vehicles. [2] Such a green transition is only possible if efficient and environmentally friendly energy storage systems are developed. [1][2][3] As the most prominent and versatile energy storage system, batteries are anticipated to be the vital cog for the storage/ delivery of on-demand power in an environmentally and socioeconomically sustainable manner. [4] Ideally, a sustainable energy storage device should deliver large capacities, present good rate capability, have long operating lifespans, and, most importantly, rely on nontoxic and noncritical materials. [5][6][7] These stringent requirements displace lithium ion batteries (LIBs) as the preferred choice for truly green batteries. [5] Current LIBs use toxic and flammable chemicals in the electrolyte (lithium hexafluorophosphate, carbonate esters) and elements listed by the European Union as critical raw materials (CRMs), including cobalt, lithium, or graphite. [8,9] Besides their high supply risk with primary resources in Bolivia, Argentina, Chile, Australia, and the Democratic Republic of Congo, the disposal and subsequent marine/ landfill accumulation of CRMs seriously threaten animal and Transient batteries are expected to lessen the inherent environmental impact of traditional batteries that rely on toxic and critical raw materials. This work presents the bottom-up design of a fully transient Zn-ion battery (ZIB) made of nontoxic and earth-abundant elements, including a novel hydrogel electrolyte prepared by cross-linking agarose and carboxymethyl cellulose. Facilitated by a high ionic conductivity and a high positive zinc-ion species transference number, the optimized hydrogel electrolyte enables stable cycling of the Zn anode with a lifespan extending over 8500 h for 0.25 mA cm −2 -0.25 mAh cm −2 . On pairing with a biocompatible organic polydopamine-based cathode, the full cell ZIB delivers a capacity of 196 mAh g −1 after 1000 cycles at a current density of 0.5 A g −1 and a capacity of 110 mAh g −1 after 10 000 cycles at a current density of 1 A g −1 . A transient ZIB with a biodegradable agarose casing displays an open circuit voltage of 1.123 V and provides a specific capacity of 157 mAh g −1 after 200 cycles at a current density of 50 mA g −1 . After completing its service life, the battery can disintegrate under composting conditions.

Lignin–Chitosan Gel Polymer Electrolytes for Stable Zn Electrodeposition

“…In any case, it is important to note that the low overpotential obtained by the LS,Chi 30/70 GPE enables a high voltage efficiency of the battery, delaying undesired decomposition reactions that may yield to a premature cell failure or inefficient charge/discharge . It is worthy to note that the observed overpotential value for LS30Chi70 GPE is similar to that shown by a cellulose–agarose GPE recently developed by our group, which offers a lifespan extending over 8500 h (one year cycling) in a symmetric Zn|Zn configuration . In fact, we postulate that developed lignin-based GPEs suppress the presence of free water as opposed to conventional membrane/aqueous electrolyte systems, shielding Zn surfaces from the free water-induced Zn corrosion and thus enabling long-term cycling .…”

“…When lignin–chitosan GPEs are paired with organic cathode materials, fully renewable ZIBs could be obtained, avoiding the use of scarce and toxic critical raw materials that are causing serious resource depletion and supply chain bottleneck issues . Additionally, the biodegradable character of electrolyte constituents makes these GPEs susceptible to degrade under composting conditions, opening new opportunities to fabricate transient rechargeable batteries that are rapidly degraded into harmless by-products (once the adequate trigger is activated) after a period of stable operation . Thereby, lignin–chitosan GPEs have the potential to lessen the inherent environmental impact of conventional LIBs requiring non-biodegradable and harmful materials.…”

“…74 In any case, it is important to note that the low overpotential obtained by the LS,Chi 30/70 GPE enables a high voltage efficiency of the battery, delaying undesired decomposition reactions that may yield to a premature cell failure or inefficient charge/ 74 It is worthy to note that the observed overpotential value for LS30Chi70 GPE is similar to that shown by a cellulose−agarose GPE recently developed by our group, which offers a lifespan extending over 8500 h (one year cycling) in a symmetric Zn|Zn configuration. 23 In fact, we postulate that developed lignin-based GPEs suppress the presence of free water as opposed to conventional membrane/ aqueous electrolyte systems, shielding Zn surfaces from the free water-induced Zn corrosion and thus enabling long-term cycling. 32 Noting this composition presents the lower Young's modulus (55 ± 4 MPa), it can be concluded that achieving a good interfacial compatibility and intimate contact of the GPEs with the metallic Zn (also promoted by the hydroxyl and ether Considering the functional properties and their renewable/ biodegradable nature, we envisage the following potential applications for fabricated lignin-containing GPEs.…”

“…79 Additionally, the biodegradable character of electrolyte constituents makes these GPEs susceptible to degrade under composting conditions, opening new opportunities to fabricate transient rechargeable batteries that are rapidly degraded into harmless by-products (once the adequate trigger is activated) after a period of stable operation. 23 Thereby, lignin−chitosan GPEs have the potential to lessen the inherent environmental impact of conventional LIBs requiring non-biodegradable and harmful materials.…”

“…Underutilized biorefinery wastes offer plenty of materials with abundant functional groups and tailored properties to be exploited as battery electrolytes. So far, most of the efforts to develop Zn 2+ conducting materials have been directed toward the use of celluloses, agarose, or chitosan . Among the bio-based materials not yet fully exploited, lignin is particularly attractive given its aromatic structure and abundant production as a by-product from industrial biomass processing .…”