Molecule Engineering of Sugar Derivatives as Electrolyte Additives for Deep-Reversible Zn Metal Anode

The cycling performance of zinc-ion batteries is greatly affected by dendrite formation and side reactions on zinc anode, particularly in scenarios involving high depth of discharge (DOD) and low negative/positive capacity (N/P) ratios in full cells. Herein, drawing upon principles of host-guest interaction chemistry, we investigate the impact of molecular structure of electrolyte additives, specifically the -COOH and -OH groups, on the zinc negative electrode through molecular design. Our findings reveal that molecules containing these groups exhibit strong adsorption onto zinc anode surfaces and chelate with Zn²⁺, forming a H₂O-poor inner Helmholtz plane. This effectively suppresses side reactions and promotes dendrite-free zinc deposition of exposed (002) facets, enhancing stability and reversibility of an average coulombic efficiency of 99.89 % with the introduction of Lactobionic acid (LA) additive. Under harsh conditions of 92 % DOD, Zn//Zn cells exhibit stable cycling at challenging current densities of 15 mA ⋅ cm^-2. Even at a low N/P ratio of 1.3, Zn//NH₄V₄O₁₀ full cells with LA electrolyte exhibit high-capacity retention of 73 % after 300 cycles, significantly surpassing that of the blank electrolyte. Moreover, in a conversion type Zn//Br static battery with a high areal capacity (~5 mAh ⋅ cm^-2), LA electrolyte sustains an improved cycling stability of 700 cycles.