Abstract: Ionic thermoelectric materials show considerable potential in the field of low-grade heat recovery, yet how to synergistically enhance their Seebeck coefficient and ionic conductivity remains a key challenge. In this study, natural balsa wood was used as the raw material to construct a three-dimensional porous cellulose framework via chemical delignification. A series of high-performance lignocellulose-based ionic thermoelectric gels were prepared by loading composite gels of polyvinyl alcohol (PVA) and different electrolytes (sodium chloride, potassium chloride, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium acetate, i.e., NaCl, KCl, BMIMCl, BMIMAc) into the framework using vacuum impregnation technology. The effects of electrolyte type and concentration on ion transport and thermoelectric performance were systematically investigated. The results indicate that the ionic liquid system, leveraging the synergistic effect of cation steric hindrance and anion coordination, significantly amplifies the difference in cation and anion migration. Among all samples, the 8% BMIMAc/PVA sample exhibited the best comprehensive performance, with an ionic conductivity of 5.33 mS/cm and a high Seebeck coefficient of 23 mV/K (ΔT = 3 K), which is approximately eight times higher than that of the inorganic salt system at the same concentration. This study proposes a new mechanism for optimizing ionic thermoelectric performance through the synergistic design of matrix structure and electrolyte, offering new insights for the development of high-performance and sustainable biomass-based thermoelectric materials.