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对固态二氧化硅在850℃氯化钙熔盐中的伏安行为分析的基础上,通过系统研究了二氧化硅粉末压片在850℃氯化钙熔盐中恒电位电解产物的物相和纯度,确定了通过熔盐电解法制备单质硅的电位范围.实验结果表明,熔盐电解二氧化硅制备单质硅合适的电解电位范围为0.65V（vs.Ca/Ca2＋）至1.15V.通过在此电位范围内恒电位电解产物纯度和能量效率分析,明确了熔盐电解制备单质硅最优化的电解电位为0.85V,此时电解产物纯度高达99.41%,电流效率为79.3%,电解能耗为11.5kWh/kg Si.上述结果表明,熔盐电解法制备单质硅与传统碳热还原法相比在能量效率和产物纯度上具有优势.通过电解产物杂质来源的分析,提出进一步提高产物纯度以达到太阳能级硅要求的措施,为通过熔盐电解法直接制备太阳能级硅提供了科学基础.“,”Together with voltammetric analysis of solid silica electrode in molten CaCl2 at 850 ℃,crystal phase and purity of the electrolytic products generated from potentiostatic electrolysis of porous silica in molten CaCl2 at 850 ℃ are investigated,which specifies that the proper electrolysis potential towards silicon production via molten-salt electrolysis falls in a range between 0.65 V(vs.Ca/Ca2+)and 1.15 V.Based on purity and energy efficiency of potentiostatic electrolysis,the optimal electrolysis potential is determined to be 0.85 V.Upon potentiostatic electrolysis at this optimal potential,the purity of electrolytic sample,current efficiency and energy consumption are calculated to be 99.41 wt%,79.3% and 11.5 kWh/kg Si,respectively.The merits of molten-salt electrolysis method over traditional carbothermic-reduction route for silicon production are therefore highlighted in terms of energy efficiency and purity of products.The origins of impurities in electrolytic silicon are also discussed,which not only gives hints on further improving purity to solar grade,but also forms the scientific grounds of direct preparation of solar-grade silicon via molten-salt electrolysis.