Carbon-free Mn-doped LiFePO₄ cathode for highly transparent thin-film batteries

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>The search for transparent battery cathodes primarily focuses on patterned electrodes with feature sizes below the optical absorption limit. This significantly limits the electrode capacity, as a large electrode area remains unused to maintain transparency. Herein, we report transparent olivine LiFe<SUB>0.77</SUB>Mn<SUB>0.23</SUB>PO<SUB>4</SUB> thin-film electrodes discovered through high-throughput continuous-composition-spread sputtering. After investigating six different Mn doping ratios, we found the optimal Mn-doped olivine composition with an enhanced discharge capacity of 45.7 μA h/cm<SUP>2</SUP>∙μm without using excessive nanosized features or carbon coating. The thin-film electrode exhibits a clear redox activity for both Fe<SUP>3+/2+</SUP> and Mn<SUP>3+/2+</SUP>, resulting in an enhanced average voltage over LiFePO<SUB>4</SUB> composition. A 250-nm-thick film exhibits an optical transmittance of over 80% in the visible region. The results in this study demonstrates that transparent cathode thin films can be developed based on phospho-olivines via doping strategies with high-throughput continuous-composition-spread sputtering methods.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Exploration of carbon-free transparent LiFe<SUB>1-<I>x</I> </SUB>Mn<SUB> <I>x</I> </SUB>PO<SUB>4</SUB> thin films by CCS. </LI> <LI> The capacity of carbon-free LiFe<SUB>0.77</SUB>Mn<SUB>0.23</SUB>PO<SUB>4</SUB> thin films is 45.7 μA h/cm<SUP>2</SUP>∙μm. </LI> <LI> Transmittance of Carbon-free LiFe<SUB>0.77</SUB>Mn<SUB>0.23</SUB>PO<SUB>4</SUB> thin film exhibits 82%. </LI> <LI> Carbon-free LiFe<SUB>0.77</SUB>Mn<SUB>0.23</SUB>PO<SUB>4</SUB> is suitable for transparent thin film batteries. </LI> </UL> </P>