Ferroelectric Nanorods as a Polymer Interface Additive for High-Performance Garnet-Based Solid-State Batteries

Sandwiching polymer interlayers between the electrodeand solidelectrolyte is considered promising in solving the interfacial issuesarising from solid-solid contact in garnet-based solid-statebatteries, but drawbacks including low ionic conductivity, inferiorLi(+) transference number, and unsatisfying mechanical propertyof the polymer hindered the practical application of such strategy.To solve the mentioned shortcomings of the polymer interlayer simultaneously,we introduce the ferroelectric material, BaTi2O5 (BT) nanorods, into the polymer matrix in this work. By taking fulladvantage of the plasticization effect and intrinsic spontaneous polarizationof the introduced ferroelectric, the polymer's ionic conductivityand Li+ transference number have been significantly enhanced.The built-in electric field BT introduced also benefits the modulationof CEI components formed on the cathode particles, further enhancingthe battery performance by decreasing cathode degradation. Besides,the BT nanorods' particular high aspect ratio also helps increasethe mechanical property of the obtained polymer film, making it moreresistant to lithium dendrite growth across the interface. Benefittingfrom the merits mentioned above, the assembled lithium symmetric cellsusing garnet SE with the BT-modified polymer interlayer exhibit stablecycling performance (no short circuit after 1000 h under RT) withlow polarization voltage. The full battery employing LiFePO4 as a cathode also presents superior capacity retentions (94.6% after200 cycles at 0.1 C and 93.4% after 400 cycles at 0.2 C). This workhighlights the importance of ferroelectric materials with specificmorphology in enhancing the electrochemical performance of polymer-basedelectrolytes, promoting the practical application of solid-state batteries.