A Bioinspired Piezoelectric Stress Buffer Layer for SiO_x-Based Electrodes Toward High-Energy Lithium Batteries

High-specific-capacity silicon suboxide (SiO_x, 0 < x < 2) anodes have long faced the problems of huge volume expansion, fast capacity decay and unsatisfied rate performance. To overcome these bottlenecks, the volume expansion resistance and electrogenic Na⁺ transport functions of common rain frog (Breviceps adspersus) epidermis are introduced into the design philosophy of stress buffers for SiO_x electrodes. Thereupon, a mechanically robust, piezoelectric (MP) stress buffer layer comprised of ferroelectric tetragonal BaTiO₃ nanoparticles and a novel homopolymer (PCM) binder of cyanoethyl carbamate-containing methacrylate is developed. It is demonstrated that MP stress buffer layer with superior mechanical properties effectively inhibits excessive volume expansion and stabilizes the solid electrolyte interface along with much suppressed electrolyte decomposition. Meanwhile, MP stress buffer layer helps expedite the dealloying reaction kinetics of SiO_x electrodes in half-cells, mainly owing to the generation of a stress-induced built-in electric field within MP stress buffer layer, conducive to improving battery rate performance. As a result, unprecedented cycling and rate performance can be realized in coin and home-made soft package cells with SiO_x and SiO_x/graphite composite electrodes. Such a design philosophy of stress buffer layers marks an important milestone in developing high-energy lithium batteries with SiO_x-based anodes.