Liquid-free all-solid-state lithium metal batteries (ASSLMBs) are promising candidates to meet the requirements of safety and high energy density for energy storages. However, poor interfacial contact is a major obstacle limiting their applications. Herein, we report a solid polymer electrolyte (SPE), originally prepared by stereolithography (SLA) three-dimensional (3D) printing for ASSLMBs. A 3D-Archimedean spiral structured SPE is rationally designed, which can shorten the Li-ion transport pathway from the electrolyte into the electrode, reinforce the interfacial adhesion, and improve the mass loading of active materials. The SLA printed SPE exhibits a high ionic conductivity of 3.7 × 10 −4 S cm −1 at 25 °C. Furthermore, Li|3D-SPE|LFP cells achieve reduced interfacial impedance and higher specific capacity of 128 mAh g −1 after 250 cycles than those using structure-free SPE of 32 mAh g −1 . This work opens the great promise of SLA 3D printing technology to fabricate high-performance SPEs in ASSLMBs for next-generation energy storages.

Rechargeable batteries that combine high energy density with high power density are highly demanded. However, the wide utilization of lithium metal anode is limited by the uncontrollable dendrite growth, and the conventional lithium-ion batteries (LIBs) commonly suffer from low rate capability. Here, we for the first time develop a biofilm-coated separator for high-energy and high-power batteries. It reveals that the coating of Escherichia coli protein nanofibers can improve electrolyte wettability and lithium transference number and enhance adhesion between separators and electrodes. Thus, lithium dendrite growth is impeded because of the uniform distribution of the Li-ion flux. The modified separator also enables the stable cycling of high-voltage Li|Li1.2Mn0.6Ni0.2O2 (LNMO) cells at an extremely high rate of 20 C, delivering a high specific capacity of 83.1 mA h g–1, which exceeds the conventional counterpart. In addition, the modified separator in the Li4Ti5O12|LNMO full cell also exhibits a larger capacity of 68.2 mA h g–1 at 10 C than the uncoated separator of 37.4 mA h g–1. Such remarkable performances of the modified separators arise from the conformal, adhesive, and endurable coating of biofilm nanofibers. Our work opens up a new opportunity for protein-based biomaterials in practical application of high-energy and high-power batteries.

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Lithium-rich layered oxide cathodes with high specific energy have become one of the most popular cathode materials for high-performance lithium-ion batteries. However, spinel phase formation due to the migration of transition metals and the release of lattice oxygen leads to the degradation of electrochemical performance. Here, we develop a synthesis approach for Li-rich layered oxide cathodes by a two-step heat-treatment process, which includes precursor calcination and pellet sintering. Compared with the sample prepared by the traditional one-step calcination, the oxide particles prepared by the two-step heat treatment show increased grain size from 217 to 425 nm. The Li-rich layered oxide cathodes with larger crystal grains indicate a mitigated formation of spinel phase and reduced voltage decay, which result in improved specific capacity, cycle stability, and rate capability. In addition, the thermal stability of the oxides is also improved. The improved electrochemical performance is because of the large single grains having a reduced contact area with a liquid electrolyte and the stable crystal lattice during cycling. Our strategy not only provides a simple and effective way to enhance the stability of the Li-rich layered oxide cathodes but also extends to the preparation of oxide powders with large grains.

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