Abstract

The synthesis, processing, and performance of a low‐cost monolithic battery electrode, produced entirely of natural and renewable resources, are reported. This anode material exhibits tunable electrochemical performance suitable for both high power and high energy applications. A synthesis method that directly results in electrically interconnected three‐dimensional architectures is presented, where the carbon framework functions as current collector and lithium insertion material, eliminating the extra mass and expense of inactive materials in conventional designs. Fibrous carbon electrode materials are produced from solvent extracted lignin using scalable melt processing technology and thermal conversion methods. The resulting free‐standing electrodes exhibit comparable electrochemical performance to commercial carbon‐based anodes at a fraction of the materials and processing costs. Compositional and electrochemical characterization shows that carbonized lignin has a disordered nano‐crystalline microstructure. The carbonized mats cycle reversibly in conventional aprotic organic electrolytes with Coulombic efficiencies over 99.9%. Moreover, lignin carbon fibers carbonized at 2000 °C can cycle reversibly in 1 m LiPF6 in propylene carbonate.

Additive manufacturing allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) - to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm3, and the room temperature magnetic properties are: intrinsic coercivity Hci = 688.4 kA/m, remanence Br = 0.51 T, and energy product (BH)max = 43.49 kJ/m3 (5.47 MGOe). In addition, tensile tests performed on four dog-bone shaped specimens yielded an average ultimate tensile strength of 6.60 MPa and an average failure strain of 4.18%. Scanning electron microscopy images of the fracture surfaces indicate that the failure is primarily related to the debonding of the magnetic particles from the polymer binder. The present method significantly simplifies manufacturing of near-net-shape bonded magnets, enables efficient use of rare earth elements thus contributing towards enriching the supply of critical materials.

Functional polymers are intelligent materials that can respond to a variety of external stimuli. However, these materials have not yet found widespread real world applications because of the difficulties in fabrication and the limited number of functional building blocks that can be incorporated into a material. Here, we demonstrate a simple route to incorporate three functional building blocks (azobenzene chromophores, liquid crystals, and dynamic covalent bonds) into an epoxy-based liquid crystalline network (LCN), in which an azobenzene-based epoxy monomer is polymerized with an aliphatic dicarboxylic acid to create exchangeable ester bonds that can be thermally activated. All three functional building blocks exhibited good compatibility, and the resulting materials exhibits various photomechanical, shape memory, and self-healing properties because of the azobenzene molecules, liquid crystals, and dynamic ester bonds, respectively.

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