Hybrid solid electrolytes, composed of 3D ordered bicontinuous conducting ceramic and insulating polymer microchannels are reported. The ceramic channels provide continuous, uninterrupted pathways, maintaining high ionic conductivity between the electrodes, while the polymer channels permit improvement of the mechanical properties from that of the ceramic alone, in particular mitigation of the ceramic brittleness. The conductivity of a ceramic electrolyte is usually limited by resistance at the grain boundaries, necessitating dense ceramics. The conductivity of the 3D ordered hybrid is reduced by only the volume fraction occupied by the ceramic, demonstrating that the ceramic channels can be sintered to high density similar to a dense ceramic disk. The hybrid electrolytes are demonstrated using the ceramic lithium ion conductor Li_1.4Al_0.4Ge_1.6(PO₄)₃ (LAGP). Structured LAGP 3D scaffolds with empty channels were prepared by negative replication of a 3D printed polymer template. Filling the empty channels with non-conducting polypropylene (PP) or epoxy polymer (epoxy) creates the structured hybrid electrolytes with 3D bicontinuous ceramic and polymer microchannels. Printed templating permits precise control of the ceramic to polymer ratio and the microarchitecture; as demonstrated by the formation of cubic, gyroidal, diamond and spinodal (bijel) structures. The electrical and mechanical properties depend on the microarchitecture, the gyroid filled with epoxy giving the best combination of conductivity and mechanical properties. An ionic conductivity of 1.6 × 10⁻⁴ S cm⁻¹ at room temperature was obtained, reduced from the conductivity of a sintered LAGP pellet only by the volume fraction occupied by the ceramic. The mechanical properties of the gyroid LAGP–epoxy electrolyte demonstrate up to 28% higher compressive failure strain and up to five times the flexural failure strain of a LAGP pellet before rupture. Notably, this demonstrates that ordered ceramic and polymer hybrid electrolytes can have superior mechanical properties without significantly compromising ionic conductivity, which addresses one of the key challenges for all-solid-state batteries.

In the search for active Lithium-ion battery materials with ever-increasing energy density, the limits of conventional auxiliary materials, such as binders and conducting additives are being tested. Binders adhere to active substances and current collectors, yielding an interconnected electrode structure that ensures mechanical integrity during the (de-)lithiation process. Even though the battery binder only accounts for a fraction of battery weight and cost, it is a bottleneck technology in the deployment of high energy density active materials that experience significant volume variation and side-reactions. This review paper discusses research on alternative binders derived from conducting polymers (CPs). The use of CPs in binders enables mechanically flexible electronic contacts with the active material with the goal of accommodating larger volume changes within the electrode. Following a summary of the reasoning behind the use of CP-based binders, their rational design is reviewed, including novel composite syntheses and chemical modifications. A new class of multifunctional CP-based binders exhibits promising properties such as high electronic conductivity, the ability for aqueous processing, and efficient binding that tackle the limiting features of traditional binders. The practical application of these binders in Li-ion batteries and beyond is summarized, yielding an outline of current achievements, and a discussion of remaining knowledge gaps and possible future development of such binders.

Lithium‐rich transition metal cathodes can deliver higher capacities than stoichiometric materials by exploiting redox reactions on oxygen. However, oxidation of O²⁻ on charging often results in loss of oxygen from the lattice. In the case of Li₂MnO₃ all the capacity arises from oxygen loss, whereas doping with Ni and/or Co leads to the archetypal O‐redox cathodes Li[Li_0.2Ni_0.2Mn_0.6]O₂ and Li[Li_0.2Ni_0.13Co_0.13Mn_0.54]O₂, which exhibit much reduced oxygen loss. Understanding the factors that determine the degree of reversible O‐redox versus irreversible O‐loss is important if Li‐rich cathodes are to be exploited in next generation lithium‐ion batteries. Here it is shown that the almost complete eradication of O‐loss with Ni substitution is due to the presence of a less Li‐rich, more Ni‐rich (nearer stoichiometric) rocksalt shell at the surface of the particles compared with the bulk, which acts as a self‐protecting layer against O‐loss. In the case of Ni and Co co‐substitution, a thinner rocksalt shell forms, and the O‐loss is more abundant. In contrast, Co doping does not result in a surface shell yet it still suppresses O‐loss, although less so than Ni and Ni/Co doping, indicating that doping without shell formation is effective and that two mechanisms exist for O‐loss suppression.