We report that a solid‐state battery architecture enables the reversible, four electron storage of fully utilized solvothermally synthesized cubic‐FeS2 (pyrite). With a sulfide based glass electrolyte we successfully confine electro‐active species and permit the safe use of a lithium metal anode. These FeS2/Li solid‐state cells deliver a theoretical specific capacity of 894 mAh g−1 at 60 °C. We find that nanoparticles of orthorhombic‐FeS2 (marcasite) are generated upon recharge at 30–60 °C which explains a coincident change in rate kinetics.

Cycle stability of solid-state lithium batteries (SSLBs) using a LiCoO 2 cathode is improved by atomic layer deposition (ALD) on active material powder with Al 2 O 3 . SSLBs with LiCoO 2 /Li 3.15 Ge 0.15 P 0.85 S 4 /77.5Li 2 S-22.5P 2 S 5 /Li structure were constructed and tested by charge-discharge cycling at a current density of 45 μA cm −2 with a voltage window of 3.3 ∼ 4.3 V (vs. Li/Li + ). Capacity degradation during cycling is suppressed dramatically by employing Al 2 O 3 ALD-coated LiCoO 2 in the composite cathode. Whereas only 70% of capacity retention is achieved for uncoated LiCoO 2 after 25 cycles, 90% of capacity retention is observed for LiCoO 2 with ALD Al 2 O 3 layers. Electrochemical impedance spectroscopy (EIS) and transmission electron microscopy (TEM) studies show that the presence of ALD Al 2 O 3 layers on the surface of LiCoO 2 reduces interfacial resistance development between LiCoO 2 and solid state electrolyte (SSE) during cycling.

To deploy solid-state Li batteries in next-generation vehicles, it is essential to develop electrodes with durability, high energy and high power. Here we report on nanostructured composite cathode materials that enable solid-state Li batteries to cycle with durable high energy and high rate performance. Particle size of TiS 2 is reduced by planetary ball-milling to enhance performance of nanocomposite cathodes in solid-state Li batteries. The better utilization of active material and fast kinetics resulting from the size reduction of TiS 2 allow for highly reversible capacity in both room temperature and elevated temperature batteries. High power all-solid-state batteries have been constructed with nano-sized TiS 2 and demonstrated high power density over 1000 W kg −1 for over 50 cycles, with a maximum power density of ∼ 1400 W kg −1 . Galvanostatic intermittent titration technique and electrochemical impedance spectroscopy are employed in order to explain the extremely high rate capability of nanostructured TiS 2 nanocomposite.

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Polyacrylonitrile (PAN) was combined with elemental sulfur (S) using a facile procedure that produces a highly conductive and high capacity active material, PAN-S. PAN-S is shown in this work to be capable of extremely high energy density and good cycle stability in all-solid-state lithium batteries utilizing a sulfide based solid electrolyte. All-solid-state batteries employing PAN-S as active material maintained over 605 mAh g −1 for 50 cycles, and composite active materials containing less sulfur resulted in lower overall specific capacity but excellent cycle stability with less than 1% loss over 50 cycles. A high energy density of over 700 Wh kg −1 was achieved for all-solid-state lithium battery electrodes incorporating 57% active material into the cathode composite.

We report the direct observation of microstructural changes of LixSi electrode with lithium insertion. HRTEM experiments confirm that lithiated amorphous silicon forms a shell around a core made up of the unlithiated silicon and that fully lithiated silicon contains a large number of pores of which concentration increases toward the center of the particle. Chemomechanical modeling is employed in order to explain this mechanical degradation resulting from stresses in the LixSi particles with lithium insertion. Because lithiation‐induced volume expansion and pulverization are the key mechanical effects that plague the performance and lifetime of high‐capacity Si anodes in lithium‐ion batteries, our observations and chemomechanical simulation provide important mechanistic insight for the design of advanced battery materials.

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