Slurry making is a critical step that can irrevocably affect the subsequent steps in battery manufacturing. Many experimental parameters, including the mixing sequence, must be considered in making the slurry. In this work, we investigated the effects of the two main industry-used mixing sequences on the rheological behavior of the slurry, and the relation of the slurry rheology to structural, mechanical, and electrochemical performance of LiNi 0.33 Mn 0.33 Co 0.33 O 2 (NMC) electrodes. We show that: (1) mixing carbon black (CB) with polyvinylidene fluoride (PVDF) solution before adding NMC can facilitate the formation of a gel-like slurry; (2) porous clusters of CB/PVDF can form around NMC after drying the gel-like slurry, providing a high C-rate capability;(3) dry powder mixing of CB and NMC can facilitate the binding of the CB to the NMC surfaces, reducing the amount of CB in the PVDF and resulting in a liquid-like slurry; (4) after drying of the liquid-like slurry, a dense CB/PVDF layer can form on the NMC surfaces; and (5) this dense layer can provide high binding strength but may block ionic transport and weaken the electronic connection, reducing the C-rate capability. Thus, it is critically important to understand the effects of mixing sequence in electrode manufacturing.

Zinc has the potential for widespread use as an environmentally friendly and cost‐effective anode material pending the resolution of rechargeability issues caused by active material loss and shape change. Here, a self‐assembled Nafion‐coated Celgard 3501 (NC‐Celgard) separator is shown to enable unprecedented cycle life of a Zn anode in alkaline electrolyte at high depth‐of‐discharge (DODZn). Using commercially relevant energy‐dense electrodes with high areal capacities of 60 mAh cm–2, Zn–Ni cells tested at 20% DODZn cells achieve over 200 cycles while 50% DODZn cells achieve over 100 cycles before failure. The 20% and 50% DOD cells deliver an average of 132 and 180 Wh L–1 per cycle over their lifetime respectively. Rechargeability is attributed to the highly selective diffusion properties of the 300 nm thick negatively charged Nafion coating on the separator which prevents shorting by dendrites and inhibits redistribution of the active material. Crossover experiments show that the NC‐Celgard separator is practically impermeable to zincate ([Zn(OH)4]2–), outperforming commercial Celgard, cellophane, Nafion 211 and 212 separators while still allowing hydroxide transport. This work demonstrates the efficacy of selective separators for increasing the cycle life of energy‐dense Zn electrodes without adding significant volume or complexity to the system.

The high interfacial resistance between solid electrolytes and lithium metal is a hurdle to developing all solid-state batteries. External pressure applied on the lithium and solid electrolyte interface prior to electrochemical cycling is known to effectively lower the interfacial resistance. Here we report that the interfacial resistance between Li6.4La3Zr1.4Ta0.6O12 (LLZTO) and lithium metal decreases over time even after removing the external pressure. The irreversible decrease of interfacial resistance can be understood by a gradual reduction of the total energy of the system, including strain energy and interfacial energy. Under external pressure exceeding ∼25 MPa, however, lithium can be squeezed into LLZTO, fracturing the ceramic solid electrolyte. These observations can help improve the understanding of lithium metal creep and the interactions between garnet-type solid electrolytes and lithium metal.

High performance Si/polyacrylonitrile (PAN) composite negative electrodes are fabricated by a robust process of oxidative pyrolysis at a temperature between 250 and 400°C. Multiple techniques are employed to investigate the structural, chemical, and mechanical properties of the Si/PAN composite electrodes before and after oxidative pyrolysis. With increasing temperature, oxidation, dehydration, aromatization, and intermolecular crosslinking take place in PAN, resulting in a stable cyclized structure which functions as both a binder and a conductive agent in the Si/PAN composite electrodes. Meanwhile, PAN reacts with oxygen, forming volatile products and producing progressively porous Si/PAN composites with increasing temperature. With a Si mass loading of 1 mg/cm 2 , a discharge capacity of 1555 mAh/g at the 100 th cycle is observed from the 400°C treated Si/PAN composite electrode when cycled at a rate of C/3. This 400°C treated electrode also shows good rate capability. It exhibits a specific discharge capacity of ∼500 mAh/g at 3C compared to the nearly zero capacity for those treated at lower temperatures. This facile method of synthesizing Si-based composite negative electrodes can potentially be applied to other Si/polymer systems for further increasing the power/energy density of lithium ion batteries.

We have investigated the surface of lithium metal using x-ray photoemission spectroscopy and optical spectroscopic ellipsometry. Even if we prepare the surface of lithium metal rigorously by chemical cleaning and mechanical polishing inside a glovebox, both spectroscopic investigations show the existence of a few tens of nanometer-thick surface layers, consisting of lithium oxides and lithium carbonates. When lithium metal is exposed to room air (∼50% moisture), in situ real-time monitoring of optical spectra indicates that the surface layer grows at a rate of approximately 24 nm/min, presumably driven by an interface-controlled process. Our results hint that surface-layer-free lithium metals are formidable to achieve by a simple cleaning/polishing method, suggesting that the initial interface between lithium metal electrodes and solid-state electrolytes in fabricated lithium metal batteries can differ from an ideal lithium/electrolyte contact.