Advanced parametrization for the production of high-energy solid-state lithium pouch cells containing polymer electrolytes.

Lithium batteries with solid-state electrolytes are an appealing alternative to state-of-the-art non-aqueous lithium-ion batteries with liquid electrolytes because of safety and energy aspects. However, engineering development at the cell level for lithium batteries with solid-state electrolytes is limited. Here, to advance this aspect and produce high-energy lithium cells, we introduce a cell design based on advanced parametrization of microstructural and architectural parameters of electrode and electrolyte components. To validate the cell design proposed, we assemble and test (applying a stack pressure of 3.74 MPa at 45 °C) 10-layer and 4-layer solid-state lithium pouch cells with a solid polymer electrolyte, resulting in an initial specific energy of 280 Wh kg-1 (corresponding to an energy density of 600 Wh L-1) and 310 Wh kg-1 (corresponding to an energy density of 650 Wh L-1) respectively.

Charge-clustering induced fast ion conduction in 2LiX-GaF3: A strategy for electrolyte design.

2LiX-GaF3 (X = Cl, Br, I) electrolytes offer favorable features for solid-state batteries: mechanical pliability and high conductivities. However, understanding the origin of fast ion transport in 2LiX-GaF3 has been challenging. The ionic conductivity order of 2LiCl-GaF3 (3.20 mS/cm) > 2LiBr-GaF3 (0.84 mS/cm) > 2LiI-GaF3 (0.03 mS/cm) contradicts binary LiCl (10-12 S/cm) < LiBr (10-10 S/cm) < LiI (10-7 S/cm). Using multinuclear 7Li, 71Ga, 19F solid-state nuclear magnetic resonance and density functional theory simulations, we found that Ga(F,X)n polyanions boost Li+-ion transport by weakening Li+-X- interactions via charge clustering. In 2LiBr-GaF3 and 2LiI-GaF3, Ga-X coordination is reduced with decreased F participation, compared to 2LiCl-GaF3. These insights will inform electrolyte design based on charge clustering, applicable to various ion conductors. This strategy could prove effective for producing highly conductive multivalent cation conductors such as Ca2+ and Mg2+, as charge clustering of carboxylates in proteins is found to decrease their binding to Ca2+ and Mg2+.

Prussian Blue-Type Sodium-ion Conducting Solid Electrolytes for All Solid-State Batteries.

Conventional solid electrolyte frameworks typically consist of anions such as sulphur, oxygen, chlorine, and others, leading to inherent limitations in their properties. Despite the emergence of sulphide, oxide, and halide-based solid electrolytes for all-solid-state batteries, their utilization is hampered by issues, including the evolution of H2 S gas, the need for expensive elements, and poor contact. Here, we first introduce Prussian Blue analogue (PBA) open-framework structures as a solid electrolyte that demonstrates appreciable Na+ conductivity (>10-2 mS cm-1 ). We delve into the relationship between Na+ conductivity and the lattice parameter of N-coordinated transition metal, which is attributed to the reduced interaction between Na+ and the framework, corroborated by the distribution of relaxation times and density functional theory calculations. Among the five PBAs studied, Mn-PBA have exhibited the highest Na+ conductivity of 9.1×10-2 mS cm-1 . Feasibility tests have revealed that Mn-PBA have maintained a cycle retention of 95.1 % after 80cycles at 30 °C and a C-rate of 0.2C. Our investigation into the underlying mechanisms that play a significant role in governing the conductivity and kinetics of these materials contributes valuable insights for the development of alternative strategies to realize all-solid-state batteries.

Unlocking the hidden chemical space in cubic-phase garnet solid electrolyte for efficient quasi-all-solid-state lithium batteries.

Garnet-type Li7La3Zr2O12 (LLZO) solid electrolytes (SE) demonstrates appealing ionic conductivity properties for all-solid-state lithium metal battery applications. However, LLZO (electro)chemical stability in contact with the lithium metal electrode is not satisfactory for developing practical batteries. To circumvent this issue, we report the preparation of various doped cubic-phase LLZO SEs without vacancy formation (i.e., Li = 7.0 such as Li7La3Zr0.5Hf0.5Sc0.5Nb0.5O12 and Li7La3Zr0.4Hf0.4Sn0.4Sc0.4Ta0.4O12). The entropy-driven synthetic approach allows access to hidden chemical space in cubic-phase garnet and enables lower solid-state synthesis temperature as the cubic-phase nucleation decreases from 750 to 400 °C. We demonstrate that the SEs with Li = 7.0 show better reduction stability against lithium metal compared to SE with low lithium contents and identical atomic species (i.e., Li = 6.6 such as Li6.6La3Zr0.4Hf0.4Sn0.4Sc0.2Ta0.6O12). Moreover, when a Li7La3Zr0.4Hf0.4Sn0.4Sc0.4Ta0.4O12 pellet is tested at 60 °C in coin cell configuration with a Li metal negative electrode, a LiNi1/3Co1/3Mn1/3O2-based positive electrode and an ionic liquid-based electrolyte at the cathode|SE interface, discharge capacity retention of about 92% is delivered after 700 cycles at 0.8 mA/cm2 and 60 °C.

High-energy and durable lithium metal batteries using garnet-type solid electrolytes with tailored lithium-metal compatibility.

Lithium metal batteries using solid electrolytes are considered to be the next-generation lithium batteries due to their enhanced energy density and safety. However, interfacial instabilities between Li-metal and solid electrolytes limit their implementation in practical batteries. Herein, Li-metal batteries using tailored garnet-type Li7-xLa3-aZr2-bO12 (LLZO) solid electrolytes is reported, which shows remarkable stability and energy density, meeting the lifespan requirements of commercial applications. We demonstrate that the compatibility between LLZO and lithium metal is crucial for long-term stability, which is accomplished by bulk dopant regulating and dopant-specific interfacial treatment using protonation/etching. An all-solid-state with 5 mAh cm-2 cathode delivers a cumulative capacity of over 4000 mAh cm-2 at 3 mA cm-2, which to the best of our knowledge, is the highest cycling parameter reported for Li-metal batteries with LLZOs. These findings are expected to promote the development of solid-state Li-metal batteries by highlighting the efficacy of the coupled bulk and interface doping of solid electrolytes.

A Biodegradable Secondary Battery and its Biodegradation Mechanism for Eco-Friendly Energy-Storage Systems.

The production of rechargeable batteries is rapidly expanding, and there are going to be new challenges in the near future about how the potential environmental impact caused by the disposal of the large volume of the used batteries can be minimized. Herein, a novel strategy is proposed to address these concerns by applying biodegradable device technology. An eco-friendly and biodegradable sodium-ion secondary battery (SIB) is developed through extensive material screening followed by the synthesis of biodegradable electrodes and their seamless assembly with an unconventional biodegradable separator, electrolyte, and package. Each battery component decomposes in nature into non-toxic compounds or elements via hydrolysis and/or fungal degradation, with all of the biodegradation products naturally abundant and eco-friendly. Detailed biodegradation mechanisms and toxicity influence of each component on living organisms are determined. In addition, this new SIB delivers performance comparable to that of conventional non-degradable SIBs. The strategy and findings suggest a novel eco-friendly biodegradable paradigm for large-scale rechargeable battery systems.

Voltage decay and redox asymmetry mitigation by reversible cation migration in lithium-rich layered oxide electrodes.

Despite the high energy density of lithium-rich layered-oxide electrodes, their real-world implementation in batteries is hindered by the substantial voltage decay on cycling. This voltage decay is widely accepted to mainly originate from progressive structural rearrangements involving irreversible transition-metal migration. As prevention of this spontaneous cation migration has proven difficult, a paradigm shift toward management of its reversibility is needed. Herein, we demonstrate that the reversibility of the cation migration of lithium-rich nickel manganese oxides can be remarkably improved by altering the oxygen stacking sequences in the layered structure and thereby dramatically reducing the voltage decay. The preeminent intra-cycle reversibility of the cation migration is experimentally visualized, and first-principles calculations reveal that an O2-type structure restricts the movements of transition metals within the Li layer, which effectively streamlines the returning migration path of the transition metals. Furthermore, we propose that the enhanced reversibility mitigates the asymmetry of the anionic redox in conventional lithium-rich electrodes, promoting the high-potential anionic reduction, thereby reducing the subsequent voltage hysteresis. Our findings demonstrate that regulating the reversibility of the cation migration is a practical strategy to reduce voltage decay and hysteresis in lithium-rich layered materials.

Nanoscale Phenomena in Lithium-Ion Batteries.

The electrochemical properties and performances of lithium-ion batteries are primarily governed by their constituent electrode materials, whose intrinsic thermodynamic and kinetic properties are understood as the determining factor. As a part of complementing the intrinsic material properties, the strategy of nanosizing has been widely applied to electrodes to improve battery performance. It has been revealed that this not only improves the kinetics of the electrode materials but is also capable of regulating their thermodynamic properties, taking advantage of nanoscale phenomena regarding the changes in redox potential, solid-state solubility of the intercalation compounds, and reaction paths. In addition, the nanosizing of materials has recently enabled the discovery of new energy storage mechanisms, through which unexplored classes of electrodes could be introduced. Herein, we review the nanoscale phenomena discovered or exploited in lithium-ion battery chemistry thus far and discuss their potential implications, providing opportunities to further unveil uncharted electrode materials and chemistries. Finally, we discuss the limitations of the nanoscale phenomena presently employed in battery applications and suggest strategies to overcome these limitations.

Unveiling the Intrinsic Cycle Reversibility of a LiCoO2 Electrode at 4.8-V Cutoff Voltage through Subtractive Surface Modification for Lithium-Ion Batteries.

The thermodynamic instability of the LiCoO2 layered structure at >0.5Li extraction has been considered an obstacle for the reversible utilization of its near theoretical capacity at high cutoff voltage (>4.6 V vs Li/Li+) in lithium-ion batteries. Many previous studies have focused on resolving this issue by surface modification of LiCoO2, which has proven to be effective in suppressing phase transformation. To determine the extent to which surface protection of LiCoO2 is effective despite its thermodynamic instability and presumably incomplete reversibility involving the O1 phase, here we verify the intrinsic reversibility of bulk LiCoO2 with extended lithium extraction by ruling out the effect of a surface. Specifically, first, we show that, contrary to conventional belief, electrochemical cycling of LiCoO2 at a cutoff voltage of 4.8 V (vs Li/Li+) results in better cycle stability and lower polarizations than those at 4.6 V. We demonstrate, using an exhaustive suite of characterization tools, that the rapid cycle degradation under high-voltage cycling is mostly caused by the formation of a surface resistive layer; however, these damaged surfaces are leached out faster than they are accumulated above a certain potential, which results in superior cyclability compared with that achieved for less oxidative 4.6-V cycling. This beneficial leaching out of the resistive surface layer serves as a "subtractive" surface modification and plays a role in enhancing the cycle stability and is distinguished from conventional "additive" surface modification such as coating. This approach allows us to decouple factors of the bulk and surface degradations that contribute to the capacity fade and leads to the finding that, in the absence of a resistive surface, the capacity retention of a LiCoO2 electrode with 4.8-V cutoff cycling can be intrinsically high, indicating that the instability of the crystalline Li xCoO2 ( x < 0.5) has a limited effect on the cycle stability. Our findings also explain why the strategy of coating foreign materials on the surface of LiCoO2 can improve the high-voltage cycling to some extent despite the expected thermodynamic instability of the highly charged phase.

Recent Progress in Organic Electrodes for Li and Na Rechargeable Batteries.

Organic rechargeable batteries, which use organics as electrodes, are excellent candidates for next-generation energy storage systems because they offer design flexibility due to the rich chemistry of organics while being eco-friendly and potentially cost efficient. However, their widespread usage is limited by intrinsic problems such as poor electronic conductivity, easy dissolution into liquid electrolytes, and low volumetric energy density. New types of organic electrode materials with various redox centers or molecular structures have been developed over the past few decades. Moreover, research aimed at enhancing electrochemical properties via chemical tuning has been at the forefront of organic rechargeable batteries research in recent years, leading to significant progress in their performance. Here, an overview of the current developments of organic rechargeable batteries is presented, with a brief history of research in this field. Various strategies for improving organic electrode materials are discussed with respect to tuning intrinsic properties of organics using molecular modification and optimizing their properties at the electrode level. A comprehensive understanding of the progress in organic electrode materials is provided along with the fundamental science governing their performance in rechargeable batteries thus a guide is presented to the optimal design strategies to improve the electrochemical performance for next-generation battery systems.