Pliable Lithium Superionic Conductor for AllSolid-State Batteries

The key challenges in all-solid-state batteries (ASSBs) are establishing and maintaining perfect physical contact between rigid components for facile interfacial charge transfer, particularly between the solid electrolyte and cathode, during repeated electrochemical cycling. Here, we introduce inorganic-based pliable solid electrolytes that exhibit extraordinary clay-like mechanical properties (storage and loss moduli <1 MPa) at room temperature, high lithium-ion conductivity (3.6 mS cm(-1)), and a glass transition below -50 degrees C. The unique mechanical features enabled the solid electrolyte to penetrate into the high-loading cathode like liquid, thereby providing complete ionic conduction paths for all cathode particles as well as maintaining the pathway even during cell operation. We propose a design principle in which the complex anion formation including Ga, F, and a different halogen can induce the claylike features. Our findings provide new opportunities in the search for solid electrolytes and suggest a new approach for resolving the issues caused by the solid electrolyte-cathode interface in ASSBs

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

Toward a Lithium−“Air” Battery: The Effect of CO_2 on the Chemistry of a Lithium−Oxygen Cell

Lithium–oxygen chemistry offers the highest energy density for a rechargeable system as a “lithium–air battery”. Most studies of lithium–air batteries have focused on demonstrating battery operations in pure oxygen conditions; such a battery should technically be described as a “lithium–dioxygen battery”. Consequently, the next step for the lithium–“air” battery is to understand how the reaction chemistry is affected by the constituents of ambient air. Among the components of air, CO_2 is of particular interest because of its high solubility in organic solvents and it can react actively with O_2–•, which is the key intermediate species in Li–O_2 battery reactions. In this work, we investigated the reaction mechanisms in the Li–O_2/CO_2 cell under various electrolyte conditions using quantum mechanical simulations combined with experimental verification. Our most important finding is that the subtle balance among various reaction pathways influencing the potential energy surfaces can be modified by the electrolyte solvation effect. Thus, a low dielectric electrolyte tends to primarily form Li_2O_2, while a high dielectric electrolyte is effective in electrochemically activating CO_2, yielding only Li_2CO_3. Most surprisingly, we further discovered that a high dielectric medium such as DMSO can result in the reversible reaction of Li_2CO_3 over multiple cycles. We believe that the current mechanistic understanding of the chemistry of CO_2 in a Li–air cell and the interplay of CO_2 with electrolyte solvation will provide an important guideline for developing Li–air batteries. Furthermore, the possibility for a rechargeable Li–O_2/CO_2 battery based on Li_2CO_3 may have merits in enhancing cyclability by minimizing side reactions

Sodium-oxygen batteries with alkyl-carbonate and ether based electrolytes

Recently, metal-air batteries, such as lithium-air and zinc-air systems, have been studied extensively as potential candidates for ultra-high energy density storage devices because of their exceptionally high capacities. Here, we report such an electrochemical system based on sodium, which is abundant and inexpensive. Two types of sodium-oxygen batteries were introduced and studied, i.e. with carbonate and non-carbonate electrolytes. Both types could deliver specific capacities (2800 and 6000 mA h g(-1)) comparable to that of lithium-oxygen batteries but with slightly lower discharge voltages (2.3 V and 2.0 V). The reaction mechanisms of sodium-oxygen batteries in carbonate and non-carbonate electrolytes were investigated and compared with those of lithium-oxygen batteries.

Phase Stability Study of Li1-xMnPO4 (0 <= x <= 1) Cathode for Li Rechargeable Battery

The phase stability of Li1-xMnPO4 (0 <= x <= 1) is investigated in this study for different Li compositions and temperatures by high temperature X-ray diffraction and electron microscopy. The map of stable phases is determined at temperature ranges between room temperature and 410 degrees C. While pure LiMnPO4 phase is stable at high temperature, partial phase transformation of MnPO4 into Mn2P2O7 is observed in delithiated phases above 210 degrees C. Electron microscopy study also indicates the instability of the delithiated phase. The morphology of LiMnPO4 is severely damaged upon delithiation. The instability of the delithiated phase and the phase transformation into Mn2P2O7 may imply that safety concerns can be raised regarding the LiMnPO4 cathode, unlike its Fe counterpart.

Review-Lithium-Excess Layered Cathodes for Lithium Rechargeable Batteries

The exceptionally high gravimetric capacity of lithium-excess layered cathodes (LLCs) has generated interest in their use in lithium-ion batteries (LIBs) for high-capacity applications. Their unique electrochemical and structural properties are responsible for this high capacity, which exceeds the theoretical redox capability of transition metal oxides and have been intensively investigated. However, various fundamental and practical challenges must be overcome before LLCs can be successfully commercialized. The structure of pristine LLCs, which varies with the composition and type of transition metal species used, remains unclear. In addition, the structure continuously changes during electrochemical cycling, which further complicates its understanding. In this review, we discuss the current understanding of LLCs, including their pristine structures, redox chemistries, and structural evolution during cycling, and suggest future research directions to address the critical issues. (C) 2015 The Electrochemical Society. All rights reserved

Recent progress on flexible lithium rechargeable batteries

Flexible lithium ion batteries (LIBs) have received considerable attention as a key component to enable future flexible electronic devices. A number of designs for flexible LIBs have been reported in recent years; in this article, we review recent progress. We focus on how flexibility can be introduced into each component of the LIB, including the active materials, electrolytes, separators, and current collectors. Approaches to integrating each component into a single device are described and the corresponding changes in the electrochemical and mechanical properties are discussed. Finally, the key challenges in the development of flexible LIBs are summarized

Comparative study of Li(Li1/3Ti5/3)O-4 and Li(Ni1/2-xLi2x/3Tix/3)Ti3/2O4 (x=1/3) anodes for Li rechargeable batteries

A solid solution of spinel (2/3)Li(Li1/3Ti5/3)O-4-(1/3)Li(Ni1/2Ti3/2)O-4 was prepared, and its structural/electrochemical properties were compared with Li(Li1/3Ti5/3)O-4 to identify the effect of doping to the structural invariance of Li(Li1/3Ti5/3)O-4. The solid solution retained the zero strain characteristic of Li(Li1/3Ti5/3)O-4 during discharge/charge with an excellent cycle stability, while the rate capability was notably improved. However, a reversible broadening of the XRD peak was observed at the end of discharge, indicating some structural changes. XANES measurements showed that the oxidation state of Ti was +4 and that of Ni was +2 in the solid solution. (C) 2009 Elsevier Ltd. All rights reserved.

The potential for long-term operation of a lithium-oxygen battery using a non-carbonate-based electrolyte

Herein we demonstrate the feasibility of extended cycle operation of a Li-O-2 battery by simple control of the discharge/charge protocol. By avoiding electrolyte decomposition and the deep discharge state of the air electrode, we were able to construct a Li-O-2 cell capable of efficiently cycling over 50 times with high energy density.

Synthesis of Multicomponent Olivine by a Novel Mixed Transition Metal Oxalate Coprecipitation Method and Electrochemical Characterization

The multicomponent olivine cathode material. LiMn(1/3)Fe(1/3)Co(1/3)PO(4), was prepared via a novel coprecipitation method of the mixed transition metal oxalate, Mn(1/3)Fe(1/3)Co(1/3)(C(2)O(4))center dot 2H(2)O. The stoichiometric ratio and distribution of transition metals in the oxalate, therefore, in the olivine product, was affected sensitively by the environments in the coprecipitation process, while they are the important factors in determining the electrochemical property of electrode materials with multiple transition metals. The effect of the pH, atmosphere, temperature, and aging time was investigated thoroughly with respect to the atomic ratio of transition metals, phase purity, and morphology of the mixed transition metal oxalate. The electrochemical activity of each transition metal in the olivine synthesized through this method clearly was enhanced as indicated in the cyclic voltammetry (CV) and galvanostatic charge/discharge measurement Three distinctive contributions from Mn. Fe, and Co redox couples were detected reversibly in multiple charge and discharge processes. The first discharge capacity at the C/5 rate was 140 5 mAh g(-1) with good cycle retention The rate capability test showed that the high capacity still is retained even at the 4C and 6C rates with 102 and 81 mAh g(-1), respectively