Semiconduction properties of some polyene-iodine charge-transfer complexes and their application in solid-state batteries

The conjugated polyenes -carotene, lutein, retinoic acid and -apo-8-carotenal are shown to form charge-transfer (CT) complexes with the electron acceptor iodine. The conductivity increases by several orders of magnitude and the activation energy decreases on CT complex formation. Using these complexes as cathodic material, batteries with the configuration Mg/(polyene-iodine CT complex) /graphite are developed. Different battery parameters are evaluated. The effects of ambient temperature and humidity on battery performance are also studied. Results show that a -apo-8-carotenal-l₂ based battery has the maximum power density and longest self-life and is suitable for use as a micro-electronic gadget energizer.     

Spectroscopic,dark and photoconductive properties of some polyene-iodine charge-transfer complexes

Spectroscopic evidence has been provided to confirm that zeaxanthin, lutein and fucoxanthin form molecular charge-transfer (CT) complexes with iodine in the solid state. The semiconductive and photoconductive properties of CT complexes have been investigated in polycrystals in a sandwich cell configuration. Both dark and photoconductivity increases by several orders of magnitude on complex formation. The identical values of thermal activation energies for dark and photoconduction have been obtained for the complexes and this has been attributed to spontaneous carrier generation by CT interaction and their migration by trapping and detrapping mechanisms. Photoconduction action spectra in pure polyene and in polyene-iodine complex suggest that photoinjection from the electrode and direct electron hole pair production are the two photocarrier generation mechanisms operative in these crystals. The second mechanism predominates in pure materials whereas the first one becomes important in the complexes.     

Predicting low-impedance interfaces for solid-state batteries

All-solid-state batteries are an exciting technology for increased safety and energy density compared to traditional lithium-ion cells. Recently, we developed a theory of mapping inner potentials and thermodynamic driving forces specific to the solid-state batteries, allowing prediction of the “intrinsic” interfacial lithium barriers. This potential mapping methodology, based purely on calculated bulk and surface properties, enables fast screening of a variety of advanced solid electrolyte materials as well as a selection of cutting-edge high-voltage cathode materials, predicting properties of 48 distinct battery configurations. A number of cathode/electrolyte pairs are identified which have low “intrinsic” barriers to both the charge and discharge process at all states of charge, suggesting that they will most benefit from engineering efforts to reduce extrinsic interfacial impedance. These predictions agree well with available experimental measurements, which form only a subset of the predicted interfaces. Thus, this interface potential model will accelerate the design process from emerging materials to all-solid-state battery devices.     

Advances in solid-state fiber batteries for wearable bioelectronics

Powering wearable bioelectronics with decent skin conformability and wearing comfort is highly desired. Fiber batteries could provide an attractive alternative to traditional rigid ones and present a compelling solution to this problem. In this review, we will discuss the various classes of fiber batteries, including lithium batteries, zinc batteries, and other types of fiber batteries. We will then report the latest research progress on each battery category through its working mechanism, materials usage, structure design, and wearable applications. Finally, we provide insights into current challenges and future applications of fiber batteries, aiming to promote the development of low-cost and high-performance fiber battery technologies for wearable bioelectronics.     

Primary solid-state batteries constructed from copper and indium sulphides

Copper and indium sulphides were prepared by a chemical precipitation method and further characterized. Low-cost, easily fabricated dry cells were constructed by gluing the metal sulphides on a magnesium foil using a polymer electrolyte. The efficiency, energy densities and cell voltage values of the cells were in the range 8.1–6.2 mWh cm^–3, 150–77 mWh g^–1 and 1.58–1.21 V, respectively.     

Mesoporous nitrogen-doped carbon-glass ceramic cathodes for solid-state lithium-oxygen batteries

The composite of nitrogen-doped carbon (N-C) blend with lithium aluminum germanium phosphate (LAGP) was studied as cathode material in a solid-state lithium-oxygen cell. Composite electrodes exhibit high electrochemical activity toward oxygen reduction. Compared to the cell capacity of N-C blend cathode, N-C/LAGP composite cathode exhibits six times higher discharge cell capacity. A significant enhancement in cell capacity is attributed to higher electrocatalytic activity and fast lithium ion conduction ability of LAGP in the cathode.     

Polymer electrolytes and interfaces in solid-state lithium metal batteries

The polymer electrolyte based solid-state lithium metal batteries are the promising candidate for the high-energy electrochemical energy storage with high safety and stability. Moreover, the intrinsic properties of polymer electrolytes and interface contact between electrolyte and electrodes have played critical roles for determining the comprehensive performances of solid-state lithium metal batteries. In this review, the development of polymer electrolytes with the design strategies by functional units adjustments are firstly discussed. Then the interfaces between polymer electrolyte and cathode/anode, including the interface issues, remedy strategies for stabilizing the interface contact and reducing resistances, and the in-situ polymerization method for enhancing the compatibilities and assembling the batteries with favorable performances, have been introduced. Lastly, the perspectives on developing polymer electrolytes by functional units adjustment, and improving interface contact and stability by effective strategies for solid-state lithium metal batteries have been provided.     

Customizable solid-state batteries toward shape-conformal and structural power supplies

With the advent of intelligent electronics and green transportation systems, power sources with customized shape, flexibility, functionality and high security are indispensable. Innovative customizable solid-state batteries have recently been explored as a key-enabling technology to achieve this vision. Such custom-made power sources enable the monolithic integration of bipolar-stacked cells onto complex-shaped substrates, maximize space utilization of devices, meanwhile minimize the use of inactive components. Hence, they hold great potential in reducing the total weight of target electronic devices, extending their lifespan, and even as structural batteries to replace structural components in robotics, implants and electric vehicles. This review describes state-of-the-art of customizable solid-state batteries with a focus on fabrication techniques and corresponding material considerations. The relationship between the battery architecture design and form-factors of cells concerning their mechanical and electrochemical properties are in focus. The challenges and future developments of customizable solid-state batteries are elaborated with respect to their potential applications. Through novel material engineering, structural evolution, on-going extension of high-throughput fabrication technology, and integration of multifunctional systems, the customizable solid-state batteries will pave their way to power a growing share of smart electronics and modern transportation systems.     

Processing and manufacturing of next generation lithium-based all solid-state batteries

All solid-state batteries are safe and potentially energy dense alternatives to conventional lithium ion batteries. However, current solid-state batteries are projected to costs well over $100/kWh. The high cost of solid-state batteries is attributed to both materials processing costs and low throughput manufacturing. Currently there are a range of solid electrolytes being examined and each material requires vastly different working environments and processing conditions. The processing environment (pressure and temperature) and cell operating conditions (pressure and temperature) influence costs. The need for high pressure during manufacturing and/or cell operation will ultimately increase plant footprint, costs, and machine operating times. Long term, for solid state batteries to become economical, conventional manufacturing approaches need to be adapted. In this perspective we discuss how material selection, processing approach, and system architecture will influence lithium-based solid state battery manufacturing.     

固态电池中的正极/电解质界面性质研究进展EI北大核心CSCD

锂离子电池是便携式电子产品、电动汽车和智能电网的理想电源。目前使用有机液体电解质的锂离子电池仍然存在安全问题和寿命不足的问题,而使用不燃的固态电解质的固态电池有望解决这些问题。从原理上讲,不燃的固体电解质可以从根本上防止电池的燃烧和爆炸,并且只允许锂离子在固体电解质中传输,可以减少副反应的发生。近年来,随着几种高离子电导率的固态电解质的出现,锂离子在固态电解质中的传输不再是瓶颈。然而,固态电池中各种固态成分具有不同的化学/物理/力学性能,因此在固态电池中存在多种类型的界面,包括松散的物理接触、晶界、化学和电化学反应界面等,这些都可能增加界面离子传输阻力。而正极材料与电解质之间的界面反应尤其复杂,深入理解这些复杂的正极侧界面及其反应特点是实现实用高比能固态电池的必要条件。因此,本文主要回顾了近年来在探索和理解正极/电解质界面上的工作,总结了固态电池中典型的正极侧界面类型及其各自独特的反应特征。     

Understanding all solid-state lithium batteries through in situ transmission electron microscopy

Owing to the use of solid electrolytes instead of flammable and potentially toxic organic liquid electrolytes, all solid-state lithium batteries (ASSLBs) are considered to have substantial advantages over conventional liquid electrolyte based lithium ion batteries(LIBs) in terms of safety, energy density, battery packaging, and operable temperature range. However, the electrochemistry and the operation mechanism of ASSLBs differ considerably from conventional LIBs. Consequently, the failure mechanisms of ASSLBs, which are not well understood, require particular attention. To improve the performance and realize practical applications of ASSLBs, it is crucial to unravel the dynamic evolution of electrodes, solid electrolytes, and their interfaces and interphases during cycling of ASSLBs. In situ transmission electron microscopy (TEM) provides a powerful approach for the fundamental investigation of structural and chemical changes during operation of ASSLBs with high spatio-temporal resolution. Herein, recent progress in in situ TEM studies of ASSLBs are reviewed with a specific focus on real-time observations of reaction and degradation occurring in electrodes, solid electrolytes, and their interfaces. Novel electro-chemo-mechanical coupling phenomena are revealed and mechanistic insights are highlighted. This review covers a broad range of electrode and electrolyte materials applied in ASSLBs, demonstrates the general applicability of in situ TEM for elucidating the fundamental mechanisms and providing the design guidance for the development of high-performance ASSLBs. Finally, challenges and opportunities for in situ TEM studies of ASSLBs are discussed.     

Electrolyte stability determines scaling limits for solid-state 3D Li ion batteries

Rechargeable, all-solid-state Li ion batteries (LIBs) with high specific capacity and small footprint are highly desirable to power an emerging class of miniature, autonomous microsystems that operate without a hardwire for power or communications. A variety of three-dimensional (3D) LIB architectures that maximize areal energy density has been proposed to address this need. The success of all of these designs depends on an ultrathin, conformal electrolyte layer to electrically isolate the anode and cathode while allowing Li ions to pass through. However, we find that a substantial reduction in the electrolyte thickness, into the nanometer regime, can lead to rapid self-discharge of the battery even when the electrolyte layer is conformal and pinhole free. We demonstrate this by fabricating individual, solid-state nanowire core-multishell LIBs (NWLIBs) and cycling these inside a transmission electron microscope. For nanobatteries with the thinnest electrolyte, ≈110 nm, we observe rapid self-discharge, along with void formation at the electrode/electrolyte interface, indicating electrical and chemical breakdown. With electrolyte thickness increased to 180 nm, the self-discharge rate is reduced substantially, and the NWLIBs maintain a potential above 2 V for over 2 h. Analysis of the nanobatteries' electrical characteristics reveals space-charge limited electronic conduction, which effectively shorts the anode and cathode electrodes directly through the electrolyte. Our study illustrates that, at these nanoscale dimensions, the increased electric field can lead to large electronic current in the electrolyte, effectively shorting the battery. The scaling of this phenomenon provides useful guidelines for the future design of 3D LIBs.     

Electrochemically stable lithium-ion and electron insulators(LEIs)for solid-state batteries

Rechargeable solid-state Li metal batteries demand ordered flows of Li-ions and electrons in and out of solid structures,with repeated waxing and waning of Ubcc phase near contact interfaces which gives rise to various electro-chemo-mechanical challenges.There have been approaches that adopt three-dimensional(3D)nanoporous architectures consisting of mixed ion-electron conductors(MIECs)to combat these challenges.However,there has remained an issue of LiBcc nucleation at the interfaces between different solid components(e.g.,solid electrolyte/MlEC interface),which could undermine the interfacial bonding,thereby leading to the evolution of mechanical instability and the loss of ionic/electronic percolation.In this regard,the present work shows that the Li-ion and electron insulators(LEIs)that are thermodynamically stable against LiBcc could combat such challenges by blocking transportation of charge carriers on the interfaces,analogous to dielectric layers in transistors.We searched the ab initio database and have identified 48 crystalline compounds to be LEI candidates(46 experimentally reported compounds and 2 hypothetical compounds predicted to be stable)with a band gap greater than 3 eV and vanishing Li solubility.Among these compounds,those with good adhesion to solid electrolyte and mixed ion-electron conductor of interest,but are lithiophobic,are expected to be the most useful.We also extended the search to Na or K metal compatible alkali-ion and electron insulators,and identified some crystalline compounds with a property to resist corresponding alkali-ions and electrons.     

The Sand equation and its enormous practical relevance for solid-state lithium metal batteries

In this work, different Li salt concentrations and ionic conductivities of poly(ethylene oxide)-based solid polymer electrolytes (PEO-based SPEs) are correlated with the performance of LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622)||Li full cells. While the SPEs with different salt concentrations behave similarly in NMC622||Li cells at 60 °C, their influence on the specific capacities is significant at 40 °C. Below a distinct salt concentration, i.e. > 20:1 (EO:Li), a sudden blocking-type polarization appears, indicatable by an almost vertical voltage profile, both in full and in Li||Li symmetric cells. The corresponding time and current density for this polarization-type is shown to mathematically fit with the Sand equation, which subsequently allows calculation of D_Li⁺. According this relation, lack of Li⁺ in the electrolyte close to the electrode surface can be concluded to be the origin of this polarization, but is shown to appear only for “kinetically limiting” conditions e.g. above a threshold current density, above a threshold SPE thickness and/or below a threshold salt concentration (ionic conductivity), i.e. at mass transfer limiting conditions. With the support of this relation, maximal applicable current densities and/or SPE thicknesses can be calculated and predicted for SPEs.     

Designing inorganic electrolytes for solid-state Li-ion batteries: A perspective of LGPS and garnet

Solid-state Li-ion batteries (SSLBs) are promising next-generation energy storage devices with high energy density and enhanced safety. The solid-state electrolyte (SSE) is a key component for delivering the desired electrochemical performance characteristics. This article provides a brief review of the discovery, synthesis, structure, ion-conduction mechanism, and application of LGPS-type and garnet-type Li ion conductors as two representative SSEs, aiming to extract principles for the future design and discovery of favourable solid-state Li-ion electrolytes for SSLBs. Recent advances in strategies to address the SSLB challenges are also discussed. Finally, a perspective on the future research directions of SSLBs is provided.     

Lithium-ion conductive ceramic textile: A new architecture for flexible solid-state lithium metal batteries

Designing solid-state lithium metal batteries requires fast lithium-ion conductors, good electrochemical stability, and scalable processing approaches to device integration. In this work, we demonstrate a unique design for a flexible lithium-ion conducting ceramic textile with the above features for use in solid-state batteries. The ceramic textile was based on the garnet-type conductor Li₇La₃Zr₂O₁₂ and exhibited a range of desirable chemical and structural properties, including: lithium-ion conducting cubic structure, low density, multi-scale porosity, high surface area/volume ratio, and good flexibility. The solid garnet textile enabled reinforcement of a solid polymer electrolyte to achieve high lithium-ion conductivity and stable long-term Li cycling over 500?h without failure. The textile also provided an electrolyte framework when designing a 3D electrode to realize ultrahigh cathode loading (10.8?g/cm² sulfur) for high-performance Li-metal batteries.     

Fast lithium-ion conducting thin-film electrolytes integrated directly on flexible substrates for high-power solid-state batteries

By utilizing an equilibrium processing strategy that enables co-firing of oxides and base metals, a means to integrate the lithium-stable fast lithium-ion conductor lanthanum lithium tantalate directly with a thin copper foil current collector appropriate for a solid-state battery is presented. This resulting thin-film electrolyte possesses a room temperature lithium-ion conductivity of 1.5 × 10(-5) S cm(-1) , which has the potential to increase the power of a solid-state battery over current state of the art.