Concept: Lithium battery
Current lithium batteries operate on inorganic insertion compounds to power a diverse range of applications, but recently there is a surging demand to develop environmentally friendly green electrode materials. To develop sustainable and eco-friendly lithium ion batteries, we report reversible lithium ion storage properties of a naturally occurring and abundant organic compound purpurin, which is non-toxic and derived from the plant madder. The carbonyl/hydroxyl groups present in purpurin molecules act as redox centers and reacts electrochemically with Li-ions during the charge/discharge process. The mechanism of lithiation of purpurin is fully elucidated using NMR, UV and FTIR spectral studies. The formation of the most favored six membered binding core of lithium ion with carbonyl groups of purpurin and hydroxyl groups at C-1 and C-4 positions respectively facilitated lithiation process, whereas hydroxyl group at C-2 position remains unaltered.
One of the most exciting areas in lithium ion batteries is engineering structured silicon anodes. These new materials promise to lead the next generation of batteries with significantly higher reversible charge capacity than current technologies. One drawback of these materials is that their production involves costly processing steps, limiting their application in commercial lithium ion batteries. In this report we present an inexpensive method for synthesizing macroporous silicon particulates (MPSPs). After being mixed with polyacrylonitrile (PAN) and pyrolyzed, MPSPs can alloy with lithium, resulting in capacities of 1000 mAhg(-1) for over 600+ cycles. These sponge-like MPSPs with pyrolyzed PAN (PPAN) can accommodate the large volume expansion associated with silicon lithiation. This performance combined with low cost processing yields a competitive anode material that will have an immediate and direct application in lithium ion batteries.
New energy industry including electric vehicles and large-scale energy storage in smart grids requires energy storage systems of good safety, high reliability, high energy density and low cost. Here a coated Li metal is used as anode for an aqueous rechargeable lithium battery (ARLB) combining LiMnO as cathode and 0.5 mol l LiSO aqueous solution as electrolyte. Due to the “cross-over” effect of Li ions in the coating, this ARLB delivers an output voltage of about 4.0 V, a big breakthrough of the theoretic stable window of water, 1.229 V. Its cycling is very excellent with Coulomb efficiency of 100% except in the first cycle. Its energy density can be 446 Wh kg, about 80% higher than that for traditional lithium ion battery. Its power efficiency can be above 95%. Furthermore, its cost is low and safety is much reliable. It provides another chemistry for post lithium ion batteries.
Destructive gas generation with associated swelling has been a major challenge to the large-scale application of lithium ion batteries (LIBs) made from Li(4)Ti(5)O(12) (LTO) anodes. Here we report root causes of the gassing behavior, and suggest remedy to suppress it. The generated gases mainly contain H(2), CO(2) and CO, which originate from interfacial reactions between LTO and surrounding alkyl carbonate solvents. The reactions occur at the very thin outermost surface of LTO (111) plane, which result in transformation from (111) to (222) plane and formation of (101) plane of anatase TiO(2). A nanoscale carbon coating along with a stable solid electrolyte interface (SEI) film around LTO is seen most effective as a barrier layer in suppressing the interfacial reaction and resulting gassing from the LTO surface. Such an ability to tune the interface nanostructure of electrodes has practical implications in the design of next-generation high power LIBs.
We demonstrate a simple, efficient, yet versatile strategy for the synthesis of novel hierarchical heterostructures composed of TiO(2) nanofiber stem and various metal oxides (MOs) secondary nanostructures, including Co(3)O(4), Fe(2)O(3), Fe(3)O(4), and CuO, by advantageously combining the versatility of the electrospinning technique and hydrothermal growth method, for which the controllable formation process and possible formation mechanism are also investigated. Moreover, as a proof-of-concept demonstration of the functional properties of these hierarchical heterostructures, the Co(3)O(4)/TiO(2) hierarchical heterostructures are investigated as the lithium-ion batteries (LIBs) anode materials for the first time, which not only delivers a high reversible capacity of 632.5 mAh g(-1) and 95.3% capacity retention over 480 cycles, but also shows excellent rate capability with respect to the pristine TiO(2) nanofibers. The synergetic effect between Co(3)O(4) and TiO(2) as well as the unique feature of hierarchical heterostructures are probably responsible for the enhanced electrochemical performance.
Although the energy densities of batteries continue to increase, safety problems (for example, fires and explosions) associated with the use of highly flammable liquid organic electrolytes remain a big issue, significantly hindering further practical applications of the next generation of high-energy batteries. We have fabricated a novel “smart” nonwoven electrospun separator with thermal-triggered flame-retardant properties for lithium-ion batteries. The encapsulation of a flame retardant inside a protective polymer shell has prevented direct dissolution of the retardant agent into the electrolyte, which would otherwise have negative effects on battery performance. During thermal runaway of the lithium-ion battery, the protective polymer shell would melt, triggered by the increased temperature, and the flame retardant would be released, thus effectively suppressing the combustion of the highly flammable electrolytes.
Nanoparticulate electrodes, such as Li x FePO4, have unique advantages over their microparticulate counterparts for the applications in Li-ion batteries because of the shortened diffusion path and access to nonequilibrium routes for fast Li incorporation, thus radically boosting power density of the electrodes. However, how Li intercalation occurs locally in a single nanoparticle of such materials remains unresolved because real-time observation at such a fine scale is still lacking. We report visualization of local Li intercalation via solid-solution transformation in individual Li x FePO4 nanoparticles, enabled by probing sub-angstrom changes in the lattice spacing in situ. The real-time observation reveals inhomogeneous intercalation, accompanied with an unexpected reversal of Li concentration at the nanometer scale. The origin of the reversal phenomenon is elucidated through phase-field simulations, and it is attributed to the presence of structurally different regions that have distinct chemical potential functions. The findings from this study provide a new perspective on the local intercalation dynamics in battery electrodes.
We have produced stretchable lithium-ion batteries (LIBs) using the concept of kirigami, i.e., a combination of folding and cutting. The designated kirigami patterns have been discovered and implemented to achieve great stretchability (over 150%) to LIBs that are produced by standardized battery manufacturing. It is shown that fracture due to cutting and folding is suppressed by plastic rolling, which provides kirigami LIBs excellent electrochemical and mechanical characteristics. The kirigami LIBs have demonstrated the capability to be integrated and power a smart watch, which may disruptively impact the field of wearable electronics by offering extra physical and functionality design spaces.
Herein, facile synthesis of monodisperse silicon and carbon nanocomposite spheres (MSNSs) is achieved via a simple and scalable surface-protected magnesiothermic reduction with subsequent chemical vapor deposition (CVD) process. Li-ion batteries (LIBs) were fabricated to test the utility of MSNSs as an anode material. LIB anodes based on MSNSs demonstrate a high reversible capacity of 3207 mAh g(-1), superior rate performance, and excellent cycling stability. Furthermore, the performance of full cell LIBs was evaluated by using MSNS anode and a LiCoO2 cathode with practical electrode loadings. The MSNS/LiCoO2 full cell demonstrates high gravimetric energy density in the order of 850 Wh L(-1) with excellent cycling stability. This work shows a proof of concept of the use of monodisperse Si and C nanocomposite spheres toward practical lithium-ion battery applications.
Materials synthesis often provides opportunities for innovation. We demonstrate a general low-temperature (260°C) molten salt electrodeposition approach to directly electroplate the important lithium-ion (Li-ion) battery cathode materials LiCoO2, LiMn2O4, and Al-doped LiCoO2. The crystallinities and electrochemical capacities of the electroplated oxides are comparable to those of the powders synthesized at much higher temperatures (700° to 1000°C). This new growth method significantly broadens the scope of battery form factors and functionalities, enabling a variety of highly desirable battery properties, including high energy, high power, and unprecedented electrode flexibility.