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Pre-lithiation is the most effective method to overcome the initial capacity loss of high-capacity electrodes and has the potential to be used in beyond-conventional lithium-ion batteries. In this article we focus on two types of pre-lithiation: the first type can be applied to batteries in which the cathode has been fully lithiated but the anode has a large initial capacity loss, such as batteries made with lithium metal oxide cathode and silicon-carbon anode. The second type can be applied to batteries in which both electrodes are initially lithium-free and suffer a loss of lithium during the initial cycles, such as batteries made with sulfurized polyacrylonitrile cathode and silicon-carbon anode. We describe the pre-lithiation procedures and electrode potential profiles during pre-lithiation corresponding to different pre-lithiation sources for both types of pre-lithiation. We also derive formulas for the theoretical specific energy and energy density that are based entirely on measurable parameters such as specific capacities, porosities, mass densities of two electrodes and extra lithium source, Coulombic efficiencies of electrodes, and the voltage of the cell. These formulas can be applied to different pre-lithiation sources to predict the specific energy of conventional and beyond conventional lithium-ion batteries as a function of the type of pre-lithiation. [ABSTRACT FROM AUTHOR]

As a new generation of capacitors, lithium-ion capacitors (LICs) have the same power density and cycle life as traditional electric double-layer capacitors, and 2-5 times the energy density. For the first time, in this paper we derive the mathematical formulas for the energy density of LICs. These formulas describe the relationship between the energy density of LICs and all the critical parameters, including the specific capacities of anode (negative) and cathode (positive) electrodes, the capacity ratio of anode to cathode electrodes, the maximum and minimum voltages of the LICs, the specific capacity of pre-lithiation source and the degree of the pre-lithiation and so on. These formulas provide not only a clear direction for future research in materials and devices of LICs, but also a useful tool for LIC design. [ABSTRACT FROM AUTHOR]

Pre-lithiation plays an increasingly significant role for high-energy Li-ion batteries (LIBs) since it can improve the energy density by compensating the Li loss during the initial cycle. The pre-lithiation related research so far has been focused on the development of materials and methods of pre-lithiation but has lacked theoretical and mathematical descriptions to illustrate the relationship between pre-lithiation and energy density. In this contribution, a series of mathematical formulas are derived to describe the gravimetric and volumetric energy densities of LIBs with pre-lithiation, by which the effects of the important parameters, e.g. the Coulombic efficiencies (CEs) of anode, the capacities of Li sources, etc., on the energy densities are well demonstrated. Then, the developed theory and mathematical formulas are applied to practical LIB systems, i.e. the cell using Li nickel manganese cobalt oxide (NMC) as a cathode and silicon-carbon (Si-C) composite as an anode, to identify possible energy density improvement after pre-lithiation. These systematic formulas with great universality have the potential to give significant guidelines for future studies on the pre-lithiation methods and be useful tools for the design of high energy LIBs with imperfect CEs from fundamental and practical perspectives. [ABSTRACT FROM AUTHOR]

Pre-lithiation is an essential technique for development of Li-ion sulfur batteries (LISBs), which have lower cost and higher durability than conventional Li-ion batteries. Herein, a simple and scalable pre-lithiation approach by direct contact with lithium foil is applied to a sulfur-polyacrylonitrile (S-PAN) cathode to construct LISBs, which exhibit an initial capacity of 1367 mAh g−1 and maintain 1192 mAh g−1 after 100 cycles. Moreover, we demonstrate the feasibility of proposed method on both electrodes for performance enhancement. The theoretical estimation further demonstrates the potential of the system for achieving high specific capacity and good cycle life at low cost. [ABSTRACT FROM AUTHOR]

The cathode microstructure of Li-air battery plays a significant role in Li2O2 storage and electron transfer. In this article, we report a tunable three-dimensional hierarchically macroporous carbon nanotube foam as the air cathode. Excellent electrochemical performance with a specific capacity over 10,000 mAh g-1 is achieved, which can be attributed to a combination of sufficiently large tunnels for oxygen transport and an appropriate pore width for oxygen reduction reaction. Also, an inverse correlation between the size of major pores and cell capacities is observed experimentally and a simplified analytical model is proposed to explain this correlation. Based on a combined study of galvanostatic discharge, microscopy, porosimetry, and modeling, we find that the discharge product Li2O2 is mainly deposited in the major pores of CNT foams. [ABSTRACT FROM AUTHOR]

In recent years, an increased attention has been focused on Li-ion capacitors (LICs) which are high power hybrid devices. Various carbon materials (hard carbon (HC), soft carbon (SC) and graphite) have been investigated for use as the negative electrodes for LICs. The rate capabilities are compared by half cells with carbon anode as working electrode and lithium foil as counter electrode, and by LIC full cells with test current density up to 20 mA cm-2 . It is found that the LIC with HC and SC at 20 mA cm-2 can be maintained up to 72.5% and 70%, compared to that at 0.5 mA cm-2, which is better power performance than the graphite materials. LICs with both HC and SC as anodes displayed better cycle lifes than graphite anode. After 100,000 high-rate charge-discharge cycles, the capacity retention of the LIC with HC anode maintained higher than 85%. The Scanning electron microscopy (SEM) images, surface area and the pore size distribution are also studied and compared for the various carbon anode materials. [ABSTRACT FROM AUTHOR]

Understanding the behavior of lithium (Li)-sulfur (S) cells under lithium polysulfide (LiPS)-saturated condition, especially determining whether LiPS solubility is an intrinsic limit for cell capacity, is of great interest for the development of high energy density Li-S batteries. In this work, sets of Li-S cells were tested under designed scenarios to demonstrate the effect of LiPS solubility on cell capacity. It revealed that when LiPS solubility limit is reached, though sulfur can be reduced to solid state LiPS, it cannot further convert to subsequent discharge products and contribute to cell capacity. [ABSTRACT FROM AUTHOR]

We proposed an electrochemical capacitor that consists of a battery/double-layer capacitor or a pseudocapacitor/pseudocapacitor electrode configuration, with charge transferring during the charge and discharge processes. This is fundamentally different from exiting capacitors including conventional double-layer electrochemical capacitors and asymmetrical cells. The ions in the proposed capacitors are shuttled between two electrodes during the charge and discharge cycle. The theoretical energy density of the proposed asymmetric capacitors is as high as 60 W h/kg vs less than 15 and 25 W h/kg for conventional double-layer capacitors and battery/double-layer capacitors, respectively. [ABSTRACT FROM AUTHOR]