Lightweight Lithium Ion Batteries Research Articles

A Low-Cost and Lightweight Thermal Management System for Lithium-Ion Battery Modules Based on Composite PCM under Normal EV Operating Conditions

In this paper, a novel low-cost and lightweight lithium ion batteries thermal design based on EG-based composite phase change material to store heat under normal EV operating conditions is developed and verified theoretically. The three dimensional thermal simulation model is proposed to compute the transient temperature of the battery at some actual driving conditions during discharge. The capability of battery thermal management system based on composite PCM under four kinds of actual electric vehicles thermal safety evaluation condition is investigated, and some factors influencing the system are discussed in detail. Simulation results show that the temperature of the lithium ion battery can be maintained within a reasonable range by adopting the cooling system. The highest temperature of battery discharging at 1C rate can be kept no more than 45.1 °C in the cost of 0.5mm in thickness and 1.02kg in weight increment of PCM and the temperature consistency evaluation methods based on integral values were proposed. The conclusions got in this paper can be valuable reference for battery thermal management design and analysis of dissipating heat against daily driving discharge condition.

Design and Optimization of Lightweight Lithium-Ion Battery Protector with 3D Auxetic Meta Structures

This research study involves designing and optimizing a sandwich structure based on an auxetic structure to protect the pouch battery system for electric vehicles undergoing ground impact load. The core of the sandwich structure is filled with the auxetic structure that has gone through optimization to maximize the specific energy absorbed. Its performance is analyzed with the non-linear finite element method. Five geometrical variables of the auxetic structures are analyzed using the analysis of variance and optimized using Taguchi’s method. The optimum control variables are double-U hierarchal (DUH), the cross-section’s thickness = 2 mm, the length of the cell = 10 mm, the width of the cell = 17 mm, and the bending height = 3 mm. The optimized geometries are then arranged into three different sandwich structure configurations. The core is filled with optimized DUH cells that have been enlarged to 200% in length, arranged in 11 × 11 × 1 cells, resulting in a total dimension and mass of 189 × 189 × 12 mm and 0.75 Kg. The optimized sandwich structure shows that the pouch battery cells can be protected very well from ground impact load with a maximum deformation of 1.92 mm, below the deformation threshold for battery failure.

Multiphysics coupled computational model for commercialized Si/graphite composite anode

Si/graphite composite (Si/G) anodes are now regarded among the most commercially available next-generation anode materials. The development of a fully coupled mechanical-electrochemical model for Si/G anode is an essential tool to design safer and lightweight lithium-ion battery modules/packs. In this paper, we establish an efficient model to study lithium-ion battery (LIB) with Si/G composite anode through the coupling of stress-induced battery model and homogenized mechanical model. By designing strategies for the coupling of mechanical and electrochemical governing equations, a multiphysics model is proposed. Experiments for battery charging with simultaneous various mechanical loadings are conducted to validate the established model. Finally, design-oriented parametric studies for governing factors (e.g., the Si/G mixture ratio and battery size) are discussed. Results provide a fundamental understanding of the failure mechanism of the composite anode and offer a powerful design tool for Si/G composite anode design for better electrochemical performance.

Graphene decorated polymeric flexible materials for lightweight high areal energy lithium-ion batteries

High energy density lightweight batteries are required to revolutionize the future electronics and electric vehicles, thus, a lightweight and flexible material having the ability to carry high energy is the need of the hour. Herein, we have used laser-induced graphene foam (LIGF), grown at polyimide, directly as a self-sustaining binder-free anode material for lithium-ion batteries. The migration of the electrons on the LIGF grown finally on the one side of polyimide makes it possible to directly implant as a device, for a proof of concept, a folded specimen of LIGF is used as an anode. The initial areal capacity of ∼203 μAhcm−2 for as-grown LIGF increases to 280 μA hcm−2 upon annealing at 400 °C because of the improved graphitization. Stable rate performance is observed for 100 cycles at a current density of 0.1 mAcm−1 with average Coulombic efficiency of 99%. The electrochemical impedance spectroscopy hint that the conductivity of the annealed specimen is increased subsequently favors faster electronic flow on the one side of a non-conducting polymer. The present study paves a path towards future LIGF based lightweight lithium-ion batteries and also enables flexible wearable high energy density storage devices.

Flexible and Lightweight Lithium-Ion Batteries Based on Cellulose Nanofibrils and Carbon Fibers

Flexible, low-weight electrodes with integrated current collectors based on chopped polyacrylonitrile carbon fibers (CF) were produced using an easy, aqueous fabrication process, where only 4 wt% of TEMPO-oxidized cellulose nanofibrils (CNF) were used as the binder. A flexible full cell was assembled based on a LiFePO4 (LFP) positive electrode with a CF current collector and a current collector-free CF negative electrode. The cell exhibited a stable specific capacity of 121 mAh g−1 based on the LFP weight. The CF in the negative electrode acted simultaneously as active material and current collector, which has a significant positive impact on energy density. Stable specific capacities of the CF/CNF negative electrode of 267 mAh g−1 at 0.1 C and 150 mAh g−1 at 1 C are demonstrated. The LFP/CNF with CF/CNF, as the current collector positive electrode (LFP-CF), exhibited a good rate performance with a capacity of ~150 mAh g−1 at 0.1 C and 133 mAh g−1 at 1 C. The polarization of the LFP-CF electrode was similar to that of a commercial Quallion LFP electrode, while much lower compared to a flexible LFP/CNF electrode with Al foil as the current collector. This is ascribed to good contact between the CF and the active material.

Binder-free Li3V2(PO4)3/C membrane electrode supported on 3D nitrogen-doped carbon fibers for high-performance lithium-ion batteries

An in-situ prepared binder-free Li3V2(PO4)3/C membrane electrode supported on 3D N-doped carbon fibers (LVP/C@NCF) has been developed. The residual carbon in LVP/C@NCF consists of the pyrolytic carbon from glucose and the N-doped carbon fibers decomposed from filter paper. The former uniformly covers on the surface of LVP particles, while the latter is functioned as both a 3D conductive network and a current collector for LVP. Compared with the traditional LVP/C electrode supported on Al foil (LVP/C@Al), the LVP/C@NCF membrane electrode displays higher rate capability and better cycle stability. Especially, when cycled at a high rate of 10C, it still delivers a specific capacity as high as 107.6mAhg−1 with a very low capacity fading ratio of ~0.0048% per cycle after 1000 cycles. The excellent electrochemical performance is ascribed to the synergetic effect from the 3D effectively conductive network and the in-situ produced current collector of carbon fibers. The method of using filter paper as the source of carbon and current collector to prepare integrated membrane electrode may provide feasible and effective strategy to fabricate binder-free flexible and lightweight lithium ion batteries as well as sodium ion batteries.

Developing a light weight lithium ion battery – an effective material and electrode design for high performance conversion anodes

The process of lithium storage by conversion reaction is a subject of intense research in the field of lithium ion batteries as it opens up the possibility of storing more than one mole of lithium per formula unit, leading to very high storage capacities. For instance, lithium storage by conversion reaction in hematite (α-Fe2O3) results in high theoretical capacity of 1005 mAh g−1. Despite numerous attempts, the first cycle reversibility and cyclability achieved in this material have been disappointingly low. To overcome these limitations, we report here an effective “active material-electrode design” incorporating the following features: (i) well-connected active material particles; (ii) adequate active material surface area; (iii) strong particle-current collector adhesion and (iv) superior degree of electrode drying. Incorporating these features in α-Fe2O3 electrodes enhances its overall electrochemical performance. For the first time, a high first cycle reversibility of 90% is reported for lithium storage via conversion reaction in α-Fe2O3. The long term cyclability over 800 cycles demonstrated here is one of highest reported values for this material. Even at high current densities of 5.025 A g−1 (12 mins of charge/discharge), this tailored α-Fe2O3 delivers capacities (446 mAh g−1) in excess of graphite (372 mAh g−1). Most importantly, this anode material shows feasible operation in a full cell containing olivine LiMn0.8Fe0.2PO4 cathode. It is believed that this simple design approach could also be extended to other material systems such as phosphides, sulphides, nitrides and fluorides that store lithium via conversion mechanism.

The use of magnesium in lightweight lithium-ion battery packs

The analysis of recently announced battery packs for plug-in hybrid electric vehicles (PHEV) shows that the design of the series-parallel combinations is being over-complicated. The proven energy densities of lithium-ion cells from about 200 Wh/kg are being reduced to 90 Wh/kg. The majority of the weight increase seems to be for thermal management. Simpler battery pack designs based on electro-refining pot rooms using self-contained rectangular lithium-ion cells with air cooling inside of die-cast magnesium cell tanks would help avoid hauling dead weight in PHEV by providing considerable weight reduction.