Production technology for automotive lithium-ion battery (LIB) cells and packs has improved considerably in the past five years. However, the transfer of developments in materials, cell design and processes from lab scale to production scale remains a challenge due to the large number of consecutive process steps and the significant impact of material properties, electrode compositions and cell designs on processes. This requires an in-depth understanding of the individual production processes and their interactions, and pilot-scale investigations into process parameter selection and prototype cell production. Furthermore, emerging process concepts must be developed at lab and pilot scale that reduce production costs and improve cell performance. Here, we present an introductory summary of the state-of-the-art production technologies for automotive LIBs. We then discuss the key relationships between process, quality and performance, as well as explore the impact of materials and processes on scale and cost. Finally, future developments and innovations that aim to overcome the main challenges are presented. The battery manufacturing process significantly affects battery performance. This Review provides an introductory overview of production technologies for automotive batteries and discusses the importance of understanding relationships between the production process and battery performance.

Current status and challenges for automotive battery production technologies

Topology optimization has become an effective tool for least-weight and performance design, especially in aeronautics and aerospace engineering. The purpose of this paper is to survey recent advances of topology optimization techniques applied in aircraft and aerospace structures design. This paper firstly reviews several existing applications: (1) standard material layout design for airframe structures, (2) layout design of stiffener ribs for aircraft panels, (3) multi-component layout design for aerospace structural systems, (4) multi-fasteners design for assembled aircraft structures. Secondly, potential applications of topology optimization in dynamic responses design, shape preserving design, smart structures design, structural features design and additive manufacturing are introduced to provide a forward-looking perspective.

Topology Optimization in Aircraft and Aerospace Structures Design

Lithium-ion batteries are currently the most advanced electrochemical energy storage technology due to a favourable balance of performance and cost properties Driven by forecasted growth of the electric vehicles market, the cell production capacity for this technology is continuously being scaled up However, the demand for better performance, particularly higher energy densities and/or lower costs, has triggered research into post-lithium-ion technologies such as solid-state lithium metal, lithium–sulfur and lithium–air batteries as well as post-lithium technologies such as sodium-ion batteries Currently, these technologies are being intensively studied with regard to material chemistry and cell design In this Review, we expand on the current knowledge in this field Starting with a market outlook and an analysis of technological differences, we discuss the manufacturing processes of these technologies For each technology, we describe anode production, cathode production, cell assembly and conditioning We then evaluate the manufacturing compatibility of each technology with the lithium-ion production infrastructure and discuss the implications for processing costs Tremendous research progress has been made in the development of post-lithium-ion batteries (PLIBs), yet there is little discussion on the manufacturing of these upcoming technologies In this Review, the authors survey the current production status of several representative PLIBs and offer an industrial-scale manufacturing outlook

Post-lithium-ion battery cell production and its compatibility with lithium-ion cell production infrastructure

Emerging trends in manufacturing such as light weighting, increased performance and functionality increases the use of multi-material, hybrid structures and thus the need for joining of dissimilar materials. The properties of the different materials are jointly utilised to achieve product performance. The joining processes can, on the other hand be challenging due to the same different properties. This paper reviews and summarizes state of the art research in joining dissimilar materials. Current and emerging joining technologies are reviewed according to the mechanisms of joint formation, i.e.; mechanical, chemical, thermal, or hybrid processes. Methods for process selection are described and future challenges for research on joining dissimilar materials are summarized.

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Joining of dissimilar materials

This paper investigates comprehensive knowledge regarding joining CFRP and aluminium alloys in available literature in terms of available methods, bonding processing and mechanism and properties. The methods employed comprise the use of adhesive, self-piercing rivet, bolt, clinching and welding to join only CFRP and aluminium alloys. The non-thermal joining methods received great attention though the welding process has high potential in joining these materials. Except adhesive bonding and welding, other joining methods require the penetration of metallic pins through joining parts and therefore, surface preparation is unimportant. No model is found to predict the properties of jointed structures, which makes it difficult to select one over another in applications. The choice of bonding methods depends primarily on the specific applications. The load-bearing mechanism of bolted joints is predominantly the friction that is the first stage resistance. Hybrid joints performance is enhanced by combining rivets, clinch or bolts with adhesives.

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Joining of carbon fibre reinforced polymer (CFRP) composites and aluminium alloys-A review

Fixture design is an important consideration in all manufacturing operations. Central to this design is selecting and positioning the locating points. While substantial literature exists in this area, most of it is for prismatic or solid workpieces. This paper deals with sheet metal fixture design. An ''N-2-1'' locating principle has been proposed and verified to be valid for deformable sheet metal parts as compared to the widely accepted 3-2-1 principle for rigid bodies. Based on the N-2-1 principle, algorithms for optimal fixture design are presented using finite element analysis and nonlinear programming methods to find the best N locating points such that total deformation of the deformable sheet metal is minimized. A simulation package called OFixDesign is introduced and numerical examples are presented to validate the N-2-1 principle and optimal sheet metal fixture design approach.

Deformable Sheet Metal Fixturing: Principles, Algorithms, and Simulations

Deformable sheet metal fixturing : Principles, algorithms, and simulations

Fixtures are used to locate and hold workpieces during manufacturing. Because workpiece surface errors and fixture set-up errors (called source errors) always exist, the fixtured workpiece will consequently have position and/or orientation errors (called resultant errors). In this paper, we develop a variational method for robust fixture configuration design to minimize workpiece resultant errors due to source errors. We utilize both first-order and second-order workpiece geometry information to deal with two types of source errors, i.e., infinitesimal errors and small errors. Using the proposed variational approach, other fundamental fixture design issues, such as deterministic locating and total fixturing, can be regarded as integral parts of the robust design. Closed-form analytical solutions are derived and numerical examples are shown. By employing the nonlinear programming technique, simulation software called RFixDesign is developed. This paper presents a new procedure for robust fixture configuration design that contributes especially to fixture designs where deformation is not influential.

A Variational Method of Robust Fixture Configuration Design for 3-D Workpieces

Automotive battery packs for electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (PHEV) typically consist of a large number of battery cells. These cells must be assembled together with robust mechanical and electrical joints. Joining of battery cells presents several challenges such as welding of highly conductive and dissimilar materials, multiple sheets joining, and varying material thickness combinations. In addition, different cell types and pack configurations have implications for battery joining methods. This paper provides a comprehensive review of joining technologies and processes for automotive lithium-ion battery manufacturing. It details the advantages and disadvantages of the joining technologies as related to battery manufacturing, including resistance welding, laser welding, ultrasonic welding and mechanical joining, and discusses corresponding manufacturing issues. Joining processes for electrode-to-tab, tab-to-tab (tab-to-bus bar), and module-to-module assembly are discussed with respect to cell types and pack configuration.Copyright © 2010 by ASME and General Motors

Joining Technologies for Automotive Lithium-Ion Battery Manufacturing: A Review

Manufacturing of lithium-ion battery packs for electric or hybrid electric vehicles requires a significant amount of joining such as welding to meet desired power and capacity needs. However, conventional fusion welding processes such as resistance spot welding and laser welding face difficulties in joining multiple sheets of highly conductive, dissimilar materials with large weld areas. Ultrasonic metal welding overcomes these difficulties by using its inherent advantages derived from its solid-state process characteristics. Although ultrasonic metal welding is well-qualified for battery manufacturing, there is a lack of scientific quality guidelines for implementing ultrasonic welding in volume production. In order to establish such quality guidelines, this paper first identifies a number of critical weld attributes that determine the quality of welds by experimentally characterizing the weld formation over time. Samples of different weld quality were cross-sectioned and characterized with optical microscopy, scanning electronic microscopy (SEM), and hardness measurements in order to identify the relationship between physical weld attributes and weld performance. A novel microstructural classification method for the weld region of an ultrasonic metal weld is introduced to complete the weld quality characterization. The methodology provided in this paper links process parameters to weld performance through physical weld attributes.Copyright © 2012 by ASME and General Motors

Wayne W. Cai

Papers

Deformable Sheet Metal Fixturing: Principles, Algorithms, and Simulations

Deformable sheet metal fixturing : Principles, algorithms, and simulations

A Variational Method of Robust Fixture Configuration Design for 3-D Workpieces

Joining Technologies for Automotive Lithium-Ion Battery Manufacturing: A Review

Characterization of Joint Quality in Ultrasonic Welding of Battery Tabs