energies Review Challenges of Fast Charging for Electric Vehicles and the Role of Red Phosphorous as Anode Material: Review Hong Zhao 1,2, Li Wang 2 , Zonghai Chen 3 and Xiangming He 2,* 1 School of Materials Science and Energy Engineering, Foshan University, Foshan 528225, China; [email protected] 2 Institute of Nuclear and New Energy, Tsinghua University, Beijing 100084, China; [email protected] 3 Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL 60439, USA; [email protected] * Correspondence: [email protected]; Tel.: +86-10-6279-4226 Received: 11 September 2019; Accepted: 8 October 2019; Published: 15 October 2019 Abstract: Electric vehicles (EVs) are being endorsed as the uppermost successor to fuel-powered cars, with timetables for banning the sale of petrol-fueled vehicles announced in many countries. However, the range and charging times of EVs are still considerable concerns. Fast charging could be a solution to consumers’ range anxiety and the acceptance of EVs. Nevertheless, it is a complicated and systematized challenge to realize the fast charging of EVs because it includes the coordinated development of battery cells, including electrode materials, EV battery power systems, charging piles, electric grids, etc. This paper aims to serve as an analysis for the development of fast-charging technology, with a discussion of the current situation, constraints and development direction of EV fast-charging technologies from the macroscale and microscale perspectives of fast-charging challenges. If the problem of fast-charging can be solved, it will satisfy consumers’ demand for 10-min charging and accelerate the development of electric vehicles. This paper summarized the development statuses, issues, and trends of the macro battery technology and micro battery technology. It is emphasized that to essentially solve the problem of fast charging, the development of new battery materials, especially anode materials with improved lithium ion diffusion coefficients, is the key. Finally, it is highlighted that red phosphorus is one of the most promising anodes that can simultaneously satisfy the double standards of high-energy density and fast-charging performance to a maximum degree. Keywords: fast-charging; electric vehicles; infrastructure; electrode materials; li-ion batteries 1. Introduction Electric vehicles (EVs) are receiving increasing attention because they offer the potential benefits of reducing dependence on fossil fuels and improving urban air quality, thus helping the transition to more sustainable and eco-friendly travel [1,2]. With the continuous progress of batteries, motors, and electrical control technologies; and the increasing development of informationization, network connection, and intellectualization for pure EVs, the cost performance of EVs will reach or exceed that of conventional fuel vehicles by 2025 at the latest. However, for petrol vehicles, filling with fuel only requires 2 to 5 min, whereas for common EVs on the market, general charging requires 6–8 h to achieve fully charged batteries. Such a long charging time is barely acceptable for ordinary consumers with EVs as commuting tools, but it is totally unacceptable when using EVs as operating vehicles, such as taxis and logistics vehicles. Usually, a ’10-min full charge’ is the ideal appeal for users. Fast-charging can be achieved in two typical ways, namely a high voltage or high current mode. However, if the charging Energies 2019, 12, 3897; doi:10.3390/en12203897 www.mdpi.com/journal/energies Energies 2019, 12, 3897 2 of 23 Energies 2019, 12, x FOR PEER REVIEW 2 of 23 voltage is increased greatly, the insulation level of the vehicle must be upgraded, and the requirements componentson the quality for of the electronic vehicle componentsshould be high, for resulting the vehicle in shouldextra cost. be high,If the resultingcurrent is in increased extra cost. greatly, If the itcurrent will inevitably is increased lead greatly, to a heating it will inevitably problem. lead Whether to a heating high voltage problem. or Whetherhigh current, high voltagevehicle orbattery high technologycurrent, vehicle not only battery need technology to meet the not electrochemi only need tocal meet and the thermal electrochemical demands of and fast-charging thermal demands but also of thefast-charging battery pack, but alsocharging the battery pile, pack,and power charging grid pile, must and be power capable grid mustof hand beling capable the ofhigh handling charging the powerhigh charging [3]. Thus, power fast-charging [3]. Thus, is fast-charging a complicated is aand complicated systematized and technology. systematized technology. Fast-charging has has attracted attracted people's people’s attention attention and and a series a series of review of review articles articles about about enabling enabling fast chargingfast charging have havebeen beenreported. reported. They focused They focused on vehicle on vehicle[4], battery [4], technology battery technology gap [5], gapthermal [5], managementthermal management [6], and [infrastructure/economic6], and infrastructure/economic considerations considerations [7], respectively. [7], respectively. Also, there Also, is some there academicis some academic review reviewfocused focused on rational on rational material material design design [8], [ 8which], which presents presents the the state-of-the-art developments in ultrafast charging LIBs by the rationalrational designdesign ofof materials.materials. It is especially worth mentioning thatthat a a recent recent review review study study from from Professor Professor Cuiyi Cuiyi discussed discussed the challenges the challenges and future and research future researchdirections directions towards fast towards charging fast at charging the level ofat batterythe level materials, of battery charge materials, transfer, charge and characterization transfer, and characterizationtechniques for battery techniques designs for [9 ].battery Based designs on current [9]. literature, Based on herein, current we literature, not only discussherein, thewe issue,not only but discussalso the the solution issue, to but EV also fast-charging. the solution We to reorganize EV fast-charging. the utility-scale We reorganize battery storage the utility-scale system into battery three parts:storage a system battery into system, three a parts: charging a battery pile system, system, and a charging a power pile grid, system, as shown and in a power Figure 1grid,[ 10 ].as For shown the inconvenience Figure 1 [10]. of the For following the convenience review, weof the classified followi theng batteryreview, system we classified of the vehicle, the battery charging system pile, of andthe powervehicle, grid charging as macro pile, battery and power technology grid as and macro the battery battery technology cell, including and the the cell battery materials, cell, including as micro thebattery cell technology.materials, as The micro development battery technology. statuses, issues, The development and trends of statuses, the macro issues, battery and technology trends of andthe macromicro batterybattery technology technology will and be summarized micro battery as follows. technology In particular, will be the summarized view expressed as infollows. this paper In particular,is that lithium-ion the view batteries expressed can in be this quickly paper charged is that lithium-ion to a certain extentbatteries through can be macroscopic quickly charged charging to a certaintechnology, extent but through it is currently macroscopic hard tocharging achieve technology, real fast charging, but it is which currently depends hard to on achieve a breakthrough real fast charging,of battery which materials. depends Moreover, on a breakthrough it is highlighted of battery that red materials. phosphorus Moreover, is a promising it is highlighted anode thatthat canred phosphorussimultaneously is satisfya promising the double anode standards that can of high-energy simultaneously density satisfy and fast-charging the double performance standards of to high-energya maximum degree.density and fast-charging performance to a maximum degree. Figure 1. Overview to functional blocks of a utility-scale battery storage system [4]. Figure 1. Overview to functional blocks of a utility-scale battery storage system [4]. 2. Macroscopic Challenges in EV Fast Charging 2.1. Consideration in the Battery Systems of EVs 2.1.1. Battery/Battery Pack Design To support the fast-charging performance of the cell, considerable effort goes into the design of a single cell battery pack. Generally, the fast-charging performance of a single cell can be improved Energies 2019, 12, 3897 3 of 23 2. Macroscopic Challenges in EV Fast Charging 2.1. Consideration in the Battery Systems of EVs 2.1.1. Battery/Battery Pack Design To support the fast-charging performance of the cell, considerable effort goes into the design of a single cell battery pack. Generally, the fast-charging performance of a single cell can be improved by adding more conductive agent to the electrode [11], reducing the loading of the electrode material (thinner coating), using a thicker collector, adjusting the suitable tab position, retaining a larger electrode porosity [12,13], ensuring less electrode bending [14], etc. These methods can improve the kinetic and electrical properties and reduce the internal resistance of cells. A study analyzed the internal resistance of electrodes with various thicknesses ranging from 10 µm to