New Battery Solves the Charging Problem of Electric Vehicle

"Charging anxiety" and "mileage anxiety" are a major obstacle to the large-scale industrialization of pure electric vehicles. At the recent 2019 world new energy vehicle conference, a technology called "high specific energy fast charging lithium ion battery" won the global new energy vehicle innovation technology award. This technology breaks through the technical bottleneck that the graphite system cannot be charged quickly. On the basis of maintaining the advantages of high energy density, high safety and long life, it can complete 100% charging within 15 minutes to ensure the 300 km range of electric vehicles.

What is the secret of this technology? How can new energy users feel the convenience of "charging for five minutes and talking for two hours" like mobile phones while realizing the rapid charging of electric vehicles? As we all know, for pure electric vehicles, the charge and discharge performance of battery system is an important index to determine the actual use effect of vehicles. High energy density and fast charging capability are not only the technical direction of power battery manufacturers, but also the core field of new energy technology.

Lithium ion battery is also called rocking chair battery. Both ends of the rocking chair are the two poles of the battery. Lithium ions run back and forth at both ends of the rocking chair. During charging, lithium ions move from the positive electrode of the battery through the electrolyte to the negative electrode. The graphite as the negative electrode has a layered structure, and lithium ions are embedded into the graphite through the interlayer. The more lithium ions are embedded, the higher the charging capacity.

A key index to measure the charging efficiency of electric vehicles is the charge discharge ratio (c). Charge discharge ratio can be simply understood as the rate of charge and discharge. The charge discharge ratio of lithium-ion battery determines how fast we can store a certain amount of energy in the battery or release the energy in the battery. For example, when a battery with a rated capacity of 100 a is charged with 20, its discharge rate is 0.2C, and the capacity used is discharged in 1 hour, which is called 1C discharge; After 5 hours of discharge, it is called 0.2C discharge.

It is generally believed in the industry that the fast charging of electric vehicles refers to the charging mode with a charging rate greater than 1.6c, that is, the technology that takes less than 30 minutes from 0% charging to 80%. As the name suggests, in order to shorten the charging time, it is necessary to continuously improve the charge discharge ratio. The core of fast charging technology is to accelerate the movement of lithium ions between positive and negative electrodes through chemical system and design optimization. However, the speed is not enough when developing fast charging technology.

During fast charging, lithium ions need to be accelerated and instantaneously embedded into the negative electrode. This is a great challenge to the ability of the negative electrode to quickly receive lithium ions. For the battery of ordinary chemical system, lithium precipitation and other by-products will appear on the negative electrode during fast charging, which will affect the circulation and stability of the cell. Only the negative electrode material that can withstand fast charging and high current can be used to achieve fast charging.

At present, lithium titanate and amorphous carbon are widely used as negative active materials in the industry in order to realize rapid charging. However, lithium titanate and amorphous carbon inevitably have the defects of serious insufficient energy density and high cost in practical application. The design of increasing the amount of conductive materials will also affect the energy density of the cell. "In recent years, some manufacturers have begun to explore graphite as an active material, but the problem faced by graphite as a fast charging material is how to quickly release lithium electrons from the positive electrode and then quickly enter from the negative electrode."

Graphite is more like a highway. Although the energy density is higher, lithium electrons can only pass in sequence. In other words, graphite is not naturally suitable for fast charging technology. But we use technology to break through the bottleneck of material itself. Its killer mace is' fast ion ring 'and' superelectron network '. Taking graphite as the main material of negative electrode, we creatively use pore optimization and 'fast ion ring' technology to create a circle of high-speed channel on the surface of graphite, so that lithium ions can be quickly embedded in any position of graphite, which greatly improves the embedding speed of lithium ions in graphite negative electrode. In addition, the modified graphite takes into account the characteristics of super fast charging and high energy density, No by-products will appear on the negative electrode during fast charging, which will affect the circulation and stability of the cell.

In addition, the technical team developed the "super electronic network" technology to modify the cathode material, combined with the crystal orientation and capacity excess coefficient of the positive and negative electrode pieces and other design parameters, so as to optimize the dynamic performance of electrolyte and positive and negative electrodes, so as to achieve the optimal matching of chemical system and battery design parameters. Generally speaking, the "fast ion ring" and the "superelectron network" act on the negative electrode and the positive electrode respectively to establish a fast channel for a large number of lithium ions to flow into the negative electrode at the same time and improve the diffusion rate of lithium ions.

In addition, in terms of mechanical part design, the team creatively simplified the design of the top cover of the battery cell, set the electrode terminal on the side of the top cover plate, reduce the terminal thickness, significantly reduce the internal resistance, effectively control the calorific value of fast charging, ensure the reliability of fast charging and increase the energy density by more than 5%. Our fast charging technology has 4c-5c fast charging capacity and realizes 10-15 minute fast charging. Compared with the fast charging system of lithium titanate negative electrode, it has obvious energy density and cost advantages. Compared with other fast charging technologies in the industry that also use graphite as negative electrode, it can increase the charging speed by 20% - 30% under the condition of maintaining the same battery energy density, It has better cycle and weather resistance.

At present, the super iron lithium fast charging battery developed by Ningde times with fast charging graphite as the main cathode material has been applied to more than 5000 electric buses. The buses are in good operation and have been highly praised by vehicle enterprises and bus users. The battery has also been rated as the "best reputation battery for new energy public transportation" by the Ministry of transportation.

In addition to the energy density, the battery has great advantages. In terms of cycle life, taking the bus with harsh application conditions as an example, the average number of full discharge times per day is about 2 times. After rough calculation, it can meet the 8-year operation demand, and the battery cycle needs more than 5600 times. The cycle life of super iron lithium battery cell can reach 10000 times, which can not only fully meet the operation needs of electric vehicles, but also be used for echelon utilization such as energy storage after electric vehicles are retired, creating more economic value.

In order to ensure the safety and reliability of the fast charging core, we have also developed special technology to identify the "healthy charging range" of the chemical system under different temperatures and SOC States, and then carry out fast charging within this "healthy charging range", which can not only realize fast charging, but also prevent the battery from being damaged by fast charging Long cycle, safety and reliability.

In terms of weather resistance, in order to meet the requirements of low-temperature charging in winter in the north and high-temperature working conditions in summer in the south, the technical team has specially developed an efficient thermal management system to ensure that the battery is in a reasonable temperature range. It can quickly heat the cell at low temperature, and the fast charging mode can be started when the temperature meets the requirements; At high temperature, the system will cool the cell and really achieve "all climate" fast charging.

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Envoy, an Electric Vehicle Start-up, Announced the Completion of a $81 Million Financing
According to foreign media reports, Evoy, an electric vehicle start-up, announced that it had completed a round of financing worth US $81 million, including a round of financing worth US $11 million, led by shell ventures and building ventures, one of the world's largest energy companies, and the Los Angeles clean technology incubator of electric equipment and Goodyear ventures (Los Angeles clean tech incubator) and groundbreak ventures participated in the investment.Apart from the US $11 million in round a financing, the remaining US $70 million is raised through bonds issued by the multinational Macquarie services. This round of financing will help envoy expand its business in the United States and conduct business with a local automobile industry company in Israel. Israeli angel investors Rony zarom, Ronen Jaffa, Assaf Topaz and Daniel Nazarian also participated in envoy's seed round financing.Envoy was founded in 2017 by Israeli entrepreneur ori sage and Jewish American partner ARIC ohana. In recent years, sage has lived in the United States and has been an active technology entrepreneur for the past 20 years. In 2000, he founded smart IL with his brother Tamir, which was acquired and merged into the American company smart online in 2004.When sagie invested in real estate in the United States, she met ohana and made several investments together. Envoy was founded because they have accumulated experience in science and technology projects, aiming to provide better life experience for tenants.As part of the complex, envoy mainly provides community-based shared electric vehicles for apartments, hotels and workplaces on demand. The services provided include fleet, charging station, driver insurance and a platform for managing the fleet, which includes mobile applications for end users to book and use vehicles.The company's technology also includes an engine that can collect and read data, analyze the use of vehicles in real time, collect vehicle data, driver behavior, relevant travel demand and charging information. After analyzing the data, it can provide micro travel solutions, and make suggestions according to the demand and use of each facility to increase vehicles in the fleet.According to envoy, the integration of its technology into apartment facilities can add value to apartment owners when renting houses. In addition, the service can also provide owners with additional income channels through the sharing mode of envoy products. The cost of renting vehicles is 15 cents per minute, so they can choose to rent more advanced vehicles, but they also need to pay an additional fee.At present, envoy has established cooperation with more than 100 real estate companies in the United States and signed long-term contracts. Envoy will be responsible for managing and supplying all travel and charging infrastructure required by customers, and sharing data collected from vehicles with real estate companies.
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