Five energy storage battery technologies
News 2023年7月19日 41
Currently, the majority of electric vehicles (EVs) use lithium iron phosphate (LiFePO4) batteries. However, there are several major challenges to the widespread adoption of lithium-ion EVs:
(1) Price: Battery costs account for over half of an EV’s price. The latest Tesla models can cost over 700,000 yuan, making them unaffordable for the average person.
(2) Energy density: The theoretical specific energy of LiFePO4 batteries is 170 Wh/kg, while lithium cobalt oxide (LiCoO2) batteries have a theoretical specific energy of 200 Wh/kg. As a result, a significant portion of the EV’s payload is dedicated to the weight of the battery.
(4) Charging time: Fast charging can fill up to 80% in a matter of minutes but can damage the battery and poses some risks. Slow charging takes several hours to more than a dozen hours. Manufacturers typically recommend using slow charging mode.
The claim that “supercapacitors are expected to replace batteries” lacks reliable evidence. Although the introduction of graphene has significantly improved the energy density of supercapacitors, it still lags behind lithium-ion batteries. The energy density of supercapacitors is about 74 Wh/kg. However, the advantages of supercapacitors lie in their short charging time (seconds) and safety, making them suitable for auxiliary peak shaving and regenerative braking in electric vehicles.
Hydrogen-powered vehicle technology has made significant progress in recent years. The advantages are short refueling time and strong power. However, there are currently several challenges to address:
(1) Hydrogen production costs.
(2) Safety and high-strength hydrogen storage tanks.
(4)Pricing of refueling equipment. Safety is particularly important. Additionally, there is controversy surrounding the environmental impact of the hydrogen production process.
Flow batteries mainly include zinc-bromine flow batteries and vanadium flow batteries. Zinc-bromine flow batteries have a cost price of only about 1/5 of vanadium flow batteries, making them naturally advantageous.
(1) Price: The cost of zinc-bromine flow batteries is currently approaching that of lead-acid batteries and has the potential to be even lower. It is only about 1/5 of the cost of lithium-ion batteries.
(2) Energy density: The energy density can reach 430 Wh/kg, resulting in longer driving distances.
(3) Safety: Very safe.
(4) Charging time: Short charging time, fast charging mode does not harm the battery.
(5) In addition, zinc-bromine flow batteries have other advantages such as long lifespan, 100% depth of discharge, no self-discharge, high power capability, instant charging, and almost no requirements on the working environment.
The above data tells us that currently, zinc-bromine batteries are the best energy provider for electric vehicles. Let’s take a look at related information:
Zinc-bromine batteries are semi-depositional flow batteries. In the mid-1970s, someone changed the zinc-bromine battery’s static electrolyte to a flowing one, which suppressed the formation of zinc dendrites. As a result, zinc-bromine batteries evolved into deposition-type flow storage batteries and gradually commercialized.
Zinc-bromine batteries are semi-depositional, with an electrolyte of ZnBr2 water solution. Microporous separators are placed between the electrodes, and quaternary ammonium salt ligands are added to the electrolyte to prevent bromine diffusion to the negative electrode. Due to bromine’s strong corrosiveness, the electrodes are generally made of carbon-plastic composite materials with added high surface area carbon layers. To ensure uniform zinc plating and reduce the corrosion rate of zinc, the pH value of the solution needs to be strictly controlled. In addition, leakage current needs to be minimized through battery design or electrode protection methods. According to reports, zinc-bromine batteries with capacities ranging from 5 kWh to 45 kWh have been assembled in the United States and Japan for use as power sources in electric vehicles. ZBB Energy has designed a demonstration stack with a capacity of 400 kWh. In Japan, zinc-bromine stacks with capacities ranging from 1 MWh to 4 MWh have been assembled, with an overall energy efficiency of approximately 65.9%.
Zinc-bromine flow batteries have a theoretical open-circuit voltage of 1.82V, higher than that of vanadium flow batteries. Zinc-bromine batteries operate at near-room temperatures and do not require complex thermal control systems. Most of their components are made of polyethylene plastic, and their low-cost raw materials and manufacturing costs make them cost-competitive. These characteristics make zinc-bromine flow batteries one of the choices for large-scale energy storage batteries. Zinc-bromine batteries have been used for renewable energy generation storage.