Does aqueous battery have a competitive advantage

What is an aqueous battery

Aqueous battery refers to a secondary battery that uses water as the electrolyte. Compared with organic electrolyte batteries, aqueous batteries have the advantages of high safety, environmental friendliness, and high ionic conductivity.

Hence the surge of interest in aqueous battery in the pursuit of more reliable and affordable energy storage solutions. The current commercial aqueous batteries are used in the fields of transportation and power grid storage, but cannot achieve the required energy density and cycle life. This constraint will change with the discovery of new material systems and the development of battery design strategies.

Advantages and disadvantages of aqueous battery

Aqueous batteries are generally considered safe, reliable and affordable, an advantage compared to lithium-ion batteries, which do not catch fire when they use flammable organic solvents in their electrolyte solutions. Conventional aqueous battery use electrolytes that typically contain more than 70% water by weight and are therefore generally non-flammable.

Advantage

Low cost： the argument for the low cost of aqueous battery stems from at least three factors: cheap raw materials, minimal requirements for the manufacturing environment, and limited demand for battery management and protection systems.

Safety and reliability： while an aqueous battery may not catch fire, an aqueous battery is still vulnerable to mishandling and can experience catastrophic events such as explosions. Overcharging is an incorrect operation that irreversibly decomposes the electrolyte and degrades battery performance;

Fast kinetics: Due to high ion dissociation and low viscosity, aqueous electrolyte solutions are generally more conductive than non-aqueous electrolyte solutions under equivalent conditions.

Disadvantages

Narrow electrochemical stability window: Water has a narrow thermodynamic electrochemical stability window of 1.23 V, beyond which water is anodically oxidized to oxygen.

Aggressiveness of aqueous solutions: The high polarity and strong coordination ability of water make it an excellent solvent for dissolution and dissociation. These properties make water a good ingredient for electrolytes, but a problem for many battery components.

Lithium ion battery vs aqueous battery

The most common lithium-ion batteries in life are lithium iron phosphate batteries and ternary lithium battery, which have the advantages of high energy density, small size, light weight, and long service life. However, lithium is a very active metal that can react immediately when it encounters a very small amount of water. Lithium-ion batteries can usually only be produced in strictly controlled dry rooms;

Lithium batteries are also very sensitive to temperature, and usually can only work stably in the range of -20 to 50°C near the room temperature. In order to maintain the health of the battery during use, it is also necessary to operate according to the temperature requirements.

Faced with unresolved safety issues, scientists have turned their attention to aqueous electrolytes. Compared with the organic electrolytes currently used in lithium-ion batteries, the “safety factor” of aqueous battery electrolytes is much higher. It is not difficult to understand that the aqueous battery solution is not flammable, and you want to use the battery under extreme conditions, which greatly reduces the risk of battery combustion and explosion.

High safety, easy preparation conditions, and low cost have always been the eye-catching advantages of aqueous battery electrolytes. But the shortcomings of aqueous battery are also prominent – the narrow voltage window limits the energy density of the battery.

For example, the voltage of conventional aqueous battery, such as lead-acid batteries and nickel-cadmium batteries, is 1-2 V, and the energy density is only 30-50 Wh/kg, which is far lower than that of organic lithium-ion batteries (3-4 V, 150-250 Wh /kg). The energy density of aqueous battery is less than 1/3 of lithium-ion batteries, so batteries using aqueous electrolytes do not have a competitive advantage in the market.

Future development of aqueous battery

Although it is likely that modern tool and battery designs have eliminated the limitations of traditional aqueous battery, the trade-offs introduced cannot be ignored. Most water-poor electrolytes and selective membranes are still expensive, weakening the cost advantage of aqueous battery.

The complexity of making a multi-chamber battery and the materials used for the anode, such as lithium metal, add to the cost. The ionic conduction between the poor aqueous electrolyte and the interface is comparable to that of non-aqueous electrolytes, but much lower than conventionally expected for aqueous systems. The implementation of the oxygen cycle appears to be problematic in some battery configurations and requires robust battery management.

Non-flammability, the only advantage of traditional aqueous battery, has been largely preserved, and electrolytes, membranes, and electrodes all need continuous improvement for commercially impactful modern aqueous battery to emerge. In addition to the previously outlined strategies, the following urgent but underexplored research directions: electrolyte-related issues, tailored membranes, and practical dual-ion batteries.