Early attempts to develop water-based lithium batteries faced significant challenges that prevented their commercial success. These systems, which used aqueous electrolytes instead of organic solvents, promised advantages in cost, safety, and environmental friendliness. However, fundamental electrochemical incompatibilities led to poor cycle life, low energy density, and safety hazards that made them impractical for widespread use. The primary issues revolved around hydrogen evolution, electrode corrosion, and the narrow electrochemical stability window of water, which severely limited the battery's performance and reliability.

The most critical limitation of water-based lithium batteries is the narrow voltage window imposed by the thermodynamic stability of water. Water electrolysis occurs at voltages beyond 1.23 V under standard conditions, splitting into hydrogen and oxygen. In practice, due to overpotentials at the electrodes, the practical stability window extends slightly, but it remains insufficient for high-energy-density battery chemistries. This constraint severely limits the selection of electrode materials, as most high-voltage lithium-ion cathode materials cannot be used without triggering water decomposition. For example, lithium cobalt oxide, a common cathode material, operates at potentials well above the stability limit of water, leading to rapid electrolyte breakdown and gas evolution.

Hydrogen evolution at the anode presented another major obstacle. In aqueous systems, lithium metal anodes react violently with water, producing hydrogen gas and lithium hydroxide. This reaction is highly exothermic and poses significant safety risks, including the potential for explosions. Even when using alternative anode materials such as lithium titanate or carbon-based compounds, the reduction of water molecules at low potentials remains a persistent issue. The continuous generation of hydrogen gas not only reduces coulombic efficiency but also increases internal pressure within the cell, leading to mechanical stress and potential rupture.

Corrosion of electrode materials further exacerbated the challenges. Many transition metal oxides used in cathodes are unstable in aqueous environments, dissolving over time or undergoing phase transitions that degrade performance. For instance, manganese-based cathodes suffer from manganese dissolution, which leads to capacity fade and electrode structural collapse. Similarly, aluminum current collectors corrode in aqueous electrolytes, particularly at high potentials, forming resistive oxide layers that increase internal resistance. The dissolution of electrode materials also contaminates the electrolyte, accelerating side reactions and reducing cycle life.

The limited solubility of lithium salts in water introduced additional complications. Unlike organic electrolytes, which can dissolve high concentrations of lithium salts such as LiPF6 or LiTFSI, aqueous electrolytes struggle to achieve sufficient ionic conductivity without excessive salt concentrations. High salt concentrations can lead to increased viscosity, reduced lithium-ion mobility, and precipitation of salts at low temperatures. Furthermore, the solvation structure of lithium ions in water differs from that in organic solvents, affecting ion transport and intercalation kinetics at the electrodes.

Attempts to mitigate these issues included using pH-buffered electrolytes or protective coatings on electrodes. However, these solutions often introduced new problems. Alkaline electrolytes reduced hydrogen evolution but accelerated corrosion of aluminum current collectors. Acidic electrolytes improved cathode stability but increased dissolution of anode materials. Protective coatings, such as conductive polymers or ceramic layers, added manufacturing complexity and often reduced energy density by introducing inactive materials into the cell.

The low energy density of aqueous lithium batteries compared to their non-aqueous counterparts made them commercially unviable for most applications. The combination of voltage limitations, low practical capacity, and poor cycle life resulted in systems that could not compete with organic electrolyte-based lithium-ion batteries. Even in applications where safety and cost were prioritized over energy density, such as stationary storage, the poor longevity and maintenance requirements outweighed the benefits of aqueous systems.

Safety hazards remained a persistent concern. The generation of hydrogen and oxygen gases during operation created risks of combustion, particularly in sealed cells. While venting mechanisms could alleviate pressure buildup, they introduced reliability issues and environmental sensitivity. Thermal management also proved more challenging than in non-aqueous systems, as the high heat capacity of water could not prevent localized overheating during fast charging or short circuits.

Despite these challenges, research into aqueous batteries continues, focusing on new electrode materials and electrolyte formulations that circumvent these limitations. Modern approaches include hybrid systems that combine aqueous and non-aqueous electrolytes or use highly concentrated salt solutions to expand the voltage window. However, the historical failures of early water-based lithium batteries underscore the importance of electrochemical compatibility in battery design. The lessons learned from these attempts continue to inform the development of safer, more sustainable energy storage technologies.