With the rapid development and grid connection of new energy generation like wind and solar power, the intermittency and volatility of these sources are bound to cause short - term energy imbalances in the grid. Thus, employing energy - storage technology for grid - frequency regulation is gaining in importance.

As a new - type electrochemical energy - storage battery, vanadium flow batteries (VFBs) have many merits. Their power and capacity are independent and they are highly flexible. They also feature a fast response, good safety, and a long lifespan. So, they are widely regarded.

The performance of VFBs is affected by many factors. Coulombic efficiency (CE), voltage efficiency (VE), and energy efficiency (EE) are key indicators for evaluating their performance. CE reflects charge - transfer reversibility, VE shows polarization losses, and EE is a comprehensive indicator of energy losses. They are all crucial for assessing the overall performance of a battery. This paper explores improving these efficiencies of VFBs through material optimization, structural improvements, and better battery - management systems, so VFBs can better meet new energy - generation needs and ensure grid stability.

**Coulombic Efficiency**: It mirrors the reversibility of charge transfer in a flow battery. The main factors influencing CE are as follows:

**Electrode Surface Reactions**: Electrode surface side reactions are a direct cause of the decline in CE. For instance, hydrogen evolution (HER) and oxygen evolution reactions (OER) consume active substances (such as vanadium ions) in the electrolyte, particularly under extreme potentials or high current densities. Moreover, impurities in the electrode or electrolyte (like Fe³⁺, Cl⁻) can trigger non - target redox reactions, further reducing charge utilization.

**Separator Performance**: The selectivity of the separator significantly impacts CE. Insufficient selectivity leads to the cross - membrane migration of active substances (e.g., vanadium ion permeation), causing self - discharge. Over time, separator aging or mechanical damage can worsen cross - contamination.

**Electrolyte Properties and Operating Conditions**: High - concentration electrolytes, while enhancing capacity, may accelerate side reactions. Low - concentration electrolytes lower active - substance utilization. The chemical stability of the electrolyte (e.g., the redox reversibility of V²⁺/V³⁺) and pH directly affect side - reaction rates. Temperature management is also key, as high temperatures can accelerate active - substance decomposition, while low temperatures can hinder electrode - reaction kinetics, preventing full participation of active substances in charging/discharging.

**Voltage Efficiency**: It is constrained by ohmic, activation, and concentration polarization. The details are:

**Ohmic Polarization**: It arises from the internal resistance of the battery, including insufficient electrolyte conductivity (e.g., low sulfuric acid concentration), separator resistance (the high cost and low conductivity of Nafion membranes), and electrode/current - collector contact resistance (the match between carbon felt compression rate and flow - channel design).

**Activation Polarization**: Closely related to electrode - reaction kinetics, unmodified carbon felt has poor catalytic activity for the VO²⁺/VO₂⁺ redox couple. Surface modification (e.g., nitrogen doping, metal - oxide loading) can lower the reaction energy barrier.

**Concentration Polarization**: Mainly caused by mass - transfer limitations in the electrolyte. Low flow rates or flawed flow - field designs (e.g., flow - channel dead zones) can increase the concentration gradient of active substances at the electrode surface. In addition, irreversible reactions like oxygen evolution during charging can worsen energy loss. In engineering practice, optimizing bipolar - plate flow - field designs (e.g., choosing serpentine or interleaved flow channels) can enhance current - distribution uniformity and reduce polarization losses.

**Energy Efficiency**: As the product of CE and VE, it requires optimizing charge transfer and energy - loss synergy. System operating parameters greatly impact EE. High current densities boost power density but can increase polarization and side reactions. Electrolyte flow rate must balance concentration polarization and pumping energy consumption. For example, pump losses in VFBs typically account for 10% - 15% of total energy consumption. Using low - viscosity electrolytes or optimizing flow - channel designs can cut parasitic losses. Temperature management must balance multiple objectives. Heating reduces electrolyte viscosity and speeds up reactions but promotes side reactions and active - substance degradation. Cycle - life decay also matters. Over time, issues like membrane swelling and electrode corrosion can lower EE. Studies show dynamic adjustment of flow rate based on state - of - charge (SOC) by a battery - management system (BMS) can raise EE by 5% - 8%.

To optimize flow - battery efficiency, a multi - dimensional collaborative innovation system covering materials, structure, and operation should be built. In basic materials, developing new electrolytes with high stability and wide temperature adaptability is key to overcoming technical bottlenecks, focusing on solving active - substance degradation and side - reaction suppression. For key components, advancing the continuous manufacturing of low - ionic - impedance, high - selectivity ion - exchange membranes will directly affect the scaling - up cost and cycle life of battery systems. In operation control, deeply integrating adaptive algorithms with condition - sensing technologies to create intelligent management systems with dynamic optimization capabilities can significantly enhance energy - conversion efficiency and system reliability, driving flow - battery technology to achieve safety and economic breakthroughs.

Product Series：