With the burgeoning expansion of electric vehicles (EVs), the utilization of lithium-ion batteries in various vehicles—ranging from four-wheeled EVs to electric bikes and tricycles—has surged. However, this prosperity in the market has concealed underlying crises, escalating demands for extended EV ranges, heightened energy density in power batteries, and cost surges.
The current energy density of existing lithium-ion batteries has nearly reached its theoretical limit. This saturation, coupled with rising prices of raw materials such as lithium, cobalt, and nickel, has put considerable pressure on lithium-ion battery costs. Consequently, the pursuit of new technologies and products has become imperative.
Dual Ion Battery (DIB), emerging as a cost-effective, high-voltage, and environmentally friendly energy storage device, has rapidly gained traction. DIB harnesses the synergistic redox energy storage mechanism of anions and cations, delivering high power and energy density. Notably, it presents a dual advantage, excelling in safety and cost-effectiveness over lithium-ion batteries. Recognized by the International Union of Pure and Applied Chemistry (IUPAC), DIB secured a spot among the “Top 10 Emerging Technologies” in 2020.
DIB originated from the exploration of graphite interlayer compounds (GICs) and evolved from dual carbon batteries (DCBs) or dual graphite batteries (DGBs). Unlike the singular ion movement in lithium-ion batteries (involving only Li+ ions), DIB involves both cations and anions from the electrolyte, ushering in its dual ion nomenclature.
Distinctive Material Characteristics of DIB
Early DIB studies were predominantly based on graphite-based carbon materials functioning as both cathode and anode components. Graphite-based cathodes facilitate charging and discharging through anion insertion/de-insertion processes. The choice of cathode materials significantly impacts electrochemical performance parameters such as battery capacity, cycle life, and energy density.
DIB electrolytes serve not just as ion transport mediums but also as sources of active ions during the charge-discharge process. Researchers explore electrolyte concentrations to optimize anion storage behavior, striving for a delicate balance between electrolyte concentration and specific capacity.
Anode materials for DIB encompass carbon-based materials, transition metal oxides/sulfides, organic compounds, and alloyed materials. Alloying anodes offer high specific capacity but face challenges related to volume change during charging-discharging cycles and stability issues, requiring breakthroughs in academia and industry for practical application.
Current Status and Advancements in DIB Research
China has been a hub for substantial research in various facets of DIB. Pioneering studies have been conducted in anode, cathode, and electrolyte research. For instance, Shenzhen Institute of Advanced Technology proposed a novel aluminum-graphite DIB system, significantly enhancing energy density, safety, and cycle stability.
At Sun Yat-sen University, systematic research on carbon-based positive electrode materials and their microstructural influence on electron/ion transport properties has been conducted.
Changchun Institute of Applied Chemistry, Chinese Academy of Sciences (CAS), introduced a cyclobutanesulfone electrolyte system known for its high antioxidant properties. Furthermore, strategies to enhance electrode/electrolyte interface stability have been explored, like using lithium titanate as a surface capping layer on graphite anodes.
Industrial Application of DIB
Japan stands as an early adopter of DIB commercialization, with companies like Power Japan Plus leading the way. In China, the industrialization journey of DIB has commenced, marking strides in pilot R&D and mass production. Institutions like Shenzhen Advanced Technology Research Institute (SATRI) and Shenzhen Zhongke Ruineng have developed pilot production lines and achieved promising milestones, showcasing a dual ion battery core with impressive capacity retention and energy storage system applications.
Future Trajectory for DIB
While DIB shows promise, its energy density, both in terms of volume and weight, still lags behind lithium-ion batteries. Challenges lie in the considerable electrolyte demand, contributing significantly to reduced energy density and escalated costs. Finding an optimal electrolyte ensuring high ionic conductivity and electrochemical stability is pivotal for DIB’s future advancements.