Progress in the field of next-generation high-energy lithium battery electrolytes and binders

The market and consumers are highly concerned about the cruising range of electric vehicles and portable electronic products, driving the continuous improvement of the energy density of lithium-ion batteries. The most commonly used strategy to increase the energy density of lithium-ion batteries is to develop new high-voltage and high-capacity cathode materials (such as lithium nickel manganate, high-voltage lithium cobalt oxide, high-voltage ternary materials, etc.) or high-capacity anode materials (such as silicon carbon materials). ). However, these new electrode materials have poor compatibility with traditional electrolytes and binders, and it is difficult to form a stable interface, which has become one of the bottlenecks restricting the commercialization of next-generation high-energy lithium-ion batteries. Relying on the Qingdao Institute of Energy Storage Industry Technology, built by the Qingdao Institute of Bioenergy and Processes, Chinese Academy of Sciences, the research on the next generation of high-energy lithium-ion batteries and their supporting electrolytes and binders is one of the main research areas. As we all know, the electrolyte is the 'blood' of lithium-ion batteries. The development of high-performance electrolytes and the research on the formation mechanism of the electrode/electrolyte interface will greatly improve the performance of the next generation of high-energy lithium-ion batteries. Inspired by the traditional Chinese medicine prescription and western medicine 'drug synergy' idea, Qingdao Energy Storage Institute has further developed the 'electrolyte functional additive synergy' strategy to achieve the goal of greatly improving the performance of next-generation high-energy lithium-ion batteries, such as high-voltage cobalt acid Lithium/graphite full battery system (Energy Technology, 2017, 5, 1979-1989) and 5V high voltage lithium nickel manganese oxide/graphite full battery system (Advanced Energy Materials, 2018, 8, 1701398). Although these research works have made a guiding explanation for the synergistic mechanism of additives, they are limited to the characterization of ex-situ technical means and may not reflect the true state of the electrode/electrolyte interface reaction. In recent years, the development of in-situ characterization technology has injected new vitality into the development of high-performance electrolytes and the study of electrode/electrolyte interface formation mechanisms. Gas is an important product of the electrode/electrolyte interface reaction. Determining the gas product combined with the characterization and analysis of the interface solid product will achieve an effective analysis of the electrode/electrolyte interface reaction. In-situ differential electrochemical mass spectrometry (in-situDEMS) can Real-time monitoring of the gas production behavior of quantitative batteries at different potentials has attracted much attention (Figure 1a). Qingdao Energy Storage Institute used in-situDEMS (Hiden, HPR-20 and HPR-40) and theoretical calculations to study the influence of electrolyte additives on the electrolyte/electrode interface reaction in high-capacity silicon carbon anodes (Figure 1b- d), and successfully constructed a 5V high-voltage lithium nickel manganese oxide/silicon carbon full battery system, which has important guiding significance for the development of electrolyte functional additives and the in-depth study of the interface. The related work is TracingtheImpactofHybridFunctionalAdditivesonaHigh-Voltage(5V-class)SiOx -C/LiNi0.5Mn1.5O4Li-ionBatterySystem was published in Chemistry of Materials (2018, 30, 8291-8302). In addition, Qingdao Energy Storage Institute has independently developed a new type of lithium perfluoro-tert-butoxy trifluoroborate (LiTFPFB) with a large anion structure as the main electrolyte (ChemicalScience). The amount of binder in lithium-ion battery electrodes is very small, but it plays a key role, but it is easily overlooked in research. Polyvinylidene fluoride (PVDF) is the most commonly used binder for cathode materials. In recent years, studies have found that PVDF is unstable under high-voltage working conditions, which is an important reason for the performance degradation of next-generation high-energy lithium batteries. Qingdao Energy Storage Institute uses renewable lignin containing a large number of phenol groups as a new functional binder for the 5V high-voltage lithium nickel manganate cathode material, and the cycle performance of the new cathode material has been greatly improved. After full experimental demonstration, it is found that the phenol group in the lignin binder can eliminate the free radicals in the electrolyte and terminate the chain reaction of the free radicals, thereby inhibiting the oxidative decomposition of the electrolyte, and constructing a highly stable electrolyte/electrode Interface, this work has a milestone guiding significance for the development of high-voltage cathode material binders. Related work was published online in Energyu0026Environmental Science (2018, DOI:10.1039/c8ee02555j) with the topic Abiomassbasedfreeradicalscavengerbinderendowingacompatiblecathodeinterfacefor5Vlithium-ionbatteries. Qingdao Energy Storage Institute's achievements in the research field of next-generation high-energy lithium-ion batteries and their supporting electrolytes and binders have been highly recognized by international counterparts. They were invited to write a review on 5V high-voltage lithium nickel manganese batteries (Chemistry of Materials, 2016). ,28,3578-3606); A review of electrolyte flame retardants (Energy Storage Science and Technology, 2018,6(7),1040-1059); A review of high-voltage lithium cobalt oxide batteries (ChemicalSocietyReviews,2018,47, 6505-6602); a review of polymer electrolytes for ternary cathode materials (ElectrochemicalEnergyReviews, 2018, received); a series of articles on a review of high-performance binders (EnergyStorage Materials, 2018).