The global transition to renewable energy sources is placing high demands on the development of effective energy storage methods, the most prevalent being batteries. Dual-ion batteries are a new battery technology that takes advantage of the simultaneous intercalation of both cations and anions. Dual-ion batteries can be made from environmentally friendly materials such as organic compounds or conductive polymers that are made up of highly abundant elements. These often have a lower cell voltage than metal-based batteries, allowing water-based electrolytes to be used without decomposing. This master’s thesis presents the synthesis, and electrochemical testing of a nanofibrous polyaniline cathode. It also presents the synthesis and electrochemical testing of two anodes being and graphene-enhanced polyimide, and perylene tetracarboxylic diimide (PTCDI). Aqueous ammonium sulfate of 1 M or 3 M concentration is used as electrolyte. A novel full-cell dual-ion battery is also constructed using polyaniline and PTCDI as electrodes. The addition of graphene to polyimide results in changes in morphology with decreased pore size and increased surface area for supposed improved reaction kinetics with the electrolyte. The electrochemical testing of this anode is however not successful. The polyaniline cathode has an early charge/discharge capacity of 184.5/85.2 mAh/g that decreases to 40.4/45.8 mAh/g after 100 cycles. The PTCDI anode has an early charge/discharge capacity of 80.2/87.3 mAh/g but cannot be evaluated after a few cycles due to electrolyte decomposition. For this reason, the electrolyte dependence on ammonium sulfate concentration is also investigated. An increase in molarity from 1 M to 3 M leads to increased stability of the electrolyte. The polyaniline//PTCDI full-cell has a voltage of 1.2 V and shows an early charge/discharge capacity of 17.6/11.9 mAh/g that decreases to 9.1/7.2 mAh/g after 100 cycles where the efficiency stabilizes at 80%.

In today’s fast adjustment to renewable energy, new battery technologies are needed to meetthe ever-growing demands of energy storage. Cheaper and easier to produce materials areneeded, as well as materials with a lower environmental impact. One new and interestingtechnology is the dual-ion battery, and more specifically the aluminum dual-ion battery. Thisbattery uses cheap and abundant aluminum together with a graphitic cathode to work. However,a lot of research today uses expensive and sophisticated cathode materials to make this type ofbattery work. Therefore, this thesis focuses on creating a cheap and easy to produce graphitecathode material through the phase inversion method for the use in aluminum dual-ionbatteries, that is also freestanding for better energy density. Graphene is also used as anadditive to improve the electrical conductivity of the material, and the material is later tested in afull cell with the typical ionc liquid electrolyte EMImCL/AlCl4.Through phase inversion, a freestanding graphite cathode is produced with 8 wt% PVDF binderand 0.4 wt% graphene. The material has a porous structure and an enhanced electricalconductivity with the graphene added. Through CV cycling and symmetric Al-Al tests the batteryreactions are shown to work. However, when cycling the cell with a constant current there areproblems, probably coming from some sort of soft shorting or side reactions. It is revealed thatapart from the expected reactions, Ni dissolution from the contact tabs also takes place, andmay cause problems. Further tests are needed to validate if this material works. However,because no new active materials have been introduced to the battery chemistry, it is reasonableto believe that the battery will work with some small changes.Tek nisk-naturvetensk apliga fak ulteten, Upps ala universitet. Utgiv nings ort U pps al a/Vis by . H andledare: Anwar Ahniy az , Äm nesgranskar e: D aniel Brandell, Ex aminator: Lena Klintberg

Multifunctional batteries with enhanced safety performance have received considerable attention for their applications at extreme conditions. However, few batteries can endure a mix‐up of battery polarity during charging, a common wrong operation of rechargeable batteries. Herein, a polarity‐switchable battery based on the switchable intercalation feature of graphite is demonstrated. The unique redox‐amphoteric intercalation behavior of graphite allows a reversible switching of graphite between anode and cathode, thus enabling polarity‐switchable symmetric graphite batteries. The large potential gap between anion and cation intercalation delivers a high midpoint device voltage (≈average voltage) of ≈4.5 V. Further, both the graphite anode and cathode are kinetically activated during the polarity switching. Consequently, polarity‐switchable symmetric graphite batteries exhibit a remarkable cycling stability (96% capacity retention after 500 cycles), a high power density of 8.66 kW kg−1, and a high energy density of 227 Wh kg−1 (calculated based on the total weight of active materials in both anode and cathode), which are superior to other symmetric batteries and recently reported dual‐graphite or dual‐carbon batteries. This work will inspire the development of new multifunctional energy‐storage devices based on novel materials and electrolyte systems.

The anode-free battery concept is proposed to pursue the aspiration of energy-dense, rechargeable metal batteries, but this has not been achieved with dual-ion batteries. Herein, the first anode-free Zn–graphite battery enabled by efficient Zn plating–stripping onto a silver-coated Cu substrate is demonstrated. The silver coating guides uniform Zn deposition without dendrite formation or side reaction over a wide range of electrolyte concentrations, enabling the construction of anode-free Zn cells. In addition, the graphite cathode operates efficiently under reversible bis(trifluoromethanesulfonyl)imide anion (TFSI−) intercalation without anodic corrosion. An extra high-potential TFSI− intercalation plateau is recognized at 2.75 V, contributing to the high capacity of graphite cathode. Thanks to efficient Zn plating–stripping and TFSI− intercalation–deintercalation, an anode-free Zn–graphite dual-ion battery that exhibits impressive cycling stability with 82% capacity retention after 1000 cycles is constructed. At the same time, a specific energy of 79 Wh kg−1 based on the mass of cathode and electrolyte is achieved, which is over two times higher than conventional Zn–graphite batteries (<30 Wh kg−1).