This battery test cell is designed for reproducible electrochemical measurements of battery and supercapacitor materials under high compression force. It allows compression of electrode stack at forces up to 2kN and in-situ monitoring of the force. The cell is fully manual operated – no external equipment, like hydraulic press, is needed. Additionally, no extra data logging unit is needed for the in-situ force measurements – the load sensor can be connected to PC directly via USB cable. Free data logging and calibration software is included. The cell can be assembled in static (fixed compression) or dynamic (flexible compression) modes with the use of removable disc springs.

The cell consists of two main elements: (i) the cell base with build-in force sensor and lead screw; and (ii) electrode cartridge where the anode, cathode and reference electrode are located. Redox.me offers various electrode cartridges (different functionality, electrode sizes etc.), which are interchangeable between our battery test cell bases. The (default) electrode cartridge and plungers are designed for planar electrodes with diameter of 18 mm and the total stack thickness of 2.5 mm. The diameter of separator shall be at least 2 mm larger than electrode diameter (max 22 mm). The lock ring secures the separator in the electrode cartridge allowing easy and safe electrodes insertion, while ensuring accurate alignment. The upper and lower electrode plungers are available in various materials: 316L Stainless Steel (default), copper, aluminum, nickel etc. The pin-type reference electrode is installed from the side of the electrode cartridge. Thanks to sharp edged hole at the end of the pin the reference electrode (Li/Na/K etc.) can be easily punched from the metal foil and directly loaded into cell. The magnetic mount facilitates rapid assembly of the cartridge in the cell base. For 2-electrode measurements the reference electrode feedthrough hole can be closed with the reference electrode punch.

The cell elements are constructed with materials that are inert to the sample (Stainless steel and PEEK). It well fits aqueous (FKM or EPDM O-Rings) and organic solvent (FFKM O-Rings) electrolyte requirements. Good electrical contact is ensured by gold plated pins. The construction is air-tight and can be effortlessly assembled in the glove box, reducing possible human error to minimum.

**Application note ** This cell can be used for all common battery measurements, such as galvanostatic cycling, cyclic voltammetry or electrochemical impedance spectroscopy. Both liquid and solid-state electrolytes can be studied. Particularly, it is suitable for solid-state batteries measurements, as they usually require high compression forces. With default electrode size (18 mm) the maximum force of 2 kN equals pressure of 8 MPa – enough for most practical applications. In-situ force monitoring is also extremely useful in study of materials that undergo large volume expansion/contraction upon cycling, such as Si or lithium metal plating (anode-free system). Additionally, properties and performance of supercapacitor materials can be investigated. Various materials can be examined, including typical Li-ion electrodes (graphite, NMC, LTO etc.) and other chemistries – sodium, magnesium, potassium etc. It can also be applied to measure the ionic conductivity of separators and electrolytes.