The demand for lithium batteries in the communication, tools, automotive and energy sectors is high. Becoming increasingly lighter and with greater energy density, they are replacing heavy lead or nickel-cadmium batteries in these applications.
Lithium iron phosphate batteries cannot meet the requirements for electric mobility and stationary storage as the new generation of lithium batteries. Lithium-ion batteries with special cathode materials are replacing lithium iron phosphate batteries. The new power packs have a long service life with a high energy density and a large number of charge cycles with maximum safety. With carbon compounds containing lithium, these properties can be put to use as anodes and, with a ternary oxide system containing lithium, as cathodes. Market researchers are anticipating above-average growth per year.
Ternary precursors are being used for this. These are predominantly manufactured by means of reactions of nickel, cobalt and manganese solutions through hydroxide or carbonate precipitation. In this process, sodium hydroxide acts as a precipitant and ammonia as the complexing agent. For special applications, the manganese is replaced with aluminium solutions and receives NCA compounds. NCM or NCA precursors are obtained by various solutions being combined in precisely specified quantities, within a specific time frame, at specified temperatures, under stable conditions, and reacting accordingly. The reactions of the chemicals affect the critical properties of the precursors, such as the particle size and their specific surface. Strict proportional control of the reactants directly determines the final ternary material properties and their quality, as well as the purity of the sintered ternary lithium, nickel, cobalt and manganese (NCM) compounds. To obtain an exact quality in the precursors, and above all one that can be reproduced, smart high-end metering pumps are increasingly being used. These ensure the exact metering of the individual heavy metal solutions required for the reaction to achieve the requisite precursor quality at all stages of production.
Task of the metering pumps
Typical production for ternary precursors consists of up to 15 different process stages. Within the individual processes, solenoid-driven metering pumps and motor-driven metering pumps are used to precisely meter fluoride, liquid metal solutions containing amounts of nickel, cobalt and manganese, plus sodium hydroxide (NaOH) and ammonia. In the key process step, the synthesis reaction, ultra-pure water and ammonia are added as the base fluid. Depending on the pH value, three diaphragm metering pumps, for example, synchronously meter the various liquid metal solutions at around 5 to 20 l/min. A NaOH solution is also added and mixed with the metal ion solutions in the reactor. Additional pumps meter the precipitant at around 10 to 40 l/min. The original pH value in the solution is maintained throughout the entire reaction, including all metering and mixing processes. After a reaction time of around 24 h, the pH value is slowly lowered in one-hundredth steps (0.01 pH/H) to a specific pH value. This is done through the absolute and precise addition of NaOH.
Custom metering behaviour
The solenoid-driven metering pumps in the Gamma product range with regulated solenoid drive are ideal for this. Within their capacity ranges of 2.3 to 45 l/h or 8 to 80 l/h at 25 to 2 bar, the precise quantity needed can be set and added to the exact process. Their model-based solenoid control records varying pressure levels, while automatically and precisely adjusting the pump’s metering behaviour to the current conditions. In other words: The pumps always meter the required quantity of the chemical precisely– without any additional sensors. Unlike other metering pumps, this eliminates unnecessary sources of faults in advance.
Intuitive operation and simple programming of all pump parameters needed are key for error-free operation. A minimal number of controls on the gamma pump ensures rapid adjustment of the individual parameters, such as stroke length, frequency, and metering profile.
A click wheel and some push-buttons are all that is needed to quickly access parameters or functions at different menu levels. Specifying the capacity in l/h avoids laborious conversions and allows the setting to be made quickly and easily. The stroke length can be electronically set within the range between 0 and 100 %. Another advantage of controlled pumps is their continuous metering characteristics which ensure the excellent mixing of the individual reactants. With volume-proportional metering of chemicals into a primary flow, elongated metering strokes ensure even distribution. There is therefore no need for static mixers. After completion of the reaction and lowering of the pH, product particles with an average size of a few µm have formed. After repeated washing, these are sedimented, dried at temperatures of up to 150 °C and after one day, can be extracted as a ternary precursor.
Adjusted movement profile
Regardless of the size of the reactors, quantities are also needed that exceed the capacity range of the Gamma product range. In this scenario, Sigma X motor-driven metering pumps are used. Depending on the version, these ensure accurate metering within the range of up to 117 l/h (Sigma1), 353 l/h (Sigma2) or 1040 l/h (Sigma3). They have the same standardised operating concept with click wheel and four additional operating keys as the Gamma pumps. They also provide accurate and complication-free metering of media due to their broad adjustment range thanks to a combination of frequency and stroke length adjustment and adjustment of their movement profile.
Real time communication
Production processes, such as the production of ternary precursors for battery cathode materials, are extremely challenging for operators. It involves maintaining optimal conditions, which are dependent on various metering processes, over a long period of time. The precise quantity of the various solutions must still be continuously metered in real time throughout the entire production period. This requires direct communication using corresponding sensors and the control system. Integrated Profibus and CANopen interfaces enable simple connection to process control systems. As smart products, the Gamma/ X and XL diaphragm metering pumps, and the Sigma X can be connected to the Dulconnex web-based fluid management platform. This allows the operator to monitor, analyse and optimise the individual metering processes with ease. Each process can be monitored in real time. Downtimes and the consumption of raw materials used are thus minimised. The result: The result: high quality ternary precursors which ensure that batteries have high energy density and a longer service life.
Prominent GmbH, Heidelberg