A Paper Relating to the Thermal Management of Batteries.

[NNadir]

To make a comment I'll briefly report on this paper: Balancing Charging Efficiency and Thermal Safety: A Comparative Analysis of Multistage Constant Current Charging Protocols Meiyuan Jiao, Jianglong Du, Haihua Xu, Jia-hui Li, Michelle Fu, Wenqi Yang, Weiling Luan, Cheng Lian, and Honglai Liu Industrial & Engineering Chemistry Research 2024 63 (22), 10054-10066.

People love to believe that storing energy is the same as having energy. We have two versions of this very, very, very, very ignorant belief, which is regrettably wildly popular and based on the obviously absurd idea that the world is awash in so called "renewable energy," - it isn't - batteries and hydrogen. In response to this nonsense, I regularly point to the second law of thermodynamics, which cannot be repealed by any legislature and doesn't go away because wishful thinking makes one happy. It's a law of physics, laws so based on reality that none other than Albert Einstein declared that the laws of thermodynamics will never be overturned. A consequence of the second law is that storing energy wastes energy.

The wasted energy is expressed as heat. Now that we have understood, because of work conducted in the late 19th century and early 20th century by some of the finest minds the world has ever known, what heat is, we can easily, with a modicum of education, understand that heat is the result of entropy, energy rejected to the environment.

One sees around here and elsewhere, we see the fossil fuel salespeople rebranding fossil fuels as "hydrogen," promoting stories about how the competition for storing energy, batteries are dangerous because of battery fires. This overlooks the reality that energy itself is dangerous. A gasoline fire is not less odious than a battery fire, and neither is a hydrogen explosion less odious than a gasoline fire. Most fossil fuel sales people around here and elsewhere are antinukes who like to prattle endlessly about the big bogeyman at Fukushima. The explosion of the Fukushima reactors was not a nuclear explosion; it was a hydrogen explosion where the hydrogen was generated by heating zirconium cladding to high temperatures in the presence of steam, resulting in the following chemical reaction:

2H₂O + Zr -> 2H₂ + ZrO₂.

(Nuclear fuels designed to prevent this reaction have been developed and are undergoing testing.)

Consumer hydrogen is a very, very, very bad idea, a wasteful idea, not only because of danger, but because it wastes energy and drives the increased use of dangerous fossil fuels.

A Giant Climate Lie: When they're selling hydrogen, what they're really selling is fossil fuels.

Some of the text from the paper:

The rapid development of electric vehicles with high energy efficiency and low exhaust emission demands future advanced lithium-ion batteries (LIBs) with high power and energy density and fast-charging capability. (1?4) However, thermal safety limits the development of LIBs. (5?8) Numerous researchers have suggested various alternatives, such as changing the battery electrode structure, altering the battery pack’s construction, and improving the heat dissipation mechanism, to increase the thermal safety of LIBs. (9?13) All of these options, however, raise the price of producing LIBs during the manufacturing process. LIBs’ thermal safety can be enhanced with low production costs with properly planned charging processes. (7,9?11) Traditional charging protocols advocate applying small currents to the LIBs charging process because large charging currents will increase the battery’s heat generation rate. Once the battery temperature exceeds the critical value, the heat control of the battery will fail and the battery may catch fire and explode. (14?16) Therefore, designing and developing new fast-charging protocols that can reduce the heat generation of batteries and improve the performance of batteries are crucial to the development of high energy density and fast-charging LIBs.

As a new fast charging protocol, multistage constant current (MSCC) charging is often employed to reduce the charge time and extend the cycle life of LIBs. (17,18) MSCC charging protocols can reduce the heat generation rate of batteries and enhance the charging performance. (19) Multiple currents that are continuously switched during the charging process consist of the MSCC charging protocol. In addition, the pulse current charging strategy can also improve the charging performance of a lithium-ion battery. Among them, the pulse constant current charging mode (PCCC), by a positive pulsed current (PPC) followed by a constant current (CC), alternately, can make the battery capacity utilization rate of 80%–95%. (20,21) Inspired by this, this research examines the effect of current switching frequency (CSF) on the thermal behavior of batteries during MSCC charging.

The thermal performance of LIBs has been the subject of numerous experimental studies. (22?24) Currently, the experimental methods adopted to investigate the thermal performance of LIBs are primarily macroscopic in nature. Compared to experimental methods, simulation techniques can efficiently lower the cost by visualizing the processes of ion transport, heat generation, and heat transfer within the LIBs. (25?29) Studies on how fast charging processes affect lithium-ion battery thermal behavior are primarily based on empirical techniques and empirical models, e.g., equivalent circuit models. (26,30) These research techniques fall short of accurately capturing the dynamic behavior of LIBs during the charging process. The pseudo-two-dimensional (P2D) electrochemical model proposed by Newman et al. (31?33) was employed to investigate the dynamic characteristics of LIBs. (31?34) Bae et al. used the electrochemical model to examine the impact of three independent parameters, including the diffusion coefficient of lithium ions, the lithiation rate constant on the surface of the active material, and the particle radius of the active material, on the performance of the batteries. (35) An et al. discovered that the average heat generation rate is relatively unaffected by temperature after simulating the thermal behavior and dynamic evolution of electrochemical processes in a battery using an electrochemical model. (36) However, few studies have utilized the electrochemical model to illustrate the influence of the fast-charging protocols on the electrochemical-thermal behavior of batteries...

...Combined the designed MSCC charging protocols with different CSFs, we explored the influence of CSF on the battery temperature. The theoretical model is verified by using a commercial LiCoO2/graphite battery with a 3 : 7 volume ratio of ethylene carbonate (EC): methyl ethyl carbonate (EMC) electrolyte. Additionally, under various charging protocols, the reversible, joule, and polarization heats in the battery’s positive, separator, and negative electrodes are studied. By utilizing multistage constant current charging strategy, the impact of various ambient temperatures on the thermal behavior of the battery is also elucidated...

It goes on about charging protocols to minimize the energy wasted or at least ways to make the wasted energy less dangerous, but as in the case of rebranding fossil fuels as hydrogen, fossil fuels being dangerous mostly because of fossil fuel chemical waste responsible for extreme global heating, primarily CO₂ and observably deadly air pollution, but also because of fire and explosion risk, stored energy like energy itself is dangerous. What humanity has accepted, in a de facto sense, is the tradeoff where the danger of using energy is less odious than the risk of not having energy at all.

Have a nice Sunday afternoon.