NEWS
The Complexity of Lithium-Ion Battery Degradation and Chemical Choices
Release time:
2024-08-28
Lithium-ion battery degradation is complex, influenced by factors such as temperature and charging methods. Different cathode chemistries (e.g., NMC and LFP) affect battery energy density, lifespan, and safety.
Degradation
The whole process is somewhat more complex than boarding a train, however. It involves ion interaction with a multitude of different materials, at different speeds, temperatures, stress levels, and in different processes. Battery degradation issues hinge on factors such as the effect of temperature on electrolyte viscosity, and thus the process speed of this crucial voyage. Also, as the “best seats” are taken, step by step, the host materials slightly expand, adding mechanical expansion stress and potentially leading to internal cracks and fissures. It is obvious that the way of charging, discharging, and operating a battery will dramatically affect the magnitude and rate of degradation processes that lead to the well-known loss of capacity, and also to safety-critical side processes.
In terms of different battery chemistries and the abbreviations mentioned above, the anode reservoir is traditionally made of graphite, albeit with a myriad of secret additives, manufacturing, and processing variations. LTO batteries are an exception which will be considered shortly.
For cathodes, things become more complicated. Cathode materials made of varying amounts of nickel (Ni), manganese (Mn), controversial cobalt (Co) – and sometimes also aluminum (Al) – plus other secret additives, are referred to as NMC or NCA (nickel-cobalt-aluminum) devices. Such cathodes typically have high energy density, meaning they can accommodate a high number of lithium ions per volume but have shorter lifetimes, lower safety margins, and a bigger price tag than rival chemistries as a result.
To satisfy the automotive industry’s hunger for energy density and range, engineers crank up the nickel content – the first NMC batteries had equal parts of the three components, were dubbed NMC 1-1-1, and offered decent energy density and robust safety characteristics. Nowadays, industry adds eight times more Ni than manganese and cobalt, for NMC 811 batteries. These offer much greater range but significantly shorter lifetime and safety characteristics. That’s right, average li-ion NMC lifetimes and safety are decreasing.
By contrast, the second dominant cathode type is lithium iron-phosphate, also known as LiFePO4 or lithium ferro-phosphate. These cathodes feature lower energy density than NMC devices but are more robust and – at least traditionally – more affordable. Increasingly popular, LFP-based batteries are almost entirely manufactured by Chinese producers. LFP systems are handicapped by the fact their voltage varies little over a wide range of battery state-of-charge levels. State of charge, or SOC, is the amount of charge, or energy, in a battery. Less flexible voltage makes balancing and control of systems, as well as determining SOC, difficult and renders LFP applications generally prone to unexpected operational problems and downtime, further aggravating their lower energy density.
LTO devices
As mentioned, there is an exotic battery variant which uses lithium-titanate (lithium titan oxide, or LTO) for the anode, rather than graphite, sometimes paired with an LFP cathode. These devices offer very low energy density (even lower than legacy nickel-metal hydride, NiMH, chemistry) and can cost 50% to 150% as much as NMC cells because they offer between 10 times and 30 times better safety and longevity performance than LFP and NMC systems.
These are broad brush strokes, however, and the terrific variety of li-ion chemistries available offers cell manufacturers the opportunity to push performance in one direction or another. While characteristics can vary as a result, though, a giant leap in energy density for li-ion, without negative effects on aspects such as lifetime, cannot realistically be expected in the near future.
Relevant information
Main office: Room 501, Building 3, No. 81, Dingye Road, Tangjiawan Town, High-tech District, Zhuhai City, Guangdong Province, China 519000
Manufacturing Center：Zhongneng Science Park, No. 168, Tanlong North Road,Tanzhou Town, Zhongshan, China
R&D and Sales Center in Oxford, UK：47,The Lawns, Kennington Road,Radley,Oxfordshire, UK, OX14 2JR
SAF Coolest v1.3.1.2 设置面板 GAGSD-ZGYF-JFAVE-ZQZ
无数据提示
Sorry, the current column is being updated, please look forward to it!