Has the energy density of lithium-ion batteries really improved? Is it still the lithium iron phosphate or lithium iron manganese phosphate route? Will ternary materials change? To address these questions, the media interviewed Dr. Fan Weifeng of the Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, and Technical Director of Chengdu Xingneng New Materials Co., Ltd.
Lithium iron phosphate is not alone.
Dr. Fan Weifeng believes that lithium iron phosphate is a complex phosphate formed by lithium and another metal ion, similar to chemical fertilizers sold on the market (ammonium dihydrogen phosphate, iron ammonium phosphate, etc.), but with different solubility. That's why some people say that lithium iron phosphate fertilizer can be used as phosphate fertilizer. In fact, lithium iron phosphate has extremely poor solubility and cannot release effective phosphorus components into the soil.
Fan Weifeng explained that because phosphate ions have a large number of oxygen ions and coordination space, they can often form interconnected spatial aggregate structures with transition metal ions. Therefore, these ions belong to another major category—polyanionic compounds (polyanionic cathode materials).
Polyanionic cathodes are a large family.
Dr. Fan Weifeng explained that M represents any of the metal elements replaced by iron, manganese, cobalt, nickel, copper, chromium, etc. As long as M is a variable valence metal and the above-mentioned compound has a stable structure and has a lithium-ion diffusion channel, it can be used as a lithium battery cathode material. However, the capacity, voltage, rate performance, and lifespan will differ.
Lithium manganese iron phosphate or lithium iron manganese phosphate?
Dr. Fan Weifeng believes that the name doesn't matter; the key is the final iron-manganese ratio. Currently, there is no clear consensus similar to that of ternary materials (532, 111, 811, etc.) on what iron-manganese ratio is optimal. This is because a stable and high-performance lithium iron manganese phosphate has not yet been developed. Perhaps the lithium iron manganese phosphate that will actually be used in the future will be a composite phosphate of more metals.
Is the technology genuine?
The theoretical specific capacity of lithium iron phosphate is 170 mAh/g, the discharge platform is 3.4 V, and the material energy density is 578 Wh/kg; the theoretical specific capacity of lithium manganese phosphate is 171 mAh/g, the discharge platform is 4.1 V, and the material energy density is 701 Wh/kg, which is 21% higher than the former.
Dr. Fan Weifeng explained to my country Battery Network that the energy density of existing lithium iron phosphate batteries ranges from 90Wh/kg to 130Wh/kg. Even with pure lithium manganese phosphate contributing 21% to the energy density improvement, the highest energy density can only reach around 150Wh/kg, and batteries using lithium manganese iron phosphate can only achieve energy densities below 150Wh/kg. If we compare the best-case scenario (150Wh/kg) with the worst-case scenario (90Wh/kg) of existing lithium iron phosphate batteries, we can infer a maximum improvement of 67%, but this is clearly just an assumption.
Comparative analysis of BYD lithium iron manganese phosphate
Dr. Fan Weifeng stated that BYD's genuine pursuit of change in technology and strategy >
Regarding the authenticity of technological innovation, BYD may gradually put forward some newer concepts and viewpoints, attempting to continue to lead the development direction of the industry; however, regardless of whether it denies its established lithium iron phosphate technology route, BYD has only two directions: (1) Adhering to the old lithium iron phosphate model, which gradually ages in the new energy industry and is abandoned, just like the process that BYD is helplessly completing. (2) Actively preparing new routes, announcing its true ideas at the right time, and achieving rapid technological transformation based on its own strong R&D team, thus achieving a second industrial victory.
Dr. Fan Weifeng's comments to Wang Chuanfu during an interview with my country Battery Network—"We chose lithium iron manganese phosphate, an element that is abundant on Earth and will never be depleted. Therefore, from an economic perspective, we chose this route. Of course, as battery technology continues to develop, we may also choose other technological routes"—clearly have an underlying message. In other words, BYD cannot stick to one path forever!
Industry discussions with differing opinions
Voice 1: While lithium iron phosphate (LFP) technology certainly represents progress, there's a slight element of hype involved; it's not as good as Wang Chuanfu claims. 90Wh/kg is relatively poor for LFP batteries, while 150Wh/kg represents the best performance achievable by the new generation of LFP products. Comparing the worst of the old to the best of the new makes the data more eye-catching.
Voice 2: We don't know when lithium iron phosphate will be mass-produced, because we are not with BYD. However, leading international manufacturers, such as PHOSTECH, already have production capacity for lithium iron phosphate materials, and Tianjin Sterland has long been producing in ton-scale quantities.
Voice 3: Lithium manganese iron phosphate (MFP) material has two voltage plateaus, corresponding to the redox reactions of manganese and iron. If it were to replace lithium iron phosphate batteries, the battery system would require slight modifications, but these are estimated to be minor. The preparation process for this material is not significantly different from that of lithium iron phosphate, and the battery manufacturing technology is likely similar, suggesting a promising future for its adoption.
Voice 4: Lithium manganese iron phosphate is an upgraded version of lithium iron phosphate, and it has certain advantages over lithium iron phosphate. I work with lithium manganese iron phosphate; it's promising, but it's not easy to produce.
