The capacity and charging rate of lithium batteries are the two primary battery limitations, and improving the high capacity and charging rate of lithium batteries has always been a core issue that the lithium battery industry has been focusing on. Many lithium battery manufacturers use it as a selling point and have launched various new energy lithium batteries to achieve a prosperous production and sales.
Improvement of capacity of lithium batteries
Improving the energy density of lithium batteries (limited to capacity based batteries) is the top priority in battery design. Insufficient capacity, even if the unit price is low, the cycle is good, and the safety is high, the battery produced may not be favored by anyone. The capacity of lithium-ion batteries mainly depends on the quality and ratio of positive and negative electrode active materials, and the positive and negative electrode materials determine the energy density of the battery.
For positive and negative active substances, it is the most direct method to increase the capacity density of lithium batteries. The main directions include:
1. Use materials with greater potential, such as lithium rich cathode materials, high-voltage ternary materials, high-voltage lithium cobalt oxide materials, binary materials, etc; Soft carbon hard carbon, silicon tin based compounds, etc. for the negative electrode.
2. Use positive and negative electrode materials with higher compaction density.
3. Using active substances with better adhesion and conductivity can reduce the content of adhesives and conductive agents in the dressing, thereby increasing the capacity that can be exerted per unit mass of dressing; In addition, reducing the amount of binders and conductive agents can also improve the compaction and processing performance of active materials.
4. Using materials with smaller thickness rebound: After cycling in lithium-ion batteries, there will be a certain rebound in thickness; When designing, it is necessary to reserve the rebound thickness after the cycle; When materials with smaller thickness rebound are used (as far as we can see, these materials are also materials with good cycling performance), the reserved space for thickness rebound can be transferred to the design thickness of the battery cell, thereby increasing the design capacity of the battery cell.
5. Choosing a material system with better performance: a single combination of "good positive electrode", "good negative electrode", and "good electrolyte" cannot guarantee a "good battery". Combining materials with poor compatibility not only reduces the cycling performance of lithium batteries, but may also affect the rate performance and even the balance between positive and negative electrodes; Similarly, when the material compatibility is better, performance such as performance, cycling, and expansion rate may all be improved.
The improvement of charging speed for lithium batteries
The essence of fast charging and discharging of lithium batteries is that lithium ions can quickly deintercalate between positive and negative electrode materials. The properties of battery materials, process design, and charging and discharging systems all have an impact on the high current charging performance. For lithium batteries, the charging method has a significant impact on their performance. A reasonable charging method can extend the lifespan of lithium batteries and improve charging efficiency.
1. A reliable method to improve the charging speed of lithium batteries is to coat and modify the positive electrode material. For example, LFP itself has poor conductivity. Surface coating with carbon or other materials can improve its conductivity, which is beneficial for improving the fast charging performance of the battery.
2. The negative electrode materials used for fast charging of lithium batteries include carbon materials, lithium titanate, and other novel materials. For LTO, it is a zero strain oxygen negative electrode material that does not produce SEI during battery operation. Its binding ability with lithium ions is stronger, which can meet the requirements of fast charging and discharging.
Some people say that charging a lithium battery is like pouring beer. It is fast and can fill beer quickly, but it has a lot of foam. Pouring slowly, the speed is slow, but there is a lot of beer, it's very practical. Fast charging not only saves charging time, but also causes significant damage to the battery itself. So generally speaking, we recommend using slow charging as much as possible when not in a hurry, which is beneficial for extending the battery life, and slow charging of lithium batteries is safer.