The Development of Lithium Batteries in Drones

Batteries are the power source of drones. And there are many types of batteries, including lead-acid batteries, nickel-metal hydride batteries, nickel-chromium batteries, lithium batteries, hydrogen batteries, etc. The current mainstream drone battery is lithium battery, which has better performance than other varieties. Lithium batteries are divided into power batteries and ordinary batteries. Although they are the same as lithium batteries, there are still many differences.

Different in characteristics:

Compare to small batteries that provide energy for portable electronic devices, lithium power batteries refer to batteries that provide power for drones. Ordinary batteries use lithium metal as anode material and use a non-aqueous solution as electrolyte. Lithium-ion batteries are different from lithium-ion polymer batteries.

The energy density of batteries is different:

in the case of new batteries, the discharge meter tests the capacity of the power lithium battery and the ordinary battery. The capacity of the general lithium power battery is about 1000-1500mAh; while the capacity of ordinary batteries is above 2000mAh, some can reach 3400mAh.

The discharge power is different:

a 4200mAh power battery can discharge all the power in just a few minutes. However, ordinary batteries cannot do it at all, so the discharge capacity of ordinary batteries cannot be compared with that of power batteries. The biggest difference between a lithium power battery and an ordinary battery is its large discharge power and high specific energy. Since the main purpose of power batteries is to supply energy to drones, they have a higher discharge power than ordinary batteries.

The discharge power is different:

a 4200mAh power battery can discharge all the power in just a few minutes. However, ordinary batteries cannot do it at all, so the discharge capacity of ordinary batteries cannot be compared with that of power batteries. The biggest difference between a lithium power battery and an ordinary battery is its large discharge power and high specific energy. Since the main purpose of power batteries is to supply energy to drones, they have a higher discharge power than ordinary batteries.

The Development of Lithium Drone Battery

Generalization
The generalized polymer lithium battery has the main characteristics of the above-mentioned polymer lithium battery, etc., and can be applied to drones of different weights. The battery commonly used in drones is a T-type polymer lithium battery, and one end of the power cord is connected to the male and female heads (generally XT60) for energy output.The signal line at the other end is usually detected by equipment such as a voltage detector.

Generalized polymer lithium batteries are a low-cost power solution for drones. However, they will bring many problems. For example, first of all, the battery power cannot be monitored in real time, and there will be a risk of falling off the plane. Secondly, there is no perfect charging management and discharge management. After the charging and discharging are completed, a voltage detector needs to be used to detect the battery. Third, the problem of over-discharge cannot be solved.Fourth, due to the frequent use of plug connections, the problem of plug aging cannot be solved. Fourth, the battery is flammable and explosive, and there are great safety risks.Fifth, recycling is inconvenient, and lithium batteries cause great environmental pollution.Fifth, the battery itself has a low energy density, which cannot meet the urgent needs of drones during long-term flights.Sixth, disassembly and assembly are inconvenient, and the frequency of replacement of batteries by drones is high, which affects the user experience.

Intelligence

Intelligent polymer lithium batteries mainly directly hit the pain points of the use of the above-mentioned general polymer lithium batteries, optimized the design, combined with the UAV flight control system and the optimized battery management system, to achieve intelligent management and control of the battery.In terms of battery structure, first of all, ABS+PC fireproof materials are selected to improve the protection level of the battery.Secondly, the integrated design of the fast charging port, while adding a power control switch, reflects the convenience of operation, and again, the buckle design of the battery head is easy to quickly disassemble.Finally, taking into account the appearance and shape of the battery, realize the productization of smart batteries.

On the hardware, the battery is equipped with a BMS Battery Management System (BMS for short).BMS is an important link between drone power batteries and electric drones.BMS is used to monitor and indicate the battery, capacitance status (voltage, temperature, current, remaining energy), send an alarm signal (sound and light) to the user under abnormal circumstances, and cut off the power transmission link according to the formulated control strategy in severe cases to protect the battery and extend the battery life.

BMS consists of three parts: a terminal module, a central processing module and a display module.The terminal module is responsible for measuring the battery voltage and temperature, equalizing the battery energy, current sampling and SOC calculation, generating various alarm data, and controlling the charge and discharge circuit; the display module is responsible for displaying the battery data, giving sound and light alarms, recording data, etc.When the total number of system batteries is small, the central processing module and the terminal module can be combined to form an integrated BMS system to save costs.

Solidification

The solidification development of lithium batteries is mainly to solve the safety risks, green environmental protection, low energy density and other problems of general-purpose lithium batteries. The energy density of existing liquid lithium-ion batteries is generally only 130-160Wh/kg, and the ceiling is about 300Wh/kg.And there are disadvantages of long charging time and low safety.The energy density of solid-state lithium-ion batteries will be much higher. The energy density of all-solid-state lithium-ion batteries can reach up to 900Wh/kg, and the structure is safer, so it was once considered an ideal drone power battery.

In terms of working principle, there is no difference between solid-state lithium batteries and traditional lithium batteries.The two ends of the battery are the positive and negative poles of the battery, and the liquid electrolyte is in the middle.Lithium ions move back and forth at both ends through the electrolyte to complete the charging and discharging process of the battery.The main difference is that solid-state lithium batteries, except that their electrolytes are solid.The density and structure of solid-state lithium batteries can allow more charged ions to gather at one end and conduct greater current, thereby increasing the battery capacity.

Solid-state lithium batteries have many advantages and broad prospects for development. Among them, the two most obvious advantages are higher energy density and safer operation. After using an all-solid electrolyte, lithium batteries can not use lithium-embedded graphite negative electrodes, but it can directly use lithium metal as the negative electrode, which can greatly reduce the amount of negative electrode material, so that the energy density of the entire battery has been significantly improved.Now in many laboratories, all-solid-state batteries with an energy density of 300-400Wh/kg can be trial-produced in small batches.The solid-state battery will not work at high currents and will not pierce the diaphragm due to lithium dendrites, causing a short circuit, will not have side reactions at high temperatures, and will not burn due to gas production.

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