What is the influence factors of lithium battery quick charge ability

Each kind of lithium battery parameters and environmental parameters under different states there is an optimum charging current value, so, look from the cell structure, the factors affecting the optimal charge value all have?

The micro process of charging

Referred to as "rocking chair" type batteries, lithium-ion batteries charged ions movement between is negative, to realize the charge transfer, recharge external circuit power supply or from an external power source. Concrete in the process of charging voltage load in poles of the battery, lithium ion from the anode materials embedded, into the electrolyte, excess electrons through the positive set fluid at the same time, the external circuit to the cathode movement; Lithium ions in the electrolyte from the positive to the negative movement, through the diaphragm to the cathode; Through the SEI film on the surface of the cathode is embedded into the anode graphite layer structure, and combine with electrons.

In the process of the whole operation of the ions and electrons, impact on the charge transfer of cell structure, electrochemical and physical, will have an effect on the fast charging performance.

Quick charge, the battery requirements of each part

For battery, if you want to improve power performance, need the battery every link in the overall effort, mainly including the anode, cathode, electrolyte and the diaphragm and structure design, etc.

The anode

In fact, all kinds of the anode materials can be used to make almost all quick charge battery, need to ensure that the performance of the main including conductance (reduce the internal resistance), diffusion reaction kinetics (), (no need to explain life, security (no need to explain), the appropriate processing performance, specific surface area is too big, reduce side effects, for the security services).

, of course, for each of the specific material to solve the problem may differ, but we usually common anode material can be through a series of optimization to meet these requirements, but also different from different materials:

A, lithium iron phosphate may be more focus on the problems of conductivity and low temperature. Nano carbon coated, moderation (note that is moderate, is definitely not the thinner the better simple logic), formed in the particle surface treatment ion conductor is the most typical strategy.

Conductance, ternary material itself has B is better, but its high reactivity, therefore the ternary material for nano rare work (nano is not all of the antidote of material performance, especially in the field of battery and sometimes there are a lot of reaction), more pay attention to safety and restrain adverse event (with electrolyte), after all, a curse of the ternary material is safe, recently in battery frequent safety accidents has put forward higher requirements.

C, manganese acid lithium is more value for life, also have on market now quite a few quick charge battery lithium manganese acid system.

The cathode

Lithium ion batteries When charging, lithium to negative transfer. And quick charge large current of high potential will lead to negative electrode potential is more negative, the negative pressure quickly accept lithium get bigger, tend to generate lithium dendrite get bigger, so quick charge when the cathode is not only to satisfy the requirement of the lithium diffusion dynamics, to solve more lithium dendrite formation tend to exacerbate brings security problems, so fast charging core and the main technical difficulties for lithium ion embedded in the cathode.

A, currently on the market dominance of the anode materials is still graphite (about 90% of the market share), the root cause without him - cheap, and graphite composite processing is better performance, energy density, relatively few disadvantages. Graphite anode, of course, also have a question, its surface is very sensitive to electrolyte, lithium embedded reaction with strong directivity, therefore carries on the graphite surface treatment, improve its structure stability, promote the lithium ion on the base of the direction of diffusion is the major requires hard work.

B, hard and soft carbon carbon materials in recent years, there are many: the development of hard carbon materials intercalated-li potential is high, the material of microporous so reaction kinetics performance good; And soft carbon material has good compatibility with electrolyte, MCMB material is also very representative, just hard soft carbon material is generally low efficiency, high cost (and imagine graphite as cheap as I'm afraid from the industrial perspective unlikely), so the dosage is far less than graphite, multi-purpose in some more The special battery On.

C, lithium titanate? Simple said once: lithium titanate has the advantage of high power density, safer, shortcomings are obvious, the energy density is low, according to WH calculation cost is very high. So for Titanium acid lithium battery Point of view is a useful technology has an advantage in a particular situation, but for a lot of costs, requiring higher range are not applicable.

D, silicon anode materials is an important development direction, Panasonic's new 18650 battery has already started the commercial process of this kind of material. But how in nano pursuit performance and battery industry for the general micron grade of the material requirements to achieve a balance, is still a more challenging job.

The diaphragm

For power battery, large current work on its safety, life provides a higher request. Diaphragm is not open around coating technology, ceramic coating because of its high safety, can consume diaphragm character such as impurities in the electrolyte is rapidly away, especially for The ternary battery The safety of the promotion effect is particularly significant.

Ceramic membrane is mainly used in system is to put the alumina particles coated in conventional diaphragm surface, is new, it is a solid electrolyte fiber is coated on the diaphragm, so a lower internal resistance of the diaphragm, the mechanics of fiber for the diaphragm support effect is better, and in the process of serving the tendency of congestion on the diaphragm hole is lower.

After coating of the diaphragm, good stability, even if the temperature is higher, it's not easy contraction deformation cause a short-circuit, Tsinghua university institute of materials member of policy, technical support team of Jiangsu south qing tao energy companies have some representative works in this aspect.

The electrolyte

Electrolyte for quick charge has great influence on the performance of lithium ion batteries. In quick charge battery to ensure the stability and security of the shed, the electrolyte should satisfy the following features: A) cannot be separated, and B) higher conductivity, C) for the cathode material is inert, not response or dissolved.

If you want to meet these requirements, the key to use electrolyte additives and function. Such as ternary quick charge battery safety by its influence is very big, must to join all kinds of high temperature resistant, flame retardant, prevent overcharge additives to protect, to a certain extent, improve its security. And lithium titanate battery problem, the high temperature bilge gas, improved function, but also depends on the high temperature electrolyte.

Battery structure design

A optimization strategy is a typical laminated type VS coiling, rather then parallel relationship between laminated type battery electrodes, coiling are so series, and therefore the former internal resistance is much smaller, more suitable for power occasion.

Also can be in very ear number fluctuation kongfu, solve the problem of internal resistance and heat dissipation. Besides using high conductivity electrode materials, using more conductive agent, coating and thinner electrode are also can consider the strategy.

In short, affects the mobile and embedded inside the battery charge electrode cavity rate factor, will affect the lithium battery quick charging ability.

The future of quick charge technology

The electric car is quick charge technology, the direction of history or a flash in the pan mischiefs, actually now opinions vary, no conclusion. As an alternative to solve the range anxiety, it with battery energy density and the overall transport costs on a platform to consider.

Energy density and fast filling performance, at the same battery only, can be said to be the incompatibility of two direction, "she said. The pursuit of the battery energy density, now is the mainstream. When the energy density is high enough, a car loading capacity is large enough, enough to avoid the so-called "range anxiety", will reduce the demand of the battery charging properties; At the same time, the capacity is big, if the battery KWH cost is not low, so whether to KeDingKe Mao buy enough to "anxiety", requires people to make a choice, such a thought, quick charge is the value of existence. Another point of view, is quickly filling facilities costs, which of course is part of a push electric cost of the whole society.

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