A few years in the energy sector is usually considered a blink of an eye. This makes the rapid transformation of the battery storage market in recent years even more remarkable. The battery storage landscape in the electricity sector is moving away from NiCd; it has shifted towards lithium-ion batteries, as well as advanced lead-acid. For many applications, lithium-ion has proved preferable to other chemistries with respect to energy and power density, cycle and calendar life, and cost. The lithium-ion deep discharge cycle life, energy and power density, and other attributes have proved preferable over other battery types. In conjunction with rapid cost decreases, this has led to increased deployment of lithium-ion.

What is a LiFePO4 battery?

LiFePO4 Battery, with the full name of lithium iron or lithium ferro-phosphate battery. It is a high-power lithium-ion rechargeable battery for energy storage, EVs, electric tools, yacht, and solar systems that uses lithium iron phosphate as the positive material. LFP Battery Cell has excellent safety and cycle life performance advantages and is the most critical technical index of a power battery.

The lithium iron phosphate battery is a type of rechargeable battery based on the original lithium-ion chemistry, created by the use of Iron (Fe) as a cathode material. LiFePO4 cells have a higher discharge current, do not explode under extreme conditions, and weigh less but have lower voltage and energy density than normal Li-ion cells.

Iron (Fe) is an intrinsically safer cathode material than Cobalt (Co). The Fe-P-O bond is stronger than the Co-O bond so that when abused (short-circuited, overheated, etc.) the oxygen atoms are much harder to remove. This stabilization of the redox energies also helps fast ion migration. Only under extreme heating, generally over 8000C, does breakdown occur which prevents the thermal runaway that typical Li-Ion cells are prone to.

LiFePO4 is highly resilient during oxygen loss which typically results in an exothermic reaction in other lithium cells. No PCM is needed but recommended to maintain cycle life and capacity.

What is the history behind lithium iron phosphate batteries?

LiFePO4 is a natural mineral of the olivine family (triphylite). Arumugam Manthiram and John B. Goodenough first identified the polyanion class of cathode materials for lithium-ion= batteries. LiFePO4 was then identified as a cathode material belonging to the polyanion class for use in batteries in 1996 by Padhi et al. Reversible extraction of lithium from LiFePO4 and insertion of lithium into FePO4 was demonstrated. Because of its low cost, non-toxicity, natural abundance of iron, its excellent thermal stability, safety characteristics, electrochemical performance, and specific capacity (170 mA·h/g, or 610 C/g), it has gained considerable market acceptance.

How the LiFePO4 battery is made up?

The lithium iron phosphate battery (LiFePO4 battery) or LFP battery (lithium fluorophosphate) is a type of lithium-ion battery using lithium iron phosphate (LiFePO4) as the cathode material and a graphitic carbon electrode with a metallic backing as the anode. The energy density of an LFP battery is lower than that of other common lithium-ion battery types such as Nickel Manganese Cobalt (NMC) and Nickel Cobalt Aluminium (NCA) batteries.

What are the basic specifications of the LiFePO4 battery?

Because of being a lithium-ion battery, the minimum and maximum discharge voltage of the LiFePO4 battery respectively lower than any other available commercial battery in the market. However, the cell voltage of the LiFePO4 battery is, 2.5 (minimum discharge voltage), the working voltage is between 3 to 3.2 volts, and the maximum charge voltage is 3.65 volts. The volumetric energy density of the LiFePO4 battery is 220 Wh/L (790 kJ/L). Gravimetric energy density is greater than 320 J/g and up to 580 J/g. However, the cycle life of LiFePO4 battery is 2700 to more than 10000 CPS depending upon conditions.

The cycle life of LiFePO4 ferro phosphate Battery at 1C charging is around 2000 times, it also has the performance that puncture does not explode, and it is not easy to burn when overcharging. The materials of lithium iron phosphate cathode make large-capacity lithium batteries easier to use in series. LiFePO4 has a working voltage of 2.8V ~3.65V, a nominal voltage of 3.2V, and a wide operating temperature range (-20℃~ +75℃).

The good and bad of LiFePO4 batteries

Advantages of LiFePO4 Batteries

Some main advantages of LiFePO4 batteries are as follows:

Less Degradation & Long Life

LiFePO4 has a long life cycle as compared to other batteries and has 1,000-10,000 cycles. Lithium iron phosphate has an excellent discharge rate and has less degradation at high temperatures. Because of their extended life features, you can use these batteries for various applications. A standard qualified LiFePO4 battery remains 80% DOD till 2000 cycles of discharging and charging.

No Harm to the Environment

Lithium-iron phosphate batteries are eco-friendly and do not contain harmful metals. They are non-contaminating and non-toxic and are less costly than other lithium-ion and Lithium polymer batteries.

Compact Size & Lightweight

Lithium iron phosphate batteries have a compact size and high power density. They are lightweight and have no memory effect.  Lithium iron phosphate batteries don’t require priming, and less maintenance is required for their care. They are gaining fame due to their small size, lightweight, stability at high temperatures and low cost.

High Safety & Efficiency

No downtime and fast charging make lithium iron phosphate more efficient and safer to use. These batteries can deliver a high discharge pulse rate in a short time and have constant discharge voltage. The chemical and thermal stability makes lithium iron phosphate batteries more reliable and safer.

Withstand Extreme Weather conditions & Temperature

These batteries can withstand extreme weather conditions and temperatures, and the battery remains cool at high temperatures. They don’t have thermal runaways and don’t explode when they overheat or overcharge.

Good Storage & Suitable for Various Applications

Lithium iron phosphate batteries use for various applications such as electronic machines, military, medical applications, and electric motors. For a cheap battery alternative, these batteries can be a good choice. Safe iron phosphate chemistry and no recycling procedure make these batteries cheaper than LiPo and Li-ion batteries.

The LFP cells exhibit substantially longer cycle life spans under the examined conditions: 2500 to 9000 EFC vs 250 to 1500 EFC for NCA cells and 200 to 2500 EFC for NMC cells. Most of the LFP cells had not reached 80% capacity by the conclusion of this study for the NCA and NMC cells. For LFP cells that have not yet reached 80% capacity, the lifetime was extrapolated based on the present (linear) degradation rate. Among the three chemistries, there is no universal dependence on temperature, DOD, or discharge rate. A more systematic analysis of variable dependence is presented below. The LFP cells show higher RTEs than NCA and NMC cells at all conditions, though the differences are minimized at lower discharge rates.

Disadvantages of LiFePO4 Batteries

Compared to LFP cells, the NCA and NMC cells experienced a more dramatic transition in a capacity fade from partial to complete DOD and this result is consistent with previous studies. This transition could be attributed to the metal oxide cathodes’ higher operating voltages (100% SOC corresponds to 4.2 V for NCA and NMC vs 3.6 V for LFP), which could promote electrolyte oxidation.44,45 A separate study of LFP cathode half cells charged to different voltages (with an electrolyte of 1 M LiPF6 in EC: DEC 1:1 weight ratio) showed optimal performance at 3.9 V vs Li/Li+, with no difference in long-term cycling degradation between maximum voltages of 3.6 and 4.2 V.46 These results suggest that the electrochemical cycling behavior of LFP cathodes charged with different upper voltage limits merits further exploration, as the results could vary with the cell manufacturing and electrolyte composition.

On the other hand, lithium iron phosphate batteries also have some disadvantages over other lithium chemistries. Two of them are the most serious. The BIGGEST disadvantage of lithium iron phosphate batteries is low capacity. For instance, while a standard 3.7V lithium-ion 18650 battery can have a capacity as high as 3500mAH, a LiFePO4 18650 battery has a capacity of only around 1500mAH at most. Because it takes more and/or larger batteries to store the same amount of energy with LiFePO4 vs other chemistries, LiFePO4 is not as well suited to mobile applications. LiFePO4 is generally limited to stationary applications where longevity, voltage stability, and lead-acid compatible voltage are needed.

Another disadvantage is slightly lower voltage. This is not necessarily a disadvantage per se. But it can be for some applications. For instance, an LED that might work fine when powered by a single 3.7V cell may glow dimly with a 3.2V LiFePO4 cell. And the efficiency of voltage-boosting circuitry might be decreased if voltage must be increased. This lower voltage is not necessarily always a disadvantage, as it makes four LiFePO4 cells very close in voltage to a 12V lead-acid cell. But it can be for certain applications. However, lithium iron phosphate batteries also have some other disadvantages. They’re as follows:

1. Users will have to face balancing issues with aging, and they are a high self-discharging rate compared to other batteries.
2. Lithium iron phosphate abbreviated as LFP batteries have a low energy density also, and this is why more protection is required for maintaining battery life and functioning.
3. Lithium iron phosphate batteries don’t perform well at low temperatures and need more protection and care for use in such apparatus.
4. Transportation and aging effects are also common in lithium iron phosphate batteries like some other kinds of batteries.
5. One of the other drawbacks of LPF is deep discharge and low density. These flaws make these batteries unfit for small devices such as smartphones. Therefore mainly, these LFP batteries are used in LEV (low-emission vehicles) and electric bikes.

To sum up the aforementioned advantages as well as the disadvantages, of users willing to purchase an LFP battery, it is essential to know its pros and cons and whether it fulfills their requirements. It helps the user in saving money and time. Buying an LFP battery from an authentic supplier will make the user avoid any quality problems in the future.

Why aren’t lithium-iron phosphate batteries used in vehicles?

Lithium-iron phosphate batteries actually have LOTS going for them. They can produce LOTS of current for high-power applications. They last a long time. Voltage is virtually constant during the entire discharge cycle. They don’t use exotic metals like cobalt. And they don’t tend to catch fire. But they have a rather big disadvantage: capacity is low. This means that you need a larger and heavier battery pack to get a given range. Or that it is impossible to fit a sufficiently large pack in a vehicle to get the range people desire. Other lithium chemistries can provide a higher energy density and, therefore, longer range. This is why lithium iron phosphate has generally been ignored by manufacturers of EVs.

Do LiFePO4 batteries provide better aging and cycle-life characteristics?

LFP chemistry offers a considerably longer cycle life than other lithium-ion chemistries. Under most conditions, it supports more than 3,000 cycles, and under optimal conditions, it supports more than 10,000 cycles. NMC batteries support about 1,000 to 2,300 cycles, depending on conditions.

LFP cells experience a slower rate of capacity loss (aka greater calendar life) than lithium-ion battery chemistries such as cobalt (LiCoO2) or manganese spinel (LiMn2O4) and lithium-ion polymer batteries (LiPo battery) or lithium-ion batteries.

How viable are lead-acid batteries as an alternative to LiFePO4 batteries?

Because of the nominal 3.2 V output, four cells can be placed in series for a nominal voltage of 12.8 V. This comes close to the nominal voltage of six-cell lead-acid batteries. Along with the good safety characteristics of LFP batteries, this makes LFP a good potential replacement for lead-acid batteries in applications such as automotive and solar applications, provided the charging systems are adapted not to damage the LFP cells through excessive charging voltages (beyond 3.6 volts DC per cell while under charge), temperature-based voltage compensation, equalization attempts or continuous trickle charging. The LFP cells must be at least balanced initially before the pack is assembled and a protection system also needs to be implemented to ensure no cell can be discharged below a voltage of 2.5 V or severe damage will occur in most instances, due to irreversible de-intercalation of LiFePO4 into FePO4.

What is the safety of using a LiFePO4 battery?

One important advantage over other lithium-ion chemistries is thermal and chemical stability, which improves battery safety. LiFePO4 is an intrinsically safer cathode material than LiCoO₂ and manganese dioxide spinels through the omission of the cobalt, with its negative temperature coefficient of resistance that can encourage thermal runaway. The P–O bond in the (PO₄)³⁻ Ion is stronger than the Co–O bond in the (CoO2)⁻ Ion, so when abused (short-circuited, overheated, etc.), the oxygen atoms are released more slowly. This stabilization of the redox energies also promotes faster ion migration.

As lithium migrates out of the cathode in a LiCoO2 cell, the CoO2 undergoes non-linear expansion that affects the structural integrity of the cell. The fully lithiated and unlithiated states of LiFePO4 are structurally similar which means that LiFePO4 cells are more structurally stable than LiCoO2 cells.

No lithium remains in the cathode of a fully charged LFP cell. (In a LiCoO2 cell, approximately 50% remains.) LiFePO4 is highly resilient during oxygen loss, which typically results in an exothermic reaction in other lithium cells. As a result, LiFePO4 cells are harder to ignite in the event of mishandling (especially during charge). The LiFePO4 battery does not decompose at high temperatures.

The energy density (energy/volume) of a new LFP battery is 14% lower than that of a new LiCoO2 battery. Also, many brands of LFPs, as well as cells within a given brand of LFP batteries, have a lower discharge rate than lead-acid or LiCoO2. Since discharge rate is a percentage of battery capacity, a higher rate can be achieved by using a larger battery (more ampere-hours) if low-current batteries must be used. Better yet, a high-current LFP cell (which will have a higher discharge rate than a lead acid or LiCoO2 battery of the same capacity) can be used.

What are the major uses of LiFePO4 batteries?

Once lithium iron phosphate batteries were ignored due to various disadvantages. But recently people are realizing it’s potential hence there is a vast use of LiFePO4 batteries all over the world.

Home energy storage

Enphase pioneered LFP home storage batteries for reasons of cost and fire safety, although the market remains split among competing chemistries. The lower energy density compared to other lithium chemistries adds mass and volume, both may be more tolerable in a static application. In 2021, there were several suppliers to the home end-user market, including SonnenBatterie and Enphase. Tesla Motors continues to use NMC batteries in its home energy storage products, but in 2021 switched to LFP for its utility-scale battery product. The most quoted home energy storage battery in the U.S. is the Enphase, which in 2021 surpassed Tesla Motors and LG.

Transportation

Higher discharge rates needed for acceleration, lower weight, and longer life make this battery type ideal for forklifts, bicycles, and electric cars. 12V LiFePO4 batteries are also gaining popularity as a second (house) battery for a caravan, motor-home, or boat.

Most recently Tesla Motors have started using LFP batteries in certain vehicles, including its Chinese-made Standard Range Models 3 and Y, and some Model 3 units in the United States beginning around August 2021. In October 2021, Tesla announced that all standard-range Models 3 and Y will begin using LFP battery chemistry.

In late 2021, Our Next Energy demonstrated a long-range test of a Model S retrofitted with an LFP battery traveling for 752 miles on a single charge.

Solar-powered lighting systems

Single “14500” (AA battery–sized) LFP cells are now used in some solar-powered landscape lighting instead of 1.2 V NiCd/NiMH.

LFP’s higher (3.2 V) working voltage lets a single cell drive an LED without circuitry to step up the voltage. Its increased tolerance to modest overcharging (compared to other Li cell types) means that LiFePO4 can be connected to photovoltaic cells without circuitry to halt the recharge cycle. The ability to drive an LED from a single LFP cell also obviates battery holders, and thus the corrosion, condensation and dirt issues associated with products using multiple removable rechargeable batteries.

By 2013, better solar-charged passive infrared security lamps emerged. As AA-sized LFP cells have a capacity of only 600 mAh (while the lamp’s bright LED may draw 60 mA), the units shine for at most 10 hours. However, if triggering is only occasional, such units may be satisfactory even charging in low sunlight, as lamp electronics ensure after-dark “idle” currents of under 1 mA.

However, there are some other uses of LiFePO4 battery also. Likewise, some electronic cigarettes use these types of batteries. Other applications include marine electrical systems and propulsion, flashlights, radio-controlled models, portable motor-driven equipment, amateur radio equipment, industrial sensor systems, and emergency lighting. 

Commercial Li-ion batteries based on NMC, NCA, and LFP chemistries were cycled with varying temperatures, depth of discharge, and discharge rate. The capacity and discharge energy retention, as well as the round-trip efficiency, were compared. The dependence on each cycling variable was analyzed qualitatively as well as by analysis of variance. Key insights from this work include:

LFP cells had the highest cycle lifetime across all conditions, but this performance gap was reduced when cells were compared according to the discharge energy throughput. The latter metric factored in the lower capacity and lower voltage of the LFP cells, illustrating the importance of identifying the appropriate metrics for each application.

In the 15 °C to 35 °C temperature range, the capacity fade rate increased with increasing temperature for LFP cells but decreased for NMC cells, indicating different dominant degradation mechanisms. These results illustrate the value of varying multiple temperatures within a normal operating range rather than looking solely at extreme temperatures. The gap in preferred conditions for LFP and NMC cells has implications for battery thermal management. A survey of the literature and the results here suggest that LFP cells are more suited for lower-temperature applications.

The uses and benefits of LiFePO4 battery

• Considered the best lithium-ion battery for industrial applications.
• Contains almost no toxic or hazardous materials and is not usually considered hazardous waste.
• Provides a safe technology that will not catch fire or explode with overcharging, nor produce flammable gases under any circumstances.
• Weighs one-third to one-quarter of the weight of an equivalent power lead-acid battery.
• Delivers more than 5000 deep discharge cycles, compared to 300 to 800 for a ten-year design-life VRLA or 1500 cycles to 50% depth of discharge for a 20-year design-life VRLA.
• Produces double the usable capacity of similarly rated lead-acid or NiCd batteries in higher discharge-rate applications.
• Has a flat voltage discharge curve, delivering little to no “voltage sag” as with lead-acid batteries.
• Has a higher discharge-rate capability (10C continuous, 20C pulse discharge).
• Accepts higher continuous charge rates – up to 3C, allowing for much shorter recharging times compared to VRLA which has 0.1C to 0.25C recommended charge rates.
• Can be left in a partially discharged state for extended periods without causing a permanent reduction of capacity.
• Has low self-discharge rates (unlike lead acid which will go flat quite quickly if left sitting for long periods).
• Does not suffer from thermal runaway. VRLA charge rates and block temperatures must be limited to avoid thermal runaway.
• Can be used in high ambient temperatures, up to 65°C, without significant performance or service-life degradation.
• Is relatively maintenance-free for the life of the battery. VRLA batteries require yearly discharge capacity testing, impedance, or conductance testing.
• Can be operated in any orientation, including inverted.
• Does not contain any toxic heavy metals such as lead or cadmium, nor any corrosive acid or alkali electrolyte.
• Is the most environmentally friendly battery chemistry available today.
• Has almost twice the energy density than NiCd.
• Weighs about one third to half of the weight of a NiCd battery of equivalent power.
• Has relatively low self-discharge; less than half that of NiCd. Left uncharged, LiFePO4 cells can retain their charge for up to ten years.
• Has a higher cell voltage of 3.6V, which means fewer cells and associated connections and electronics are needed for high voltage batteries.
• Can replace three NiCd cells, which have a cell voltage of only 1.2V.
• Does not contain any liquid electrolyte which means they are immune from leaking. NiCd contain liquid potassium hydroxide which, if leaked, is extremely corrosive and so toxic it is fatal if ingested.
• Can produce double the usable capacity of similarly rated NiCd batteries in higher discharge-rate applications.
• Has a flat voltage discharge curve, delivering maximum power available until fully discharged (no “voltage sag” as with NiCd batteries).
• Can deliver a very high discharge rate, 10C continuous, 20C pulse discharge.
• Accepts much higher charge rates – up to 3C, which means much faster recharging possibilities.
• Can be left in a deep discharged state for extended periods without causing permanent reduction of battery capacity.
• Does not suffer from “thermal runaway.”
• Can be used safely in high ambient temperatures, up to 65°C, without significant performance degradation. NiCd can only operate reliably at up to 35 to 40°C.

Check:  What Are LiFePo4 Batteries Used For?

What is the market for LiFePO4 batteries globally?

Because of its lower cost, high safety, low toxicity, long cycle life, and other factors, LFP batteries are finding a number of roles in-vehicle use, utility-scale stationary applications, and backup power. LFP batteries are cobalt-free. As of Q1 2021, LFP type battery market share reached 24.1%, with Chinese manufacturers holding a near-monopoly, and is expected to rise further to surpass NCM-type batteries in 2028.

What are the main obstacles in commercializing LiFePO4 batteries and how are modern industry is trying to overcome them?

The chief barrier to commercialization was its intrinsically low electrical conductivity. This problem was overcome by reducing the particle size, and coating the LiFePO4 particles with conductive materials such as carbon nanotubes, or both. This approach was developed by Michel Armand and his co-workers. Another approach by Yet-Ming Chiang’s group consisted of doping LFP with cations of materials such as aluminum, niobium, and zirconium. Negative electrodes (anode, on discharge) made of petroleum coke were used in early lithium-ion batteries; later types used natural or synthetic graphite.

Why have the demands for LiFePO4 batteries been rising globally in recent times?

The rising demand for LiFePO4 batteries from the automotive sector acts as the sector’s prime driver. Its demand comes in direct correspondence with the increased demand and use of battery electric vehicles (EVs).

As fossil fuel reserves empty, a corresponding price increase for gasoline and diesel can be observed. With this and the resulting environmental concerns comes a drive for consumers to switch over to battery EVs. Technological advancements, rising smart device adoption and stringent government mandates all concurrently contribute to the demand for batteries during the forecast period.

Are there any recent updates on industry growth regarding the production of LiFePO4 batteries?

The growing use of LiFePO4 batteries in renewable energy storage systems, increasing demand for consumer electronics, and resulting stringent government regulations all contribute to the battery industry’s growth.

A 2020 report published by the Department of Energy compared the costs of large-scale energy storage systems built with LFP vs NMC. It found that the cost per kWh of LFP batteries was about 6% less than NMC, and it projected that the LFP cells would last about 67% longer (more cycles). Because of differences between the cell’s characteristics, the cost of some other components of the storage system would be somewhat higher for LFP, but on balance, it still remains less costly per kWh than NMC.

ELIIY Power is a leading manufacturer of high-capacity lithium-ion batteries for electricity storage. Established in 2006 in Tokyo, ELIIY Power has its own technology development center and fully automated factories in Japan, with annual production capacities of 1.2 million battery cells in total. Utilizing a wide range of cutting-edge technologies, ELIIY Power’s lithium-ion batteries offer world-leading safety and performance. Its home page is http://eliiypower.co.jp/english/index.html.

What are the environmental impacts of lithium iron phosphate batteries?

Here’s a thoroughly modern riddle: what links the battery in your smartphone with a dead yak floating down a Tibetan river? The answer is lithium – the reactive alkali metal that powers our phones, tablets, laptops and electric cars.

In May 2016, hundreds of protestors threw dead fish onto the streets of Tagong, a town on the eastern edge of the Tibetan plateau. They had plucked them from the waters of the Liqi river, where a toxic chemical leak from the Ganzizhou Rongda Lithium mine had wreaked havoc with the local ecosystem.

There are pictures of masses of dead fish on the surface of the stream. Some eyewitnesses reported seeing cow and yak carcasses floating downstream, dead from drinking contaminated water. It was the third such incident in the space of seven years in an area that has seen a sharp rise in mining activity, including operations run by BYD, the world’s biggest supplier of lithium-ion batteries for smartphones and electric cars. After the second incident, in 2013, officials closed the mine, but when it reopened in April 2016, the fish started dying again.

But lithium may not be the most problematic ingredient of modern rechargeable batteries. It is relatively abundant, and could in theory be generated from seawater in the future, albeit through a very energy-intensive process.

Two other key ingredients, cobalt, and nickel are more in danger of creating a bottleneck in the move towards electric vehicles, and at a potentially huge environmental cost. Cobalt is found in huge quantities right across the Democratic Republic of Congo and central Africa, and hardly anywhere else. The price has quadrupled in the last two years. There’s also a political angle to be considered. When Bolivia started to exploit its lithium supplies in about 2010, it was argued that its huge mineral wealth could give the impoverished country the economic and political heft that the oil-rich nations of the Middle East. “They don’t want to pay a new OPEC,” says Lisbeth Dahllöf, of the IVL Swedish Environmental Institute, who co-authored a report last year on the environmental footprint of electric car battery production.

Why LiFePO4 battery is in cars more dangerous than fossil fuels?

Lithium-ion batteries are a crucial component of efforts to clean up the planet. The battery of a Tesla Model S has about 12 kilograms of lithium in it, while grid storage solutions that will help balance renewable energy would need much more.

Demand for lithium is increasing exponentially, and it doubled in price between 2016 and 2018. According to consultancy Cairn Energy Research Advisors, the lithium-ion industry is expected to grow from 100 gigawatt hours (GWh) of annual production in 2017, to almost 800 GWh in 2027.

William Adams, head of research at Metal Bulletin, says the current spike in demand can be traced back to 2015 when the Chinese government announced a huge push toward electric vehicles in its 13th Five-Year Plan. That has led to a massive rise in the number of projects to extract lithium, and there are “hundreds more in the pipeline,” says Adams.

But there’s a problem. As the world scrambles to replace fossil fuels with clean energy, the environmental impact of finding all the lithium required to enable that transformation could become a serious issue in its own right. “One of the biggest environmental problems caused by our endless hunger for the latest and smartest devices is a growing mineral crisis, particularly those needed to make our batteries,” says Christina Valimaki an analyst at Elsevier.